Identification of new dicaffeoylquinic acids from Chrysanthemum morifolium and their antioxidant activities.

Two new dicaffeoylquinic acids, 3,5-dicaffeoyl- epi-quinic acid (1) and 1,3-dicaffeoyl- epi-quinic acid (2), were isolated from Chrysanthemum morifolium Ramar together with six known dicaffeoylquinic acid derivatives and three flavonoids. The structures of the new compounds were elucidated using of spectroscopic methods. These compounds were assessed for antioxidant activities in the DPPH radical and superoxide anion radical scavenging systems. Most of the isolates showed strong antioxidant activities in these assay systems. Two new compounds showed potent superoxide anion radical scavenging activity (IC50 = 2.9 +/- 0.1 for 1 and 2.6 +/- 0.4 microg/mL for 2, respectively) in the xanthine/xanthine oxidase system as compared to quercetin and also showed potent DPPH radical scavenging activity (IC50 = 5.6 +/- 0.1 for 1 and 5.8 +/- 0.2 microg/mL for 2, respectively).