Detailed study of Glycosides including its Definition, properties, types, classification, isolation/extraction

1. GLYCOSIDES: Definition,
classification, properties and test for
identification

2. DEFINITION:
• It may be defined as the organic compounds
from plant or animal sources which on
enzymatic or acid hydrolysis gives one or more
sugar and non- sugar moiety.
Glycosides
enzymatic hydrolysis/ Acid hydrolysis
Sugar part (glycone) + Non-sugar part (Aglycone or
genin)

3. OR
• Chemically:
• Glycosides are the acetals or sugar ether
formed by interaction of OH group each of
sugar and non- sugar moiety with the loss of
water molecules.
• Sugar (OH) + Non-sugar (OH) (it can ne
alcoholic or phenolic)
Acetals or sugar

4. • A substance containing a glycosidic bond is a
glycoside. The sugar group is known as the glycone
and the non- sugar group as the aglycone or genin
part of the glycoside.
• Aglycone part is responsible for therapeutic activity
and glycone part helps in the transportation of
glycosides at the site of action.
• The glycone can consist of a single sugar group
(monosaccharide) or several sugar groups
(oligosaccharide).

5. • Sugar moieties in glycosides: The sugars found
in glycosides are glucose and rhamnose
(monosaccharides), mannose, digitoxose and
cymarose found in cardiac glycosides.

6. PROPERTIES:
• Crystalline and amorphous substances
• Soluble in water and dilute alcohol and
insoluble in organic solvents like benzene and
ether. The exception is resin glycosides.
• The aglycone part is soluble in organic solvents
like benzene or ether.
• They are optically active.
• Participate in growth regulation and protection
of plant.

7. • CLASSIFICATION
1. On the Basis of Glycosidic Linkage between
glycone and Aglycone part
2. On the basis of chemical nature of Aglycone
part or therapeutic activity.

8. 1. On the Basis of Glycosidic Linkage between
glycone and Aglycone part
1. O-glycosides: Sugar molecule is combined with
phenol or –OH group of Aglycone.
Glycone (OH) +HO- Aglycone
-H2O
glycone- O- aglycone
• These are hydrolysed by treatment with acid or
alkali.
• Examples: Senna and Rhubrb

9. 2. N-glycosides: Sugar molecule is combined with N of the
–NH (amino group) of aglycone.
Glycone (OH) +HN- Aglycone glycone- N- aglycone
for example, nucleosides
3. S-glycosides: Sugar molecule is combined with the S or
SH (thiol group) of aglycone,
• Glycone (OH) +HS- Aglycone glycone- S- aglycone
for example, Sinigrin (from black mustard)

10. 4. C-glycosides: Sugar molecule is directly
attached with C—atom of aglycone.
Glycone (OH) +HC- Aglycone glycone- C-
Aglycone
These are hydrolysed by hydrolysis with ferric
chloride.
for example, Anthraquinone glycosides like Aloin,
Barbaloin, Cascaroside and Flavan glycosides, etc.

11. 2. On the Basis of Aglycone
• The various classes according to aglycone
moiety are given below:

13. CHEMICAL TESTS OF GLYCOSIDES
• The aqueous or alcoholic extracts of crude drugs are tested with
specific reagents for presence of various types of glycosides.
1. Chemical Tests for Anthraquinone Glycosides
Borntrager’s test
• 1 gm of drug + 5–10 ml of dilute HCl
• boil on water bath for 10 min and filter
• Filtrate was extracted with CCl4/ benzene and add equal amount of
ammonia solution to filtrate and shake separate the organic layer,
• Formation of pink or red colour in ammonical layer due to presence of
anthraquinone moiety.

14. Modified borntrager’s test
• 1 gm of drug + 5 ml dilute HCl + 5 ml ferric Chloride (5%
w/v)
• Boil for 10 min on water bath, cool and filter, filtrate was
extracted with carbon tetra-chloride or benzene and add
equal volume of ammonia solution
• formation of pink to red colour due to presence of
anthraquinone moiety.
• Modified borntrager’ s test is carried out for the
detection of C-glycoside because these are resistant to
simple acid hydrolysis.

15. 2. Chemical Tests for Saponin Glycosides
• Haemolysis test
A drop blood on slide was mixed with few drops
of aqeous Saponin solution, RBC’s becomes
ruptured in presence of saponins.
• Foam test
To 1 gm of drug add 10–20 ml of water, shake for
few minutes, formation frothing which persists
for 60–120 s in presence of saponins.

16. 3. Chemical Tests for Cardiac Glycosides
• Keller-kiliani test : for detection of deoxy sugars.
• alcoholic extract of drug + 3 ml of glacial acetic acid + few
drops of FeCl3 solution + Conc. H2SO4
• Reddish brown layer is formed, which turns bluish green
after standing due to presence of digitoxose.
• Legal test
• alcoholic extract of drug + 2 ml of pyridine + sodium
nitropruside 2 ml was added followed by addition of
NaOH solution to make alkaline
• Formation of pink colour in presence of glycosides or
aglycone moiety.

17. • Baljet test
• Drug + sodium picrate solution, it forms yellow
to orange colour in presence of aglycones or
glycosides.

18. 4. Chemical Tests for Coumarin Glycosides
• FeCl3 test
alcoholic extract of drug + few drops of alcoholic
FeCl3 solution was added. Formation of deep green
colour, which turned yellow on addition of conc.
HNO3, indicates presence of coumarins.
5. Chemical Tests for Flavonoid Glycosides
Shinoda test
• 1. alcoholic extract of drug + 5ml 95% ethanol + +
few strips of magnesium turning and dil. HCl was
added, formation of pink colour indicates the
presence of flavonoids.

19. • EXTRACTION/ISOLATION
• Stas-Otto Method
drug containing glycoside
finely powdered
• Extracted by continuous hot percolation using
soxhlet apparatus with alcohol (various enzymes
present in plant parts deactivated due to heating.
The thermolabile glycosides should be extracted
at temperature below 45°C.)
Extract

20. treated with lead acetate( to precipitate tannins and
thus eliminate non-glycosidal impurities)
Pass H2S gas
(excess of lead acetate is precipitated as lead
sulphide by passing hydrogen sulphide gas through
solution)
The extract is filtered,
concentrated

21. • crude glycosides
• Purification
(by fractional solubility, fractional crystallization
and chromatographic techniques such as
preparative thin layer and column
chromatography)
characterization of isolated purified compounds
(by IR, UV, NMR and mass spectrometry)