Enhanced Antibacterial Activity of Endo-nortropine Substituted (C-7) Fluoroquinolones Against V. cholerae, S. aureus and B. subtilis

Introduction: Bacterial infections account for maximum deaths worldwide than for any other single cause. Methods: Here in, we report a convenient synthesis of new fluoroquinolone molecules substituted with endo- nortropine and its derivatives at C-7position. All the synthesized molecules, when screened for their antibacterial activity by agar diffusion method against Vibrio cholerae, Bacillus subtilis, Staphylococcus aureus and Escherichia coli were found to be active against the first three strains. The shortlisted compounds in the series, RG and RO, were further evaluated to determine their MIC values by micro-dilution broth assay. Result & Conclusion: Compound RG was ten times more effective in case of S. aureus (15.0 nM), two times in case of V. cholerae (3.7 nM) and the same as that of standard drug Levofloxacin in case of Bacillus subtilis (7.8 nM). Compound RO also displayed an impressive MIC value (62.5 nM) in case of S. aureus as compared to control (125 nM). The results have been supported by in-silico docking studies, where increased hydrogen bonding interactions in case of RG as compared to standard drug levofloxacin with DNA gyrase (2XCT) of S. aureus resulted in decreased energy of the former. Keywords: Levofloxacin, Tropine alkaloids, DNA gyrase, Piperazine, MRSA, VRSA.