Absence of the antibacterial activity of the crude extracts and compounds isolated from M. rubiginosa against extended-spectrum -lactamase producing enterobacteria

Abstract

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 -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.