Chemical Characterization of Three Artemisia tridentata Essential Oils and Multivariate Analyses: A Preliminary Investigation

Background/Objective: Big sagebrush (Artemisia tridentata Nutt., Asteraceae) is a conspicuous shrub growing in arid and semi-arid regions of intermountain western North America, from eastern Washington and Oregon, through Nevada, Idaho, and Utah, into northern Arizona and New Mexico, and east as far as the western Dakotas, and Colorado. At least three subspecies of A. tridentata have been recognized, including A. tridentata subsp. tridentata Nutt. (basin big sagebrush), A. tridentata subsp. wyomingensis Beetle & A.L.Young (Wyoming big sagebrush), and A. tridentata subsp. vaseyana (Rydb.) Beetle (mountain big sagebrush). Although big sagebrush is an important food source and cover for several animal species, the volatile phytochemistry has shown wide variation in composition. The purpose of this work was to compare and contrast the essential oil compositions of the three subspecies of A. tridentata growing in southwestern Idaho. Methods/Results: Several samples of A. tridentata subsp. wyomingensis and A. tridentata subsp. vaseyana were collected, the essential oils obtained by hydrodistillation using a Likens-Nickerson apparatus in yields of 2.33%-4.45% and 0.90%-1.73%, respectively, and the essential oils analyzed by gas chromatographic techniques. Although A. tridentata shows wide variation in essential oil compositions, multivariate analysis (hierarchical cluster analysis and principal component analysis) indicated A. tridentata subsp. tridentata to be characterized by high concentrations of yomogi alcohol (5.8%-30.8%) and camphor (5.2%-20.1%), while camphor was the defining component in A. tridentata subsp. wyomingensis (10.0%-30.1%) and subsp. vaseyana (16.1%-40.2%). One sample of A. tridentata subsp. vaseyana was dominated by alpha-thujone (76.1%), however. Conclusion: There is much variation in essential oil compositions of A. tridentata, both within subspecies and between geographical locations; much additional investigation is necessary to more fully characterize the volatile phytochemistry of this plant.