Design and syntheses of some new quinoxaline derivatives containing pyrazoline residue as potential antimicrobial agents

A series of 3-[{5-(substituted-phenyl)-3-(phenyl/4-methoxyphenyl)-4,5-dihydro-1H-pyrazol-1-yl}carbonyl]quinoxalin-2-ol derivatives (3–24) were synthesized by reacting 2-hydroxy quinoxaline-3-hydrazide with different substituted 1,3-diphenyl prop-2-en-1-ones in absolute ethanol. The structures of all the compounds were established on the basis of spectral data (IR, 1H NMR 13C NMR, and mass) and elemental analysis. All the newly synthesized compounds were examined for their in vitro antimicrobial activity against Staphylococcus aureus, Escherichia coli, Penicillium citrinum, and Aspergillus niger by the agar-well diffusion method employing ofloxacin and ketoconazole as reference drugs. All the tested compounds were found to possess substantial antimicrobial activity. Compound 5 and 12 showed excellent antibacterial and antifungal activity against all the tested strains. It was interesting and encouraging to note that all the compounds established high-antifungal activity than standard drug ketoconazole against P. citrinum.