Chemical Composition and Enantiomeric Distribution of the Essential oil of <i>Larix occidentalis</i> Nutt

Background/Objective: Larix occidentalis (Pinaceae) is a tree native to the mountains of northwestern United States and southwestern Canada. Indigenous peoples used this tree as part of their traditional medicine to treat various ailments, including coughs, colds, arthritis, and wounds. As part of our interest in essential oils of coniferous tree species and the potential utilization as fragrances, we have obtained the foliar essential oil of L. occidentalis from Idaho, USA, which complements previous reports from Canada. Methods: The foliage from three individual trees growing on Brundage Mountain, Idaho, were collected; the essential oils obtained by hydrodistillation, and the essential oils characterized by gas chromatographic methods, including enantioselective gas chromatography – mass spectrometry. Results: The yellow essential oils were obtained in yields of 1.25-1.77%. The major components in the essential oils were α-pinene (26.5 ± 5.4%), β-pinene (14.9 ± 2.5%), α-terpineol (8.3 ± 1.2%), and δ-3-carene (6.6 ± 2.9%). The (−)-enantiomers were dominant for camphene (84.1 ± 6.6%), β-pinene (97.7 ± 0.4%), β-phellandrene (80.6 ± 3.2%), borneol (86.2 ± 0.9%), and α-terpineol (85.4 ± 4.6%); the (+)-enantiomer was the only enantiomer observed for δ-3-carene. Conclusions: This is the first investigation of L. occidentalis essential oil from Idaho. The major components are consistent with ethnopharmacological uses of the plant. Additional work is needed to more clearly define the essential oil compositions of North American, European, and Asian Larix species.