General characters
1. Widely distributed in higher plants.
2. Bitter, acrid taste & sternutatory (irritant to mucous
membranes).
3. Form colloidal solutions in H2O foam on shaking
due to: hydrophobic / hydrophilic asymmetry of the
molecule (large aglycone & small sugar moiety)
lowering of surface tension in aqueous solution.
4. Form insoluble complex with sterols.
Destroy RBCshaemolysis.
Toxic to cold- blood animals (fishes & frogs).
Toxic by i.v. injection & harmless by oral route.
Chemical characters
1. O-glycosides hydrolysis aglycone(sapogenin) + sugar moiety.
2. Aglycone:
– triterpenoidal (C-30) [mainly in Dicotyledons]
– steroidal (C-27) [mainly in Monocotyledons]
3. Sugar moiety:
– Often contain uronic acids or acyl residues.
– Usually glycosylation is at C-3.
– Sometimes -CH3 (side chain) -COOH, whichmay be esterified by a sugar.
Isolation
1. Plant material + water, alcohol or aqueous
alcohol + reflux.
2. Concentrate & precipitate crude saponin
mixture with:
– Ether or acetone.
– Lead acetate (acidic saponins), or basic lead
acetate (neutral saponins) followed by
decomposition with acid.
3. Individual glycosides are separated by
chromatography.
Economical & Medicinal importance
Economical uses
1. Cleaning industrial equipment & fine fabrics.
2. Powerful emulsifier.
3. Steroidal sapogenins used in semisynthesis of
cortisone & sex hormones.
Medicinal uses
1. Expectorant
2. Immunostimulant
3. Control of schistosomiasis snails
4. Hypoglycemic (saponins of Balanites aegyptiaca ,
Egyptian date-sugar)
Tests for identification
1. Froth test:
1 ml of aqueous solution of saponin or plant
extract + shake persistent & voluminous
froth.
2. Haemolysis test:
Suspension of RBCs in normal saline + equal
volume of plant extract in normal saline +
shake gently clear red solution indicating
heamolysis of RBCs (compared with blank ).
Quantitative Determination1.Gravimetric method
– Saponin glycosides + Ba(OH)2 precipitate [Saponin-Ba(OH)2complex]
– Filer, dry & weigh the precipitate original weight {W1}
– Ignite & weigh the residue {W2} (calculated as BaO)
– W1 - W2 = Saponin content
2.Determination of Foam Index
– The foam index is defined as:
“ The dilution of the drug, that gives a layer of foam of 1 cmheight, when an aqueous solution is shaken in a graduatedcylinder for 15 seconds after standing for 15 min.”
3.Determination of Fish Index
– Saponins are toxic to cold blooded animals.
– The fish index is defined as:
“The reciprocal of the saponin dilution that kills 60 % of theexperimental animals within 1 hour.”
4.Determination of Haemolytic Index
– The heamolytic index is defined as:
“The greatest dilution of saponin that produces completehaemolysis.”
Steroidal saponins-
Balanites saponins (Balanitins 1-4)Chemistry
Steroidal saponin glycosides.
Aglycone: yamogenin (furanostane
type).
Source
Fruits & bark of Balanitesaegyptiaca : Balanitins 1-4 &
balanitoside.
Uses
Hypoglycemic, anticancer &
molluscicidal
Balanites aegyptiaca
Fruits
Triterpenoidal Saponins -
Licorice saponins
Source
Rhizomes & roots of licorice: 2-6 % of Glycyrrhizin
Structure
Glycyrrhizic acid = Glycyrrhetic
acid -3 O- diglucuronide (2 molecules
of glucuronic acid)
Glycyrrhetic acid Glycyrrhetinic acid
Glycyrrhizic acid Glycyrrhizinic acid
HO
COOH
Glycyrrhetic acid(aglycone)
O
3
Glycyrrhizin = mixture of K+ & Ca++ salts of Glycyrrhizic acid
Major non-saponin constituents of Licorice
Flavonoid glycosides: major liquiritin (flavanone).
Coumarins: herniarin & umbelliferone.
Others: asparagine, dihydrostigmasterol, glucose,
mannitol & starch.
