Potency of

Rhizophora stylosa leaf extract contains bioactive compounds with potential antibacterial activity, yet its effectiveness across bacterial species and concentration ranges remains insufficiently characterized. This study evaluates the antibacterial performance of ethanol-based extracts at concentrations of 10, 50, 100, 150, and 200 mg/mL against Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Vibrio cholerae, Bacillus cereus ATCC 14579, and Staphylococcus aureus ATCC 25923. Antibacterial activity was assessed using disc diffusion to measure inhibition zones and dilution assays to determine MIC and MBC values. The extract at 50 mg/mL produced the strongest inhibition against V. cholerae (9.14 ± 0.19 mm). MIC-MBC results showed E. coli with a MIC of 25 mg/mL and MBC of 100 mg/mL; B. cereus with MIC ≥1.56 mg/mL and MBC >200 mg/mL; V. cholerae with MIC 3.75 mg/mL and MBC 6.25 mg/mL. The MBC for S. aureus and P. aeruginosa was >200 mg/mL, indicating resistance. These findings demonstrate that ethanol extracts of R. stylosa leaves possess antibacterial activity, particularly against V. cholerae, and may contribute to mitigating antibiotic resistance. This work supports Sustainable Development Goal 3 by exploring natural antibacterial alternatives to enhance global health resilience.