Differences between the inflorescence, leaf and stem essential oils of wild Mentha pulegium plants from Zakynthos, Greece

The composition of the inflorescence (1), leaf (L) and stem (S) essential oils of wild Mentha pulegium plants from three populations (1-3) on the island of Zakynthos were examined. Pulegone (32.8 S1 to 75.8 %, 13) was the major constituent of all of the oils. The other main constituents were piperitenone (5.1 L3 to 35 %, 12), isomenthone (4.3 %, I2 to 28.6 %, L3) and piperitone (0.5 %, I3 to 5.2 %, L2). In total, C-3-oxygenated p-menthane compounds constituted from 73.0 % (SI) to 96.2 % (I2) of the oils. The piperitenone content of the inflorescence oils was up to 2.4 (Loc 3) times higher than that of the leaf oils. Correspondingly, the isomenthone content of the leaf oils was up to 4.2 (Loc 2) times higher than that of the inflorescence oils. The ratio of the isomenthone:piperitenone content of the oils (n=3) was markedly different for the inflorescence (mean 0.31 +/- SD 0.21), leaf (mean 2.91 +/- SD 2.37) and stem (mean 1.12 +/- SD 0.68) oils. The essential oil yields (mL /100g DW) were for the inflorescences 3.1-5.0 %, leaves 3.1-4.0 %, stems <0.1-0.1% and whole plant (aerial parts) 2.4-3.9 % and are among the highest oil yields reported to date in Greece for M. pulegium.