Chemosystematic studies of the volatile oils of Juniperus horizontalis, J. scopulorum and J. virginiana

Abstract

The volatile oil from the foliage of individual plants from different populations of Juniperus horizontalis, J. scopulorum and J. virginiana has been analyzed qualitatively and quantitatively. Some analytical problems are discussed and several new constituents have been identified. J. horizontalis can be differentiated from the other two species by the presence of relatively large percentages of cadinane-type sesquiterpenes and less of the elemol-eudesmol type. The ratio of methyl citronellate to citronellol may also have diagnostic value, as may be the virtual absence of aromatic ethers of the safrole-type. The oil of J. scopulorum is virtually devoid of the cadinol type sesquiterpenes but differentiation from that of J. virginiana is difficult. A useful measure of clinal variation within different populations of each species is the ratio of sabinene and limonene percentages. The occurrence of aromatic ethers in J. scopulorum and J. virginiana is erratic; in J. horizontalis they are present in trace amounts only. Provided an adequate foliage sample size is taken during the dormant season, population studies based on the means of the percentages of the foliage oil components are feasible. Two hybrid swarms of J. horizontalis and J. scopulorum were sampled and all plants had intermediate foliage oil compositions.