Inhibition of Efflux Pump by O-Eugenol and Its Toxicity in Animal Model

Background: Efflux pumps are transmembrane proteins that expel drugs out of a bacterial cell contributing to microorganism drug resistance. Several studies addressing the use of natural products with medicinal properties have intensified given the above. Thus, the aim of the present study was to investigate the antibacterial activity and the O-eugenol potential in resistance reversal by efflux pump inhibition, as well as to evaluate its toxicity in the arthropod model. The broth microdilution method was used to determine the minimum inhibitory concentration (MIC) and the O-eugenol efflux pump inhibition. For the toxicity assays, mortality and locomotor system damage were performed using the fumigation method.

Results: O-eugenol presented a MIC of 1024 g/mL against . The association of this compound with the antibiotic tetracycline demonstrated a synergistic effect ( < 0.0001), this also being observed when the antibiotic was associated with ethidium bromide ( < 0.0001); thus, these results may be attributable to an efflux pump inhibition. The mortality and geotaxis assays revealed the compound is toxic, with an EC of 18 g/mL within 48 hours of exposure.

Conclusions: While we can conclude that the tested product has an efflux pump inhibitory effect, further studies are needed to elucidate its mechanisms of action, in addition to assays using other strains to verify whether the substance has the same inhibitory effect.