Evaluation of antibacterial and toxicological activities of essential oil of Ocimum gratissimum L. and its major constituent eugenol

The present study aimed to comparatively analyze the antibacterial activity, combined with antibiotics, and toxicological activity of the essential oil of O. gratissimum L. and its major compound, eugenol. The phytochemical analysis of the essential oil was performed by gas chromatography coupled with mass spectrometry. The minimum inhibitory concentration and combined antibiotic activity were performed by microdilution. Drosophila melanogaster was the model organism chosen to evaluate the toxicological response of substances. The chromatographic assay showed eugenol as the major compound of the essential oil of O. gratissimum L. The microbiological assays showed that in terms of antibacterial activity, both products showed similar activity, quite significant in Gram-negatives, such as those of strains of Pseudomonas aeruginosa. Similar results were verified in the modulatory activity, allowing the verification that the bioactivity performed by the essential oil of O. gratissimum L. is mainly influenced by its major constituent. Although the EC50 of the compounds varied subtly, the essential oil was less toxic compared to eugenol. The information obtained in the present study demonstrates that the essential oil of O. gratissimum L. is a promising antibacterial agent and better tolerated than its majority compound alone, in the model organism D. melanogaster.