Identification of α-glucosidase inhibitors from the bran of Chenopodium quinoa Willd. by surface plasmon resonance coupled with ultra-performance liquid chromatography and quadrupole-time-of-flight-mass spectrometry

Extracts from the bran of Chenopodium quinoa Willd. (QBE) were reported to be active in inhibiting alpha-glycosidase, a promising target for treatment of diabetes mellitus. However, the constituents responsible for the alpha-glucosidase-inhibiting activity of QBE have not been fully characterized. The present study aimed to set up a method for rapid identification of glycosidase inhibiting compounds from the quinoa bran. With surface plasmon resonance (SPR) coupled with liquid chromatography-mass spectrometry (LC-MS), we identified eight flavonoids and ten triterpenoid saponins that may bind to the alpha-glycosidase. Analysis of the interaction kinetics by molecular docking supported their alpha-glucosidase-inhibiting activity and revealed the potential mechanisms for the inhibitory effects. In summary, this study established a SPR and LC-MS-based method for rapid in vitro screening of alpha-glucosidase inhibitors and suggested the quinoa bran a potential natural source of alpha-glucosidase inhibitors.