Astringent flavors

thumb|upright=1.5|Crystal of potassium alum,

thumb|Representative chemical structure of a tannic acid, a type of tannin thumb|Tannin powder (mixture of compounds) thumb|A bottle of tannic acid solution in [[water ]]

3,4,5-trihydroxybenzoic acid

chemical compound

thumb|A crystal of the astringent alum thumb|The astringents and acids in fresh blackthorn berries (sloes) give the fruit its sourness.

chemical compound

Grandinin is an ellagitannin. It can be found in Melaleuca quinquenervia leaves and in oaks species like the North American white oak (Quercus alba) and European red oak (Quercus robur). It shows antioxydant activity. It is an astringent compound. It is also found in wine, red or white, aged in oak barrels.