TANNINS

1. TANNINS

2. TANNINS
Tannins are complex organic, non-nitrogenous plant
products, which generally have astringent properties.
The name tannin is derived from the French tanin
(tanning substance) and is used for a range of natural
polyphenols.
Tannins are secondary metabolites that are present in
solution form in the cell sap and in distinct vacuoles.

3. PSEUDOTANNINS
Pseudo tannins are compounds of low molecular weight than
true tannins.
This is not as such separate group of tannins but maybe treated
as a sub-group because they do not obey goldbeaters skin test.
Examples
⚫ Gallic acid - rhubarb
⚫ Catechins – catechu, cocoa, guarana, Australian kinos
⚫ Chlorogenic acid – coffee and nux vomica
⚫ Ipecacuanhic acid - Ipecacuanha

4. CLASSIFCATION OF TANNINS
The tannins are classified into two groups based on
their chemical nature and according to their behavior
on dry distillation.
Hydrolysable tannins Condensed tannins
These tannins are hydrolysable by Condensed tannins are not
mineral acids or enzymes readily hydrolysable to simpler
such as tannase. molecules with mineral acids.
The structures involve several The structures involve
molecules such as leucoanthocyanidin,
gallic acids, ellagic acids etc., catechin etc.,

5. PTEROCARPUS
Synonyms: Bijasal, Malabar kino, Indian kino tree
Biological source: It consists of the dried juice of the plant
PterocarpusmarsupiumLinn. obtained by making incisions to the
stem bark.
Family: Leguminosae
Macroscopic characters:
Colour - Ruby red
Odour - odourless
Taste – astringent
Shape - angular grains

6. Chemical constituents
Kino contains about 70-80% of kino tannic acid, kino red,
k- pyrocatechin (catechol), resin and Gallic acid.
Kinoin is an insoluble phlobaphene and is produced by
the action of oxidase enzyme.
Kino red – an anhydride of Kinoin.
Identification tests:
1. Pterocarpus with mineral acids forms precipitate.
2. When reacted with alkalis, violet colour is produced .
3. When the solution of drug is treated with ferrous sulphate,
green colour is produced.

7. USES
⚫ It is used in dying, tanning and printing.
⚫ Used as powerful astringent.
⚫ Used in the treatment of diarrhoea and dysentery.
⚫ The aqueous infusion of the wood is of considerable benefitin
diabetes as they are known to posses hypoglycemic action.

8. PALE CATECHU
Synonyms: Gambier, Gambir, Catechu
Biological source: It is a dried aqueous extract of the leaves
and young shoots of Uncaria gambier Roxburgh,
Family: Rubiaceae
Macroscopic characters:
Colour – reddish-brown
Odour – odourless
Taste – astringent (bitter and sweet)
Shapes – acicular crystals

9. Chemical constituents
Pale catechu contain from about 7 to 30% of pseudotannin catechuand 22
to 55% of a phlobatannin catechutannicacid. Both of the about component
constituteover 60% of the drug. It also contains catechu red, gambier
fluorescin and quercetin.It contains indolealkaloid up to 0.05%, which
includes gambirtannin and its derivatives. Gambirtannin gives a strong
fluorescenceunder UV light. Catechin forms white, needle like crystals,
which dissolves in alcoholand hot water. Catechutannicacid gives green
colourwith ferric chloride.
Identification tests
1. It gives test for Catechins by dipping a match stick in
hydrochloric acid and warming it near the flame.
2. Witha mixture of vanillin and hydrochloric acid , it shows pink
or red colour.
3. Test for Gambier-fluorescin: The drug is extracted with alcohol
and sodium hydroxide is added to extra followed
by a addition off a few drops of light petroleum. The mixture is
shaken and kept for some time. Green fluorescence
is observed in light petroleum layer.

10. USES
⚫ It is used as an astringent in the treatment of diarrhoea
in the form of lozenges.
⚫ It is used in dyeing and tanning industries.
⚫ Used as protection for fish nets.

11. BLACK CATECHU
● Synonyms: Kattha, cutch, Khadir-catechu,catechu
● Biological source: It is a dried aqueous extract prepared
from the heartwood of Acacia catechu wild and Acaciachundra
wild.
● Family: Leguminosae
● Macroscopic characters:
Colour – reddish-brown
Odour – odourless
Taste – astringent ( bitter and sweet)
Shapes – acicular crystals

12. Chemical constituents
Cutch or black catechu resembles pale catechu or gambier in its
composition. It contains about 2-12% of catechin and about 25-33%of
phlobatannincatechutannicacid. The principle fraction of cutch has been
identified as a mixture of catechin isomers which includes (-)epicatechin,
catechin, DL-acacatechin, L-acacatechin and D-isoacacatechin. It also
contains 20-30%gummy matter, catechin red, quercetin and querecitin. It
yields 2-3% of ash.
Identification tests
1. Witha mixture of vanillin and hydrochloric acid , it shows pink
or red colour.
2. Lime water when added to aqueous extract of black catechu
gives brown colour, which turns out to red precipitate on
standing.
3. Dilute solution of black catechu with ferric ammonium sulphate
produces green colour.

13. USES
⚫ It is used as an astringent externally for boils, ulcers
and skin eruptions.
⚫ It is also used in cough and diarrhoea.