... and USA for 6 years. Gallic acid is a trihydroxybenzoic acid, a type of phenolic acid, a type of organic acid, also known as 3,4 ... ,5-trihydroxybenzoic acid, found in gallnuts, sumac, ... C6H2(OH)3COOH. Gallic acid is found both free and as part of tannins. Salts and esters of gallic acid are termed 'gallates'. ...