Fig. (1).

Chemical structure of chlorogenic acid and its isomers. The chemical name of CGA is 3-O-caffeoylquinic acid, and its molecular formula is C ₁₆H₁₈O ₉ , including catechol, carboxyl, ester, unsaturated double bond and hydroxyl. Due to the different binding sites and numbers of caffeoyl on quinic acid, CGA contains 4-O-caffeoylquinic acid, 5-O-caffeoylquinic acid, 1,3-O-dicaffeoylquinic acid, 3,5-O-caffeoylquinicacid,3,4-O-caffeoylquinic acid, 4,5-O-dicaffeoylquinic acid, and many other isomers.