Synthesis and antioxidant activities of berberine 9--benzoic acid derivatives.

Although berberine (BBR) shows antioxidant activity, its activity is limited. We synthesized 9--benzoic acid berberine derivatives, and their antioxidant activities were screened ABTS, DPPH, HOSC and FRAP assays. The -position was modified with halogen elements on the benzoic acid ring, which led to an enhanced antioxidant activity and the substituent on the -position was found to be better than the -position.