Identification of essential oil components of Marrubium thessalum Boiss. & Heldr., growing wild in Greece.

The essential oil of the Greek endemic species Marrubium thessalum Boiss. & Heldr. (Lamiaceae) was obtained by the hydrodistillation of its aerial parts during the flowering stage. The composition of the oil was analysed by GC and GC-MS. Thirty compounds were identified. The oil was devoid of monoterpenes, while sesquiterpenes constituted the major fraction. The main components of the oil were caryophyllene oxide (21.7%), β-caryophyllene (17.6%), germacrene D (15.3%), β-bisabolene (12.6%) and trans-β-farnesene (8.1%).