Synthesis, characterization and antitubercular studies of some pyrazole based molecules

Abstract

Tuberculosis, caused by bacillus called Mycobacterium tuberculosis, is one of the major diseases and is second largest killer disease after HIV/AIDS. In the last few decades, extensive research is going on globally targeting effective heterocyclic candidates to develop newer entities to combat against these infectious agents. Pyrazole is such a member of the heterocyclic family that constantly draws interest for the development of newer drug moiety due to its wide spectrum of pharmacological applications. In particular, literatures on pyrazole derivatives have shown quite good response in terms of antitubercular and antibacterial property. Owing to this therapeutic nuance of pyrazole and its derivatives, in the current work, it has been contemplated to integrate various potent heterocyclic motifs with the pyrazole skeleton to form a new molecular framework. Accordingly, five different libraries of pyrazole based compounds comprising of 1,2,3-triazole (P1-P24), 1,3,4- oxadiazole (P25-P48), two series of quinoline (P49 -P89) and isoniazid analogs (P90-P107) have been successfully synthesized through multistep organic synthetic protocols. Chemical structures of the prepared molecules were established by various spectroscopic techniques viz. 1H NMR, 13C NMR, ESI-MS and elemental analyses. Additionally, 3-dimensional structures of few target molecules were confirmed by single crystal X-ray diffraction studies. Further, the synthesized title compounds were subjected to preliminary in vitro antitubercular studies against Mycobacterium tuberculosis H37Rv strain and antibacterial screening against three common infectious bacterial strains of Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli. The active antitubercular molecules in each series were identified and tested for their toxicity on the benign non-cancerous cells. The in silico molecular modeling studies of these active derivatives were also carried out.