Research ArticleSynthesis Characterization Anticancer and Antioxidant Studiesof Ru(III) Complexes of Monobasic Tridentate Schiff Bases
Ikechukwu P Ejidike and Peter A Ajibade
Department of Chemistry Faculty of Science and Agriculture University of Fort Hare PB X1314 Alice 5700 South Africa
Correspondence should be addressed to Peter A Ajibade pajibadeufhacza
Received 3 March 2016 Revised 28 April 2016 Accepted 5 June 2016
Academic Editor Claudio Pettinari
Copyright copy 2016 I P Ejidike and P A AjibadeThis is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in anymedium provided the originalwork is properly cited
Mononuclear Ru(III) complexes of the type [Ru(LL)Cl2(H2O)] (LL =monobasic tridentate Schiff base anion (1Z)-N1015840-(2-(119864)-[1-(2
4-dihydroxyphenyl)ethylidene]aminoethyl)-N-phenylethanimidamide [DAE] 4-[(1E)-N-2-[(Z)-(4-hydroxy-3-methoxybenzyl-idene)amino]ethylethanimidoyl]benzene-13-diol [HME] 4-[(1E)-N-2-[(Z)-(34-dimethoxybenzylidene)amino]ethylethanim-idoyl]benzene-13-diol [MBE] and N-(2-(119864)-[1-(24-dihydroxyphenyl)ethylidene]aminoethyl)benzenecarboximidoyl chloride[DEE]) were synthesized and characterized using the microanalytical conductivity measurements electronic spectra and FTIRspectroscopy IR spectral studies confirmed that the ligands act as tridentate chelate coordinating the metal ion through theazomethine nitrogen and phenolic oxygen atom An octahedral geometry has been proposed for all Ru(III)-Schiff base complexesIn vitro anticancer studies of the synthesized complexes against renal cancer cells (TK-10) melanoma cancer cells (UACC-62) andbreast cancer cells (MCF-7) was investigated using the Sulforhodamine B assay [Ru(DAE)Cl
2(H2O)] showed the highest activity
with IC50valves of 357 plusmn 109 644 plusmn 038 and 906 plusmn 118 120583M against MCF-7 UACC-62 and TK-10 respectively order of activity
being TK-10 lt UACC-62 ltMCF-7 The antioxidant activity by DPPH and ABTS inhibition assay was also examined Scavengingability of the complexes on DPPH radical can be ranked in the following order [Ru(DEE)Cl
2(H2O)] gt [Ru(HME)Cl
2(H2O)] gt
[Ru(DAE)Cl2(H2O)] gt [Ru(MBE)Cl
2(H2O)]
1 Introduction
Coordination chemistry of transition metal Schiff base com-plexes possessing N O and S-donor atoms has receivedconsideration over the past fewdecades due to the imperativeroles these compounds have played in a variety of biochem-ical procedures like haloperoxidation [1] insulin mimicking[2 3] fixation of nitrogen [4] inhibition of cancer growthand prophylaxis against carcinogenesis [5 6] A huge varietyof carbonyl compounds (gtC=O) and amines (R-NH
2) have
been exploited in the preparation of Schiff bases [7 8]The reactivity of aldehyde compounds is generally fasterthan those of the ketones in condensation reaction therebyresulting in the formation of Schiff bases with a centre thatare less steric than the ketonersquos relatively unstable and freelypolymerizable [9] This important attribute of Schiff baseligands offers prospects for prompting substrate chirality andmetal centred electronic factor tuning and improving thesolubility and steadiness of either homogeneous or heteroge-neous catalysts [10ndash12]
Schiff bases have shown an interesting application as anactive corrosion inhibitor that is established on their capabil-ity to spontaneously form amonolayer upon the surface to beglazed [13] as it is a type of interaction existing between aninhibitor and a metal surface known as chemisorption [14]It is interesting to note that several commercial inhibitorscontain amines and aldehydes but seemingly because of thepresence of gtC=N bond this makes Schiff bases functionmore resourcefully in many ways [15] Stabilization of metalions in various oxidation states and monitoring their reactiv-ity for catalytic applications have been linked to Schiff bases[16]The nitrogen-oxygen Schiff bases geometry largely relieson the diamine structural unit nature of the ancillary ligandand the central metal ion [17] Schiff base-transition metalcomplexes have been known to be one of themost modifiableand comprehensively studied systems [18] with applicationsin clinical and analytical fields [19 20] Antioxidants derivedfrom metal Schiff base ligand combinations have receivedcurrent attention for their capability to safeguard living
Hindawi Publishing CorporationBioinorganic Chemistry and ApplicationsVolume 2016 Article ID 9672451 11 pageshttpdxdoiorg10115520169672451
2 Bioinorganic Chemistry and Applications
systems and cells from impairment caused by oxidative stressor free radicals [21]
DNA binding cleavage potentials scavenging potentialsand anticancer investigations of Schiff base-ruthenium(III)complexes have been accounted for [22] Synthesis spec-tral redox catalytic and biological action investigationof mononuclear Ru(III)-Schiff base structures are reported[23] 221015840-Bipyridine and tetradentate Schiff base ancillaryligands ofmixed-ligand Ru(II) complexes have been reportedfor their electrochemical and Na+ binding properties [24]Catalytic and growth inhibitory activities of Ru(III) mixedligand complexes of 2-hydroxy-1-naphthylideneimines havebeen reported [25]
In this study we report the synthesis characteriza-tion free radical scavenging and anticancer studies offour mononuclear ruthenium(III) complexes of Schiff basesderived from 2101584041015840-dihydroxyacetophenone and ethylenedi-amine as the bridging ligand with RCHO moiety alongsidetheir radicals scavenging action on 11-diphenyl-2-picrylhy-drazyl (DPPH) and 221015840-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and antiproliferative potentials TheSchiff base ligands containing N
2O type tridentate parti-
tions were utilized for the synthesis of the mononuclearruthenium(III)-Schiff base complexes (Scheme 1)
2 Experimental
21 Chemicals and Instrumentations All reagents used wereof analytical grade and used as purchased commerciallyEthylenediamine N1198731015840-dimethylformamide (DMF) andascorbic acid (Vit C) were received from Merck 2101584041015840-dihydroxyacetophenone and RuCl
3sdot3H2O were obtained
from Aldrich 11-Diphenyl-2-picrylhydrazyl (DPPH) 221015840-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS)butylated hydroxytoluene (BHT) and rutin hydrate werereceived from Sigma Chemical Co (St Louis MO USA)Elemental analysis was carried out using Perkin-Elmerelemental analyzer IR spectra were recorded on an FT-IRspectrometer Perkin-Elmer System (Spectrum 2000) viaKBr diskmethod was used for the IR spectra analysis Freshlyprepared DMF solutions of about 10minus3M containing Ru(III)complexes gave the molar conductance at room temperaturewith Crison EC-Meter Basic 30+ conductivity cell Electronicabsorption spectra ranging from 200 to 900 nm wererecorded on a Perkin-Elmer Lambda-25 spectrophotometerStuartmelting point (SMP 11) was used for themelting pointsFour N
2O type tridentate ligands (1Z)-1198731015840-(2-(119864)-[1-(24-
22 Preparation of the Tridentate Schiff Bases (DAEHME MBE and DEE) Ethylenediamine (0015mol)
dissolved in 20mL of alcohol was slowly added to 2101584041015840-dihydroxyacetophenone (0015mol) dissolved in same alco-hol (30mL) and allowed to stir for 60 minutes at room tem-perature and then followed by drop-wise addition ofappropriate aldehyde (RCHO 15mmol) dissolved in 30mLalcohol for 20minutes time interval at room temperature andfurther stirred for 120 minutesThemixture was left standingwith continuous stirring for approximately 36 hours at roomtemperature after which the desired tridentate compoundswere filtered and washed with ethanol to give crystallinesolid The crude product was recrystallized from warmethanol The products were dried in the vacuum at 50∘Covernight to give analytically pure products in good yields(642 to 738)
23 Synthesis of Ru(III)-Tridentate Schiff Base ComplexesRu(III) complexes were prepared by adding (05mmol)ethanol solution of ruthenium(III) chloride to a warmethanolic solution (05mmol) of [DAE][HME][MBE][DEE] respectively The colour of the solutions changedimmediately magnetically stirred and kept under reflux for6 hours The precipitated solids were filtered by suction fromthe reaction medium washed with ethanol and then withdiethyl ether and dried over anhydrous calcium chlorideTheyields were about 557ndash619The synthesis of the complexesis explained in Scheme 1
231 Synthesis of [OHC6H3OHC(CH3)N(C2H4)NC(CH3)NHC6H5RuCl2(H2O)]
[Ru(DAE)Cl2(H2O)]sdotH2O Dark-green solid Yield 1566mg(604) F Wt 51838 g Anal Calcd for C
18H24N3O4RuCl2
() C 4171 H 467 N 811 Found () C 4143 H 454 N829 IR (KBr) ]maxcm
24 In Vitro Antiproliferative Activity The potentials of theRu(III)-tridentate Schiff base complexes to interfere with thegrowth of TK-10 renal cell line UACC-62melanoma cell lineand MCF-7 breast cell lines were determined by SRB assayas previously described [22] 3ndash19 passages of MCF-7 TK-10andUACC-62 cell lineswith plating densities of 7ndash10 000 cellsper well were precultured into 96-well microtitre plates for24 h at 37∘Cwith 95air 5CO
2 and 100 relative humidity
in RPMI medium supplemented with 5 fetal bovine serum
(FBS) 50 120583gmLminus1 (gentamicin) and 2mML-glutamine [27]The compounds were dissolved in DMSO and treated withthe cells after 24 h and diluted in RPMI medium giving riseto 5 concentrations comprising 001 01 0 10 and 100 120583M
Wells containing culture medium were used as controlwhile the wells containing complete culture medium with nocells were used as the blanks Parthenolide was used as thestandard drug in this study The plates were then incubatedfor 48 h after the addition of the compounds Viable cells werefixed to the bottom of each well with cold 50 trichloroaceticacid washed dried and dyed by SRB The unbounded dyewas separated while the protein-bound dye was extractedwith 10mM Tris base and multiwell spectrophotometer atthe wavelength 540 nm was used for its optical densitydetermination IC
50values were determined by plotting the
percentage viability against concentration of compounds ona logarithmic graph to obtain 50 of cell growth inhibitionrelative to the control
25 Antioxidant Assay
251 Scavenging Activity of 11-Diphenyl-2-picrylhydrazyl(DPPH) Radical The antioxidant activity of the preparedRu(III) complexes was studied using spectrophotometer by11-diphenyl-2-picrylhydrazyl (DPPH) method This com-pound is known as a stable readily accessible free radicalwith solubility in methanol giving a purple solution and
4 Bioinorganic Chemistry and Applications
when reacted with antioxidant species changes to an equiv-alent light yellow colour The radical scavenging potentialsof the complexes with DPPH radical were evaluated asdescribed [22] 1mL solution of the compounds in DMFwithconcentrations ranging from 100 to 500120583gmL was mixedthoroughly with equivalent amount of 04mM DPPH inmethanol themixtures were then allowed to react in the darkfor half an hour Measurement of the mixture absorbancewas achieved spectrophotometrically at 517 nm Vitamin Cand rutin were used as the standard drugs All test analysiswas carried out in triplicate The ability of the rutheniumcompounds to scavenge DPPH radical was calculated via thefollowing equation
DPPH radical scavenging activity ()
=Absorbance of control minus Absorbance of sample
Absorbance of control
times 100
(1)
252 ABTS 221015840-Azino-bis(3-ethylbenzothiazoline-6-sulfonicacid) Radical Scavenging Assay ABTS scavenging abilityof the Ru(III)-tridentate Schiff base complexes adopted adescribed method [28] 7mM ABTS solution and 24mMpotassium persulfate solution in equal amounts (1 1) wereused for working solution preparation and allowed to reactin the dark for 12 h at room temperature An absorbanceof 0706 plusmn 0001 units at 734 nm required for the analysiswas obtained by diluting 1mL ABTS+ solution Test samples(1mL) were mixed with 1mL of the ABTS+ solution andabsorbance was read spectrophotometrically at 734 nm Thetest samplesrsquo ABTS scavenging capacity alongside standarddrugs was evaluated Triplicate analysis was carried out Thepercentage inhibition ofABTS radical scavenging activitywasobtained following a previous report [28]
3 Results and Discussion
31 Synthesis and Characterization The obtained com-pounds were of coloured powders stable in atmospherewith a general formula [Ru(LL)Cl
2(H2O)] (LL = monobasic
tridentate Schiff base anion DAE HME MBE and DEE)They were prepared by treating [RuCl
3sdot3H2O] with the
corresponding Schiff base in an equal mole ratio in alcoholas depicted in the Scheme 1 All the complexes are dark-green and sparingly soluble in general organic solvents butsoluble in polar aprotic solvent such as DMF and DMSOthe melting point analysis showed that the Ru(III) complexeswere decomposing before melting The physicoanalyticaldata collected for the compounds are in agreement withthe structural formulae proposed thus confirming the sug-gested mononuclear composition for the Ru(III) complexes(Scheme 1)
32 Molar Conductivity Measurements The molar conduc-tance of the synthesized Ru(III) complexes was measuredin DMF at 10minus3M solution The values were found to be in
the range of 301ndash388 120583Scmminus1 suggesting the nonelectrolyticnature of the complexes in solution [22 29]
33 Infrared Spectra Valuable evidence concerning the envi-ronment of the functional group attached to the rutheniumatom has been obtained from the FTIR spectra The IRspectra of the ligands when compared with those of thenewly synthesized complexes confirm the coordination ofN2O type tridentate ligands to the ruthenium ion The
classification was achieved by comparing the spectra of theligandswith those originating from the coordination betweenruthenium(III) metal ion and the active sites The Schiffbases showed the broad bands in the 3462ndash3477 cmminus1 rangeattributable to the ](OH) cmminus1 vibration Ligand infraredspectra showed that a band at 1605ndash1619 cmminus1 is attributed to](C=N) stretching of the azomethine group based on earlierreports [30] This ](C=N) shift to 1617ndash1639 cmminus1 in all thecomplexes by about 5ndash23 cmminus1 signifies the participation ofazomethine nitrogen in the coordination sphere with theruthenium(III) ion for all the complexes [21 31] A mediumband that corresponds to phenolic oxygen atom ](C-O) isobserved at 1167 and 1245 cmminus1 for the free ligands
The higher shifting of ](C-O) stretching vibrations asobserved in the ruthenium(III) complexes spectra suggeststhat the phenolic OH group of Schiff base DAE HMEMBE and DEE is involved in coordination with rutheniumion after deprotonation [32 33] Seemingly the DAE HMEMBE and DEE ligands act as a tridentate chelating com-pound coordinating to the metal ion via the two nitrogenatoms of the azomethine group as well as O atom of phenolicgroup [21 25] This is further supported by the displacementof ](O-H) in the range 3462ndash3477 cmminus1 in all the complexesThe presence of coordinated water gave a broad band thatappeared in the regions 3416ndash3436 and 813ndash851 cmminus1 this canbe due to ](O-H) stretching and ](O-H) rocking vibrationsrespectively which further confirms the presence of nonli-gand assignable to the rocking mode of water [28 34] Newweak nonligand bands that are not found in the DAE HMEMBE and DEE ligands appeared in the ranges 475ndash548 cmminus1and 436ndash475 cmminus1 in the complexes spectra attributed to](Ru-N) and ](Ru-O) vibrations respectively [35 36] A bandranging from 311ndash346 cmminus1 appeared in the spectra of theRu(III)-Schiff base complexes indicating the presence of twochloride ions in trans position around ruthenium centre [37ndash40]
34 Electronic Absorption Spectra Studies The UV-Vis spec-tra of the Ru(III)-Schiff base complexes in DMF solutionswere recorded at room temperature ranging from 200 to900 nm The nature of DAE HME MBE and DEE ligandsfield around the ruthenium ion was obtained from theelectronic spectra The free ligands showed absorption bandswithin the range of 277ndash393 nm attributable to 120587lowast larr 120587 and120587lowastlarr 119899 transitions relating the benzene ring (Figure 1) The
shifting of these bands in the complexes spectra followed theparticipation of the imine group nitrogen and phenolic groupoxygen in bonding [22 25] Ground state of ruthenium(III) is2T2g where initial excited doublet levels in order of increasing
Bioinorganic Chemistry and Applications 5
0
02
04
06
08
1
12
14
16
260 320 380 440 500 560 620 680
Abso
rban
ce (a
u)
Wavelength (nm)
(a)
0
02
04
06
08
1
12
14
16
18
260 320 380 440 500 560 620 680
Abso
rban
ce (a
u)
Wavelength (nm)
(b)
0
02
04
06
08
1
12
14
260 320 380 440 500 560 620 680
Abso
rban
ce (a
u)
Wavelength (nm)
(c)
0
01
02
03
04
260 320 380 440 500 560 620 680
Abso
rban
ce (a
u)
Wavelength (nm)
(d)
Figure 1 Electronic absorption spectra of the Ru(III) complexes (a) [Ru(DAE)Cl2(H2O)] (b) [Ru(HME)Cl
2(H2O)] (c)
[Ru(MBE)Cl2(H2O)] (d) [Ru(DEE)Cl
2(H2O)]
energy are 2A2g and 2T
1g arising from t42ge1
g configuration[41]
Ru3+ ion with a d5 electronic configuration possesseshigh oxidizing properties and large crystal field parameterAlso charge transfer bands of the type L
120587y rarr T2g were
noticeable within low energy region obscuring weaker bandsthat is due to d-d transitions [22 25] The extinction coef-ficient bands around 613ndash632 nm regions are found to below when compared to the charge transfer bands Thesebands have been assigned to 2T
2g rarr2A2g transition and
are in agreement with the assignment made for similaroctahedral ruthenium(III) complexes [42 43] Absorptionbands within the 452ndash525 nm regions were assigned to thecharge transfer transitions [22 44] Overall the absorptionspectra of the Ru(III)-Schiff base complexes are typical ofoctahedral environment about the ruthenium(III) ions [22]
35 Antiproliferative Activity Investigation into the struc-ture-activity relationship of the isolated Ru(III)-N
2O Schiff
base complexes with respect to different functional groups
on the ligands used for ruthenium ion complex formationhas been conducted via antiproliferative studies Three of theRu(III)-Schiff base compounds alongside parthenolide weresubjected to cell lines tests at different sample concentrationsranging from 001 to 100120583M towards renal cancer cell (TK-10) melanoma cancer cell (UACC-62) and breast cancercell (MCF-7) The cancer cell lines were incubated for 48 hfollowed by the addition of the compounds of variousconcentrations via Sulforhodamine B (SRB) assay [22]
The ruthenium(III) compounds and standard drug(parthenolide) IC
50values are presented in Table 1 and
revealed that the test samples showed significant inhibitionagainst the tested cell lines Figures 2ndash4 represent the cellviability percentages of ruthenium(III)-Schiff base complexesand parthenolide drug against TK-10 UACC-62 and MCF-7 cell lines at different concentrations of ruthenium(III)compounds or parthenolide A high level of antiprolifera-tive potentials against the studied cell lines was exhibitedby parthenolide in accordance with earlier reports [45]The obtained results revealed that treatment of cell lines with
6 Bioinorganic Chemistry and Applications
Table 1 In vitro antiproliferative studies of Ru(III)-Schiff base complexes against TK-10 UACC-62 and MCF-7 cell lines
Compounds Molecular formula Anticancer activity IC50(120583M) 48 h
TK-10 UACC-62 MCF-7[Ru(DAE)Cl
2(H2O)] C
18H24N3O4RuCl2
906 plusmn 118 644 plusmn 038 357 plusmn 109
[Ru(HME)Cl2(H2O)] C
18H23N2O6RuCl2
4109 plusmn 444 631 plusmn 147 488 plusmn 128
[Ru(DEE)Cl2(H2O)] C
17H20N2O4RuCl3
1310 plusmn 281 514 plusmn 109 343 plusmn 148
Parthenolidelowast C15H20O3
050 plusmn 143 089 plusmn 218 044 plusmn 202lowastStandard cytotoxin drug cell lines were treated with different concentrations of the compounds to achieve 50 inhibition of the culture growth when culturedfor 48 h Value represents mean plusmn SD of three independent experimentations
Figure 2 In vitro antiproliferative activity of Ru(III) complexes andparthenolide against human breast cancer cell line (MCF-7)
different concentrations of Ru(III)-Schiff base complexes effi-ciently affected cell viability towardsMCF-7 cells as displayedin Figures 2ndash4 and Table 1 The Ru(III) compounds exhibitedlow to strong in vitro antiproliferative activities againstthe selected cell lines as compared to the standard drug(parthenolide) [Ru(DAE)Cl
2(H2O)] [Ru(HME)Cl
2(H2O)]
and [Ru(DEE)Cl2(H2O)] induced more efficient cell death
with IC50values of 357plusmn109 488plusmn128 and 343plusmn148 120583M
respectively towards human breast cancer cell (MCF-7) cellsthan other investigated cell lines compared with IC
50values
of 044 plusmn 202 120583M MCF-7 for the standard cytotoxin drugparthenolide
The order of activity of the complexes againsthuman melanoma cancer cell (UACC-62) is asfollows [Ru(DEE)Cl
2(H2O)] gt [Ru(HME)Cl
2(H2O)] gt
[Ru(DAE)Cl2(H2O)] With respect to previous report by
Shier [46] compounds exhibiting IC50activity ranging from
10 to 25 120583M are referred to as weak anticancer drugs whilethose with IC
50action between 5 and 10 120583M are moderate
and the compounds possessing activity less than (lt) 500120583M
Figure 3 In vitro antiproliferative activity of Ru(III) complexes andparthenolide against human melanoma cancer cell (UACC-62)
are considered as strong agents Thus the Ru(III) complexesexhibited a weak to strong activity against the investigatedcancer cell lines with the following order of activity MCF-7 gt UACC-62 gt TK-10 However [Ru(DAE)Cl
2(H2O)]
showed the highest antiproliferative activity with IC50
valves of 357 plusmn 109 644 plusmn 038 and 906 plusmn 118 120583M forMCF-7 UACC-62 and TK-10 respectively The biochemicalactivity could be due to the methoxy alkyl chloride groupsubstituents and bridge spacer ethylenediamine whichcould have played a vital role in antiproliferative potentialsof the Ru(III)-N
2O Schiff base complexes In vitro anticancer
activity of the synthesized Ru(III) complexes in this studywas compared with Ru complexes reported by other authorsand found that [Ru(DAE)Cl
2(H2O)] [Ru(HME)Cl
2(H2O)]
and [Ru(DEE)Cl2(H2O)] complexes exhibited higher
antitumor activities [RuCl(CO)(PPh3)L] reported by Raja et
al [47] against human cervical carcinoma cell line (HeLa)after exposure for 48 h gave an IC
50value in the range of
316 120583M and [RuCl2(AsPh
3)L] with an IC
50value of 378120583M
[48] Raju et al [43] reported ruthenium(III) Schiff basecomplexes of the type [RuX
2(PPh3)2(L)] (where X = Cl or
Bioinorganic Chemistry and Applications 7
020
4060
80
100
00101
1
10
100
ce
ll vi
abili
ty
[Parthenolide][Ru(DAE)Cl2(H2O)]
[Ru(HME)Cl2(H2O)][Ru(DEE)Cl2(H2O)]
Concentration (120583M)
Figure 4 In vitro antiproliferative activity of Ru(III) complexes andparthenolide against human renal cancer cell (TK-10)
Br L = monobasic bidentate ligand) complex to have IC50
value in the range of 452120583M
36 Antioxidant Capacity Different antioxidant techniquesand modifications have been put forward to evaluate antiox-idants reactivity and functionality in foods and biologicalsystems as a means of checkmating variety of patholog-ical activities such as cellular injury and aging processthese damaging occurrences are caused by free radicalsHence two free radicals were used for in vitro antioxi-dants activities of the test samples in this study namely11-diphenyl-2-picrylhydrazyl (DPPH) and 221015840-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS)
361 DPPHRadical Scavenging Assay The activity of antiox-idants on DPPH radical is believed to be centred on theirability to donate hydrogen [22] DPPH has been a stablefree radical with the ability to accept hydrogen radical or anelectron and then become a stable molecule [49]
The mode of rummaging the DPPH radical hasextensively been used to appraise antioxidant activities oftest samples in a moderately short period of time comparedto other procedures [49] The reduction in the DPPH radicalcapability is calculated by the decrease in its absorbanceat 517 nm prompted by antioxidants [50] The reduction ofDPPH radical intensity in this study is due to the interactionof Ru(III) complexes with radical and as such scavengingthe radicals by hydrogen donation (Scheme 2) The DPPHactivities by the Ru(III)-N
2O Schiff base complexes exhibit
strong electron donating power when compared to thestandards ascorbic acid and rutin as displayed in Figure 5The calculated IC
Figure 5 DPPH scavenging potential of Ru(III)-Schiff base com-plexes
coefficient) values of Ru(III) compounds are listed in Table 2Compounds [Ru(DAE)Cl
2(H2O)] [Ru(HME)Cl
2(H2O)]
[Ru(MBE)Cl2(H2O)] and [Ru(DEE)Cl
2(H2O)] with an IC
50
value of 160plusmn068 154plusmn044 163plusmn105 and 151plusmn050 120583Mrespectively exhibited higher activity against DPPH thanthe commercially available Vit C and rutin (standard)however [Ru(DEE)Cl
2(H2O)] showed the highest activity of
all investigated ruthenium(III) samples with an IC50value of
151 plusmn 050 120583MScavenging ability of the test samples on the
DPPH radical can be ranked in the following order[Ru(DEE)Cl
2(H2O)] gt [Ru(HME)Cl
2(H2O)] gt
[Ru(DAE)Cl2(H2O)] gt [Ru(MBE)Cl
2(H2O)] gt [Vit C]
gt [rutin]The scavenging effect of the DAE HME MBE andDEE ligands is lower as compared to their correspondingRu(III) complexes owing to the coordination of the organicmolecules to the Ru3+ ion It is further supported by theobserved discolouration from purple DPPH radical solutionto yellow solution showing scavenging of the DPPH radicalsby hydrogen donation (Scheme 2) Hence these complexescould be effective therapeutic agentrsquos preparation for thetreatment of chronic conditions such as cardiovascularneurodegenerative and arteriosclerosis diseases [21]
362 221015840-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)Radical Scavenging Activity To further confirm the synthe-sized Ru(III)-N
2O Schiff base complexes antiradical poten-
tial we examined the ABTS assay in this study A well-knownprotonated radical like 221015840-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) possesses characteristic absorbancemaxima at 734 nm and decreases with the scavenging of theproton radicals [51]The assaymeasures radical scavenging byelectron donation The outcome of Ru(III)-N
2O Schiff base
complexes alongside the standard drugs on ABTS radical ispresented in Table 2 At 734 nm the absorbance of activeABTSlowast solution noticeably declined upon the addition ofdifferent concentrations of ruthenium(III) samples the sametrend was also observed for the standard drugs butylated
8 Bioinorganic Chemistry and Applications
N N NH+
Cl
Cl
N N
O
HO
HRuCl
Cl
N N
OHRu
+
DPPH radical Reduced DPPH
Antioxidant
OH2 OH2
O2N
O2N
O2N
O2N
NO2
H3C H3C
OCH3 OCH3
OCH3OCH3
NO2
517 nm
O∙
N∙
Scheme 2 Conversion of DPPHlowast (purple) to its corresponding hydrazine form (yellow) by the addition of Ru(III) compounds to DPPHlowastdue to proton transfer
Table 2 Radical scavenging abilities (IC50plusmn SD 120583M) of Ru(III)-Schiff base complexes and standard drugs
Rutinlowast 252 plusmn 160 0798 283 plusmn 184 0983Vit Clowast 192 plusmn 107 0978 mdash mdashBHTlowast mdash mdash 164 plusmn 154 0919119899 = 3119883plusmn SEM IC50 growth inhibitory concentration when the inhibition of the tested compounds was 50 the tested compound concentration was IC501198772 correlation coefficient lowastStandards
hydroxytoluene (BHT) and rutin hydrate with the percentageinhibition displayed in Figure 6
The efficacy of the tested samples in quenching ATBSlowastradicals in the system was observed at 100120583gmL the lowestconcentration and Ru(III) complexes exhibited higher ABTS inhibition than the standards [Ru(DEE)Cl
2(H2O)] com-
plex exhibited the highest ABTS scavenging activity amongstthe studied ruthenium(III) complexes with an IC
50value
of 324 plusmn 093 120583M and 0855 1198772 (correlation coefficient) aslisted in Table 2 while complexes of [Ru(DAE)Cl
2(H2O)]
[Ru(HME)Cl2(H2O)] and [Ru(MBE)Cl
2(H2O)] had an IC
50
value of 330 plusmn 089 427 plusmn 117 and 330 plusmn 148 120583Mrespectively
The ABTS scavenging activity pattern of the complexesis ranked in the following order [Ru(HME)Cl
2(H2O)]
lt [Ru(MBE)Cl2(H2O)] = [Ru(DAE)Cl
2(H2O)] lt
[Ru(DEE)Cl2(H2O)] With this result the antiradical
studies showed that the synthesised Ru(III)-N2O Schiff base
complexes may be useful in developing therapeutic agentfor averting cell oxidative damage and as radicals chainterminator This is because various free radicals generated in
the system often lead to cancer cellular injury aging processand cardiovascular diseases [21]
4 Conclusion
In this study we present the synthesis of Ru(III) Schiff basecomplexes formulated as [Ru(LL)Cl
2(H2O)] (LL = DAE
HME MBE and DEE) The complexes were character-ized using the microanalytical conductance electronic andvibrational spectral analysis FTIR spectral data showed thatthe ligand acts as tridentate chelating ligand coordinatingthrough azomethine nitrogen and phenol oxygen atomThe microanalyses were in conformity with the proposedstructures Conductance measurements showed the com-plexes to be nonelectrolytes in DMF Octahedral structureswere assigned to these complexes based on the elementaland spectral information In vitro antiproliferative studiesof the Ru(III) complexes gave a weak to strong inhibitionagainst the studied cancer cell lines with the followingactivity order MCF-7 gt UACC-62 gt TK-10 Significantly
Figure 6 ABTS rummaging activity of Ru(III)-Schiff base com-plexes
further investigation on the compounds free radical scav-enging properties revealed that Ru(III)-Schiff base complexespossessed considerable antioxidant activities The outcomefrom DPPH and ABTS inhibition studies revealed that thecompounds are proficient in donating electron or hydrogenatom and subsequently terminate the chain reactions ina dose-dependent pattern Scavenging ability of the testsamples on the DPPH radicals can be ranked in the fol-lowing order [Ru(DEE)Cl
2(H2O)]gt [Ru(HME)Cl
2(H2O)]gt
[Ru(DAE)Cl2(H2O)] gt [Ru(MBE)Cl
2(H2O)] Thus Ru(III)-
N2O Schiff base complexes showed stronger inhibition of
DPPH at various concentrations
Competing Interests
No conflict of interests regarding the publication of this paperis declared by the authors
Acknowledgments
The authors acknowledge GovanMbeki Research and Devel-opment Centre (GMRDC) University of Fort Hare forfinancial support and IPE acknowledges National ResearchFoundation and Sasol Inzalo Foundation for the award ofPhD scholarship
References
[1] A Butler and J V Walker ldquoMarine haloperoxidasesrdquo ChemicalReviews vol 93 no 5 pp 1937ndash1944 1993
[2] Y Shechter I Goldwaser M Mironchik M Fridkin and DGefel ldquoHistoric perspective and recent developments on theinsulin-like actions of vanadium toward developing vanadium-based drugs for diabetesrdquo Coordination Chemistry Reviews vol237 no 1-2 pp 3ndash11 2003
[3] A M B Bastos J G da Silva P I S Maia et al ldquoOxo-vanadium(IV) and (V) complexes of acetylpyridine-derivedsemicarbazones exhibit insulin-like activityrdquoPolyhedron vol 27no 6 pp 1787ndash1794 2008
[4] R R Eady ldquoCurrent status of structure function relationshipsof vanadiumnitrogenaserdquoCoordination Chemistry Reviews vol237 no 1-2 pp 23ndash30 2003
[5] K H Thompson J H McNeill and C Orvig ldquoVanadiumcompounds as insulin mimicsrdquo Chemical Reviews vol 99 no9 pp 2561ndash2572 1999
[6] G Grivani G Bruno H A Rudbari A D Khalaji and PPourteimouri ldquoSynthesis characterization and crystal structuredetermination of a new oxovanadium(IV) Schiff base complexthe catalytic activity in the epoxidation of cyclooctenerdquo Inor-ganic Chemistry Communications vol 18 pp 15ndash20 2012
[7] J W Pyrz A L Roe L J Stern and L Que Jr ldquoModel studiesof iron-tyrosinate proteinsrdquo Journal of the American ChemicalSociety vol 107 no 3 pp 614ndash620 1985
[8] M Tumer B Erdogan H Koksal S Serin and M Y NutkuldquoPreparation spectroscopic characterisation and thermal anal-yses studies of theCu(II) Pd(II) andVO(IV) complexes of someSchiff base ligandsrdquo Synthesis and Reactivity in Inorganic andMetal-Organic Chemistry vol 28 no 4 pp 529ndash542 1998
