Oxidative Cyclization of Isoniazid with Fluoroquinolones: Synthesis, Antibacterial and Antitubercular Activity of New 2,5-disubstituted-1,3,4-Oxadiazoles

We report herein one-pot synthesis and the antibacterial and antitubercular activities of 2,5-disubstituted-1,3,4-oxadiazole compounds obtained by hybridization of a well-known antitubercular agent isoniazid (INH) with four broad-spectrum antibiotics belonging to fluoroquinolone (FQ) class. The work is aimed at designing and developing potential antimicrobial agents having synergistic action due to the coupling of INH and FQ through the biologically active 1,3,4-oxadiazole nucleus. The synthesized compounds are expected to have low toxicity as compared to INH due to the absence of free hydrazide group in the chemical structure of the prepared derivatives. The antibacterial activities of the 1,3,4 oxadiazole derivatives were also tested against several Gram-positive and Gram-negative pathogenic bacterial strains. The antitubercular activity was evaluated against M. tuberculosis H(37)Rv strain, and the results were compared with that of the positive control INH. The title compounds showed excellent antimicrobial and promising antitubercular activity in comparison to the parent fluoroquinolones and INH, respectively.