The phototoxic antibacterial drug prulifloxacin (PLF, 1) is photolabile under aerobic condition in UV-A light. Irradiation of a phosphate buffer solution of 1 under oxygen atmosphere produces one major photoproduct, 6-fluoro-1-methyl-4-oxo-7-[piperazin-1-yl]-1,4-dihydro- [1,3]thiazeto[3,2-a] quinoline-3-carboxylic acid (2).The formation of product was explained by oxidative photodegradation of prulifloxacin in an irreversible trapping of the selfphotogenerated 1O2 by the type II photodynamic action of the drug. The generation of singlet oxygen during photolysis was confirmed by singlet oxygen scavenger sodium azide (NaN3).
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