ESR DETECTION OF FREE-RADICAL AND ACTIVE OXYGEN SPECIES GENERATED DURING PHOTOLYSIS OF FLUOROQUINOLONES

The photolysis of six fluoroquinolone agents was investigated in neutr al aqueous solution by means of ESR spectroscopy. Lomefloxacin (LFLX), sparfloxacin (SPFX), ciprofloxacin (CPFX), enoxacin (ENX) and sitaflo xacin (STFX) generated free radicals in the process of photochemical d egradation, while levofloxacin (LVFX) did not. The free radicals and a ctive oxygen species observed were presumed to be carbon-centered radi cal (. C), hydroxyl radical (. OH) and singlet oxygen (O-1(2)), No sup eroxide anion radical (O-2(.-)) was detected by the 5,5-dimethylpyrrol ineN-oxide (DMPO) spin trapping method in our system. 8-Fluorine-subst ituted fluoroquinolones (LFLX, SPFX) produced . C, and generated a hig h degree of O-1(2). On the other hand, the fluoroquinolones which have hydrogen, oxygen or chlorine at the 8-position (CPFX, LVFX, STFX) did not produce . C, and generated a low degree of O-1(2). ENX produced . C, and generated a low degree of O-1(2). These results suggest that t he nature of the substituent at the 8-position of the fluoroquinolone ring plays an important role in the formation of free radicals and act ive oxygen species during photoirradiation.