Jasmonate compounds are known as new plant hormones that play important roles in the regulation of plant growth and development. Mints have been used and valued as aromatic herbs for thousands of years. Peppermint (Mentha piperita L.) is used for medicinal and food purposes and its essential oil is considered industrially important. Peppermint plants were grown in a greenhouse in pots. At flowering phase, the plants were treated with different concentrations of MeJA (0, 0.1, 0.5 mM) and after 24 h were evaluated for their carotenoid, anthocyanin, phenol, flavonol, flavonoid, H2O2, and proline. Analysis of variance indicated that different concentrations of MeJA caused significant variation in all measured traits except proline. As the latest studies indicated that components such as polyphenols, carotenoids, and flavonoids are natural antioxidants, the results of this experiment showed a significant increase in the antioxidant potential of Mentha piperita treated with 0.1 mM MeJA.

Essential oils are natural compounds, which have extensive applications in perfumery, food and pharmaceutical industries. Nowadays they are also used in preservation of foods and disinfectant production. Considering the undesirable effects of synthetic compounds on the nature and living beings, using natural compounds like essential oils have been noticed recently. Peppermint (Mentha piperita) belongs to Labiateae family and is originated from Mediterranean region. It is widely cultivated in the world. In this research, we studied composition and antifungal effects of Mentha piperita oil on Fusarium oxysporum f. sp. ciceri., Macrophomina phaseolina, and Dreschlera oryzea on the basis of agar dilution method. The test was caried out with factorial experiments based on the random complete block design with triplicates. 1- Essential oil analysis with GS/MS revealed that main compounds of oil include menthol (19.76%), menthan-3-one (19.31%), menthofuran+isomenthone (9.12%), 1, 8-cineole+beta phellandren (8.8%) and menthol acetate (5.63%). 2-Comparison of means by LSD (?=1%) revealed that inhibitory effect of essntial oil varied among different fungi. After 48 hours, results showed no significant difference between the growth of fungi at 800 and 1600 ppm neither did show between water and alcohol controls, but differences between 200 and 400 ppm were significant. The minimum inhibitory concentration (MIC) of A and C was observed in 800 ppm, where as it was 1600 ppm in the case of B. After 72 hours, investigation showed that the MIC for A increased to 1600 ppm, whereas for C it was 800 ppm yet. After 3 days, 1600 ppm treatment completely inhibited the growth of fungi. After 7 days, it was found that 800 and 1600 ppm on C fungy, and 1600 ppm on A fungy were completely inhibitory. 3-Investigations on the fungicide effect of pippermint oil, showed that peppermint oil in these concentrations have no fungicide properties. The results of our studies revealed that the Mentha piperita oil exhibited a significant antifungal activity. Compounds of essential oils depend on climatic condition, spieces and chemiotype.