Effects of stilbene constituents from rhubarb on nitric oxide production in lipopolysaccharide-activated macrophages

Two new anthraquinone glucosides [chrysophanol 8-O-β- -(6′-galloyl)-glucopyranoside, aloe-emodin 1-O-β- -glucopyranoside] together with various known stilbenes and their glucosides, anthraquinone glucosides, and a naphthalene glucoside were isolated from the rhizome of Rheum undulatum L. Three stilbenes (rhapontigenin, piceatannol, resveratrol), a naphthalene glucoside (torachrysone 8-O-β- -glucopyranoside), and two stilbene glucoside gallates (rhaponticin 2′′-O-gallate, rhaponticin 6′′-O-gallate) showed inhibitory activity of NO production in lipopolysaccharide-activated macrophages. (IC50=11–69 μM). The oxygen functions (-OH,-OCH3) at the benzene ring were found to be essential to show the activity. Whereas, the glucoside moiety reduced the activity, while the α,β-double bond did not affect the activity. Furthermore, the active stilbenes (rhapontigenin, piceatannol, resveratrol) inhibited iNOS induction.