Licorice - Uses1. Expectorant & demulcent by stimulation of tracheal mucous
secretion due to glycyrrhizin.
2. Antiinflamatory & adrenocorticotropic activity due to steroidal-like activity of glycyrrhizin &/or glycyrrhetic acid.
3. Antihepatotoxic, antibacterial, antirheumatic, antitumour &antiviral.
4. Used in treatment of gastric & duodenal ulcers by increasing therate of healing of gastric mucosa mainly due to liquiritin.
DGL = licorice preparation with very low % of glycyrrhizin (< 1 %)used as antiulcer for hypertensive patients.
5. Used in laxative formulations to facilitate absorption ofanthraquinone glycosides due to surfactant properties ofsaponins.
6. Used as sweetener (glycyrrhizin 50 times > sweet than sucrose)& as flavoring agent to mask the bitter taste of some drugs asaloe, quinine & others.
Ginseng saponinsSource
Roots of Panax quinquefolius (American
ginseng) & P. ginseng (Asian ginseng),
Araliaceae.
Contains a complex mixture of
triterpenoidal saponins with a tetracyclic (steroids) or pentacyclic structure
Classification
Classified into 3 types:
1. Ginsenosides,
2. Panaxosides
3. Chikusetsusaponins.Aerial partsRoots
Ginseng saponinsGinsenosides
1. Major saponins of ginseng (0.7-3 % calculated asginsenosides).
2. Aglycones of most ginsenosides have a tetracyclicsteroidal structure. They are glycosides of:
20 (S)-protopanaxadiol: aglycone of ginsenosidesRb1, Rb2, Rc, & Rd. Rb1 is the major.
20(S)-protopanaxatriol: aglycone of ginsenosidesRe, Rf, Rg1, Rg2 & Rh1. Rg1 is the major.
3. Ginsenoside Ro is an exception, being a triglycoside ofthe pentacyclic triterpene (oleanolic acid).
Ginsenosides
HOR2O
HO
CH3
O R1
HOR2O
R1O
CH3
20(S)-Protopanaxadiols 20(S)-Protopanaxatriols
Ginsenoside R1 R2
Rb1 -glc (2-1)glc -glc (6-1)glcRb2 -glc (2-1)glc -glc (6-1)arabRc -glc (2-1)glc -glc (2-1)arabRd -glc (2-1)glc -glc
Ginsenoside R1 R2
Re -glc (2-1)rha -glc Rf -glc (2-1)glc -HRg1 -glc -glc Rg2 -glc (2-1)rha -H
Ginseng -Therapeutic uses1. Tonic, stimulant, diuretic & carminative.
2. Adaptogenic (antistress): enhances bodynonspecific resistance to external stress (physical,chemical or biological).
3. Improves physical & mental performance e.g.learning, memory & physical capabilities.
4. Improves immune function & metabolism.
5. Used in anemia, diabetes, insomnia, neurasthenia,gastritis & sexual impotence.
6. Contraindicated in case of hypertension & duringpregnancy.
Cyanogenetic glycosides
N.B. Cyanogenic = Cyanogenetic= Cyanophore
Introduction
O-glycosides hydrolysis HCN gas.
Present in over 3000 plant spp. (110 families).
In plants, cyanogenic glycosides & their hydrolytic
-glycosidase enzymes are present in different
cellular compartments.
Cyanogenesis: is a chemical defense mechanism
protecting plants against damaging organisms by
release of toxic HCN gas
Cyanogenic glycosides-Structure
-hydroxynitrile derivatives = cyanohydrins.
Fairly unstable, stabilized by -D-linked sugar
chains with -D-glucose as first sugar
attached to the aglycone.
R1 & R2 are often differentpairs of epimers.
C
R2sugar-O
R1
CN
General structure of cyanogenic glycosides
Cyanogenic glycosides vs. non-
cyanogenic nitriles
Non-cyanogenic nitriles :
1. Glucosides of - & -hydroxynitriles.
2. On hydrolysis: do not yield free HCN except under
specific conditions.
