Enantioselective gas chromatographic analysis of Cupressaceae foliar essential oils: Callitropsis nootkatensis, Calocedrus decurrens, Sequoia sempervirens, and Thuja plicata

Members of the Cupressaceae have historically held importance in traditional medicine as well as sources of essential oils.As part of our interest in medicinal and aromatic plants, we obtained essential oils from the foliage of Callitropsis nootkatensis, Calocedrus decurrens, Sequoia sempervirens, and Thuja plicata growing in the western United States.The essential oils were analyzed by gas chromatography particularly enantioselective gas chromatography to ascertain whether there are trends in the enantiomeric distribution of chiral monoterpenoids in this family.The major components in C. nootkatensis were pinene (33.5%, 16.4%; 81.8% (-)--pinene), (+)--3-carene (28.6-11.0%),and limonene (34.4%, 4.2%; 89.7% (+)-limonene).The major components in C. decurrens were (+)--3carene (28.6-11.0%),limonene (44.4-14.7%,92.4% (+)-limonene, and terpinolene (10.0-5.4%).The major components in S. sempervirens were -pinene (18.8-10.1%,91.6% (-)-pinene), limonene (8.7-6.2%,87.9% (+)-limonene), and germacrene B (8.2-5.4%).(-)--Thujone (65.9%, 62.5%) and (+)--thujone (12.1%, 10.2%) dominated the essential oil of T. plicata.The chemical compositions of the essential oils are comparable to those reported previously.However, this is the first investigation of the enantiomeric distribution of chiral monoterpenoids in C. nootkatensis, C. decurrens, and S. sempervirens.(+)-Sabinene is the major enantiomer in the Cupressaceae, whereas (-)-sabinene is the major enantiomer in Pinus spp.(+)-Limonene is the major enantiomer in the Cupressaceae, while (-)limonene predominates in the Pinaceae.In contrast to members of the Pinaceae (e.g., Abies and Pinus spp.), in which (-)-terpinen-4-ol and (-)--terpineol were dominant, these two monoterpene alcohols showed variable enantiomeric distributions in the Cupressaceae.The enantioselective gas chromatographic analysis of the Cupressaceae adds to our understanding of the phytochemistry of this family.