Tannins

Tannins
Definition, classification, properties and test for identification
PRESENTED BY:
MR. PRITAM VIJAY JUVATKAR
ASSISTANT PROFESSOR
pvjuvatkar@rediffmail.com, +91 9987779536
KONKAN GYANPEETH RAHUL DHARKAR COLLEGE OF PHARMACY AND RESEARCH INSTITUTE,
KARJAT
UNIVERSITY OF MUMBAI

Pritam Vijay Juvatkar 9987779536 Tannin 2
• Definition
 These secondary metabolites mixture of complex organic substances in which polyphenols are present,
generally with o-dihydroxy or o-trihydroxy groups on a phenyl ring, astringent substances, Capacity to
combine with tissue proteins and precipitate them, Mild antiseptics.
• Physical & Chemical Properties of Tannin
 Fairly high molecular weight, colloidal solutions, Non-crystalline substances and acidic in nature
 soluble in alcohol, glycerine, dilute alkalies, but practically insoluble in organic solvents except
acetone
 Solution of tannin precipitates gelatin, and alkaloids.
 Tannins are precipitated by salts of copper, tin, and lead.
 They are precipitated by strong potassium dichromate solution or chromic acid solution.
 Ferric chloride gives bluish-black or brownish- green colour potassium ferri cyanide with ammonia
gives deep red colour.
Tannin

• Classification of Tannins
 The tannins are broadly classified into three groups based on complexity of their chemical nature
and according to their behavior on dry distillation.
 Hydrolysable Tannins
 Condensed Tannins
 Pseudotannins

Classification of Tannins-: Hydrolysable tannins
 Tannins are hydrolysed by acids or enzymes gives gallic acid or ellagic acid.
 On dry distillation, gallic acid and other components get converted to pyrogallol.
 They respond to ferric chloride solution, producing blue colour.
 The examples of hydrolysable tannins are
 Myrobalan
 Bahera
 Arjuna
 Amla
 Galltannin in nutgall,
 Rhubarb,
 Clove and
 Chestnut;
 Ellagitannin from oak,
 Myrobalans
 Pomegranate bark.
O
O
O
O
OH
OH
O
H
O
H
Gallic acid
Ellagic acid
Pyrogallal

Classification of Tannins-: Condensed tannins
 They are much resistant to hydrolysis
 They are related to flavonoid pigments, phlobatannins or proanthocyanidins
 On dry distillation they yield catechol
 Tannins with ferric chloride produce brownish-green colour
 Unlike the hydrolysable tannins, on treatment with enzymes or mineral acids, they are polymerized
or decomposed into red coloured substances called phlobaphenes
 They are formed via derivatives of flavones, like catechin or flavan-4-ol or flavan-3, 4-diols

Classification of Tannins-: Condensed tannins
 They are distributed in different parts of plants,
 The green tea and hamamelis leaves;
 Cinchona, cinnamon and
 Ashoka and Wild cherry bark;
 Male fern rhizome;
 Cocoa, cola and areca seeds;
 Pale and black catechu
Glucogallin Catechin
Catechol
Classification of Tannins-: Pseudotannins
 They do not obey to goldbeater's skin test and are low molecular weight compounds.
 Examples: Chlorogenic acid in coffee and nuxvomica, ipecacuanhic acid in ipecacuanha and catechins in cocoa

Chemical Test of Tannin :Goldbeater's skin test
Untanned fresh skin of an animal intestine of ox Treated
with hydrochloric acid
.
putting in ferrous sulphate solution.
placed in tannin solution for 5 minutes.
Washing with distilled water
A brown or black colour is
developed on the skin due to tannin.
Rinsed with distilled water

Thank You
PRESENTED BY:
ASSISTANT PROFESSOR
KARJAT

Disclosure
PRESENTED BY:
ASSISTANT PROFESSOR
KARJAT
This Presentation is meant for Study Notes for B.Pharm Students only. Please do
not take as a reference for treatment for an ailments or other usage

Tannins

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