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2. Condensed Tannins (Proanthocyanidins):

- These include all other true tannins, their molecules are more resistant to
breakage than hydrolysable tannins.
- On treatment with acids or enzymes they are decomposed into red
insoluble compounds known as “phlobaphenes”. Phlobaphenes give the
characteristic red colour to many drugs such as red cinchona bark.
- On dry distillation they yield catechol and these tannins are therefore
sometimes called catechol tannins. Like catechol itself , their solutions turn
green with ferric chloride.
- Condensed tannins appear to be formed of the polymerisation of flavans
e.g. catechin and leucocyanidin

OH
OH

Catechol Catechin

Examples of drugs containing condensed tannins are:tea, cinnamon,
cinchona, kola and guarana.

3. Pseudotannins: These are compounds of low molecular weight than

true tannins and they do not respond to the gold beater’s skin test.
Examples: gallic acid , ellagic acd, hexahydroxydiphenic acid and
chlorogenic acid

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