[9] J Hine and C Y Yeh ldquoEquilibrium in formation and conforma-tional isomerization of imines derived from isobutyraldehydeand saturated aliphatic primary aminesrdquo Journal of the Ameri-can Chemical Society vol 89 no 11 pp 2669ndash2676 1967
[10] T Opstal and F Verpoort ldquoSynthesis of highly active rutheniumindenylidene complexes for atom-transfer radical polymer-ization and ring-opening-metathesis polymerizationrdquo Ange-wandte ChemiemdashInternational Edition vol 42 no 25 pp 2876ndash2879 2003
[11] B De Clercq F Lefebvre and F Verpoort ldquoImmobilization ofmultifunctional Schiff base containing ruthenium complexeson MCM-41rdquo Applied Catalysis A General vol 247 no 2 pp345ndash364 2003
[12] A Golcu M Tumer H Demirelli and R A WheatleyldquoCd(II) andCu(II) complexes of polydentate Schiff base ligandssynthesis characterization properties and biological activityrdquoInorganica Chimica Acta vol 358 no 6 pp 1785ndash1797 2005
[13] NMishra K Poonia and D Kumar ldquoAn overview of biologicalaspects of Schiff base metal complexesrdquo International Journal ofAdvancements in ResearchampTechnology vol 2 no 8 pp 52ndash662013
[14] L-A H Allen L S Schlesinger and B Kang ldquoVirulent strainsof Helicobacter pylori demonstrate delayed phagocytosis andstimulate homotypic phagosome fusion in macrophagesrdquo TheJournal of Experimental Medicine vol 191 no 1 pp 115ndash1272000
[15] L A Calderon R C L Teles J R S A Leite C Bloch JrS Astolfi-Filho and S M Freitas ldquoSerine protease inhibitorsfromAmazon Leguminosae seeds purification and preliminarycharacterization of two chymotrypsin inhibitors from Ingaumbraticardquo Protein and Peptide Letters vol 8 no 6 pp 485ndash493 2001
[16] P G Cozzi ldquoMetal-Salen Schiff base complexes in catalysispractical aspectsrdquo Chemical Society Reviews vol 33 no 7 pp410ndash421 2004
[17] T Katsuki ldquoUnique asymmetric catalysis of cis-120573 metal com-plexes of salen and its related Schiff-base ligandsrdquo ChemicalSociety Reviews vol 33 no 7 pp 437ndash444 2004
[18] I M I Fakhr N A Hamdy M A Radwan and Y M AhmedldquoSynthesis of new bioactive benzothiophene derivativesrdquo Egyp-tian Journal of Chemistry vol 47 pp 201ndash215 2004
[19] R A A Ammar and A-N M A Alaghaz ldquoSynthesisspectroscopic characterization and potentiometric studies of
10 Bioinorganic Chemistry and Applications
a tetradentate [N2O2] schiff base NN1015840-bis(2-hydroxyben-
zylidene)-11-diaminoethane and its Co(II)Ni(II)Cu(II) andZn(II) complexesrdquo International Journal of ElectrochemicalScience vol 8 no 6 pp 8686ndash8699 2013
[20] A S Gaballa M S Asker A S Barakat and S M TelebldquoSynthesis characterization and biological activity of someplatinum(II) complexes with Schiff bases derived from salicy-laldehyde 2-furaldehyde and phenylenediaminerdquo Spectrochim-ica Acta Part A Molecular and Biomolecular Spectroscopy vol67 no 1 pp 114ndash121 2007
[21] I P Ejidike and P A Ajibade ldquoTransition metal complexesof symmetrical and asymmetrical Schiff bases as antibacterialantifungal antioxidant and anticancer agents progress andprospectsrdquo Reviews in Inorganic Chemistry vol 35 no 4 pp191ndash224 2015
[22] I P Ejidike and P A Ajibade ldquoSynthesis characterization andin vitro antioxidant and anticancer studies of ruthenium(III)complexes of symmetric and asymmetric tetradentate Schiffbasesrdquo Journal of Coordination Chemistry vol 68 no 14 pp2552ndash2564 2015
[23] N P Priya S Arunachalam A Manimaran D Muthupriyaand C Jayabalakrishnan ldquoMononuclear Ru(III) Schiff basecomplexes synthesis spectral redox catalytic and biologicalactivity studiesrdquo Spectrochimica Acta Part A Molecular andBiomolecular Spectroscopy vol 72 no 3 pp 670ndash676 2009
[24] L Mishra R Prajapati and K K Pandey ldquoMixed-ligand Ru(II)complexes with 221015840-bipyridine and tetradentate Schiff basesauxiliary ligands Synthesis physico-chemical study DFT anal-ysis electrochemical and Na+ binding propertiesrdquo Spectrochim-ica ActamdashPart A Molecular and Biomolecular Spectroscopy vol70 no 1 pp 79ndash85 2008
[25] G Venkatachalam and R Ramesh ldquoCatalytic and biologicalactivities of Ru(III) mixed ligand complexes containing NOdonor of 2-hydroxy-1-naphthylideneiminesrdquo SpectrochimicaActa Part A Molecular and Biomolecular Spectroscopy vol 61no 9 pp 2081ndash2087 2005
[26] I P Ejidike and P A Ajibade ldquoSynthesis and in vitro anti-cancer antibacterial and antioxidant studies of unsymmet-rical Schiff base derivatives of 4-[(1E)-N-(2-aminoethyl)eth-animidoyl]benzene-13-diolrdquo Research on Chemical Intermedi-ates vol 42 no 8 pp 6543ndash6555 2016
[27] K I Ansari I Hussain H K Das and S S Mandal ldquoOver-expression of human histone methylase MLL1 upon exposureto a food contaminant mycotoxin deoxynivalenolrdquo The FEBSJournal vol 276 no 12 pp 3299ndash3307 2009
[28] I P Ejidike and P A Ajibade ldquoSynthesis characterization andbiological studies of metal(II) complexes of (3E)-3-[(2-(119864)-[1-(24-Dihydroxyphenyl) ethylidene]aminoethyl)imino]-1-phenylbutan-1-one schiff baserdquo Molecules vol 20 no 6 pp9788ndash9802 2015
[29] C A Bolos A T Chaviara D Mourelatos et al ldquoSynthesischaracterization toxicity cytogenetic and in vivo antitumorstudies of 11-dithiolate Cu(II) complexes with di- tri- tetra-amines and 13-thiazoles Structure-activity correlationrdquo Bioor-ganic amp Medicinal Chemistry vol 17 no 8 pp 3142ndash3151 2009
[30] P K Das N Panda and N K Behera ldquoSynthesis character-ization and antimicrobial activities of Schiff base complexesderived from isoniazid and diacetylmonoximerdquo InternationalJournal of Innovative Science Engineering amp Technology vol 3no 1 pp 42ndash54 2016
[31] L Mitu M Ilis N Raman M Imran and S RavichandranldquoTransition metal complexes of isonicotinoylndashhydrazone-4-diphenylaminobenzaldehyde synthesis characterization andantimicrobial studiesrdquo E-Journal of Chemistry vol 9 no 1 pp365ndash372 2012
[32] S A Ali A A Soliman M M Aboaly and R M RamadanldquoChromium molybdenum and ruthenium complexes of 2-hydroxyacetophenone schiff basesrdquo Journal of CoordinationChemistry vol 55 no 10 pp 1161ndash1170 2002
[33] K N Kumar R Ramesh and Y Liu ldquoSynthesis structureand catalytic activity of cycloruthenated carbonyl complexescontaining arylazo phenolate ligandsrdquo Journal of MolecularCatalysis A Chemical vol 265 no 1-2 pp 218ndash226 2007
[34] I P Ejidike and P A Ajibade ldquoSynthesis characterizationantioxidant and antibacterial studies of some metal(II)complexes of tetradentate schiff base ligand (4E)-4-[(2-(119864)-[1-(24-dihydroxyphenyl)ethylidene]aminoethyl)imino]pentan-2-onerdquo Bioinorganic Chemistry and Applications vol 2015Article ID 890734 9 pages 2015
[35] J S Casas A Castineiras F Condori et al ldquoDiorganotin(IV)-promoted deamination of amino acids by pyridoxal SnR2
2+
complexes of pyridoxal 51015840-phosphate and of the Schiff basepyridoxal-pyridoxamine (PLPM) and antibacterial activities ofPLPM and [SnR
2(PLPM-2H)] (R=Me Et Bu Ph)rdquo Polyhedron
vol 22 no 1 pp 53ndash65 2003[36] P J K Inba B Annaraj S Thalamuthu and M A Nee-
lakantan ldquoCu(II) Ni(II) and Zn(II) complexes of salan-typeligand containing ester groups synthesis characterizationelectrochemical properties and in vitro biological activitiesrdquoBioinorganic Chemistry and Applications vol 2013 Article ID439848 11 pages 2013
[37] K Shanker R Rohini V Ravinder P M Reddy and Y-P HoldquoRu(II) complexes of N
4and N
2O2macrocyclic Schiff base lig-
ands their antibacterial and antifungal studiesrdquo SpectrochimicaActa Part A Molecular and Biomolecular Spectroscopy vol 73no 1 pp 205ndash211 2009
[38] M Alias H Kassum and C Shakir ldquoSynthesis physicalcharacterization and biological evaluation of Schiff base M(II)complexesrdquo Journal of the Association of Arab Universities forBasic and Applied Sciences vol 15 no 1 pp 28ndash34 2014
[39] K Shivakumar Shashidhar P V Reddy and M B HallildquoSynthesis spectral characterization and biological activity ofbenzofuran Schiff bases with Co(II) Ni(II) Cu(II) Zn(II)Cd(II) and Hg(II) complexesrdquo Journal of Coordination Chem-istry vol 61 no 14 pp 2274ndash2287 2008
[40] T D Thangadurai and S-K Ihm ldquoNovel bidentate ruthe-nium(III) Schiff base complexes synthetic spectral electro-chemical catalytic and antimicrobial studiesrdquo Transition MetalChemistry vol 29 no 2 pp 189ndash195 2004
[41] C J Ballhausen Introduction to Ligand Field Theory McGarwHill New York NY USA 1962
[42] A B P Lever Inorganic Electronic Spectroscopy Elsevier NewYork NY USA 2nd edition 1984
[43] V V Raju K P Balasubramanian C Jayabalakrishnan and VChinnusamy ldquoSynthesis characterization antimicrobial activ-ities and DNA-Binding studies of some Ru(III) complexesof Schiff basesrdquo International Journal of Applied Biology andPharmaceutical Technology vol 3 no 2 pp 76ndash87 2012
[44] K P Balasubramanian K Parameswari V Chinnusamy RPrabhakaran and K Natarajan ldquoSynthesis characterizationelectro chemistry catalytic and biological activities of ruthe-nium(III) complexes with bidentate N OS donor ligandsrdquo
Bioinorganic Chemistry and Applications 11
Spectrochimica ActamdashPart A Molecular and Biomolecular Spec-troscopy vol 65 no 3-4 pp 678ndash683 2006
[45] A Ghantous M Saikali T Rau H Gali-Muhtasib RSchneider-Stock and N Darwiche ldquoInhibition of tumor pro-motion by parthenolide epigenetic modulation of p21rdquo CancerPrevention Research vol 5 no 11 pp 1298ndash1309 2012
[46] W T ShierMammalian Cell Culture on $5 aDay A LabManualof Low Cost Methods University of the Philippines Los BanosCalif USA 1991
[47] G Raja R J Butcher and C Jayabalakrishnan ldquoStudies onsynthesis characterization DNA interaction and cytotoxicity ofruthenium(II) Schiff base complexesrdquo Spectrochimica Acta PartA Molecular and Biomolecular Spectroscopy vol 94 pp 210ndash215 2012
[48] G Raja R J Butcher and C Jayabalakrishnan ldquoSynthesischaracterization DNA binding and cleavage properties andanticancer studies of ruthenium(III) Schiff base complexesrdquoTransition Metal Chemistry vol 37 no 2 pp 169ndash174 2012
[49] I Gulcin O I Kufrevioglu M Oktay and M EBuyukokuroglu ldquoAntioxidant antimicrobial antiulcer andanalgesic activities of nettle (Urtica dioica L)rdquo Journal of Ethno-pharmacology vol 90 no 2-3 pp 205ndash215 2004
[50] M Viuda-Martos Y R Navajas E S Zapata J Fernandez-Lopez and J A Perez-Alvarez ldquoAntioxidant activity of essentialoils of five spice plants widely used in a Mediterranean dietrdquoFlavour and Fragrance Journal vol 25 no 1 pp 13ndash19 2010
[51] S Mathew and T E Abraham ldquoIn vitro antioxidant activity andscavenging effects of Cinnamomum verum leaf extract assayedby different methodologiesrdquo Food and Chemical Toxicology vol44 no 2 pp 198ndash206 2006
systems and cells from impairment caused by oxidative stressor free radicals [21]
DNA binding cleavage potentials scavenging potentialsand anticancer investigations of Schiff base-ruthenium(III)complexes have been accounted for [22] Synthesis spec-tral redox catalytic and biological action investigationof mononuclear Ru(III)-Schiff base structures are reported[23] 221015840-Bipyridine and tetradentate Schiff base ancillaryligands ofmixed-ligand Ru(II) complexes have been reportedfor their electrochemical and Na+ binding properties [24]Catalytic and growth inhibitory activities of Ru(III) mixedligand complexes of 2-hydroxy-1-naphthylideneimines havebeen reported [25]
In this study we report the synthesis characteriza-tion free radical scavenging and anticancer studies offour mononuclear ruthenium(III) complexes of Schiff basesderived from 2101584041015840-dihydroxyacetophenone and ethylenedi-amine as the bridging ligand with RCHO moiety alongsidetheir radicals scavenging action on 11-diphenyl-2-picrylhy-drazyl (DPPH) and 221015840-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and antiproliferative potentials TheSchiff base ligands containing N
2O type tridentate parti-
tions were utilized for the synthesis of the mononuclearruthenium(III)-Schiff base complexes (Scheme 1)
2 Experimental
21 Chemicals and Instrumentations All reagents used wereof analytical grade and used as purchased commerciallyEthylenediamine N1198731015840-dimethylformamide (DMF) andascorbic acid (Vit C) were received from Merck 2101584041015840-dihydroxyacetophenone and RuCl
3sdot3H2O were obtained
from Aldrich 11-Diphenyl-2-picrylhydrazyl (DPPH) 221015840-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS)butylated hydroxytoluene (BHT) and rutin hydrate werereceived from Sigma Chemical Co (St Louis MO USA)Elemental analysis was carried out using Perkin-Elmerelemental analyzer IR spectra were recorded on an FT-IRspectrometer Perkin-Elmer System (Spectrum 2000) viaKBr diskmethod was used for the IR spectra analysis Freshlyprepared DMF solutions of about 10minus3M containing Ru(III)complexes gave the molar conductance at room temperaturewith Crison EC-Meter Basic 30+ conductivity cell Electronicabsorption spectra ranging from 200 to 900 nm wererecorded on a Perkin-Elmer Lambda-25 spectrophotometerStuartmelting point (SMP 11) was used for themelting pointsFour N
2O type tridentate ligands (1Z)-1198731015840-(2-(119864)-[1-(24-
22 Preparation of the Tridentate Schiff Bases (DAEHME MBE and DEE) Ethylenediamine (0015mol)
dissolved in 20mL of alcohol was slowly added to 2101584041015840-dihydroxyacetophenone (0015mol) dissolved in same alco-hol (30mL) and allowed to stir for 60 minutes at room tem-perature and then followed by drop-wise addition ofappropriate aldehyde (RCHO 15mmol) dissolved in 30mLalcohol for 20minutes time interval at room temperature andfurther stirred for 120 minutesThemixture was left standingwith continuous stirring for approximately 36 hours at roomtemperature after which the desired tridentate compoundswere filtered and washed with ethanol to give crystallinesolid The crude product was recrystallized from warmethanol The products were dried in the vacuum at 50∘Covernight to give analytically pure products in good yields(642 to 738)
23 Synthesis of Ru(III)-Tridentate Schiff Base ComplexesRu(III) complexes were prepared by adding (05mmol)ethanol solution of ruthenium(III) chloride to a warmethanolic solution (05mmol) of [DAE][HME][MBE][DEE] respectively The colour of the solutions changedimmediately magnetically stirred and kept under reflux for6 hours The precipitated solids were filtered by suction fromthe reaction medium washed with ethanol and then withdiethyl ether and dried over anhydrous calcium chlorideTheyields were about 557ndash619The synthesis of the complexesis explained in Scheme 1
231 Synthesis of [OHC6H3OHC(CH3)N(C2H4)NC(CH3)NHC6H5RuCl2(H2O)]
[Ru(DAE)Cl2(H2O)]sdotH2O Dark-green solid Yield 1566mg(604) F Wt 51838 g Anal Calcd for C
18H24N3O4RuCl2
() C 4171 H 467 N 811 Found () C 4143 H 454 N829 IR (KBr) ]maxcm
24 In Vitro Antiproliferative Activity The potentials of theRu(III)-tridentate Schiff base complexes to interfere with thegrowth of TK-10 renal cell line UACC-62melanoma cell lineand MCF-7 breast cell lines were determined by SRB assayas previously described [22] 3ndash19 passages of MCF-7 TK-10andUACC-62 cell lineswith plating densities of 7ndash10 000 cellsper well were precultured into 96-well microtitre plates for24 h at 37∘Cwith 95air 5CO
2 and 100 relative humidity
in RPMI medium supplemented with 5 fetal bovine serum
(FBS) 50 120583gmLminus1 (gentamicin) and 2mML-glutamine [27]The compounds were dissolved in DMSO and treated withthe cells after 24 h and diluted in RPMI medium giving riseto 5 concentrations comprising 001 01 0 10 and 100 120583M
Wells containing culture medium were used as controlwhile the wells containing complete culture medium with nocells were used as the blanks Parthenolide was used as thestandard drug in this study The plates were then incubatedfor 48 h after the addition of the compounds Viable cells werefixed to the bottom of each well with cold 50 trichloroaceticacid washed dried and dyed by SRB The unbounded dyewas separated while the protein-bound dye was extractedwith 10mM Tris base and multiwell spectrophotometer atthe wavelength 540 nm was used for its optical densitydetermination IC
50values were determined by plotting the
percentage viability against concentration of compounds ona logarithmic graph to obtain 50 of cell growth inhibitionrelative to the control
25 Antioxidant Assay
251 Scavenging Activity of 11-Diphenyl-2-picrylhydrazyl(DPPH) Radical The antioxidant activity of the preparedRu(III) complexes was studied using spectrophotometer by11-diphenyl-2-picrylhydrazyl (DPPH) method This com-pound is known as a stable readily accessible free radicalwith solubility in methanol giving a purple solution and
4 Bioinorganic Chemistry and Applications
when reacted with antioxidant species changes to an equiv-alent light yellow colour The radical scavenging potentialsof the complexes with DPPH radical were evaluated asdescribed [22] 1mL solution of the compounds in DMFwithconcentrations ranging from 100 to 500120583gmL was mixedthoroughly with equivalent amount of 04mM DPPH inmethanol themixtures were then allowed to react in the darkfor half an hour Measurement of the mixture absorbancewas achieved spectrophotometrically at 517 nm Vitamin Cand rutin were used as the standard drugs All test analysiswas carried out in triplicate The ability of the rutheniumcompounds to scavenge DPPH radical was calculated via thefollowing equation
DPPH radical scavenging activity ()
=Absorbance of control minus Absorbance of sample
Absorbance of control
times 100
(1)
252 ABTS 221015840-Azino-bis(3-ethylbenzothiazoline-6-sulfonicacid) Radical Scavenging Assay ABTS scavenging abilityof the Ru(III)-tridentate Schiff base complexes adopted adescribed method [28] 7mM ABTS solution and 24mMpotassium persulfate solution in equal amounts (1 1) wereused for working solution preparation and allowed to reactin the dark for 12 h at room temperature An absorbanceof 0706 plusmn 0001 units at 734 nm required for the analysiswas obtained by diluting 1mL ABTS+ solution Test samples(1mL) were mixed with 1mL of the ABTS+ solution andabsorbance was read spectrophotometrically at 734 nm Thetest samplesrsquo ABTS scavenging capacity alongside standarddrugs was evaluated Triplicate analysis was carried out Thepercentage inhibition ofABTS radical scavenging activitywasobtained following a previous report [28]
3 Results and Discussion
31 Synthesis and Characterization The obtained com-pounds were of coloured powders stable in atmospherewith a general formula [Ru(LL)Cl
2(H2O)] (LL = monobasic
tridentate Schiff base anion DAE HME MBE and DEE)They were prepared by treating [RuCl
3sdot3H2O] with the
corresponding Schiff base in an equal mole ratio in alcoholas depicted in the Scheme 1 All the complexes are dark-green and sparingly soluble in general organic solvents butsoluble in polar aprotic solvent such as DMF and DMSOthe melting point analysis showed that the Ru(III) complexeswere decomposing before melting The physicoanalyticaldata collected for the compounds are in agreement withthe structural formulae proposed thus confirming the sug-gested mononuclear composition for the Ru(III) complexes(Scheme 1)
32 Molar Conductivity Measurements The molar conduc-tance of the synthesized Ru(III) complexes was measuredin DMF at 10minus3M solution The values were found to be in
the range of 301ndash388 120583Scmminus1 suggesting the nonelectrolyticnature of the complexes in solution [22 29]
33 Infrared Spectra Valuable evidence concerning the envi-ronment of the functional group attached to the rutheniumatom has been obtained from the FTIR spectra The IRspectra of the ligands when compared with those of thenewly synthesized complexes confirm the coordination ofN2O type tridentate ligands to the ruthenium ion The
classification was achieved by comparing the spectra of theligandswith those originating from the coordination betweenruthenium(III) metal ion and the active sites The Schiffbases showed the broad bands in the 3462ndash3477 cmminus1 rangeattributable to the ](OH) cmminus1 vibration Ligand infraredspectra showed that a band at 1605ndash1619 cmminus1 is attributed to](C=N) stretching of the azomethine group based on earlierreports [30] This ](C=N) shift to 1617ndash1639 cmminus1 in all thecomplexes by about 5ndash23 cmminus1 signifies the participation ofazomethine nitrogen in the coordination sphere with theruthenium(III) ion for all the complexes [21 31] A mediumband that corresponds to phenolic oxygen atom ](C-O) isobserved at 1167 and 1245 cmminus1 for the free ligands
The higher shifting of ](C-O) stretching vibrations asobserved in the ruthenium(III) complexes spectra suggeststhat the phenolic OH group of Schiff base DAE HMEMBE and DEE is involved in coordination with rutheniumion after deprotonation [32 33] Seemingly the DAE HMEMBE and DEE ligands act as a tridentate chelating com-pound coordinating to the metal ion via the two nitrogenatoms of the azomethine group as well as O atom of phenolicgroup [21 25] This is further supported by the displacementof ](O-H) in the range 3462ndash3477 cmminus1 in all the complexesThe presence of coordinated water gave a broad band thatappeared in the regions 3416ndash3436 and 813ndash851 cmminus1 this canbe due to ](O-H) stretching and ](O-H) rocking vibrationsrespectively which further confirms the presence of nonli-gand assignable to the rocking mode of water [28 34] Newweak nonligand bands that are not found in the DAE HMEMBE and DEE ligands appeared in the ranges 475ndash548 cmminus1and 436ndash475 cmminus1 in the complexes spectra attributed to](Ru-N) and ](Ru-O) vibrations respectively [35 36] A bandranging from 311ndash346 cmminus1 appeared in the spectra of theRu(III)-Schiff base complexes indicating the presence of twochloride ions in trans position around ruthenium centre [37ndash40]
34 Electronic Absorption Spectra Studies The UV-Vis spec-tra of the Ru(III)-Schiff base complexes in DMF solutionswere recorded at room temperature ranging from 200 to900 nm The nature of DAE HME MBE and DEE ligandsfield around the ruthenium ion was obtained from theelectronic spectra The free ligands showed absorption bandswithin the range of 277ndash393 nm attributable to 120587lowast larr 120587 and120587lowastlarr 119899 transitions relating the benzene ring (Figure 1) The
shifting of these bands in the complexes spectra followed theparticipation of the imine group nitrogen and phenolic groupoxygen in bonding [22 25] Ground state of ruthenium(III) is2T2g where initial excited doublet levels in order of increasing
Bioinorganic Chemistry and Applications 5
0
02
04
06
08
1
12
14
16
260 320 380 440 500 560 620 680
Abso
rban
ce (a
u)
Wavelength (nm)
(a)
0
02
04
06
08
1
12
14
16
18
260 320 380 440 500 560 620 680
Abso
rban
ce (a
u)
Wavelength (nm)
(b)
0
02
04
06
08
1
12
14
260 320 380 440 500 560 620 680
Abso
rban
ce (a
u)
Wavelength (nm)
(c)
0
01
02
03
04
260 320 380 440 500 560 620 680
Abso
rban
ce (a
u)
Wavelength (nm)
(d)
Figure 1 Electronic absorption spectra of the Ru(III) complexes (a) [Ru(DAE)Cl2(H2O)] (b) [Ru(HME)Cl
2(H2O)] (c)
[Ru(MBE)Cl2(H2O)] (d) [Ru(DEE)Cl
2(H2O)]
energy are 2A2g and 2T
1g arising from t42ge1
g configuration[41]
Ru3+ ion with a d5 electronic configuration possesseshigh oxidizing properties and large crystal field parameterAlso charge transfer bands of the type L
120587y rarr T2g were
noticeable within low energy region obscuring weaker bandsthat is due to d-d transitions [22 25] The extinction coef-ficient bands around 613ndash632 nm regions are found to below when compared to the charge transfer bands Thesebands have been assigned to 2T
2g rarr2A2g transition and
are in agreement with the assignment made for similaroctahedral ruthenium(III) complexes [42 43] Absorptionbands within the 452ndash525 nm regions were assigned to thecharge transfer transitions [22 44] Overall the absorptionspectra of the Ru(III)-Schiff base complexes are typical ofoctahedral environment about the ruthenium(III) ions [22]
35 Antiproliferative Activity Investigation into the struc-ture-activity relationship of the isolated Ru(III)-N
2O Schiff
base complexes with respect to different functional groups
on the ligands used for ruthenium ion complex formationhas been conducted via antiproliferative studies Three of theRu(III)-Schiff base compounds alongside parthenolide weresubjected to cell lines tests at different sample concentrationsranging from 001 to 100120583M towards renal cancer cell (TK-10) melanoma cancer cell (UACC-62) and breast cancercell (MCF-7) The cancer cell lines were incubated for 48 hfollowed by the addition of the compounds of variousconcentrations via Sulforhodamine B (SRB) assay [22]
The ruthenium(III) compounds and standard drug(parthenolide) IC
50values are presented in Table 1 and
revealed that the test samples showed significant inhibitionagainst the tested cell lines Figures 2ndash4 represent the cellviability percentages of ruthenium(III)-Schiff base complexesand parthenolide drug against TK-10 UACC-62 and MCF-7 cell lines at different concentrations of ruthenium(III)compounds or parthenolide A high level of antiprolifera-tive potentials against the studied cell lines was exhibitedby parthenolide in accordance with earlier reports [45]The obtained results revealed that treatment of cell lines with
6 Bioinorganic Chemistry and Applications
Table 1 In vitro antiproliferative studies of Ru(III)-Schiff base complexes against TK-10 UACC-62 and MCF-7 cell lines
Compounds Molecular formula Anticancer activity IC50(120583M) 48 h
TK-10 UACC-62 MCF-7[Ru(DAE)Cl
2(H2O)] C
18H24N3O4RuCl2
906 plusmn 118 644 plusmn 038 357 plusmn 109
[Ru(HME)Cl2(H2O)] C
18H23N2O6RuCl2
4109 plusmn 444 631 plusmn 147 488 plusmn 128
[Ru(DEE)Cl2(H2O)] C
17H20N2O4RuCl3
1310 plusmn 281 514 plusmn 109 343 plusmn 148
Parthenolidelowast C15H20O3
050 plusmn 143 089 plusmn 218 044 plusmn 202lowastStandard cytotoxin drug cell lines were treated with different concentrations of the compounds to achieve 50 inhibition of the culture growth when culturedfor 48 h Value represents mean plusmn SD of three independent experimentations
Figure 2 In vitro antiproliferative activity of Ru(III) complexes andparthenolide against human breast cancer cell line (MCF-7)
different concentrations of Ru(III)-Schiff base complexes effi-ciently affected cell viability towardsMCF-7 cells as displayedin Figures 2ndash4 and Table 1 The Ru(III) compounds exhibitedlow to strong in vitro antiproliferative activities againstthe selected cell lines as compared to the standard drug(parthenolide) [Ru(DAE)Cl
2(H2O)] [Ru(HME)Cl
2(H2O)]
and [Ru(DEE)Cl2(H2O)] induced more efficient cell death
with IC50values of 357plusmn109 488plusmn128 and 343plusmn148 120583M
respectively towards human breast cancer cell (MCF-7) cellsthan other investigated cell lines compared with IC
50values
of 044 plusmn 202 120583M MCF-7 for the standard cytotoxin drugparthenolide
The order of activity of the complexes againsthuman melanoma cancer cell (UACC-62) is asfollows [Ru(DEE)Cl
2(H2O)] gt [Ru(HME)Cl
2(H2O)] gt
[Ru(DAE)Cl2(H2O)] With respect to previous report by
Shier [46] compounds exhibiting IC50activity ranging from
10 to 25 120583M are referred to as weak anticancer drugs whilethose with IC
50action between 5 and 10 120583M are moderate
and the compounds possessing activity less than (lt) 500120583M
Figure 3 In vitro antiproliferative activity of Ru(III) complexes andparthenolide against human melanoma cancer cell (UACC-62)
are considered as strong agents Thus the Ru(III) complexesexhibited a weak to strong activity against the investigatedcancer cell lines with the following order of activity MCF-7 gt UACC-62 gt TK-10 However [Ru(DAE)Cl
2(H2O)]
showed the highest antiproliferative activity with IC50
valves of 357 plusmn 109 644 plusmn 038 and 906 plusmn 118 120583M forMCF-7 UACC-62 and TK-10 respectively The biochemicalactivity could be due to the methoxy alkyl chloride groupsubstituents and bridge spacer ethylenediamine whichcould have played a vital role in antiproliferative potentialsof the Ru(III)-N
2O Schiff base complexes In vitro anticancer
activity of the synthesized Ru(III) complexes in this studywas compared with Ru complexes reported by other authorsand found that [Ru(DAE)Cl
2(H2O)] [Ru(HME)Cl
2(H2O)]
and [Ru(DEE)Cl2(H2O)] complexes exhibited higher
antitumor activities [RuCl(CO)(PPh3)L] reported by Raja et
al [47] against human cervical carcinoma cell line (HeLa)after exposure for 48 h gave an IC
50value in the range of
316 120583M and [RuCl2(AsPh
3)L] with an IC
50value of 378120583M
[48] Raju et al [43] reported ruthenium(III) Schiff basecomplexes of the type [RuX
2(PPh3)2(L)] (where X = Cl or
Bioinorganic Chemistry and Applications 7
020
4060
80
100
00101
1
10
100
ce
ll vi
abili
ty
[Parthenolide][Ru(DAE)Cl2(H2O)]
[Ru(HME)Cl2(H2O)][Ru(DEE)Cl2(H2O)]
Concentration (120583M)
Figure 4 In vitro antiproliferative activity of Ru(III) complexes andparthenolide against human renal cancer cell (TK-10)
Br L = monobasic bidentate ligand) complex to have IC50
value in the range of 452120583M
36 Antioxidant Capacity Different antioxidant techniquesand modifications have been put forward to evaluate antiox-idants reactivity and functionality in foods and biologicalsystems as a means of checkmating variety of patholog-ical activities such as cellular injury and aging processthese damaging occurrences are caused by free radicalsHence two free radicals were used for in vitro antioxi-dants activities of the test samples in this study namely11-diphenyl-2-picrylhydrazyl (DPPH) and 221015840-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS)
361 DPPHRadical Scavenging Assay The activity of antiox-idants on DPPH radical is believed to be centred on theirability to donate hydrogen [22] DPPH has been a stablefree radical with the ability to accept hydrogen radical or anelectron and then become a stable molecule [49]
The mode of rummaging the DPPH radical hasextensively been used to appraise antioxidant activities oftest samples in a moderately short period of time comparedto other procedures [49] The reduction in the DPPH radicalcapability is calculated by the decrease in its absorbanceat 517 nm prompted by antioxidants [50] The reduction ofDPPH radical intensity in this study is due to the interactionof Ru(III) complexes with radical and as such scavengingthe radicals by hydrogen donation (Scheme 2) The DPPHactivities by the Ru(III)-N
2O Schiff base complexes exhibit
strong electron donating power when compared to thestandards ascorbic acid and rutin as displayed in Figure 5The calculated IC
Figure 5 DPPH scavenging potential of Ru(III)-Schiff base com-plexes
coefficient) values of Ru(III) compounds are listed in Table 2Compounds [Ru(DAE)Cl
2(H2O)] [Ru(HME)Cl
2(H2O)]
[Ru(MBE)Cl2(H2O)] and [Ru(DEE)Cl
2(H2O)] with an IC
50
value of 160plusmn068 154plusmn044 163plusmn105 and 151plusmn050 120583Mrespectively exhibited higher activity against DPPH thanthe commercially available Vit C and rutin (standard)however [Ru(DEE)Cl
2(H2O)] showed the highest activity of
all investigated ruthenium(III) samples with an IC50value of
151 plusmn 050 120583MScavenging ability of the test samples on the
DPPH radical can be ranked in the following order[Ru(DEE)Cl
2(H2O)] gt [Ru(HME)Cl
2(H2O)] gt
[Ru(DAE)Cl2(H2O)] gt [Ru(MBE)Cl
2(H2O)] gt [Vit C]
gt [rutin]The scavenging effect of the DAE HME MBE andDEE ligands is lower as compared to their correspondingRu(III) complexes owing to the coordination of the organicmolecules to the Ru3+ ion It is further supported by theobserved discolouration from purple DPPH radical solutionto yellow solution showing scavenging of the DPPH radicalsby hydrogen donation (Scheme 2) Hence these complexescould be effective therapeutic agentrsquos preparation for thetreatment of chronic conditions such as cardiovascularneurodegenerative and arteriosclerosis diseases [21]
362 221015840-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)Radical Scavenging Activity To further confirm the synthe-sized Ru(III)-N
2O Schiff base complexes antiradical poten-
tial we examined the ABTS assay in this study A well-knownprotonated radical like 221015840-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) possesses characteristic absorbancemaxima at 734 nm and decreases with the scavenging of theproton radicals [51]The assaymeasures radical scavenging byelectron donation The outcome of Ru(III)-N
