Study of essential oil composition, menthone reductase activity and antimicrobial activity of Mentha piperita in two stages of growth

Mentha piperita is the important species of genus Mentha and it´s essential oil is desired. In this research amount of essential oil, menthone reductase activity and antibacterial activity of essential oil were investigated in two stage of growth, 2 and 4 months after sowing. The results showed that essential oil composition of M. piperita in two harvests was different. In first harvest, the main constituents of the oil were Menthone, Menthol, Menthofuran, Pulegone, 1,8- Cineole and menthyl acetate respectively whereas the main constituents of the oil in second harvest were Menthol, Menthone, Neo-Menthone, 1,8- Cineole and Menthyl acetate respectively. Menthone reductase activity was significantly greater in the leaves that were harvested 2 months after sowing compared to the 4 months. The results of this research showed that the amount of Menthol was increased accompanying with increase of the enzyme activity. Antibacterial activity of the oil were tested against eleven Gram-(+) or Gram-(-) bacteria. It was found that the oil of first harvest had antibacterial activity against all bacteria and was more active than the essential oil of second harvest.