Design, synthesis and in vitro antitubercular evaluation of novel 7-methoxy pyrrolo[1,2-a]quinoline analogues as CYP 121 inhibitors

Abstract

A novel series of pyrrolo[1,2-a]quinoline analogues (4a-n) was designed via a heterocyclic fusion approach for their antitubercular evaluation. The targeted compounds were synthesized by reacting 6-methoxy quinoline with different substituted phenacyl bromides, to get quinolinium ylide intermediates (2a-i), which have further undergone [3+2] cycloaddition with electron-deficient acetylenes to furnish novel 7-methoxy pyrrolo[1,2-a]quinoline derivatives (4a-n). All these newly synthesized intermediate products and final compounds have been characterized by spectroscopic techniques such as 1H NMR, 13C NMR, HRMS, and FT-IR. The intermediate ylides and final pyrrolo[1,2-a]quinoline analogues were evaluated for their antitubercular potential against the Mtb H37Rv strain (ATCC 27294). All the tested compounds exhibited antitubercular activity with the MIC99 in the range of 25–50 µM (10.4–25.7 µg/mL), compared to the standard drug Isoniazid (0.195 µM=0.026 µg/mL). An in silico molecular docking study revealed the strong binding affinity of target compounds with the enzyme Mtb CYP 121. The pharmacokinetic properties and toxicity predictions indicate overall drug-likeness for synthesized compounds. In this study, the compounds 4i, 4j, and 4k displayed considerable anti-TB activity against Mtb H37Rv with MIC99 values of 25 µM (10.43, 10.54, and 11.65 µg/mL respectively). CC50 of the test compounds were determined by cell viability assay using THP-1 macrophages. The compounds having methoxy and halogen substitution at the para position of the benzoyl fragment of designed molecules exhibited the best activity among the series.