Raal, A., Kanut, M. and Orav, A. 2010. Annual Variation of Yield and Composition of the Essential Oil of Common Juniper (Juniperus communis L.) Branches from Estonia.  Baltic Forestry 16 (1): 50-56.

The yield and composition of the essential oil of common juniper (Juniperus communis L.) branches from Estonia were analyzed. The yields and composition of the oil isolated by hydrodistillation from dried juniper branches, gathered from one single juniper plant every month in 2006 and in 2007 (12 samples), were compared. The oil yields ranged between 0.05 – 0.70%. A total sixty seven compounds were identified, representing over 96% of the total oil yield. The essential oil from Estonian juniper branches showed a high content of ɑ-pinene (40.4 – 62.0%); the other predominant constituents were limonene (4.2 – 10.0%), ɑ-cadinol (1.9 – 6.3%), δ-cadinene (2.1 – 4.8%), ɣ-muurolene and germacrene D (1.6 – 4.4%), ϐ-myrcene (2.6 – 3.1%), ɑ- and ϐ-selinene (0.9 – 3.1%), germacren D-4-ol (0.8 – 3.0%) and ϐ-pinene (1.4 – 2.2%). The yield of essential oil and amounts of mono- and sesquiterpenes depend on the month of collecting the plant material. The best time for harvesting juniper branches seems to be from January to April. The yield and composition of essential oils in branches are rather similar, but did not completely correspond to the standards of European Pharmacopoeia stated to juniper berries.

Key words: Juniperus communis, common juniper, branches, essential oil, ɑ-pinene, harvesting time, European Pharmacopoeia