SEASONAL VARIATION OF THE ESSENTIAL OIL OF EUROPEAN PENNYROYAL (MENTHA PULEGIUM L.)

Mentha pulegium L. (syn. Pulegium vulgare Miller) is the only representative of the section Pulegium (Miller) DC. in Europe. Although pulegone, the main component of the essential oil, shows highly hepatotoxic effects, the essential oil as well as the herbal drug (= Menthae Pulegii Herba) is still traded.

Investigations in the essential oils obtained from different parts of the plant at six stages of development revealed a high variation of its composition. Terpene hydrocarbons ranged from 0 to 18.5%, their oxygenated derivatives from 78.5 to 98% of the oil. The main representative of the latter proved to be pulegone (7.0 – 85.3%), menthone (2.7 – 32.3%), and neomenthol (0.4 – 35.5%). 30 further components have been identified.

Obviously, the investigated material belonged to the pulegone-type: oils rich in pulegone, with different quantities of menthone and isomenthone, the common source of European Pennyroyal oils. The evaluation of the results concerning the seasonal variation supports a biosynthetic pathway starting with limonene via pulegone to menthone or isomenthone, respectively. The analysis of the glycosidically bound volatiles of M. pulegium L. revealed no significant connection to the essential oil.