Polyflavanostilbene A, a New Flavanol-Fused Stilbene Glycoside from Polygonum cuspidatum

Polyflavanostilbene A, a new flavanol-fused stilbene glycoside, was isolated from the rhizome of Polygonum cuspidatum. Its unusual structure, including its absolute stereochemistry, was determined by UV, IR, HRESIMS, and 1D and 2D NMR data and by the comparison of experimental and calculated electronic circular dichroism (ECD) spectra. Polyflavanostilbene A has an unprecedented rearranged flavanol skeleton fused to stilbene via a hexahydrocyclopenta[c]furan moiety. Polyflavanostilbene A showed strong inhibitory activity against α-glucosidase with an IC(50) value of 17.7 μM.