2O Schiff base
complexes alongside the standard drugs on ABTS radical ispresented in Table 2 At 734 nm the absorbance of activeABTSlowast solution noticeably declined upon the addition ofdifferent concentrations of ruthenium(III) samples the sametrend was also observed for the standard drugs butylated
8 Bioinorganic Chemistry and Applications
N N NH+
Cl
Cl
N N
O
HO
HRuCl
Cl
N N
OHRu
+
DPPH radical Reduced DPPH
Antioxidant
OH2 OH2
O2N
O2N
O2N
O2N
NO2
H3C H3C
OCH3 OCH3
OCH3OCH3
NO2
517 nm
O∙
N∙
Scheme 2 Conversion of DPPHlowast (purple) to its corresponding hydrazine form (yellow) by the addition of Ru(III) compounds to DPPHlowastdue to proton transfer
Table 2 Radical scavenging abilities (IC50plusmn SD 120583M) of Ru(III)-Schiff base complexes and standard drugs
Rutinlowast 252 plusmn 160 0798 283 plusmn 184 0983Vit Clowast 192 plusmn 107 0978 mdash mdashBHTlowast mdash mdash 164 plusmn 154 0919119899 = 3119883plusmn SEM IC50 growth inhibitory concentration when the inhibition of the tested compounds was 50 the tested compound concentration was IC501198772 correlation coefficient lowastStandards
hydroxytoluene (BHT) and rutin hydrate with the percentageinhibition displayed in Figure 6
The efficacy of the tested samples in quenching ATBSlowastradicals in the system was observed at 100120583gmL the lowestconcentration and Ru(III) complexes exhibited higher ABTS inhibition than the standards [Ru(DEE)Cl
2(H2O)] com-
plex exhibited the highest ABTS scavenging activity amongstthe studied ruthenium(III) complexes with an IC
50value
of 324 plusmn 093 120583M and 0855 1198772 (correlation coefficient) aslisted in Table 2 while complexes of [Ru(DAE)Cl
2(H2O)]
[Ru(HME)Cl2(H2O)] and [Ru(MBE)Cl
2(H2O)] had an IC
50
value of 330 plusmn 089 427 plusmn 117 and 330 plusmn 148 120583Mrespectively
The ABTS scavenging activity pattern of the complexesis ranked in the following order [Ru(HME)Cl
2(H2O)]
lt [Ru(MBE)Cl2(H2O)] = [Ru(DAE)Cl
2(H2O)] lt
[Ru(DEE)Cl2(H2O)] With this result the antiradical
studies showed that the synthesised Ru(III)-N2O Schiff base
complexes may be useful in developing therapeutic agentfor averting cell oxidative damage and as radicals chainterminator This is because various free radicals generated in
the system often lead to cancer cellular injury aging processand cardiovascular diseases [21]
4 Conclusion
In this study we present the synthesis of Ru(III) Schiff basecomplexes formulated as [Ru(LL)Cl
2(H2O)] (LL = DAE
HME MBE and DEE) The complexes were character-ized using the microanalytical conductance electronic andvibrational spectral analysis FTIR spectral data showed thatthe ligand acts as tridentate chelating ligand coordinatingthrough azomethine nitrogen and phenol oxygen atomThe microanalyses were in conformity with the proposedstructures Conductance measurements showed the com-plexes to be nonelectrolytes in DMF Octahedral structureswere assigned to these complexes based on the elementaland spectral information In vitro antiproliferative studiesof the Ru(III) complexes gave a weak to strong inhibitionagainst the studied cancer cell lines with the followingactivity order MCF-7 gt UACC-62 gt TK-10 Significantly
Figure 6 ABTS rummaging activity of Ru(III)-Schiff base com-plexes
further investigation on the compounds free radical scav-enging properties revealed that Ru(III)-Schiff base complexespossessed considerable antioxidant activities The outcomefrom DPPH and ABTS inhibition studies revealed that thecompounds are proficient in donating electron or hydrogenatom and subsequently terminate the chain reactions ina dose-dependent pattern Scavenging ability of the testsamples on the DPPH radicals can be ranked in the fol-lowing order [Ru(DEE)Cl
2(H2O)]gt [Ru(HME)Cl
2(H2O)]gt
[Ru(DAE)Cl2(H2O)] gt [Ru(MBE)Cl
2(H2O)] Thus Ru(III)-
N2O Schiff base complexes showed stronger inhibition of
DPPH at various concentrations
Competing Interests
No conflict of interests regarding the publication of this paperis declared by the authors
Acknowledgments
The authors acknowledge GovanMbeki Research and Devel-opment Centre (GMRDC) University of Fort Hare forfinancial support and IPE acknowledges National ResearchFoundation and Sasol Inzalo Foundation for the award ofPhD scholarship
References
[1] A Butler and J V Walker ldquoMarine haloperoxidasesrdquo ChemicalReviews vol 93 no 5 pp 1937ndash1944 1993
[2] Y Shechter I Goldwaser M Mironchik M Fridkin and DGefel ldquoHistoric perspective and recent developments on theinsulin-like actions of vanadium toward developing vanadium-based drugs for diabetesrdquo Coordination Chemistry Reviews vol237 no 1-2 pp 3ndash11 2003
[3] A M B Bastos J G da Silva P I S Maia et al ldquoOxo-vanadium(IV) and (V) complexes of acetylpyridine-derivedsemicarbazones exhibit insulin-like activityrdquoPolyhedron vol 27no 6 pp 1787ndash1794 2008
[4] R R Eady ldquoCurrent status of structure function relationshipsof vanadiumnitrogenaserdquoCoordination Chemistry Reviews vol237 no 1-2 pp 23ndash30 2003
[5] K H Thompson J H McNeill and C Orvig ldquoVanadiumcompounds as insulin mimicsrdquo Chemical Reviews vol 99 no9 pp 2561ndash2572 1999
[6] G Grivani G Bruno H A Rudbari A D Khalaji and PPourteimouri ldquoSynthesis characterization and crystal structuredetermination of a new oxovanadium(IV) Schiff base complexthe catalytic activity in the epoxidation of cyclooctenerdquo Inor-ganic Chemistry Communications vol 18 pp 15ndash20 2012
[7] J W Pyrz A L Roe L J Stern and L Que Jr ldquoModel studiesof iron-tyrosinate proteinsrdquo Journal of the American ChemicalSociety vol 107 no 3 pp 614ndash620 1985
[8] M Tumer B Erdogan H Koksal S Serin and M Y NutkuldquoPreparation spectroscopic characterisation and thermal anal-yses studies of theCu(II) Pd(II) andVO(IV) complexes of someSchiff base ligandsrdquo Synthesis and Reactivity in Inorganic andMetal-Organic Chemistry vol 28 no 4 pp 529ndash542 1998
[9] J Hine and C Y Yeh ldquoEquilibrium in formation and conforma-tional isomerization of imines derived from isobutyraldehydeand saturated aliphatic primary aminesrdquo Journal of the Ameri-can Chemical Society vol 89 no 11 pp 2669ndash2676 1967
[10] T Opstal and F Verpoort ldquoSynthesis of highly active rutheniumindenylidene complexes for atom-transfer radical polymer-ization and ring-opening-metathesis polymerizationrdquo Ange-wandte ChemiemdashInternational Edition vol 42 no 25 pp 2876ndash2879 2003
[11] B De Clercq F Lefebvre and F Verpoort ldquoImmobilization ofmultifunctional Schiff base containing ruthenium complexeson MCM-41rdquo Applied Catalysis A General vol 247 no 2 pp345ndash364 2003
[12] A Golcu M Tumer H Demirelli and R A WheatleyldquoCd(II) andCu(II) complexes of polydentate Schiff base ligandssynthesis characterization properties and biological activityrdquoInorganica Chimica Acta vol 358 no 6 pp 1785ndash1797 2005
[13] NMishra K Poonia and D Kumar ldquoAn overview of biologicalaspects of Schiff base metal complexesrdquo International Journal ofAdvancements in ResearchampTechnology vol 2 no 8 pp 52ndash662013
[14] L-A H Allen L S Schlesinger and B Kang ldquoVirulent strainsof Helicobacter pylori demonstrate delayed phagocytosis andstimulate homotypic phagosome fusion in macrophagesrdquo TheJournal of Experimental Medicine vol 191 no 1 pp 115ndash1272000
[15] L A Calderon R C L Teles J R S A Leite C Bloch JrS Astolfi-Filho and S M Freitas ldquoSerine protease inhibitorsfromAmazon Leguminosae seeds purification and preliminarycharacterization of two chymotrypsin inhibitors from Ingaumbraticardquo Protein and Peptide Letters vol 8 no 6 pp 485ndash493 2001
[16] P G Cozzi ldquoMetal-Salen Schiff base complexes in catalysispractical aspectsrdquo Chemical Society Reviews vol 33 no 7 pp410ndash421 2004
[17] T Katsuki ldquoUnique asymmetric catalysis of cis-120573 metal com-plexes of salen and its related Schiff-base ligandsrdquo ChemicalSociety Reviews vol 33 no 7 pp 437ndash444 2004
[18] I M I Fakhr N A Hamdy M A Radwan and Y M AhmedldquoSynthesis of new bioactive benzothiophene derivativesrdquo Egyp-tian Journal of Chemistry vol 47 pp 201ndash215 2004
[19] R A A Ammar and A-N M A Alaghaz ldquoSynthesisspectroscopic characterization and potentiometric studies of
10 Bioinorganic Chemistry and Applications
a tetradentate [N2O2] schiff base NN1015840-bis(2-hydroxyben-
zylidene)-11-diaminoethane and its Co(II)Ni(II)Cu(II) andZn(II) complexesrdquo International Journal of ElectrochemicalScience vol 8 no 6 pp 8686ndash8699 2013
[20] A S Gaballa M S Asker A S Barakat and S M TelebldquoSynthesis characterization and biological activity of someplatinum(II) complexes with Schiff bases derived from salicy-laldehyde 2-furaldehyde and phenylenediaminerdquo Spectrochim-ica Acta Part A Molecular and Biomolecular Spectroscopy vol67 no 1 pp 114ndash121 2007
[21] I P Ejidike and P A Ajibade ldquoTransition metal complexesof symmetrical and asymmetrical Schiff bases as antibacterialantifungal antioxidant and anticancer agents progress andprospectsrdquo Reviews in Inorganic Chemistry vol 35 no 4 pp191ndash224 2015
[22] I P Ejidike and P A Ajibade ldquoSynthesis characterization andin vitro antioxidant and anticancer studies of ruthenium(III)complexes of symmetric and asymmetric tetradentate Schiffbasesrdquo Journal of Coordination Chemistry vol 68 no 14 pp2552ndash2564 2015
[23] N P Priya S Arunachalam A Manimaran D Muthupriyaand C Jayabalakrishnan ldquoMononuclear Ru(III) Schiff basecomplexes synthesis spectral redox catalytic and biologicalactivity studiesrdquo Spectrochimica Acta Part A Molecular andBiomolecular Spectroscopy vol 72 no 3 pp 670ndash676 2009
[24] L Mishra R Prajapati and K K Pandey ldquoMixed-ligand Ru(II)complexes with 221015840-bipyridine and tetradentate Schiff basesauxiliary ligands Synthesis physico-chemical study DFT anal-ysis electrochemical and Na+ binding propertiesrdquo Spectrochim-ica ActamdashPart A Molecular and Biomolecular Spectroscopy vol70 no 1 pp 79ndash85 2008
[25] G Venkatachalam and R Ramesh ldquoCatalytic and biologicalactivities of Ru(III) mixed ligand complexes containing NOdonor of 2-hydroxy-1-naphthylideneiminesrdquo SpectrochimicaActa Part A Molecular and Biomolecular Spectroscopy vol 61no 9 pp 2081ndash2087 2005
[26] I P Ejidike and P A Ajibade ldquoSynthesis and in vitro anti-cancer antibacterial and antioxidant studies of unsymmet-rical Schiff base derivatives of 4-[(1E)-N-(2-aminoethyl)eth-animidoyl]benzene-13-diolrdquo Research on Chemical Intermedi-ates vol 42 no 8 pp 6543ndash6555 2016
[27] K I Ansari I Hussain H K Das and S S Mandal ldquoOver-expression of human histone methylase MLL1 upon exposureto a food contaminant mycotoxin deoxynivalenolrdquo The FEBSJournal vol 276 no 12 pp 3299ndash3307 2009
[28] I P Ejidike and P A Ajibade ldquoSynthesis characterization andbiological studies of metal(II) complexes of (3E)-3-[(2-(119864)-[1-(24-Dihydroxyphenyl) ethylidene]aminoethyl)imino]-1-phenylbutan-1-one schiff baserdquo Molecules vol 20 no 6 pp9788ndash9802 2015
[29] C A Bolos A T Chaviara D Mourelatos et al ldquoSynthesischaracterization toxicity cytogenetic and in vivo antitumorstudies of 11-dithiolate Cu(II) complexes with di- tri- tetra-amines and 13-thiazoles Structure-activity correlationrdquo Bioor-ganic amp Medicinal Chemistry vol 17 no 8 pp 3142ndash3151 2009
[30] P K Das N Panda and N K Behera ldquoSynthesis character-ization and antimicrobial activities of Schiff base complexesderived from isoniazid and diacetylmonoximerdquo InternationalJournal of Innovative Science Engineering amp Technology vol 3no 1 pp 42ndash54 2016
[31] L Mitu M Ilis N Raman M Imran and S RavichandranldquoTransition metal complexes of isonicotinoylndashhydrazone-4-diphenylaminobenzaldehyde synthesis characterization andantimicrobial studiesrdquo E-Journal of Chemistry vol 9 no 1 pp365ndash372 2012
[32] S A Ali A A Soliman M M Aboaly and R M RamadanldquoChromium molybdenum and ruthenium complexes of 2-hydroxyacetophenone schiff basesrdquo Journal of CoordinationChemistry vol 55 no 10 pp 1161ndash1170 2002
[33] K N Kumar R Ramesh and Y Liu ldquoSynthesis structureand catalytic activity of cycloruthenated carbonyl complexescontaining arylazo phenolate ligandsrdquo Journal of MolecularCatalysis A Chemical vol 265 no 1-2 pp 218ndash226 2007
[34] I P Ejidike and P A Ajibade ldquoSynthesis characterizationantioxidant and antibacterial studies of some metal(II)complexes of tetradentate schiff base ligand (4E)-4-[(2-(119864)-[1-(24-dihydroxyphenyl)ethylidene]aminoethyl)imino]pentan-2-onerdquo Bioinorganic Chemistry and Applications vol 2015Article ID 890734 9 pages 2015
[35] J S Casas A Castineiras F Condori et al ldquoDiorganotin(IV)-promoted deamination of amino acids by pyridoxal SnR2
2+
complexes of pyridoxal 51015840-phosphate and of the Schiff basepyridoxal-pyridoxamine (PLPM) and antibacterial activities ofPLPM and [SnR
2(PLPM-2H)] (R=Me Et Bu Ph)rdquo Polyhedron
vol 22 no 1 pp 53ndash65 2003[36] P J K Inba B Annaraj S Thalamuthu and M A Nee-
lakantan ldquoCu(II) Ni(II) and Zn(II) complexes of salan-typeligand containing ester groups synthesis characterizationelectrochemical properties and in vitro biological activitiesrdquoBioinorganic Chemistry and Applications vol 2013 Article ID439848 11 pages 2013
[37] K Shanker R Rohini V Ravinder P M Reddy and Y-P HoldquoRu(II) complexes of N
4and N
2O2macrocyclic Schiff base lig-
ands their antibacterial and antifungal studiesrdquo SpectrochimicaActa Part A Molecular and Biomolecular Spectroscopy vol 73no 1 pp 205ndash211 2009
[38] M Alias H Kassum and C Shakir ldquoSynthesis physicalcharacterization and biological evaluation of Schiff base M(II)complexesrdquo Journal of the Association of Arab Universities forBasic and Applied Sciences vol 15 no 1 pp 28ndash34 2014
[39] K Shivakumar Shashidhar P V Reddy and M B HallildquoSynthesis spectral characterization and biological activity ofbenzofuran Schiff bases with Co(II) Ni(II) Cu(II) Zn(II)Cd(II) and Hg(II) complexesrdquo Journal of Coordination Chem-istry vol 61 no 14 pp 2274ndash2287 2008
[40] T D Thangadurai and S-K Ihm ldquoNovel bidentate ruthe-nium(III) Schiff base complexes synthetic spectral electro-chemical catalytic and antimicrobial studiesrdquo Transition MetalChemistry vol 29 no 2 pp 189ndash195 2004
[41] C J Ballhausen Introduction to Ligand Field Theory McGarwHill New York NY USA 1962
[42] A B P Lever Inorganic Electronic Spectroscopy Elsevier NewYork NY USA 2nd edition 1984
[43] V V Raju K P Balasubramanian C Jayabalakrishnan and VChinnusamy ldquoSynthesis characterization antimicrobial activ-ities and DNA-Binding studies of some Ru(III) complexesof Schiff basesrdquo International Journal of Applied Biology andPharmaceutical Technology vol 3 no 2 pp 76ndash87 2012
[44] K P Balasubramanian K Parameswari V Chinnusamy RPrabhakaran and K Natarajan ldquoSynthesis characterizationelectro chemistry catalytic and biological activities of ruthe-nium(III) complexes with bidentate N OS donor ligandsrdquo
Bioinorganic Chemistry and Applications 11
Spectrochimica ActamdashPart A Molecular and Biomolecular Spec-troscopy vol 65 no 3-4 pp 678ndash683 2006
[45] A Ghantous M Saikali T Rau H Gali-Muhtasib RSchneider-Stock and N Darwiche ldquoInhibition of tumor pro-motion by parthenolide epigenetic modulation of p21rdquo CancerPrevention Research vol 5 no 11 pp 1298ndash1309 2012
[46] W T ShierMammalian Cell Culture on $5 aDay A LabManualof Low Cost Methods University of the Philippines Los BanosCalif USA 1991
[47] G Raja R J Butcher and C Jayabalakrishnan ldquoStudies onsynthesis characterization DNA interaction and cytotoxicity ofruthenium(II) Schiff base complexesrdquo Spectrochimica Acta PartA Molecular and Biomolecular Spectroscopy vol 94 pp 210ndash215 2012
[48] G Raja R J Butcher and C Jayabalakrishnan ldquoSynthesischaracterization DNA binding and cleavage properties andanticancer studies of ruthenium(III) Schiff base complexesrdquoTransition Metal Chemistry vol 37 no 2 pp 169ndash174 2012
[49] I Gulcin O I Kufrevioglu M Oktay and M EBuyukokuroglu ldquoAntioxidant antimicrobial antiulcer andanalgesic activities of nettle (Urtica dioica L)rdquo Journal of Ethno-pharmacology vol 90 no 2-3 pp 205ndash215 2004
[50] M Viuda-Martos Y R Navajas E S Zapata J Fernandez-Lopez and J A Perez-Alvarez ldquoAntioxidant activity of essentialoils of five spice plants widely used in a Mediterranean dietrdquoFlavour and Fragrance Journal vol 25 no 1 pp 13ndash19 2010
[51] S Mathew and T E Abraham ldquoIn vitro antioxidant activity andscavenging effects of Cinnamomum verum leaf extract assayedby different methodologiesrdquo Food and Chemical Toxicology vol44 no 2 pp 198ndash206 2006
24 In Vitro Antiproliferative Activity The potentials of theRu(III)-tridentate Schiff base complexes to interfere with thegrowth of TK-10 renal cell line UACC-62melanoma cell lineand MCF-7 breast cell lines were determined by SRB assayas previously described [22] 3ndash19 passages of MCF-7 TK-10andUACC-62 cell lineswith plating densities of 7ndash10 000 cellsper well were precultured into 96-well microtitre plates for24 h at 37∘Cwith 95air 5CO
2 and 100 relative humidity
in RPMI medium supplemented with 5 fetal bovine serum
(FBS) 50 120583gmLminus1 (gentamicin) and 2mML-glutamine [27]The compounds were dissolved in DMSO and treated withthe cells after 24 h and diluted in RPMI medium giving riseto 5 concentrations comprising 001 01 0 10 and 100 120583M
Wells containing culture medium were used as controlwhile the wells containing complete culture medium with nocells were used as the blanks Parthenolide was used as thestandard drug in this study The plates were then incubatedfor 48 h after the addition of the compounds Viable cells werefixed to the bottom of each well with cold 50 trichloroaceticacid washed dried and dyed by SRB The unbounded dyewas separated while the protein-bound dye was extractedwith 10mM Tris base and multiwell spectrophotometer atthe wavelength 540 nm was used for its optical densitydetermination IC
50values were determined by plotting the
percentage viability against concentration of compounds ona logarithmic graph to obtain 50 of cell growth inhibitionrelative to the control
25 Antioxidant Assay
251 Scavenging Activity of 11-Diphenyl-2-picrylhydrazyl(DPPH) Radical The antioxidant activity of the preparedRu(III) complexes was studied using spectrophotometer by11-diphenyl-2-picrylhydrazyl (DPPH) method This com-pound is known as a stable readily accessible free radicalwith solubility in methanol giving a purple solution and
4 Bioinorganic Chemistry and Applications
when reacted with antioxidant species changes to an equiv-alent light yellow colour The radical scavenging potentialsof the complexes with DPPH radical were evaluated asdescribed [22] 1mL solution of the compounds in DMFwithconcentrations ranging from 100 to 500120583gmL was mixedthoroughly with equivalent amount of 04mM DPPH inmethanol themixtures were then allowed to react in the darkfor half an hour Measurement of the mixture absorbancewas achieved spectrophotometrically at 517 nm Vitamin Cand rutin were used as the standard drugs All test analysiswas carried out in triplicate The ability of the rutheniumcompounds to scavenge DPPH radical was calculated via thefollowing equation
DPPH radical scavenging activity ()
=Absorbance of control minus Absorbance of sample
Absorbance of control
times 100
(1)
252 ABTS 221015840-Azino-bis(3-ethylbenzothiazoline-6-sulfonicacid) Radical Scavenging Assay ABTS scavenging abilityof the Ru(III)-tridentate Schiff base complexes adopted adescribed method [28] 7mM ABTS solution and 24mMpotassium persulfate solution in equal amounts (1 1) wereused for working solution preparation and allowed to reactin the dark for 12 h at room temperature An absorbanceof 0706 plusmn 0001 units at 734 nm required for the analysiswas obtained by diluting 1mL ABTS+ solution Test samples(1mL) were mixed with 1mL of the ABTS+ solution andabsorbance was read spectrophotometrically at 734 nm Thetest samplesrsquo ABTS scavenging capacity alongside standarddrugs was evaluated Triplicate analysis was carried out Thepercentage inhibition ofABTS radical scavenging activitywasobtained following a previous report [28]
3 Results and Discussion
31 Synthesis and Characterization The obtained com-pounds were of coloured powders stable in atmospherewith a general formula [Ru(LL)Cl
2(H2O)] (LL = monobasic
tridentate Schiff base anion DAE HME MBE and DEE)They were prepared by treating [RuCl
3sdot3H2O] with the
corresponding Schiff base in an equal mole ratio in alcoholas depicted in the Scheme 1 All the complexes are dark-green and sparingly soluble in general organic solvents butsoluble in polar aprotic solvent such as DMF and DMSOthe melting point analysis showed that the Ru(III) complexeswere decomposing before melting The physicoanalyticaldata collected for the compounds are in agreement withthe structural formulae proposed thus confirming the sug-gested mononuclear composition for the Ru(III) complexes(Scheme 1)
32 Molar Conductivity Measurements The molar conduc-tance of the synthesized Ru(III) complexes was measuredin DMF at 10minus3M solution The values were found to be in
the range of 301ndash388 120583Scmminus1 suggesting the nonelectrolyticnature of the complexes in solution [22 29]
33 Infrared Spectra Valuable evidence concerning the envi-ronment of the functional group attached to the rutheniumatom has been obtained from the FTIR spectra The IRspectra of the ligands when compared with those of thenewly synthesized complexes confirm the coordination ofN2O type tridentate ligands to the ruthenium ion The
classification was achieved by comparing the spectra of theligandswith those originating from the coordination betweenruthenium(III) metal ion and the active sites The Schiffbases showed the broad bands in the 3462ndash3477 cmminus1 rangeattributable to the ](OH) cmminus1 vibration Ligand infraredspectra showed that a band at 1605ndash1619 cmminus1 is attributed to](C=N) stretching of the azomethine group based on earlierreports [30] This ](C=N) shift to 1617ndash1639 cmminus1 in all thecomplexes by about 5ndash23 cmminus1 signifies the participation ofazomethine nitrogen in the coordination sphere with theruthenium(III) ion for all the complexes [21 31] A mediumband that corresponds to phenolic oxygen atom ](C-O) isobserved at 1167 and 1245 cmminus1 for the free ligands
The higher shifting of ](C-O) stretching vibrations asobserved in the ruthenium(III) complexes spectra suggeststhat the phenolic OH group of Schiff base DAE HMEMBE and DEE is involved in coordination with rutheniumion after deprotonation [32 33] Seemingly the DAE HMEMBE and DEE ligands act as a tridentate chelating com-pound coordinating to the metal ion via the two nitrogenatoms of the azomethine group as well as O atom of phenolicgroup [21 25] This is further supported by the displacementof ](O-H) in the range 3462ndash3477 cmminus1 in all the complexesThe presence of coordinated water gave a broad band thatappeared in the regions 3416ndash3436 and 813ndash851 cmminus1 this canbe due to ](O-H) stretching and ](O-H) rocking vibrationsrespectively which further confirms the presence of nonli-gand assignable to the rocking mode of water [28 34] Newweak nonligand bands that are not found in the DAE HMEMBE and DEE ligands appeared in the ranges 475ndash548 cmminus1and 436ndash475 cmminus1 in the complexes spectra attributed to](Ru-N) and ](Ru-O) vibrations respectively [35 36] A bandranging from 311ndash346 cmminus1 appeared in the spectra of theRu(III)-Schiff base complexes indicating the presence of twochloride ions in trans position around ruthenium centre [37ndash40]
34 Electronic Absorption Spectra Studies The UV-Vis spec-tra of the Ru(III)-Schiff base complexes in DMF solutionswere recorded at room temperature ranging from 200 to900 nm The nature of DAE HME MBE and DEE ligandsfield around the ruthenium ion was obtained from theelectronic spectra The free ligands showed absorption bandswithin the range of 277ndash393 nm attributable to 120587lowast larr 120587 and120587lowastlarr 119899 transitions relating the benzene ring (Figure 1) The
shifting of these bands in the complexes spectra followed theparticipation of the imine group nitrogen and phenolic groupoxygen in bonding [22 25] Ground state of ruthenium(III) is2T2g where initial excited doublet levels in order of increasing
Bioinorganic Chemistry and Applications 5
0
02
04
06
08
1
12
14
16
260 320 380 440 500 560 620 680
Abso
rban
ce (a
u)
Wavelength (nm)
(a)
0
02
04
06
08
1
12
14
16
18
260 320 380 440 500 560 620 680
Abso
rban
ce (a
u)
Wavelength (nm)
(b)
0
02
04
06
08
1
12
14
260 320 380 440 500 560 620 680
Abso
rban
ce (a
u)
Wavelength (nm)
(c)
0
01
02
03
04
260 320 380 440 500 560 620 680
Abso
rban
ce (a
u)
Wavelength (nm)
(d)
Figure 1 Electronic absorption spectra of the Ru(III) complexes (a) [Ru(DAE)Cl2(H2O)] (b) [Ru(HME)Cl
2(H2O)] (c)
[Ru(MBE)Cl2(H2O)] (d) [Ru(DEE)Cl
2(H2O)]
energy are 2A2g and 2T
1g arising from t42ge1
g configuration[41]
Ru3+ ion with a d5 electronic configuration possesseshigh oxidizing properties and large crystal field parameterAlso charge transfer bands of the type L
120587y rarr T2g were
noticeable within low energy region obscuring weaker bandsthat is due to d-d transitions [22 25] The extinction coef-ficient bands around 613ndash632 nm regions are found to below when compared to the charge transfer bands Thesebands have been assigned to 2T
2g rarr2A2g transition and
are in agreement with the assignment made for similaroctahedral ruthenium(III) complexes [42 43] Absorptionbands within the 452ndash525 nm regions were assigned to thecharge transfer transitions [22 44] Overall the absorptionspectra of the Ru(III)-Schiff base complexes are typical ofoctahedral environment about the ruthenium(III) ions [22]
35 Antiproliferative Activity Investigation into the struc-ture-activity relationship of the isolated Ru(III)-N
2O Schiff
base complexes with respect to different functional groups
on the ligands used for ruthenium ion complex formationhas been conducted via antiproliferative studies Three of theRu(III)-Schiff base compounds alongside parthenolide weresubjected to cell lines tests at different sample concentrationsranging from 001 to 100120583M towards renal cancer cell (TK-10) melanoma cancer cell (UACC-62) and breast cancercell (MCF-7) The cancer cell lines were incubated for 48 hfollowed by the addition of the compounds of variousconcentrations via Sulforhodamine B (SRB) assay [22]
The ruthenium(III) compounds and standard drug(parthenolide) IC
50values are presented in Table 1 and
revealed that the test samples showed significant inhibitionagainst the tested cell lines Figures 2ndash4 represent the cellviability percentages of ruthenium(III)-Schiff base complexesand parthenolide drug against TK-10 UACC-62 and MCF-7 cell lines at different concentrations of ruthenium(III)compounds or parthenolide A high level of antiprolifera-tive potentials against the studied cell lines was exhibitedby parthenolide in accordance with earlier reports [45]The obtained results revealed that treatment of cell lines with
6 Bioinorganic Chemistry and Applications
Table 1 In vitro antiproliferative studies of Ru(III)-Schiff base complexes against TK-10 UACC-62 and MCF-7 cell lines
Compounds Molecular formula Anticancer activity IC50(120583M) 48 h
TK-10 UACC-62 MCF-7[Ru(DAE)Cl
2(H2O)] C
18H24N3O4RuCl2
906 plusmn 118 644 plusmn 038 357 plusmn 109
[Ru(HME)Cl2(H2O)] C
18H23N2O6RuCl2
4109 plusmn 444 631 plusmn 147 488 plusmn 128
[Ru(DEE)Cl2(H2O)] C
17H20N2O4RuCl3
1310 plusmn 281 514 plusmn 109 343 plusmn 148
Parthenolidelowast C15H20O3
050 plusmn 143 089 plusmn 218 044 plusmn 202lowastStandard cytotoxin drug cell lines were treated with different concentrations of the compounds to achieve 50 inhibition of the culture growth when culturedfor 48 h Value represents mean plusmn SD of three independent experimentations
Figure 2 In vitro antiproliferative activity of Ru(III) complexes andparthenolide against human breast cancer cell line (MCF-7)
different concentrations of Ru(III)-Schiff base complexes effi-ciently affected cell viability towardsMCF-7 cells as displayedin Figures 2ndash4 and Table 1 The Ru(III) compounds exhibitedlow to strong in vitro antiproliferative activities againstthe selected cell lines as compared to the standard drug(parthenolide) [Ru(DAE)Cl
2(H2O)] [Ru(HME)Cl
2(H2O)]
and [Ru(DEE)Cl2(H2O)] induced more efficient cell death
with IC50values of 357plusmn109 488plusmn128 and 343plusmn148 120583M
respectively towards human breast cancer cell (MCF-7) cellsthan other investigated cell lines compared with IC
50values
of 044 plusmn 202 120583M MCF-7 for the standard cytotoxin drugparthenolide
The order of activity of the complexes againsthuman melanoma cancer cell (UACC-62) is asfollows [Ru(DEE)Cl
2(H2O)] gt [Ru(HME)Cl
2(H2O)] gt
[Ru(DAE)Cl2(H2O)] With respect to previous report by
Shier [46] compounds exhibiting IC50activity ranging from
10 to 25 120583M are referred to as weak anticancer drugs whilethose with IC
50action between 5 and 10 120583M are moderate
and the compounds possessing activity less than (lt) 500120583M
Figure 3 In vitro antiproliferative activity of Ru(III) complexes andparthenolide against human melanoma cancer cell (UACC-62)
are considered as strong agents Thus the Ru(III) complexesexhibited a weak to strong activity against the investigatedcancer cell lines with the following order of activity MCF-7 gt UACC-62 gt TK-10 However [Ru(DAE)Cl
2(H2O)]
showed the highest antiproliferative activity with IC50
valves of 357 plusmn 109 644 plusmn 038 and 906 plusmn 118 120583M forMCF-7 UACC-62 and TK-10 respectively The biochemicalactivity could be due to the methoxy alkyl chloride groupsubstituents and bridge spacer ethylenediamine whichcould have played a vital role in antiproliferative potentialsof the Ru(III)-N
2O Schiff base complexes In vitro anticancer
activity of the synthesized Ru(III) complexes in this studywas compared with Ru complexes reported by other authorsand found that [Ru(DAE)Cl
2(H2O)] [Ru(HME)Cl
2(H2O)]
and [Ru(DEE)Cl2(H2O)] complexes exhibited higher
antitumor activities [RuCl(CO)(PPh3)L] reported by Raja et
al [47] against human cervical carcinoma cell line (HeLa)after exposure for 48 h gave an IC
50value in the range of
316 120583M and [RuCl2(AsPh
3)L] with an IC
50value of 378120583M
[48] Raju et al [43] reported ruthenium(III) Schiff basecomplexes of the type [RuX
2(PPh3)2(L)] (where X = Cl or
Bioinorganic Chemistry and Applications 7
020
4060
80
100
00101
1
10
100
ce
ll vi
abili
ty
[Parthenolide][Ru(DAE)Cl2(H2O)]
[Ru(HME)Cl2(H2O)][Ru(DEE)Cl2(H2O)]
Concentration (120583M)
Figure 4 In vitro antiproliferative activity of Ru(III) complexes andparthenolide against human renal cancer cell (TK-10)
Br L = monobasic bidentate ligand) complex to have IC50
value in the range of 452120583M
36 Antioxidant Capacity Different antioxidant techniquesand modifications have been put forward to evaluate antiox-idants reactivity and functionality in foods and biologicalsystems as a means of checkmating variety of patholog-ical activities such as cellular injury and aging processthese damaging occurrences are caused by free radicalsHence two free radicals were used for in vitro antioxi-dants activities of the test samples in this study namely11-diphenyl-2-picrylhydrazyl (DPPH) and 221015840-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS)
361 DPPHRadical Scavenging Assay The activity of antiox-idants on DPPH radical is believed to be centred on theirability to donate hydrogen [22] DPPH has been a stablefree radical with the ability to accept hydrogen radical or anelectron and then become a stable molecule [49]
The mode of rummaging the DPPH radical hasextensively been used to appraise antioxidant activities oftest samples in a moderately short period of time comparedto other procedures [49] The reduction in the DPPH radicalcapability is calculated by the decrease in its absorbanceat 517 nm prompted by antioxidants [50] The reduction ofDPPH radical intensity in this study is due to the interactionof Ru(III) complexes with radical and as such scavengingthe radicals by hydrogen donation (Scheme 2) The DPPHactivities by the Ru(III)-N
