By bioassay-guided separation, three stilbenes (rhapontigenin, piceatannol, and resveratrol), two stilbene glucoside gallates (rhaponticin 2''-O-gallate and rhaponticin 6"-O-gallate), and a naphthalene glucoside (torachrysone 8-O-beta -D-glucopyranoside) with inhibitory activity against nitric oxide (NO) production in lipopolysaccharide-activated macrophages were isolated (IC50 = 11-69 muM). The oxygen functions (-OH, -OCH3) of stilbenes at the benzene ring were essential for the activity. The glucoside moiety reduced the activity, while the alpha,beta -double bond had no effect. Furthermore, the active stilbenes (rhapontigenin, piceatannol, and resveratrol) did not inhibit inducible NO synthase activity, but they inhibited nuclear factor-kappaB activation following expression of inducible NO synthase. (C) 2001 Elsevier Science Ltd. All rights reserved.
Effects of stilbene constituents from rhubarb on nitric oxide production in lipopolysaccharide-activated macrophages
Two new anthraquinone glucosides [chrysophanol 8-O-beta-D-(6'-galloyl)-glucopyranoside, aloe-emodin 1-O-beta-D-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-beta-D-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 mu M). 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 alpha,beta-double bond did not affect the activity. Furthermore; the active stilbenes (rhapontigenin, piceatannol, resveratrol) inhibited iNOS induction. (C) 2000 Elsevier Science Ltd. All rights reserved.