Isolation and evaluation of the antibacterial constituents of <i>Synsepalum brevipes</i>

Purpose: To isolate and evaluate the antibacterial constituents of Synsepalum brevipes.Methods: The compounds were isolated using varying chromatographic separation methods. The structures were established using 1D and 2D nuclear magnetic resonance (NMR) spectroscopic methods, mass spectroscopy (MS), and by comparison with existing data. Extracts, fractions, and selected compounds were assessed against six bacterial strains using the broth microdilution method.Results: Chemical constituents isolated were identified as taraxeryl acetate, taraxerol, ursolic acid, oleanolic acid, betulinic acid, lupeol, herannone, spinasterol, spinasterol-3-O-β-D-glucopyranoside, eicosanoic acid, asperphernamate, hyperoside, spinasterone, arganin C, and butyroside B. The crude extracts and fractions were inactive against all the bacterial strains. The three compounds, which include oleanolic acid, ursolic acid, and hyperoside, exhibited moderate inhibitory activity with minimum inhibitory concentration (MIC) ranging from 12.5 to 50 μg/mL against the tested bacteria. Oleanolic acid revealed moderate bactericidal effects on Escherichia coli, and methicillin-resistant Staphylococcus (minimum bactericidal concentration (MBC) = 100 μg/mL, while ursolic acid showed moderatebactericidal effects on methicillin-resistant Staphylococcus aureus (MBC = 50 μg/mL).Conclusion: These results show that two triterpenoids and one phenolic exhibit moderate antibacterial effects against Escherichia coli, methicillin-resistant Staphylococcus, and Staphylococcus aureus.