Preparative isolation of cyclolanostane-type saponins from Astragalus membranaceus Bge. var. mongholicus (Bge.) Hsiao by TLC-MS/MS guided high-speed counter-current chromatography

Two cyclolanostane-type saponins, astragalosides I and II, were first identified by TLC-MS/MS in the ethyl acetate extract of the roots of Astragalus membranaceus Bge var. mongholicus (Bge.) Hsiao without chemical reference substances. They were then isolated by high-speed counter-current chromatography with a two-step two-phase solvent system of ethyl acetate-2-propanol–water (5:1:5, 50:1:50, v/v/v). The quantities of astragalosides I and II isolated from 1 g of the crude extract were 30.2 mg and 16.5 mg, respectively. Their purities were found to be over 95% by HPLC–ELSD analysis. Their chemical structures were confirmed by 1H and 13C nuclear magnetic resonance analysis.