Research ArticleIsolation, Identification, Molecular and Electronic Structure,Vibrational Spectroscopic Investigation, and Anti-HIV-1 Activityof Karanjin Using Density Functional Theory
1 Department of Physics, Government Danteshwari P.G.College, Dantewada 494449, India2Department of Physics, Government Kakatiya Post Graduate College, Jagdalpur, Bastar, Chhattisgarh 494001, India3 Department of Chemistry, Lucknow University, Lucknow 226007, India4National Botanical Research Institute, Lucknow 226007, India
Correspondence should be addressed to Apoorva Dwivedi; [email protected]
Received 17 January 2014; Revised 9 April 2014; Accepted 9 April 2014; Published 7 May 2014
“Karanjin” (3-methoxy furano-2,3,7,8-flavone) is an anti-HIV drug, and it is particularly effective in the treatment of gastricproblems. The method of isolation of “Karanjin” followed the Principles of Green Chemistry (eco-friendly and effortless method).The optimized geometry of the “Karanjin” molecule has been determined by the method of density functional theory (DFT).Using this optimized structure, we have calculated the infrared wavenumbers and compared them with the experimental data. Thecalculated wavenumbers are in an excellent agreement with the experimental values. On the basis of fully optimized ground-statestructure, TDDFT//B3LYP/LANL2DZ calculations have been used to determine the low-lying excited states of Karanjin. Basedon these results, we have discussed the correlation between the vibrational modes and the crystalline structure of “Karanjin.” Acomplete assignment is provided for the observed FTIR spectra. This is the first report of the isolation, molecular and electronicstructure using vibrational spectroscopic investigation, density functional theory, and anti-HIV-1 activity of “Karanjin.”
1. Introduction
Pongamia pinnata is a medium sized glabrous tree, foundthroughout Indian forests [1]. Different parts of this planthave been used as a source of traditional medicine. P. pinnataseeds contain oil which is mainly used in tanning industryfor dressing of leather and to some extent it is used in soapindustry. Oil is employed in scabies, herpes, and leucoderma,and sometimes as stomachic and cholagogue in dyspepsiaand sluggish liver [2]. “Karanjin” is an active principleresponsible for the curative effects of the oil in skin disease[1]. Seed extract inhibits growth of herpes simplex virus andalso possesses hypoglycemic, antioxidative, antiulcerogenic,anti-inflammatory, and analgesic properties [3]. During thecourse of exploration of new compounds from P. pinnataseed oil, several workers [4–6] have identified some newcompounds of its seed oil apart from “Karanjin.” “Karanjin”
possess pesticidal [7], insecticidal [8], and anti-inflammatoryactivity [9].
Considering the role of “Karanjin” in different areas, inthe present communication, we have carried out isolation andidentification of “Karanjin” by ecofriendly method and testedfor its anti-HIV activity. The molecular structure of the well-known natural product “Karanjin” has been studied usingthe density functional theory. The equilibrium geometry,harmonic vibrational frequencies, and HOMO-LUMO gaphave been calculated by the density functional B3LYPmethodemploying 6-311 G (d, p) as the basis set. The detailedinterpretation of the vibrational spectra of Karanjin in termsof the normal mode analysis has been reported. The mainobjective of the present study is to investigate in detailthe vibrational spectra of the important biological molecule(Karanjin) by DFT [10] method, which can presumably help
Hindawi Publishing CorporationJournal of eoretical ChemistryVolume 2014, Article ID 680987, 13 pageshttp://dx.doi.org/10.1155/2014/680987
2 Journal of Theoretical Chemistry
33H
31C
32O
34H
30C
26C25C
12H
13H
28H27C
2C 7C17O
8C
24C3C
22H29H
1C
6C
9C14H
4C
20H
5C
19C23O
11C
10C
18O
16H
21H
15H
A
B C
D
Figure 1: Model molecular structure of Karanjin.
in understanding its dynamical behavior. To the best ofour knowledge, no detailed DFT calculations and anti-HIVactivity have been performed on “Karanjin” so far in theliterature.
2. Experimental Methods(Structure and Spectra)
The molecular structure of the title compound “Karanjin” ismade bymolecularmodeling.Themodelmolecular structureof the compound is given in Figure 1. Fourier transforminfrared spectrum was recorded with FTIR Perkin Elmerspectrometer in KBr dispersion in the range of 500 to4000 cm−1 for the title molecule. The comparison of thecalculated and experimental FTIR and UV visible spectra of“Karanjin” is given in Figures 2 and 3, respectively.
3. Computational Methods
The initial geometry was generated from the standard geo-metrical parameters and was minimized without any con-straint in the potential energy surface.The gradient correcteddensity functional theory (DFT) with the three-parameterhybrid functional (B3) [11] for the exchange part and the Lee-Yang-Parr (LYP) correlation function [12] has been employedfor the computation of molecular structure, vibrational fre-quencies, HOMO-LUMO, and energies of the optimizedstructures, using Gaussian 09 [13]. The calculated vibrationalfrequencies have also been scaled by a factor of 0.963[14]. By combining the results of the GaussView program[15] with symmetry considerations, vibrational frequencyassignments were made with a high degree of accuracy. Weused this approach for the prediction of IR frequencies oftitle compound and found it to be very straightforward.Density functional theory calculations are reported to pro-vide excellent vibrational frequencies of organic compoundif the calculated frequencies are scaled to compensate for theapproximate treatment of electron correlation, for basis setdeficiencies and for anharmonicity. A number of studies havebeen carried out regarding calculations of vibrational spectra
500 1000 1500 2500 3000 3500 4000
Abso
rban
ce (a
.u.)
