What is "protocatechuic acid"

n. (context organic compound English) The phenolic carboxylic acid ''3,4-dihydroxybenzoic acid'' that is a major metabolite of polyphenols

Protocatechuic acid (PCA) is a dihydroxybenzoic acid, a type of phenolic acid. It is a major metabolite of antioxidant polyphenols found in green tea. It has mixed effects on normal and cancer cells in in vitro and in vivo studies.