2O Schiff base complexes exhibit
strong electron donating power when compared to thestandards ascorbic acid and rutin as displayed in Figure 5The calculated IC
Figure 5 DPPH scavenging potential of Ru(III)-Schiff base com-plexes
coefficient) values of Ru(III) compounds are listed in Table 2Compounds [Ru(DAE)Cl
2(H2O)] [Ru(HME)Cl
2(H2O)]
[Ru(MBE)Cl2(H2O)] and [Ru(DEE)Cl
2(H2O)] with an IC
50
value of 160plusmn068 154plusmn044 163plusmn105 and 151plusmn050 120583Mrespectively exhibited higher activity against DPPH thanthe commercially available Vit C and rutin (standard)however [Ru(DEE)Cl
2(H2O)] showed the highest activity of
all investigated ruthenium(III) samples with an IC50value of
151 plusmn 050 120583MScavenging ability of the test samples on the
DPPH radical can be ranked in the following order[Ru(DEE)Cl
2(H2O)] gt [Ru(HME)Cl
2(H2O)] gt
[Ru(DAE)Cl2(H2O)] gt [Ru(MBE)Cl
2(H2O)] gt [Vit C]
gt [rutin]The scavenging effect of the DAE HME MBE andDEE ligands is lower as compared to their correspondingRu(III) complexes owing to the coordination of the organicmolecules to the Ru3+ ion It is further supported by theobserved discolouration from purple DPPH radical solutionto yellow solution showing scavenging of the DPPH radicalsby hydrogen donation (Scheme 2) Hence these complexescould be effective therapeutic agentrsquos preparation for thetreatment of chronic conditions such as cardiovascularneurodegenerative and arteriosclerosis diseases [21]
362 221015840-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)Radical Scavenging Activity To further confirm the synthe-sized Ru(III)-N
2O Schiff base complexes antiradical poten-
tial we examined the ABTS assay in this study A well-knownprotonated radical like 221015840-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) possesses characteristic absorbancemaxima at 734 nm and decreases with the scavenging of theproton radicals [51]The assaymeasures radical scavenging byelectron donation The outcome of Ru(III)-N
2O Schiff base
complexes alongside the standard drugs on ABTS radical ispresented in Table 2 At 734 nm the absorbance of activeABTSlowast solution noticeably declined upon the addition ofdifferent concentrations of ruthenium(III) samples the sametrend was also observed for the standard drugs butylated
8 Bioinorganic Chemistry and Applications
N N NH+
Cl
Cl
N N
O
HO
HRuCl
Cl
N N
OHRu
+
DPPH radical Reduced DPPH
Antioxidant
OH2 OH2
O2N
O2N
O2N
O2N
NO2
H3C H3C
OCH3 OCH3
OCH3OCH3
NO2
517 nm
O∙
N∙
Scheme 2 Conversion of DPPHlowast (purple) to its corresponding hydrazine form (yellow) by the addition of Ru(III) compounds to DPPHlowastdue to proton transfer
Table 2 Radical scavenging abilities (IC50plusmn SD 120583M) of Ru(III)-Schiff base complexes and standard drugs
Rutinlowast 252 plusmn 160 0798 283 plusmn 184 0983Vit Clowast 192 plusmn 107 0978 mdash mdashBHTlowast mdash mdash 164 plusmn 154 0919119899 = 3119883plusmn SEM IC50 growth inhibitory concentration when the inhibition of the tested compounds was 50 the tested compound concentration was IC501198772 correlation coefficient lowastStandards
hydroxytoluene (BHT) and rutin hydrate with the percentageinhibition displayed in Figure 6
The efficacy of the tested samples in quenching ATBSlowastradicals in the system was observed at 100120583gmL the lowestconcentration and Ru(III) complexes exhibited higher ABTS inhibition than the standards [Ru(DEE)Cl
2(H2O)] com-
plex exhibited the highest ABTS scavenging activity amongstthe studied ruthenium(III) complexes with an IC
50value
of 324 plusmn 093 120583M and 0855 1198772 (correlation coefficient) aslisted in Table 2 while complexes of [Ru(DAE)Cl
2(H2O)]
[Ru(HME)Cl2(H2O)] and [Ru(MBE)Cl
2(H2O)] had an IC
50
value of 330 plusmn 089 427 plusmn 117 and 330 plusmn 148 120583Mrespectively
The ABTS scavenging activity pattern of the complexesis ranked in the following order [Ru(HME)Cl
2(H2O)]
lt [Ru(MBE)Cl2(H2O)] = [Ru(DAE)Cl
2(H2O)] lt
[Ru(DEE)Cl2(H2O)] With this result the antiradical
studies showed that the synthesised Ru(III)-N2O Schiff base
complexes may be useful in developing therapeutic agentfor averting cell oxidative damage and as radicals chainterminator This is because various free radicals generated in
the system often lead to cancer cellular injury aging processand cardiovascular diseases [21]
4 Conclusion
In this study we present the synthesis of Ru(III) Schiff basecomplexes formulated as [Ru(LL)Cl
2(H2O)] (LL = DAE
HME MBE and DEE) The complexes were character-ized using the microanalytical conductance electronic andvibrational spectral analysis FTIR spectral data showed thatthe ligand acts as tridentate chelating ligand coordinatingthrough azomethine nitrogen and phenol oxygen atomThe microanalyses were in conformity with the proposedstructures Conductance measurements showed the com-plexes to be nonelectrolytes in DMF Octahedral structureswere assigned to these complexes based on the elementaland spectral information In vitro antiproliferative studiesof the Ru(III) complexes gave a weak to strong inhibitionagainst the studied cancer cell lines with the followingactivity order MCF-7 gt UACC-62 gt TK-10 Significantly
Figure 6 ABTS rummaging activity of Ru(III)-Schiff base com-plexes
further investigation on the compounds free radical scav-enging properties revealed that Ru(III)-Schiff base complexespossessed considerable antioxidant activities The outcomefrom DPPH and ABTS inhibition studies revealed that thecompounds are proficient in donating electron or hydrogenatom and subsequently terminate the chain reactions ina dose-dependent pattern Scavenging ability of the testsamples on the DPPH radicals can be ranked in the fol-lowing order [Ru(DEE)Cl
2(H2O)]gt [Ru(HME)Cl
2(H2O)]gt
[Ru(DAE)Cl2(H2O)] gt [Ru(MBE)Cl
2(H2O)] Thus Ru(III)-
N2O Schiff base complexes showed stronger inhibition of
DPPH at various concentrations
Competing Interests
No conflict of interests regarding the publication of this paperis declared by the authors
Acknowledgments
The authors acknowledge GovanMbeki Research and Devel-opment Centre (GMRDC) University of Fort Hare forfinancial support and IPE acknowledges National ResearchFoundation and Sasol Inzalo Foundation for the award ofPhD scholarship
References
[1] A Butler and J V Walker ldquoMarine haloperoxidasesrdquo ChemicalReviews vol 93 no 5 pp 1937ndash1944 1993
[2] Y Shechter I Goldwaser M Mironchik M Fridkin and DGefel ldquoHistoric perspective and recent developments on theinsulin-like actions of vanadium toward developing vanadium-based drugs for diabetesrdquo Coordination Chemistry Reviews vol237 no 1-2 pp 3ndash11 2003
[3] A M B Bastos J G da Silva P I S Maia et al ldquoOxo-vanadium(IV) and (V) complexes of acetylpyridine-derivedsemicarbazones exhibit insulin-like activityrdquoPolyhedron vol 27no 6 pp 1787ndash1794 2008
[4] R R Eady ldquoCurrent status of structure function relationshipsof vanadiumnitrogenaserdquoCoordination Chemistry Reviews vol237 no 1-2 pp 23ndash30 2003
[5] K H Thompson J H McNeill and C Orvig ldquoVanadiumcompounds as insulin mimicsrdquo Chemical Reviews vol 99 no9 pp 2561ndash2572 1999
[6] G Grivani G Bruno H A Rudbari A D Khalaji and PPourteimouri ldquoSynthesis characterization and crystal structuredetermination of a new oxovanadium(IV) Schiff base complexthe catalytic activity in the epoxidation of cyclooctenerdquo Inor-ganic Chemistry Communications vol 18 pp 15ndash20 2012
[7] J W Pyrz A L Roe L J Stern and L Que Jr ldquoModel studiesof iron-tyrosinate proteinsrdquo Journal of the American ChemicalSociety vol 107 no 3 pp 614ndash620 1985
[8] M Tumer B Erdogan H Koksal S Serin and M Y NutkuldquoPreparation spectroscopic characterisation and thermal anal-yses studies of theCu(II) Pd(II) andVO(IV) complexes of someSchiff base ligandsrdquo Synthesis and Reactivity in Inorganic andMetal-Organic Chemistry vol 28 no 4 pp 529ndash542 1998
[9] J Hine and C Y Yeh ldquoEquilibrium in formation and conforma-tional isomerization of imines derived from isobutyraldehydeand saturated aliphatic primary aminesrdquo Journal of the Ameri-can Chemical Society vol 89 no 11 pp 2669ndash2676 1967
[10] T Opstal and F Verpoort ldquoSynthesis of highly active rutheniumindenylidene complexes for atom-transfer radical polymer-ization and ring-opening-metathesis polymerizationrdquo Ange-wandte ChemiemdashInternational Edition vol 42 no 25 pp 2876ndash2879 2003
[11] B De Clercq F Lefebvre and F Verpoort ldquoImmobilization ofmultifunctional Schiff base containing ruthenium complexeson MCM-41rdquo Applied Catalysis A General vol 247 no 2 pp345ndash364 2003
[12] A Golcu M Tumer H Demirelli and R A WheatleyldquoCd(II) andCu(II) complexes of polydentate Schiff base ligandssynthesis characterization properties and biological activityrdquoInorganica Chimica Acta vol 358 no 6 pp 1785ndash1797 2005
[13] NMishra K Poonia and D Kumar ldquoAn overview of biologicalaspects of Schiff base metal complexesrdquo International Journal ofAdvancements in ResearchampTechnology vol 2 no 8 pp 52ndash662013
[14] L-A H Allen L S Schlesinger and B Kang ldquoVirulent strainsof Helicobacter pylori demonstrate delayed phagocytosis andstimulate homotypic phagosome fusion in macrophagesrdquo TheJournal of Experimental Medicine vol 191 no 1 pp 115ndash1272000
[15] L A Calderon R C L Teles J R S A Leite C Bloch JrS Astolfi-Filho and S M Freitas ldquoSerine protease inhibitorsfromAmazon Leguminosae seeds purification and preliminarycharacterization of two chymotrypsin inhibitors from Ingaumbraticardquo Protein and Peptide Letters vol 8 no 6 pp 485ndash493 2001
[16] P G Cozzi ldquoMetal-Salen Schiff base complexes in catalysispractical aspectsrdquo Chemical Society Reviews vol 33 no 7 pp410ndash421 2004
[17] T Katsuki ldquoUnique asymmetric catalysis of cis-120573 metal com-plexes of salen and its related Schiff-base ligandsrdquo ChemicalSociety Reviews vol 33 no 7 pp 437ndash444 2004
[18] I M I Fakhr N A Hamdy M A Radwan and Y M AhmedldquoSynthesis of new bioactive benzothiophene derivativesrdquo Egyp-tian Journal of Chemistry vol 47 pp 201ndash215 2004
[19] R A A Ammar and A-N M A Alaghaz ldquoSynthesisspectroscopic characterization and potentiometric studies of
10 Bioinorganic Chemistry and Applications
a tetradentate [N2O2] schiff base NN1015840-bis(2-hydroxyben-
zylidene)-11-diaminoethane and its Co(II)Ni(II)Cu(II) andZn(II) complexesrdquo International Journal of ElectrochemicalScience vol 8 no 6 pp 8686ndash8699 2013
[20] A S Gaballa M S Asker A S Barakat and S M TelebldquoSynthesis characterization and biological activity of someplatinum(II) complexes with Schiff bases derived from salicy-laldehyde 2-furaldehyde and phenylenediaminerdquo Spectrochim-ica Acta Part A Molecular and Biomolecular Spectroscopy vol67 no 1 pp 114ndash121 2007
[21] I P Ejidike and P A Ajibade ldquoTransition metal complexesof symmetrical and asymmetrical Schiff bases as antibacterialantifungal antioxidant and anticancer agents progress andprospectsrdquo Reviews in Inorganic Chemistry vol 35 no 4 pp191ndash224 2015
[22] I P Ejidike and P A Ajibade ldquoSynthesis characterization andin vitro antioxidant and anticancer studies of ruthenium(III)complexes of symmetric and asymmetric tetradentate Schiffbasesrdquo Journal of Coordination Chemistry vol 68 no 14 pp2552ndash2564 2015
[23] N P Priya S Arunachalam A Manimaran D Muthupriyaand C Jayabalakrishnan ldquoMononuclear Ru(III) Schiff basecomplexes synthesis spectral redox catalytic and biologicalactivity studiesrdquo Spectrochimica Acta Part A Molecular andBiomolecular Spectroscopy vol 72 no 3 pp 670ndash676 2009
[24] L Mishra R Prajapati and K K Pandey ldquoMixed-ligand Ru(II)complexes with 221015840-bipyridine and tetradentate Schiff basesauxiliary ligands Synthesis physico-chemical study DFT anal-ysis electrochemical and Na+ binding propertiesrdquo Spectrochim-ica ActamdashPart A Molecular and Biomolecular Spectroscopy vol70 no 1 pp 79ndash85 2008
[25] G Venkatachalam and R Ramesh ldquoCatalytic and biologicalactivities of Ru(III) mixed ligand complexes containing NOdonor of 2-hydroxy-1-naphthylideneiminesrdquo SpectrochimicaActa Part A Molecular and Biomolecular Spectroscopy vol 61no 9 pp 2081ndash2087 2005
[26] I P Ejidike and P A Ajibade ldquoSynthesis and in vitro anti-cancer antibacterial and antioxidant studies of unsymmet-rical Schiff base derivatives of 4-[(1E)-N-(2-aminoethyl)eth-animidoyl]benzene-13-diolrdquo Research on Chemical Intermedi-ates vol 42 no 8 pp 6543ndash6555 2016
[27] K I Ansari I Hussain H K Das and S S Mandal ldquoOver-expression of human histone methylase MLL1 upon exposureto a food contaminant mycotoxin deoxynivalenolrdquo The FEBSJournal vol 276 no 12 pp 3299ndash3307 2009
[28] I P Ejidike and P A Ajibade ldquoSynthesis characterization andbiological studies of metal(II) complexes of (3E)-3-[(2-(119864)-[1-(24-Dihydroxyphenyl) ethylidene]aminoethyl)imino]-1-phenylbutan-1-one schiff baserdquo Molecules vol 20 no 6 pp9788ndash9802 2015
[29] C A Bolos A T Chaviara D Mourelatos et al ldquoSynthesischaracterization toxicity cytogenetic and in vivo antitumorstudies of 11-dithiolate Cu(II) complexes with di- tri- tetra-amines and 13-thiazoles Structure-activity correlationrdquo Bioor-ganic amp Medicinal Chemistry vol 17 no 8 pp 3142ndash3151 2009
[30] P K Das N Panda and N K Behera ldquoSynthesis character-ization and antimicrobial activities of Schiff base complexesderived from isoniazid and diacetylmonoximerdquo InternationalJournal of Innovative Science Engineering amp Technology vol 3no 1 pp 42ndash54 2016
[31] L Mitu M Ilis N Raman M Imran and S RavichandranldquoTransition metal complexes of isonicotinoylndashhydrazone-4-diphenylaminobenzaldehyde synthesis characterization andantimicrobial studiesrdquo E-Journal of Chemistry vol 9 no 1 pp365ndash372 2012
[32] S A Ali A A Soliman M M Aboaly and R M RamadanldquoChromium molybdenum and ruthenium complexes of 2-hydroxyacetophenone schiff basesrdquo Journal of CoordinationChemistry vol 55 no 10 pp 1161ndash1170 2002
[33] K N Kumar R Ramesh and Y Liu ldquoSynthesis structureand catalytic activity of cycloruthenated carbonyl complexescontaining arylazo phenolate ligandsrdquo Journal of MolecularCatalysis A Chemical vol 265 no 1-2 pp 218ndash226 2007
[34] I P Ejidike and P A Ajibade ldquoSynthesis characterizationantioxidant and antibacterial studies of some metal(II)complexes of tetradentate schiff base ligand (4E)-4-[(2-(119864)-[1-(24-dihydroxyphenyl)ethylidene]aminoethyl)imino]pentan-2-onerdquo Bioinorganic Chemistry and Applications vol 2015Article ID 890734 9 pages 2015
[35] J S Casas A Castineiras F Condori et al ldquoDiorganotin(IV)-promoted deamination of amino acids by pyridoxal SnR2
2+
complexes of pyridoxal 51015840-phosphate and of the Schiff basepyridoxal-pyridoxamine (PLPM) and antibacterial activities ofPLPM and [SnR
2(PLPM-2H)] (R=Me Et Bu Ph)rdquo Polyhedron
vol 22 no 1 pp 53ndash65 2003[36] P J K Inba B Annaraj S Thalamuthu and M A Nee-
lakantan ldquoCu(II) Ni(II) and Zn(II) complexes of salan-typeligand containing ester groups synthesis characterizationelectrochemical properties and in vitro biological activitiesrdquoBioinorganic Chemistry and Applications vol 2013 Article ID439848 11 pages 2013
[37] K Shanker R Rohini V Ravinder P M Reddy and Y-P HoldquoRu(II) complexes of N
4and N
2O2macrocyclic Schiff base lig-
ands their antibacterial and antifungal studiesrdquo SpectrochimicaActa Part A Molecular and Biomolecular Spectroscopy vol 73no 1 pp 205ndash211 2009
[38] M Alias H Kassum and C Shakir ldquoSynthesis physicalcharacterization and biological evaluation of Schiff base M(II)complexesrdquo Journal of the Association of Arab Universities forBasic and Applied Sciences vol 15 no 1 pp 28ndash34 2014
[39] K Shivakumar Shashidhar P V Reddy and M B HallildquoSynthesis spectral characterization and biological activity ofbenzofuran Schiff bases with Co(II) Ni(II) Cu(II) Zn(II)Cd(II) and Hg(II) complexesrdquo Journal of Coordination Chem-istry vol 61 no 14 pp 2274ndash2287 2008
[40] T D Thangadurai and S-K Ihm ldquoNovel bidentate ruthe-nium(III) Schiff base complexes synthetic spectral electro-chemical catalytic and antimicrobial studiesrdquo Transition MetalChemistry vol 29 no 2 pp 189ndash195 2004
[41] C J Ballhausen Introduction to Ligand Field Theory McGarwHill New York NY USA 1962
[42] A B P Lever Inorganic Electronic Spectroscopy Elsevier NewYork NY USA 2nd edition 1984
[43] V V Raju K P Balasubramanian C Jayabalakrishnan and VChinnusamy ldquoSynthesis characterization antimicrobial activ-ities and DNA-Binding studies of some Ru(III) complexesof Schiff basesrdquo International Journal of Applied Biology andPharmaceutical Technology vol 3 no 2 pp 76ndash87 2012
[44] K P Balasubramanian K Parameswari V Chinnusamy RPrabhakaran and K Natarajan ldquoSynthesis characterizationelectro chemistry catalytic and biological activities of ruthe-nium(III) complexes with bidentate N OS donor ligandsrdquo
Bioinorganic Chemistry and Applications 11
Spectrochimica ActamdashPart A Molecular and Biomolecular Spec-troscopy vol 65 no 3-4 pp 678ndash683 2006
[45] A Ghantous M Saikali T Rau H Gali-Muhtasib RSchneider-Stock and N Darwiche ldquoInhibition of tumor pro-motion by parthenolide epigenetic modulation of p21rdquo CancerPrevention Research vol 5 no 11 pp 1298ndash1309 2012
[46] W T ShierMammalian Cell Culture on $5 aDay A LabManualof Low Cost Methods University of the Philippines Los BanosCalif USA 1991
[47] G Raja R J Butcher and C Jayabalakrishnan ldquoStudies onsynthesis characterization DNA interaction and cytotoxicity ofruthenium(II) Schiff base complexesrdquo Spectrochimica Acta PartA Molecular and Biomolecular Spectroscopy vol 94 pp 210ndash215 2012
[48] G Raja R J Butcher and C Jayabalakrishnan ldquoSynthesischaracterization DNA binding and cleavage properties andanticancer studies of ruthenium(III) Schiff base complexesrdquoTransition Metal Chemistry vol 37 no 2 pp 169ndash174 2012
[49] I Gulcin O I Kufrevioglu M Oktay and M EBuyukokuroglu ldquoAntioxidant antimicrobial antiulcer andanalgesic activities of nettle (Urtica dioica L)rdquo Journal of Ethno-pharmacology vol 90 no 2-3 pp 205ndash215 2004
[50] M Viuda-Martos Y R Navajas E S Zapata J Fernandez-Lopez and J A Perez-Alvarez ldquoAntioxidant activity of essentialoils of five spice plants widely used in a Mediterranean dietrdquoFlavour and Fragrance Journal vol 25 no 1 pp 13ndash19 2010
[51] S Mathew and T E Abraham ldquoIn vitro antioxidant activity andscavenging effects of Cinnamomum verum leaf extract assayedby different methodologiesrdquo Food and Chemical Toxicology vol44 no 2 pp 198ndash206 2006
when reacted with antioxidant species changes to an equiv-alent light yellow colour The radical scavenging potentialsof the complexes with DPPH radical were evaluated asdescribed [22] 1mL solution of the compounds in DMFwithconcentrations ranging from 100 to 500120583gmL was mixedthoroughly with equivalent amount of 04mM DPPH inmethanol themixtures were then allowed to react in the darkfor half an hour Measurement of the mixture absorbancewas achieved spectrophotometrically at 517 nm Vitamin Cand rutin were used as the standard drugs All test analysiswas carried out in triplicate The ability of the rutheniumcompounds to scavenge DPPH radical was calculated via thefollowing equation
DPPH radical scavenging activity ()
=Absorbance of control minus Absorbance of sample
Absorbance of control
times 100
(1)
252 ABTS 221015840-Azino-bis(3-ethylbenzothiazoline-6-sulfonicacid) Radical Scavenging Assay ABTS scavenging abilityof the Ru(III)-tridentate Schiff base complexes adopted adescribed method [28] 7mM ABTS solution and 24mMpotassium persulfate solution in equal amounts (1 1) wereused for working solution preparation and allowed to reactin the dark for 12 h at room temperature An absorbanceof 0706 plusmn 0001 units at 734 nm required for the analysiswas obtained by diluting 1mL ABTS+ solution Test samples(1mL) were mixed with 1mL of the ABTS+ solution andabsorbance was read spectrophotometrically at 734 nm Thetest samplesrsquo ABTS scavenging capacity alongside standarddrugs was evaluated Triplicate analysis was carried out Thepercentage inhibition ofABTS radical scavenging activitywasobtained following a previous report [28]
3 Results and Discussion
31 Synthesis and Characterization The obtained com-pounds were of coloured powders stable in atmospherewith a general formula [Ru(LL)Cl
2(H2O)] (LL = monobasic
tridentate Schiff base anion DAE HME MBE and DEE)They were prepared by treating [RuCl
3sdot3H2O] with the
corresponding Schiff base in an equal mole ratio in alcoholas depicted in the Scheme 1 All the complexes are dark-green and sparingly soluble in general organic solvents butsoluble in polar aprotic solvent such as DMF and DMSOthe melting point analysis showed that the Ru(III) complexeswere decomposing before melting The physicoanalyticaldata collected for the compounds are in agreement withthe structural formulae proposed thus confirming the sug-gested mononuclear composition for the Ru(III) complexes(Scheme 1)
32 Molar Conductivity Measurements The molar conduc-tance of the synthesized Ru(III) complexes was measuredin DMF at 10minus3M solution The values were found to be in
the range of 301ndash388 120583Scmminus1 suggesting the nonelectrolyticnature of the complexes in solution [22 29]
33 Infrared Spectra Valuable evidence concerning the envi-ronment of the functional group attached to the rutheniumatom has been obtained from the FTIR spectra The IRspectra of the ligands when compared with those of thenewly synthesized complexes confirm the coordination ofN2O type tridentate ligands to the ruthenium ion The
classification was achieved by comparing the spectra of theligandswith those originating from the coordination betweenruthenium(III) metal ion and the active sites The Schiffbases showed the broad bands in the 3462ndash3477 cmminus1 rangeattributable to the ](OH) cmminus1 vibration Ligand infraredspectra showed that a band at 1605ndash1619 cmminus1 is attributed to](C=N) stretching of the azomethine group based on earlierreports [30] This ](C=N) shift to 1617ndash1639 cmminus1 in all thecomplexes by about 5ndash23 cmminus1 signifies the participation ofazomethine nitrogen in the coordination sphere with theruthenium(III) ion for all the complexes [21 31] A mediumband that corresponds to phenolic oxygen atom ](C-O) isobserved at 1167 and 1245 cmminus1 for the free ligands
The higher shifting of ](C-O) stretching vibrations asobserved in the ruthenium(III) complexes spectra suggeststhat the phenolic OH group of Schiff base DAE HMEMBE and DEE is involved in coordination with rutheniumion after deprotonation [32 33] Seemingly the DAE HMEMBE and DEE ligands act as a tridentate chelating com-pound coordinating to the metal ion via the two nitrogenatoms of the azomethine group as well as O atom of phenolicgroup [21 25] This is further supported by the displacementof ](O-H) in the range 3462ndash3477 cmminus1 in all the complexesThe presence of coordinated water gave a broad band thatappeared in the regions 3416ndash3436 and 813ndash851 cmminus1 this canbe due to ](O-H) stretching and ](O-H) rocking vibrationsrespectively which further confirms the presence of nonli-gand assignable to the rocking mode of water [28 34] Newweak nonligand bands that are not found in the DAE HMEMBE and DEE ligands appeared in the ranges 475ndash548 cmminus1and 436ndash475 cmminus1 in the complexes spectra attributed to](Ru-N) and ](Ru-O) vibrations respectively [35 36] A bandranging from 311ndash346 cmminus1 appeared in the spectra of theRu(III)-Schiff base complexes indicating the presence of twochloride ions in trans position around ruthenium centre [37ndash40]
34 Electronic Absorption Spectra Studies The UV-Vis spec-tra of the Ru(III)-Schiff base complexes in DMF solutionswere recorded at room temperature ranging from 200 to900 nm The nature of DAE HME MBE and DEE ligandsfield around the ruthenium ion was obtained from theelectronic spectra The free ligands showed absorption bandswithin the range of 277ndash393 nm attributable to 120587lowast larr 120587 and120587lowastlarr 119899 transitions relating the benzene ring (Figure 1) The
shifting of these bands in the complexes spectra followed theparticipation of the imine group nitrogen and phenolic groupoxygen in bonding [22 25] Ground state of ruthenium(III) is2T2g where initial excited doublet levels in order of increasing
Bioinorganic Chemistry and Applications 5
0
02
04
06
08
1
12
14
16
260 320 380 440 500 560 620 680
Abso
rban
ce (a
u)
Wavelength (nm)
(a)
0
02
04
06
08
1
12
14
16
18
260 320 380 440 500 560 620 680
Abso
rban
ce (a
u)
Wavelength (nm)
(b)
0
02
04
06
08
1
12
14
260 320 380 440 500 560 620 680
Abso
rban
ce (a
u)
Wavelength (nm)
(c)
0
01
02
03
04
260 320 380 440 500 560 620 680
Abso
rban
ce (a
u)
Wavelength (nm)
(d)
Figure 1 Electronic absorption spectra of the Ru(III) complexes (a) [Ru(DAE)Cl2(H2O)] (b) [Ru(HME)Cl
2(H2O)] (c)
[Ru(MBE)Cl2(H2O)] (d) [Ru(DEE)Cl
2(H2O)]
energy are 2A2g and 2T
1g arising from t42ge1
g configuration[41]
Ru3+ ion with a d5 electronic configuration possesseshigh oxidizing properties and large crystal field parameterAlso charge transfer bands of the type L
120587y rarr T2g were
noticeable within low energy region obscuring weaker bandsthat is due to d-d transitions [22 25] The extinction coef-ficient bands around 613ndash632 nm regions are found to below when compared to the charge transfer bands Thesebands have been assigned to 2T
2g rarr2A2g transition and
are in agreement with the assignment made for similaroctahedral ruthenium(III) complexes [42 43] Absorptionbands within the 452ndash525 nm regions were assigned to thecharge transfer transitions [22 44] Overall the absorptionspectra of the Ru(III)-Schiff base complexes are typical ofoctahedral environment about the ruthenium(III) ions [22]
35 Antiproliferative Activity Investigation into the struc-ture-activity relationship of the isolated Ru(III)-N
2O Schiff
base complexes with respect to different functional groups
on the ligands used for ruthenium ion complex formationhas been conducted via antiproliferative studies Three of theRu(III)-Schiff base compounds alongside parthenolide weresubjected to cell lines tests at different sample concentrationsranging from 001 to 100120583M towards renal cancer cell (TK-10) melanoma cancer cell (UACC-62) and breast cancercell (MCF-7) The cancer cell lines were incubated for 48 hfollowed by the addition of the compounds of variousconcentrations via Sulforhodamine B (SRB) assay [22]
The ruthenium(III) compounds and standard drug(parthenolide) IC
50values are presented in Table 1 and
revealed that the test samples showed significant inhibitionagainst the tested cell lines Figures 2ndash4 represent the cellviability percentages of ruthenium(III)-Schiff base complexesand parthenolide drug against TK-10 UACC-62 and MCF-7 cell lines at different concentrations of ruthenium(III)compounds or parthenolide A high level of antiprolifera-tive potentials against the studied cell lines was exhibitedby parthenolide in accordance with earlier reports [45]The obtained results revealed that treatment of cell lines with
6 Bioinorganic Chemistry and Applications
Table 1 In vitro antiproliferative studies of Ru(III)-Schiff base complexes against TK-10 UACC-62 and MCF-7 cell lines
Compounds Molecular formula Anticancer activity IC50(120583M) 48 h
TK-10 UACC-62 MCF-7[Ru(DAE)Cl
2(H2O)] C
18H24N3O4RuCl2
906 plusmn 118 644 plusmn 038 357 plusmn 109
[Ru(HME)Cl2(H2O)] C
18H23N2O6RuCl2
4109 plusmn 444 631 plusmn 147 488 plusmn 128
[Ru(DEE)Cl2(H2O)] C
17H20N2O4RuCl3
1310 plusmn 281 514 plusmn 109 343 plusmn 148
Parthenolidelowast C15H20O3
050 plusmn 143 089 plusmn 218 044 plusmn 202lowastStandard cytotoxin drug cell lines were treated with different concentrations of the compounds to achieve 50 inhibition of the culture growth when culturedfor 48 h Value represents mean plusmn SD of three independent experimentations
Figure 2 In vitro antiproliferative activity of Ru(III) complexes andparthenolide against human breast cancer cell line (MCF-7)
different concentrations of Ru(III)-Schiff base complexes effi-ciently affected cell viability towardsMCF-7 cells as displayedin Figures 2ndash4 and Table 1 The Ru(III) compounds exhibitedlow to strong in vitro antiproliferative activities againstthe selected cell lines as compared to the standard drug(parthenolide) [Ru(DAE)Cl
2(H2O)] [Ru(HME)Cl
2(H2O)]
and [Ru(DEE)Cl2(H2O)] induced more efficient cell death
with IC50values of 357plusmn109 488plusmn128 and 343plusmn148 120583M
respectively towards human breast cancer cell (MCF-7) cellsthan other investigated cell lines compared with IC
50values
of 044 plusmn 202 120583M MCF-7 for the standard cytotoxin drugparthenolide
The order of activity of the complexes againsthuman melanoma cancer cell (UACC-62) is asfollows [Ru(DEE)Cl
2(H2O)] gt [Ru(HME)Cl
2(H2O)] gt
[Ru(DAE)Cl2(H2O)] With respect to previous report by
Shier [46] compounds exhibiting IC50activity ranging from
10 to 25 120583M are referred to as weak anticancer drugs whilethose with IC
50action between 5 and 10 120583M are moderate
and the compounds possessing activity less than (lt) 500120583M
Figure 3 In vitro antiproliferative activity of Ru(III) complexes andparthenolide against human melanoma cancer cell (UACC-62)
are considered as strong agents Thus the Ru(III) complexesexhibited a weak to strong activity against the investigatedcancer cell lines with the following order of activity MCF-7 gt UACC-62 gt TK-10 However [Ru(DAE)Cl
2(H2O)]
showed the highest antiproliferative activity with IC50
valves of 357 plusmn 109 644 plusmn 038 and 906 plusmn 118 120583M forMCF-7 UACC-62 and TK-10 respectively The biochemicalactivity could be due to the methoxy alkyl chloride groupsubstituents and bridge spacer ethylenediamine whichcould have played a vital role in antiproliferative potentialsof the Ru(III)-N
2O Schiff base complexes In vitro anticancer
activity of the synthesized Ru(III) complexes in this studywas compared with Ru complexes reported by other authorsand found that [Ru(DAE)Cl
2(H2O)] [Ru(HME)Cl
2(H2O)]
and [Ru(DEE)Cl2(H2O)] complexes exhibited higher
antitumor activities [RuCl(CO)(PPh3)L] reported by Raja et
al [47] against human cervical carcinoma cell line (HeLa)after exposure for 48 h gave an IC
50value in the range of
316 120583M and [RuCl2(AsPh
3)L] with an IC
50value of 378120583M
[48] Raju et al [43] reported ruthenium(III) Schiff basecomplexes of the type [RuX
2(PPh3)2(L)] (where X = Cl or
Bioinorganic Chemistry and Applications 7
020
4060
80
100
00101
1
10
100
ce
ll vi
abili
ty
[Parthenolide][Ru(DAE)Cl2(H2O)]
[Ru(HME)Cl2(H2O)][Ru(DEE)Cl2(H2O)]
Concentration (120583M)
Figure 4 In vitro antiproliferative activity of Ru(III) complexes andparthenolide against human renal cancer cell (TK-10)
Br L = monobasic bidentate ligand) complex to have IC50
value in the range of 452120583M
36 Antioxidant Capacity Different antioxidant techniquesand modifications have been put forward to evaluate antiox-idants reactivity and functionality in foods and biologicalsystems as a means of checkmating variety of patholog-ical activities such as cellular injury and aging processthese damaging occurrences are caused by free radicalsHence two free radicals were used for in vitro antioxi-dants activities of the test samples in this study namely11-diphenyl-2-picrylhydrazyl (DPPH) and 221015840-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS)
361 DPPHRadical Scavenging Assay The activity of antiox-idants on DPPH radical is believed to be centred on theirability to donate hydrogen [22] DPPH has been a stablefree radical with the ability to accept hydrogen radical or anelectron and then become a stable molecule [49]
