Abstract
The chemical composition and antibacterial activity of Nepeta nuda (Lamiaceae) essential oil were examined, as well as the association between it and standard antibiotics: tetracycline and streptomycin. The antibacterial activities of 1,8-cineole, the main constituent of N. nuda oil, individually and in combination with standard antibiotics were also determined. The interactions of the essential oil and 1,8-cineole with antibiotics toward five selected strains were evaluated using the microdilution checkerboard assay in combination with chemoinformatics methods. Oxygenated monoterpenes were the most abundant compound class in the oil (57.8%), with 1,8-cineole (46.0%) as the major compound. The essential oil exhibited in vitro antibacterial activity against all tested bacterial strains, but the activities were lower than those of the standard antibiotics. The combinations N. nuda oil-antibiotic and 1,8-cineole-antibiotic produced a predominantly antagonistic interactions. Chemoinformatics survey confirms the antagonistic interactions as a consequence of membrane potential/proton motive force dissipation. These data indicate cytochrome c oxidase as a target for 1.8-cineole toxicity action mechanisms.