SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS—I. SPIN TRAPPING OF PHOTOLYSIS PRODUCTS FROM SULFANILAMIDE, 4‐AMINOBENZOIC ACID AND RELATED COMPOUNDS

Abstract
—: The photodecomposition of sulfanilamide, 4‐aminobenzoic acid and other related analogs has been studied with the aid of the spin trap 2‐methyl‐2‐nitrosopropane. UV photolysis of an aqueous solution of sulfanilamide yielded the following radicals C˙6H4SO2NH2, C6H5SO, S˙O2NH2 and SO (or SO2dot;). Under the same conditions 4‐aminobenzoic acid gave C˙6H4COOH. In addition both sulfanilamide and 4‐aminobenzoic acid, but not 4‐dimethylaminobenzoic acid, generated eaq or hydrogen atoms during UV irradiation. The C6H4SO2NH2 radical was also produced by photolysis of 4‐iodobenzenesul‐fonamide and 4‐nitrobenzenesulfonamide. The C6H4COOH radical was generated by photolysis of 4‐nitrobenzoic acid and 4‐iodobenzoic acid. Finally the C6H4NO2 radical was formed during the irradiation of 4‐nitroaniline, 1,4‐dinitrobenzene and 4‐iodonitrobenzene. The free radicals generated by sulfanilamide and 4‐aminobenzoic acid may play an important role in the phototoxic and photoallergic responses elicited by these drugs in certain individuals.

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