The mode of rummaging the DPPH radical hasextensively been used to appraise antioxidant activities oftest samples in a moderately short period of time comparedto other procedures [49] The reduction in the DPPH radicalcapability is calculated by the decrease in its absorbanceat 517 nm prompted by antioxidants [50] The reduction ofDPPH radical intensity in this study is due to the interactionof Ru(III) complexes with radical and as such scavengingthe radicals by hydrogen donation (Scheme 2) The DPPHactivities by the Ru(III)-N
2O Schiff base complexes exhibit
strong electron donating power when compared to thestandards ascorbic acid and rutin as displayed in Figure 5The calculated IC
Figure 5 DPPH scavenging potential of Ru(III)-Schiff base com-plexes
coefficient) values of Ru(III) compounds are listed in Table 2Compounds [Ru(DAE)Cl
2(H2O)] [Ru(HME)Cl
2(H2O)]
[Ru(MBE)Cl2(H2O)] and [Ru(DEE)Cl
2(H2O)] with an IC
50
value of 160plusmn068 154plusmn044 163plusmn105 and 151plusmn050 120583Mrespectively exhibited higher activity against DPPH thanthe commercially available Vit C and rutin (standard)however [Ru(DEE)Cl
2(H2O)] showed the highest activity of
all investigated ruthenium(III) samples with an IC50value of
151 plusmn 050 120583MScavenging ability of the test samples on the
DPPH radical can be ranked in the following order[Ru(DEE)Cl
2(H2O)] gt [Ru(HME)Cl
2(H2O)] gt
[Ru(DAE)Cl2(H2O)] gt [Ru(MBE)Cl
2(H2O)] gt [Vit C]
gt [rutin]The scavenging effect of the DAE HME MBE andDEE ligands is lower as compared to their correspondingRu(III) complexes owing to the coordination of the organicmolecules to the Ru3+ ion It is further supported by theobserved discolouration from purple DPPH radical solutionto yellow solution showing scavenging of the DPPH radicalsby hydrogen donation (Scheme 2) Hence these complexescould be effective therapeutic agentrsquos preparation for thetreatment of chronic conditions such as cardiovascularneurodegenerative and arteriosclerosis diseases [21]
362 221015840-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)Radical Scavenging Activity To further confirm the synthe-sized Ru(III)-N
2O Schiff base complexes antiradical poten-
tial we examined the ABTS assay in this study A well-knownprotonated radical like 221015840-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) possesses characteristic absorbancemaxima at 734 nm and decreases with the scavenging of theproton radicals [51]The assaymeasures radical scavenging byelectron donation The outcome of Ru(III)-N
2O Schiff base
complexes alongside the standard drugs on ABTS radical ispresented in Table 2 At 734 nm the absorbance of activeABTSlowast solution noticeably declined upon the addition ofdifferent concentrations of ruthenium(III) samples the sametrend was also observed for the standard drugs butylated
8 Bioinorganic Chemistry and Applications
N N NH+
Cl
Cl
N N
O
HO
HRuCl
Cl
N N
OHRu
+
DPPH radical Reduced DPPH
Antioxidant
OH2 OH2
O2N
O2N
O2N
O2N
NO2
H3C H3C
OCH3 OCH3
OCH3OCH3
NO2
517 nm
O∙
N∙
Scheme 2 Conversion of DPPHlowast (purple) to its corresponding hydrazine form (yellow) by the addition of Ru(III) compounds to DPPHlowastdue to proton transfer
Table 2 Radical scavenging abilities (IC50plusmn SD 120583M) of Ru(III)-Schiff base complexes and standard drugs
Rutinlowast 252 plusmn 160 0798 283 plusmn 184 0983Vit Clowast 192 plusmn 107 0978 mdash mdashBHTlowast mdash mdash 164 plusmn 154 0919119899 = 3119883plusmn SEM IC50 growth inhibitory concentration when the inhibition of the tested compounds was 50 the tested compound concentration was IC501198772 correlation coefficient lowastStandards
hydroxytoluene (BHT) and rutin hydrate with the percentageinhibition displayed in Figure 6
The efficacy of the tested samples in quenching ATBSlowastradicals in the system was observed at 100120583gmL the lowestconcentration and Ru(III) complexes exhibited higher ABTS inhibition than the standards [Ru(DEE)Cl
2(H2O)] com-
plex exhibited the highest ABTS scavenging activity amongstthe studied ruthenium(III) complexes with an IC
50value
of 324 plusmn 093 120583M and 0855 1198772 (correlation coefficient) aslisted in Table 2 while complexes of [Ru(DAE)Cl
2(H2O)]
[Ru(HME)Cl2(H2O)] and [Ru(MBE)Cl
2(H2O)] had an IC
50
value of 330 plusmn 089 427 plusmn 117 and 330 plusmn 148 120583Mrespectively
The ABTS scavenging activity pattern of the complexesis ranked in the following order [Ru(HME)Cl
2(H2O)]
lt [Ru(MBE)Cl2(H2O)] = [Ru(DAE)Cl
2(H2O)] lt
[Ru(DEE)Cl2(H2O)] With this result the antiradical
studies showed that the synthesised Ru(III)-N2O Schiff base
complexes may be useful in developing therapeutic agentfor averting cell oxidative damage and as radicals chainterminator This is because various free radicals generated in
the system often lead to cancer cellular injury aging processand cardiovascular diseases [21]
4 Conclusion
In this study we present the synthesis of Ru(III) Schiff basecomplexes formulated as [Ru(LL)Cl
2(H2O)] (LL = DAE
HME MBE and DEE) The complexes were character-ized using the microanalytical conductance electronic andvibrational spectral analysis FTIR spectral data showed thatthe ligand acts as tridentate chelating ligand coordinatingthrough azomethine nitrogen and phenol oxygen atomThe microanalyses were in conformity with the proposedstructures Conductance measurements showed the com-plexes to be nonelectrolytes in DMF Octahedral structureswere assigned to these complexes based on the elementaland spectral information In vitro antiproliferative studiesof the Ru(III) complexes gave a weak to strong inhibitionagainst the studied cancer cell lines with the followingactivity order MCF-7 gt UACC-62 gt TK-10 Significantly
Figure 6 ABTS rummaging activity of Ru(III)-Schiff base com-plexes
further investigation on the compounds free radical scav-enging properties revealed that Ru(III)-Schiff base complexespossessed considerable antioxidant activities The outcomefrom DPPH and ABTS inhibition studies revealed that thecompounds are proficient in donating electron or hydrogenatom and subsequently terminate the chain reactions ina dose-dependent pattern Scavenging ability of the testsamples on the DPPH radicals can be ranked in the fol-lowing order [Ru(DEE)Cl
2(H2O)]gt [Ru(HME)Cl
2(H2O)]gt
[Ru(DAE)Cl2(H2O)] gt [Ru(MBE)Cl
2(H2O)] Thus Ru(III)-
N2O Schiff base complexes showed stronger inhibition of
DPPH at various concentrations
Competing Interests
No conflict of interests regarding the publication of this paperis declared by the authors
Acknowledgments
The authors acknowledge GovanMbeki Research and Devel-opment Centre (GMRDC) University of Fort Hare forfinancial support and IPE acknowledges National ResearchFoundation and Sasol Inzalo Foundation for the award ofPhD scholarship
References
[1] A Butler and J V Walker ldquoMarine haloperoxidasesrdquo ChemicalReviews vol 93 no 5 pp 1937ndash1944 1993
[2] Y Shechter I Goldwaser M Mironchik M Fridkin and DGefel ldquoHistoric perspective and recent developments on theinsulin-like actions of vanadium toward developing vanadium-based drugs for diabetesrdquo Coordination Chemistry Reviews vol237 no 1-2 pp 3ndash11 2003
[3] A M B Bastos J G da Silva P I S Maia et al ldquoOxo-vanadium(IV) and (V) complexes of acetylpyridine-derivedsemicarbazones exhibit insulin-like activityrdquoPolyhedron vol 27no 6 pp 1787ndash1794 2008
[4] R R Eady ldquoCurrent status of structure function relationshipsof vanadiumnitrogenaserdquoCoordination Chemistry Reviews vol237 no 1-2 pp 23ndash30 2003
[5] K H Thompson J H McNeill and C Orvig ldquoVanadiumcompounds as insulin mimicsrdquo Chemical Reviews vol 99 no9 pp 2561ndash2572 1999
[6] G Grivani G Bruno H A Rudbari A D Khalaji and PPourteimouri ldquoSynthesis characterization and crystal structuredetermination of a new oxovanadium(IV) Schiff base complexthe catalytic activity in the epoxidation of cyclooctenerdquo Inor-ganic Chemistry Communications vol 18 pp 15ndash20 2012
[7] J W Pyrz A L Roe L J Stern and L Que Jr ldquoModel studiesof iron-tyrosinate proteinsrdquo Journal of the American ChemicalSociety vol 107 no 3 pp 614ndash620 1985
[8] M Tumer B Erdogan H Koksal S Serin and M Y NutkuldquoPreparation spectroscopic characterisation and thermal anal-yses studies of theCu(II) Pd(II) andVO(IV) complexes of someSchiff base ligandsrdquo Synthesis and Reactivity in Inorganic andMetal-Organic Chemistry vol 28 no 4 pp 529ndash542 1998
[9] J Hine and C Y Yeh ldquoEquilibrium in formation and conforma-tional isomerization of imines derived from isobutyraldehydeand saturated aliphatic primary aminesrdquo Journal of the Ameri-can Chemical Society vol 89 no 11 pp 2669ndash2676 1967
[10] T Opstal and F Verpoort ldquoSynthesis of highly active rutheniumindenylidene complexes for atom-transfer radical polymer-ization and ring-opening-metathesis polymerizationrdquo Ange-wandte ChemiemdashInternational Edition vol 42 no 25 pp 2876ndash2879 2003
[11] B De Clercq F Lefebvre and F Verpoort ldquoImmobilization ofmultifunctional Schiff base containing ruthenium complexeson MCM-41rdquo Applied Catalysis A General vol 247 no 2 pp345ndash364 2003
[12] A Golcu M Tumer H Demirelli and R A WheatleyldquoCd(II) andCu(II) complexes of polydentate Schiff base ligandssynthesis characterization properties and biological activityrdquoInorganica Chimica Acta vol 358 no 6 pp 1785ndash1797 2005
[13] NMishra K Poonia and D Kumar ldquoAn overview of biologicalaspects of Schiff base metal complexesrdquo International Journal ofAdvancements in ResearchampTechnology vol 2 no 8 pp 52ndash662013
[14] L-A H Allen L S Schlesinger and B Kang ldquoVirulent strainsof Helicobacter pylori demonstrate delayed phagocytosis andstimulate homotypic phagosome fusion in macrophagesrdquo TheJournal of Experimental Medicine vol 191 no 1 pp 115ndash1272000
[15] L A Calderon R C L Teles J R S A Leite C Bloch JrS Astolfi-Filho and S M Freitas ldquoSerine protease inhibitorsfromAmazon Leguminosae seeds purification and preliminarycharacterization of two chymotrypsin inhibitors from Ingaumbraticardquo Protein and Peptide Letters vol 8 no 6 pp 485ndash493 2001
[16] P G Cozzi ldquoMetal-Salen Schiff base complexes in catalysispractical aspectsrdquo Chemical Society Reviews vol 33 no 7 pp410ndash421 2004
[17] T Katsuki ldquoUnique asymmetric catalysis of cis-120573 metal com-plexes of salen and its related Schiff-base ligandsrdquo ChemicalSociety Reviews vol 33 no 7 pp 437ndash444 2004
[18] I M I Fakhr N A Hamdy M A Radwan and Y M AhmedldquoSynthesis of new bioactive benzothiophene derivativesrdquo Egyp-tian Journal of Chemistry vol 47 pp 201ndash215 2004
[19] R A A Ammar and A-N M A Alaghaz ldquoSynthesisspectroscopic characterization and potentiometric studies of
10 Bioinorganic Chemistry and Applications
a tetradentate [N2O2] schiff base NN1015840-bis(2-hydroxyben-
zylidene)-11-diaminoethane and its Co(II)Ni(II)Cu(II) andZn(II) complexesrdquo International Journal of ElectrochemicalScience vol 8 no 6 pp 8686ndash8699 2013
[20] A S Gaballa M S Asker A S Barakat and S M TelebldquoSynthesis characterization and biological activity of someplatinum(II) complexes with Schiff bases derived from salicy-laldehyde 2-furaldehyde and phenylenediaminerdquo Spectrochim-ica Acta Part A Molecular and Biomolecular Spectroscopy vol67 no 1 pp 114ndash121 2007
[21] I P Ejidike and P A Ajibade ldquoTransition metal complexesof symmetrical and asymmetrical Schiff bases as antibacterialantifungal antioxidant and anticancer agents progress andprospectsrdquo Reviews in Inorganic Chemistry vol 35 no 4 pp191ndash224 2015
[22] I P Ejidike and P A Ajibade ldquoSynthesis characterization andin vitro antioxidant and anticancer studies of ruthenium(III)complexes of symmetric and asymmetric tetradentate Schiffbasesrdquo Journal of Coordination Chemistry vol 68 no 14 pp2552ndash2564 2015
[23] N P Priya S Arunachalam A Manimaran D Muthupriyaand C Jayabalakrishnan ldquoMononuclear Ru(III) Schiff basecomplexes synthesis spectral redox catalytic and biologicalactivity studiesrdquo Spectrochimica Acta Part A Molecular andBiomolecular Spectroscopy vol 72 no 3 pp 670ndash676 2009
[24] L Mishra R Prajapati and K K Pandey ldquoMixed-ligand Ru(II)complexes with 221015840-bipyridine and tetradentate Schiff basesauxiliary ligands Synthesis physico-chemical study DFT anal-ysis electrochemical and Na+ binding propertiesrdquo Spectrochim-ica ActamdashPart A Molecular and Biomolecular Spectroscopy vol70 no 1 pp 79ndash85 2008
[25] G Venkatachalam and R Ramesh ldquoCatalytic and biologicalactivities of Ru(III) mixed ligand complexes containing NOdonor of 2-hydroxy-1-naphthylideneiminesrdquo SpectrochimicaActa Part A Molecular and Biomolecular Spectroscopy vol 61no 9 pp 2081ndash2087 2005
[26] I P Ejidike and P A Ajibade ldquoSynthesis and in vitro anti-cancer antibacterial and antioxidant studies of unsymmet-rical Schiff base derivatives of 4-[(1E)-N-(2-aminoethyl)eth-animidoyl]benzene-13-diolrdquo Research on Chemical Intermedi-ates vol 42 no 8 pp 6543ndash6555 2016
[27] K I Ansari I Hussain H K Das and S S Mandal ldquoOver-expression of human histone methylase MLL1 upon exposureto a food contaminant mycotoxin deoxynivalenolrdquo The FEBSJournal vol 276 no 12 pp 3299ndash3307 2009
[28] I P Ejidike and P A Ajibade ldquoSynthesis characterization andbiological studies of metal(II) complexes of (3E)-3-[(2-(119864)-[1-(24-Dihydroxyphenyl) ethylidene]aminoethyl)imino]-1-phenylbutan-1-one schiff baserdquo Molecules vol 20 no 6 pp9788ndash9802 2015
[29] C A Bolos A T Chaviara D Mourelatos et al ldquoSynthesischaracterization toxicity cytogenetic and in vivo antitumorstudies of 11-dithiolate Cu(II) complexes with di- tri- tetra-amines and 13-thiazoles Structure-activity correlationrdquo Bioor-ganic amp Medicinal Chemistry vol 17 no 8 pp 3142ndash3151 2009
[30] P K Das N Panda and N K Behera ldquoSynthesis character-ization and antimicrobial activities of Schiff base complexesderived from isoniazid and diacetylmonoximerdquo InternationalJournal of Innovative Science Engineering amp Technology vol 3no 1 pp 42ndash54 2016
[31] L Mitu M Ilis N Raman M Imran and S RavichandranldquoTransition metal complexes of isonicotinoylndashhydrazone-4-diphenylaminobenzaldehyde synthesis characterization andantimicrobial studiesrdquo E-Journal of Chemistry vol 9 no 1 pp365ndash372 2012
[32] S A Ali A A Soliman M M Aboaly and R M RamadanldquoChromium molybdenum and ruthenium complexes of 2-hydroxyacetophenone schiff basesrdquo Journal of CoordinationChemistry vol 55 no 10 pp 1161ndash1170 2002
[33] K N Kumar R Ramesh and Y Liu ldquoSynthesis structureand catalytic activity of cycloruthenated carbonyl complexescontaining arylazo phenolate ligandsrdquo Journal of MolecularCatalysis A Chemical vol 265 no 1-2 pp 218ndash226 2007
[34] I P Ejidike and P A Ajibade ldquoSynthesis characterizationantioxidant and antibacterial studies of some metal(II)complexes of tetradentate schiff base ligand (4E)-4-[(2-(119864)-[1-(24-dihydroxyphenyl)ethylidene]aminoethyl)imino]pentan-2-onerdquo Bioinorganic Chemistry and Applications vol 2015Article ID 890734 9 pages 2015
[35] J S Casas A Castineiras F Condori et al ldquoDiorganotin(IV)-promoted deamination of amino acids by pyridoxal SnR2
2+
complexes of pyridoxal 51015840-phosphate and of the Schiff basepyridoxal-pyridoxamine (PLPM) and antibacterial activities ofPLPM and [SnR
2(PLPM-2H)] (R=Me Et Bu Ph)rdquo Polyhedron
vol 22 no 1 pp 53ndash65 2003[36] P J K Inba B Annaraj S Thalamuthu and M A Nee-
lakantan ldquoCu(II) Ni(II) and Zn(II) complexes of salan-typeligand containing ester groups synthesis characterizationelectrochemical properties and in vitro biological activitiesrdquoBioinorganic Chemistry and Applications vol 2013 Article ID439848 11 pages 2013
[37] K Shanker R Rohini V Ravinder P M Reddy and Y-P HoldquoRu(II) complexes of N
4and N
2O2macrocyclic Schiff base lig-
ands their antibacterial and antifungal studiesrdquo SpectrochimicaActa Part A Molecular and Biomolecular Spectroscopy vol 73no 1 pp 205ndash211 2009
[38] M Alias H Kassum and C Shakir ldquoSynthesis physicalcharacterization and biological evaluation of Schiff base M(II)complexesrdquo Journal of the Association of Arab Universities forBasic and Applied Sciences vol 15 no 1 pp 28ndash34 2014
[39] K Shivakumar Shashidhar P V Reddy and M B HallildquoSynthesis spectral characterization and biological activity ofbenzofuran Schiff bases with Co(II) Ni(II) Cu(II) Zn(II)Cd(II) and Hg(II) complexesrdquo Journal of Coordination Chem-istry vol 61 no 14 pp 2274ndash2287 2008
[40] T D Thangadurai and S-K Ihm ldquoNovel bidentate ruthe-nium(III) Schiff base complexes synthetic spectral electro-chemical catalytic and antimicrobial studiesrdquo Transition MetalChemistry vol 29 no 2 pp 189ndash195 2004
[41] C J Ballhausen Introduction to Ligand Field Theory McGarwHill New York NY USA 1962
[42] A B P Lever Inorganic Electronic Spectroscopy Elsevier NewYork NY USA 2nd edition 1984
[43] V V Raju K P Balasubramanian C Jayabalakrishnan and VChinnusamy ldquoSynthesis characterization antimicrobial activ-ities and DNA-Binding studies of some Ru(III) complexesof Schiff basesrdquo International Journal of Applied Biology andPharmaceutical Technology vol 3 no 2 pp 76ndash87 2012
[44] K P Balasubramanian K Parameswari V Chinnusamy RPrabhakaran and K Natarajan ldquoSynthesis characterizationelectro chemistry catalytic and biological activities of ruthe-nium(III) complexes with bidentate N OS donor ligandsrdquo
Bioinorganic Chemistry and Applications 11
Spectrochimica ActamdashPart A Molecular and Biomolecular Spec-troscopy vol 65 no 3-4 pp 678ndash683 2006
[45] A Ghantous M Saikali T Rau H Gali-Muhtasib RSchneider-Stock and N Darwiche ldquoInhibition of tumor pro-motion by parthenolide epigenetic modulation of p21rdquo CancerPrevention Research vol 5 no 11 pp 1298ndash1309 2012
[46] W T ShierMammalian Cell Culture on $5 aDay A LabManualof Low Cost Methods University of the Philippines Los BanosCalif USA 1991
[47] G Raja R J Butcher and C Jayabalakrishnan ldquoStudies onsynthesis characterization DNA interaction and cytotoxicity ofruthenium(II) Schiff base complexesrdquo Spectrochimica Acta PartA Molecular and Biomolecular Spectroscopy vol 94 pp 210ndash215 2012
[48] G Raja R J Butcher and C Jayabalakrishnan ldquoSynthesischaracterization DNA binding and cleavage properties andanticancer studies of ruthenium(III) Schiff base complexesrdquoTransition Metal Chemistry vol 37 no 2 pp 169ndash174 2012
[49] I Gulcin O I Kufrevioglu M Oktay and M EBuyukokuroglu ldquoAntioxidant antimicrobial antiulcer andanalgesic activities of nettle (Urtica dioica L)rdquo Journal of Ethno-pharmacology vol 90 no 2-3 pp 205ndash215 2004
[50] M Viuda-Martos Y R Navajas E S Zapata J Fernandez-Lopez and J A Perez-Alvarez ldquoAntioxidant activity of essentialoils of five spice plants widely used in a Mediterranean dietrdquoFlavour and Fragrance Journal vol 25 no 1 pp 13ndash19 2010
[51] S Mathew and T E Abraham ldquoIn vitro antioxidant activity andscavenging effects of Cinnamomum verum leaf extract assayedby different methodologiesrdquo Food and Chemical Toxicology vol44 no 2 pp 198ndash206 2006
Figure 1 Electronic absorption spectra of the Ru(III) complexes (a) [Ru(DAE)Cl2(H2O)] (b) [Ru(HME)Cl
2(H2O)] (c)
[Ru(MBE)Cl2(H2O)] (d) [Ru(DEE)Cl
2(H2O)]
energy are 2A2g and 2T
1g arising from t42ge1
g configuration[41]
Ru3+ ion with a d5 electronic configuration possesseshigh oxidizing properties and large crystal field parameterAlso charge transfer bands of the type L
120587y rarr T2g were
noticeable within low energy region obscuring weaker bandsthat is due to d-d transitions [22 25] The extinction coef-ficient bands around 613ndash632 nm regions are found to below when compared to the charge transfer bands Thesebands have been assigned to 2T
2g rarr2A2g transition and
are in agreement with the assignment made for similaroctahedral ruthenium(III) complexes [42 43] Absorptionbands within the 452ndash525 nm regions were assigned to thecharge transfer transitions [22 44] Overall the absorptionspectra of the Ru(III)-Schiff base complexes are typical ofoctahedral environment about the ruthenium(III) ions [22]
35 Antiproliferative Activity Investigation into the struc-ture-activity relationship of the isolated Ru(III)-N
2O Schiff
base complexes with respect to different functional groups
on the ligands used for ruthenium ion complex formationhas been conducted via antiproliferative studies Three of theRu(III)-Schiff base compounds alongside parthenolide weresubjected to cell lines tests at different sample concentrationsranging from 001 to 100120583M towards renal cancer cell (TK-10) melanoma cancer cell (UACC-62) and breast cancercell (MCF-7) The cancer cell lines were incubated for 48 hfollowed by the addition of the compounds of variousconcentrations via Sulforhodamine B (SRB) assay [22]
The ruthenium(III) compounds and standard drug(parthenolide) IC
50values are presented in Table 1 and
revealed that the test samples showed significant inhibitionagainst the tested cell lines Figures 2ndash4 represent the cellviability percentages of ruthenium(III)-Schiff base complexesand parthenolide drug against TK-10 UACC-62 and MCF-7 cell lines at different concentrations of ruthenium(III)compounds or parthenolide A high level of antiprolifera-tive potentials against the studied cell lines was exhibitedby parthenolide in accordance with earlier reports [45]The obtained results revealed that treatment of cell lines with
6 Bioinorganic Chemistry and Applications
Table 1 In vitro antiproliferative studies of Ru(III)-Schiff base complexes against TK-10 UACC-62 and MCF-7 cell lines
Compounds Molecular formula Anticancer activity IC50(120583M) 48 h
TK-10 UACC-62 MCF-7[Ru(DAE)Cl
2(H2O)] C
18H24N3O4RuCl2
906 plusmn 118 644 plusmn 038 357 plusmn 109
[Ru(HME)Cl2(H2O)] C
18H23N2O6RuCl2
4109 plusmn 444 631 plusmn 147 488 plusmn 128
[Ru(DEE)Cl2(H2O)] C
17H20N2O4RuCl3
1310 plusmn 281 514 plusmn 109 343 plusmn 148
Parthenolidelowast C15H20O3
050 plusmn 143 089 plusmn 218 044 plusmn 202lowastStandard cytotoxin drug cell lines were treated with different concentrations of the compounds to achieve 50 inhibition of the culture growth when culturedfor 48 h Value represents mean plusmn SD of three independent experimentations
Figure 2 In vitro antiproliferative activity of Ru(III) complexes andparthenolide against human breast cancer cell line (MCF-7)
different concentrations of Ru(III)-Schiff base complexes effi-ciently affected cell viability towardsMCF-7 cells as displayedin Figures 2ndash4 and Table 1 The Ru(III) compounds exhibitedlow to strong in vitro antiproliferative activities againstthe selected cell lines as compared to the standard drug(parthenolide) [Ru(DAE)Cl
2(H2O)] [Ru(HME)Cl
2(H2O)]
and [Ru(DEE)Cl2(H2O)] induced more efficient cell death
with IC50values of 357plusmn109 488plusmn128 and 343plusmn148 120583M
respectively towards human breast cancer cell (MCF-7) cellsthan other investigated cell lines compared with IC
50values
of 044 plusmn 202 120583M MCF-7 for the standard cytotoxin drugparthenolide
The order of activity of the complexes againsthuman melanoma cancer cell (UACC-62) is asfollows [Ru(DEE)Cl
2(H2O)] gt [Ru(HME)Cl
2(H2O)] gt
[Ru(DAE)Cl2(H2O)] With respect to previous report by
Shier [46] compounds exhibiting IC50activity ranging from
10 to 25 120583M are referred to as weak anticancer drugs whilethose with IC
50action between 5 and 10 120583M are moderate
and the compounds possessing activity less than (lt) 500120583M
Figure 3 In vitro antiproliferative activity of Ru(III) complexes andparthenolide against human melanoma cancer cell (UACC-62)
are considered as strong agents Thus the Ru(III) complexesexhibited a weak to strong activity against the investigatedcancer cell lines with the following order of activity MCF-7 gt UACC-62 gt TK-10 However [Ru(DAE)Cl
2(H2O)]
showed the highest antiproliferative activity with IC50
valves of 357 plusmn 109 644 plusmn 038 and 906 plusmn 118 120583M forMCF-7 UACC-62 and TK-10 respectively The biochemicalactivity could be due to the methoxy alkyl chloride groupsubstituents and bridge spacer ethylenediamine whichcould have played a vital role in antiproliferative potentialsof the Ru(III)-N
2O Schiff base complexes In vitro anticancer
activity of the synthesized Ru(III) complexes in this studywas compared with Ru complexes reported by other authorsand found that [Ru(DAE)Cl
2(H2O)] [Ru(HME)Cl
2(H2O)]
and [Ru(DEE)Cl2(H2O)] complexes exhibited higher
antitumor activities [RuCl(CO)(PPh3)L] reported by Raja et
al [47] against human cervical carcinoma cell line (HeLa)after exposure for 48 h gave an IC
50value in the range of
316 120583M and [RuCl2(AsPh
3)L] with an IC
50value of 378120583M
[48] Raju et al [43] reported ruthenium(III) Schiff basecomplexes of the type [RuX
2(PPh3)2(L)] (where X = Cl or
Bioinorganic Chemistry and Applications 7
020
4060
80
100
00101
1
10
100
ce
ll vi
abili
ty
[Parthenolide][Ru(DAE)Cl2(H2O)]
[Ru(HME)Cl2(H2O)][Ru(DEE)Cl2(H2O)]
Concentration (120583M)
Figure 4 In vitro antiproliferative activity of Ru(III) complexes andparthenolide against human renal cancer cell (TK-10)
Br L = monobasic bidentate ligand) complex to have IC50
value in the range of 452120583M
36 Antioxidant Capacity Different antioxidant techniquesand modifications have been put forward to evaluate antiox-idants reactivity and functionality in foods and biologicalsystems as a means of checkmating variety of patholog-ical activities such as cellular injury and aging processthese damaging occurrences are caused by free radicalsHence two free radicals were used for in vitro antioxi-dants activities of the test samples in this study namely11-diphenyl-2-picrylhydrazyl (DPPH) and 221015840-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS)
361 DPPHRadical Scavenging Assay The activity of antiox-idants on DPPH radical is believed to be centred on theirability to donate hydrogen [22] DPPH has been a stablefree radical with the ability to accept hydrogen radical or anelectron and then become a stable molecule [49]
The mode of rummaging the DPPH radical hasextensively been used to appraise antioxidant activities oftest samples in a moderately short period of time comparedto other procedures [49] The reduction in the DPPH radicalcapability is calculated by the decrease in its absorbanceat 517 nm prompted by antioxidants [50] The reduction ofDPPH radical intensity in this study is due to the interactionof Ru(III) complexes with radical and as such scavengingthe radicals by hydrogen donation (Scheme 2) The DPPHactivities by the Ru(III)-N
2O Schiff base complexes exhibit
strong electron donating power when compared to thestandards ascorbic acid and rutin as displayed in Figure 5The calculated IC
Figure 5 DPPH scavenging potential of Ru(III)-Schiff base com-plexes
coefficient) values of Ru(III) compounds are listed in Table 2Compounds [Ru(DAE)Cl
2(H2O)] [Ru(HME)Cl
2(H2O)]
[Ru(MBE)Cl2(H2O)] and [Ru(DEE)Cl
2(H2O)] with an IC
50
value of 160plusmn068 154plusmn044 163plusmn105 and 151plusmn050 120583Mrespectively exhibited higher activity against DPPH thanthe commercially available Vit C and rutin (standard)however [Ru(DEE)Cl
2(H2O)] showed the highest activity of
all investigated ruthenium(III) samples with an IC50value of
151 plusmn 050 120583MScavenging ability of the test samples on the
DPPH radical can be ranked in the following order[Ru(DEE)Cl
2(H2O)] gt [Ru(HME)Cl
2(H2O)] gt
[Ru(DAE)Cl2(H2O)] gt [Ru(MBE)Cl
2(H2O)] gt [Vit C]
gt [rutin]The scavenging effect of the DAE HME MBE andDEE ligands is lower as compared to their correspondingRu(III) complexes owing to the coordination of the organicmolecules to the Ru3+ ion It is further supported by theobserved discolouration from purple DPPH radical solutionto yellow solution showing scavenging of the DPPH radicalsby hydrogen donation (Scheme 2) Hence these complexescould be effective therapeutic agentrsquos preparation for thetreatment of chronic conditions such as cardiovascularneurodegenerative and arteriosclerosis diseases [21]
362 221015840-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)Radical Scavenging Activity To further confirm the synthe-sized Ru(III)-N
2O Schiff base complexes antiradical poten-
tial we examined the ABTS assay in this study A well-knownprotonated radical like 221015840-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) possesses characteristic absorbancemaxima at 734 nm and decreases with the scavenging of theproton radicals [51]The assaymeasures radical scavenging byelectron donation The outcome of Ru(III)-N
2O Schiff base
complexes alongside the standard drugs on ABTS radical ispresented in Table 2 At 734 nm the absorbance of activeABTSlowast solution noticeably declined upon the addition ofdifferent concentrations of ruthenium(III) samples the sametrend was also observed for the standard drugs butylated
8 Bioinorganic Chemistry and Applications
N N NH+
Cl
Cl
N N
O
HO
HRuCl
Cl
N N
OHRu
+
DPPH radical Reduced DPPH
Antioxidant
OH2 OH2
O2N
O2N
O2N
O2N
NO2
H3C H3C
OCH3 OCH3
OCH3OCH3
NO2
517 nm
O∙
N∙
Scheme 2 Conversion of DPPHlowast (purple) to its corresponding hydrazine form (yellow) by the addition of Ru(III) compounds to DPPHlowastdue to proton transfer
Table 2 Radical scavenging abilities (IC50plusmn SD 120583M) of Ru(III)-Schiff base complexes and standard drugs
Rutinlowast 252 plusmn 160 0798 283 plusmn 184 0983Vit Clowast 192 plusmn 107 0978 mdash mdashBHTlowast mdash mdash 164 plusmn 154 0919119899 = 3119883plusmn SEM IC50 growth inhibitory concentration when the inhibition of the tested compounds was 50 the tested compound concentration was IC501198772 correlation coefficient lowastStandards
hydroxytoluene (BHT) and rutin hydrate with the percentageinhibition displayed in Figure 6
The efficacy of the tested samples in quenching ATBSlowastradicals in the system was observed at 100120583gmL the lowestconcentration and Ru(III) complexes exhibited higher ABTS inhibition than the standards [Ru(DEE)Cl
2(H2O)] com-
plex exhibited the highest ABTS scavenging activity amongstthe studied ruthenium(III) complexes with an IC
50value
of 324 plusmn 093 120583M and 0855 1198772 (correlation coefficient) aslisted in Table 2 while complexes of [Ru(DAE)Cl
2(H2O)]
[Ru(HME)Cl2(H2O)] and [Ru(MBE)Cl
2(H2O)] had an IC
50
value of 330 plusmn 089 427 plusmn 117 and 330 plusmn 148 120583Mrespectively
The ABTS scavenging activity pattern of the complexesis ranked in the following order [Ru(HME)Cl
2(H2O)]
lt [Ru(MBE)Cl2(H2O)] = [Ru(DAE)Cl
2(H2O)] lt
[Ru(DEE)Cl2(H2O)] With this result the antiradical
studies showed that the synthesised Ru(III)-N2O Schiff base
complexes may be useful in developing therapeutic agentfor averting cell oxidative damage and as radicals chainterminator This is because various free radicals generated in
the system often lead to cancer cellular injury aging processand cardiovascular diseases [21]
4 Conclusion
In this study we present the synthesis of Ru(III) Schiff basecomplexes formulated as [Ru(LL)Cl
2(H2O)] (LL = DAE
HME MBE and DEE) The complexes were character-ized using the microanalytical conductance electronic andvibrational spectral analysis FTIR spectral data showed thatthe ligand acts as tridentate chelating ligand coordinatingthrough azomethine nitrogen and phenol oxygen atomThe microanalyses were in conformity with the proposedstructures Conductance measurements showed the com-plexes to be nonelectrolytes in DMF Octahedral structureswere assigned to these complexes based on the elementaland spectral information In vitro antiproliferative studiesof the Ru(III) complexes gave a weak to strong inhibitionagainst the studied cancer cell lines with the followingactivity order MCF-7 gt UACC-62 gt TK-10 Significantly
Figure 6 ABTS rummaging activity of Ru(III)-Schiff base com-plexes
further investigation on the compounds free radical scav-enging properties revealed that Ru(III)-Schiff base complexespossessed considerable antioxidant activities The outcomefrom DPPH and ABTS inhibition studies revealed that thecompounds are proficient in donating electron or hydrogenatom and subsequently terminate the chain reactions ina dose-dependent pattern Scavenging ability of the testsamples on the DPPH radicals can be ranked in the fol-lowing order [Ru(DEE)Cl
