... organic acid, also known as 3,4,5-trihydroxybenzoic acid, found in gallnuts, sumac, witch hazel, tea leaves, oak bark, and ... .The chemical formula is C6H2(OH)3COOH. Gallic acid is found both free and as part of tannins. Salts and esters ... to protect human cells against oxidative damage. Gallic acid was found to show cytotoxicity against cancer cells, without harming healthy cells ...