Ciprofloxacin-Tethered 1,2,3-Triazole Conjugates: New Quinolone Family Compounds to Upgrade Our Antiquated Approach against Bacterial Infections

A newer ciprofloxacin series containing 1,2,3-triazole conjugates of ciprofloxacin was designed, synthesized, and well characterized using modern analytical techniques by reacting diversified anilines with ciprofloxacin obtained from ciprofloxacin hydrochloride. The newer conjugates were evaluated for their antimicrobial activity against various strains, viz. Staphylococcus aureus (ATCC25923), Enterococcus faecalis (clinical isolate), Staphylococcus epidermidis (ATCC3594), Escherichia coli (ATCC25922), Pseudomonas aeruginosa (ATCC27853), Salmonella typhi (clinical isolate), Salmonella typhimurium (clinical isolate), Acinetobacter baumannii (ATCC19606), Aeromonas hydrophila (ATCC7966), Plesiomonas shigelloides (ATCC14029), and Sphingo biumpaucimobilis (MTCC6362) in vitro. Interestingly, some of the conjugates showed superior antimicrobial activity as compared to the control drug ciprofloxacin. The three compounds 4i, 4j, and 4n showed strong activity with minimum inhibitory concentration (MIC) 0.78 mu M, while the compound 4g showed MIC 1.56 mu M against S. typhi (clinical). The compound 4a showed good efficacy against S. aureus (ATCC25923) and S. typhi (clinical) with MIC 3.12 mu M, while the compound 4b exhibited efficacy with MIC 3.12 mu M against S. aureus (ATCC25923) and the control drug ciprofloxacin showed MIC 6.25 mu M. Among all of the synthesized compounds, 4e, 4f, 4g, 4h, 4p, 4q, 4t, and 4u displayed less than 20% hemolysis, while the rest of the compounds showed hemolysis in the range of 21-48%. Moreover, the structure of compound 4b was also established by single-crystal X-ray diffraction studies.