RESUMO
This study is a pioneer in reporting the antibacterial properties of the species Croton ceanothifolius Baill. The genus Croton belongs to the family Euphorbiaceae composed of numerous species with documented biological activities. However, the pharmacological properties of C. ceanothifolius remain poorly understood. The leaves of this plant were submitted to hydrodistillation for essential oil (CcEO) extraction and the phytochemical characterization of the oil was performed by GC/MS. The minimum inhibitory concentration of the CcEO was determined for the evaluation of antibacterial activity against multiresistant strains of Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. The antibiotic-modulating activity of the oil, in combination with antibiotics, was also evaluated. The combination of the CcEO with penicillin, norfloxacin, and gentamicin presented a synergistic effect. This effect was more significant for the association with antibiotics of the quinolone and aminoglycoside classes against Escherichia coli. The association of oil with gentamicin showed better results with regard to the Gram-positive strain. The association of the oil with norfloxacin against P. aeruginosa also showed synergism, but the association with penicillin did not change the effect of this antibiotic. Thus, it is concluded that C. ceanothifolius essential oil selectively potentiates the action of antibiotics against multiresistant strains.
RESUMO
The present study evaluated the effect of the essential oil of Mikania cordifolia (EOMc) and its major constituent limonene alone or associated with antibacterial drugs against Multidrug Resistant Bacteria (MDR). To evaluate the antibacterial activity, the minimum inhibitory concentrations (MIC) of the oil and limonene against Pseudomonas aeruginosa, Escherichia coli and Staphylococcus aureus were determined. The antibiotic-modulating activity was assessed using subinhibitory concentrations (MIC/8) of these substances in combination with conventional antibacterial drugs. Although no relevant antibacterial activity of the natural products was detected, both substances modulated the action of antibiotics against resistant bacteria. The EOMc demonstrated the best modulating effect against P. aeruginosa, presenting synergistic effects when associated with gentamicin and norfloxacin. In addition, the oil reduced the MIC of norfloxacin against E. coli as well as reduced the MIC of gentamicin against S. aureus. On the other hand, the best effect of limonene was obtained against S. aureus. Thus, it is concluded that the essential oil Mikania cordifolia and the isolated compound limonene do not have clinically significant antibacterial effect, but modulate the action of antibiotics against MDR bacteria.