Kinetic characteristics of the reaction of natural thiols with peroxyl radicals and hydrogen peroxide

Kinetic characteristics of the reaction between natural thiols, viz., glutathione, cysteine, and homocysteine, and peroxyl radicals formed upon decomposition of the azo initiator AAPH (2,2´-azobis(2-methylpropionamidine) dihydrochloride) in aqueous solutions at 37 °С were determined by the competing reaction method. The kinetics of radicals formation in the reaction between natural thiols and H2O2 was studied by the inhibitor method. The polymethine dye, pyridinium 3,3´-di-γ-sulfopropyl-9-methylthiacarbocyanine, was used as the radical scavenger. Cysteine was found to exhibit the highest activity in the reactions with peroxyl radicals and in the free radical generation upon the reaction with H2O2. The data obtained can be useful for understanding the physiological role of thiols in oxidative processes.