Exploration of 1,3-di substituted pyrazole conjugates as DNA gyrase inhibitors to combat Staphylococcus aureus and Mycobacterium tuberculosis

The rapid rise of antimicrobial resistance (AMR), particularly among the ESKAP pathogens represents a critical threat to global healthcare, rendering many conventional Antibiotics ineffective. Therefore, the development of new chemical entities that target essential Bacterial enzymes is an urgent need. Among these, DNA gyrase is a "well-validated," target due to its pivotal function in regulating DNA supercoiling. In this work we designed and synthesized 37 new "pyrazole-indole," conjugates and assessed their inhibitory potential against a panel of Bacterial and mycobacterial pathogens. Among the synthesized derivatives, 6b is the most potent compound demonstrating exceptional Antibacterial efficacy with a MIC of 0.125 μg/mL against Staphylococcus aureus and MIC of 0.5 μg/mL against Mycobacterium tuberculosis. A cytotoxicity evaluation on HepG2 cells revealed a high CC₅₀ of 103.6 μg/mL, resulting in a significant selectivity index (SI) of 828.8, which suggests a favorable safety profile. Time-kill kinetics confirmed the bactericidal nature of 6b, while biofilm studies showed an MBIC₅₀ of 0.309 μg/mL, outperforming ciprofloxacin MBIC₅₀ of 0.368 μg/mL. The mechanism was validated by an enzymatic assay, where 6b significantly inhibited DNA gyrase supercoiling at 1 μg/mL, supported by molecular docking studies showing stable active site interactions. Finally, ADMET predictions confirmed that 6b aligns with Lipinski's Rule of Five, exhibiting drug-like properties with no predicted toxicity. These findings suggest that 6b is a potential lead for the further development of novel antimicrobial agents.

Antibacterial agents; Antimicrobial resistance; DNA gyrase inhibitors; Indole; Pyrazole.