Examples: cyanolipids (esters of fatty acids with
- & -hydroxynitriles) & Simmondsin
OCH3
OCH3
OOH
NC H
O
HOHO
OH
HO
O (CH2)nCH3
O
HNC
Non-cyanogenic nitrile compounds
SimmondsinCyanolipid
Cyanogenic glycosides-Amygdalin
SourceKernels of peaches, apricots (Prunus
armeniaca) & bitter almond seeds(Prunus amygdalus var. amara)[Rosaceae] .
HydrolysisAmygdalin + emulsin enzyme (mixture of 3
enzymes:
Amygdalin hydrolase + prunasin hydrolase +
mandelonitrile lyase) benzaldehyde +HCN + 2 glucose.
UsesPreparation of benzaldehyde (volatile oil of
bitter
almond)
Peaches
C
O
CN
Glc-(1 - 6)-Glc
H
(gentiobiose)
Amygdalin
Amygdalin- hydrolysis
CO
CN
Glc-(1 - 6)-Glc
CO
CN
Glc
C
HO
CNCHO
HCN
+ Glucose
Mandelonitrile
PrunasinAmygdalin
Benzaldehyde
hydrolyase
Prunasin hydrolyase
Mandelonitrile lyase
H
H H
(Gentiobiose)
Amygdalin
+ Glucose+
(Volatile oil of bitter almond)
Cyanogenic glycosides-Linamarin
Source
Seeds of Linum usitatissimum, (Linseed, Flaxseed,
Linaceae), Lotus arabicus & in lima beans.
Hydrolysis
Linamarin acetone cyanohydrin ( acetone + HCN) +
glucose
H3C
CH3
C
O
CN
Glc
Linamarin
Linseed
Glucosinolates-General characters
Common in Cruciferae (mustard family), Capparidaceae,
Resedaceae & Liliaceae.
Bound toxins like cyanogenetic glycosides.
Found in plants with specific hydrolytic enzymes
(thioglucosidases= myrosinases).
Characterized by presence of:
1. One S atom attached to glucose S-glycoside
2. Another S atom present as a sulfonated oxime group.
Aglycones: aliphatic or aromatic formed from amino acids.
Members of family Brassicaceae ( = Cruciferae) are rich in
glucosinolates:
1. Oilseeds e.g. rapeseed
2. Condiments e.g. mustard & horseradish
3. Vegetables e.g. broccoli, cabbage & turnips
Glucosinolates = Thioglycosides = Isothiocyanate glycosides
Pharmacological action & uses1. Play an important role as
feeding deterrent against
insects & mammals.
2. Anticarcinogenic.
3. Improve flavor of foods.
Rape Black mustard Horse radish Turnip
Broccoli
Cabbage
Glucosinolates - Sinigrin
Source
Seeds of Brassica nigra (black mustard) [Brassicaceae]
Properties
Sharp odor & biting taste.
Hydrolysis
Sinigrin + myrosinase enzyme allylisothiocyanate (volatile oil of mustard) + KHSO4 + glucose.
Uses
1. Internally: emetic.
2. Externally: local irritant, rubefacient & vesicant.
3. Commercially: condiment.
H2C CH
CH2
C
N-O-SO3K
S-Glc
S C N
H2
C
CH
CH2 KHSO4+ Glucose+
myrosinase
allylisothiocyanateSinigrin
Glucosinolates - Sinalbin
Source
Seeds of Brassica alba (white mustard), Brassicaceae.
Hydrolysis
Uses: Condiment
H2O
MyrosinaseSinalbin p-Hydroxybenzyl isothiocyanate + Sinapine acid sulfate + Glucose
Slightly volatile
& pungent
Non-glycosidic organo-sulfur drugs- Alliin
Source & decomposition
Bulb of Allium sativum (Fam. Liliaceae)
Food & traditional medicine since Pharaohs.
Intact cells of garlic contain Alliin (1.2 % in fresh garlic).
Alliin + crushing (allinase enzyme) Allicin (diallyl
thiosulfinate).
Allicin is responsible for the characteristic odor & flavor of
garlic.
Allicin + air + water diallyl disulfide + diallyl trisulfide +
polysulfides (All strong smelling).
Uses: Allicin is used as antibacterial, antihyperlipidemic; inhibits
platelet aggregation & enhances the blood fibrinolytic (anti-
thrombic) activity.
SH
O
NH2
COOH SS
O
Allinase+ H2O
Alliin Allicin