Association between drugs and herbal products: In vitro enhancement of the antibiotic activity by fractions from leaves of Croton campestris A. (Euphorbiaceae)

IntroductionThe objective of this study was to evaluate the antibacterial activity of methanol (MFEECC) and ethyl acetate (AFEECC) fractions, obtained from the ethanol extract of Croton campestris A. leaves.MethodsAntibacterial and modulating activity (on bacterial resistance) was determined by micro dilution method to identify the MIC (Minimum Inhibitory Concentration), performed in triplicate and statistical significance tested by ANOVA (two-way) with Bonferroni post hoc test (p < 0.001).ResultsIn the antibacterial activity tests the fractions showed a MIC of ≥1024 μg/mL. In regards to modulation of bacterial resistance, MFEECC showed synergism when combined with antibiotic against bacterial strains. In the modulation tests, AFEECC potentiated the effects of amikacin against Staphylococcus aureus and Pseudomonas aeruginosa but had an antagonistic effect against Escherichia coli. AFEECC combined with gentamicin displayed antagonism against S. aureus and E. coli and an antagonistic effect against P. aeruginosa. When AFEECC was combined with Neomycin it resulted in antagonism against P. aeruginosa but did not affect S. aureus and E. coli.ConclusionsThe results indicate that the extracts and fractions obtained from C. campestris leaves could represent an alternative source of natural products capable of modifying and interfering with bacterial resistance to aminoglycosides.