PHOTOGENERATION OF FLUORIDE BY THE FLUOROQUINOLONE ANTIMICROBIAL AGENTS LOMEFLOXACIN AND FLEROXACIN

The photolysis (>320 nm) of the fluoroquinolone antibacterial agents l omefloxacin and fleroxacin results in the loss of their Fs atoms as fl uoride. The quantum yield for lomefloxacin was 0.98 at pH 7.4. The mec hanism probably involves aryl-F heterolysis from the S-1 state with th e concomitant generation of a carbene at C-8, In contrast, the monoflu orinated fluoroquinolones norfloxacin and ciprofloxacin do not generat e fluoride upon irradiation. Carbenes are highly reactive species that undergo addition, insertion and abstraction reactions and can cause D NA cleavage. These findings may explain why lomefloxacin and fleroxaci n are more photomutagenic and photocarcinogenic than fluoroquiuolones in which C-8 is either unsubstituted or bears a substituent other than fluorine.