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, witch hazel, tea leaves, oak bark, and other plants.
The chemical formula is C6H2(OH)3COOH. Gallic acid is found both free and as part of hydrolyzable tannins.
Gallic acid is commonly used in the pharmaceutical industry. It is used as a standard for determining the phenol content of various analytes by the Folin-Ciocalteau assay; results are reported in gallic acid equivalents.Gallic acid can also be used as a starting material in the synthesis of the psychedelic alkaloid mescaline.