Screening for α-glucosidase inhibitors from Selaginella uncinata based on the ligand fishing combined with ultra-high-performance liquid chromatography-quadrupole time-of-flight-tandem mass spectrometry.

Biflavonoids are naturally occurring compounds consisting of two flavonoid moieties that have received substantial attention from researchers. Although many kinds of biflavonoids are typically distributed in Selaginella uncinata with hypoglycemic effect, their anti-α-glucosidase activities are not yet clear. In this study, a ligand fishing strategy for fast screening of α-glucosidase inhibitors from S. uncinata was proposed. α-Glucosidase was first immobilized on Fe O magnetic nanoparticles (MNPs) and then the α-glucosidase-functionalized MNPs were incubated with crude extracts of S. uncinata to fish out the ligands. Furthermore, considering the similarity and easy confusion of the structures of biflavonoids, the fragmentation patterns of different types of biflavonoids were studied. Based on this, 11 biflavonoids ligands with α-glucosidase inhibitory activities were accurately and quickly identified from S. uncinata with ultra-high-performance liquid chromatography-quadrupole time-of-flight-tandem mass spectrometry. Furthermore, these ligands were confirmed to be potential inhibitors through the in vitro inhibitory assay and molecular docking.