Synthesis, antibacterial, and cytotoxic evaluation of certain 7-substituted norfloxacin derivatives

We report herein the synthesis and biological evaluation of two series of 7-substituted norfloxacin derivatives. Most compounds tested in this study demonstrated better activity against methicillin-resistant Staphylococcus aureus than norfloxacin. Preliminary in vitro evaluation indicated that the 7-[4-(2-hydroxyiminoethyl)piperazin-1-yl] derivatives 3b-e possess distinct cytotoxicity profiles as compared with their alpha-methylene-gamma-butyrolactone counterparts, 4b,e: i.e., excellent activities against the renal cancer subpanel. Among them, 1-ethyl-6-fluoro-7-{4-[2-(4-chlorophenyl)-2-hydroxyiminoethyl]-1-piperazinyl}-4-oxo-1,4-dihydro-3-quinolinecarboxylic acid (3d) demonstrated the most significant activities against renal cancer cell lines, with log GI(50) values of -6.40 against CAK-1, -6.14 against RXF 393, and -7.54 against UO-31, compared with a mean log GI(50) value of -5.03.