Global production of eucalyptus oil is dominated by oil from Eucalyptus globulus, a tall, evergreen tree endemic to southeastern Australia. Eucalyptus globulus was first formally described in 1800 by the French botanist Jacques Labillardière. The species name is from the Latin globulus, a little ball or small sphere, referring to the shape of the fruit. The Tasmanian blue gum was proclaimed as the floral emblem of Tasmania on 27 November 1962. Blue gum is one of the most extensively planted eucalypts. In the trade, eucalyptus oils fall into three broad types according to composition and main end-use: medicinal, perfumery and industrial. The most prevalent type is the standard cineole-based oil.
Eucalyptus oils are complex mixtures of substances, generally containing 20 to 80 compounds, and terpenes and terpenoids are the major components of those obtained from the leaves. Within the same variety, the essential oil composition can vary according to geographical region. Eucalyptol, also called cineole, is a colorless monoterpenoid liquid and a bicyclic ether. It is insoluble in water, but miscible with organic solvents. Its IUPAC name is 1,3,3-trimethyl-2-oxabicyclo[2.2.2]octane. Eucalyptol makes up about 70-90% of eucalyptus oil. In 1870 F. S. Cloez identified the dominant portion of Eucalyptus globulus oil and ascribed the name eucalyptol to it. The oil of Eucalyptus globulus is virtually phellandrene free, a necessary characteristic for internal pharmaceutical use. Eucalyptus kochii and Eucalyptus polybractea have the highest cineole content, ranging from 80 to 95%. The British Pharmacopoeia states that the oil must have a minimum cineole content of 70% if it is pharmaceutical grade. Medicinal oils are designated in terms of 1,8-cineole content. The highest price is associated with an oil called eucalyptol, which contains about 98% 1,8-cineole.
The genus also produces non-cineole oils, including piperitone, phellandrene, citral, methyl cinnamate and geranyl acetate. Corymbia citriodora, the lemon-scented gum, was renamed from Eucalyptus citriodora in 1995 by Ken Hill and Lawrie Johnson. The essential oil of the lemon-scented gum mainly consists of citronellal (80%).
Eucalyptus oil is a common ingredient in decongestant formulations. Eucalyptol is an ingredient in commercial mouthwashes and cough suppressants. As a flavoring, cineole-based eucalyptus oil is added at a level of 0.002% to baked goods, confectionery, meat products and beverages. Eucalyptus oil is used in household cleaning applications. It is used as a solvent for removing grease and sticky residue. Eucalyptol exhibits insecticidal and insect repellent properties. The known primary toxin in eucalyptus oil is eucalyptol. Systemic toxicity can result from ingestion or topical application at higher than recommended doses.
Aboriginal Australians use eucalyptus leaf infusions as a traditional medicine for treating body pains, sinus congestion, fever and colds. In 1788, Dennis Considen and John White, surgeons on the First Fleet, distilled eucalyptus oil from Eucalyptus piperita, growing on the shores of Port Jackson, to treat convicts and marines. By the 1870s oil from Eucalyptus globulus, Tasmanian blue gum, was being exported worldwide and eventually dominated world trade. Surgeons were using eucalyptus oil as an antiseptic during surgery by the 1880s. Eucalyptus oil was in particularly big demand during the global influenza pandemic of 1918-19.
Explore all seven extraits in the Discovery Set.
—
Related: Amyris · Birch · Cascarilla · Cedarwood · Cypress · Desert Sagebrush · Driftwood · Ebanol
