Isolation and identification of phenolic compounds from Hypericum richeri Vill. and their antioxidant capacity.

The chemical composition and free radical scavenging properties of the MeOH extract of Hypericum richeri and its subsequent CHCl(3), n-BuOH, EtOAc and aqueous extracts were investigated. Four quercetin-3-O-glycosides, three myricetin-3-O-glycosides, 3-O- and 5-O-caffeoylquinic acid, quercetin, I3,II8-biapigenin, pseudohypericin and hypericin were identified. The constituents of the extracts were quantified using HPLC-DAD (high-performance liquid chromatography-diode array detector). Isolation of the compounds from n-BuOH and EtOAc extracts was conducted by column chromatography. Antioxidant capacity of the extracts was evaluated by superoxide radical and ABTS√(+) scavenging assays and inhibition of lipid peroxidation. The EtOAc extract of H. richeri was the most potent antioxidant in all experiments. Free radical scavenging compounds were identified by HPLC-DPPH√ (high-performance liquid chromatography-2,2-diphenyl-1-picrylhydrazyl) post-column derivatisation method, where all phenolic compounds except I3,II8-biapigenin exhibited radical scavenging properties. This is the first report of the presence of myricetin-3-O-rutinoside, myricetin-3-O-galactoside, myricetin-3-O-glucoside, 5-O-caffeoylquinic acid and I3,II8-biapigenin in H. richeri.