Antimicrobial Activity of Butea monosperma Lam. Flower Extract against Gram-positive and Gram-negative Bacteria

A BSTRACT Background: Antimicrobial resistance is increasing worldwide, creating an urgent need for new treatments or agents that can support existing antibiotics. Butea monosperma , a traditional medicinal plant, has shown antimicrobial activity in earlier studies, but its effects on biofilms, its postantibiotic effect (PAE), and its interactions with standard antibiotics have not been well defined. Objectives: This study evaluated the antimicrobial and antibiofilm activities of the ethanolic extract of Butea monosperma Lam. flowers (BMFE) against selected Gram-positive and Gram-negative bacteria and explored its mechanisms of action through network pharmacology. Materials and Methods: In this study, we tested the ethanolic flower extract of Butea monosperma against selected Gram-positive and Gram-negative bacteria. Antimicrobial activity was measured using the minimum inhibitory concentration (MIC) assays. Biofilm inhibition was assessed at concentrations from 1/2× to 4× MIC. We also evaluated PAEs and examined whether BMFE works synergistically with cefalexin. Finally, network pharmacology was used to predict molecular targets and pathways linked to BMFE’s bioactive compounds. Results: BMFE exhibited uniform antibacterial activity (MIC 2 mg/mL) against all tested strains. It significantly reduced biofilm biomass in a concentration-dependent manner: Staphylococcus aureus, Bacillus pumilus, Escherichia coli , and Micrococcus luteus at 2×–4× MIC; Staphylococcus epidermidis and Bacillus subtilis primarily at 4× MIC. BMFE produced a measurable PAE (~2 h at 4× MIC), synergized with cefalexin against S. epidermidis (fractional inhibitory concentration index 0.1875). Network pharmacology implicated fatty acid biosynthesis (E. coli) and protein degradation ( B. subtilis ). Conclusion: BMFE demonstrates significant antimicrobial and antibiofilm activity, especially against Gram-positive bacteria.