Spectroscopic Studies of Cutaneous Photosensitizing Agents—iv. The Photolysis of Benoxaprofen, an Anti‐inflammatory Drug With Phototoxic Properties

Benoxaprofen [2‐(4‐chlorophenyl)‐α‐methyl‐5‐benzoxazole acetic acid] is an anti‐inflammatory drug that causes acute phototoxicity in many patients. Photolysis studies in organic solvents (ethanol, benzene, dimethylsulfoxide) showed that benoxaprofen underwent both Type I and Type II reactions. Irradiation of an anerobic solution of benoxaprofen in ethanol resulted in hydrogen abstraction from the solvent to yield hydroxyethyl and ethoxyl radicals. In the presence of oxygen, superoxide, singlet oxygen and hydroxyethyl radicals were detected. Photolysis of benoxaprofen in air‐saturated benzene or dimethylsulfoxide gave superoxide. However, under anerobic conditions the drug yielded a carbon‐centered radical in benzene that could not be identified. These findings suggest that both oxygen‐dependent and oxygen‐independent processes may be important in the phototoxic reactions of benoxaprofen.