Photochemical Transformation of Flouroquinolone Antibiotic Drug- Besifloxacin

In the present study, the photochemistry of flouroquinolone antibiotic drug-besifloxacin (1) was investigated under mild conditions similar to those encountered in biological systems namely aerobic as well as an anaerobic condition with UV-A light. When besifloxacin (1) was irradiated with a high-pressure mercury lamp under aerobic conditions it afforded 7-(2-Amino-5-oxopentylamino)-8-chloro-1-cyclopropyl-6-fluoro-4-oxo1, 4 dihydroquinoline-3-carboxylic acid as photoproduct (2) and under anaerobic condition it afforded 7-(3-Amino-azepan-1-yl)-1-cyclopropyl-6fluoro-8-hydroxy-4-oxo-1,4dihydro-quinoline-3-carboxylic acid as photoproduct (3). The formation of photoproduct was explained by the type-I and type II mechanism of Photosensitization. INTRODUCTION: The Interest in the topic of drug photochemistry has amplified markedly due to the awareness among the scientific community of an increase in the UV portion of the sun spectrum reaching the earth 1-3 . In the last few years majority of the work done on the mechanisms of both drug photodegradation and photosensitization, has appeared in recent reviews. 4 The mechanism of Photosensitization induced by drugs are generally considered as belonging to either type I (radical mediated) or type II (singlet oxygen mediated). 5 The interaction of many currently used drugs with UVA and UVB radiations is usually responsible for a series of photosensitizing effects, i.e. phototoxicity, photoallergy, photomutagenesis and photocarcinogenesis. QUICK RESPONSE CODE DOI: 10.13040/IJPSR.0975-8232.IJP.2(9).478-83 Article can be accessed online on: www.ijpjournal.com DOI link: http://dx.doi.org/10.13040/IJPSR.0975-8232.IJP.2(9).478-83 Thus to evaluate the photobiological risk associated with a drug, it is important to understand the molecular mechanism of drug photosensitization. 6 Fluoroquinolone drugs are the most successful largely used class of antibiotics. They are considered to be well tolerated drugs with relatively limited adverse effects. 7-9 In spite of this, they have been recognized to possess a remarkable phototoxic potential. 10-12 In order to gain insight into the molecular mechanisms of the photoinduced biological damage, a great deal of attention was recently dedicated to the study of their photochemical degradation pathways. 13 Besifloxacin is a topical ophthalmic fluroquinolone, most recentaly approved drug for the treatment of bacterial conjunctivitis caused by susceptible bacterial strains. Like other fluoroquinolones 14 (FQs), besifloxacin also targets bacterial enzymes required for DNA replication such as DNA gyrase and topoisomerase IV. 15, 16 However, besifloxacin show more balanced activity against these enzymes than do other fluroquinolone In addition, besifloxacin has been found to have greater in vitro activity than