ExperimentalCalculated
Wavenumbers (cm−1)
Figure 2: Comparison of calculated and experimental FTIR spectraof Karanjin.
200 250 300 350 400 450 500 550 600 650
Abso
rban
ce (a
.u.)
Theoretical
Experimental
𝜆max
Figure 3: Comparison of calculated and experimental UV visiblespectra of Karanjin.
by using B3LYP methods with 6-311 G (d, p) basis set. Thescaling factor was applied successfully for B3LYPmethod andwas found to be easily transferable in a number of molecules.Thus, vibrational frequencies calculated by using the B3LYPfunctional with 6-311G (d, p) as basis set can be utilized toeliminate the uncertainties in the fundamental assignment inthe IR spectra.
4. Results and Discussion
4.1. Eco-Friendly Method. Here it needs to be highlightedthat so far “Karanjin” has been isolated through columnchromatography (silica gel, 100–200 mesh) or by preparativeHPLC [16–18], but in our study the method was eco-friendly and effortless and followed the Principles of GreenChemistry. Implementing these Green Chemical Principlesrequires a certain investment, since the current, very inex-pensive chemical processes must be redesigned. A typicalchemical process generates products and wastes from raw
Journal of Theoretical Chemistry 3
materials such as substrates, solvents, and reagents. If mostof the reagents and the solvent can be recycled, the mass flowlooks quite different.
4.2. Isolation of “Karanjin”. The shade dried Karanja seeds(Pongamia pinnata) of 3.5 kg were extracted with methanol(MeOH) (4.5 lit) at room temperature.The combinedMeOHextract was concentrated under reduced pressure at 40∘C toa dark viscous mass. It was concentrated to dryness and keptat 4∘C for 24 hr; after adding ethanol, shake it properly andkeep on for settling down of crystals for few hours. Colorlesscrystals (11.2 g) were obtained from crystallizationwith EtOHisolated with TLC in 98 : 2 chloroform and MeOH and asingle spot was obtained.
4.3. Identification of “Karanjin”. Isolated compound identi-fied as “Karanjin” (3-methoxy furano-(20,30 : 7,8)-flavone) bydirect comparison of co-TLC andmelting point of 162∘Cwiththat of authentic sample obtained from Sigma-Aldrich andwas also confirmed by the 1H NMR and 13C NMR reportedin the literature [19].
4.4. Cytotoxicity and Anti-HIV-1 Activity of Compound.Compound “Karanjin” was tested for cytotoxicity againstC8166 cells (CC50), and anti-HIV-1 activity was evaluated bythe inhibition assay for the cytopathic effects of HIV-1(EC
50
)< using AZT as a positive control; the compound exertedmoderate cytotoxic activity against C8166 cells with CC
50
>
693.15 𝜇M and showed anti-HIV-1 activity with EC50
=49.43 𝜇M and selectivity index (CC
50
/EC50
) more than 14.02.Cytotoxicity and anti-HIV-1 activity of compound is shownin Table 1.
4.5. Anti-HIV-1 Assay. Cytotoxicity against C8166 cells(CC50
) was assessed using the MTT method, and anti-HIV-1 activity was evaluated by the inhibition assay for thecytopathic effects of HIV-1(EC
50
) [20].
4.6. Molecular Structure. The equilibrium geometry optimi-zation of “Karanjin” has been achieved by energy minimiza-tion, using DFT at the B3LYP level, employing LANL2DZas the basis set given in Table 2. The optimized geometry ofthe molecule under study is confirmed to be located at thelocal true minima on potential energy surface, as the calcu-lated vibrational spectra contain no imaginary wavenumber.“Karanjin” is an unsymmetrical molecule having C
1
pointgroup symmetry. The given molecule has four rings. Out ofthese, three are six membered hexagonal rings and one fivemembered pentagonal ring in which A andC are heterocyclicrings in which one carbon is replaced by oxygen. Due to theantibonding repulsion, these rings are slightly shifted towardsthe plane. The given structure of “Karanjin” is slightly shiftedfrom the planar structure to minimize its surface energy.Due to this reason, ring D gets shifted from its plane. Theoptimized bond length of C–C in five membered ring Aranges between 1.353 A and 1.438 A, while, for another sixmembered ring B, this ranges between 1.379 A and 1.415 A.The optimized bond length of C–C in six membered ringC ranges between 1.367 A and 1.471 A, while, for another six
Table 1
Compound CytotoxicityCC50 (𝜇M)
Anti-HIV-1activity,
EC50 (𝜇M)
Selectivityindex,
CC50/EC50
KJ 693.15 49.43 >14.02AZT 5746.1 0.0147 390406.06
membered ring D, this ranges between 1.389 A and 1.405 A.This difference in the C–C bond length is attributed to thedifference in bond strength.TheoptimizedC–Obond lengthsin ring A are found to be 1.362 A and 1.373 A, while, in ringC, the optimized C–O bond lengths are found to be 1.357 Aand 1.371 A.The optimized C–O bond length attached to ringC is found to be 1.363 A. Bond length of carbonyl group C=Oattached to the ring C is calculated to be 1.227 A. Values of allthe bond angles are given in Table 2 and all are in agreementwith the previous experimental and theoretical studies ondifferent biomolecules [21–23].
4.7. Vibrational Assignments. The molecule “Karanjin” con-tains 34 atoms and therefore has 96 normal modes of vibra-tion. All the 96 fundamental vibrations are IR active. Theharmonic vibrational frequencies calculated for Karanjin atDFT (B3LYP) level using LANL2DZ as the basis set andthe experimental frequencies (FTIR) have been comparedin Table 3 along with their vibrational assignments of thenormal modes. Vibrational assignments are based on theobservation of the animated modes in GaussView.
