Eucalyptus oil is the generic name for distilled oil from the leaf of Eucalyptus , a genus of the plant family Myrtaceae native to Australia and cultivated worldwide. Eucalyptus oil has a history of wide application, as a pharmaceutical, antiseptic, repellent, flavouring, fragrance and industrial uses. The leaves of selected Eucalyptus species are steam distilled to extract eucalyptus oil.
Eucalyptus oils in the trade are categorized into three broad types according to their composition and main end-use: medicinal, perfumery and industrial. [1] The most prevalent is the standard cineole-based "oil of eucalyptus", a colourless mobile liquid (yellow with age) with a penetrating, camphoraceous, woody-sweet scent. [2]
China produces about 75% of the world trade, but most of this is derived from the cineole fractions of camphor laurel rather than being true eucalyptus oil. [3] Significant producers of true eucalyptus include South Africa, Portugal, Spain, Brazil, Australia, Chile, and Eswatini.
Global production is dominated by Eucalyptus globulus . However, 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. Rectification is used to bring lower grade oils up to the high cineole standard required. In 1991, global annual production was estimated at 3,000 tonnes for the medicinal eucalyptus oil with another 1,500 tonnes for the main perfumery oil (produced from Eucalyptus citriodora ). [4] The eucalyptus genus also produces non-cineole oils, including piperitone, phellandrene, citral, methyl cinnamate and geranyl acetate.
Eucalyptus oil is a common ingredient in decongestant formulations. [5] The European Medicines Agency Committee on Herbal Medicinal Products concluded that traditional medicines based on eucalyptus oil can be used for treating cough associated with the common cold, and to relieve symptoms of localized muscle pain. [6]
Cineole-based eucalyptus oil is used as an insect repellent and biopesticide. [7] In the U.S., eucalyptus oil was first registered in 1948 as an insecticide and miticide. [8]
Eucalyptus oil is used in flavouring. Cineole-based eucalyptus oil is used as a flavouring at low levels (0.002%) in various products, including baked goods, confectionery, meat products and beverages. [9] Eucalyptus oil has antimicrobial activity against a broad range of foodborne human pathogens and food spoilage microorganisms. [10] Non-cineole peppermint gum, strawberry gum and lemon ironbark are also used as flavouring. Eucalyptus oil is also used as a fragrance component to impart a fresh and clean aroma in soaps, detergents, lotions, and perfumes. It is known for its pungent, intoxicating scent. Due to its cleansing properties, eucalyptus oil is found in mouthrinses to freshen breath.[ citation needed ]
Research shows that cineole-based eucalyptus oil (5% of mixture) prevents the separation problem with ethanol and petrol fuel blends. Eucalyptus oil also has a respectable octane rating, and can be used as a fuel in its own right. However, production costs are currently too high for the oil to be economically viable as a fuel. [11]
Phellandrene- and piperitone-based eucalyptus oils have been used in mining to separate sulfide minerals via flotation.
Eucalyptus oil is used in household cleaning applications. [12] [13] It is commonly used in commercial laundry products such as wool wash liquid. It is used as a solvent for removing grease and sticky residue. [14]
If consumed internally at low dosage as a flavouring component or in pharmaceutical products at the recommended rate, cineole-based 'oil of eucalyptus' is safe for adults. However, systemic toxicity can result from ingestion or topical application at higher than recommended doses. [15] In Australia, eucalyptus oil is one of the many essential oils that have been increasingly causing cases of poisoning, mostly of children. There were 2,049 reported cases in New South Wales between 2014 and 2018, accounting for 46.4% of essential oil poisoning incidents. [16]
The probable lethal dose of pure eucalyptus oil for an adult is in the range of 0.05 mL to 0.5 mL/per kg of body weight. [17] Because of their high body-surface-area-to-mass ratio, children are more vulnerable to poisons absorbed transdermally. Severe poisoning has occurred in children after ingestion of 4 mL to 5 mL of eucalyptus oil. [18]
Eucalyptus oil has also been shown to be dangerous to domestic cats, causing an unstable gait, excessive drooling, and other symptoms of ill health. [19]
Aboriginal Australians use eucalyptus leaf infusions (which contain eucalyptus oil) as a traditional medicine for treating body pains, sinus congestion, fever, and colds. [20] [21]
Dennis Considen and John White, surgeons on the First Fleet, distilled eucalyptus oil from Eucalyptus piperita found growing on the shores of Port Jackson in 1788 to treat convicts and marines. [22] [23] [24] [25] Eucalyptus oil was subsequently extracted by early colonists, but was not commercially exploited for some time.
