In Vitro Antimycobacterial Activity and Physicochemical Characterization of Diaryl Ether Triclosan Analogues as Potential InhA Reductase Inhibitors

Two sets of diphenyl ether derivatives incorporating five-membered 1,3,4-oxadiazoles, and their open-chain aryl hydrazone analogs were synthesized in good yields. Most of the synthesized compounds showed promising in vitro antimycobacterial activity againstMycobacterium tuberculosisH37Rv. Three diphenyl ether derivatives, namely hydrazide3, oxadiazole4and naphthylarylidene8gexhibited pronounced activity with minimum inhibitory concentrations (MICs) of 0.61, 0.86 and 0.99 mu g/mL, respectively compared to triclosan (10 mu g/mL) and isoniazid (INH) (0.2 mu g/mL). Compounds3,4, and8gshowed the InhA reductase enzyme inhibition with higher IC(50)values (3.28-4.23 mu M) in comparison to triclosan (1.10 mu M). Correlation between calculated physicochemical parameters and biological activity has been discussed which justifies a strong correlation with respect to the inhibition of InhA reductase enzyme. Molecular modeling and drug-likeness studies showed good agreement with the obtained biological evaluation. The structural and experimental information concerning these three InhA inhibitors will likely contribute to the lead optimization of new antibiotics forM. tuberculosis.