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TANNINS - I D.Pharm ER-20:13T
- 2. CONTENT Introduction Classification of Tannins Occurrence Distribution Isolation Identification test Therapeutic activity Pharmaceutical application
- 3. INTRODUCTION DEFINITION: Tannins are defined as, Complex substances that usually occur as mixtures of polyphenols that are very difficult to separate since they do not crystallize. Tannins are class of “ASTRINGENT” Tannins are present in the aerial parts, E.g., Leaves, Fruits, Barks or Stem.
- 4. CLASSIFICATION OF TANNINS TRUE TANNINS (High Molecular Weight Compounds) 1. Hydrolysable Tannins (These may be hydrolyzed by acid or enzymes) Gallitannins E.g: Rhubarb Ellagitannins E.g: Myrobalans 2. Condensed Tannins (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% Hcl and 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, whereas pseudo tannins show very little colour or negative test.
- 10. IDENTIFICATION TEST FOR TANNINS EXPERIMENT OBSERVATION INFERENCE Gelatin Test: • To a solution of sample, add aqueous solutions of gelatin and sodium chloride are added. A white buff- coloured precipitate is formed. Presence of Tannins. Catechin Test: (Matchstick Test) • Catechin test is the modification of the well known 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. Matchstick wood turns pink or red. Presence of Tannins.
- 11. THERAPEUTIC ACTIVITY OF TANNINS 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
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