Antibacterial evaluation of sophoraflavanone G from Sophora pachycarpa against Pseudomonas aeruginosa and Staphylococcus epidermidis biofilm

Abstract Antimicrobial resistance, particularly among biofilm-forming pathogens, poses a serious threat to public health and drives the urgent need for new therapeutic agents. Sophoraflavanone G, a prenylated flavonoid derived from Sophora pachycarpa , has shown notable antimicrobial activity, especially against Gram-positive bacteria. In this study, Sophoraflavanone G was isolated and purified using chromatographic techniques and structurally confirmed via ¹H-NMR. Its antibacterial and anti-biofilm properties were evaluated against several bacterial strains, including Pseudomonas aeruginosa PAO1 and Staphylococcus epidermidis DSMZ 3270. The compound exhibited potent inhibitory and bactericidal activity against all tested Gram-positive bacteria, with Listeria monocytogenes being the most sensitive (MIC = 0.98 µg/mL). However, it showed no activity against P. aeruginosa in planktonic form (MIC > 1000 µg/mL). While it failed to inhibit P. aeruginosa biofilm formation or enhance tobramycin penetration at low doses, a higher concentration (1 mg/mL) of Sophoraflavanone G significantly improved antibiotic penetration into the biofilm. In contrast, the compound demonstrated strong inhibitory, disruptive, and biofilm-penetrating effects against S. epidermidis , with a clear dose-dependent response. These findings underscore the potential of Sophoraflavanone G as a candidate for managing Gram-positive and biofilm-associated infections, particularly those involving S. epidermidis , while highlighting the need for further development to improve its efficacy against Gram-negative pathogens.