Targeting drug-resistant tuberculosis: Thioacetamide-substituted benzothiazoles as bactericidal agents inhibiting type II NADH dehydrogenase.

The identification of novel anti-tubercular agents that inhibit the function of less-explored yet essential components of Mycobacterium tuberculosis is critically needed to address the increasing prevalence of drug-resistant tuberculosis. The type II NADH dehydrogenase, an indispensable component of the oxidative phosphorylation pathway, is the entry point of electrons into the electron transport chain, facilitating ATP production. This enzyme is a promising drug target because its inhibition leads to a bactericidal response through energy starvation. In our study, we synthesized a series of 6-isopropyl benzothiazole derivatives, with various thioacetamide side chains; and assessed their anti-tubercular efficacy, and specificity toward NADH dehydrogenase through in vitro studies. The most potent compounds, C4-1 (MIC = 4 μg/mL, 13.042 μM), and C4-11 (MIC = 8 μg/mL, 24.80 μM), exhibited inhibitory effects against mycobacterial strains, exhibiting resistance to FDA approved anti-tubercular drugs; and demonstrated bactericidal activity with a safety index exceeding 10. The primary target for these derivatives is proposed to be type II NADH dehydrogenase, indicated by increased NADH/NAD+ ratios in the peredox mCherry assay, and from detection of single-nucleotide polymorphisms at multiple points in the type II NADH dehydrogenase gene coding sequence of the strains, exhibiting resistance to the compounds C4-1, and C4-11. Additionally, molecular docking, molecular dynamics, and in silico ADME profiling were performed on the active compounds.