2(H2O)]gt [Ru(HME)Cl
2(H2O)]gt
[Ru(DAE)Cl2(H2O)] gt [Ru(MBE)Cl
2(H2O)] Thus Ru(III)-
N2O Schiff base complexes showed stronger inhibition of
DPPH at various concentrations
Competing Interests
No conflict of interests regarding the publication of this paperis declared by the authors
Acknowledgments
The authors acknowledge GovanMbeki Research and Devel-opment Centre (GMRDC) University of Fort Hare forfinancial support and IPE acknowledges National ResearchFoundation and Sasol Inzalo Foundation for the award ofPhD scholarship
References
[1] A Butler and J V Walker ldquoMarine haloperoxidasesrdquo ChemicalReviews vol 93 no 5 pp 1937ndash1944 1993
[2] Y Shechter I Goldwaser M Mironchik M Fridkin and DGefel ldquoHistoric perspective and recent developments on theinsulin-like actions of vanadium toward developing vanadium-based drugs for diabetesrdquo Coordination Chemistry Reviews vol237 no 1-2 pp 3ndash11 2003
[3] A M B Bastos J G da Silva P I S Maia et al ldquoOxo-vanadium(IV) and (V) complexes of acetylpyridine-derivedsemicarbazones exhibit insulin-like activityrdquoPolyhedron vol 27no 6 pp 1787ndash1794 2008
[4] R R Eady ldquoCurrent status of structure function relationshipsof vanadiumnitrogenaserdquoCoordination Chemistry Reviews vol237 no 1-2 pp 23ndash30 2003
[5] K H Thompson J H McNeill and C Orvig ldquoVanadiumcompounds as insulin mimicsrdquo Chemical Reviews vol 99 no9 pp 2561ndash2572 1999
[6] G Grivani G Bruno H A Rudbari A D Khalaji and PPourteimouri ldquoSynthesis characterization and crystal structuredetermination of a new oxovanadium(IV) Schiff base complexthe catalytic activity in the epoxidation of cyclooctenerdquo Inor-ganic Chemistry Communications vol 18 pp 15ndash20 2012
[7] J W Pyrz A L Roe L J Stern and L Que Jr ldquoModel studiesof iron-tyrosinate proteinsrdquo Journal of the American ChemicalSociety vol 107 no 3 pp 614ndash620 1985
[8] M Tumer B Erdogan H Koksal S Serin and M Y NutkuldquoPreparation spectroscopic characterisation and thermal anal-yses studies of theCu(II) Pd(II) andVO(IV) complexes of someSchiff base ligandsrdquo Synthesis and Reactivity in Inorganic andMetal-Organic Chemistry vol 28 no 4 pp 529ndash542 1998
[9] J Hine and C Y Yeh ldquoEquilibrium in formation and conforma-tional isomerization of imines derived from isobutyraldehydeand saturated aliphatic primary aminesrdquo Journal of the Ameri-can Chemical Society vol 89 no 11 pp 2669ndash2676 1967
[10] T Opstal and F Verpoort ldquoSynthesis of highly active rutheniumindenylidene complexes for atom-transfer radical polymer-ization and ring-opening-metathesis polymerizationrdquo Ange-wandte ChemiemdashInternational Edition vol 42 no 25 pp 2876ndash2879 2003
[11] B De Clercq F Lefebvre and F Verpoort ldquoImmobilization ofmultifunctional Schiff base containing ruthenium complexeson MCM-41rdquo Applied Catalysis A General vol 247 no 2 pp345ndash364 2003
[12] A Golcu M Tumer H Demirelli and R A WheatleyldquoCd(II) andCu(II) complexes of polydentate Schiff base ligandssynthesis characterization properties and biological activityrdquoInorganica Chimica Acta vol 358 no 6 pp 1785ndash1797 2005
[13] NMishra K Poonia and D Kumar ldquoAn overview of biologicalaspects of Schiff base metal complexesrdquo International Journal ofAdvancements in ResearchampTechnology vol 2 no 8 pp 52ndash662013
[14] L-A H Allen L S Schlesinger and B Kang ldquoVirulent strainsof Helicobacter pylori demonstrate delayed phagocytosis andstimulate homotypic phagosome fusion in macrophagesrdquo TheJournal of Experimental Medicine vol 191 no 1 pp 115ndash1272000
[15] L A Calderon R C L Teles J R S A Leite C Bloch JrS Astolfi-Filho and S M Freitas ldquoSerine protease inhibitorsfromAmazon Leguminosae seeds purification and preliminarycharacterization of two chymotrypsin inhibitors from Ingaumbraticardquo Protein and Peptide Letters vol 8 no 6 pp 485ndash493 2001
[16] P G Cozzi ldquoMetal-Salen Schiff base complexes in catalysispractical aspectsrdquo Chemical Society Reviews vol 33 no 7 pp410ndash421 2004
[17] T Katsuki ldquoUnique asymmetric catalysis of cis-120573 metal com-plexes of salen and its related Schiff-base ligandsrdquo ChemicalSociety Reviews vol 33 no 7 pp 437ndash444 2004
[18] I M I Fakhr N A Hamdy M A Radwan and Y M AhmedldquoSynthesis of new bioactive benzothiophene derivativesrdquo Egyp-tian Journal of Chemistry vol 47 pp 201ndash215 2004
[19] R A A Ammar and A-N M A Alaghaz ldquoSynthesisspectroscopic characterization and potentiometric studies of
10 Bioinorganic Chemistry and Applications
a tetradentate [N2O2] schiff base NN1015840-bis(2-hydroxyben-
zylidene)-11-diaminoethane and its Co(II)Ni(II)Cu(II) andZn(II) complexesrdquo International Journal of ElectrochemicalScience vol 8 no 6 pp 8686ndash8699 2013
[20] A S Gaballa M S Asker A S Barakat and S M TelebldquoSynthesis characterization and biological activity of someplatinum(II) complexes with Schiff bases derived from salicy-laldehyde 2-furaldehyde and phenylenediaminerdquo Spectrochim-ica Acta Part A Molecular and Biomolecular Spectroscopy vol67 no 1 pp 114ndash121 2007
[21] I P Ejidike and P A Ajibade ldquoTransition metal complexesof symmetrical and asymmetrical Schiff bases as antibacterialantifungal antioxidant and anticancer agents progress andprospectsrdquo Reviews in Inorganic Chemistry vol 35 no 4 pp191ndash224 2015
[22] I P Ejidike and P A Ajibade ldquoSynthesis characterization andin vitro antioxidant and anticancer studies of ruthenium(III)complexes of symmetric and asymmetric tetradentate Schiffbasesrdquo Journal of Coordination Chemistry vol 68 no 14 pp2552ndash2564 2015
[23] N P Priya S Arunachalam A Manimaran D Muthupriyaand C Jayabalakrishnan ldquoMononuclear Ru(III) Schiff basecomplexes synthesis spectral redox catalytic and biologicalactivity studiesrdquo Spectrochimica Acta Part A Molecular andBiomolecular Spectroscopy vol 72 no 3 pp 670ndash676 2009
[24] L Mishra R Prajapati and K K Pandey ldquoMixed-ligand Ru(II)complexes with 221015840-bipyridine and tetradentate Schiff basesauxiliary ligands Synthesis physico-chemical study DFT anal-ysis electrochemical and Na+ binding propertiesrdquo Spectrochim-ica ActamdashPart A Molecular and Biomolecular Spectroscopy vol70 no 1 pp 79ndash85 2008
[25] G Venkatachalam and R Ramesh ldquoCatalytic and biologicalactivities of Ru(III) mixed ligand complexes containing NOdonor of 2-hydroxy-1-naphthylideneiminesrdquo SpectrochimicaActa Part A Molecular and Biomolecular Spectroscopy vol 61no 9 pp 2081ndash2087 2005
[26] I P Ejidike and P A Ajibade ldquoSynthesis and in vitro anti-cancer antibacterial and antioxidant studies of unsymmet-rical Schiff base derivatives of 4-[(1E)-N-(2-aminoethyl)eth-animidoyl]benzene-13-diolrdquo Research on Chemical Intermedi-ates vol 42 no 8 pp 6543ndash6555 2016
[27] K I Ansari I Hussain H K Das and S S Mandal ldquoOver-expression of human histone methylase MLL1 upon exposureto a food contaminant mycotoxin deoxynivalenolrdquo The FEBSJournal vol 276 no 12 pp 3299ndash3307 2009
[28] I P Ejidike and P A Ajibade ldquoSynthesis characterization andbiological studies of metal(II) complexes of (3E)-3-[(2-(119864)-[1-(24-Dihydroxyphenyl) ethylidene]aminoethyl)imino]-1-phenylbutan-1-one schiff baserdquo Molecules vol 20 no 6 pp9788ndash9802 2015
[29] C A Bolos A T Chaviara D Mourelatos et al ldquoSynthesischaracterization toxicity cytogenetic and in vivo antitumorstudies of 11-dithiolate Cu(II) complexes with di- tri- tetra-amines and 13-thiazoles Structure-activity correlationrdquo Bioor-ganic amp Medicinal Chemistry vol 17 no 8 pp 3142ndash3151 2009
[30] P K Das N Panda and N K Behera ldquoSynthesis character-ization and antimicrobial activities of Schiff base complexesderived from isoniazid and diacetylmonoximerdquo InternationalJournal of Innovative Science Engineering amp Technology vol 3no 1 pp 42ndash54 2016
[31] L Mitu M Ilis N Raman M Imran and S RavichandranldquoTransition metal complexes of isonicotinoylndashhydrazone-4-diphenylaminobenzaldehyde synthesis characterization andantimicrobial studiesrdquo E-Journal of Chemistry vol 9 no 1 pp365ndash372 2012
[32] S A Ali A A Soliman M M Aboaly and R M RamadanldquoChromium molybdenum and ruthenium complexes of 2-hydroxyacetophenone schiff basesrdquo Journal of CoordinationChemistry vol 55 no 10 pp 1161ndash1170 2002
[33] K N Kumar R Ramesh and Y Liu ldquoSynthesis structureand catalytic activity of cycloruthenated carbonyl complexescontaining arylazo phenolate ligandsrdquo Journal of MolecularCatalysis A Chemical vol 265 no 1-2 pp 218ndash226 2007
[34] I P Ejidike and P A Ajibade ldquoSynthesis characterizationantioxidant and antibacterial studies of some metal(II)complexes of tetradentate schiff base ligand (4E)-4-[(2-(119864)-[1-(24-dihydroxyphenyl)ethylidene]aminoethyl)imino]pentan-2-onerdquo Bioinorganic Chemistry and Applications vol 2015Article ID 890734 9 pages 2015
[35] J S Casas A Castineiras F Condori et al ldquoDiorganotin(IV)-promoted deamination of amino acids by pyridoxal SnR2
2+
complexes of pyridoxal 51015840-phosphate and of the Schiff basepyridoxal-pyridoxamine (PLPM) and antibacterial activities ofPLPM and [SnR
2(PLPM-2H)] (R=Me Et Bu Ph)rdquo Polyhedron
vol 22 no 1 pp 53ndash65 2003[36] P J K Inba B Annaraj S Thalamuthu and M A Nee-
lakantan ldquoCu(II) Ni(II) and Zn(II) complexes of salan-typeligand containing ester groups synthesis characterizationelectrochemical properties and in vitro biological activitiesrdquoBioinorganic Chemistry and Applications vol 2013 Article ID439848 11 pages 2013
[37] K Shanker R Rohini V Ravinder P M Reddy and Y-P HoldquoRu(II) complexes of N
4and N
2O2macrocyclic Schiff base lig-
ands their antibacterial and antifungal studiesrdquo SpectrochimicaActa Part A Molecular and Biomolecular Spectroscopy vol 73no 1 pp 205ndash211 2009
[38] M Alias H Kassum and C Shakir ldquoSynthesis physicalcharacterization and biological evaluation of Schiff base M(II)complexesrdquo Journal of the Association of Arab Universities forBasic and Applied Sciences vol 15 no 1 pp 28ndash34 2014
[39] K Shivakumar Shashidhar P V Reddy and M B HallildquoSynthesis spectral characterization and biological activity ofbenzofuran Schiff bases with Co(II) Ni(II) Cu(II) Zn(II)Cd(II) and Hg(II) complexesrdquo Journal of Coordination Chem-istry vol 61 no 14 pp 2274ndash2287 2008
[40] T D Thangadurai and S-K Ihm ldquoNovel bidentate ruthe-nium(III) Schiff base complexes synthetic spectral electro-chemical catalytic and antimicrobial studiesrdquo Transition MetalChemistry vol 29 no 2 pp 189ndash195 2004
[41] C J Ballhausen Introduction to Ligand Field Theory McGarwHill New York NY USA 1962
[42] A B P Lever Inorganic Electronic Spectroscopy Elsevier NewYork NY USA 2nd edition 1984
[43] V V Raju K P Balasubramanian C Jayabalakrishnan and VChinnusamy ldquoSynthesis characterization antimicrobial activ-ities and DNA-Binding studies of some Ru(III) complexesof Schiff basesrdquo International Journal of Applied Biology andPharmaceutical Technology vol 3 no 2 pp 76ndash87 2012
[44] K P Balasubramanian K Parameswari V Chinnusamy RPrabhakaran and K Natarajan ldquoSynthesis characterizationelectro chemistry catalytic and biological activities of ruthe-nium(III) complexes with bidentate N OS donor ligandsrdquo
Bioinorganic Chemistry and Applications 11
Spectrochimica ActamdashPart A Molecular and Biomolecular Spec-troscopy vol 65 no 3-4 pp 678ndash683 2006
[45] A Ghantous M Saikali T Rau H Gali-Muhtasib RSchneider-Stock and N Darwiche ldquoInhibition of tumor pro-motion by parthenolide epigenetic modulation of p21rdquo CancerPrevention Research vol 5 no 11 pp 1298ndash1309 2012
[46] W T ShierMammalian Cell Culture on $5 aDay A LabManualof Low Cost Methods University of the Philippines Los BanosCalif USA 1991
[47] G Raja R J Butcher and C Jayabalakrishnan ldquoStudies onsynthesis characterization DNA interaction and cytotoxicity ofruthenium(II) Schiff base complexesrdquo Spectrochimica Acta PartA Molecular and Biomolecular Spectroscopy vol 94 pp 210ndash215 2012
[48] G Raja R J Butcher and C Jayabalakrishnan ldquoSynthesischaracterization DNA binding and cleavage properties andanticancer studies of ruthenium(III) Schiff base complexesrdquoTransition Metal Chemistry vol 37 no 2 pp 169ndash174 2012
[49] I Gulcin O I Kufrevioglu M Oktay and M EBuyukokuroglu ldquoAntioxidant antimicrobial antiulcer andanalgesic activities of nettle (Urtica dioica L)rdquo Journal of Ethno-pharmacology vol 90 no 2-3 pp 205ndash215 2004
[50] M Viuda-Martos Y R Navajas E S Zapata J Fernandez-Lopez and J A Perez-Alvarez ldquoAntioxidant activity of essentialoils of five spice plants widely used in a Mediterranean dietrdquoFlavour and Fragrance Journal vol 25 no 1 pp 13ndash19 2010
[51] S Mathew and T E Abraham ldquoIn vitro antioxidant activity andscavenging effects of Cinnamomum verum leaf extract assayedby different methodologiesrdquo Food and Chemical Toxicology vol44 no 2 pp 198ndash206 2006
Table 1 In vitro antiproliferative studies of Ru(III)-Schiff base complexes against TK-10 UACC-62 and MCF-7 cell lines
Compounds Molecular formula Anticancer activity IC50(120583M) 48 h
TK-10 UACC-62 MCF-7[Ru(DAE)Cl
2(H2O)] C
18H24N3O4RuCl2
906 plusmn 118 644 plusmn 038 357 plusmn 109
[Ru(HME)Cl2(H2O)] C
18H23N2O6RuCl2
4109 plusmn 444 631 plusmn 147 488 plusmn 128
[Ru(DEE)Cl2(H2O)] C
17H20N2O4RuCl3
1310 plusmn 281 514 plusmn 109 343 plusmn 148
Parthenolidelowast C15H20O3
050 plusmn 143 089 plusmn 218 044 plusmn 202lowastStandard cytotoxin drug cell lines were treated with different concentrations of the compounds to achieve 50 inhibition of the culture growth when culturedfor 48 h Value represents mean plusmn SD of three independent experimentations
Figure 2 In vitro antiproliferative activity of Ru(III) complexes andparthenolide against human breast cancer cell line (MCF-7)
different concentrations of Ru(III)-Schiff base complexes effi-ciently affected cell viability towardsMCF-7 cells as displayedin Figures 2ndash4 and Table 1 The Ru(III) compounds exhibitedlow to strong in vitro antiproliferative activities againstthe selected cell lines as compared to the standard drug(parthenolide) [Ru(DAE)Cl
2(H2O)] [Ru(HME)Cl
2(H2O)]
and [Ru(DEE)Cl2(H2O)] induced more efficient cell death
with IC50values of 357plusmn109 488plusmn128 and 343plusmn148 120583M
respectively towards human breast cancer cell (MCF-7) cellsthan other investigated cell lines compared with IC
50values
of 044 plusmn 202 120583M MCF-7 for the standard cytotoxin drugparthenolide
The order of activity of the complexes againsthuman melanoma cancer cell (UACC-62) is asfollows [Ru(DEE)Cl
2(H2O)] gt [Ru(HME)Cl
2(H2O)] gt
[Ru(DAE)Cl2(H2O)] With respect to previous report by
Shier [46] compounds exhibiting IC50activity ranging from
10 to 25 120583M are referred to as weak anticancer drugs whilethose with IC
50action between 5 and 10 120583M are moderate
and the compounds possessing activity less than (lt) 500120583M
Figure 3 In vitro antiproliferative activity of Ru(III) complexes andparthenolide against human melanoma cancer cell (UACC-62)
are considered as strong agents Thus the Ru(III) complexesexhibited a weak to strong activity against the investigatedcancer cell lines with the following order of activity MCF-7 gt UACC-62 gt TK-10 However [Ru(DAE)Cl
2(H2O)]
showed the highest antiproliferative activity with IC50
valves of 357 plusmn 109 644 plusmn 038 and 906 plusmn 118 120583M forMCF-7 UACC-62 and TK-10 respectively The biochemicalactivity could be due to the methoxy alkyl chloride groupsubstituents and bridge spacer ethylenediamine whichcould have played a vital role in antiproliferative potentialsof the Ru(III)-N
2O Schiff base complexes In vitro anticancer
activity of the synthesized Ru(III) complexes in this studywas compared with Ru complexes reported by other authorsand found that [Ru(DAE)Cl
2(H2O)] [Ru(HME)Cl
2(H2O)]
and [Ru(DEE)Cl2(H2O)] complexes exhibited higher
antitumor activities [RuCl(CO)(PPh3)L] reported by Raja et
al [47] against human cervical carcinoma cell line (HeLa)after exposure for 48 h gave an IC
50value in the range of
316 120583M and [RuCl2(AsPh
3)L] with an IC
50value of 378120583M
[48] Raju et al [43] reported ruthenium(III) Schiff basecomplexes of the type [RuX
2(PPh3)2(L)] (where X = Cl or
Bioinorganic Chemistry and Applications 7
020
4060
80
100
00101
1
10
100
ce
ll vi
abili
ty
[Parthenolide][Ru(DAE)Cl2(H2O)]
[Ru(HME)Cl2(H2O)][Ru(DEE)Cl2(H2O)]
Concentration (120583M)
Figure 4 In vitro antiproliferative activity of Ru(III) complexes andparthenolide against human renal cancer cell (TK-10)
Br L = monobasic bidentate ligand) complex to have IC50
value in the range of 452120583M
36 Antioxidant Capacity Different antioxidant techniquesand modifications have been put forward to evaluate antiox-idants reactivity and functionality in foods and biologicalsystems as a means of checkmating variety of patholog-ical activities such as cellular injury and aging processthese damaging occurrences are caused by free radicalsHence two free radicals were used for in vitro antioxi-dants activities of the test samples in this study namely11-diphenyl-2-picrylhydrazyl (DPPH) and 221015840-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS)
361 DPPHRadical Scavenging Assay The activity of antiox-idants on DPPH radical is believed to be centred on theirability to donate hydrogen [22] DPPH has been a stablefree radical with the ability to accept hydrogen radical or anelectron and then become a stable molecule [49]
The mode of rummaging the DPPH radical hasextensively been used to appraise antioxidant activities oftest samples in a moderately short period of time comparedto other procedures [49] The reduction in the DPPH radicalcapability is calculated by the decrease in its absorbanceat 517 nm prompted by antioxidants [50] The reduction ofDPPH radical intensity in this study is due to the interactionof Ru(III) complexes with radical and as such scavengingthe radicals by hydrogen donation (Scheme 2) The DPPHactivities by the Ru(III)-N
2O Schiff base complexes exhibit
strong electron donating power when compared to thestandards ascorbic acid and rutin as displayed in Figure 5The calculated IC
Figure 5 DPPH scavenging potential of Ru(III)-Schiff base com-plexes
coefficient) values of Ru(III) compounds are listed in Table 2Compounds [Ru(DAE)Cl
2(H2O)] [Ru(HME)Cl
2(H2O)]
[Ru(MBE)Cl2(H2O)] and [Ru(DEE)Cl
2(H2O)] with an IC
50
value of 160plusmn068 154plusmn044 163plusmn105 and 151plusmn050 120583Mrespectively exhibited higher activity against DPPH thanthe commercially available Vit C and rutin (standard)however [Ru(DEE)Cl
2(H2O)] showed the highest activity of
all investigated ruthenium(III) samples with an IC50value of
151 plusmn 050 120583MScavenging ability of the test samples on the
DPPH radical can be ranked in the following order[Ru(DEE)Cl
2(H2O)] gt [Ru(HME)Cl
2(H2O)] gt
[Ru(DAE)Cl2(H2O)] gt [Ru(MBE)Cl
2(H2O)] gt [Vit C]
gt [rutin]The scavenging effect of the DAE HME MBE andDEE ligands is lower as compared to their correspondingRu(III) complexes owing to the coordination of the organicmolecules to the Ru3+ ion It is further supported by theobserved discolouration from purple DPPH radical solutionto yellow solution showing scavenging of the DPPH radicalsby hydrogen donation (Scheme 2) Hence these complexescould be effective therapeutic agentrsquos preparation for thetreatment of chronic conditions such as cardiovascularneurodegenerative and arteriosclerosis diseases [21]
362 221015840-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)Radical Scavenging Activity To further confirm the synthe-sized Ru(III)-N
2O Schiff base complexes antiradical poten-
tial we examined the ABTS assay in this study A well-knownprotonated radical like 221015840-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) possesses characteristic absorbancemaxima at 734 nm and decreases with the scavenging of theproton radicals [51]The assaymeasures radical scavenging byelectron donation The outcome of Ru(III)-N
2O Schiff base
complexes alongside the standard drugs on ABTS radical ispresented in Table 2 At 734 nm the absorbance of activeABTSlowast solution noticeably declined upon the addition ofdifferent concentrations of ruthenium(III) samples the sametrend was also observed for the standard drugs butylated
8 Bioinorganic Chemistry and Applications
N N NH+
Cl
Cl
N N
O
HO
HRuCl
Cl
N N
OHRu
+
DPPH radical Reduced DPPH
Antioxidant
OH2 OH2
O2N
O2N
O2N
O2N
NO2
H3C H3C
OCH3 OCH3
OCH3OCH3
NO2
517 nm
O∙
N∙
Scheme 2 Conversion of DPPHlowast (purple) to its corresponding hydrazine form (yellow) by the addition of Ru(III) compounds to DPPHlowastdue to proton transfer
Table 2 Radical scavenging abilities (IC50plusmn SD 120583M) of Ru(III)-Schiff base complexes and standard drugs
Rutinlowast 252 plusmn 160 0798 283 plusmn 184 0983Vit Clowast 192 plusmn 107 0978 mdash mdashBHTlowast mdash mdash 164 plusmn 154 0919119899 = 3119883plusmn SEM IC50 growth inhibitory concentration when the inhibition of the tested compounds was 50 the tested compound concentration was IC501198772 correlation coefficient lowastStandards
hydroxytoluene (BHT) and rutin hydrate with the percentageinhibition displayed in Figure 6
The efficacy of the tested samples in quenching ATBSlowastradicals in the system was observed at 100120583gmL the lowestconcentration and Ru(III) complexes exhibited higher ABTS inhibition than the standards [Ru(DEE)Cl
2(H2O)] com-
plex exhibited the highest ABTS scavenging activity amongstthe studied ruthenium(III) complexes with an IC
50value
of 324 plusmn 093 120583M and 0855 1198772 (correlation coefficient) aslisted in Table 2 while complexes of [Ru(DAE)Cl
2(H2O)]
[Ru(HME)Cl2(H2O)] and [Ru(MBE)Cl
2(H2O)] had an IC
50
value of 330 plusmn 089 427 plusmn 117 and 330 plusmn 148 120583Mrespectively
The ABTS scavenging activity pattern of the complexesis ranked in the following order [Ru(HME)Cl
2(H2O)]
lt [Ru(MBE)Cl2(H2O)] = [Ru(DAE)Cl
2(H2O)] lt
[Ru(DEE)Cl2(H2O)] With this result the antiradical
studies showed that the synthesised Ru(III)-N2O Schiff base
complexes may be useful in developing therapeutic agentfor averting cell oxidative damage and as radicals chainterminator This is because various free radicals generated in
the system often lead to cancer cellular injury aging processand cardiovascular diseases [21]
4 Conclusion
In this study we present the synthesis of Ru(III) Schiff basecomplexes formulated as [Ru(LL)Cl
2(H2O)] (LL = DAE
HME MBE and DEE) The complexes were character-ized using the microanalytical conductance electronic andvibrational spectral analysis FTIR spectral data showed thatthe ligand acts as tridentate chelating ligand coordinatingthrough azomethine nitrogen and phenol oxygen atomThe microanalyses were in conformity with the proposedstructures Conductance measurements showed the com-plexes to be nonelectrolytes in DMF Octahedral structureswere assigned to these complexes based on the elementaland spectral information In vitro antiproliferative studiesof the Ru(III) complexes gave a weak to strong inhibitionagainst the studied cancer cell lines with the followingactivity order MCF-7 gt UACC-62 gt TK-10 Significantly
Figure 6 ABTS rummaging activity of Ru(III)-Schiff base com-plexes
further investigation on the compounds free radical scav-enging properties revealed that Ru(III)-Schiff base complexespossessed considerable antioxidant activities The outcomefrom DPPH and ABTS inhibition studies revealed that thecompounds are proficient in donating electron or hydrogenatom and subsequently terminate the chain reactions ina dose-dependent pattern Scavenging ability of the testsamples on the DPPH radicals can be ranked in the fol-lowing order [Ru(DEE)Cl
2(H2O)]gt [Ru(HME)Cl
2(H2O)]gt
[Ru(DAE)Cl2(H2O)] gt [Ru(MBE)Cl
2(H2O)] Thus Ru(III)-
N2O Schiff base complexes showed stronger inhibition of
DPPH at various concentrations
Competing Interests
No conflict of interests regarding the publication of this paperis declared by the authors
Acknowledgments
The authors acknowledge GovanMbeki Research and Devel-opment Centre (GMRDC) University of Fort Hare forfinancial support and IPE acknowledges National ResearchFoundation and Sasol Inzalo Foundation for the award ofPhD scholarship
References
[1] A Butler and J V Walker ldquoMarine haloperoxidasesrdquo ChemicalReviews vol 93 no 5 pp 1937ndash1944 1993
[2] Y Shechter I Goldwaser M Mironchik M Fridkin and DGefel ldquoHistoric perspective and recent developments on theinsulin-like actions of vanadium toward developing vanadium-based drugs for diabetesrdquo Coordination Chemistry Reviews vol237 no 1-2 pp 3ndash11 2003
[3] A M B Bastos J G da Silva P I S Maia et al ldquoOxo-vanadium(IV) and (V) complexes of acetylpyridine-derivedsemicarbazones exhibit insulin-like activityrdquoPolyhedron vol 27no 6 pp 1787ndash1794 2008
[4] R R Eady ldquoCurrent status of structure function relationshipsof vanadiumnitrogenaserdquoCoordination Chemistry Reviews vol237 no 1-2 pp 23ndash30 2003
[5] K H Thompson J H McNeill and C Orvig ldquoVanadiumcompounds as insulin mimicsrdquo Chemical Reviews vol 99 no9 pp 2561ndash2572 1999
[6] G Grivani G Bruno H A Rudbari A D Khalaji and PPourteimouri ldquoSynthesis characterization and crystal structuredetermination of a new oxovanadium(IV) Schiff base complexthe catalytic activity in the epoxidation of cyclooctenerdquo Inor-ganic Chemistry Communications vol 18 pp 15ndash20 2012
[7] J W Pyrz A L Roe L J Stern and L Que Jr ldquoModel studiesof iron-tyrosinate proteinsrdquo Journal of the American ChemicalSociety vol 107 no 3 pp 614ndash620 1985
[8] M Tumer B Erdogan H Koksal S Serin and M Y NutkuldquoPreparation spectroscopic characterisation and thermal anal-yses studies of theCu(II) Pd(II) andVO(IV) complexes of someSchiff base ligandsrdquo Synthesis and Reactivity in Inorganic andMetal-Organic Chemistry vol 28 no 4 pp 529ndash542 1998
[9] J Hine and C Y Yeh ldquoEquilibrium in formation and conforma-tional isomerization of imines derived from isobutyraldehydeand saturated aliphatic primary aminesrdquo Journal of the Ameri-can Chemical Society vol 89 no 11 pp 2669ndash2676 1967
[10] T Opstal and F Verpoort ldquoSynthesis of highly active rutheniumindenylidene complexes for atom-transfer radical polymer-ization and ring-opening-metathesis polymerizationrdquo Ange-wandte ChemiemdashInternational Edition vol 42 no 25 pp 2876ndash2879 2003
[11] B De Clercq F Lefebvre and F Verpoort ldquoImmobilization ofmultifunctional Schiff base containing ruthenium complexeson MCM-41rdquo Applied Catalysis A General vol 247 no 2 pp345ndash364 2003
[12] A Golcu M Tumer H Demirelli and R A WheatleyldquoCd(II) andCu(II) complexes of polydentate Schiff base ligandssynthesis characterization properties and biological activityrdquoInorganica Chimica Acta vol 358 no 6 pp 1785ndash1797 2005
[13] NMishra K Poonia and D Kumar ldquoAn overview of biologicalaspects of Schiff base metal complexesrdquo International Journal ofAdvancements in ResearchampTechnology vol 2 no 8 pp 52ndash662013
[14] L-A H Allen L S Schlesinger and B Kang ldquoVirulent strainsof Helicobacter pylori demonstrate delayed phagocytosis andstimulate homotypic phagosome fusion in macrophagesrdquo TheJournal of Experimental Medicine vol 191 no 1 pp 115ndash1272000
[15] L A Calderon R C L Teles J R S A Leite C Bloch JrS Astolfi-Filho and S M Freitas ldquoSerine protease inhibitorsfromAmazon Leguminosae seeds purification and preliminarycharacterization of two chymotrypsin inhibitors from Ingaumbraticardquo Protein and Peptide Letters vol 8 no 6 pp 485ndash493 2001
[16] P G Cozzi ldquoMetal-Salen Schiff base complexes in catalysispractical aspectsrdquo Chemical Society Reviews vol 33 no 7 pp410ndash421 2004
[17] T Katsuki ldquoUnique asymmetric catalysis of cis-120573 metal com-plexes of salen and its related Schiff-base ligandsrdquo ChemicalSociety Reviews vol 33 no 7 pp 437ndash444 2004
[18] I M I Fakhr N A Hamdy M A Radwan and Y M AhmedldquoSynthesis of new bioactive benzothiophene derivativesrdquo Egyp-tian Journal of Chemistry vol 47 pp 201ndash215 2004
[19] R A A Ammar and A-N M A Alaghaz ldquoSynthesisspectroscopic characterization and potentiometric studies of
10 Bioinorganic Chemistry and Applications
a tetradentate [N2O2] schiff base NN1015840-bis(2-hydroxyben-
zylidene)-11-diaminoethane and its Co(II)Ni(II)Cu(II) andZn(II) complexesrdquo International Journal of ElectrochemicalScience vol 8 no 6 pp 8686ndash8699 2013
[20] A S Gaballa M S Asker A S Barakat and S M TelebldquoSynthesis characterization and biological activity of someplatinum(II) complexes with Schiff bases derived from salicy-laldehyde 2-furaldehyde and phenylenediaminerdquo Spectrochim-ica Acta Part A Molecular and Biomolecular Spectroscopy vol67 no 1 pp 114ndash121 2007
[21] I P Ejidike and P A Ajibade ldquoTransition metal complexesof symmetrical and asymmetrical Schiff bases as antibacterialantifungal antioxidant and anticancer agents progress andprospectsrdquo Reviews in Inorganic Chemistry vol 35 no 4 pp191ndash224 2015
[22] I P Ejidike and P A Ajibade ldquoSynthesis characterization andin vitro antioxidant and anticancer studies of ruthenium(III)complexes of symmetric and asymmetric tetradentate Schiffbasesrdquo Journal of Coordination Chemistry vol 68 no 14 pp2552ndash2564 2015
[23] N P Priya S Arunachalam A Manimaran D Muthupriyaand C Jayabalakrishnan ldquoMononuclear Ru(III) Schiff basecomplexes synthesis spectral redox catalytic and biologicalactivity studiesrdquo Spectrochimica Acta Part A Molecular andBiomolecular Spectroscopy vol 72 no 3 pp 670ndash676 2009
[24] L Mishra R Prajapati and K K Pandey ldquoMixed-ligand Ru(II)complexes with 221015840-bipyridine and tetradentate Schiff basesauxiliary ligands Synthesis physico-chemical study DFT anal-ysis electrochemical and Na+ binding propertiesrdquo Spectrochim-ica ActamdashPart A Molecular and Biomolecular Spectroscopy vol70 no 1 pp 79ndash85 2008
[25] G Venkatachalam and R Ramesh ldquoCatalytic and biologicalactivities of Ru(III) mixed ligand complexes containing NOdonor of 2-hydroxy-1-naphthylideneiminesrdquo SpectrochimicaActa Part A Molecular and Biomolecular Spectroscopy vol 61no 9 pp 2081ndash2087 2005
[26] I P Ejidike and P A Ajibade ldquoSynthesis and in vitro anti-cancer antibacterial and antioxidant studies of unsymmet-rical Schiff base derivatives of 4-[(1E)-N-(2-aminoethyl)eth-animidoyl]benzene-13-diolrdquo Research on Chemical Intermedi-ates vol 42 no 8 pp 6543ndash6555 2016
[27] K I Ansari I Hussain H K Das and S S Mandal ldquoOver-expression of human histone methylase MLL1 upon exposureto a food contaminant mycotoxin deoxynivalenolrdquo The FEBSJournal vol 276 no 12 pp 3299ndash3307 2009
[28] I P Ejidike and P A Ajibade ldquoSynthesis characterization andbiological studies of metal(II) complexes of (3E)-3-[(2-(119864)-[1-(24-Dihydroxyphenyl) ethylidene]aminoethyl)imino]-1-phenylbutan-1-one schiff baserdquo Molecules vol 20 no 6 pp9788ndash9802 2015
[29] C A Bolos A T Chaviara D Mourelatos et al ldquoSynthesischaracterization toxicity cytogenetic and in vivo antitumorstudies of 11-dithiolate Cu(II) complexes with di- tri- tetra-amines and 13-thiazoles Structure-activity correlationrdquo Bioor-ganic amp Medicinal Chemistry vol 17 no 8 pp 3142ndash3151 2009
[30] P K Das N Panda and N K Behera ldquoSynthesis character-ization and antimicrobial activities of Schiff base complexesderived from isoniazid and diacetylmonoximerdquo InternationalJournal of Innovative Science Engineering amp Technology vol 3no 1 pp 42ndash54 2016
[31] L Mitu M Ilis N Raman M Imran and S RavichandranldquoTransition metal complexes of isonicotinoylndashhydrazone-4-diphenylaminobenzaldehyde synthesis characterization andantimicrobial studiesrdquo E-Journal of Chemistry vol 9 no 1 pp365ndash372 2012
[32] S A Ali A A Soliman M M Aboaly and R M RamadanldquoChromium molybdenum and ruthenium complexes of 2-hydroxyacetophenone schiff basesrdquo Journal of CoordinationChemistry vol 55 no 10 pp 1161ndash1170 2002
[33] K N Kumar R Ramesh and Y Liu ldquoSynthesis structureand catalytic activity of cycloruthenated carbonyl complexescontaining arylazo phenolate ligandsrdquo Journal of MolecularCatalysis A Chemical vol 265 no 1-2 pp 218ndash226 2007
