New triterpenoids from acorns of Quercus liaotungensis and their inhibitory activity against α-glucosidase, α-amylase and protein-tyrosine phosphatase 1B

Abstract Acorn has been used as a functional food with numerous nutritional and active ingredients. In this study, 3 new triterpenoids, together with 22 known compounds were isolated from acorns ( Quercus liaotungensis ) and further confirmed by NMR. In order to disclose the hypoglycaemic ingredients, the extracts and all the discovered compounds were researched for enzyme inhibition using in-vitro assays on α -amylase, α -glucosidase, and protein-tyrosine phosphatase 1B (PTP1B). The results suggested that 75% EtOH, PE, EtOAc, and n-BuOH extracts of acorns all exhibited potent inhibitory activities against PTP1B and α -glucosidase. Most of the compounds showed strong inhibitory effects on PTP1B and α -glucosidase, especially new compounds and compound 12 , their IC 50 values were about 6-fold to 20-fold lower than positive control, all showed competitive inhibitory pattern. The result suggested that triterpenoids from acorns are potential functional food ingredients that can be used as new anti-diabetic agent.