Page 100 - Pharmd general phytochemistry I-Final2024_LEUCTERS

Identification:

1- Goldbeater's skin test:
A small piece of ox intestine (gold beater's skin) is soaked in 2% HCl,
washed with distilled water then placed in the solution under test (containing
tannins) for 5 minutes. The skin membrane is then washed with distilled
water then put in 1 % ferrous sulphate solution, when a black or brownish
color indicates the presence of tannins in the test solution.
2- Gelatin test:
True tannins precipitate gelatin from its solution. To carry out the test a I %
solution of gelatin is used, and the tannins concentration must be within the
suitable range (0.5-1 %).
3- Phenazone test:
Tannins are precipitated from buffered solutions by phenazone. 2%
phenazone solution is added, to the tannin solution buffered with sodium
phosphate, when a bulky precipitate is formed.
4- Ferric chloride test:
Ferric chloride solution (neutral) gives with solutions of condensed tannins
greenish or brownish precipitates. While with hydrolyasble tannin it gives
bluish black precipitate.
5- Test for catechnins:
Catechin (simpler pyrogallol tannins) gives when heated with acids
phloroglucinol that can be tested for by a piece of wood (match stick)
moistened with concentrated hydrochloric acid, then warmed, when a red or
pink color is developed (lignin test).
6- Test for chlorogenic acid:
When treated with ammonia and exposed to air a green color is developed.

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