Synthesis, in Vitro and in Silico Studies of Some Novel 5-Nitrofuran-2-yl Hydrazones as Antimicrobial and Antitubercular Agents

In this study, we synthesized two series of novel 5-nitrofuran-2-carbohydrazides 21a-h and 22a-e in addition to a third series of thiophene-2-carbohydrazides 23a-g to develop potent antimicrobial and/or antitubercular agents. The newly synthesized compounds were evaluated in vitro for their antimicrobial and antimycobacterial activities. Most of the 5-nitrofuran-2-carbohydrazides 21a-h and 22a-e displayed variable activity against Aspergillus fumigates, Staphylococcus aureus, Streptococcus pneumonia, Bacillis subtilis, Salmonella typhimurium, Klebsiella pneumonia, Escherichia coli and Mycobacterium tuberculosis. The sulfonamide derivative 21f exhibited superior potency and broad-spectrum antimicrobial activity with minimum inhibitory concentration (MIC)=0.06-0.98 µg/mL and antimycobacterial activity with MIC=3.9 µg/mL. The 5-nitrofuran-2-carbohydrazides 21a, b, g, h and 22a-c exhibited significant antibacterial activity with MIC values in the range of 0.12-7.81 µg/mL. The significances of the 5-nitrofuran moiety and sulfonamide function were explored via the structure-activity relationship (SAR) study. In addition, docking studies revealed that the p-amino benzoic acid (PABA) and binding pockets of the dihydropteroate synthase (DHPS) were successfully occupied by compound 21f. Furthermore, two quantitative structure-activity relationship (QSAR) models were built to explore the structural requirements which controlled the activity.