SCREENING FOR α-GLUCOSIDASE INHIBITORS FROM COPTIDIS-REHMANNIAE HERB COUPLE BY USING ULTRAFILTRATION LIQUID CHROMATOGRAPHY/MASS SPECTROMETRY

α-Glucosidase inhibitors have been used for the management of type 2 diabetes mellitus (T2DM) for a long time. The natural α-glucosidase inhibitors from Chinese herbal medicine have become an attractive therapeutic approach for treating T2DM due to their low toxicity. The assays for the discovery of compounds in natural product extracts, however, mostly needed labor-intensive and time-consuming purification. In the current study, the screening of α-glucosidase inhibitors from Coptidis-Rehmanniae herb couple which was composed of Rhizoma Coptidis and Radix Rehmanniae, was investigated by ultrafiltration liquid chromatography/mass spectrometry (UF-LC/MS). As a result, four compounds binding to α-glucosidase were observed and identified to be jatrorrhizine, coptisine, palmatine, and berberine. Subsequently, the sustained off-resonance irradiation collision-induced dissociation Fourier transform mass spectrometry was performed for validation. In addition, the specific binding of ligands to α-glucosidase was demonstrated using UF-LC/MS and the ligands were ranked in order of affinity for α-glucosidase. The relative affinity order for the ligands was coptisine > jatrorrhizine > palmatine ≈ berberine, which indicated that coptisine and jatrorrhizine exhibited more potent α-glucosidase inhibitory activity compared to palmatine and berberine. Therefore, UF-LC/MS might provide not only a powerful tool for screening α-glucosidase inhibitors in complex samples but also a useful platform for bioactive compounds discovery of the efficient anti-diabetic drugs.