Novel 6,8-dibromo-4(3H)quinazolinone derivatives of anti-bacterial and anti-fungal activities.

Starting from 4-(6,8-dibromo-2-phenyl-4-oxo-(4H)-quinazolin-3-yl)-benzoic acid ethyl ester (II) and its acid hydrazide III, a new series of Schiff bases IV and their cyclized products, thiazolidinones V, oxadiazole VIII, pyrazoles X-XII, pyrroles XIII-XV and other related products were synthesized. These compounds were screened for their anti-bacterial activity against Gram-positive bacteria (Staphylococcus aureus, Legionella monocytogenes and Bacillus cereus) and Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa and Salmonella typhimurium) and anti-fungal activity (Candida albicans and Aspergillus flavus) using paper disc diffusion technique. The minimum inhibitory concentrations (MICs) of the compounds were also determined by agar streak dilution method. Among the synthesized compounds 2-(4-(2-phenyl-6,8-dibromo-4-oxo-(4H)quinazolin-3-yl)-N-ethylamido benzoic acid hydrazide VIIa was found to exhibits the most potent in vitro anti-microbial activity with the MICs of 1.56, 3.125, 1.56, 25, 25 and 25 microg/ml against E. coli, S. typhimurium, L. monocytogenes, S. aureus, P. aeruginosa, and B. cereus respectively. Compound 2-(4-(2-phenyl-6,8-dibromo-4-oxo-(4H)quinazolin-3-yl)-N-methyl thioamido benzoic acid hydrazide VIIc was found to exhibit the most potent in vitro anti-fungal activity with MICs 0.78 and 0.097 microg/ml against C. albicans and A. flavus.