In “Karanjin,” the C–H functional group is present ata number of positions. The stretching vibration, ](C–H), isexpected to occur in the region 2900–3200 cm−1. The calcu-lated values of the ](C–H) vibration lie within this spectralrange. For C–H stretching vibrations, intense bands arecalculated at 2902, 2989, and 3060 cm−1 which matches wellthe experimental frequencies observed at 2929, 2972, and3052 cm−1.
The other important stretching vibrations correspondto the C=O moieties at the C
7
position. The region 1600–1750 cm−1 is generally considered as the double bond stretch-ing region for C=O, C=C, and C=N bonds [24–27]. TheC=O stretching vibration, ](C=O), appears as a prominentmode in the FTIR spectra at 1624 cm−1 which matches wellthe calculated one, that is, 1632 cm−1. For C–C stretchingvibration an intense band is calculated at 1539 cm−1 whichis found to be in good agreement with the experimentalone, that is, 1526 cm−1. Due to the deformation of ring Avibration, an intense band is calculated at 1369 cm−1 which isin very good agreement with the experimental one, that is,1369 cm−1. Due to breathingmode in ring B vibration, intenseband is calculated at 1250 cm−1 which nearly matches theexperimental one, that is, 1225 cm−1. Due to out of plane(C–C–H) vibration, intense band appears at 739 cm−1. The–CH3
functional group is an important constituent of“Karanjin” and vibrations corresponding to this group arepresent in a number of modes. The stretching vibrations ofthese groups appear in a number of modes. An intense banddue to butterfly motion in CH
3
appears in the experimental
4 Journal of Theoretical Chemistry
Table 2: Optimized geometrical parameters of Karanjin by B3LYP/6-311G (d, p) methods.
Table 3: Vibrational assignments of Karanjin with B3LYP/6-311G (d, p).
B3LYP (calculate) IR (int.) Exp. Vibrational assignments41 0.4616 — Ring D twist from rest of the molecule47 0.0408 — Slight bending in whole molecule58 1.4783 — Slight bending in whole molecule71 1.2198 — Rock CH3
182 1.3627 — Bending in whole molecule216 3.8318 — Floating of whole molecule231 1.4454 — Bending in whole molecule257 4.7668 — 𝛾(C–C–C) in whole molecule265 0.8668 — Whole molecule stretching299 1.2843 — 𝛾(C–C–C) in whole molecule314 3.3777 — Twist (C–O–CH3)324 4.4912 — 𝜏(C–C–C=O)362 1.0152 — 𝜏(C–C–O–CH3)398 0.2783 — 𝛾(C–C–C) Ring D412 16.6519 422 Ring A bends from joint to ring B441 1.5627 — 𝛾(C–C–C) ring D477 10.432 — 𝜏(C–C–C–C) in whole molecule486 4.307 490 𝜏(C–C–O–CH3)525 0.5385 — 𝛾(C–C–H) rings A and B549 1.0232 — 𝜏(C–C–C–C) ring B580 5.7233 589 𝛾(C–C–H) ring A607 1.0343 — 𝜏(C–C–C–C) ring D615 5.088 — 𝜏(C–C–C–C) ring D622 5.8291 — 𝜏(C–C–C–C) ring D629 7.1766 632 𝛾(C–C–C) ring D + 𝛾(C–C–H) ring D639 2.7418 — 𝜏(C–C–C–O) + 𝜏(C–C–C–C)673 15.257 — 𝛽(C–C–C) ring B681 35.221 693 𝛾(C–C–H) ring D714 5.4099 — 𝛾(C–C–H) ring A739 70.1363 730 𝛾(C–C–H) ring A743 19.7507 — Bending in whole molecule757 18.7847 757 𝛾(C–C–H) ring D + 𝛾(C–C–C) ring D773 7.1237 — 𝛾(C–C–H) in whole molecule
6 Journal of Theoretical Chemistry
Table 3: Continued.