[34] I P Ejidike and P A Ajibade ldquoSynthesis characterizationantioxidant and antibacterial studies of some metal(II)complexes of tetradentate schiff base ligand (4E)-4-[(2-(119864)-[1-(24-dihydroxyphenyl)ethylidene]aminoethyl)imino]pentan-2-onerdquo Bioinorganic Chemistry and Applications vol 2015Article ID 890734 9 pages 2015
[35] J S Casas A Castineiras F Condori et al ldquoDiorganotin(IV)-promoted deamination of amino acids by pyridoxal SnR2
2+
complexes of pyridoxal 51015840-phosphate and of the Schiff basepyridoxal-pyridoxamine (PLPM) and antibacterial activities ofPLPM and [SnR
2(PLPM-2H)] (R=Me Et Bu Ph)rdquo Polyhedron
vol 22 no 1 pp 53ndash65 2003[36] P J K Inba B Annaraj S Thalamuthu and M A Nee-
lakantan ldquoCu(II) Ni(II) and Zn(II) complexes of salan-typeligand containing ester groups synthesis characterizationelectrochemical properties and in vitro biological activitiesrdquoBioinorganic Chemistry and Applications vol 2013 Article ID439848 11 pages 2013
[37] K Shanker R Rohini V Ravinder P M Reddy and Y-P HoldquoRu(II) complexes of N
4and N
2O2macrocyclic Schiff base lig-
ands their antibacterial and antifungal studiesrdquo SpectrochimicaActa Part A Molecular and Biomolecular Spectroscopy vol 73no 1 pp 205ndash211 2009
[38] M Alias H Kassum and C Shakir ldquoSynthesis physicalcharacterization and biological evaluation of Schiff base M(II)complexesrdquo Journal of the Association of Arab Universities forBasic and Applied Sciences vol 15 no 1 pp 28ndash34 2014
[39] K Shivakumar Shashidhar P V Reddy and M B HallildquoSynthesis spectral characterization and biological activity ofbenzofuran Schiff bases with Co(II) Ni(II) Cu(II) Zn(II)Cd(II) and Hg(II) complexesrdquo Journal of Coordination Chem-istry vol 61 no 14 pp 2274ndash2287 2008
[40] T D Thangadurai and S-K Ihm ldquoNovel bidentate ruthe-nium(III) Schiff base complexes synthetic spectral electro-chemical catalytic and antimicrobial studiesrdquo Transition MetalChemistry vol 29 no 2 pp 189ndash195 2004
[41] C J Ballhausen Introduction to Ligand Field Theory McGarwHill New York NY USA 1962
[42] A B P Lever Inorganic Electronic Spectroscopy Elsevier NewYork NY USA 2nd edition 1984
[43] V V Raju K P Balasubramanian C Jayabalakrishnan and VChinnusamy ldquoSynthesis characterization antimicrobial activ-ities and DNA-Binding studies of some Ru(III) complexesof Schiff basesrdquo International Journal of Applied Biology andPharmaceutical Technology vol 3 no 2 pp 76ndash87 2012
[44] K P Balasubramanian K Parameswari V Chinnusamy RPrabhakaran and K Natarajan ldquoSynthesis characterizationelectro chemistry catalytic and biological activities of ruthe-nium(III) complexes with bidentate N OS donor ligandsrdquo
Bioinorganic Chemistry and Applications 11
Spectrochimica ActamdashPart A Molecular and Biomolecular Spec-troscopy vol 65 no 3-4 pp 678ndash683 2006
[45] A Ghantous M Saikali T Rau H Gali-Muhtasib RSchneider-Stock and N Darwiche ldquoInhibition of tumor pro-motion by parthenolide epigenetic modulation of p21rdquo CancerPrevention Research vol 5 no 11 pp 1298ndash1309 2012
[46] W T ShierMammalian Cell Culture on $5 aDay A LabManualof Low Cost Methods University of the Philippines Los BanosCalif USA 1991
[47] G Raja R J Butcher and C Jayabalakrishnan ldquoStudies onsynthesis characterization DNA interaction and cytotoxicity ofruthenium(II) Schiff base complexesrdquo Spectrochimica Acta PartA Molecular and Biomolecular Spectroscopy vol 94 pp 210ndash215 2012
[48] G Raja R J Butcher and C Jayabalakrishnan ldquoSynthesischaracterization DNA binding and cleavage properties andanticancer studies of ruthenium(III) Schiff base complexesrdquoTransition Metal Chemistry vol 37 no 2 pp 169ndash174 2012
[49] I Gulcin O I Kufrevioglu M Oktay and M EBuyukokuroglu ldquoAntioxidant antimicrobial antiulcer andanalgesic activities of nettle (Urtica dioica L)rdquo Journal of Ethno-pharmacology vol 90 no 2-3 pp 205ndash215 2004
[50] M Viuda-Martos Y R Navajas E S Zapata J Fernandez-Lopez and J A Perez-Alvarez ldquoAntioxidant activity of essentialoils of five spice plants widely used in a Mediterranean dietrdquoFlavour and Fragrance Journal vol 25 no 1 pp 13ndash19 2010
[51] S Mathew and T E Abraham ldquoIn vitro antioxidant activity andscavenging effects of Cinnamomum verum leaf extract assayedby different methodologiesrdquo Food and Chemical Toxicology vol44 no 2 pp 198ndash206 2006
Figure 4 In vitro antiproliferative activity of Ru(III) complexes andparthenolide against human renal cancer cell (TK-10)
Br L = monobasic bidentate ligand) complex to have IC50
value in the range of 452120583M
36 Antioxidant Capacity Different antioxidant techniquesand modifications have been put forward to evaluate antiox-idants reactivity and functionality in foods and biologicalsystems as a means of checkmating variety of patholog-ical activities such as cellular injury and aging processthese damaging occurrences are caused by free radicalsHence two free radicals were used for in vitro antioxi-dants activities of the test samples in this study namely11-diphenyl-2-picrylhydrazyl (DPPH) and 221015840-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS)
361 DPPHRadical Scavenging Assay The activity of antiox-idants on DPPH radical is believed to be centred on theirability to donate hydrogen [22] DPPH has been a stablefree radical with the ability to accept hydrogen radical or anelectron and then become a stable molecule [49]
The mode of rummaging the DPPH radical hasextensively been used to appraise antioxidant activities oftest samples in a moderately short period of time comparedto other procedures [49] The reduction in the DPPH radicalcapability is calculated by the decrease in its absorbanceat 517 nm prompted by antioxidants [50] The reduction ofDPPH radical intensity in this study is due to the interactionof Ru(III) complexes with radical and as such scavengingthe radicals by hydrogen donation (Scheme 2) The DPPHactivities by the Ru(III)-N
2O Schiff base complexes exhibit
strong electron donating power when compared to thestandards ascorbic acid and rutin as displayed in Figure 5The calculated IC
Figure 5 DPPH scavenging potential of Ru(III)-Schiff base com-plexes
coefficient) values of Ru(III) compounds are listed in Table 2Compounds [Ru(DAE)Cl
2(H2O)] [Ru(HME)Cl
2(H2O)]
[Ru(MBE)Cl2(H2O)] and [Ru(DEE)Cl
2(H2O)] with an IC
50
value of 160plusmn068 154plusmn044 163plusmn105 and 151plusmn050 120583Mrespectively exhibited higher activity against DPPH thanthe commercially available Vit C and rutin (standard)however [Ru(DEE)Cl
2(H2O)] showed the highest activity of
all investigated ruthenium(III) samples with an IC50value of
151 plusmn 050 120583MScavenging ability of the test samples on the
DPPH radical can be ranked in the following order[Ru(DEE)Cl
2(H2O)] gt [Ru(HME)Cl
2(H2O)] gt
[Ru(DAE)Cl2(H2O)] gt [Ru(MBE)Cl
2(H2O)] gt [Vit C]
gt [rutin]The scavenging effect of the DAE HME MBE andDEE ligands is lower as compared to their correspondingRu(III) complexes owing to the coordination of the organicmolecules to the Ru3+ ion It is further supported by theobserved discolouration from purple DPPH radical solutionto yellow solution showing scavenging of the DPPH radicalsby hydrogen donation (Scheme 2) Hence these complexescould be effective therapeutic agentrsquos preparation for thetreatment of chronic conditions such as cardiovascularneurodegenerative and arteriosclerosis diseases [21]
362 221015840-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)Radical Scavenging Activity To further confirm the synthe-sized Ru(III)-N
2O Schiff base complexes antiradical poten-
tial we examined the ABTS assay in this study A well-knownprotonated radical like 221015840-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) possesses characteristic absorbancemaxima at 734 nm and decreases with the scavenging of theproton radicals [51]The assaymeasures radical scavenging byelectron donation The outcome of Ru(III)-N
2O Schiff base
complexes alongside the standard drugs on ABTS radical ispresented in Table 2 At 734 nm the absorbance of activeABTSlowast solution noticeably declined upon the addition ofdifferent concentrations of ruthenium(III) samples the sametrend was also observed for the standard drugs butylated
8 Bioinorganic Chemistry and Applications
N N NH+
Cl
Cl
N N
O
HO
HRuCl
Cl
N N
OHRu
+
DPPH radical Reduced DPPH
Antioxidant
OH2 OH2
O2N
O2N
O2N
O2N
NO2
H3C H3C
OCH3 OCH3
OCH3OCH3
NO2
517 nm
O∙
N∙
Scheme 2 Conversion of DPPHlowast (purple) to its corresponding hydrazine form (yellow) by the addition of Ru(III) compounds to DPPHlowastdue to proton transfer
Table 2 Radical scavenging abilities (IC50plusmn SD 120583M) of Ru(III)-Schiff base complexes and standard drugs
Rutinlowast 252 plusmn 160 0798 283 plusmn 184 0983Vit Clowast 192 plusmn 107 0978 mdash mdashBHTlowast mdash mdash 164 plusmn 154 0919119899 = 3119883plusmn SEM IC50 growth inhibitory concentration when the inhibition of the tested compounds was 50 the tested compound concentration was IC501198772 correlation coefficient lowastStandards
hydroxytoluene (BHT) and rutin hydrate with the percentageinhibition displayed in Figure 6
The efficacy of the tested samples in quenching ATBSlowastradicals in the system was observed at 100120583gmL the lowestconcentration and Ru(III) complexes exhibited higher ABTS inhibition than the standards [Ru(DEE)Cl
2(H2O)] com-
plex exhibited the highest ABTS scavenging activity amongstthe studied ruthenium(III) complexes with an IC
50value
of 324 plusmn 093 120583M and 0855 1198772 (correlation coefficient) aslisted in Table 2 while complexes of [Ru(DAE)Cl
2(H2O)]
[Ru(HME)Cl2(H2O)] and [Ru(MBE)Cl
2(H2O)] had an IC
50
value of 330 plusmn 089 427 plusmn 117 and 330 plusmn 148 120583Mrespectively
The ABTS scavenging activity pattern of the complexesis ranked in the following order [Ru(HME)Cl
2(H2O)]
lt [Ru(MBE)Cl2(H2O)] = [Ru(DAE)Cl
2(H2O)] lt
[Ru(DEE)Cl2(H2O)] With this result the antiradical
studies showed that the synthesised Ru(III)-N2O Schiff base
complexes may be useful in developing therapeutic agentfor averting cell oxidative damage and as radicals chainterminator This is because various free radicals generated in
the system often lead to cancer cellular injury aging processand cardiovascular diseases [21]
4 Conclusion
In this study we present the synthesis of Ru(III) Schiff basecomplexes formulated as [Ru(LL)Cl
2(H2O)] (LL = DAE
HME MBE and DEE) The complexes were character-ized using the microanalytical conductance electronic andvibrational spectral analysis FTIR spectral data showed thatthe ligand acts as tridentate chelating ligand coordinatingthrough azomethine nitrogen and phenol oxygen atomThe microanalyses were in conformity with the proposedstructures Conductance measurements showed the com-plexes to be nonelectrolytes in DMF Octahedral structureswere assigned to these complexes based on the elementaland spectral information In vitro antiproliferative studiesof the Ru(III) complexes gave a weak to strong inhibitionagainst the studied cancer cell lines with the followingactivity order MCF-7 gt UACC-62 gt TK-10 Significantly
Figure 6 ABTS rummaging activity of Ru(III)-Schiff base com-plexes
further investigation on the compounds free radical scav-enging properties revealed that Ru(III)-Schiff base complexespossessed considerable antioxidant activities The outcomefrom DPPH and ABTS inhibition studies revealed that thecompounds are proficient in donating electron or hydrogenatom and subsequently terminate the chain reactions ina dose-dependent pattern Scavenging ability of the testsamples on the DPPH radicals can be ranked in the fol-lowing order [Ru(DEE)Cl
2(H2O)]gt [Ru(HME)Cl
2(H2O)]gt
[Ru(DAE)Cl2(H2O)] gt [Ru(MBE)Cl
2(H2O)] Thus Ru(III)-
N2O Schiff base complexes showed stronger inhibition of
DPPH at various concentrations
Competing Interests
No conflict of interests regarding the publication of this paperis declared by the authors
Acknowledgments
The authors acknowledge GovanMbeki Research and Devel-opment Centre (GMRDC) University of Fort Hare forfinancial support and IPE acknowledges National ResearchFoundation and Sasol Inzalo Foundation for the award ofPhD scholarship
References
[1] A Butler and J V Walker ldquoMarine haloperoxidasesrdquo ChemicalReviews vol 93 no 5 pp 1937ndash1944 1993
[2] Y Shechter I Goldwaser M Mironchik M Fridkin and DGefel ldquoHistoric perspective and recent developments on theinsulin-like actions of vanadium toward developing vanadium-based drugs for diabetesrdquo Coordination Chemistry Reviews vol237 no 1-2 pp 3ndash11 2003
[3] A M B Bastos J G da Silva P I S Maia et al ldquoOxo-vanadium(IV) and (V) complexes of acetylpyridine-derivedsemicarbazones exhibit insulin-like activityrdquoPolyhedron vol 27no 6 pp 1787ndash1794 2008
[4] R R Eady ldquoCurrent status of structure function relationshipsof vanadiumnitrogenaserdquoCoordination Chemistry Reviews vol237 no 1-2 pp 23ndash30 2003
[5] K H Thompson J H McNeill and C Orvig ldquoVanadiumcompounds as insulin mimicsrdquo Chemical Reviews vol 99 no9 pp 2561ndash2572 1999
[6] G Grivani G Bruno H A Rudbari A D Khalaji and PPourteimouri ldquoSynthesis characterization and crystal structuredetermination of a new oxovanadium(IV) Schiff base complexthe catalytic activity in the epoxidation of cyclooctenerdquo Inor-ganic Chemistry Communications vol 18 pp 15ndash20 2012
[7] J W Pyrz A L Roe L J Stern and L Que Jr ldquoModel studiesof iron-tyrosinate proteinsrdquo Journal of the American ChemicalSociety vol 107 no 3 pp 614ndash620 1985
[8] M Tumer B Erdogan H Koksal S Serin and M Y NutkuldquoPreparation spectroscopic characterisation and thermal anal-yses studies of theCu(II) Pd(II) andVO(IV) complexes of someSchiff base ligandsrdquo Synthesis and Reactivity in Inorganic andMetal-Organic Chemistry vol 28 no 4 pp 529ndash542 1998
[9] J Hine and C Y Yeh ldquoEquilibrium in formation and conforma-tional isomerization of imines derived from isobutyraldehydeand saturated aliphatic primary aminesrdquo Journal of the Ameri-can Chemical Society vol 89 no 11 pp 2669ndash2676 1967
[10] T Opstal and F Verpoort ldquoSynthesis of highly active rutheniumindenylidene complexes for atom-transfer radical polymer-ization and ring-opening-metathesis polymerizationrdquo Ange-wandte ChemiemdashInternational Edition vol 42 no 25 pp 2876ndash2879 2003
[11] B De Clercq F Lefebvre and F Verpoort ldquoImmobilization ofmultifunctional Schiff base containing ruthenium complexeson MCM-41rdquo Applied Catalysis A General vol 247 no 2 pp345ndash364 2003
[12] A Golcu M Tumer H Demirelli and R A WheatleyldquoCd(II) andCu(II) complexes of polydentate Schiff base ligandssynthesis characterization properties and biological activityrdquoInorganica Chimica Acta vol 358 no 6 pp 1785ndash1797 2005
[13] NMishra K Poonia and D Kumar ldquoAn overview of biologicalaspects of Schiff base metal complexesrdquo International Journal ofAdvancements in ResearchampTechnology vol 2 no 8 pp 52ndash662013
[14] L-A H Allen L S Schlesinger and B Kang ldquoVirulent strainsof Helicobacter pylori demonstrate delayed phagocytosis andstimulate homotypic phagosome fusion in macrophagesrdquo TheJournal of Experimental Medicine vol 191 no 1 pp 115ndash1272000
[15] L A Calderon R C L Teles J R S A Leite C Bloch JrS Astolfi-Filho and S M Freitas ldquoSerine protease inhibitorsfromAmazon Leguminosae seeds purification and preliminarycharacterization of two chymotrypsin inhibitors from Ingaumbraticardquo Protein and Peptide Letters vol 8 no 6 pp 485ndash493 2001
[16] P G Cozzi ldquoMetal-Salen Schiff base complexes in catalysispractical aspectsrdquo Chemical Society Reviews vol 33 no 7 pp410ndash421 2004
[17] T Katsuki ldquoUnique asymmetric catalysis of cis-120573 metal com-plexes of salen and its related Schiff-base ligandsrdquo ChemicalSociety Reviews vol 33 no 7 pp 437ndash444 2004
[18] I M I Fakhr N A Hamdy M A Radwan and Y M AhmedldquoSynthesis of new bioactive benzothiophene derivativesrdquo Egyp-tian Journal of Chemistry vol 47 pp 201ndash215 2004
[19] R A A Ammar and A-N M A Alaghaz ldquoSynthesisspectroscopic characterization and potentiometric studies of
10 Bioinorganic Chemistry and Applications
a tetradentate [N2O2] schiff base NN1015840-bis(2-hydroxyben-
zylidene)-11-diaminoethane and its Co(II)Ni(II)Cu(II) andZn(II) complexesrdquo International Journal of ElectrochemicalScience vol 8 no 6 pp 8686ndash8699 2013
[20] A S Gaballa M S Asker A S Barakat and S M TelebldquoSynthesis characterization and biological activity of someplatinum(II) complexes with Schiff bases derived from salicy-laldehyde 2-furaldehyde and phenylenediaminerdquo Spectrochim-ica Acta Part A Molecular and Biomolecular Spectroscopy vol67 no 1 pp 114ndash121 2007
[21] I P Ejidike and P A Ajibade ldquoTransition metal complexesof symmetrical and asymmetrical Schiff bases as antibacterialantifungal antioxidant and anticancer agents progress andprospectsrdquo Reviews in Inorganic Chemistry vol 35 no 4 pp191ndash224 2015
[22] I P Ejidike and P A Ajibade ldquoSynthesis characterization andin vitro antioxidant and anticancer studies of ruthenium(III)complexes of symmetric and asymmetric tetradentate Schiffbasesrdquo Journal of Coordination Chemistry vol 68 no 14 pp2552ndash2564 2015
[23] N P Priya S Arunachalam A Manimaran D Muthupriyaand C Jayabalakrishnan ldquoMononuclear Ru(III) Schiff basecomplexes synthesis spectral redox catalytic and biologicalactivity studiesrdquo Spectrochimica Acta Part A Molecular andBiomolecular Spectroscopy vol 72 no 3 pp 670ndash676 2009
[24] L Mishra R Prajapati and K K Pandey ldquoMixed-ligand Ru(II)complexes with 221015840-bipyridine and tetradentate Schiff basesauxiliary ligands Synthesis physico-chemical study DFT anal-ysis electrochemical and Na+ binding propertiesrdquo Spectrochim-ica ActamdashPart A Molecular and Biomolecular Spectroscopy vol70 no 1 pp 79ndash85 2008
[25] G Venkatachalam and R Ramesh ldquoCatalytic and biologicalactivities of Ru(III) mixed ligand complexes containing NOdonor of 2-hydroxy-1-naphthylideneiminesrdquo SpectrochimicaActa Part A Molecular and Biomolecular Spectroscopy vol 61no 9 pp 2081ndash2087 2005
[26] I P Ejidike and P A Ajibade ldquoSynthesis and in vitro anti-cancer antibacterial and antioxidant studies of unsymmet-rical Schiff base derivatives of 4-[(1E)-N-(2-aminoethyl)eth-animidoyl]benzene-13-diolrdquo Research on Chemical Intermedi-ates vol 42 no 8 pp 6543ndash6555 2016
[27] K I Ansari I Hussain H K Das and S S Mandal ldquoOver-expression of human histone methylase MLL1 upon exposureto a food contaminant mycotoxin deoxynivalenolrdquo The FEBSJournal vol 276 no 12 pp 3299ndash3307 2009
[28] I P Ejidike and P A Ajibade ldquoSynthesis characterization andbiological studies of metal(II) complexes of (3E)-3-[(2-(119864)-[1-(24-Dihydroxyphenyl) ethylidene]aminoethyl)imino]-1-phenylbutan-1-one schiff baserdquo Molecules vol 20 no 6 pp9788ndash9802 2015
[29] C A Bolos A T Chaviara D Mourelatos et al ldquoSynthesischaracterization toxicity cytogenetic and in vivo antitumorstudies of 11-dithiolate Cu(II) complexes with di- tri- tetra-amines and 13-thiazoles Structure-activity correlationrdquo Bioor-ganic amp Medicinal Chemistry vol 17 no 8 pp 3142ndash3151 2009
[30] P K Das N Panda and N K Behera ldquoSynthesis character-ization and antimicrobial activities of Schiff base complexesderived from isoniazid and diacetylmonoximerdquo InternationalJournal of Innovative Science Engineering amp Technology vol 3no 1 pp 42ndash54 2016
[31] L Mitu M Ilis N Raman M Imran and S RavichandranldquoTransition metal complexes of isonicotinoylndashhydrazone-4-diphenylaminobenzaldehyde synthesis characterization andantimicrobial studiesrdquo E-Journal of Chemistry vol 9 no 1 pp365ndash372 2012
[32] S A Ali A A Soliman M M Aboaly and R M RamadanldquoChromium molybdenum and ruthenium complexes of 2-hydroxyacetophenone schiff basesrdquo Journal of CoordinationChemistry vol 55 no 10 pp 1161ndash1170 2002
[33] K N Kumar R Ramesh and Y Liu ldquoSynthesis structureand catalytic activity of cycloruthenated carbonyl complexescontaining arylazo phenolate ligandsrdquo Journal of MolecularCatalysis A Chemical vol 265 no 1-2 pp 218ndash226 2007
[34] I P Ejidike and P A Ajibade ldquoSynthesis characterizationantioxidant and antibacterial studies of some metal(II)complexes of tetradentate schiff base ligand (4E)-4-[(2-(119864)-[1-(24-dihydroxyphenyl)ethylidene]aminoethyl)imino]pentan-2-onerdquo Bioinorganic Chemistry and Applications vol 2015Article ID 890734 9 pages 2015
[35] J S Casas A Castineiras F Condori et al ldquoDiorganotin(IV)-promoted deamination of amino acids by pyridoxal SnR2
2+
complexes of pyridoxal 51015840-phosphate and of the Schiff basepyridoxal-pyridoxamine (PLPM) and antibacterial activities ofPLPM and [SnR
2(PLPM-2H)] (R=Me Et Bu Ph)rdquo Polyhedron
vol 22 no 1 pp 53ndash65 2003[36] P J K Inba B Annaraj S Thalamuthu and M A Nee-
lakantan ldquoCu(II) Ni(II) and Zn(II) complexes of salan-typeligand containing ester groups synthesis characterizationelectrochemical properties and in vitro biological activitiesrdquoBioinorganic Chemistry and Applications vol 2013 Article ID439848 11 pages 2013
[37] K Shanker R Rohini V Ravinder P M Reddy and Y-P HoldquoRu(II) complexes of N
4and N
2O2macrocyclic Schiff base lig-
ands their antibacterial and antifungal studiesrdquo SpectrochimicaActa Part A Molecular and Biomolecular Spectroscopy vol 73no 1 pp 205ndash211 2009
[38] M Alias H Kassum and C Shakir ldquoSynthesis physicalcharacterization and biological evaluation of Schiff base M(II)complexesrdquo Journal of the Association of Arab Universities forBasic and Applied Sciences vol 15 no 1 pp 28ndash34 2014
[39] K Shivakumar Shashidhar P V Reddy and M B HallildquoSynthesis spectral characterization and biological activity ofbenzofuran Schiff bases with Co(II) Ni(II) Cu(II) Zn(II)Cd(II) and Hg(II) complexesrdquo Journal of Coordination Chem-istry vol 61 no 14 pp 2274ndash2287 2008
[40] T D Thangadurai and S-K Ihm ldquoNovel bidentate ruthe-nium(III) Schiff base complexes synthetic spectral electro-chemical catalytic and antimicrobial studiesrdquo Transition MetalChemistry vol 29 no 2 pp 189ndash195 2004
[41] C J Ballhausen Introduction to Ligand Field Theory McGarwHill New York NY USA 1962
[42] A B P Lever Inorganic Electronic Spectroscopy Elsevier NewYork NY USA 2nd edition 1984
[43] V V Raju K P Balasubramanian C Jayabalakrishnan and VChinnusamy ldquoSynthesis characterization antimicrobial activ-ities and DNA-Binding studies of some Ru(III) complexesof Schiff basesrdquo International Journal of Applied Biology andPharmaceutical Technology vol 3 no 2 pp 76ndash87 2012
[44] K P Balasubramanian K Parameswari V Chinnusamy RPrabhakaran and K Natarajan ldquoSynthesis characterizationelectro chemistry catalytic and biological activities of ruthe-nium(III) complexes with bidentate N OS donor ligandsrdquo
Bioinorganic Chemistry and Applications 11
Spectrochimica ActamdashPart A Molecular and Biomolecular Spec-troscopy vol 65 no 3-4 pp 678ndash683 2006
[45] A Ghantous M Saikali T Rau H Gali-Muhtasib RSchneider-Stock and N Darwiche ldquoInhibition of tumor pro-motion by parthenolide epigenetic modulation of p21rdquo CancerPrevention Research vol 5 no 11 pp 1298ndash1309 2012
[46] W T ShierMammalian Cell Culture on $5 aDay A LabManualof Low Cost Methods University of the Philippines Los BanosCalif USA 1991
[47] G Raja R J Butcher and C Jayabalakrishnan ldquoStudies onsynthesis characterization DNA interaction and cytotoxicity ofruthenium(II) Schiff base complexesrdquo Spectrochimica Acta PartA Molecular and Biomolecular Spectroscopy vol 94 pp 210ndash215 2012
[48] G Raja R J Butcher and C Jayabalakrishnan ldquoSynthesischaracterization DNA binding and cleavage properties andanticancer studies of ruthenium(III) Schiff base complexesrdquoTransition Metal Chemistry vol 37 no 2 pp 169ndash174 2012
[49] I Gulcin O I Kufrevioglu M Oktay and M EBuyukokuroglu ldquoAntioxidant antimicrobial antiulcer andanalgesic activities of nettle (Urtica dioica L)rdquo Journal of Ethno-pharmacology vol 90 no 2-3 pp 205ndash215 2004
[50] M Viuda-Martos Y R Navajas E S Zapata J Fernandez-Lopez and J A Perez-Alvarez ldquoAntioxidant activity of essentialoils of five spice plants widely used in a Mediterranean dietrdquoFlavour and Fragrance Journal vol 25 no 1 pp 13ndash19 2010
[51] S Mathew and T E Abraham ldquoIn vitro antioxidant activity andscavenging effects of Cinnamomum verum leaf extract assayedby different methodologiesrdquo Food and Chemical Toxicology vol44 no 2 pp 198ndash206 2006
Scheme 2 Conversion of DPPHlowast (purple) to its corresponding hydrazine form (yellow) by the addition of Ru(III) compounds to DPPHlowastdue to proton transfer
Table 2 Radical scavenging abilities (IC50plusmn SD 120583M) of Ru(III)-Schiff base complexes and standard drugs
Rutinlowast 252 plusmn 160 0798 283 plusmn 184 0983Vit Clowast 192 plusmn 107 0978 mdash mdashBHTlowast mdash mdash 164 plusmn 154 0919119899 = 3119883plusmn SEM IC50 growth inhibitory concentration when the inhibition of the tested compounds was 50 the tested compound concentration was IC501198772 correlation coefficient lowastStandards
hydroxytoluene (BHT) and rutin hydrate with the percentageinhibition displayed in Figure 6
The efficacy of the tested samples in quenching ATBSlowastradicals in the system was observed at 100120583gmL the lowestconcentration and Ru(III) complexes exhibited higher ABTS inhibition than the standards [Ru(DEE)Cl
2(H2O)] com-
plex exhibited the highest ABTS scavenging activity amongstthe studied ruthenium(III) complexes with an IC
50value
of 324 plusmn 093 120583M and 0855 1198772 (correlation coefficient) aslisted in Table 2 while complexes of [Ru(DAE)Cl
2(H2O)]
[Ru(HME)Cl2(H2O)] and [Ru(MBE)Cl
2(H2O)] had an IC
50
value of 330 plusmn 089 427 plusmn 117 and 330 plusmn 148 120583Mrespectively
The ABTS scavenging activity pattern of the complexesis ranked in the following order [Ru(HME)Cl
2(H2O)]
lt [Ru(MBE)Cl2(H2O)] = [Ru(DAE)Cl
2(H2O)] lt
[Ru(DEE)Cl2(H2O)] With this result the antiradical
studies showed that the synthesised Ru(III)-N2O Schiff base
complexes may be useful in developing therapeutic agentfor averting cell oxidative damage and as radicals chainterminator This is because various free radicals generated in
the system often lead to cancer cellular injury aging processand cardiovascular diseases [21]
4 Conclusion
In this study we present the synthesis of Ru(III) Schiff basecomplexes formulated as [Ru(LL)Cl
2(H2O)] (LL = DAE
HME MBE and DEE) The complexes were character-ized using the microanalytical conductance electronic andvibrational spectral analysis FTIR spectral data showed thatthe ligand acts as tridentate chelating ligand coordinatingthrough azomethine nitrogen and phenol oxygen atomThe microanalyses were in conformity with the proposedstructures Conductance measurements showed the com-plexes to be nonelectrolytes in DMF Octahedral structureswere assigned to these complexes based on the elementaland spectral information In vitro antiproliferative studiesof the Ru(III) complexes gave a weak to strong inhibitionagainst the studied cancer cell lines with the followingactivity order MCF-7 gt UACC-62 gt TK-10 Significantly
Figure 6 ABTS rummaging activity of Ru(III)-Schiff base com-plexes
further investigation on the compounds free radical scav-enging properties revealed that Ru(III)-Schiff base complexespossessed considerable antioxidant activities The outcomefrom DPPH and ABTS inhibition studies revealed that thecompounds are proficient in donating electron or hydrogenatom and subsequently terminate the chain reactions ina dose-dependent pattern Scavenging ability of the testsamples on the DPPH radicals can be ranked in the fol-lowing order [Ru(DEE)Cl
2(H2O)]gt [Ru(HME)Cl
2(H2O)]gt
[Ru(DAE)Cl2(H2O)] gt [Ru(MBE)Cl
2(H2O)] Thus Ru(III)-
N2O Schiff base complexes showed stronger inhibition of
DPPH at various concentrations
Competing Interests
No conflict of interests regarding the publication of this paperis declared by the authors
Acknowledgments
The authors acknowledge GovanMbeki Research and Devel-opment Centre (GMRDC) University of Fort Hare forfinancial support and IPE acknowledges National ResearchFoundation and Sasol Inzalo Foundation for the award ofPhD scholarship
References
[1] A Butler and J V Walker ldquoMarine haloperoxidasesrdquo ChemicalReviews vol 93 no 5 pp 1937ndash1944 1993
[2] Y Shechter I Goldwaser M Mironchik M Fridkin and DGefel ldquoHistoric perspective and recent developments on theinsulin-like actions of vanadium toward developing vanadium-based drugs for diabetesrdquo Coordination Chemistry Reviews vol237 no 1-2 pp 3ndash11 2003
[3] A M B Bastos J G da Silva P I S Maia et al ldquoOxo-vanadium(IV) and (V) complexes of acetylpyridine-derivedsemicarbazones exhibit insulin-like activityrdquoPolyhedron vol 27no 6 pp 1787ndash1794 2008
[4] R R Eady ldquoCurrent status of structure function relationshipsof vanadiumnitrogenaserdquoCoordination Chemistry Reviews vol237 no 1-2 pp 23ndash30 2003
[5] K H Thompson J H McNeill and C Orvig ldquoVanadiumcompounds as insulin mimicsrdquo Chemical Reviews vol 99 no9 pp 2561ndash2572 1999
[6] G Grivani G Bruno H A Rudbari A D Khalaji and PPourteimouri ldquoSynthesis characterization and crystal structuredetermination of a new oxovanadium(IV) Schiff base complexthe catalytic activity in the epoxidation of cyclooctenerdquo Inor-ganic Chemistry Communications vol 18 pp 15ndash20 2012
[7] J W Pyrz A L Roe L J Stern and L Que Jr ldquoModel studiesof iron-tyrosinate proteinsrdquo Journal of the American ChemicalSociety vol 107 no 3 pp 614ndash620 1985
[8] M Tumer B Erdogan H Koksal S Serin and M Y NutkuldquoPreparation spectroscopic characterisation and thermal anal-yses studies of theCu(II) Pd(II) andVO(IV) complexes of someSchiff base ligandsrdquo Synthesis and Reactivity in Inorganic andMetal-Organic Chemistry vol 28 no 4 pp 529ndash542 1998
[9] J Hine and C Y Yeh ldquoEquilibrium in formation and conforma-tional isomerization of imines derived from isobutyraldehydeand saturated aliphatic primary aminesrdquo Journal of the Ameri-can Chemical Society vol 89 no 11 pp 2669ndash2676 1967
[10] T Opstal and F Verpoort ldquoSynthesis of highly active rutheniumindenylidene complexes for atom-transfer radical polymer-ization and ring-opening-metathesis polymerizationrdquo Ange-wandte ChemiemdashInternational Edition vol 42 no 25 pp 2876ndash2879 2003
[11] B De Clercq F Lefebvre and F Verpoort ldquoImmobilization ofmultifunctional Schiff base containing ruthenium complexeson MCM-41rdquo Applied Catalysis A General vol 247 no 2 pp345ndash364 2003
[12] A Golcu M Tumer H Demirelli and R A WheatleyldquoCd(II) andCu(II) complexes of polydentate Schiff base ligandssynthesis characterization properties and biological activityrdquoInorganica Chimica Acta vol 358 no 6 pp 1785ndash1797 2005
[13] NMishra K Poonia and D Kumar ldquoAn overview of biologicalaspects of Schiff base metal complexesrdquo International Journal ofAdvancements in ResearchampTechnology vol 2 no 8 pp 52ndash662013
[14] L-A H Allen L S Schlesinger and B Kang ldquoVirulent strainsof Helicobacter pylori demonstrate delayed phagocytosis andstimulate homotypic phagosome fusion in macrophagesrdquo TheJournal of Experimental Medicine vol 191 no 1 pp 115ndash1272000
[15] L A Calderon R C L Teles J R S A Leite C Bloch JrS Astolfi-Filho and S M Freitas ldquoSerine protease inhibitorsfromAmazon Leguminosae seeds purification and preliminarycharacterization of two chymotrypsin inhibitors from Ingaumbraticardquo Protein and Peptide Letters vol 8 no 6 pp 485ndash493 2001
[16] P G Cozzi ldquoMetal-Salen Schiff base complexes in catalysispractical aspectsrdquo Chemical Society Reviews vol 33 no 7 pp410ndash421 2004
[17] T Katsuki ldquoUnique asymmetric catalysis of cis-120573 metal com-plexes of salen and its related Schiff-base ligandsrdquo ChemicalSociety Reviews vol 33 no 7 pp 437ndash444 2004