Baron Ferdinand von Mueller, Victorian botanist, promoted the qualities of Eucalyptus as a disinfectant in "fever districts", and also encouraged Joseph Bosisto, a Melbourne pharmacist, to investigate the commercial potential of the oil. [26] Bosisto started the commercial eucalyptus oil industry in 1852 near Dandenong, Victoria, Australia, when he set up a distillation plant and extracted the essential oil from the cineole chemotype of Eucalyptus radiata . This resulted in the cineole chemotype becoming the generic 'oil of eucalyptus', and "Bosisto's Eucalyptus Oil" still survives as a brand.
French chemist, F. S. Cloez, identified and ascribed the name eucalyptol — also known as cineole — to the dominant portion of E. globulus oil. [27] By the 1870s oil from Eucalyptus globulus, Tasmanian blue gum, was being exported worldwide and eventually dominated world trade, while other higher quality species were also being distilled to a lesser extent. Surgeons were using eucalyptus oil as an antiseptic during surgery by the 1880s. [28]
Eucalyptus oil became an important industry in the box-ironbark forests of Victoria during the post gold-rush era of the 1870s. The oil was often described as Australia's natural wonder and was exported to a growing international market, mostly for medicinal purposes. Eucalyptus oil was in particularly big demand during the global influenza pandemic of 1918-19. A distillation plant was established by the Forests Commission Victoria at Wellsford State Forest [29] near Bendigo in 1926. The Principal of the Victorian School of Forestry, Edwin James Semmens, undertook much of the pioneering chemistry into the composition of eucalyptus oil. [30] His steam extraction kilns are in the museum at the school.
The Australian eucalyptus oil industry peaked in the 1940s, the main area of production being the central goldfields region of Victoria, particularly Inglewood; then the global establishment of eucalyptus plantations for timber resulted in increased volumes of eucalyptus oil as a plantation by-product. By the 1950s the cost of producing eucalyptus oil in Australia had increased so much that it could not compete against cheaper Spanish and Portuguese oils (closer to European Market therefore less costs). Non-Australian sources now dominate commercial eucalyptus oil supply, although Australia continues to produce high grade oils, mainly from blue mallee (E. polybractea) stands.
Commercial cineole-based eucalyptus oils are produced from several species of Eucalyptus:
Non-cineole oil producing species:
The former lemon eucalyptus species Eucalyptus citriodora is now classified as Corymbia citriodora, which produces a citronellal-based oil.
An essential oil is a concentrated hydrophobic liquid containing volatile chemical compounds from plants. Essential oils are also known as volatile oils, ethereal oils, aetheroleum, or simply as the oil of the plant from which they were extracted, such as oil of clove. An essential oil is essential in the sense that it contains the essence of the plant's fragrance—the characteristic fragrance of the plant from which it is derived. The term "essential" used here does not mean indispensable or usable by the human body, as with the terms essential amino acid or essential fatty acid, which are so called because they are nutritionally required by a living organism.
Camphora officinarum is a species of evergreen tree indigenous to warm temperate to subtropical regions of East Asia, including countries such as China, Taiwan, Vietnam, Korea, and Japan. It is known by various names, most notably the camphor tree, camphorwood or camphor laurel.
Eucalyptus globulus, commonly known as southern blue gum or blue gum, is a species of flowering plant in the family Myrtaceae. It is a tall, evergreen tree endemic to southeastern Australia. This Eucalyptus species has mostly smooth bark, juvenile leaves that are whitish and waxy on the lower surface, glossy green, lance-shaped adult leaves, glaucous, ribbed flower buds arranged singly or in groups of three or seven in leaf axils, white flowers and woody fruit.
Eucalyptol is a monoterpenoid colorless liquid, and a bicyclic ether. It has a fresh camphor-like odor and a spicy, cooling taste. It is insoluble in water, but miscible with organic solvents. Eucalyptol makes up about 70–90% of eucalyptus oil. Eucalyptol forms crystalline adducts with hydrohalic acids, o-cresol, resorcinol, and phosphoric acid. Formation of these adducts is useful for purification.
Backhousia citriodora, commonly known as lemon myrtle, lemon scented myrtle or lemon scented ironwood, is a flowering plant in the family Myrtaceae. It is endemic to subtropical rainforests of central and south-eastern Queensland, Australia, with a natural distribution from Mackay to Brisbane.
