Glycosides, Introduction to glycosides, Types of glycosides, Properties of glycosides, general extraction process of glycosides

1. Glycosides
Prepared by,
Ms. M.S. Divya Sree,
Assistant Professor,
Department of Pharmacognosy,
Sree Vidyanikethan College of Pharmacy,
Tirupati, Andhra Pradesh

2. Definition
 Organic natural compounds present in a lot of plants
and some animals, these compounds upon hydrolysis
give one or more sugars (glycone) moieties and non
sugar (aglycone) moiety.
 Glycoside = sugar group + nonsugar group
(glycone) (aglycone or genin)
 Glycone and aglycone are linked by glycosidic linkage

3.  Glycosidic linkage is formed between –OH group of
sugar and –H group of non sugar moieties or other sugar
with loss of water molecule.
Glycoside bond
glycoside= glycone {---o---} aglycon
 The sugars involved in glycosides are of different types
but most commonly it is β - D-glucose.
 The other sugars found are galactose, mannose,
rhamnose, digitoxose, cymarose etc.

4. • Glycosides can be alpha or beta but plants contains
only beta glycosides.
α- glycoside (α-sugar) and β-glycosides (β-sugar).

5. • Therapeutic effect of glycosides is only due to aglycon
part and sugar moiety facilitate absorption of glycoside,
transportation of aglycone to site of action.
• So glycosides are hydrolysed to give aglycon part for
action.
• Glycosides have therapeutic effect in human and
animals, so they are used in traditional and modern
medicines as cardio tonic, purgative, analgesic, anti-
rheumatic, demulcent and many other uses.

6. Classification
1. Classification based on type of aglycone in
glycoside.
2. Classification based on type of sugar (glycone)
part.
3. Classification based on type of linkage between
glycone and aglycone.
4. Classification based on there use

7. Classification based on type of aglycone in
glycoside
 Anthraquinone or anthracene glycoside
 Sterols or cardiac glycoside
 Saponin glycoside
 Cyanogenic glycoside
 Isothiocynate glycoside
 Coumarins and furanocoumarins
 Aldehyde glycoside
 Phenol glycoside
 Steroidal glycoside
 Miscellaneous glycosides

8. Classification based on type of
sugar (glycone) part
 Glucose - glucoside
 Rhamnose – rhamnoside
 Digitoxose - digitoxoside
 Glucose and rhamnose - glucorhamnoside
 Rhamnose and glucose - rhamnoglucoside

9. Classification based on type of linkage
between glycone and aglycone
Linkage between –OH group and –H group of
RADICALS like –CH,-OH,-SH,-NH of glycoside is named by
perfix like
o C-glycoside, - sugar linked to carbon atom of aglycone
o N-glycoside, - sugar linked to nitrogen atom of aglycone
o O-glycoside, - sugar linked to oxygen atom of aglycone
o S- glycoside - sugar linked to sulfur atom of aglycone

10. Classification based on their use
• Cathartics.
• Cardio tonics.
• Analgesics.
• Anti-rheumatics.
• Anti-ulcer etc

11. Properties
 Colorless, solid, amorphous, non-volatile
( flavonoid- yellow, anthraquinone - red or
orange.)
 Give positive reaction with Molisch's and
Fehling's solution test (after hydrolysis).
 Most of them have bitter taste.
(except: populin, glycyrrhizin, stevioside)

12.  Odorless except saponin (glycyrrhizin).
 When a glycosides has a lot of sugars its
solubility in water increases.
 Glycosides hydrolyzes by using mineral acids
and temperature or by using enzymes.

13. Solubility
 Glycosides are water soluble compounds and
insoluble in the organic solvents.
 Glycone part: water soluble, insoluble in the
organic solvents.
 Aglycone part: water insoluble, soluble in the
organic solvents.
 Some glycosides soluble in alcohol.

14. General extraction method
Stas-otto method
The drug containing glycoside is finely
powdered and subjected to successive
extraction in a soxhlet apparatus with
alcohol or suitable solvent.

15.  After extraction collect the extract and treat with
lead acetate to precipitate tannins.
 After that filter it and to the filtrate pass H2S gas,
to precipitated excess of lead acetate which
converts to precipitate of lead sulphide.
 Filter it to remove lead sulphide.

16.  The filtrate is subjected to fractional
crystallization, distillation or chromatography to
obtain pure component.
 And molecular structure of component is
determined by the spectrophotometer, Infra red ,
NMR , mass spectroscopy etc.