Anthraquinones and stilbenes from the roots and rhizomes of Rhubarb

Two new anthraquinone glucosides [aloe-emodin 8-O-β-d-(6′-galloyl)glucopyranoside (1) and rhein 8-O-β-d-(6′-galloyl)glucopyranoside (2)], together with 16 known compounds (3–18), were isolated from the roots and rhizomes of Rheum hotaoense C.Y. Cheng et C.T. Kao. Their structures were elucidated on the basis of extensive investigation of 1D and 2D NMR, HR-ESI-MS, and chemical evidence. In addition, the free-radical-scavenging activity was tested using the 1,1-diphenyl-2-picrylhydrazyl assay.