Species of the Intermountain Western United States: A Chemotaxonomic Investigation Based on Essential Oil Compositions.

is a genus of 98 species, widely distributed in western North America. This work presents a chemometric analysis of the essential oils of seven species of (, var. , , , , , and var. ) from the intermountain western United States (Oregon and Idaho). The essential oils were obtained by hydrodistillation and analyzed by gas chromatographic methods. essential oil can be characterized as limonene-rich, is a species rich in sabinene and α-pinene, and essential oils were rich in myrcene, while var. essential oils were dominated by octyl acetate and decyl acetate, essential oils from western Idaho had high -cymene and 2-methyl-5-(1,2,2-trimethylcyclopentyl)phenol concentrations, while those from Oregon had relatively high β-phellandrene and sedanenolide levels. The essential oils of var. were too variable to confidently assign a chemical type. The major components in the essential oils were β-phellandrene (16.0-45.7%), ()-ligustilide (5.6-47.1%), ()-β-ocimene (3.3-9.9%), and δ-3-carene (0.2-12.6%). The enantiomeric distributions of α-pinene, camphene, sabinene, β-pinene, limonene, and linalool were also utilized to discriminate between the taxa. There are not enough consistent data to properly characterize var. or the Oregon essential oils. Additional research is needed to confidently describe the chemotype(s) of these species.