a-Glucosidase inhibitors extracted from the roots of Polygonum multiflorum Thunb.

A novel stilbene glucoside, polygonumnolide D (1), and a novel dianthrone glycoside, polygonumnolide E (2), were isolated from a 70% EtOH extract of the dried roots of Polygonum multiflorum Thunb., together with six known compounds (3-8). Their structures were elucidated by 1D and 2D NMR as well as mass spectroscopy data. The isolated compounds were evaluated for their a-glucosidase inhibitory activities in vitro. Compounds 1, 2 and 5 showed the inhibitory activity against a-glucosidase with the IC50 values of 2.4, 2.7 and 0.3μM, respectively.