Screening and characterization of potential α-glucosidase inhibitors from Cercis chinensis Bunge fruits using ultrafiltration coupled with HPLC-ESI-MS/MS

A more accurate HPLC-MS screening method combining functional enzyme assay and affinity ultrafiltration screening assay was developed and applied for the screening of natural product inhibitors of alpha-glucosidase from Cercis chinensis Bunge fruits. The enzyme assay was conducted to prescreen botanical extracts, in which maltose was used as the substrate and detection object. That showed the Cercis chinensis Bunge fruits demonstrated higher alpha-glucosidase inhibitory activity (IC50 = 11.94 +/- 1.23 mu g/mL) than acarbose (IC50 = 44.03 +/- 4.37 mu g/mL) (n = 3, p < 0.05). Subsequently, twelve bioactive components targeting alpha-glucosidase were screened out and identified using affinity ultrafiltration coupled to liquid chromatography-mass spectrometry. The known inhibitor, acarbose, was used as a positive control and competitive ligand to eliminate false positives. Moreover, bindings of the twelve components to the active site of a-glucosidase were investigated via molecular docking, which further confirmed the results of the screening assay.