Chemical Profile of Essential oil of Ocimum gratissimum L. and Evaluation of Antibacterial and Drug Resistance-modifying Activity by Gaseous Contact Method

Introduction: Plant products with antimicrobial potential and ability to modulate the action of drugs have become the target of several studies. Many studies of the species Ocimum gratissimum Lamiaceae have reported biological activities in the essential oil and extracts of various parts of the plant. Objective: Evaluate the antibacterial and resistance-modifying activity of the essential oil of O. gratissimum (OEOg) and its major compound eugenol. Materials and Methods: OEOg was extracted by hydrodistillation, and eugenol was obtained commercially. Multiresistant strains of Escherichia coli and Staphylococos aureus were used to test for drug activity. Antibacterial and resistance-modifying activity of OEOg and eugenol was evaluated by gaseous contact. Results: Chemical analysis of OEOg demonstrated the presence of eugenol and other compounds such as 1,8-cineole and β-selinene as well. In the evaluation of the antibacterial activity, both OEOg and eugenol were unable to form a bacterial growth inhibition zone at any of the concentrations tested. However, the modulation tests with amikacin and erythromycin identified synergism with OEOg and eugenol against E.  coli and S. aureus. Gentamicin combined with OEOg showed antagonism against S. aureus but synergism against E.coli. When gentamicin was combined with eugenol, there was also synergism against S. aureus, whereas no effect was seen against E. coli. Conclusion: Given the results obtained in this study, it is concluded that OEOg and eugenol may eventually represent a new therapeutic tool against antibiotic-resistant bacteria.