Chemical constituents of n-butanol extract of Astragalus rigidulus

Abstract

To study the chemical constituents of n-butanol extract from Astragalus rigidulus, HP-20 macroporous adsorption resin, Sephadex LH-20 gel, ODS gel column chromatography and semi-preparative high performance liquid chromatography were used to separate the chemical constituents. The structures of all isolates were identified by spectroscopic methods, including NMR and HR-ESI-MS. The results showed that twenty compounds including nineteen flavonoid derivatives and one sesquiterpene glycoside were isolated and purified from n-butanol extract of A. rigidulus. Their structures were identified as 7-O-methylorobol-4′-O-β-D-glucopyranoside (1), mildiside A (2), naringenin (3), purine 4′-O-β-D-glucoside (4), orobot (5), kaempferol-3-O-β-D-(6′-acetyl) glucopyranoside (6), 5,7-dihydroxy-4′-methoxyisoflavone-2′-O-β-D-glucopyranoside (7), amarantholidoside IV (8), kaempferol-3-O-α-L-rhamnopyranosyl-(1→2)-β-D-glucopyranoside (9), kaempferol (10), 5,7,4′-trihydroxyisoflavone (11), kaempferol-3-O-β-D-glucopyranoside (12), (S)-mucronulatol (13), calycosin (14), quercetin (15), pratensein-7-O-β-D-glucoside (16), 2′-hydroxy-3′,4′-dimethoxyisoflavan-7-O-β-D-glucoside (17), kaempferol-3-O-rutinoside (18), 5,7,4′-trihydroxy-3′-methoxyflavonol-3-O-rutinoside (19), quercetin-3-O-β-D-glucoside (20). It is the first report for the compounds 1-9 found in the genus Astragalus. The other compounds are isolated from the title plant for the first time. The results of this study provide basic data for the pharmacodynamic material study of A. rigidulus, and provide a theoretical reference for the rational development and utilization of the plant resources in the future.

Keywords

• astragalus rigidulus
• chemical constituents
• isolation and purification
• structure identification
• isoflavones