Dietary bioflavonoids inhibit Escherichia coli ATP synthase in a differential manner

The aim of this study was to determine if the dietary benefits of bioflavonoids are linked to the inhibition of ATP synthase. We studied the inhibitory effect of 17 bioflavonoid compounds on purified F-1 or membrane bound F1F0 E. coli ATP synthase. We found that the extent of inhibition by bioflavonoid compounds was variable. Morin, silymarin, baicalein, silibinin, rimantadin, amantidin, or, epicatechin resulted in complete inhibition. The most potent inhibitors on molar scale were morin (IC50 similar to 0.07 mm) > silymarin (Ic(50) similar to 0.11 mM)> baicalein (IC50 similar to 0.29 mm)> silibinin (IC50 similar to 0.34 mM)> rimantadin (IC50 similar to 2.0 mM)> amantidin (IC50 similar to 2.5 mM)> epicatechin (IC50 similar to 4.0 mM). Inhibition by hesperidin, chrysin, kaempferol, diosmin, apigenin, genistein, or rutin was partial in the range of 40-60% and inhibition by galangin, daidzein, or luteolin was insignificant. The main skeleton, size, shape, geometry, and position of functional groups on inhibitors played important role in the effective inhibition of ATP synthase. In all cases inhibition was found fully reversible and identical in both F1F0 membrane preparations and isolated purified F-1. ATPase and growth assays suggested that the bioflavonoid compounds used in this study inhibited F-l -ATPase as well as ATP synthesis nearly equally, which signifies a link between the beneficial effects of dietary bioflavonoids and their inhibitory action on ATP synthase. (C) 2010 Elsevier B.V. All rights reserved.