Sarah-Eve Tremblay, M. Sc. A., chimiste
The fir is directly associated to the holidays frenzy. It is decorated with lights, garlands and, of course, a star on top. Often a small village is built at its foot. Its scent gives the house a festive and comforting smell. That is why, in this holiday season, we will discuss its essential oil, or more specifically that of the species found in Canada: balsam fir (Abies balsamea).
The fir is part of the large group of conifers. It is particularly gathered for the production of lumber and paper, but also for production of essential oils, mainly from needles. The essential oil of balsam fir (figure 1) is rich in monoterpenes, more than 95%. The dominant monoterpenes (figure 2) are β-pinene (B), typically around 25-35%, and Δ3-carene (C) at 8-20% (with exceptions, see below). Some oxygenated compounds of this oil are bornyl acetate (F) typically between 5% and 9%, α-terpineol (D) between 0,1% and 1%, piperitone (E) between ∽0,1% and 1,2% and thymol (G) between traces and 0,3%. [1, internal data]. The piperitone is not a compound that is common to all conifers: for example, it is almost completely lacking in black spruce (Picea mariana). Bornyl acetate, on the other hand, is responsible for the refreshing smell of many conifers. The characteristic sesquiterpenes of balsam fir, besides caryophyllene, are longifolene (H) and β-bisabolene (I).
Figure 2. Typical terpenes from A. balsamea oil. See figure 1 for names.
Essential oil of fir can be divided into two different groups (chemotypes). The first chemotype is rich in Δ3-carene (C) and second chemotype only contains a small percentage. Another division has also been noticed for thymol, with a few samples featuring as much as 3%, but most of the fir oils studied contained only a small percentage of this oxygenated compound. However, those containing a high percentage of thymol were observed in balsam fir oils containing both large or small percentage of Δ3-carene .
One can also notice that oils obtained from young shoots of needles, occurring in spring near the bud burst period, feature an increase in the percentage of bornyl acetate from ∽6% to ∽13%, of piperitone from ∽0,1% to ∽1% and of camphene (A) from ∽4% to ∽10%, and a often decrease in the percentage of β-pinene from up to 40% to ∽12%. This modification of percentage is due to the fact that biosynthesis of some terpenes is at rest during other seasons .
 Régimbal, J-M., Collin, G. (1994) Essential Oil Analysis of Balsam Fir Abies balsamea (L.) Mill, J. Essent. Oil Res., 6, 229-238.
 von Rudloff, E., Granat, M. (1982) Seasonal Variation of the Terpenes of the Leaves, Buds, and Twigs of Balsam Fir (Abies balsamea), Can. J. Bot. 60: 2682-2685.