In vitro Antibacterial Activity of Essential Oils of Croton tetradenius Baill. From the Brazilian Caatinga Biome and Its Synergistic Effect With Ciprofloxacin and Meropenem

Abstract

This study aimed to evaluate the antimicrobial activity of essential oils extracted from two genotypes of Croton tetradenius Baill. individually and in combination with antibiotics against Staphylococcus aureus, Escherichia coli and Klebsiella pneumoniae. Camphor (13.95 %) was found to be the most dominant compound in essential oil obtained from C. tetradenius CTE101 followed by p-cymene (13.37 %) and trans-ascaridole (8.07 %), while the C. tetradenius CTE407 essential oil presented p-cymene (17.55 %), trans-ascaridole (14.0 %) and 1,8-cineole (12.12 %) as main compounds. High concentrations of essential oils were necessary to inhibit the bacterial strains evaluated, with MIC values ranging from 2.8 to 5.6 mg/mL. CTE407 showed lower values compared to CTE101. The checkerboard dilution method demonstrated that combinations of essential oils with antibiotics (ciprofloxacin and meropenem) resulted in a synergistic effect, with the exception of the combination of CTE101 with ciprofloxacin against E. coli. These results indicate that the essential oils tested have the potential to be used in combination with traditional antibiotics. When used in combination with essential oils, a lower concentration of antibiotics was required to inhibit the growth of microorganisms tested.

Keywords:

• Antimicrobial activity
• natural products
• monoterpenes
• checkerboard method