Riboflavin-Sensitized Photooxidation of Phenothiazines in Aqueous Solution by Laser-Irradiation

Abstract

A laser-irradiation (490 nm) of the tranquilizing phenothiazines such as chlorpromazine, propericiazine, prochlorperazine, and promethazine in the presence of riboflavin gave the corresponding sulfoxides in an acidic buffer solution (pH 4.0). Fluorescence quenching and visible absorption changes of riboflavin by the binding to phenothiazines were quantitatively treated to obtain the equilibrium constants (K_c) of the complexes. The larger the K_c values, the greater the extent of photolysis was observed. Riboflavin-sensitized photooxidation was discussed on the basis of the complex formation between riboflavin and phenothiazines.