PULSE-RADIOLYSIS STUDY OF ONE ELECTRON OXIDATION OF RIBOFLAVIN

One electron oxidation of riboflavin (Rf) has been studied using various oxidising species such as Cl2-., SO4-. and OH radicals. The transient species produced by the reaction of SO4-. with riboflavin gave spectra with lambda-m at 680 and 640 nm at pHs 4 and 7.1 respectively with a pK(a) at approximately 6. Cl2-. radicals reacted with riboflavin to give a transient spectrum with lambda-m at 570 nm. The possibility of two sites viz. C-8 methyl group and the extended pi-ring system of the molecule for oxidation reaction are discussed. The reaction of Cl2-. with riboflavin is an equilibrium from which the redox potential for the Rf+./Rf couple has been evaluated to be 2.28 V vs NHE. OH radicals reacted with riboflavin to give a transient spectrum attributable to a mixture of species produced by addition or abstraction reactions.