The chemical and biological aspects of fluoroquinolones: reality and dreams

A vast array of fluoroquinolones having excellent broad-spectrum activity form an invaluable part of the present anti-infective armory of the clinicians. A number of these compounds are today's blockbusters of the antibacterial market due to their therapeutic efficacy having tolerable side effects and thus challenging the predominance of well established beta-lactam antibiotics which are becoming more prone to the resistant pathogenic bacteria. Since the discovery of nalidixic acid the development of fluoroquinolones has experienced an exponential growth and is being continued with more vigor to obtain better drugs having multifunctional action. This article attempts to review the current developments of the chemical and biological aspects of fluoroquinolones in a chronological manner touching upon their antibacterial properties based on the structure activity relationship while pointing out to their mode of action. It also provides an insight into a variety of approaches resulting in elegant manipulations of their basic skeleton and some breakthroughs in their synthetic strategies of a few widely used drugs, which had helped in accelerating their market growth as well as continuing research for newer fluoroquinolones. Since the mode of action of fluoroquinolones being different from beta-lactams and their transportation to the target site is slow several dual action quinolonyl-beta-lactams (Penicillins, Cephalosporins, Penems, Cephems, Carbapenams etc.) have come as a major breakthrough among the hybrid antibiotics. While focusing on the multifunctional activities of such compounds, this review briefly points out to the current trends in various techniques for de novo drug design and development of newer therapeutic molecules, which hold future promises in combating the fight against drug resistant bacteria as it still remains to be won.