Discovered potential of biomass Eucalyptus deglupta blume: In Vitro and In Silico antimicrobial evaluation against Bacillus subtilis and Escherichia coli

This study aimed to evaluate the antibacterial potential of leaf and twig extracts of Eucalyptus deglupta Blume — the only Eucalyptus species endemic to Southeast Asia — against Bacillus subtilis and Escherichia coli through in vitro and in silico approaches, within a sustainable lignocellulosic biomass valorization framework. Twig and leaf samples were extracted sequentially using solvents of increasing polarity (n-hexane, ethyl acetate, methanol, and water) via ultrasound-assisted extraction (UAE). Antimicrobial activities were evaluated by agar well diffusion and broth microdilution methods. Metabolite profiles were characterized by GC-MS (n-hexane and ethyl acetate extracts) and LC-MS (methanol and water extracts). Active compounds were predicted against six key anti-AMR protein targets (TolC, AcrA, AcrB, AcrD, FabI, and FtsZ) selected via bioinformatics protein–protein interaction (PPI) network analysis using molecular docking (AutoDock Vina 1.5.6). The twig methanol extract showed the lowest MIC (0.10 mg/mL against E. coli ) and the highest inhibition zone diameter (IZD = 23.87 mm), exceeding the positive control chloramphenicol. Sesquiterpenoids ((±)-trans-nerolidol, bisabolol, globulol) dominated the nonpolar extracts, while flavones (cypellocarpin B), flavonols (kaempferol-7-O-rhamnoside), and phenolics (gallic acid) characterized the polar extracts. Molecular docking indicated that cypellocarpin B may interact with FabI (ΔG = −10.872 kcal/mol) and AcrB (ΔG = −10.401 kcal/mol), while (±)-trans-nerolidol showed the highest predicted affinity for AcrB (ΔG = −11.960 kcal/mol), suggesting potential multi-target anti-AMR activity. These findings suggest that E. deglupta lignocellulosic biomass, processed through solvent-polarity-based biorefining, yields extracts with promising multi-target anti-AMR potential, supporting the development of sustainable bio-based antimicrobial platforms within a circular bioeconomy framework.