Phytochemical identification from Lithocarpus polystachyus by UHPLC-Q-TOF-MS and its protein tyrosine phosphatase 1B and α-glucosidase activities.

Lithocarpus polystachyus leaves have become popular healthful tea due to its antidiabetic activity. In the present study, the phytochemical profiles were achieved by UHPLC-Q-TOF-MS in both positive and negative ion modes. A total of 17 compounds were tentatively characterized and identified by means of accurate mass and characteristic fragment ions. Total phenolic contents ranged from 9.0 to 13.4 g gallic acid equivalents (GAE)/100g of dry weight. In addition, α-glucosidase and protein tyrosine phosphatase 1B (PTP1B) inhibitory activities were evaluated. The L. polystachyus extracts significantly showed the α-glucosidase inhibition rate more than 88.1% at a concentration of 1.25 mg/mL. The acarbose was 93.6% at a concentration of 5 mg/mL. The PTP1B inhibition rate showed more than 84.3%. The antioxidant capacities were determined using DPPH, ABTS, and FRAP ranged from 50.5 to 72.5 g trolox, from 43.2 to 77.7 g trolox, and from 5.0 to 10.6 g BHT (equaling trolox or BHT per 100 g of dry weight), respectively. L. polystachyus could be considered as functional food for antidiabetic and antioxidative activities, due to its rich phenolic and dihydrochalcone contents.