Chemical composition, antibacterial and antibiotic modulatory effect of Croton campestris essential oils

In this study, essential oils from fresh leaves (EOFL) and branches (EOB) from Croton campestris were investigated for their chemical composition and antimicrobial and antibiotic modulatory activities. The essential oils were extracted by hydrodistillation and analyzed by gas chromatographic–mass spectrometry (GC/MS). The major components found were β-cariophylene (17.0%) and biyclogermacrene (16.2%) – EOFL, β-cariophylene (11.3%) and spathulenol (14.7%) – EOB. The antibacterial evaluation was performed using three methods: gaseous contact, MIC and modulatory activity. In the gaseous contact assay, EOB potentialized gentamicin activity (↑56.2%) against the gram-positive Staphylococcus aureus ATCC 12624. The modulatory activity analyzed by the contact direct assay revealed that EOFF increased the activity of all aminoglycosides tested, except gentamicin. EOFF antagonized the antibacterial effect of gentamicin against Escherichia coli ATCC 25922. The results suggest that the essential oils from leaves and branches of C. campestris could be used as a source of natural products with resistance-modifying antibacterial activity.