Chemical profile and inhibition of a-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 a-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 a-glycosidase and PTP1B inhibitory activities. A total of 12 compounds demonstrated stronger activity than acarbose (IC50 = 5.42 +/- 0.10 mu g/mL); the compound 18 yielded higher IC50 (15.62 +/- 0.20 mu M) than NaVO4 (positive control; IC50 = 29.10 +/- 0.20 mu M). These results suggested that flavonoids from licorice are potential functional food ingredients that can be used to prevent and treat type 2 diabetes mellitus. (C) 2014 Elsevier Ltd. All rights reserved.