Photooxidation of hypotaurine taurine in the presence of flavins

Irradiation of organic sulfinates such as hypotaurine and cysteine sulfinic acid in the presence of catalytic amounts of flavins led to the oxidation of its sulfinic groups (-SO2H) to the corresponding sulfonates. The process of hypotaurine oxidation in the presence of riboflavin, followed by absorbance decrease at 220 nm and by ion-exchange chromatography, showed a pseudo-first-order kinetics at pH 6.0. The k value depended linearly on flavin concentrations. The reaction rate was higher at acidic pH. Although the reaction rate was not affected by the addition of superoxide dismutase or catalase, superoxide ions were supposed to be by-products of the reaction. The effectiveness of allyl alcohol as a scavenger pointed to a free-radical mechanism of the reaction. We propose a new reaction mechanism involving sulfinic radicals on this photochemical reaction.