Synthesis and Biological Evaluation of Some Novel Mannich Bases of Isoxazoline Derivatives as Possible Antimicrobial Agents

Abstract

Novel isoxazoline derivatives were synthesized by condensation of substituted acetophenones with aldehyde in presence of alcoholic NaOH to get intermediate chalcones, which were further treated with hydroxylamine hydrochloride in presence of sodium hydroxide to get isoxazoline derivatives. The latter were refluxed separately with isonicotinic acid hydrazide and sulphanilamide in presence of formaldehyde for 6-10 h to afford corresponding Mannich bases. The structures of synthesized compounds were established on the basis of melting point, TLC, IR, 1H NMR and HRMS. Antimycobacterial activity of compounds (3a-j) were assessed against M. tuberculosis (vaccine strain, H37 Rv strain) ATCC27294 using microplate Alamar Blue assay (MABA). Further the derivatives were evaluated for the antibacterial activity against Gram positive bacteria S. aureus (ATCC 9144), S. epidemidis (ATCC12228) and Gram negative bacteria E. coli (ATCC 25922), Klebsiella (ATCC 4352), while antifungal activity against A. flavus (ATCC 9643) and A. niger (ATCC 16404) by using agar well diffusion method using ciprofloxacin and fluconazole as standards, respectively. The results of antimicrobial studies showed that some of the derivatives posses mild to moderate biological activity as compared to standard.