Synthesis and antitubercular and antibacterial activity of some active fluorine containing quinoline–pyrazole hybrid derivatives

Abstract

In an attempt to develop newer antitubercular and antibacterial agents against the increasing bacterial resistance, we have designed new quinoline–pyrazole analogs (8a–u) following the molecular hybridization approach. The structure of one of the final compounds, 8a was unambiguously confirmed by single crystal X-ray diffraction (SC-XRD) analysis. The target compounds were evaluated for their antitubercular activity against Mycobacterium tuberculosis and antibacterial activity against three common pathogenic bacterial strains. Four derivatives (8b, 8c, 8j and 8o) displayed significant antitubercular activity. The compounds derived from 8-trifluoromethylquinoline and 6-fluoroquinoline scaffolds with halogen substitution on the pyrazole ring exhibited superior inhibition activity than corresponding 6-methoxyquinoline analogs. The cytotoxic studies revealed that the active compounds are nontoxic to normal Vero cell lines with selectivity index values ≥10, which indicate the suitability of these compounds for further drug development. The in silico molecular docking study demonstrated strong binding affinity of the compounds with the target enzymes (InhA, CYP121 and TMPK) of M. tuberculosis. Further, the in vitro antibacterial activity of compounds 8b, 8c, 8d and 8g is comparable with that of the reference drug, Ciprofloxacin.