[18] I M I Fakhr N A Hamdy M A Radwan and Y M AhmedldquoSynthesis of new bioactive benzothiophene derivativesrdquo Egyp-tian Journal of Chemistry vol 47 pp 201ndash215 2004
[19] R A A Ammar and A-N M A Alaghaz ldquoSynthesisspectroscopic characterization and potentiometric studies of
10 Bioinorganic Chemistry and Applications
a tetradentate [N2O2] schiff base NN1015840-bis(2-hydroxyben-
zylidene)-11-diaminoethane and its Co(II)Ni(II)Cu(II) andZn(II) complexesrdquo International Journal of ElectrochemicalScience vol 8 no 6 pp 8686ndash8699 2013
[20] A S Gaballa M S Asker A S Barakat and S M TelebldquoSynthesis characterization and biological activity of someplatinum(II) complexes with Schiff bases derived from salicy-laldehyde 2-furaldehyde and phenylenediaminerdquo Spectrochim-ica Acta Part A Molecular and Biomolecular Spectroscopy vol67 no 1 pp 114ndash121 2007
[21] I P Ejidike and P A Ajibade ldquoTransition metal complexesof symmetrical and asymmetrical Schiff bases as antibacterialantifungal antioxidant and anticancer agents progress andprospectsrdquo Reviews in Inorganic Chemistry vol 35 no 4 pp191ndash224 2015
[22] I P Ejidike and P A Ajibade ldquoSynthesis characterization andin vitro antioxidant and anticancer studies of ruthenium(III)complexes of symmetric and asymmetric tetradentate Schiffbasesrdquo Journal of Coordination Chemistry vol 68 no 14 pp2552ndash2564 2015
[23] N P Priya S Arunachalam A Manimaran D Muthupriyaand C Jayabalakrishnan ldquoMononuclear Ru(III) Schiff basecomplexes synthesis spectral redox catalytic and biologicalactivity studiesrdquo Spectrochimica Acta Part A Molecular andBiomolecular Spectroscopy vol 72 no 3 pp 670ndash676 2009
[24] L Mishra R Prajapati and K K Pandey ldquoMixed-ligand Ru(II)complexes with 221015840-bipyridine and tetradentate Schiff basesauxiliary ligands Synthesis physico-chemical study DFT anal-ysis electrochemical and Na+ binding propertiesrdquo Spectrochim-ica ActamdashPart A Molecular and Biomolecular Spectroscopy vol70 no 1 pp 79ndash85 2008
[25] G Venkatachalam and R Ramesh ldquoCatalytic and biologicalactivities of Ru(III) mixed ligand complexes containing NOdonor of 2-hydroxy-1-naphthylideneiminesrdquo SpectrochimicaActa Part A Molecular and Biomolecular Spectroscopy vol 61no 9 pp 2081ndash2087 2005
[26] I P Ejidike and P A Ajibade ldquoSynthesis and in vitro anti-cancer antibacterial and antioxidant studies of unsymmet-rical Schiff base derivatives of 4-[(1E)-N-(2-aminoethyl)eth-animidoyl]benzene-13-diolrdquo Research on Chemical Intermedi-ates vol 42 no 8 pp 6543ndash6555 2016
[27] K I Ansari I Hussain H K Das and S S Mandal ldquoOver-expression of human histone methylase MLL1 upon exposureto a food contaminant mycotoxin deoxynivalenolrdquo The FEBSJournal vol 276 no 12 pp 3299ndash3307 2009
[28] I P Ejidike and P A Ajibade ldquoSynthesis characterization andbiological studies of metal(II) complexes of (3E)-3-[(2-(119864)-[1-(24-Dihydroxyphenyl) ethylidene]aminoethyl)imino]-1-phenylbutan-1-one schiff baserdquo Molecules vol 20 no 6 pp9788ndash9802 2015
[29] C A Bolos A T Chaviara D Mourelatos et al ldquoSynthesischaracterization toxicity cytogenetic and in vivo antitumorstudies of 11-dithiolate Cu(II) complexes with di- tri- tetra-amines and 13-thiazoles Structure-activity correlationrdquo Bioor-ganic amp Medicinal Chemistry vol 17 no 8 pp 3142ndash3151 2009
[30] P K Das N Panda and N K Behera ldquoSynthesis character-ization and antimicrobial activities of Schiff base complexesderived from isoniazid and diacetylmonoximerdquo InternationalJournal of Innovative Science Engineering amp Technology vol 3no 1 pp 42ndash54 2016
[31] L Mitu M Ilis N Raman M Imran and S RavichandranldquoTransition metal complexes of isonicotinoylndashhydrazone-4-diphenylaminobenzaldehyde synthesis characterization andantimicrobial studiesrdquo E-Journal of Chemistry vol 9 no 1 pp365ndash372 2012
[32] S A Ali A A Soliman M M Aboaly and R M RamadanldquoChromium molybdenum and ruthenium complexes of 2-hydroxyacetophenone schiff basesrdquo Journal of CoordinationChemistry vol 55 no 10 pp 1161ndash1170 2002
[33] K N Kumar R Ramesh and Y Liu ldquoSynthesis structureand catalytic activity of cycloruthenated carbonyl complexescontaining arylazo phenolate ligandsrdquo Journal of MolecularCatalysis A Chemical vol 265 no 1-2 pp 218ndash226 2007
[34] I P Ejidike and P A Ajibade ldquoSynthesis characterizationantioxidant and antibacterial studies of some metal(II)complexes of tetradentate schiff base ligand (4E)-4-[(2-(119864)-[1-(24-dihydroxyphenyl)ethylidene]aminoethyl)imino]pentan-2-onerdquo Bioinorganic Chemistry and Applications vol 2015Article ID 890734 9 pages 2015
[35] J S Casas A Castineiras F Condori et al ldquoDiorganotin(IV)-promoted deamination of amino acids by pyridoxal SnR2
2+
complexes of pyridoxal 51015840-phosphate and of the Schiff basepyridoxal-pyridoxamine (PLPM) and antibacterial activities ofPLPM and [SnR
2(PLPM-2H)] (R=Me Et Bu Ph)rdquo Polyhedron
vol 22 no 1 pp 53ndash65 2003[36] P J K Inba B Annaraj S Thalamuthu and M A Nee-
lakantan ldquoCu(II) Ni(II) and Zn(II) complexes of salan-typeligand containing ester groups synthesis characterizationelectrochemical properties and in vitro biological activitiesrdquoBioinorganic Chemistry and Applications vol 2013 Article ID439848 11 pages 2013
[37] K Shanker R Rohini V Ravinder P M Reddy and Y-P HoldquoRu(II) complexes of N
4and N
2O2macrocyclic Schiff base lig-
ands their antibacterial and antifungal studiesrdquo SpectrochimicaActa Part A Molecular and Biomolecular Spectroscopy vol 73no 1 pp 205ndash211 2009
[38] M Alias H Kassum and C Shakir ldquoSynthesis physicalcharacterization and biological evaluation of Schiff base M(II)complexesrdquo Journal of the Association of Arab Universities forBasic and Applied Sciences vol 15 no 1 pp 28ndash34 2014
[39] K Shivakumar Shashidhar P V Reddy and M B HallildquoSynthesis spectral characterization and biological activity ofbenzofuran Schiff bases with Co(II) Ni(II) Cu(II) Zn(II)Cd(II) and Hg(II) complexesrdquo Journal of Coordination Chem-istry vol 61 no 14 pp 2274ndash2287 2008
[40] T D Thangadurai and S-K Ihm ldquoNovel bidentate ruthe-nium(III) Schiff base complexes synthetic spectral electro-chemical catalytic and antimicrobial studiesrdquo Transition MetalChemistry vol 29 no 2 pp 189ndash195 2004
[41] C J Ballhausen Introduction to Ligand Field Theory McGarwHill New York NY USA 1962
[42] A B P Lever Inorganic Electronic Spectroscopy Elsevier NewYork NY USA 2nd edition 1984
[43] V V Raju K P Balasubramanian C Jayabalakrishnan and VChinnusamy ldquoSynthesis characterization antimicrobial activ-ities and DNA-Binding studies of some Ru(III) complexesof Schiff basesrdquo International Journal of Applied Biology andPharmaceutical Technology vol 3 no 2 pp 76ndash87 2012
[44] K P Balasubramanian K Parameswari V Chinnusamy RPrabhakaran and K Natarajan ldquoSynthesis characterizationelectro chemistry catalytic and biological activities of ruthe-nium(III) complexes with bidentate N OS donor ligandsrdquo
Bioinorganic Chemistry and Applications 11
Spectrochimica ActamdashPart A Molecular and Biomolecular Spec-troscopy vol 65 no 3-4 pp 678ndash683 2006
[45] A Ghantous M Saikali T Rau H Gali-Muhtasib RSchneider-Stock and N Darwiche ldquoInhibition of tumor pro-motion by parthenolide epigenetic modulation of p21rdquo CancerPrevention Research vol 5 no 11 pp 1298ndash1309 2012
[46] W T ShierMammalian Cell Culture on $5 aDay A LabManualof Low Cost Methods University of the Philippines Los BanosCalif USA 1991
[47] G Raja R J Butcher and C Jayabalakrishnan ldquoStudies onsynthesis characterization DNA interaction and cytotoxicity ofruthenium(II) Schiff base complexesrdquo Spectrochimica Acta PartA Molecular and Biomolecular Spectroscopy vol 94 pp 210ndash215 2012
[48] G Raja R J Butcher and C Jayabalakrishnan ldquoSynthesischaracterization DNA binding and cleavage properties andanticancer studies of ruthenium(III) Schiff base complexesrdquoTransition Metal Chemistry vol 37 no 2 pp 169ndash174 2012
[49] I Gulcin O I Kufrevioglu M Oktay and M EBuyukokuroglu ldquoAntioxidant antimicrobial antiulcer andanalgesic activities of nettle (Urtica dioica L)rdquo Journal of Ethno-pharmacology vol 90 no 2-3 pp 205ndash215 2004
[50] M Viuda-Martos Y R Navajas E S Zapata J Fernandez-Lopez and J A Perez-Alvarez ldquoAntioxidant activity of essentialoils of five spice plants widely used in a Mediterranean dietrdquoFlavour and Fragrance Journal vol 25 no 1 pp 13ndash19 2010
[51] S Mathew and T E Abraham ldquoIn vitro antioxidant activity andscavenging effects of Cinnamomum verum leaf extract assayedby different methodologiesrdquo Food and Chemical Toxicology vol44 no 2 pp 198ndash206 2006
Figure 6 ABTS rummaging activity of Ru(III)-Schiff base com-plexes
further investigation on the compounds free radical scav-enging properties revealed that Ru(III)-Schiff base complexespossessed considerable antioxidant activities The outcomefrom DPPH and ABTS inhibition studies revealed that thecompounds are proficient in donating electron or hydrogenatom and subsequently terminate the chain reactions ina dose-dependent pattern Scavenging ability of the testsamples on the DPPH radicals can be ranked in the fol-lowing order [Ru(DEE)Cl
2(H2O)]gt [Ru(HME)Cl
2(H2O)]gt
[Ru(DAE)Cl2(H2O)] gt [Ru(MBE)Cl
2(H2O)] Thus Ru(III)-
N2O Schiff base complexes showed stronger inhibition of
DPPH at various concentrations
Competing Interests
No conflict of interests regarding the publication of this paperis declared by the authors
Acknowledgments
The authors acknowledge GovanMbeki Research and Devel-opment Centre (GMRDC) University of Fort Hare forfinancial support and IPE acknowledges National ResearchFoundation and Sasol Inzalo Foundation for the award ofPhD scholarship
References
[1] A Butler and J V Walker ldquoMarine haloperoxidasesrdquo ChemicalReviews vol 93 no 5 pp 1937ndash1944 1993
[2] Y Shechter I Goldwaser M Mironchik M Fridkin and DGefel ldquoHistoric perspective and recent developments on theinsulin-like actions of vanadium toward developing vanadium-based drugs for diabetesrdquo Coordination Chemistry Reviews vol237 no 1-2 pp 3ndash11 2003
[3] A M B Bastos J G da Silva P I S Maia et al ldquoOxo-vanadium(IV) and (V) complexes of acetylpyridine-derivedsemicarbazones exhibit insulin-like activityrdquoPolyhedron vol 27no 6 pp 1787ndash1794 2008
[4] R R Eady ldquoCurrent status of structure function relationshipsof vanadiumnitrogenaserdquoCoordination Chemistry Reviews vol237 no 1-2 pp 23ndash30 2003
[5] K H Thompson J H McNeill and C Orvig ldquoVanadiumcompounds as insulin mimicsrdquo Chemical Reviews vol 99 no9 pp 2561ndash2572 1999
[6] G Grivani G Bruno H A Rudbari A D Khalaji and PPourteimouri ldquoSynthesis characterization and crystal structuredetermination of a new oxovanadium(IV) Schiff base complexthe catalytic activity in the epoxidation of cyclooctenerdquo Inor-ganic Chemistry Communications vol 18 pp 15ndash20 2012
[7] J W Pyrz A L Roe L J Stern and L Que Jr ldquoModel studiesof iron-tyrosinate proteinsrdquo Journal of the American ChemicalSociety vol 107 no 3 pp 614ndash620 1985
[8] M Tumer B Erdogan H Koksal S Serin and M Y NutkuldquoPreparation spectroscopic characterisation and thermal anal-yses studies of theCu(II) Pd(II) andVO(IV) complexes of someSchiff base ligandsrdquo Synthesis and Reactivity in Inorganic andMetal-Organic Chemistry vol 28 no 4 pp 529ndash542 1998
[9] J Hine and C Y Yeh ldquoEquilibrium in formation and conforma-tional isomerization of imines derived from isobutyraldehydeand saturated aliphatic primary aminesrdquo Journal of the Ameri-can Chemical Society vol 89 no 11 pp 2669ndash2676 1967
[10] T Opstal and F Verpoort ldquoSynthesis of highly active rutheniumindenylidene complexes for atom-transfer radical polymer-ization and ring-opening-metathesis polymerizationrdquo Ange-wandte ChemiemdashInternational Edition vol 42 no 25 pp 2876ndash2879 2003
[11] B De Clercq F Lefebvre and F Verpoort ldquoImmobilization ofmultifunctional Schiff base containing ruthenium complexeson MCM-41rdquo Applied Catalysis A General vol 247 no 2 pp345ndash364 2003
[12] A Golcu M Tumer H Demirelli and R A WheatleyldquoCd(II) andCu(II) complexes of polydentate Schiff base ligandssynthesis characterization properties and biological activityrdquoInorganica Chimica Acta vol 358 no 6 pp 1785ndash1797 2005
[13] NMishra K Poonia and D Kumar ldquoAn overview of biologicalaspects of Schiff base metal complexesrdquo International Journal ofAdvancements in ResearchampTechnology vol 2 no 8 pp 52ndash662013
[14] L-A H Allen L S Schlesinger and B Kang ldquoVirulent strainsof Helicobacter pylori demonstrate delayed phagocytosis andstimulate homotypic phagosome fusion in macrophagesrdquo TheJournal of Experimental Medicine vol 191 no 1 pp 115ndash1272000
[15] L A Calderon R C L Teles J R S A Leite C Bloch JrS Astolfi-Filho and S M Freitas ldquoSerine protease inhibitorsfromAmazon Leguminosae seeds purification and preliminarycharacterization of two chymotrypsin inhibitors from Ingaumbraticardquo Protein and Peptide Letters vol 8 no 6 pp 485ndash493 2001
[16] P G Cozzi ldquoMetal-Salen Schiff base complexes in catalysispractical aspectsrdquo Chemical Society Reviews vol 33 no 7 pp410ndash421 2004
[17] T Katsuki ldquoUnique asymmetric catalysis of cis-120573 metal com-plexes of salen and its related Schiff-base ligandsrdquo ChemicalSociety Reviews vol 33 no 7 pp 437ndash444 2004
[18] I M I Fakhr N A Hamdy M A Radwan and Y M AhmedldquoSynthesis of new bioactive benzothiophene derivativesrdquo Egyp-tian Journal of Chemistry vol 47 pp 201ndash215 2004
[19] R A A Ammar and A-N M A Alaghaz ldquoSynthesisspectroscopic characterization and potentiometric studies of
10 Bioinorganic Chemistry and Applications
a tetradentate [N2O2] schiff base NN1015840-bis(2-hydroxyben-
zylidene)-11-diaminoethane and its Co(II)Ni(II)Cu(II) andZn(II) complexesrdquo International Journal of ElectrochemicalScience vol 8 no 6 pp 8686ndash8699 2013
[20] A S Gaballa M S Asker A S Barakat and S M TelebldquoSynthesis characterization and biological activity of someplatinum(II) complexes with Schiff bases derived from salicy-laldehyde 2-furaldehyde and phenylenediaminerdquo Spectrochim-ica Acta Part A Molecular and Biomolecular Spectroscopy vol67 no 1 pp 114ndash121 2007
[21] I P Ejidike and P A Ajibade ldquoTransition metal complexesof symmetrical and asymmetrical Schiff bases as antibacterialantifungal antioxidant and anticancer agents progress andprospectsrdquo Reviews in Inorganic Chemistry vol 35 no 4 pp191ndash224 2015
[22] I P Ejidike and P A Ajibade ldquoSynthesis characterization andin vitro antioxidant and anticancer studies of ruthenium(III)complexes of symmetric and asymmetric tetradentate Schiffbasesrdquo Journal of Coordination Chemistry vol 68 no 14 pp2552ndash2564 2015
[23] N P Priya S Arunachalam A Manimaran D Muthupriyaand C Jayabalakrishnan ldquoMononuclear Ru(III) Schiff basecomplexes synthesis spectral redox catalytic and biologicalactivity studiesrdquo Spectrochimica Acta Part A Molecular andBiomolecular Spectroscopy vol 72 no 3 pp 670ndash676 2009
[24] L Mishra R Prajapati and K K Pandey ldquoMixed-ligand Ru(II)complexes with 221015840-bipyridine and tetradentate Schiff basesauxiliary ligands Synthesis physico-chemical study DFT anal-ysis electrochemical and Na+ binding propertiesrdquo Spectrochim-ica ActamdashPart A Molecular and Biomolecular Spectroscopy vol70 no 1 pp 79ndash85 2008
[25] G Venkatachalam and R Ramesh ldquoCatalytic and biologicalactivities of Ru(III) mixed ligand complexes containing NOdonor of 2-hydroxy-1-naphthylideneiminesrdquo SpectrochimicaActa Part A Molecular and Biomolecular Spectroscopy vol 61no 9 pp 2081ndash2087 2005
[26] I P Ejidike and P A Ajibade ldquoSynthesis and in vitro anti-cancer antibacterial and antioxidant studies of unsymmet-rical Schiff base derivatives of 4-[(1E)-N-(2-aminoethyl)eth-animidoyl]benzene-13-diolrdquo Research on Chemical Intermedi-ates vol 42 no 8 pp 6543ndash6555 2016
[27] K I Ansari I Hussain H K Das and S S Mandal ldquoOver-expression of human histone methylase MLL1 upon exposureto a food contaminant mycotoxin deoxynivalenolrdquo The FEBSJournal vol 276 no 12 pp 3299ndash3307 2009
[28] I P Ejidike and P A Ajibade ldquoSynthesis characterization andbiological studies of metal(II) complexes of (3E)-3-[(2-(119864)-[1-(24-Dihydroxyphenyl) ethylidene]aminoethyl)imino]-1-phenylbutan-1-one schiff baserdquo Molecules vol 20 no 6 pp9788ndash9802 2015
[29] C A Bolos A T Chaviara D Mourelatos et al ldquoSynthesischaracterization toxicity cytogenetic and in vivo antitumorstudies of 11-dithiolate Cu(II) complexes with di- tri- tetra-amines and 13-thiazoles Structure-activity correlationrdquo Bioor-ganic amp Medicinal Chemistry vol 17 no 8 pp 3142ndash3151 2009
[30] P K Das N Panda and N K Behera ldquoSynthesis character-ization and antimicrobial activities of Schiff base complexesderived from isoniazid and diacetylmonoximerdquo InternationalJournal of Innovative Science Engineering amp Technology vol 3no 1 pp 42ndash54 2016
[31] L Mitu M Ilis N Raman M Imran and S RavichandranldquoTransition metal complexes of isonicotinoylndashhydrazone-4-diphenylaminobenzaldehyde synthesis characterization andantimicrobial studiesrdquo E-Journal of Chemistry vol 9 no 1 pp365ndash372 2012
[32] S A Ali A A Soliman M M Aboaly and R M RamadanldquoChromium molybdenum and ruthenium complexes of 2-hydroxyacetophenone schiff basesrdquo Journal of CoordinationChemistry vol 55 no 10 pp 1161ndash1170 2002
[33] K N Kumar R Ramesh and Y Liu ldquoSynthesis structureand catalytic activity of cycloruthenated carbonyl complexescontaining arylazo phenolate ligandsrdquo Journal of MolecularCatalysis A Chemical vol 265 no 1-2 pp 218ndash226 2007
[34] I P Ejidike and P A Ajibade ldquoSynthesis characterizationantioxidant and antibacterial studies of some metal(II)complexes of tetradentate schiff base ligand (4E)-4-[(2-(119864)-[1-(24-dihydroxyphenyl)ethylidene]aminoethyl)imino]pentan-2-onerdquo Bioinorganic Chemistry and Applications vol 2015Article ID 890734 9 pages 2015
[35] J S Casas A Castineiras F Condori et al ldquoDiorganotin(IV)-promoted deamination of amino acids by pyridoxal SnR2
2+
complexes of pyridoxal 51015840-phosphate and of the Schiff basepyridoxal-pyridoxamine (PLPM) and antibacterial activities ofPLPM and [SnR
2(PLPM-2H)] (R=Me Et Bu Ph)rdquo Polyhedron
vol 22 no 1 pp 53ndash65 2003[36] P J K Inba B Annaraj S Thalamuthu and M A Nee-
lakantan ldquoCu(II) Ni(II) and Zn(II) complexes of salan-typeligand containing ester groups synthesis characterizationelectrochemical properties and in vitro biological activitiesrdquoBioinorganic Chemistry and Applications vol 2013 Article ID439848 11 pages 2013
[37] K Shanker R Rohini V Ravinder P M Reddy and Y-P HoldquoRu(II) complexes of N
4and N
2O2macrocyclic Schiff base lig-
ands their antibacterial and antifungal studiesrdquo SpectrochimicaActa Part A Molecular and Biomolecular Spectroscopy vol 73no 1 pp 205ndash211 2009
[38] M Alias H Kassum and C Shakir ldquoSynthesis physicalcharacterization and biological evaluation of Schiff base M(II)complexesrdquo Journal of the Association of Arab Universities forBasic and Applied Sciences vol 15 no 1 pp 28ndash34 2014
[39] K Shivakumar Shashidhar P V Reddy and M B HallildquoSynthesis spectral characterization and biological activity ofbenzofuran Schiff bases with Co(II) Ni(II) Cu(II) Zn(II)Cd(II) and Hg(II) complexesrdquo Journal of Coordination Chem-istry vol 61 no 14 pp 2274ndash2287 2008
[40] T D Thangadurai and S-K Ihm ldquoNovel bidentate ruthe-nium(III) Schiff base complexes synthetic spectral electro-chemical catalytic and antimicrobial studiesrdquo Transition MetalChemistry vol 29 no 2 pp 189ndash195 2004
[41] C J Ballhausen Introduction to Ligand Field Theory McGarwHill New York NY USA 1962
[42] A B P Lever Inorganic Electronic Spectroscopy Elsevier NewYork NY USA 2nd edition 1984
[43] V V Raju K P Balasubramanian C Jayabalakrishnan and VChinnusamy ldquoSynthesis characterization antimicrobial activ-ities and DNA-Binding studies of some Ru(III) complexesof Schiff basesrdquo International Journal of Applied Biology andPharmaceutical Technology vol 3 no 2 pp 76ndash87 2012
[44] K P Balasubramanian K Parameswari V Chinnusamy RPrabhakaran and K Natarajan ldquoSynthesis characterizationelectro chemistry catalytic and biological activities of ruthe-nium(III) complexes with bidentate N OS donor ligandsrdquo
Bioinorganic Chemistry and Applications 11
Spectrochimica ActamdashPart A Molecular and Biomolecular Spec-troscopy vol 65 no 3-4 pp 678ndash683 2006
[45] A Ghantous M Saikali T Rau H Gali-Muhtasib RSchneider-Stock and N Darwiche ldquoInhibition of tumor pro-motion by parthenolide epigenetic modulation of p21rdquo CancerPrevention Research vol 5 no 11 pp 1298ndash1309 2012
[46] W T ShierMammalian Cell Culture on $5 aDay A LabManualof Low Cost Methods University of the Philippines Los BanosCalif USA 1991
[47] G Raja R J Butcher and C Jayabalakrishnan ldquoStudies onsynthesis characterization DNA interaction and cytotoxicity ofruthenium(II) Schiff base complexesrdquo Spectrochimica Acta PartA Molecular and Biomolecular Spectroscopy vol 94 pp 210ndash215 2012
[48] G Raja R J Butcher and C Jayabalakrishnan ldquoSynthesischaracterization DNA binding and cleavage properties andanticancer studies of ruthenium(III) Schiff base complexesrdquoTransition Metal Chemistry vol 37 no 2 pp 169ndash174 2012
[49] I Gulcin O I Kufrevioglu M Oktay and M EBuyukokuroglu ldquoAntioxidant antimicrobial antiulcer andanalgesic activities of nettle (Urtica dioica L)rdquo Journal of Ethno-pharmacology vol 90 no 2-3 pp 205ndash215 2004
[50] M Viuda-Martos Y R Navajas E S Zapata J Fernandez-Lopez and J A Perez-Alvarez ldquoAntioxidant activity of essentialoils of five spice plants widely used in a Mediterranean dietrdquoFlavour and Fragrance Journal vol 25 no 1 pp 13ndash19 2010
[51] S Mathew and T E Abraham ldquoIn vitro antioxidant activity andscavenging effects of Cinnamomum verum leaf extract assayedby different methodologiesrdquo Food and Chemical Toxicology vol44 no 2 pp 198ndash206 2006
a tetradentate [N2O2] schiff base NN1015840-bis(2-hydroxyben-
zylidene)-11-diaminoethane and its Co(II)Ni(II)Cu(II) andZn(II) complexesrdquo International Journal of ElectrochemicalScience vol 8 no 6 pp 8686ndash8699 2013
[20] A S Gaballa M S Asker A S Barakat and S M TelebldquoSynthesis characterization and biological activity of someplatinum(II) complexes with Schiff bases derived from salicy-laldehyde 2-furaldehyde and phenylenediaminerdquo Spectrochim-ica Acta Part A Molecular and Biomolecular Spectroscopy vol67 no 1 pp 114ndash121 2007
[21] I P Ejidike and P A Ajibade ldquoTransition metal complexesof symmetrical and asymmetrical Schiff bases as antibacterialantifungal antioxidant and anticancer agents progress andprospectsrdquo Reviews in Inorganic Chemistry vol 35 no 4 pp191ndash224 2015
[22] I P Ejidike and P A Ajibade ldquoSynthesis characterization andin vitro antioxidant and anticancer studies of ruthenium(III)complexes of symmetric and asymmetric tetradentate Schiffbasesrdquo Journal of Coordination Chemistry vol 68 no 14 pp2552ndash2564 2015
[23] N P Priya S Arunachalam A Manimaran D Muthupriyaand C Jayabalakrishnan ldquoMononuclear Ru(III) Schiff basecomplexes synthesis spectral redox catalytic and biologicalactivity studiesrdquo Spectrochimica Acta Part A Molecular andBiomolecular Spectroscopy vol 72 no 3 pp 670ndash676 2009
[24] L Mishra R Prajapati and K K Pandey ldquoMixed-ligand Ru(II)complexes with 221015840-bipyridine and tetradentate Schiff basesauxiliary ligands Synthesis physico-chemical study DFT anal-ysis electrochemical and Na+ binding propertiesrdquo Spectrochim-ica ActamdashPart A Molecular and Biomolecular Spectroscopy vol70 no 1 pp 79ndash85 2008
[25] G Venkatachalam and R Ramesh ldquoCatalytic and biologicalactivities of Ru(III) mixed ligand complexes containing NOdonor of 2-hydroxy-1-naphthylideneiminesrdquo SpectrochimicaActa Part A Molecular and Biomolecular Spectroscopy vol 61no 9 pp 2081ndash2087 2005
[26] I P Ejidike and P A Ajibade ldquoSynthesis and in vitro anti-cancer antibacterial and antioxidant studies of unsymmet-rical Schiff base derivatives of 4-[(1E)-N-(2-aminoethyl)eth-animidoyl]benzene-13-diolrdquo Research on Chemical Intermedi-ates vol 42 no 8 pp 6543ndash6555 2016
[27] K I Ansari I Hussain H K Das and S S Mandal ldquoOver-expression of human histone methylase MLL1 upon exposureto a food contaminant mycotoxin deoxynivalenolrdquo The FEBSJournal vol 276 no 12 pp 3299ndash3307 2009
[28] I P Ejidike and P A Ajibade ldquoSynthesis characterization andbiological studies of metal(II) complexes of (3E)-3-[(2-(119864)-[1-(24-Dihydroxyphenyl) ethylidene]aminoethyl)imino]-1-phenylbutan-1-one schiff baserdquo Molecules vol 20 no 6 pp9788ndash9802 2015
[29] C A Bolos A T Chaviara D Mourelatos et al ldquoSynthesischaracterization toxicity cytogenetic and in vivo antitumorstudies of 11-dithiolate Cu(II) complexes with di- tri- tetra-amines and 13-thiazoles Structure-activity correlationrdquo Bioor-ganic amp Medicinal Chemistry vol 17 no 8 pp 3142ndash3151 2009
[30] P K Das N Panda and N K Behera ldquoSynthesis character-ization and antimicrobial activities of Schiff base complexesderived from isoniazid and diacetylmonoximerdquo InternationalJournal of Innovative Science Engineering amp Technology vol 3no 1 pp 42ndash54 2016
[31] L Mitu M Ilis N Raman M Imran and S RavichandranldquoTransition metal complexes of isonicotinoylndashhydrazone-4-diphenylaminobenzaldehyde synthesis characterization andantimicrobial studiesrdquo E-Journal of Chemistry vol 9 no 1 pp365ndash372 2012
[32] S A Ali A A Soliman M M Aboaly and R M RamadanldquoChromium molybdenum and ruthenium complexes of 2-hydroxyacetophenone schiff basesrdquo Journal of CoordinationChemistry vol 55 no 10 pp 1161ndash1170 2002
[33] K N Kumar R Ramesh and Y Liu ldquoSynthesis structureand catalytic activity of cycloruthenated carbonyl complexescontaining arylazo phenolate ligandsrdquo Journal of MolecularCatalysis A Chemical vol 265 no 1-2 pp 218ndash226 2007
[34] I P Ejidike and P A Ajibade ldquoSynthesis characterizationantioxidant and antibacterial studies of some metal(II)complexes of tetradentate schiff base ligand (4E)-4-[(2-(119864)-[1-(24-dihydroxyphenyl)ethylidene]aminoethyl)imino]pentan-2-onerdquo Bioinorganic Chemistry and Applications vol 2015Article ID 890734 9 pages 2015
[35] J S Casas A Castineiras F Condori et al ldquoDiorganotin(IV)-promoted deamination of amino acids by pyridoxal SnR2
2+
complexes of pyridoxal 51015840-phosphate and of the Schiff basepyridoxal-pyridoxamine (PLPM) and antibacterial activities ofPLPM and [SnR
2(PLPM-2H)] (R=Me Et Bu Ph)rdquo Polyhedron
vol 22 no 1 pp 53ndash65 2003[36] P J K Inba B Annaraj S Thalamuthu and M A Nee-
lakantan ldquoCu(II) Ni(II) and Zn(II) complexes of salan-typeligand containing ester groups synthesis characterizationelectrochemical properties and in vitro biological activitiesrdquoBioinorganic Chemistry and Applications vol 2013 Article ID439848 11 pages 2013
[37] K Shanker R Rohini V Ravinder P M Reddy and Y-P HoldquoRu(II) complexes of N
4and N
2O2macrocyclic Schiff base lig-
ands their antibacterial and antifungal studiesrdquo SpectrochimicaActa Part A Molecular and Biomolecular Spectroscopy vol 73no 1 pp 205ndash211 2009
[38] M Alias H Kassum and C Shakir ldquoSynthesis physicalcharacterization and biological evaluation of Schiff base M(II)complexesrdquo Journal of the Association of Arab Universities forBasic and Applied Sciences vol 15 no 1 pp 28ndash34 2014
[39] K Shivakumar Shashidhar P V Reddy and M B HallildquoSynthesis spectral characterization and biological activity ofbenzofuran Schiff bases with Co(II) Ni(II) Cu(II) Zn(II)Cd(II) and Hg(II) complexesrdquo Journal of Coordination Chem-istry vol 61 no 14 pp 2274ndash2287 2008
[40] T D Thangadurai and S-K Ihm ldquoNovel bidentate ruthe-nium(III) Schiff base complexes synthetic spectral electro-chemical catalytic and antimicrobial studiesrdquo Transition MetalChemistry vol 29 no 2 pp 189ndash195 2004
[41] C J Ballhausen Introduction to Ligand Field Theory McGarwHill New York NY USA 1962
[42] A B P Lever Inorganic Electronic Spectroscopy Elsevier NewYork NY USA 2nd edition 1984
[43] V V Raju K P Balasubramanian C Jayabalakrishnan and VChinnusamy ldquoSynthesis characterization antimicrobial activ-ities and DNA-Binding studies of some Ru(III) complexesof Schiff basesrdquo International Journal of Applied Biology andPharmaceutical Technology vol 3 no 2 pp 76ndash87 2012
[44] K P Balasubramanian K Parameswari V Chinnusamy RPrabhakaran and K Natarajan ldquoSynthesis characterizationelectro chemistry catalytic and biological activities of ruthe-nium(III) complexes with bidentate N OS donor ligandsrdquo
Bioinorganic Chemistry and Applications 11
Spectrochimica ActamdashPart A Molecular and Biomolecular Spec-troscopy vol 65 no 3-4 pp 678ndash683 2006
[45] A Ghantous M Saikali T Rau H Gali-Muhtasib RSchneider-Stock and N Darwiche ldquoInhibition of tumor pro-motion by parthenolide epigenetic modulation of p21rdquo CancerPrevention Research vol 5 no 11 pp 1298ndash1309 2012
[46] W T ShierMammalian Cell Culture on $5 aDay A LabManualof Low Cost Methods University of the Philippines Los BanosCalif USA 1991
[47] G Raja R J Butcher and C Jayabalakrishnan ldquoStudies onsynthesis characterization DNA interaction and cytotoxicity ofruthenium(II) Schiff base complexesrdquo Spectrochimica Acta PartA Molecular and Biomolecular Spectroscopy vol 94 pp 210ndash215 2012
[48] G Raja R J Butcher and C Jayabalakrishnan ldquoSynthesischaracterization DNA binding and cleavage properties andanticancer studies of ruthenium(III) Schiff base complexesrdquoTransition Metal Chemistry vol 37 no 2 pp 169ndash174 2012
[49] I Gulcin O I Kufrevioglu M Oktay and M EBuyukokuroglu ldquoAntioxidant antimicrobial antiulcer andanalgesic activities of nettle (Urtica dioica L)rdquo Journal of Ethno-pharmacology vol 90 no 2-3 pp 205ndash215 2004
[50] M Viuda-Martos Y R Navajas E S Zapata J Fernandez-Lopez and J A Perez-Alvarez ldquoAntioxidant activity of essentialoils of five spice plants widely used in a Mediterranean dietrdquoFlavour and Fragrance Journal vol 25 no 1 pp 13ndash19 2010
[51] S Mathew and T E Abraham ldquoIn vitro antioxidant activity andscavenging effects of Cinnamomum verum leaf extract assayedby different methodologiesrdquo Food and Chemical Toxicology vol44 no 2 pp 198ndash206 2006
Spectrochimica ActamdashPart A Molecular and Biomolecular Spec-troscopy vol 65 no 3-4 pp 678ndash683 2006
[45] A Ghantous M Saikali T Rau H Gali-Muhtasib RSchneider-Stock and N Darwiche ldquoInhibition of tumor pro-motion by parthenolide epigenetic modulation of p21rdquo CancerPrevention Research vol 5 no 11 pp 1298ndash1309 2012
[46] W T ShierMammalian Cell Culture on $5 aDay A LabManualof Low Cost Methods University of the Philippines Los BanosCalif USA 1991
[47] G Raja R J Butcher and C Jayabalakrishnan ldquoStudies onsynthesis characterization DNA interaction and cytotoxicity ofruthenium(II) Schiff base complexesrdquo Spectrochimica Acta PartA Molecular and Biomolecular Spectroscopy vol 94 pp 210ndash215 2012
[48] G Raja R J Butcher and C Jayabalakrishnan ldquoSynthesischaracterization DNA binding and cleavage properties andanticancer studies of ruthenium(III) Schiff base complexesrdquoTransition Metal Chemistry vol 37 no 2 pp 169ndash174 2012
[49] I Gulcin O I Kufrevioglu M Oktay and M EBuyukokuroglu ldquoAntioxidant antimicrobial antiulcer andanalgesic activities of nettle (Urtica dioica L)rdquo Journal of Ethno-pharmacology vol 90 no 2-3 pp 205ndash215 2004
[50] M Viuda-Martos Y R Navajas E S Zapata J Fernandez-Lopez and J A Perez-Alvarez ldquoAntioxidant activity of essentialoils of five spice plants widely used in a Mediterranean dietrdquoFlavour and Fragrance Journal vol 25 no 1 pp 13ndash19 2010
[51] S Mathew and T E Abraham ldquoIn vitro antioxidant activity andscavenging effects of Cinnamomum verum leaf extract assayedby different methodologiesrdquo Food and Chemical Toxicology vol44 no 2 pp 198ndash206 2006
