Kinetic study of the oxidation of catechin and rutin, subclass of flavonoids mainly found in teas and red wine, by Ru(NH3)5L3+(L=pzCH3+,pz, isn) complexes were carried out over a pH range 0-7.6.The rate law of the reaction involves a rate determining step of one electron oxidation of the flavonoids in the form of H2X (k0), HX- (k1) and X2- (k2) by Ru(NH3)5L3+ complexes to from the cooresponding radicals, following the rapid scavenge of radicals by Ru(lll) complexes. The rate constants of oxidation in different forms of flavonoids were summarized in Table 1. With the measured k0, k1 and k2, the self-exchange rate constants (kex) can be calculated on the basis of Marcus theory, and the results are listed in Table 2. The comparison of kex of flavonoids with that of the catechol and the ascorbic acid suggest that active sites of flavonoids with that of the catechol and the ascorbic acid suggest that the active sites of oxidation go to the catechol ring of the flavonoids and the antioxidative reactivity of flavonoids is greater than that of the ascorbic acid by at least 3 orders of magnitude.
