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.

[edit] Types and production

Eucalyptus oil in the trade are categorized into three broad types according to their composition and main end-use: medicinal, perfumery and industrial. 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.^[1]

China produces about 70% of the world trade, but most of this is derived from camphor oil fractions rather than being true eucalyptus oil.^[2] Significant producers of true eucalyptus oil include South Africa, Portugal, Spain, Brazil, Australia, Chile and Swaziland.

Eucalyptus polybractea or Blue-leaf Mallee, a species yielding high quality eucalyptus oil

Global production is dominated by Eucalyptus globulus. However, Eucalyptus kochii and Eucalyptus polybractea have the highest cineole content, ranging from 80-95%. The British Pharmacopoeia states that the oil must have a minimum cineole content of 70% if it's pharmaceutical grade.^[3] Rectification is used to bring lower grade oils up to the high cineole standard required. Global annual production of eucalyptus oil is estimated at 3,000 tonnes.^[4]

The eucalyptus genus also produces non-cineole oils, including piperitone, phellandrene, citral, methyl cinnamate and geranyl acetate.

Eucalyptus oil should not be confused with the term "eucalyptol", another name for cineole.

[edit] Uses

[edit] Medicinal and antiseptic

The cineole-based oil is used as component in pharmaceutical preparations to relieve the symptoms of influenza and colds, in products like cough sweets, lozenges, ointments and inhalants. Eucalyptus oil has antibacterial effects on pathogenic bacteria in the respiratory tract.^[5] Inhaled eucalyptus oil vapor is a decongestant and treatment for bronchitis.^[6] Cineole controls airway mucus hypersecretion and asthma via anti-inflammatory cytokine inhibition.^[7][8] Eucalyptus oil also stimulates immune system response by affects on the phagocytic ability of human monocyte derived macrophages.^[9]

Eucalyptus oil also has anti-inflammatory and analgesic qualities as a topically applied liniment ingredient.^[10][11]

Eucalyptus oil is also used in personal hygiene products for antimicrobial properties in dental care^[12] and soaps. It can also be applied to wounds to prevent infection.

[edit] Repellent and biopesticide

The cineole based oils can also be used as an insect repellent and biopesticide. Eucalyptus oil has been used as an effective way of killing dust mites according to the Asthma Foundation of Victoria.^[13]

[edit] Flavouring

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.^[14] Eucalyptus oil has antimicrobial activity against a broad range of foodborne human pathogens and food spoilage microorganisms.^[15] Non-cineole peppermint gum, strawberry gum and lemon ironbark are also used as flavouring.

[edit] Fragrance

Eucalyptus oil is also used as a fragrance component to impart a fresh and clean aroma in soaps, detergents, lotions and perfumes.

[edit] Industrial

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 to be economically viable as a fuel.^[16]

Phellandrene and piperitone based eucalyptus oils have been used in mining to separate metallic sulphides via flotation.

[edit] Safety and toxicity

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, in its pure form it is poisonous according to dosage.

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 low body weight, children are more vulnerable to poisons. Severe poisoning has occurred in children after ingestion of 4 mL to 5 mL of eucalyptus oil.^[18][19]

[edit] History

Australian Aboriginals use eucalyptus leaf infusions — whereby eucalyptus oil is a fraction — 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 colonialists, 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 — now more often called 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]

The Australian eucalyptus oil industry peaked in the 1940s; 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. Non-Australian sources now dominate commercial eucalyptus oil supply, although Australia continues to produce high grade oils of mainly blue mallee, E. polybractea.

[edit] Species utilised

Commercial cineole based eucalyptus oils are produced from several species of Eucalyptus:

• Eucalyptus cneorifolia
• Eucalyptus dives
• Eucalyptus dumosa
• Eucalyptus globulus
• Eucalyptus goniocalyx
• Eucalyptus horistes
• Eucalyptus kochii
• Eucalyptus leucoxylon
• Eucalyptus oleosa
• Eucalyptus polybractea
• Eucalyptus radiata
• Eucalyptus sideroxylon
• Eucalyptus smithii
• Eucalyptus tereticornis
• Eucalyptus viridis

Non-cineole oil producing species:

• Eucalyptus dives - phellandrene variant
• Eucalyptus dives - piperitone variant
• Eucalyptus elata - piperitone variant
• Eucalyptus macarthurii - geranyl acetate
• Eucalyptus olida - methyl cinnamate
• Eucalyptus radiata - phellandrene variant
• Eucalyptus staigeriana - citral, limonene

The former lemon eucalyptus species Eucalyptus citriodora is now classified as Corymbia citriodora, which produces a citronellal based oil.

[edit] Compendial status

• British Pharmacopoeia ^[29]

[edit] See also

• Eucalypts, woody plants belonging to three closely related genera: Eucalyptus, Corymbia and Angophora

[edit] References

[edit] Further reading

• Boland, D.J., Brophy, J.J., and A.P.N. House, Eucalyptus Leaf Oils, 1991, ISBN 0-909605-69-6
• FAO Corporate Document Repository, Flavours and fragrances of plant origin

[edit] External links

• Toxicity Eucalyptus oil profile, Chemical Safety Information from Intergovernmental Organizations