Caffeic Acid (CA)

Caffeic acid is an organic compound that is classified as hydroxycinnamic acid. This yellow solid consists of both phenolic and acrylic functional groups. It is found in all plants because it is a key intermediate in the biosynthesis of lignin, one of the principal components of plant biomass and its residues. Caffeic acid, which is unrelated to caffeine, is biosynthesized by hydroxylation of coumaroyl ester of quinic acid (esterified through a side chain alcohol). This hydroxylation produces the caffeic acid ester of shikimic acid, which converts to chlorogenic acid. It is the precursor to ferulic acid, coniferyl alcohol, and sinapyl alcohol, all of which are significant building blocks in lignin. The transformation to ferulic acid is catalyzed by the enzyme caffeic acid-O-methyltransferase. Caffeic acid and its derivative caffeic acid phenethyl ester (CAPE) are produced in many kinds of plants.