Essential oil variation of Thymbra spicata L. (Lamiaceae), an East Mediterranean “oregano” herb

This is the first account of the essential oils of wild Greek plants of Thymbra spicata, an East Mediterranean species used as a culinary herb and herbal tea. In particular, the yield and composition of the essential oil of Th. spicata from Chios Island is recorded and compared between two seasons. Considering that Chios provides the westernmost studied material of Th. spicata, the geographical variation in the main essential oil compounds in the total natural range of the species in relation to its systematics is also discussed. The essential oil yield of the Chios plants ranged from 2.4 to 4.8 mL 100 g−1 dry weight (aerial parts without stems). Carvacrol (responsible for the “oregano” scent) was dominant in considerably high amounts (67.5%-88.3% of the total oil) and without significant seasonal differences. Other main compounds were p-cymene (0.7%-17.4%), γ-terpinene (0.1%-6.9%) and caryophyllene oxide (0.9%-2.5%). Τhymol (responsible for the “thyme” scent) was always very low (0.3%-0.7%). Throughout the East Mediterranean, carvacrol is dominantly the major essential oil compound of Th. spicata. p-Cymene, γ-terpinene and other, more minor, compounds contribute to local differences in the species' essential oils in its total range. The thymol-chemotype is scarce throughout the species' range and not related to the local Turkish subspecies intricata as previously suggested. Despite the closer taxonomic affinities with the genus Thymus and the thyme-related vernacular names attributed to Th. spicata, this species can be characterized as an “oregano” with regard to its essential oil composition and herbal use.