Synthesis, characterization, and biological evaluation of novel thiazole and pyrazole derivatives of quinoline-4-carboxylic acid as potential antimicrobial agents

A series of quinoline-based heterocycles prepared and bioevaluated for their possible antimicrobial activity against a panel of gram-positive bacteria Staphylococcus aureus (ATCC-9144) and Bacillus subtilis (ATCC-6633)] and gram-negative bacteria Pseudomonas aeruginosa (ATCC-25615), and Escherichia coli (MTCC-739)], and fungal strains Candida albicans (ATCC-24433), Aspergillus niger (MTCC-872), and Aspergillus fumigatus (MTCC-343)] by the known methods. All the prepared quinoline derivatives have shown significant antimicrobial activities. Few compounds, viz. 4b, 4c and 4a, 4c proved to be active at low concentrations against Sa and Ca, respectively, while compounds 4a, 6d, and 6b showed milder inhibitory effects against other microbes. The structures of newly synthesized compounds were characterized by elemental analysis, Infrared (IR), ¹HNMR, ¹³C-NMR and Mass-spectroscopy.