Antioxidant activity and inhibition of alpha-glucosidase by trans-resveratrol, piceid, and a novel trans-stilbene from the roots of Israeli Rumex bucephalophorus L.
The roots of Rumex bucephalophorus, collected in Israel, were analyzed for trans-stilbenes. Two stilbene-O-glycosyl derivatives were identified, in addition to 3,5,4'-trihydroxystilbene (1) (resveratrol). The stilbene-O-glycosyl derivatives were 5,4'-dihydroxystilbene-3-O-beta-d-glucopyranoside (2) (piceid) and the new 5,4'-dihydroxystilbene-3-O-alpha-arabinopyranoside (3), which is being named rumexoid. The structure of rumexoid was elucidated by using spectroscopic data. The antioxidant capacities of stilbenoids 1-3 were determined and expressed as trolox equivalent antioxidant capacity (TEAC). TEAC value for trans-resveratrol was highest (2.7) and for rumexoid lowest (1.5). In vitro, trans-resveratrol and rumexoid demonstrated a potent inhibitory effect on alpha-glucosidase activity (IC50 < 0.1 and < 0.5 mM, respectively). The commercial antidiabetic agent acarbose was shown to inhibit only 35% of the enzyme activity at 0.5 mM. The addition of piceid to the reaction mixture did not inhibit alpha-glucosidase in vitro in the range of concentrations used. These findings extend the range of reported beneficial effects of stilbene derivatives, and demonstrate the multifaceted activities that dietary polyphenols may exert in the intestine, where their concentrations are highest in the body.
Institute of Biochemistry, Food Science, and Nutrition, The Faculty of Agricultural, Food, and Environmental Quality Sciences, The Hebrew University of Jerusalem, P.O. Box 12, Rehovot 76100, Israel. kerem@agri.huji.ac.il
Zohar
Z
Kerem
Itzhak
I
Bilkis
Moshe A
MA
Flaishman
Lior
L
Sivan
D000975:Antioxidants / Q000494:pharmacology*; D002851:Chromatography, High Pressure Liquid; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005960:Glucosides / Q000494:pharmacology*; D065089:Glycoside Hydrolase Inhibitors; D009682:Magnetic Resonance Spectroscopy; D018517:Plant Roots / Q000737:chemistry; D019664:Polygonaceae / Q000737:chemistry*; D000077185:Resveratrol; D013267:Stilbenes / Q000494:pharmacology*
D000975:Antioxidants; D004791:Enzyme Inhibitors; D005960:Glucosides; D065089:Glycoside Hydrolase Inhibitors; D013267:Stilbenes; D000077185:Resveratrol; C058229:polydatin