Pharmacophoric screening of newly synthesized isoniazid derivatives and their antimycobacterial activity

Mycobacterium tuberculosis is clinically recognized as a causative agent of Tuberculosis. Keeping in view, this study was endeavored to screen our previously synthesized seventeen INH analogues for their antimycobacterial potential using proportion method. During this process, INH and all the seventeen compounds were examined at different concentrations of 0.05, 0.1 and 0.2μg/mL which were prepared using Lowenstein-Jensen (LJ) base. For drug susceptibility test, three Mycobacterial strains ATCC H37Rv, known INH-sensitive and INH-resistant strains were selected, sub-cultured on LJ Medium and serial diluted to achieve 1:10, 1:100, 1:1000 and 1:10000 from calibrated bacterial suspension Mcfarland No. 1. Dilutions of 1:100 and 1:10000 were added to drug free medium and 1:100 bacterial suspension was added to each of the test concentrations and finally incubated for 4-6 weeks at 37°C. It was observed that only compounds II and XI were active against MTb. Compounds III, IX and X also showed activity but were less potent. Ligand Scout 3.02[il_10] was used to perform pharmacophore-based screening where important pharmacophoric features were identified in the structures of these compounds which could be related to their observed antimycobacterial activity.