The Leaf Essential Oils of the New Conifer Genus, Xanthocyparis: Xanthocyparis vietnamensis and X. nootkatensis

Abstract

A new conifer genus was recently discovered in northern Vietnam and named Xanthocyparis with two species: X. vietnamensis in Vietnam and X. nootkatensis (= Chamaecyparis nootkatensis) in western North America. This is the first analysis of the leaf essential oil of X. vietnamensis. The oil of X. vietnamensis is dominated by sesquiterpenes and diterpenes. The major components are hedycaryol (1.4–34.4%), phyllocladene (0.9–37.8%), sandaracopimara-8(14),15-diene (0.7–8.9%), germacrene D (3.7–7.9%), and α-pinene (0.8–14.9%). The oil of Xanthocyparis nootkatensis (Chamaecyparis nootkatensis) is dominated by monoterpenes. The major constituents of X. nootkatensis are limonene (35.4–42.4%), ω-3-carene (11.5–23.4%), α-pinene (8.7–16.3%) and nezukol (3.3–4.8%). The oils differ in many components but share many of the unusual diterpenes. This seems to indicate a rather distant relationship and a long period of divergence. The oil samples of X. vietnamensis were extremely variable (e.g. hedycaryol 1.4–34.4%; phyllocladene 0.9–37.8%) suggesting chemical races or botanical varieties may be present.