TANNINS - I D.Pharm ER-20:13T

Unit-IV

1. TANNINS
PRESENTED BY
M.NITHYA., B.PHARM,
LECTURER, ECOP.

2. CONTENT
Introduction
Classification of Tannins
Occurrence
Distribution
Isolation
Identification test
Therapeutic activity
Pharmaceutical application

3. INTRODUCTION
DEFINITION:
Tanninsaredefinedas,Complexsubstancesthatusually
occurasmixturesofpolyphenolsthatareverydifficultto
separatesincetheydonotcrystallize.
Tanninsareclassof“ASTRINGENT”
Tanninsarepresentintheaerialparts,E.g.,Leaves,
Fruits,BarksorStem.

4. CLASSIFICATION OF TANNINS
TRUETANNINS
(High Molecular Weight
Compounds)
1. HydrolysableTannins (These may be
hydrolyzed by acid or enzymes)
Gallitannins
E.g:Rhubarb
Ellagitannins
E.g:Myrobalans
2. CondensedTannins (These are not readily
hydrolysable to simple molecule.)
E.g:Asoka Bark, Catechu
3. Complex Tannins(These are biosynthesized
from both hydrolysable and condensed
tannins)
PSEUDO TANNINS : (Low Molecular Weight Compounds)
E.g:Gallic acid, Catechins.

5. OCCURRENCE
FAMILY EXAMPLE
Leguminosae Ashoka, Acacia, Black Catechu
Combretaceae Myrobalan, Arjuna
Fagaceae Tannic acid
Euphorbiaceae Amla
Rubiaceae Pale Catechu

6. DISTRIBUTION
Barks –Cinnamon, Cinchona, Acacia, Oak
Flowers –Lime
Seeds –Cocoa, Areca
Leaves –Tea
Extracts & Dried Juices –Catechu, Acacia, Eucalyptus.

7. ISOLATION OF TANNINS
•100 gm of the powder sample reflexed for 15 min in a
500ml Erlenmeyer flask.
•During the reflex process, the entire sample should be
covered with 70% of acetone.
•The flask is removed from the hot plate and filtered in
another flask.
•The residue on the filter paper is washed off using a
sufficient amount of 70% of acetone.

8. CONT.,
•The washed solution is combined with the filterate and the
filterate and the resultant mixture subjected to extraction
using diethyl ether.
•This process is repeated five times till the diethyl ether and
tannin separate out completely as distinct upper and lower
respectively.
•The tannin layer is separated via separated via separatory
funnel.
•The tannin so collected is evaporated till a residue, known
as the extracted tannin, is obtained which is the final
product.

9. IDENTIFICATION TEST FOR TANNINS
EXPERIMENT OBSERVATION INFERENCE
Goldbeater’s skin test:
•Goldbeater’s skin is a membrane
produced from the intestine of Ox.
•A piece of goldbeaters skin
previously soaked in 2% Hcland
washed with distilled water is placed
in a solution of tannin for 5 minutes.
•It is then washed with distilled water
and transferred to 1% ferrous
sulphate solution.
A change of the
colour of the
goldbeater’s skin
to brown or black
Hydrolysable and
condensed tannins
both give the positive
goldbeater’s test,
whereaspseudo
tannins show very
little colour or
negative test.

10. IDENTIFICATION TEST FOR TANNINS
EXPERIMENT OBSERVATION INFERENCE
GelatinTest:
•To a solution of sample, add aqueous
solutions of gelatin and sodium chloride
are added.
Awhite buff-coloured
precipitate is formed.
Presence of
Tannins.
Catechin Test:(MatchstickTest)
•Catechin test is themodification of the
wellknown phloroglucinol test for lignin.
•Matchstick contains lignin.
•Dip a matchstick in the dilute extract of
the drug, dry, moisten it with
concentrated hydrochloric acid, and
warm it near a flame.
Matchstickwood turns
pink or red.
Presence of
Tannins.

11. THERAPEUTIC ACTIVITY OFTANNINS
1.Styptics
2.Anti –Diarrhoeal
3.Anti-Tumor
4.Antidote

12. PHARMACEUTICAL APPLICATIONS OF
TANNINS
1.Myrobalan –Astringent, Stomachic, Purgative
2.Arjuna –Cardio tonic, Hypotensive
3.Tannic acid –Astringent for mucous membrane
4.Amla –Diuretic, Laxative
5.Ashoka –Uterine tonic and Oxytocic
6.Black Catechu –Astringent for Boils
7.Pale Catechu –Astringent for treatment of Diarrhoea

13. Thank you