B3LYP (calculate) IR (int.) Exp. Vibrational assignments809 11.2216 — 𝛾(C–C–H) ring B819 9.2691 — 𝛽(C–C–C) ring B + 𝛽(C–O–C) ring A825 1.1522 — 𝛾(C–C–H) ring D839 0.8883 833 𝛾(C–C–H) ring A870 12.1445 886 𝛽(C–C–O) ring A + 𝛽(C–C–C) ring A907 1.2768 — 𝛾(C–C–H) ring D922 9.1487 — 𝛽(C–C–C) rings C and D935 16.2356 — 𝛽(C–C–H) ring A + 𝛽(C–C–C) ring B945 0.0615 — 𝛾(C–C–H) ring B951 1.3957 954 𝛾(C–C–H) ring D968 0.4403 — 𝛾(C–C–H) ring D976 0.873 — 𝛽(C–C–C) ring D1002 24.0341 — 𝜔(O–H)1006 14.4736 — 𝛽(C–C–H) rings A and B + 𝛽(C–C–C) ring B1014 24.7318 — 𝛽(C–C–H) ring D1034 37.6874 1032 𝛽(C–C–O) ring A + 𝛽(C–C–H) ring A1065 37.523 1078 𝛽(C–C–H) ring D1108 32.1303 — 𝛽(C–C–H) rings A and B1112 3.026 — 𝛽(C–C–H) rings A and B1120 14.9274 — Twist CH3
1138 3.8577 — 𝛽(C–C–H) ring D1140 195.8791 1132 𝛽(C–C–H) in whole molecule + 𝛽(C–C–C) ring B1151 51.793 Twist CH3 + 𝛽(C–C–H) in whole molecule1164 11.6598 1163 𝛽(C–C–H) ring D1187 103.9113 — 𝛽(C–C–H) in whole molecule1195 103.0799 — 𝛽(C–C–H) ring B + twist CH3
1214 5.214 — 𝛽(C–C–H) rings A and B1250 100.8387 1225 Breathing in ring B1273 8.6432 — Ring D deformation1304 6.3433 — 𝛽(C–C–H) ring D1310 19.154 — 𝛽(C–C–H) in whole molecule1330 153.5339 1339 𝛽(C–C–C) rings B and C + 𝛽(C–C–H) ring D1369 121.7396 1369 Ring A deformation1408 52.4486 1405 Butterfly in CH3
1417 8.0248 — 𝛽(C–C–H) in whole molecule1418 17.7601 — 𝛽(C–C–H) in whole molecule1424 2.3616 — 𝑆(H–C–H) in CH3
1434 72.9917 — 𝛽(C–C–H) ring B + ](C–C) ring A1456 17.1709 — 𝑆(H–C–H) in CH3
1465 14.0125 1460 𝛽(C–C–H) ring D1504 14.0743 — ](C–C) ring A1539 26.0649 1526 ](C–C) rings C and D1554 6.2017 — ](C–C) in whole molecule1566 74.9616 — ](C–C) in whole molecule1578 1.1856 — ](C–C) ring D1592 64.7197 — Ring A deformation1632 379.2331 1624 ](C=O)2902 62.4466 2929 ](C–H) in (O–CH3)2989 35.857 2972 ](C–H) in (O–CH3)3024 7.4574 — ](C–H) in (O–CH3)
Journal of Theoretical Chemistry 7
Table 3: Continued.B3LYP (calculate) IR (int.) Exp. Vibrational assignments3038 0.0903 — ](C–H) ring D3048 14.3705 — ](C–H) ring D3060 29.321 3052 ](C–H) ring D3072 1.1549 — ](C–H) ring B3078 5.8476 — ](C–H) ring D3084 4.8586 — ](C–H) ring B3106 2.4619 — ](C–H) ring D3127 1.4105 3131 ](C–H) ring A3149 0.1629 3153 ](C–H) ring A]: stretching; 𝛽: in plane bending; 𝛾: out of plane bending; 𝜏: torsion.
Table 4: Calculated parameters using TDDFT//B3LYP/LANL2DZ for Karanjin.
Excitation CIcoefficient
Expansion wave length (nm)calculated (Exp.) Oscillator strength Energy (eV)
spectrum at 1405 cm−1 which matches well the peak at1408 cm−1, in the calculated spectrum.
In “Karanjin,” a very important vibration corresponds tothe modes involving the vibrations of the ring atoms. Forthe purpose of simplifying the analysis, we have classifiedthe structure of “Karanjin” into four rings A, B, C, and D asshown in Figure 1.The ring stretching vibrations, ] (ring), arecomplicated combinations of the stretching of C–O and C–C bonds. The most important ring stretching vibrations arethe ring breathing, ring deformation, and so forth. Other ringvibration modes present a mixed profile.
There are some frequencies in the lower region due tothe torsion and mixed bending modes having appreciableIR intensity in calculated FTIR spectrum. Furthermore,the study of low frequency vibrations is of great signifi-cance, because it gives information on weak intermolecularinteractions, which takes place in enzyme reactions [28].Knowledge of low frequency mode is also essential for theinterpretation of the effect of electromagnetic radiation onbiological systems [29].
The calculated (scaled) and experimental frequenciesshow some deviation which can be due to the combination ofelectron correlation effects, insufficiency of basis set, and theunevenness of the potential energy surface and also may beexplained by the presence of external medium taken duringexperimental FTIR analysis.The theoretical calculations havebeen done on gas-phase molecule.
4.8. Electronic Spectra and Electronic Properties of Karanjin.On the basis of fully optimized ground-state structure,TDDFT//B3LYP/LANL2DZ calculations have been used todetermine the low-lying excited states of “Karanjin.” Theparameters calculated involve the vertical excitation energies,oscillator strength (𝑓), and wavelength by using the Gaussian09W code. Experimental wavelengths are not available sothese calculated data can presumably help the experimen-talists. Electronic transitions determined from excited statecalculations are listed in Table 4 for the three lowest energytransitions of the molecule. TD-DFT calculation predictsthree intense electronic transitions at 4.2188 eV (293.89 nm),5.9317 eV (209.02), and 6.7948 eV (182.47) with an oscillatorstrengths of 0.2818, 0.3189, and 0.2131, respectively, whichare compared with the measured experimental data (Exp. =310 nm and 274 nm).
The electronic structure of the “Karanjin” in the gas phasehas been calculated with DFT using the B3LYP /6-311 G (d, p)as the basis set. HOMO and LUMO are the basic electronicparameters associated with the orbital in a molecule andthe difference between them, resulting in energy gap. Notonly energy gap (frontier orbital gap) helps to describe thechemical reactivity and kinetic stability of the molecule butalso these orbitals find out theway themolecule interactswithother species.TheHOMO-LUMOenergy gap is an importantmeasure for stability index. It establishes correlations invarious chemical and biochemical systems [30, 31].
8 Journal of Theoretical Chemistry
0.008 0.004 0.0020.001
0.001
−0.001
−0.001
−0.001
−0.001
−0.002
−0.002
−0.002
−0.004
−0.004
−0.004
−0.008
−0.008
−0.008
Figure 4: 3D and 2D plots of the highest occupied molecular orbital for Karanjin.
