Variation in the essential oil content and composition of a Finnish oregano collection

Fifteen oregano samples (Origanum vulgare L.) from eleven different locations in southern Finland plus one commercial Greek oregano (Origanum viride ssp. viride) were cultivated in Mikkeli, south-eastern Finland in 2008 and 2009. The plants were harvested at flowering time in August 2009, dried and stored in paper bags. The plant material was submitted to hydrodistillation in a Karlsruher-Stahl apparatus for two hours in order to isolate the oil and determine the oil content. The oil content varied from 0.2 to 0.8% in the Finnish oreganos and was 3.7% in the Greek oregano. The oils were analysed by GC-MS using an unpolar RTX-1 and a polar Stabilwax column (30m x 0.20mm i.d. Restek Corporation, CA, USA). The identification was based on retention indices and comparison with library spectra. Altogether 47 components were identified and the identified constituents represented 64.9–96.9% of the total oil. The dominant constituents were sabinene (up to 17%), γ-terpinene (up to 12%), β-caryophyllene (up to 20%), germacrene-D (up to 17%), caryophyllene oxide (up to 23%) and carvacrol (up to 85%). A cluster analysis of the essential oil compositions classsifed the oils into five groups: 1) β-caryophyllene/germacrene-D, 2) caryophyllene oxide, 3) carvacrol, 4) β-caryophyllene and 5) sabinene/germacrene-D type. Only the Greek oregano was a carvacrol type. Great variations in oregano oils of Mediterranean origin have been reported (1, 2), but not in oregano of Finnish origin.

References: 1. Figueredo, G et al. (2006) Flav Fragr J 21: 134–139.

2. De Martino, L. et al. (2009) Molecules 14: 2735–2746.