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TANNINS

TANNINS. Tannins Tannins is a substance found naturally in many different plants, most in grapes and tea leaves ,precipitate proteins from their aqueous solutions. Types of hydrolysable tannin: A- Gallitannin On hydrolysis , it gives gallic acid and glucose. Present in clove..

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TANNINS

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  1. TANNINS

  2. Tannins • Tanninsis a substance found naturally in many different plants, most in grapes and tea leaves ,precipitate proteins from their aqueous solutions.

  3. Types of hydrolysable tannin: A- Gallitannin On hydrolysis , it gives gallic acid and glucose. Present in clove.. B- Ellagitannin On hydrolysis it gives ellagic acid and glucose  Present in pomegranate. Pseudotannins: Pseudo tannins are low molecular weight compounds found in Rhubarb , tea and coffee

  4. Identification of Tannins: 1-tannin + ferric chloride (FeCl3) : Bluish black colour with hydrolysable tannin. Brownish black colour with catechol.

  5. 2- 2-Gelatin test: Solution of tannins (about 5-1%) precipitate 1% Solution of gelatin containing l0 % sodium chloride Gallic acid and other pseudotannins also precipitate. gelatin if the solutions are sufficiently concentrated. 3- Bromine water: only condensed tannin gives ppt. with bromine water.

  6. 4-Gold beater's skin test: asoak a small piece of Gold beater's skin membrane in 2% hydrochloric acid ( HCL). b- rinse with distilled water. c- place the piece for 5 minutes in the tannin solution to be tested. d- wash with distilled water

  7. ……… e- transfer to 1% ferrous sulfate (FeSO4) solution. f-a brown or black colour in the skin denote the presence of tannins.

  8. Quantitative determination of tannin: 1- Hide powder method:The difference in the dry weight of the extract before and after treatment with hide powder is takenas a measure for tannin content. 2- Copper acetate method: Gravimetric method using copper acetate as precipitant.

  9. Uses of Tannins: Industrially:In leather tanning, ink manufacture. Medicinally:Astringent, haemostatic, antidiarrheal, antidote in alkaloid and heavy metals toxicity.  In labs:Reagent for detection of proteins, alkaloids and heavy metals because of their precipitating properties.

  10. Tannin containing drugs : Galls (Blue Galls, Aleppo Galls, Turkish Galls):Turkish galls are vegetable growths formed on the Young twigs of the dyer’s oak.

  11. Origin of galls : (pathological outgrowth) as a result of the deposition of the eggs of the gall-wasp Cynips gallae tinctoriae on the young twigs of Quercus infectoria (Fagaceae). They are Collected before the escape of the insect and known as blue galls.

  12. Characters of galls : 1- galls are globular in shape and form l0 to 25 mm in Diameter . 2-They have a short basal stalk and numerous rounded projection on the surface. 3-Galls are hard and heavy, usually sinking in water. 4-external surface is bluish green to olive green in color .Internally it is buff in color. 5- The so-called ‘blue' variety are actually of a grey or brownish-grey color.

  13. *Constituents of galls : Galls contain 50-70% of the tannin known as gallotannic acid. Galls also contain Gallic acid and ellagic acid.

  14. Uses of galls: Medicinally: 1-It is used as astringent 2- haemostatic used in treatment of hemorrhoids in form of suppository or ointment. Industrially: 1- in manufacture of ink and paints. 2- in tanning of leather.

  15. Commercial test : Galls + fecl3 Bluish Black color.

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