0.008
0.008
0.004
0.004
0.002
0.002
0.001
0.001
0.001
−0.001
−0.001
−0.001
−0.002
−0.002
−0.002
−0.004
−0.004
−0.008
−0.008
Figure 5: 3D and 2D plots of lowest unoccupied molecular orbital for Karanjin.
Table 5: Lowest energy, HOMO-LUMOgap (frontier orbital energygap), and dipole moment of Karanjin by B3LYP/6-311G (d, p)methods.Parameters KaranjinEnergy (in au) −994.2536HOMO (in eV) −6.17377LUMO (in eV) −1.92332Frontier orbital energy gap (in eV) 4.25045Dipole moment (in Debye) 3.86
The plots of the HOMO, LUMO, and electrostatic poten-tial for both themolecules in 2D and 3D are shown in Figures4, 5, and 6. The HOMO is found to be concentrated overthe whole atoms, but the LUMO lies mainly over the wholemolecule but less over ringA.The calculated value of the fron-tier orbital energy gap is 4.25 eV (Table 5). The low frontier
orbital gap is also associated with a high chemical reactivityand low kinetic stability [32]. The molecular electrostaticpotential (MESP) is an important factor by which we canconfirm the electrostatic potential region distribution of sizeand shape of molecules as well as the total physiology of themolecules. We have plotted 2D and 3D MESP structures ofthe title compound as shown in Figure 6.The electronegativeregion is outside the molecule near the oxygen atoms. Theenergy equal to the shielded potential energy surface isrequired for any substitution reaction near oxygen. The elec-tronegative lines (in between −0.08 a.u. and −0.02 a.u.) forma closed contour which clearly indicates that total flux passingin between these curves is not equal to zero. For any nucle-ophilic substitution reaction near oxygen (closed contourarea), an amount of energy equal to shielded potential energysurface is required; however, remaining part of molecule issuitable for electrophilic substitution reaction.Thus, it can be
Journal of Theoretical Chemistry 9
Table 6: Calculated 𝜀HOMO, 𝜀LUMO, energy band gap (𝜀𝐿−𝜀𝐻
), chemical potential (𝜇), electronegativity (𝜒), global hardness (𝜂), global softness(𝑆), and global electrophilicity index (𝜔) for Karanjin at B3LYP/6-311G (d, p) level.
Karanjin 𝜀𝐻
𝜀𝐿
𝜀𝐿
− 𝜀𝐻
𝜒 𝜇 𝜂 𝑆 𝜔
A −6.17377 −1.92332 4.25045 4.04854 −4.04854 2.12523 0.23527 3.85622
0.008
0.008
0.0040.0020.001
−0.001
−0.001
−0.001
−0.002
−0.002
−0.002
−0.02
−0.02
−0.004
−0.004
−0.004
−0.04−0.008
−0.008
−0.008
−0.08
0.2
0.20.2
0.4
0.4
0.8
0.2
0.020.02
0.02
0.02
0.04
0.04
0.04
0.04
0.08
0.080.08
0.08
0.08
Figure 6: 3D and 2D plots of molecular electrostatic potential.
asserted thatMESP values have been shown to be well relatedto biological properties [33–35].
4.9. Global Reactivity Descriptors. The energies of frontiermolecular orbitals (𝜀HOMO, 𝜀LUMO), energy band gap (𝜀LUMO−
𝜀HOMO), electronegativity (𝜒), chemical potential (𝜇), globalhardness (𝜂), global softness (𝑆), and global electrophilicityindex (𝜔) [36–39] of “Karanjin” have been listed in Table 6.On the basis of 𝜀HOMO and 𝜀LUMO, these parameters arecalculated using (1) as given below
𝜒 = −
1
2
(𝜀LUMO + 𝜀HOMO)
𝜇 = −𝜒 =
1
2
(𝜀LUMO + 𝜀HOMO)
𝜂 =
1
2
(𝜀LUMO − 𝜀HOMO)
𝑆 =
1
2𝜂
𝜔 =
𝜇2
2𝜂
.
(1)
4.10. Local Reactivity Descriptors. The Fukui function (FF)of a molecule provides information on the reactivity. TheFF successfully predicts relative site reactivities for mostchemical systems and as such it provides a method forunderstanding and categorizing chemical reactions.The atomwith the highest FF value is highly reactive when comparedto the other atoms in the molecule. These values representthe qualitative descriptors of reactivity of different atoms
in the molecule. Ayers and Parr [40] have elucidated thatmolecules tend to react where the FF is the largest whenattacked by soft reagents and in places where the FF is foundto be smaller when attacked by hard reagents. The use ofthe Fukui functions for the site selectivity of the Karanjinmolecule for nucleophilic and electrophilic attacks has beenmade with special emphasis to the dependence of the Fukuivalues on the basis of B3LYP/6-311G(d, p) level of theory.Using the Mulliken atomic charges of neutral, cation, andanion, state of Karanjin, the Fukui functions (𝑓
+
𝑘
, 𝑓−
𝑘
, 𝑓0
𝑘
),local softness (𝑠
+
𝑘
, 𝑠−
𝑘
, 𝑠0
𝑘
), and local electrophilicity indices(𝜔+
𝑘
, 𝜔−
𝑘
, 𝜔0
𝑘
) [37, 38], the Fukui functions are calculated usingthe following (2):
𝑓+
𝑘
= [𝑞 (𝑁 + 1) − 𝑞 (𝑁)] for nucleophilic attack
𝑓−
𝑘
= [𝑞 (𝑁) − 𝑞 (𝑁 − 1)] for electrophilic attack
𝑓0
𝑘
=
1
2
[𝑞 (𝑁 + 1) + 𝑞 (𝑁 − 1)] for radical attack.
