stilbenes and isoquercitrin

We have studied the inhibitory effect of five polyphenols namely, resveratrol, piceatannol, quercetin, quercetrin, and quercetin-3-beta-D glucoside on Escherichia coli ATP synthase. Recently published X-ray crystal structures of bovine mitochondrial ATP synthase inhibited by resveratrol, piceatannol, and quercetin, suggest that these compounds bind in a hydrophobic pocket between the gamma-subunit C-terminal tip and the hydrophobic inside of the surrounding annulus in a region critical for rotation of the gamma-subunit. Herein, we show that resveratrol, piceatannol, quercetin, quercetrin, or quercetin-3-beta-d glucoside all inhibit E. coli ATP synthase but to different degrees. Whereas piceatannol inhibited ATPase essentially completely ( approximately 0 residual activity), inhibition by other compounds was partial with approximately 20% residual activity by quercetin, approximately 50% residual activity by quercetin-3-beta-D glucoside, and approximately 60% residual activity by quercetrin or resveratrol. Piceatannol was the most potent inhibitor (IC(50) approximately 14 microM) followed by quercetin (IC(50) approximately 33 microM), quercetin-3-beta-D glucoside (IC(50) approximately 71 microM), resveratrol (IC(50) approximately 94 microM), quercitrin (IC(50) approximately 120 microM). Inhibition was identical in both F(1)F(o) membrane preparations as well as in isolated purified F(1). In all cases inhibition was reversible. Interestingly, resveratrol and piceatannol inhibited both ATPase and ATP synthesis whereas quercetin, quercetrin or quercetin-3-beta-d glucoside inhibited only ATPase activity and not ATP synthesis.

Topics: ATP Synthetase Complexes; Escherichia coli; Inhibitory Concentration 50; Models, Molecular; Molecular Structure; Proton Pumps; Quercetin; Resveratrol; Stilbenes

Phenolic profile of 10 different varieties of red "Vinho Verde" grapes (Azal Tinto, Borraçal, Brancelho, Doçal, Espadeiro, Padeiro de Basto, Pedral, Rabo de ovelha, Verdelho and Vinhão), from Minho (Portugal) were studied. Nine Flavonols, four phenolic acids, three flavan-3-ols, one stilben and eight anthocyanins were determined. Malvidin-3-O-glucoside was the most abundant anthocyanin while the main non-coloured compound was much more heterogeneous: catechin, epicatechin, myricetin-3-O-glucoside, quercetin-3-O-glucoside or syringetin-3-O-glucoside. Anthocyanin contents ranged from 42 to 97%. Principal component analysis (PCA) was applied to analyse the date and study the relations between the samples and their phenolic profiles. Anthocyanin profile proved to be a good marker to characterize the varieties even considering different origin and harvest. "Vinhão" grapes showed anthocyanins levels until twenty four times higher than the rest of the samples, with 97% of these compounds.

Topics: Anthocyanins; Catechin; Flavonoids; Flavonols; Glucosides; Hydroxybenzoates; Phenols; Pigments, Biological; Quercetin; Stilbenes; Vitis