N-sulfonylated indole hydrazone hybrid targeting Staphylococcus aureus with compelling antibiofilm and membrane-disrupting properties.

Staphylococcus aureus is a highly adaptable opportunistic pathogen and a leading cause of infectious disease-related morbidity and mortality globally. This pathogen triggers a wide spectrum of infections, from mild skin infections to life-threatening conditions like sepsis and pneumonia. Thus, it is implicated in escalating the global antimicrobial resistance (AMR) crisis, and there is an urgent need for novel antistaphylococcal scaffolds. In response to this challenge, we previously reported a metal-free electrochemical strategy for regioselective synthesis of N-sulfonylated indole-based hydrazone derivatives, identifying compound 5d as a potent lead with an MIC of 6.87 µM against the S. aureus pathogen. Building upon this, our current study provides a comprehensive antibacterial and mechanistic evaluation of the 5d molecule against the S. aureus pathogen. The antibacterial susceptibility analyses, including time-kill kinetics and anti-biofilm assays, demonstrated significant inhibitory effects. Further, mechanistic investigations revealed that potent hit (5d) triggers a multi-targeted bactericidal action. It compromised bacterial membrane integrity, resulting in leakage of cell contents, increased membrane permeability, and heightened oxidative stress through ROS generation. Next, the ATP quantification study revealed that the compound interferes with bacterial cellular bioenergetics by depleting the intracellular ATP levels. These findings highlight the compound 5d as a promising scaffold against S. aureus infections and successfully establish the sulfonylated-indole hydrazones as capable pharmacophores for next-generational antibacterial drug discovery efforts to mitigate the global AMR burden.