Structure elaboration of isoniazid: synthesis, in silico molecular docking and antimycobacterial activity of isoniazid-pyrimidine conjugates.

Designing small molecule-based new drug candidates through structure modulation of the existing drugs has drawn considerable attention in view of inevitable emergence of resistance. A new series of isoniazid-pyrimidine conjugates were synthesized in good yields and evaluated for antitubercular activity against the H37Rv strain of Mycobacterium tuberculosis using the microplate Alamar Blue assay. Structure-anti-TB relationship profile revealed that conjugates 8a and 8c bearing a phenyl group at C-6 of pyrimidine scaffold were most active (MIC99 10 µM) and least cytotoxic members of the series. In silico docking of 8a in the active site of bovine lactoperoxidase as well as a cytochrome C peroxidase mutant N184R Y36A revealed favorable interactions similar to the heme enzyme catalase peroxidase (KatG) that activates isoniazid. This investigation suggests a rationale for further work on this promising series of antitubercular agents.