Chemical Composition, Antibacterial and Inhibitory Activity of the Efflux Pump of Essential Oils from Croton piauhiensis Müll.

As the spread of bacterial resistance to clinically available antibiotics has become a global public health problem, the scientific community has intensified its studies in the search for natural compounds and their derivatives to combat bacterial resistance. In this work, a circadian study of the essential oil extracted from the leaves of Croton piauhiensis (EOCP) was carried out. We also sought to evaluate its antibacterial activity, modulatory potential and if it acts as a possible inhibitor of the efflux pump by determining the minimum inhibitory concentration (MIC) and the association of the oil in subinhibitory concentrations with the antibiotic ciprofloxacin and with ethidium bromide (EtBr) against the strain of Staphylococcus aureus K2068 strain. The assays used to obtain the MIC of the EOCP were performed by broth microdilution, while the efflux pump inhibitory test was performed by the MIC modification method. According to the results, the circadian study showed differences in the chemical composition and percentage of oils collected at different times of the day, which can be attributed to environmental conditions. The main components of the EOCP were β-caryophyllene (6 h—21.23%; 12 h—22.86% and 18 h—16.95%), followed by D-Limonene (6 h—13.27% and 18 h—15.95%) and γ-Elemene (12 h)—12.61%). The EOCP collected at 12 h had a better profile in reducing MIC, presenting antibacterial activity for Staphylococcus aureus and Escherichia coli. In the efflux pump test, it was observed that the oil was able to potentiate the action of ethidium bromide against the S. aureus K2068 strain, which can contribute to the prevention or treatment of infectious diseases caused by multidrug-resistant (MDR) strains.