Clinal Variation ofMentha pulegiumEssential Oils Along the Climatic Gradient of Greece

The essential oil content and the C-3 oxygenated p-menthane compounds of Mentha pulegium collected from 38 populations scattered all over Greece are presented. The oil content ranged from 1.0–3.8 mL/100 g (d.w.) and the C-3 oxygenated p-menthane compounds constitute in all populations the bulk of the oil (78.6–99.7% of the total oil). The quantitative composition of the different oils varied greatly with most variable compounds being pulegone (ranging from < 0.1–90.7% of the total oil), piperitone (not detected-97.2%), menthone (0.2–53.4%), isomenthone (0.1—45.1%), piperitenone (< 0.1–39.8%) and isopiperitenone (not detected-23.5%). Discriminant analysis revealed that the oil variation forms a cline along Greece. In southern Greece, where the real Mediterranean climate dominates, the total oil content and the amounts of the more reduced products of the C-3 p-menthane biosynthetic pathway, menthone and/or isomenthone and their derivatives, were increased.