Chemical Composition and Antibacterial Activity of the Essence oil of Peppermint (Mentha piperita L)

Introduction &

Peppermint (Mentha piperita L.) is a perennial herbaceous essence oil bearing plant which belongs to the Lamiaceae family. This plant is a valuable and important herb which has many therapeutic properties. Recent investigations have shown its excellent anti-irritable bowel syndrome effects. Other properties of this plant are anti-inflammatory, analgesic, promote menstrual flow, antipyretic, antiseptic and anti-rheumatoid effects. This investigation was conducted to study the antibacterial properties of peppermint essence oil, as well as determining the content and composition of essential oil.

In order to study the effect of the antibacterial activity of the essence oil of peppermint, this experimental study was conducted in 2009 at Hamedan University of Medical Sciences. The aerial parts of the peppermint were harvested in summer when it was in the full blooming stage of the plant. The collected aerial parts were then dried in the shade. The essence oil of the aerial parts was extracted by hydro-distillation technique using Clevenger apparatus and was analyzed by the capillary GC and GC/MS method. Anti bacterial properties of the essence oil on four pathogenic bacteria were determined by using broth dilution and well diffusion agar methods. The collected data were analyzed by the SPSS version 11.5 software, using the independent t-test.

The essence oil of peppermint showed the maximum anti bacterial effect on E. coli and the minimum effect on S. aureus and P. aeuroginosa. The essence oil content of aerial parts was 0.69% (w/w) based on dry weight. The amount of menthol which is the main constituent of the oil and as an antiseptic component was 47.9%.

Results of this study revealed that the essential oil of peppermint is rich in menthol and can be considered as an anti-bacterial agent in drug and food industries.