Chemical composition and evaluation of antibacterial and antioxidant activities of the essential oil of Croton urucurana Baillon (Euphorbiaceae) stem bark

The essential oil obtained from the stem bark of Croton urucurana Baillon (Euphorbiaceae) was analysed by GC and GC-MS. 83 compounds were identified and borneol (14.7%), bornyl acetate (5.2%), 1-isopropyl-7-methyl-4-methylene-1,3,4,5,6,8-hexahydro-2H-naphthalen-4a-ol (14.7%), sesquicineole (10.5%) and gamma-gurjunene epoxide (5.4%) were the main components. The EC50 value of the crude essential oil in the DPPH free radical scavenging assay was 3.21 mg mL-1. The fraction of the crude essential oil that presented antioxidant activity was purified by prep-TLC on silica gel. GC and GC-MS analysis revealed that alpha-bisabolol (38.3%), alpha-eudesmol (9.3%) and guaiol (8.2%) were the main components of the antioxidant fraction. The EC50 value measured for the bioactive oil fraction in the DPPH assay was 1.05 mg mL-1. The antimicrobial activity of the crude essential oil was assayed against seven Gram-positive and Gram-negative bacteria and three yeasts. Measured MIC values ranged from 1.25 to 10.00 mg mL-1.