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 H 2 O 2 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 H 2 O 2 . The data obtained can be useful for understanding the physiological role of thiols in oxidative processes.