Photodegradation Kinetics of the New Antibacterial Fluoroquinolone Derivative, Orbifloxacin, in Aqueous Solution

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The photodegradation kinetics of orbifloxacin (1-cyclopropyl-5,6,8-trifluoro-1,4-dihydro-7-(cis-3,5-dimethyl-1-piperazinyl)-4-oxoquinoline-3-carboxylic acid) was investigated in aqueous solution at various pH values (1.2-12.5) and at an ionic strength of 0.5. The photodegradation experiments were performed using a fluoroscent or a chemical lamp as a light source and the cummulative number of photons during exposure was determined by a ferroxalate actinometer. It was found that the photodegradation of orbifloxacin followed apparent first-order kinetics under both types of artificial light. The photodegradation rates of orbifloxacin in a neutral medium were higher than those in acidic and alkaline media. Orbifloxacin was most unstable in solution at pH 7.4,and its degradation half-life was 0.9 h. Also, the log k-pH profile indicated that the photodegradation rate of orbifloxacin was related to the dissociation of the carboxylic and dimethylpiperazinyl groups and the main photo-labile species was the zwitterionic form. In addition, the photodegradation kinetics of the decarboxylated derivative of orbifloxacin in aqueous solution was investigated to determine the effect of the functional groups on the photodegradation of orbifloxacin.
公益社団法人日本薬学会の論文
1995-06-15