Chemosystematic studies in the genus Tsuga. Leaf and twig oil analysis of western hemlock

Abstract

The chemical composition of the volatile oils of the leaves and twigs of western hemlock and the variations caused by transportation and storage, and those found within trees and within populations, were determined. Whereas the leaf oil was found to be well suited for chemosystematic studies, that of the twigs is unsatisfactory. The major components (3–25%) of the leaf oil were β-phellandrene, myrcene, α-pinene, β-pinene, cis-ocimene, limonene, and α-phellandrene and smaller amounts of α-terpineol, methyl thymol, terpinolene, cadinene and muurolene isomers and their corresponding alcohols, terpinene-4-ol, trans-ocimene, camphene, γ-terpinene, bornyl acetate, thymol, and nerolidol were identified. cis-Ocimene (8–14%) appears to be highly characteristic of the species and it, as well as other quantitative differences, may serve as a distinguishing feature with regard to mountain hemlock, eastern hemlock, and other species of the family Pinaceae. Leaf samples from 10 trees give terpene patterns that are representative of a population; no significant differences at different elevations (10–700 m) were recorded. Although the means of the major terpenes from different populations may vary by several percent, consistent differences between coastal and interior populations of British Columbia were not found.