(2)
Local softness and electrophilicity indices are calculatedusing (3)
𝑠+
𝑘
= 𝑆𝑓+
𝑘
, 𝑠−
𝑘
= 𝑆𝑓−
𝑘
, 𝑠0
𝑘
= 𝑆𝑓0
𝑘
,
𝜔+
𝑘
= 𝜔𝑓+
𝑘
, 𝜔−
𝑘
= 𝜔𝑓−
𝑘
, 𝜔−
𝑘
= 𝜔𝑓−
𝑘
,
(3)
where +, −, and 0 signs show nucleophilic, electrophilic, andradical attack, respectively.
The Fukui functions, local softnesses, and local elec-trophilicity indices for selected atomic sites in “Karanjin” havebeen listed in Table 7. The maximum values of all the threelocal electrophilic reactivity descriptors (𝑓+
𝑘
, 𝑠+
𝑘
, 𝜔+
𝑘
) at C7 and
10 Journal of Theoretical Chemistry
Table 7: (a) Fukui functions (𝑓+𝑘
, 𝑓−𝑘
), local softnesses (𝑠+𝑘
, 𝑠−𝑘
), and local electrophilicity indices (𝜔+𝑘
, 𝜔−𝑘
) for selected atomic sites of Karanjin,using the Mulliken population analysis at B3LYP/6-311G (d, p) level. (b) (All atomic sites.)
C2 indicate that this site is prone to nucleophilic attack, while,for electrophilic attack, C31 and C24 are found to be the mostactive sites.
In pentagonal ring A, carbon is replaced by oxygen whichhas the most electronegative lone pair antibonding electronwhich extracts electrons from the neighboring carbon havingthe positive charge. To cancel this positive charge, it attractsthe electron from C24 carbon. So C24 provides a betterelectrophilic site for the soft receptors. In hexagonal ring C,a carbon is replaced by oxygen having two lone pair anti-bonding electrons. Due to the repulsion of these antibondingelectrons, the shape of the ring gets distorted. Ring C hastwo substituent groups at para and meta positions. At metaposition, oxygen is attached to the ring C and at para positionO–CH
3
group is attached. Oxygen is more electronegativethan carbon which extracts electron from carbon. Due to thisreason, C31 carbon atom of methyl group is a better centerfor electrophilic substitution. In hexagonal ring C, electronwithdrawing groupO–CH
3
extracts electron fromC9 atomofthe ring C to fulfill the deficiency; C9 atom extracts electronfrom C7 atom and hence because of the C7 atom beingelectron deficient it extracts electron from O11 so C7 atombecomes a potential site for a nucleophilic attack.
4.11. Dipole Moment, Polarizability, Hyperpolarizability, andThermodynamic Properties. Dipole moment (𝜇), polarizabil-ity ⟨𝛼⟩, and total first static hyperpolarizability 𝛽 [41, 42]are also calculated (in Tables 5 and 8) by using densityfunctional theory.They can be expressed in terms of 𝑥, 𝑦, and𝑧 components and are given by following (4):
𝜇 = (𝜇2
𝑥
+ 𝜇2
𝑦
+ 𝜇2
𝑧
)
1/2
⟨𝛼⟩ =
1
3
[𝛼𝑥𝑥
+ 𝛼𝑦𝑦
+ 𝛼𝑧𝑧
]
𝛽Total = (𝛽2
𝑥
+ 𝛽2
𝑦
+ 𝛽2
𝑧
)
1/2
= [(𝛽𝑥𝑥𝑥
+ 𝛽𝑥𝑦𝑦
+ 𝛽𝑥𝑧𝑧
)
2
+ (𝛽𝑦𝑦𝑦
+ 𝛽𝑦𝑥𝑥
+ 𝛽𝑦𝑧𝑧
)
2
+ (𝛽𝑧𝑧𝑧
+ 𝛽𝑧𝑥𝑥
+ 𝛽𝑧𝑦𝑦
)
2
]
1/2
.
(4)
The 𝛽 components of Gaussian output are reported in atomicunits, where 1 a.u. = 8.3693 × 10−33 e.s.u. For Karanjin, thecalculated dipole moment value is 3.86 Debye. Having higherdipole moment than water (2.16 Debye), “Karanjin” can beused as better solvent. We see a greater contribution of 𝛼
𝑧𝑧
in molecule which shows that the molecule is elongatedmore towards 𝑍 direction and is more contracted to 𝑋
direction. Perpendicular part contributes with a less part ofpolarizability of molecule. 𝐵
𝑦𝑦𝑦
and 𝛽𝑦𝑦𝑧
contribute with alarger part of hyperpolarizability in the molecule. This showsthat 𝑌𝑍 plane and 𝑌-axis are more optically active in thesedirections. Standard thermodynamic functions such as freeenergy, constant volume heat capacity CV, and entropy 𝑆 havealso been calculated for “Karanjin” and are given in Table 9.These functions can provide helpful information for furtherstudy of the title compounds.
