SECONDARY METABOLITIES Glycosides

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

4. Introduction
• Naturally occurring organic compounds
• Found in both plants and animals
• On hydrolysis (by acids or enzymatic) gives one
or more sugar moiety (glycone) and non-sugar
moiety (aglycone).
• Non-sugar (aglycon) called genin.
• The pharmacological acivity is due to the
presence of genin part.
• Glycone part facilitates the transportation of
genin to the site of action.

5. Glycosides Definition
These are the organic compounds
obtained from the plants or animals
sources which on enzymatic or acid
hydrolysis gives one or more sugar
moieties along with non-sugar
moiety.

6. Glycosides
Enzymatic or acid hydrolysis
Sugar moieties(glycone) Non-sugar moiety
(aglycone or genin)

8. • The sugar involved in glycosides are of
different types, but most commonly, it is β-D
glucose. Other are galactose, mannose,
rhamnose, digitoxose, cymarose, etc.
• The linkage between glycone & aglycone is
called glycosidic linkage.

9. Properties of Glycosides
• They are colourless, amorphous, solid, non-volatile
compounds.
• They give a positive test with Molisch’s and Fehling’s
solution test.
• They have solubility in water but are insoluble in organic
solvents.
• Most of them possess bitter taste but some exceptions are
populin, glycyrrhizin, stevioside.
• They are odourless compounds except for saponin
(glycyrrhizin).
• Glycosides get hydrolyzed by mineral acids and
temperature or by enzymes like (a) Emolsin: Bitter
almond seeds. (b) Myrosin or Myrosinase: Black
mustard seeds. (c) Rhamnase: Glycosides containing
rhamnose as sugar part.

10. Types
1. Based on atoms involved in glycosidic linkage
• O- glycosides
• C- glycosides
• S- glycosides
• N- glycosides
2. According to chemical nature of aglycone part
• Cardiac/sterol glycosides- Digitalis, indian squill, strophanthus,
• Anthracene(Anthraqunone) glycosides- Senna, rhubarb,aloe,
cascara
• Cyanogenetic glycosides- Bitter almond, white cherry bark,
• Saponin glycosides- Dioscorea, liquorice, Ginseng,sersaparilla
• Isothiocynate glycosides- Black mustard

11. 1. According to linkage existing b/w
the glycone and aglycone
• All types of glycosidal linkages are occurred
by interaction of –OH group of glycone and
hydrogen coming through any of the radicals
like –CH, -OH, -SH, and –NH present on
aglycone part. Hence, by elimination of one
water molecule, linkage or a bridge is formed
and the type of glycoside formed.

12. 1. C-gylcosides
• Some of the anthraquinone glycosides such as
Cascarosides from Cascara and aloin from aloe,
as well as some member of flavone type of
glycosides show the presence of C-glycoside.
Glycone--OH+ HC--aglycone
Glycone--C--aglycone + H2O
• They are not hydrolysed by heating with dil.
Acid/alkalies but by oxidative hydrolysis with
ferric chloride.

13. 2. O-glycosides
• Common in higher plants.
• Examples-Senna, rhurbarb, etc
• They are hydrolysed by treatment of acid or alkali
into aglycone and sugar.
Glycone--OH+HO—aglycone
Glycone--O--aglycone
+
H2O

14. 3. S-glycosides
• Restricted to isothiocynate glycoside like-Sinigrin
from black mustard.
• They are formed by interaction of sulfahydryl
group of aglycone and hydroxide group of
glycone
Glycone--OH+HS—aglycone
Glycone--S--aglycone
+
H2O

15. 4. N-glycosides
• N-glycosides are nucleosides.
• The glycosides contain sugar but still the physical,
chemical and therapeutic properties are given by
aglycone part.
• Examples-Adenosine- antiarrythmic, yeast nucleic
acid- brewer's yeast (nutrient supplement).
Glycone--OH+HN--aglycone
Glycone--N--aglycone
+
H2O

16. GENERAL MTHOD OF EXTRACTION OF
GLYCOSIDES
Stas-Otto Method
• The drug containing glycoside is finely powdered and the powder is
extracted by continuous hot percolation using soxhlet apparatus with
alcohol as solvent.
• Various enzymes-deactivate due to heating.
• The thermolabile glysosides-Anthocyanins, however, should be
extracted at temperature preferably below 45 degree centigrade
• The extract is treated with lead acetate to precipitate tannins and thus
eliminating non-glycosidal impurities.
• The excess of lead acetate is precipitate as lead sulphide by passing
hydrogen sulphide gas through solution
• The extract is filtered, concentrated to get crude glycosides.
• From crude extract, the glycosides are obtained in pure form by
making use of processes like fractional solubility, fractional
crystallization and chromatography techniques such as preparative
thin layer and column chromatography.

