Novel ofloxacin derivatives: Synthesis, antimycobacterial and toxicological evaluation

Thirty novel 9-fluoro-2,3-dihydro-8,10-(mono/di-sub)-3-methyl-8-nitro-7-oxo-7H-[1,4]oxazino[2,3,4-ij]quinoline-6-carboxylic acids were synthesized from 2,3,4,5-tetrafluoro benzoic acid and evaluated for in vitro and in vivo antimycobacterial activities against Mycobacterium tuberculosis H37Rv (MTB), multi-drug resistant Mycobacterium tuberculosis (MDR-TB), and Mycobacterium smegmatis (MC2) and also tested for the ability to inhibit the supercoiling activity of DNA gyrase from mycobacteria. Among the synthesized compounds, 10-[2-carboxy-5,6-dihydroimidazo[1,2-a]pyrazin-7(8H)-yl]-9-fluoro-2,3-dihydro-3-methyl-8-nitro-7-oxo-7H-[1,4]oxazino[2,3,4-ij]quinoline-6-carboxylic acid was found to be the most active compound in vitro with MIC99 of 0.19 μM and 0.09 μM against MTB and MTR-TB, respectively. In the in vivo animal model also the same compound decreased the bacterial load in lung and spleen tissues with 1.91 and 2.91 − log 10 protections, respectively, at the dose of 50 mg/kg body weight. Compound 10-[(4-((4-chlorophenyl)(phenyl)methyl)piperazin-1-yl)]-9-fluoro-2,3-dihydro-3-methyl-8-nitro-7-oxo-7H-[1,4]oxazino[2,3,4-ij]quinoline-6-carboxylic acid was found to be the most active in the inhibition of the supercoiling activity of DNA gyrase with an IC50 of 10.0 μg/mL. The results demonstrate the potential and importance of developing new oxazino quinolone derivatives against mycobacterial infections.