The antibacterial, antioxidant, and insecticidal activities of essential oils from Thymus vulgaris L., Salvia officinalis L., and Ocimum basilicum L.

Abstract

The essential oils from Thymus vulgaris, Salvia officinalis, and Ocimum basilicum were extracted by hydrodistillation, characterized by gas chromatography/mass spectrometry, and quantified by gas chromatography/flame ionization detector. The principal constituents were thymol, ρ-cymene and carvacrol (T. vulgaris); camphor, β-pinene, and 1,8-cineole (S. officinalis); and (E)-anethole, linalool, and 1,8-cineole (O. basilicum). The essential oil from T. vulgaris was the most effective, forming inhibition halos of 46.16 ± 0.16 and 26.38 ± 0.33 mm, respectively, for Salmonella choleraesuis and Listeria monocytogenes. This essential oil was also more effective against S. choleraesuis, with a minimum inhibitory concentration of 8.85 mg mL⁻¹, and a minimum inhibitory concentration of 17.71 mg mL⁻¹ for L. monocytogenes. No bactericidal activity against S. choleraesuis and L. monocytogenes was observed for the essential oils from S. officinalis, and O. basilicum. Scanning electron micrographs showed that the addition of essential oils left the bacterial cells damaged and deformed. Significant 2,2-diphenyl-1-picrylhydrazyl free radical scavenging capacity and lipid substrate protection were observed in the β-carotene bleaching assay for the essential oil from T. vulgaris, with IC₅₀ of 231.13 ± 0.53 and 15.25 ± 0.38 μg mL⁻¹, respectively. A dose-dependent relationship between antioxidant activity and concentrations was observed in the tests. Toxicities of LC₅₀ = 1.24, 3.51 and 1.19 mg mL⁻¹ against Drosophila suzukii flies, respectively, were observed for the essential oils from T. vulgaris, S. officinalis, and O. basilicum. Results suggest that essential oils can be promising antioxidant agents, insecticides, and inhibitors of pathogenic bacteria.