Essential Oil Compositions and Antibacterial Properties of Mint (Mentha longifolia L.) and Rosemary (Rosmarinus officinalis)

Aims: This study was designed to investigate the chemical composition (gas chromatography/mass spectrometry [GC-MS]) and antibacterial (Gram-positive and Gram-negative bacteria) activities of essential oils extracted from aerial parts of two medicinal plants, Mentha longifolia L. and Rosmarinus officinalis, by MIC and MBC assays.
Place and Duration of Study: Institute of Agriculture, Deputy of Research and Executive, University of Zabol, Zabol, Sistan & Blochestan province, Iran, 2013May to2013 October.
Methodology: The aerial parts of Mentha longifolia L. and Rosmarinus officinalis were collected during their flowering stage. Collected plant samples were air dried in shade and under room temperature conditions. 50 g of dried plants were crushed into smaller pieces, and hydrodistilled in a Clevenger–type apparatus for 3h. The extracted compounds were analyzed on a 6890 N Agilent gas chromatograph coupled with a 5975 C Agilent mass-selective detector. For antibacterial activities assay, Minimal Inhibitory Concentration (MIC) tests against E. coli, Pseudomonas aeruginosa, salmonella typhi, Listeria monocytogenes, Bacillus cereus, Bacillus licheniformis and Staphylococcus aureus were were carried out by using Müller-Hinton broth on a tissue culture test plate. For detection of MBC, culturing was done at Nutrient Agar from wells with no bacterial growth and after 24 hr, incubation was done in 37ºC. The plates without bacterial growth were reported as Minimum Bactericidal concentration (MBC).
Results: 32 components accounting to 94.27% of the total oil were identified in Mint essential oil and 19 components accounting to 97.5% of the total oil were identified in rosemary essential oil. The major components were alpha-Ocimene, 1, 8-Cineole, Borneol, Geraniol and Camphor in rosemary and Pulegone, Isomenthone, beta- Pinene and 1, 8-Cineole in Mint. The essential oil of mint exhibited higher activity rather than L. monocytogenes, Bacillus cereus, Pseudomonas aeruginosa and Staphylococcus ureuse. Both oils had the same effect on E. coli.
Conclusion: The monoterpenes and sesquiterpenes confer the chemical profile of the analyzed essential oil of mint and rosemary samplescausing antibacterial effects.