Assessment of Antibacterial Properties of Methanolic Leaf Extracts and Their Fractions from Beninese Medicinal Plants

The use of plants in disease treatment is an ancient practice that laid the groundwork for modern pharmacology. This study assessed the antibacterial activities of crude extracts and solvent fractions from Flueggea virosa and Newbouldia laevis, two species extensively used in African traditional medicine. Methanolic leaf extracts were fractionated with hexane, dichloromethane, ethyl acetate, and water. Antibacterial screening was performed via agar well diffusion and broth microdilution methods to determine inhibition diameters (ID), minimum inhibitory concentrations (MIC), and minimum bactericidal concentrations (MBC). Toxicity was assessed using Artemia salina larvae. Phytochemical screening revealed the presence of diverse secondary metabolites. Extracts and fractions from F. virosa exhibited stronger antibacterial effects, particularly against Staphylococcus aureus and Enterococcus faecalis, with IDs of 7–15 and 7–13.5 mm, respectively. The methanolic extract (FvM) showed MIC values of 2.5 and 5 mg/mL, while fractions Fv1 and Fv2 recorded MICs of 10 and 2.5 mg/mL, respectively, on the two bacteria. MBC values ranged from 7.5 to 10 mg/mL, indicating good bactericidal potency (P = 1–4). Conversely, N. laevis displayed weak or no inhibition, except for fraction Nl2, which significantly inhibited S. aureus (ID = 13 mm, MIC = 2.5 mg/mL, MBC = 10 mg/mL, P = 4). Neither plant showed antibacterial activity against Escherichia coli. All tested extracts and fractions were non-toxic to A. salina (LC₅₀ > 0.30 mg/mL). The findings presented the significant antibacterial potential of plant, likely linked to synergistic phytocompounds, providing scientific support for its ethnomedicinal application. Further bio-guided fractionation and compound isolation are recommended to identify their active antibacterial constituents.