Separation of three flavonoid glycosides from Polygonum multiflorum Thunb. leaves using HSCCC and their antioxidant activities

Polygonum multiflorum Thunb. is a traditional herb which was widely distributed in China. The leaves of P. multiflorum (PML), which contains lots of antioxidant constituents, are often used for tea. In this study, three flavonoid glycosides were successfully separated and characterized from the ethyl acetate fraction of 80% ethanol extracts of PML by high-speed counter-current chromatography (HSCCC). The biphasic solvent system which can isolate purified myricitrin (44.5 mg), quercitrin (23.86 mg) and afzelin (14.39 mg) from 110 mg of the ethyl acetate fraction of PML was composed of n -hexane–ethyl acetate–methanol–water (0.5:3:1:2, v/v/v/v). Moreover, the purities of each compound were 94.9, 97.0, and 95.7% as determined by high-performance liquid chromatography (HPLC), respectively. Three flavonoid glycosides were obtained using only one-step HSCCC separation for the first time and the chemical structures of these three compounds were identified using the techniques of NMR and ESI–MS. The antioxidant activities of these three compounds, ethyl acetate fraction, and crude extract were evaluated by three antioxidant assays. The results of antioxidation assays showed that myricitrin and quercitrin have strong antioxidant activity and the two components may be the material basis of the antioxidant potential of PML. This work confirmed the feasibility of HSCCC to separate compounds from complex samples and it suggests that PML have pharmaceutical potential as natural antioxidant agents.