Single-step separation of bioactive flavonol glucosides from Osteomeles schwerinae by high-speed counter-current chromatography

Two bioactive flavonol glucosides, hyperoside and quercitrin, were successfully isolated in one step from the phytochemically unknown medicinal plant Osteomeles schwerinae by high-speed counter-current chromatography using a two-phase solvent system composed of n-hexane ethyl acetate methanol water (0.5:5.5:1.5:4.5 v/v). From 160 mg of crude extract, 2.1 mg of hyperoside (98.6% purity, 83.3% recovery) and 4.5 mg of quercitrin (99.2% purity, 81.7% recovery) were separated and then their chemical structures were identified by H-1 and C-13 NMR analysis. In addition, the isolates were subjected to an in vitro bioassay to evaluate their inhibitory activity on rat lens aldose reductase. Both quercitrin and hyperoside showed excellent inhibitory activities toward rat lens aldose reductase with the IC50 values of 0.16 and 4.33 mu M, respectively, as compared with positive control, 3,3-tetramethyleneglutaric acid (28.7 mu M). So far, chemical constituents and biological activities of O. schwerinae have never been reported. This is the first report on the chemical constituents and biological activity of this plant using semi-preparative highspeed counter-current chromatography separation technique.