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.