Essential oils of two Great Basin composites: Chaenactis douglasii and Dieteria canescens from southwestern Idaho

Chaenactis douglasii and Dieteria canescens are two members of the Asteraceae found in western North America and utilized by Native Americans as herbal medicines. The purpose of this investigation was to examine previously unstudied/understudied volatile phytochemistry of members of the Asteraceae from southwestern Idaho as well as to extend our understanding of the properties of Native American aromatic medicinal plants. The essential oils from the fresh aerial parts were obtained by hydrodistillation and analyzed by gas chromatographic methods. The colorless essential oil of C. douglasii was obtained in 0.024% yield, while D. canescens gave a pale-yellow essential oil in 0.418% yield. Tiglic acid (35.9%) dominated the essential oil of C. douglasii, followed by thymol (8.4%), -cadinene (5.0%), and 8-acetoxyelemol (4.7%). There was also a large concentration of an unidentified component (RI = 1998, 8.7%). The major components in D. canescens essential oil were -cadinene (28.3%), epi-cubebol (24.4%), 1-epi-cubenol (10.9%), and cubenol (7.7%). (-)--Pinene, (-)-germacrene D, (+)--cadinene, and (+) -(E)nerolidol were the exclusive enantiomers found in C. douglasii essential oil, while (+)-pinene (75.7%) was the major enantiomer for -pinene. In D. canescens essential oil, the (-)-enantiomers were predominant for -and -pinene (90.3% and 90.4%, respectively), cis-and trans-sabinene hydrate (86.9% and 85.0%, respectively), terpinen-4-ol (66.8%), terpineol (64.8%), and germacrene D (100%), while the (+)-enantiomer was the major for limonene (95.8%) and -cadinene (100%). A perusal of the literature reveals there to be no obvious trends in enantiomeric distributions of terpenoids in the Asteraceae.