Antibacterial activity of Senegenic acid 28-methyl ester against methicillin-resistant Staphylococcus aureus.

Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant clinical challenge owing to its antibiotic resistance and biofilm-forming ability. In this study, we conducted a screening of natural pentacyclic triterpenoids to identify lead compounds with high antibacterial activity. Senegenic acid 28-methyl ester (4) emerged as a potent antibacterial agent against MRSA and clinically isolated multidrug-resistant strains, with minimum inhibitory concentrations (MICs) of 8-64 μg/mL. We predicted the antibacterial mechanism of compound 4 using network pharmacology and validated by time-kill assays and membrane function tests. The results showed that compound 4 disrupted bacterial membranes and inhibited biofilm formation in a dose-dependent manner, reducing biomass and extracellular DNA levels. In vivo, compound 4 significantly improved survival in murine infection models, while demonstrating low cytotoxicity and minimal hemolytic activity. Furthermore, in-depth research on antibacterial mechanisms found that compound 4 downregulated key biofilm-associated genes (e.g., sarA and atl) in MRSA, which indicated by molecular docking and structural visualization analyses. Untargeted metabolomics revealed that compound 4 treatment induced widespread changes in metabolites and significant enrichment in amino acid, energy, and nucleotide metabolism pathways. Overall, these findings establish compound 4 as a dual-action agent with both anti-biofilm properties and regulate bacterial substance and energy metabolism against MRSA infections.