The reaction of catechin and rutin with Ru(NH3)(5)L3+ (L = N-methylpyrazinium (pzCH(3)(+)), pyrazine (pz), and isonicotinamide (isn)) complexes underwent a two-electron oxidation on the catechol ring (B ring) with the formation of quinone products. The kinetics of the oxidation, carried out at [H+] = 0.01 -1.0 M and pH = 4.0-7.6, suggested that the reaction process involves the rate determining one-electron oxidation of the flavonoids in the form of H2X (k(0)), HX-(k(1)), and X2- (k(2)) by Ru(NH3)(5)L3+ Complexes to form the corresponding semiquinone radicals, followed by the rapid scavenge of the radicals by the Ru(III) complexes. The specific rate constants (k(0), k(1), and k(2)) were measured and the results together with the application of the Marcus theory were used to estimate the self-exchange parameters for the one-electron couples of the flavonoids, H2X/H2X+center dot, HX-/HX center dot, and X2-/X-center dot.