Chemical composition, antibacterial activity, and antibiotic-potentiating effect mediated by the essential oil of the leaves of Croton urticifolius Lam. (Euphorbiaceae)

The Croton genus belongs to the Euphorbiaceae family and groups aromatic species that produce essential oils characterized by presenting a broad pharmacological spectrum, such as anti-inflammatory, antioxidant, antimicrobial, and anticancer activities. In this context, the present study aimed to investigate the chemical composition and evaluate the antibacterial and antibiotic-potentiating activity of the essential oil from Croton urticifolius leaves (EOCU). The EOCU was analyzed by gas chromatography coupled with mass spectrometry (GC-MS) to identify its chemical constituents. The analysis conducted by GC-MS allowed the identification of 18 compounds (95.0 %) and the main constituents were α-pinene (21.70 %), bicyclogermacrene (21.46 %), and (E)-caryophyllene (17.34 %). Regarding antibacterial activity, EOCU exhibited a minimum inhibitory concentration (MIC) value of 512 μg/mL against Escherichia coli. In combination with ciprofloxacin, EOCU potentiated the effect of this antibiotic against multidrug-resistant Staphylococcus aureus. In summary, these results suggest that the synergistic effects observed in the combination of EOCU and ciprofloxacin may represent a promising therapeutic alternative to overcome the resistance of pathogenic bacteria. This study is the first to report the potentiating effect of C. urticifolius essential oil combined with commercial antibiotics.