In Vitro Antibacterial Activity and Chemical Composition of Essential Oil of Mentha arvensis Linn. Leaves

The essential oil obtained from fresh leaves of Mentha arvensis (Lamiaceae), a perennial aromatic herb grown in Saudi Arabia, was screened for in vitro antibacterial activity and chemical composition. Hydro-distilled essential oil (yield 0.71 %) was analysed for its chemical composition by gas chromatography-flame ionization detector (GC-FID) and gas chromatography-mass spectrometry (GC-MS). The antibacterial activity was tested in vitro on gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis and Streptococcus pyogenes) and gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) using agar disc diffusion assay and minimum inhibitory concentration (MIC) was also determined. The essential oil analysis displayed the presence of 21 constituents which represent 97.51 % relative peak area of the whole chromatogram. The leading components of the oil were monoterpenes (92.52 %) represented by 04 hydrocarbons (5.10 %) and 11 oxygenated derivatives (87.42 %) with menthol (56.35 %), menthone (10.90 %), methyl acetate (7.70 %) and isomenthone (5.20 %) as the major constituents. The pathogens were sensitive to the oil and showed highly effective antibacterial activity with the maximum inhibition zone against S. aureus (22.33 +/- 1.15 mm). The minimum inhibitory concentration (MIC) of the oil was higher against gram-positive bacteria than the gram-negative bacteria. The results indicate that the fresh leaves oil of M. arvensis has high potential as an antibacterial agent for both pharmaceutical and pesticide industries and can also be a promising candidate for flavor and fragrance applications.