Stilbenoids isolated from the roots of Rheum lhasaense under the guidance of the acetylcholinesterase inhibition activity.

Four unknown stilbenoids, including one dimer, namely 4'-methoxy-scirpusin A (5) and three monomeric stilbene glycosides, namely piceatannol-3'-O-[2''-(3,5-dihydroxy-4-methoxybenzoyl)]-β-D-glucopyranoside (13), piceatannol-3'-O-(2''-galloyl)-β-D-glucopyranoside (14) and piceatannol-3'-O-(6″-p-coumaroyl)-β-D-glucopyranoside (16) together with 15 described compounds, were isolated from the ethyl acetate fraction of the ethanol extract of roots of Rheum lhasaense based on the guidance of the inhibitory effect on acetylcholinesterase. The structures of the unknown compounds were established by combined spectroscopic analysis and comparing their spectral data with compounds with similar structures. Some selected components were also investigated for their inhibitory abilities on acetylcholinesterase (AChE), indicating that compound 13 may be responsible for higher inhibitory activity of the ethyl acetate fraction on AChE.