Antitubercular and antibacterial activities of isoxazolines derived from natural products: Isoxazolines as inhibitors of Mycobacterium tuberculosis InhA

Abstract

Isoxazoline derivatives of the natural products eugenol, 1’-S-acetoxychavicol acetate and sclareol are prepared through 1,3-dipolar cycloaddition reactions in an aqueous buffered system. The compounds are evaluated for their antitubercular and antibacterial activities. Compounds 2, 2a and 3f display strong antitubercular activity with minimum inhibitory concentration values of 26.68, 17.89 and 14.58 µM, respectively. Furthermore, derivative 3f exhibits antibacterial activity against Bacillus cereus (minimum inhibitory concentration value of 29.16 µM). Isoxazoline derivatives of 1’-S-acetoxychavicol acetate demonstrate improvements in cytotoxicity, and derivative 3f of sclareol demonstrates improved antitubercular and antibacterial activities. Isoxazolines derived from natural products exhibit Mycobacterium tuberculosis enoyl-acyl carrier protein reductase (InhA) inhibitory activity, and molecular modelling predicts that they form hydrogen bonding and hydrophobic interactions with NADH and with the key residues of the InhA binding site.