Design, synthesis, and antibacterial evaluation of new Schiff’s base derivatives bearing nitroimidazole and pyrazole nuclei as potent E. coli FabH inhibitors

New Schiff’s base derivatives 5a–j have been synthesized by reaction between 5-aryloxypyrazole-4-carbaldehydes 3a–j and 2-(2-methyl-5-nitro-1H-imidazol-1-yl)acetohydrazide 4 in the presence of nickel (II) nitrate as a catalyst in ethanol at room temperature with good yield (75–88 %). All compounds were tested for antibacterial properties and inhibition of E. coli FabH. Of the compounds studied, the majority of the compounds showed effective antibacterial properties and inhibition of E. coli FabH activity. Compound 5i showed the most effective inhibition (IC50 = 4.6 ± 0.2 µM) by binding into the active site of the E. coli FabH receptor with minimum binding energy (ΔGb = −54.2961 kcal/mol). The binding was stabilized by two hydrogen bonds, two π–π, and three π–cation interactions.