17. Soxhlet setup

19. Anthracene Glycosides
• These constitute a major class of glycoside.
• They are mainly found in the dicot plant and
families like- Euphorbiaceae, Ericaceae,
Polygonaceae, Rhamnoceae, Rubiaceae,
leguminosae, Verbenaceae, etc.
• This group of glycosides comprises of different
aglycosides moieties like-anthraquione,
anthrone, anthranol, dianthranol and
dianthrone.

20. Anthracence derivatives

21. General tests:
(1) Antimony trichloride test: An alcoholic extract of drug →evaporate
→ dry → make extract with chloroform + saturated solution of
antimony trichloride in chloroform containing 20% acetic anhydride
→ appearance of pink colour on heating → presence of steroids and
triterpinoids.
(2) Tetranitro methane test: Alcoholic extract of drug + tetranitro
methane solution →formation of yellow colour → presence of
.sterol and triterpenoid.
• Specific tests for sterol:
(1) Libermann burchard test: Alcoholic extract of drug → evaporated
→ dry →extracted with CHCl3 + few drops of acetic anhydride +
conc.salphuric acid ( from the side wall of test tube) → appearance
of violet ring → blue colour → presence of sterol group in drug.
(2) Salkowaski test: Alcoholic extract of drug→evaporated →dry →
extracted with CHCl3 + conc. H2SO4( from side wall of test tube)
→appearance of yellow colored ring (at the junction of two liquids)
→ turn to red → presence of sterol group in drug

22. http://www.pharmacy180.com/article/chemical-tests-of-glycosides-166/
• Specific test for triterpenes :
• Trichloro acetic acid test: Drug + saturated trichloro acetic acid → coloured precipitate
→ presence of triterpenes.
• Test for Saponin glycosides:
• (i) Haemolysis test: A drop of blood on slide + few drops of aq. saponin solution →
appearance of ruptured red blood cells →the presence of sapnonin glycoside.
• (ii) Foam test: 1 gm of sample drug + 10 to 20 ml of water →well shake →generation of
froths → the presence of saponins.
• Flavonoid glycosides :
General test:
• (i) Shinoda test: alcoholic extract of 1 gm of drug + magnesium turning+ dilute
HCl → appearance of red colour → the presence of flavonoids.
-Alcoholic extract of 1 gm of drug sample + zinc turning + dil. HCl
→appearance of deep red colour → turns to magenta colour → the presence
of dihydro flavonoids (other type of flavonoid glycoside).
• (ii) Ammonia test: To the alcoholic solution of 1 gm of drug sample , when
filter paper dipped and after that exposed to ammonia vapor, appearance of
yellow spot on the filter paper indicates the presence of flavonoid.
• (iii) Vanilin HCl test:
Alcoholic solution of drug sample + vanillin HCl → appearance of pink colour→
presence of flavonoid

23. Coumarin glycoside : specific tests:
• (i) Fluorescence test :
• Alcoholic extract of drug sample + NaOH solution (1N) → generation of blue – green fluorescence
→ indicates presence of coumarins.
• (ii) Ferric chloride test :
• Concentrate alcoholic extract of drug sample + few drops of alcoholic FeCl3 solution →appearance
of dark green colour → turned to yellow after some time on addition of conc. HNO3 → indicates
the presence of coumarins.
Cardiac glycosides :
Specific test:
• (i)3,5-dinitro benzoic acid test :
Alcoholic solution of drug sample + few drops of NaOH + 2 % solution of 3,5- dinitro benzoic acid
→appearance of pink colour → indicates the presence of cardiac glycosides.
General tests :
• (i) Legal test :
Alcoholic extract of drug + equal volume of water + 0.5 ml of strong lead acetate solution → well
shake →filter → filtrate extracted with same volume of CHCl3→CHCl3 extract evaporate → dryness
→ remainder dissolve with 2 ml of pyridine and sodium nitropruside + NaOH solution to make it
alkaline → appearance of pink colour → indicates the presence of aglycon or glycoside moiety.
• (ii) Baljet test :
Section of drug containing cardiac glycoside ( thick section of leaf of digitalis) →dipped into sodium
picrate solution → appearance of yellow to orange colour → indicate the presence of aglycon
moiety.
• (iii)Keller – kiliani test :
Alcoholic extract of drug + equal volume of water + 0.5 ml of strong lead acetate solution → shake
→ filter→ filtrate extracted with same amount of CHCl3 → CHCl3 extract evaporated to dry →
remainder dissolved in 3 ml of glacial acetic acid + few drops of FeCl3 solution + 2ml of conc.
H2SO4→ reddish brown layer → turns to bluish green → indicate the presence of aglycon (
digitoxose).

24. Borntrager’s Test

25. Glycosides containing crude drugs
• Cardiac glycoside-Digitalis,
• Saponins glycoside-Liquorice, Brahmi, Senega,
Ginseng
• Anthracene(Anthraqunone) glycosides-Aloe,
Rhubarb, Senna, Cascara, Indian squill,
Strophanthus, Dioscorea, Gymnema
• Cyanogenetic glycosides-Bitter almond, white
cherry bark