Data Sheet 1_Phytochemical characterization and evaluation of antimicrobial activity of Eugenia sp.: antibacterial, antibiofilm and ampicillin-potentiating activities against resistant Staphylococcus aureus and Staphylococcus epidermidis.pdf

No relevant activity was observed against the Gram-negative bacteria tested. Active extracts and fractions inhibited biofilm formation at 7.81–15.62 μg mL^-1, while mature biofilm eradication was observed mainly against MRSA, with EBH ≥125 μg mL^-1 and DCM ≥62.5 μg mL^-1. Growth kinetics confirmed sustained inhibition by selected fractions.

Checkerboard assays revealed synergistic interactions between ampicillin and E. astringens against MRSA, (fractional inhibitory concentration index (FICI) = 0.24–0.28), and against S. epidermidis (FICI = 0.35–0.36). These findings are relevant because potentiation of ampicillin activity may enhance β-lactam efficacy against resistant Staphylococcus. SYTOX green assays demonstrated that the active samples, especially DCM from E. astringens and FAE from E. mattosii increased bacterial membrane permeability, suggesting membrane disruption as one of the mechanisms underlying their antibacterial activity.

Cytotoxicity assays in RAW 264.7 macrophages demonstrated low toxicity at MIC concentrations. Collectively, the potent anti-staphylococcal activity, inhibition of biofilm formation, synergistic interactions with ampicillin, membrane permeabilization, and low cytotoxicity at MIC concentrations highlight E. astringens as a promising source of antibacterial compounds and antibiotic adjuvants. These findings support further investigation of E. astringens against resistant Gram-positive pathogens.</p>