Chemical composition and antibacterial activities of the essential oils from Ocotea zahamenensis Van Der Werff (Lauraceae)

Abstract

The present work aimed to study the composition and antibacterial properties of the essential oils (EO) of Ocotea zahamenensis leaves (LEO), stem (SEO) and root (REO) barks from two harvest periods (March and June). All EOs were extracted by hydrodistillation from fresh plant parts with yields up to 4.5%. They are colourless, clear, with a strong odour, heavy, levogyre, with a low acid index and an ester index up to 14.89. Gas chromatography/flame ionisation detection analysis of these EOs identified 5 to 12 components representing 96.06 to 99.96% of the overall composition. Safrole was by far the most predominant constituent with contents ranging from 77.45% (SEO, June) to 97.05% (REO, March). The antibacterial activity was tested against eight pathogenic bacteria including 4 Gram (-) and 4 Gram (+) using microdilution assays. With Minimum Inhibitory Concentration (MIC) values of less than 1 mg/mL, all EOs showed antibacterial activity which varied according to the strain. There was not much difference between the activities of March and June Eos, and in both cases SEO were slightly more effective than LEO and REO. All EOs had bacteriostatic action on Bacillus cereus and Vibrio fischeri and bactericidal on almost other strains. When administered orally to mice at 0.5 mg/kg body weight, all EOs caused symptoms of intoxication. Their LD50 varied from 1.019 to 2.73 g/kg body weight. These EOs could be a new source of safrole and could be used for various purposes with further toxicological studies.