Development of a method to screen and isolate potential α-glucosidase inhibitors from Panax japonicus CA Meyer by ultrafiltration, liquid chromatography, and counter-current chromatography

A new assay based on ultrafiltration, liquid chromatography and mass spectrometry was developed for the rapid screening and identification of the ligands for alpha-glucosidase from the extract of Panax japonicus. Six saponins were identified as alpha-glucosidase inhibitors. Subsequently, the specific binding ligands, namely, notoginsenoside R-1, ginsenoside Rb-1, chikusetsusaponin V, chikusetsusaponin IV, chikusetsusaponin IVa, and ginsenoside Rd (the purities were 94.18, 95.43, 96.09, 93.26, 94.50, 93.86%, respectively) were separated by counter-current chromatography using two-phase solvent systems composed of tert-butyl methyl ether, acetonitrile, 0.1% aqueous formic acid (3.8:1.0:4.4, v/v/v) and the solvent system composed of methylene chloride, isopropanol, methanol, 0.1% aqueous formic acid (5.8:1.0:6.0:2.2, v/v/v). The results demonstrate that ultrafiltration, liquid chromatography and mass spectrometry combined with high-speed counter-current chromatography might provide not only a powerful tool for screening and isolating alpha-glucosidase inhibitors in complex samples but also a useful platform for discovering bioactive compounds for the prevention and treatment of diabetes mellitus.