Identification of α-glucosidase inhibitors from cyclocarya paliurus tea leaves using UF-UPLC-Q/TOF-MS/MS and molecular docking

Leaves of Cyclocarya paliurus (CP) have a potential antihyperglycemic effect, but its active compositions responsible for the beneficial properties remain unclear. The CP extract exhibited remarkable α-glucosidase inhibitory activity with an IC50 value of 31.5 ± 1.05 μg mL-1, much lower than that of the positive control acarbose (IC50 = 296.6 ± 1.06 μg mL-1). To identify the specific α-glucosidase inhibitors from the CP extract, affinity ultrafiltration coupled with ultra-performance liquid chromatography and quadrupole-time-of-flight mass spectrometry (UF-UPLC-Q/TOF-MS/MS) was developed and 11 potential α-glucosidase inhibitors from CP extract were identified. In vitro α-glucosidase inhibitory assay verified that quercetin-3-O-glucuronide, kaempferol-3-O-rhamnoside, quercetin, kaempferol, asiatic acid and genistein were primarily responsible for the α-glucosidase inhibitory activity of the CP extract. Further, a hypoglycemia test also verified that these α-glucosidase inhibitors had the potential to reduce post-prandial hyperglycaemia in C57BL/6 mice. Moreover, the molecular docking study revealed that these identified α-glucosidase inhibitors more easily occupy the active sites of α-glucosidase than does the positive control acarbose. These findings suggest the CP tea leaves are the potential source of a hypoglycaemic agent.