2. Glycosides
Definition:
Glycoside are compounds which upon
hydrolysis give rise to one or more sugar
(glycone) and a compound which is not a sugar
(aglycone). In a glycosidic compound a sugar
residue is linked to (C-1) through oxygen (O-
glycoside),Nitrogen (N- glycoside) or Sulphur
(S-glycoside) moiety.
4. Glycosides
Characters:
i. Most of the glycoside are colorless, crystalline
compounds.
ii. Anthracene glycosides are red or orange colored
compounds and flavone glycoside are yellowsits in
color.
iii. They are soluble in water and alcohol but
insoluble in organic solvent like petroleum ether,
chloroform, carbon tetra chloride etc.
iv. Glycosides are optically levorotatory.
5. Glycosides
Classification:
On the basis of linkage of sugar molecule to aglycone
glycoside are divided as,
i. Oxygen glycosides: In these glycosides the sugar
combinds with alcoholic or phenolic hydroxyl
function of aglycones.
e.g: Digitoxin
ii. Nitrogen glycosides: In these glycosides
Nitrogen of amino group is condensed with a
sugar.
e.g: Nucleoside
6. Glycosides
iii. Sulphur glycoside: In these glycoside a sugar
moiety attached to a sulfur of the aglycone.
e.g: Isothiocyanat glycosides.
iv. Carbon glycoside: Condension to a carbon atom
gives rise to carbon glycoside.
e.g: Aloin, Cascaroside etc
7. Glycosides
#Classification on the basis of chemical nature:
i. Steroidal glycosides: These glycoside contain a sterol
as an aglycone.
e.g: Diosgenin
ii. Flavanoid glycosides: A flavanoid aglycone is
present in this glycosides.
e.g: Rutin
iii. Anthracene glycosides: In these glycosides sugar
moiety is attached to an anthracene agycone.
e.g: Barbaloin, frangulin
8. Glycosides
iv. Cyanophoric glycosides: Cyanogen is the
aglycone part. They eyld hyrocyanic acid on
hydrolysis.
e.g: Amygdalin, Paunasin
v. Triterpenic glycosides: A triterpenic molecule is
condence with a sugar component.
e.g: Glycyrrhizin
vi. Alcohol glycosides:e.g: Salicin
vii. Lactone glycosides:e.g: Hydroxy coumarin
viii. Isothiocyanate glycosides:e.g: sinigrin, sinalbin
ix. Saponin glycosides:e.g: Dioscin
9. Glycosides
Saponin glycosides
Saponin are highly complex glycosides. Which are
widely distributed in the higher plants, saponins from
coloidal solution in water. Which give a soap like forth
on shaking. They have the property of causing
hemolysis of RBC, event at great dilution. On
hydrolysis they yield and aglycone known as
sapogenin. They have high molecular wait and are
purified with deficalty.
e.g: Senega, Guillaia.
10. Glycosides
Cardiac glycosides
These are steroidal glycosides and show highly specific
and powerful action upon the cardiac muscle. The
sugar part is attached at carbon-3(C-3) of the steroidal
nucleus.
The steroid aglycone are of two types:
i. Cardenolides:
Which are C23 steroids having α,β unsaturated five
membered lactone ring at 17β position.
11. Glycosides
ii. Bufedienolides:
Which are C24 steroids having double unsaturated six
membered lactone ring at 17α position
Cardiac glycosides increase the force of systolic
contraction and decrease the heart rate.
12. Glycosides
Pharmaceutical uses of glycosides:
i. Cardiac glycosides are used as cardiac stimulant.
e.g: Digitoxin, Stropanthus, Squill digoxin.
ii. Anthraquinone glycosides: Exert laxative effect.
e.g: Senna, Aloe, Cascara etc.
iii. Singrin glycosides: A glycoside from black
mustered, upon hydrolysis yield alyisothiocyanate that
act as powerful local irritant.
13. Glycosides
iv. Glycoside has analgesic properly.
v. Glycoside used as bitter tonic and protect the
damage of the liver.
vi. Glycosides has expectorant property.
14. Glycosides
Chemical test used to detect glycoside:
i. Killer-killiani-test: To an extract of the drug in
glacial acitic acid few drops of Ferric chloride(Fecl3)
and concentrated H2SO4 are added a reddish brown
colour is fromed and the junctions of two layers and the
uper layer turns bluish green. This test indicates the
presence of glycosides.
15. Glycosides
ii.Borntrager test: Leabs are boiled with dilute
sulphuric acid filtered, the filtered is extreated with
chloroform or ether. On addition of ammonia in organic
phage pink red color is formed due to the presence of
anthaquinon glycosides
iii. A little drug extracts treated with 5N sodium
hydroxide and sodium hyposulphite. On heating red
color appears.
