Chemical profile and inhibition of α-glycosidase and protein tyrosine phosphatase 1B (PTP1B) activities by flavonoids from licorice (Glycyrrhiza uralensis Fisch)

Licorice, one of the oldest and most common herbal medicines, is used as a natural sweetener and flavoring agent in food products. This study aimed to investigate the inhibitory activity of flavonoids against α-glycosidase and protein tyrosine phosphatase 1B (PTP1B). Macroporous resins were used to isolate total flavonoids from licorice extract; the obtained total flavonoid content was >80%. The extracted flavonoids were then identified by HPLC-MS/MS, and 18 compounds were isolated. These compounds were further evaluated to determine α-glycosidase and PTP1B inhibitory activities. A total of 12 compounds demonstrated stronger activity than acarbose (IC50 = 5.42 ± 0.10 µg/mL); the compound 18 yielded higher IC50 (15.62 ± 0.20 µM) than NaVO4 (positive control; IC50 = 29.10 ± 0.20 µM). These results suggested that flavonoids from licorice are potential functional food ingredients that can be used to prevent and treat type 2 diabetes mellitus.