Preparative isolation and purification of two isoflavones from Astragalus membranaceus Bge. var. mongholicus (Bge.) Hsiao by high-speed counter-current chromatography

Two isoflavones, calycosin-7-O-β-d-glycoside and formononetin-7-O-β-d-glycoside, were separated from n-butanol extract of the root of Astragalus membranaceus Bge. var. mongholicus (Bge.) Hsiao by high-speed counter-current chromatography in two steps using two different solvent systems composed of ethyl acetate–ethanol–n-butanol–water (30:10:6:50, v/v) and ethyl acetate–ethanol–water (5:1:5, v/v). From 200 mg of crude extract, calycosin-7-O-β-d-glycoside (12 mg) and formononetin-7-O-β-d-glycoside (10 mg) were isolated at over 95% purity by HPLC analyses, and their structures were identified by MS, 1H NMR and 13C NMR.