UV-induced photoproducts of para-aminobenzoid acid

Cis- and trans- 4,4'-azodibenzoic acid (AZBA), two photoproducts of para-aminobenzoic acid (PABA), formed by the action of 313 nm light, have been characterized on the basis of UV and mass spectral data. The relative dose of UV light required for azodibenzoic acid formation is comparable to that obtained from a day of sunbathing. The same type of photochemical reaction could lead to the formation of PABA-protein conjugates. These photoproducts may be responsible for the known photosensitizing properties of PABA and perhaps its cytotoxic and mutagenic effects.