Antibacterial activity chemical composition relationship of the essential oils from cultivated plants from Serbia

Abstract

The antibacterial effects of essential oils from Serbian cultivated plants, Thymus vulgaris L. (Lamiace) and Lavandula angustifolia L. (Lamiace) on different bacteria were investigated, with an emphasis on an antibacterial activity-chemical composition relationship. Essential oil was obtained from airdried aerial parts of the plants by hydrodistillation for 3 h using a Clevenger-type apparatus. The essential oil analyses were performed simultaneously by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) systems. The main constituents of thyme oil were thymol (59.95%) and p-cymene (18.34%). Linalyl acetate (38.23%) and linalool (35.01%) were main compounds in lavender oil. The antibacterial activity of the essential oils samples was tested towards 5 different bacteria: laboratory control strain obtained from the American Type Culture Collection and clinical isolates from different pathogenic media. Gram-negative bacteria were represented by Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 43895 and Salmonella enteretidis ATCC 9027 while researched Gram-positive strains were Bacillus cereus ATCC 8739 and Staphylococcus aureus ATCC 25923. A broth microdilution method was used to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Essential oils from thyme have been found to have antimicrobial activity against all microorganisms tested, with a range of MIC values from 0.025 to 0.10 μl/ml and MBC values from 0.05 to 0.78 μl/ml. Lavender oils demonstrated MIC values from 0.025 to 0.20 μl/ml and MBC values from 0.05 and 0.78 μl/ml. Reference antibiotic tetracycline was active in concentrations between 0.025 and 0.05 μl/ml. The Gram- -positive bacteria were more sensitive to the essential oil of thyme, while Gram- -negative bacteria were more sensitive to the essential oil of lavender. Essential oils from thyme and lavender may be used at low concentrations for prevention and treatment of infective diseases in animals and humans caused by pathogenic bacterial species.