TanninsTannins

They are high molecular weight phenolic They are high molecular weight phenolic compounds capable of precipitation of animal compounds capable of precipitation of animal

proteins in hides and converting them into proteins in hides and converting them into leather.leather.

““Tanning Industry”Tanning Industry”

They are widely distributed in plants.They are widely distributed in plants.

They are condensation products of Gallic acid They are condensation products of Gallic acid or Flavan-3-ol.or Flavan-3-ol.

Classification of Tannins:Classification of Tannins:

True Tannins(High molecular weight compounds)

Hydrolysable Tannins(Pyrogallol)

Condensed Tannins(Catechol)

PseudotanninsLow molecular weight compounds

e.g. Gallic acid, Flavan-3,4-diol

Pyrogallol TanninsPyrogallol Tannins Composed of central sugars with all its OH esterified Composed of central sugars with all its OH esterified

with Phenolic acids.with Phenolic acids. They can be hydrolyzed by acids or enzymes.They can be hydrolyzed by acids or enzymes. They produce sugars and:They produce sugars and:

Gallic acid Gallitannins. Present in Clove, Gallic acid Gallitannins. Present in Clove, HammamilisHammamilis

Ellagic acid Ellagitannins. Present in GeraniumEllagic acid Ellagitannins. Present in Geranium Produce pyrogallol on dry distillation.Produce pyrogallol on dry distillation.

COOH

OH

OHHO

Gallic acid

Catechol (Condensed) TanninsCatechol (Condensed) Tannins Condensation product of Flavan-3,4-diol.Condensation product of Flavan-3,4-diol. They resist hydrolysis.They resist hydrolysis. Upon prolonged heating they decompose into Upon prolonged heating they decompose into

Phlobaphane.Phlobaphane. Produce catechol on dry distillation.Produce catechol on dry distillation. Present in Cinchona, Cinnamon, Green tea.Present in Cinchona, Cinnamon, Green tea.

OHO

OH OH

OH

OH

OH

Flavan-3,4-diol

Properties:Properties:

Soluble in water, polar organic solvents Soluble in water, polar organic solvents and Alkali solutions.and Alkali solutions.

React with FeClReact with FeCl33 as they are Phenolic. as they are Phenolic.Precipitate proteins and Gelatin.Precipitate proteins and Gelatin.Form with alkaloids and Glycosides.Form with alkaloids and Glycosides.

Chemical test for Chemical test for Identification:Identification:

FeClFeCl33:: Hydrolysable tannins Bluish colour.Hydrolysable tannins Bluish colour. Condensed tannins Greenish colour.Condensed tannins Greenish colour.

Goldbeater’s Skin test (Ox-Intestine):Goldbeater’s Skin test (Ox-Intestine): Soak piece of Goldbeater’s skin in 2%HCl, wash with Soak piece of Goldbeater’s skin in 2%HCl, wash with

water, soak in test solution, wash with water, finally water, soak in test solution, wash with water, finally soak with FeSOsoak with FeSO4 4 Brown or Black colour.Brown or Black colour.

Gelatin test:Gelatin test: Tannins + 1% Gelatin solution in NaCl white precipitateTannins + 1% Gelatin solution in NaCl white precipitate

Uses:Uses:

Antioxidant.Antioxidant.Antidiarrheal.Antidiarrheal.Antidote for heavy metals poisoning.Antidote for heavy metals poisoning.Treatment of burns.Treatment of burns.Astringent to stop bleeding Astringent to stop bleeding

(Haemorrhoids, Ulcers).(Haemorrhoids, Ulcers).

Green and Black TeaGreen and Black Tea

Green Tea:Green Tea:Prepared by rapid drying at elevated Prepared by rapid drying at elevated

temperature to deactivate the enzymes.temperature to deactivate the enzymes.Contain Catechins with high antioxidant Contain Catechins with high antioxidant

properties.properties.

Black Tea:Black Tea:Undergo slow drying (Fermentation).Undergo slow drying (Fermentation).Enzyme action resulted in Hydrolysis and Enzyme action resulted in Hydrolysis and

Oxidation.Oxidation.Antioxidant properties is greatly decreased.Antioxidant properties is greatly decreased.