1). True tannins:
(a) Hydrolysable group:
• They are esters of a sugar (β-D-glucose), with one or more trihydroxy-benzene carboxylic acid.
• The tannins which is derived from Gallic acid called Gallo-tannin or gluco-gallin like in Rhubarb rhizomes, Clove buds etc.
• Tannis which is derived from ellagic acid called ellagotannin or glucoellagin like in Pomegranate roots bark and Eucalyptus leaves (which also contain Tannic acid which is Gallotannin).
• They form dark blue color with FeClз