Tannins

A complex topic described in slides for better understanding.

1. Associate Professor Nitu M adan Tannins

2. Tannins are complex organic, high molecular weight, non –nitrogenous plant product which generally have astringent properties . Chemically t hey contain the mixture of complex organic compounds containing polyphenols generally along with o- dihydroxy or o- trihydroxy groups on a phenyl ring. Defination

3. Tannins are classified on the basis of Goldbeaters skin test. Those showing the positive Goldbeater test are considered as T rue tannins Tannins which fails to give the Goldbeater test are considered as Psuedotannins Classification

4. Classification

5. True tannins These are further classified on the basis of hydrolytic reaction and nature of phenolic nuclei involved in the tannin structure

6. Hydrolysable tannins These tannins are hydrolysed by acids or enzymes and products of hydrolysis are gallic acid and ellagic acid. On dry distillation gallic acid and other phenolic components gets converted to Pyrogallol . Hence they are also called as Pyrogallol tannins. With Fecl 3 they gives blue colour e.g gallotannin in nutgall, rhubarb,clove

7. Condensed Tannins These tannins are not readily hydrolysed by acid or enzyme treatment but get decomposed to red insoluble compounds known as Phlobaphenes . They are also known as non-hydrolysable tannins. On dry distillation they are converted to catechol. With Fecl 3 they give brownish green colour e.g catechutannic anid in catechu

8. Psuedotannins They are simple phenolic compounds of lower molecular weight They do not give Goldbeaters test e.g chlorogenic acid

9. Tannins forms colloidal solution with water and non-crystalline substance. They show acidic reaction due to phenols. They are soluble in alcohol, water, dilute alkalies , acetone and glycerine compounds. Tannins have astringent taste. Solutions of tannins precipitate proteins, alkaloids, heavy metals, gelatin and glycosides. They produce blue or greenish black colour with Fecl 3. They causes smooth muscle contraction when applied. Properties of Tannins

10. Goldbeaters skin test Goldbeaters skin(membrane from intestine of ox) + dil Hcl →rinse with distilled water + place in tannin sample for 5 min→ wash with distilled water+ FeSo 4 →brown or black colour Test with Fecl 3 Hydrolysable Tannins+ Fecl 3 → blue black colour Condensed Tannins + Fecl 3 → brownish green colour Gelatin test Solution of true tannins+10% Nacl→precipitates 1% gelatin solution Chemical test for tannins

11. Test with Phenazone Aqueous drug solution+ sodium acid phosphate → warm → cool → filter → fiterate + 2% phenazone solution → precipitate all tannins. Test for catechins Matchstick dipped in dilute extract of drug and moisten with Hcl near flame gives pink or red colour. catechins in presence of acid produces phloroglucinol which reacts with the lignin present in the matchstick and gives the colour.

12. Synonym : Gambier, catechu Biological source : It is dried aqueous extract of leaves and young shoots of Uncaria gambier Family: Rubiaceae Geographical Source : Malaysia , S ingapore , Indonesia Cultivation : Method of Propagation : sowing seeds in nursery beds Height required : 170m Seedlings are transplanted in open field after 9 months. First harvesting is done when plant reaches the height of 2m. The plant yields the drug upto 20 years. Pale catechu

13. Collection: Leaves and young shoots are collected and boiled for 3hours in a ‘Cauldron’ a pot made of wood with iron base. Decoction obtained is concentrated till it becomes pasty mass with yellowish green colour. This mass is converted to cubes and dried. Description : colour : dark brownish to dull brick red externally, pale brownish internally Odour : odourless Taste : Astringent Pale catechu comes in a form of cubes of 2-4cm length.

14. Chemical constituents: catechin catechutannic acid catechu red q uercetin gambierfluoroscin Chemical Test : 1.Test for catechin : Matchstick dipped in pale catechu extract and moisten with Hcl near flame gives pink or red colour. catechins in presence of acid produces phloroglucinol which reacts with the lignin present in the matchstick and gives the colour . 2. Chloroform extract of drug gives greenish yellow colour due to chlorophyll. This test is negative for black catechu

15. 3.Test for gambierfluroscin : Powdered drug+ alcohol→Extract→Filter → Filterate + NaOH solution → shake+ light petroleum → shake and allow to stand → petroleum layer shows green fluoroscence . 4.Drug +vanillin Hcl → pink or red colour Uses: Astringent i ncreases appetite dyeing and tanning industries manufacture of ink

16. Synonym: Kutch,kattha,khadir,khair Biological source : It consists of dried aqueous extract of the heartwood of plant Acacia catechu wild F amily : L eguminoceae Geographical source ; In India Madhyapradesh , Punjab, Maharashtra, Gujrat , Rajasthan, Tamilnadu , Assam Method of preparation: 1.The heartwood is obtained by seperating bark and sapwood cut into chips and put into extractors. 2.Steam is passed for maximum extraction. 3.The extract is concentrated in vaccum and cooled by refrigeration. 4.It is centrifuged to isolate the cake of kattha . 5.The cake is dried and moulded in desired size Black Catechu

17. Description Colour : light brown to black Odour : None Taste : Astringent Size : 2.5-5cm Shape : Cube or irregular fragment Chemical constituents acacatechin catechutannic acid catechu red quercetin

18. Chemical test 1.Drug + Fecl 3 → bluish-black colur 2. Drug +vanillin Hcl → pink or red colour 3. L ime water+ Aqueous solution of drug → b rown colour Uses astringent cooling and digestive purpose cough and diarrhoea dyeing and tanning industry printer inks manufacture

19. Synonym : Bijasal , Indian kino tree, Malabar kino Biological source : It consists of dried juice of plant Pterocarpus marusupium , Family: Leguminosae Geographical Source : Gujrat , Madhyapradesh , Bihar, Uttarpradesh , Orissa, Assam, Karnataka Organoleptic Characters Colour : Ruby-red Odour : Odourless Taste : Astringent Size : 3-5mm granules Shape : Angular grains Pterocarpus

20. Chemical Constituents kinotannic acid kino -red kinoin pyrocatechin resin gallic acid Chemical test 1.Aqueos solution of Drug+ FeSO 4 → Green colour 2.Drug+ Alkali → Violet colour 3.Drug+ Mineral Acid → Ppt Uses Astringent diarrhoea and dysentry Haemorrhage Hypoglycemic toothache