Phellandrenes are a pair of organic compounds that have a similar molecular structure and similar chemical properties. α-Phellandrene and β-phellandrene are cyclic monoterpenes and are double-bond isomers. In α-phellandrene, both double bonds are endocyclic and in β-phellandrene, one of them is exocyclic. Both are insoluble in water, but miscible with diethyl ether.
Corymbia citriodora, commonly known as lemon-scented gum and other common names, is a species of tall tree that is endemic to north-eastern Australia. It has smooth white to pink bark, narrow lance-shaped to curved adult leaves, flower buds in groups of three, white flowers and urn-shaped or barrel-shaped fruit.
Eucalyptus olida, commonly known as strawberry gum or sometimes as forest berry, is a species of small to medium-sized tree that is endemic to a restricted area of New South Wales, Australia. It has rough, flaky and fibrous bark on the trunk and larger branches, lance-shaped to curved adult leaves, flower buds in groups of seven to fifteen or more, white flowers and barrel-shaped or bell-shaped fruit.
Eucalyptus staigeriana, commonly known as the lemon-scented ironbark, is a species of small ironbark tree that is endemic to the Cape York Peninsula. It has rough ironbark on the trunk and branches, lance-shaped to egg-shaped leaves that smell of lemons when crushed, flower buds in groups of seven, white flowers and oval to spindle-shaped fruit.
Eucalyptus dives, commonly known as the broad-leaved peppermint or blue peppermint, is a species of tree that is endemic to south-eastern Australia. It has rough, finely fibrous bark on the trunk and larger branches, smooth bark above, lance-shaped or curved adult leaves, flower buds in groups of eleven or more, white flowers and cup-shaped, hemispherical or conical fruit.
Eucalyptus polybractea, commonly known as the blue-leaved mallee or simply blue mallee, is a species of mallee that is endemic to south-eastern Australia. It has rough, fibrous or flaky bark on the lower part of the trunk, smooth greyish or brownish bark above, lance-shaped adult leaves, flower buds in groups of between seven and eleven, white flowers and cup-shaped or barrel-shaped fruit.
Eucalyptus radiata, commonly known as the narrow-leaved peppermint or Forth River peppermint, is a species of tree that is endemic to south-eastern Australia. It has rough, fibrous to flaky bark on the trunk and larger branches, smooth grey bark on the thinner branches, lance-shaped to curved or almost linear leaves, flower buds in groups of eleven to twenty or more, white flowers and cup-shaped, hemispherical or shortened spherical fruit.
Eucalyptus piperita, commonly known as Sydney peppermint and urn-fruited peppermint, is a small to medium forest tree native to New South Wales, Australia.
Eucalyptus elata, commonly known as the river peppermint or river white gum, is a species of medium to tall tree that is endemic to eastern Australia. It has rough, compacted bark on the lower trunk, smooth bark above, lance-shaped to curved adult leaves, green to yellow flower buds arranged in groups of eleven to thirty or more, white flowers and hemispherical or shortened spherical fruit.
Eucalyptus kochii, commonly known as oil mallee, is a species of mallee, sometimes a tree, and is endemic to Western Australia. It has rough, flaky or fibrous bark on the trunk, smooth grey bark above, linear to narrow lance-shaped adult leaves, flower buds in groups of nine to fifteen, white flowers and urn-shaped fruit.
Eucalyptus smithii, commonly known as the gully gum, gully peppermint, blackbutt peppermint, or ironbark peppermint, is a species of medium-sized to tall tree, sometimes a mallee, that is endemic to southeastern Australia. It has rough, compact bark on the trunk, smooth ribbony bark above, narrow lance-shaped adult leaves, flower buds in groups of seven, white flowers and cup-shaped, bell-shaped or hemispherical fruit.
Piperitone is a natural monoterpene ketone which is a component of some essential oils. Both stereoisomers, the D-form and the L-form, are known. The D-form has a peppermint-like aroma and has been isolated from the oils of plants from the genera Cymbopogon, Andropogon, and Mentha. The L-form has been isolated from Sitka spruce.
François Stanislas Cloez was a French chemist, who authored both as "F. S. Cloez" and "S. Cloez", and is known for his pioneering role in analytical chemistry during the 19th century. He was a founder and later president of the Chemistry Society of France.
