From rational design to mechanistic validation: A scaffold optimization strategy for antibacterial candidates with synergistic cytoprotective and pathogen-eradicating properties.

The global prevalence of Staphylococcus aureus (S. aureus) in clinical settings represents a critical hazard to global public health security, highlighting the pressing demand for highly effective antibacterial compounds with novel molecular scaffolds and unique action mechanisms. Herein, we describe the first creation and synthesis of a series of piperazine-bridged sulfonamide indole oxime derivatives, aiming to overcome the drug resistance bottleneck of existing antibiotics. Biological evaluation demonstrated that these derivatives exhibited remarkable antibacterial potential against the tested strains. Notably, the propyl-substituted analog 8b displayed remarkable suppression of S. aureus growth, achieving a MIC value of 2 μM, representing a 6.5-fold improvement compared to the positive control norfloxacin (MIC = 13 μM). The hybrid 8b showed a significantly lower tendency to induce bacterial resistance, outperforming the control drug. Druggability assessment revealed that compound 8b possessed excellent biocompatibility with L929 fibroblasts (negligible cytotoxicity) and could specifically upregulate TGF-β secretion at low concentrations to promote fibroblast proliferation, highlighting its potential synergistic value in tissue repair. Molecular docking simulations confirmed that the potent compound 8b could demonstrat stable interactions with the binding sites of DNA hexamer duplexes and hCAII through an extensive network of hydrogen bonds, suggesting a multi-targeting profile. Preliminary mechanistic studies uncovered that oxime 8b exerted antibacterial effects through a dual-action mode: inducing bacterial cell membrane disruption and mediating bacterial genomic DNA cleavage, which impaired genetic material integrity and blocked key replication-transcription pathways. This work offers an essential structural model and experimental foundation for designing next-generation multi-target sulfonamide-indole oxime antibacterial agents.