5. Conclusion
In this work, the compound “Karanjin” an anti-HIV drugwas experimentally isolated and identified and its bioactivityalong with detailed quantum chemical studies was carriedout. The optimized geometry of the “Karanjin” moleculehas been determined by the method of density functional
12 Journal of Theoretical Chemistry
theory (DFT). For both geometry and total energy, it hasbeen combined with B3LYP functional having 6-311 g (d,p) as the basis set. Using this optimized structure, we havecalculated the infrared wavenumbers and compared themwith the experimental data. The calculated wavenumbersare in an excellent agreement with the experimental values.On the basis of fully optimized ground-state structure,TDDFT//B3LYP/LANL2DZ calculations have been used todetermine the low-lying excited states of “Karanjin.” Reac-tivity reflects the susceptibility of a substance towards aspecific chemical reaction and plays a key role in, for example,the design of new molecules and understanding biologicalsystems and material science. Hyperpolarizability is mainlycontrolled by the planarity of the molecules, the donor andaccepter strength, and bond length alteration. The valuesof hyperpolarizability indicate a possible use of these com-pounds in electrooptical applications.We have also discussedglobal and local reactivity descriptors sites for bothmoleculesduring electrophilic, nucleophilic, and radical attacks. Thesevalues represent the qualitative descriptors of reactivity ofdifferent atoms in the molecule. This compound shows anti-HIV activity so these theoretical and experimental aspectscan provide a path for researchers in future.
Conflict of Interests
The authors of the paper have no conflict of interests in thepresent work.
Acknowledgment
The corresponding author Apoorva Dwivedi is grateful toProfessor Neeraj Misra for providing valuable suggestions.
References
[1] TheWealth of India—ADictionary of Indian RawMaterials, vol.8, Council of Scientific and Industrial Research, New Delhi,India, 2005.
[2] K. R. Kirtikar and B.D. Basu, IndianMedicinal Plants, vol. 1, 2ndedition, 1981.
[3] S. A. Dahanukar, R. A. Kulkarni, and N. N. Rege, “Pharmacol-ogy of medicinal plants and natural products,” Indian Journal ofPharmacology, vol. 32, no. 4, pp. S81–S118, 2000.
[4] G. P. Garg, “A new component from leaves of Pongamia glabra,”Planta Medica, vol. 39, no. 1, pp. 73–74, 1979.
[5] S. B. Malik, T. R. Seshadri, and P. Sharma, “Minort componentsof the leaves of pongamia glabra,” Indian Journal of Chemistry,vol. 14, pp. 229–230, 1976.
[6] P. Sharma, T. R. Seshadri, and S. K. Mukerjee, “Some synthesisand natural analogues of globrachromene,” Indian Journal ofChemistry, vol. 11, pp. 98/5–98/6, 1973.
[7] S. Rangaswamy and T. R. Seshadri, “Extraction and recovery ofkaranjin: a value addition to karanja (Pongamia pinnata) seedoil,” Indian Journal of Pharmacology, vol. 3, p. 3, 1941.
[8] B. S. Parmar and K. C. Gulati, “Synergists for pyrethrins (II)-karanjin,” Indian Journal of Entomology, vol. 31, pp. 239–243,1969.
[9] W. E. Sapna, T. C. Sindhu Kanya, A. M. Mamatha et al.,“Karanjin, a flavonoid inhibits lipoxygenases,” in Proceedings ofNational Academy of Science India, CFTRI, Mysore, India, 2007.
[10] P. Hohenberg and W. Kohn, “Inhomogeneous electron gas,”Physical Review, vol. 136, no. 3B, pp. B864–B871, 1964.
[11] A. D. Becke, “Density-functional thermochemistry. III.The roleof exact exchange,”The Journal of Chemical Physics, vol. 98, no.7, pp. 5648–5652, 1993.
[12] C. Lee, W. Yang, and R. G. Parr, “Development of the Colle-Salvetti correlation-energy formula into a functional of theelectron density,” Physical Review B, vol. 37, no. 2, pp. 785–789,1988.
[13] M. J. Frisch, G. W. Trucks, H. B. Schlegel et al., Gaussian 09,Gaussian, Pittsburgh, Pa, USA, 2009.
[14] P. L. Fast, J. Corchado, M. L. Sanches, and D. G. Truhlar,“Optimized parameters for scaling correlation energy,” TheJournal of Physical Chemistry A, vol. 103, pp. 3139–3143, 1999.
[15] A. Frisch, A. B. Nelson, and A. J. Holder, “Gauss View,” Pitts-burgh, Pa, USA, 2005.
[16] V. Vismaya, S. M. Belagihally, S. Rajashekhar, V. B. Jayaram, S.M. Dharmesh, and S. K. C. Thirumakudalu, “Gastroprotectiveproperties of karanjin from Karanja (Pongamia pinnata) seeds;Role as antioxidant and H+, K+-ATPase inhibitor,” Evidence-based Complementary and Alternative Medicine, vol. 2011, Arti-cle ID 747246, 10 pages, 2011.
[17] S. Sharma,M. Verma, R. Prasad, andD. Yadav, “Efficacy of non-edible oil seedcakes against termite (Odontotermes obesus),”Journal of Scientific and Industrial Research, vol. 70, no. 12, pp.1037–1041, 2011.
[18] R. Ranga Rao, A. K. Tiwari, P. Prabhakar Reddy et al., “Newfuranoflavanoids, intestinal 𝛼-glucosidase inhibitory and free-radical (DPPH) scavenging, activity from antihyperglycemicroot extract of Derris indica (Lam.),” Bioorganic and MedicinalChemistry, vol. 17, no. 14, pp. 5170–5175, 2009.
[19] V. Vismaya, W. Sapna Eipeson, J. R. Manjunatha, P. Srinivas,and T. C. Sindhu Kanya, “Extraction and recovery of karanjin:a value addition to karanja (Pongamia pinnata) seed oil,”Industrial Crops and Products, vol. 32, no. 2, pp. 118–122, 2010.
