Objective: The present study evaluates the antibacterial activity (Minimum Inhibitory Concentration- MIC, Minimum Bactericidal Concentration- MBC) and the Fractional Inhibitory Concentration (FIC) of crude extracts and compounds isolated from Miconia rubiginosa against ten clinical bacterial isolates and one standard bacterial strain Expanded-Spectrum β-lactamase (ESBL)-producing enterobacteria. Materials and Methods: The crude extracts were obtained by maceration and the compounds isolated were purified through different chromatography techniques, and then structures were identified for physical methods of organic analysis. The evaluation of the antibacterial activity for the microdiluition in broth technique. Results: The MIC and MBC result for the ethanolic extract was 2.0 mg/mL. For the dichloromethane extract and ursolic acid and oleanolic acid, MIC was >2.0 mg/mL, but no bactericidal activity (MBC) was observed. The FIC values achieved with the combinatioin of the crude extracts with clavulanic acid were not significantly different. Conclusion: The ethanolic extract from Miconia rubiginosa exhibits better antibacterial activity, but the two isolated compounds are not active against the tested bacterial isolates. The combination of the crude extracts with clavulanic acid does not lead to synergism, and there are no statistical differences between the two crude extracts in this sense.
Key words: Antibacterial activity, Beta-lactamase, Miconia rubiginosa, oleanolic acid, ursolic acid
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