Essential Oils of Micromeria dalmatica Benth., a Balkan Endemic Species of Section Pseudomelissa by Regina Karousou* a ), Effie Hanlidou a ), and Diamanto Lazari b ) a ) Laboratory of Systematic Botany and Phytogeography, School of Biology, Aristotle University of Thessaloniki, GR-54124 Thessaloniki (phone: þ 30-2310-998282; fax: þ 30-2310-998295; e-mail: karousou@bio.auth.gr) b ) Department of Pharmacognosy-Pharmacology, School of Pharmacy, Aristotle University of Thessaloniki, GR-54124 Thessaloniki The essential oils of 13 Greek populations of Micromeria dalmatica, a Balkan endemic species and member of the section Pseudomelissa, were examined for the first time. Among the studied populations, two main oil types could be distinguished. Type I was found to be rich in b-pinene, limonene, and germacrene D (accounting for 55.6 – 70.2% of the total oil), and Type II was characterized by the preponderance of p-menthane compounds (accounting for 64.2 – 89.9% of the oil). The latter oil type could be further divided into two subtypes, one comprising oils with predominance of piperitenone and piperitenone oxide and another composed of oils containing high proportions of pulegone, menthone, and isomenthone. The abundance of p-menthane compounds is a common feature of the oils of all members of the section Pseudomelissa studied to date. However, the existence of oils of Type I has not been previously reported for M. dalmatica, neither for other members of the section Pseudomelissa. Introduction. – Micromeria dalmatica Benth. [syn. Clinopodium dalmaticum (Benth.) BrÌuchler & Heubl., Satureja dalmatica ( Benth.) Nyman ] is a Balkan endemic species occurring in Montenegro, Bulgaria, and Greece [1]. It is a member of the old-world section Pseudomelissa Benth., comprising 20 taxa, among which nine are endemic to the Balkan Peninsula and Anatolia [1] [2]. In Greece, M. dalmatica is confined in the northeastern part of the mainland (East Macedonia and Thrace). Several taxa of the section Pseudomelissa are used in the traditional medicine as mint alternatives, due to their prominent mint-like odor [3 – 7]. The potential economic value of the plants attracted the researchers) interest, resulting in several publications on their essential-oil composition. It has been found that, besides the fluctuations in the quantitative composition, in all cases, the essential oils of the examined taxa were characterized by the preponderance of C(3)-oxygenated p-menthane compounds [3 – 5] [8 – 23] . Moreover, it has been proposed that the presence of p-menthane compounds might have a taxonomic significance, since it might allow the distinction of section Pseudomelissa from section Eumicromeria, respectively [18]. Publications regarding M. dalmatica oils are scarce, and only four wild growing populations (three from Montenegro and one from Bulgaria) have been studied to date [16] [18] [20] [23]. Thus, this study presents, for the first time, the chemical profile of 13 Greek M. dalmatica populations, aiming to increase the knowledge of the species) essential-oil diversity. The obtained results were further compared to the published CHEMISTRY & BIODIVERSITY – Vol. 9 (2012) 2775 # 2012 Verlag Helvetica Chimica Acta AG, Zürich