ABSTRACT
The aim of this work was to evaluate the chemical composition and antibacterial activity of Croton tetradenius Baill. (CTEO) and C. pulegiodorus Baill. (CPEO) essential oils against Staphylococcus aureus, and their synergism with antibiotics. The essential oils (EOs) were extracted by hydrodistillation and chemically characterized by gas chromatography-mass spectrometry (CG-MS) and gas chromatography with flame ionization detection (CG-FID). The antimicrobial action of the EOs was tested against two standard strains and four clinical isolates of S. aureus using the disk-diffusion agar method and the microdilution assay. The bacterial kinetic growth was also determined. The synergistic effect between EOs and antimicrobials was analyzed by the checkerboard test. CTEO and CPEO yielded 0.47 and 0.37% w/w and the most common components were p-cymene (28.24%), camphor (17.76%) and α-phellandrene (8.98%), and trans-chrysanthenyl acetate (27.05%), α-terpinene (19.21%) and p-cymene (12.27%), respectively. The disk-diffusion test showed that the bacteria are sensitive to the agents tested. The MIC in the presence of the CTEO it was 4000 µg/mL, while for the CPEO it was 8000 µg/mL, except for clinical isolate 4B. The MBC for strains treated with CTEO were 8000 µg/mL, with the exception of isolates 8B and 0 A 4000 µg/mL. For the CPEO, all strains showed a concentration above 8000 µg/mL. The growth curve showed that CTEO and CPEO altered growth kinetics, delaying the lag phase and reducing the log phase. In combination with antibiotics, both essential oils showed synergisms effect with oxacillin and ampicillin, and additive effect with benzylpenicillin. CTEO and CPEO showed antibacterial action against S. aureus strains, showing as a promise natural alternative in clinical therapy.