[20] J.-H. Wang, S.-C. Tam, H. Huang, D.-Y. Ouyang, Y.-Y. Wang,and Y.-T. Zheng, “Site-directed PEGylation of trichosanthinretained its anti-HIV activity with reduced potency in vitro,”Biochemical and Biophysical Research Communications, vol. 317,no. 4, pp. 965–971, 2004.
[21] D. Sajan, H. J. Ravindra, N.Misra, and I. H. Joe, “Intramolecularcharge transfer and hydrogen bonding interactions of nonlinearoptical material N-benzoyl glycine: vibrational spectral study,”Vibrational Spectroscopy, vol. 54, no. 1, pp. 72–80, 2010.
[22] V. Mukherjee, N. P. Singh, and R. A. Yadav, “FTIR andRaman spectra, DFT and SQMFF calculations for geometricalinterpretation and vibrational analysis of some trifluorobenzoicacid dimers,”Vibrational Spectroscopy, vol. 52, no. 2, pp. 163–172,2010.
[23] M. Hariharan and S. S. Rajan, “Crystal structure communica-tions,” Acta Crystallographica C, vol. 46, pp. 437–439, 1990.
[24] M. Alcolea Palafox, G. Tardajos, A. Guerrero-Martınez et al.,“FT-IR, FT-Raman spectra, density functional computations ofthe vibrational spectra and molecular geometry of biomolecule5-aminouracil,” Chemical Physics, vol. 340, no. 1-3, pp. 17–31,2007.
[25] J. S. Singh, “FTIR and Raman spectra and fundamental fre-quencies of biomolecule: 5-Methyluracil (thymine),” Journal ofMolecular Structure, vol. 876, no. 1–3, pp. 127–133, 2008.
Journal of Theoretical Chemistry 13
[26] C. P. Beetz Jr. and G. Ascarelli, “The low frequency vibrations ofpyrimidine and purine bases,” Spectrochimica Acta A:MolecularSpectroscopy, vol. 36, no. 3, pp. 299–313, 1980.
[27] J. Bandekar and G. Zundel, “The role of CO transition dipole-dipole coupling interaction in uracil,” Spectrochimica Acta A:Molecular Spectroscopy, vol. 39, no. 4, pp. 337–341, 1983.
[28] K.-C. Chou, “Biological functions of low-frequency vibrations(phonons). III. Helical structures and microenvironment,” Bio-physical Journal, vol. 45, no. 5, pp. 881–889, 1984.
[29] H. Frohlich, Biological Coherence and Response to ExternalStimuli, Springer, Berlin, Germany, 1988.
[30] D. F. V. Lewis, C. Loannides, and D. V. Parkee, “Interactionof a series of nitriles with the alcohol-inducible isoform ofP450: computer analysis of structure-activity relationships,”Xenobiotica, vol. 24, pp. 401–408, 1984.
[31] Z. Zhou and R. G. Parr, “Activation hardness: new index fordescribing the orientation of electrophilic aromatic substitu-tion,” Journal of the American Chemical Society, vol. 112, no. 15,pp. 5720–5724, 1990.
[32] I. Fleming, Frontier Orbitals and Organic Chemical Reactions,John Wiley & Sons, New York, NY, USA, 1976.
[33] M. Bohl, K. Ponsold, and G. Reck, “Quantitative structure-activity relationships of cardiotonic steroids using empiricalmolecular electrostatic potentials and semiempirical molecularorbital calculations,” Journal of Steroid Biochemistry, vol. 21, no.4, pp. 373–379, 1984.
[34] D. F. Lewis and V. Griffiths, “Molecular electrostatic potentialenergies and methylation of DNA bases: a molecular orbital-generated quantitative structure-activity relationship,” Xenovi-otica, vol. 17, pp. 769–776, 1987.
[35] A. Kumar and P. C. Mishra, “Structure-activity relationships forsome anti-HIV drugs using electric field mapping,” Journal ofMolecular Structure, vol. 277, pp. 299–312, 1992.
[36] R. G. Pearson, “Absolute electronegativity and hardness: appli-cations to organic chemistry,” Journal of Organic Chemistry, vol.54, no. 6, pp. 1423–1430, 1989.
[37] R. G. Parr, L. V. Szentpaly, and S. Liu, “Electrophilicity Index,”Journal of theAmericanChemical Society, vol. 121, pp. 1922–1924,1999.
[38] P. K. Chattaraj and S. Giri, “Stability, reactivity, and aromaticityof compounds of a multivalent superatom,” Journal of PhysicalChemistry A, vol. 111, no. 43, pp. 11116–11121, 2007.
[39] J. Padmanabhan, R. Parthasarathi, V. Subramanian, and P. K.Chattaraj, “Electrophilicity-based charge transfer descriptor,”Journal of Physical Chemistry A, vol. 111, no. 7, pp. 1358–1361,2007.
[40] P.W. Ayers and R. G. Parr, “Variational principles for describingchemical reactions: the Fukui function and chemical hardnessrevisited,” Journal of the American Chemical Society, vol. 122, no.9, pp. 2010–2018, 2000.
[41] D. A. Kleinman, “Nonlinear dielectric polarization in opticalmedia,” Physical Review B, vol. 126, no. 6, pp. 1977–1979, 1962.
[42] J. Pipek and P. G. Mezey, “A fast intrinsic localization procedureapplicable for ab initio and semiempirical linear combination ofatomic orbital wave functions,”The Journal of Chemical Physics,vol. 90, no. 9, pp. 4916–4926, 1989.
