Abstract
Introduction: Antimicrobial resistance represents a significant public health problem, driving the search for new therapeutic alternatives. Nanoencapsulation of Cymbopogon winterianus essential oil emerges as a promising strategy to enhance its stability and activity against clinically relevant microorganisms. Objective: To evaluate the antimicrobial activity of free Cymbopogon winterianus essential oil and nanoemulsion using the disk diffusion method and determine the minimum inhibitory concentration against Escherichia coli and Staphylococcus aureus. Method: To determine the lowest concentration capable of inhibiting microbial growth, microdilution was used, and the antibacterial susceptibility test was performed using the disk diffusion method, using multiple concentrations of the MIC. Results: The EO, both free and in citronella nanoemulsion, showed weak antibacterial activity against S. aureus, with an MIC of 2048 μg/mL for the free oil and 62,500 μg/mL for the nanoemulsion, and a moderate activity against E. coli, with an MIC of 512 μg/mL and 31,250 μg/mL for the nanoemulsion. In the susceptibility test, the oil did not show an inhibition halo at any concentration tested. Conclusions: It is concluded that citronella essential oil exhibited limited in vitro antibacterial activity against the evaluated strains, with better efficacy observed in the free form compared with nanoemulsion. The nanoemulsion did not demonstrate enhanced activity, suggesting that factors related to formulation and experimental conditions may have influenced its performance. These findings indicate that, under the tested conditions, incorporation into a nanoemulsion did not potentiate the antimicrobial effect of the essential oil.