Backhousia Citriodora (Lemon Myrtle) - Mar 27, 2012

Backhousia citriodora (Lemon Myrtle), often called "more lemon than Lemon", the smell of this essential oil is exquisite, being very similar to Lemongrass, but sweeter, and has some interesting applications in Aromatherapy. Read on and let us enlighten you on this wonderful Australian native.

Botanical name: Backhousia citriodora
Family: Myrtaceae
Plant Part: Foliage and terminal branchlets
Extraction: Steam distillation
Common Names: Lemon Myrtle, Lemon Scented Myrtle and Lemon Ironwood

Description

B. citriodora is an Australian native indigenous to the coastal areas from Cairns to Brisbane. Growing up to 30 metres in height, B. citriodora is a large shrub to medium sized tree. Flowering occurs in early summer in abundance, each flower with four whitish-cream petals. The leaves are lanceolate (where the length of the leaf is about five times the width and the widest part is below the centre, tapering to each end) and grow to 100mm in length (Clarke and Lee 1994, Kerr 2000, Taylor 1996, Webb 2000). A picture of Lemon Myrtle is shown in Figure 1.

History

Baron Ferdinand Von Mueller (1825-1896), the renowned Botanist, first described this plant and named it after James Backhouse, an English Botanist and Quaker Missionary. Lemon Myrtle was first distilled around 1890 by a German doctor who sent it home to be used in the essential oil industry. It is thought that this could of have been the first isolation of citral, and the oil was named citral after the botanical name of the tree.

In the early 1900's, Lemon Myrtle was used as lemon flavouring and fragrance in Australia, but the cheaper and more accessible citral rich essential oils of Lemongrass and Litsea (May Chang) soon became more popular. The leaves of Lemon Myrtle have also been used as a flavouring agent in cooking to flavour poultry and seafood and in herbed vinegar, mayonnaise and vinaigrettes, and can be used instead of Kaffir Lime leaves in recipes of South East Asian origin.

Prior to World War 1, a German firm distilled the oil and exported it back to Germany, this ceased during the war. During World War 2, the lemon scented oil was used to flavour soft drinks due to a Lemon essence shortage.

In the 1950's the Queensland Forestry Service planted small colonies for scientific research and local distillation from bush stands was also carried out. The first commercial plantation was established in 1991 as a result of renewed interest and subsequently ensuring that the endemic stands were no longer under threat of extinction (Kerr 200, Taylor 1996, Webb 2000).

Constituents

Citral (Neral (alpha citral) and Geranial (beta-citral)) comprises 90-98% of the oil. Other minor constituents are myrcene, methylheptenone, linalool, isocitrals and the unusual dehydro-1,8-cineole. The high concentrations of citral found in B. citriodora is uncommon, for instance the concentration of citral in Lemon-Scented Tea Tree (Leptospermum petersonii) is typically 40-60%, while Lemongrasses are between 60 to 90% depending upon type. May Chang (Litsea cubeba) contains around 70% citral and is the most common source of cheap natural citral (obtained by rectification of the oil). The odour of B. citriodora is a lot fresher, greener and livelier than that of many other high citral oils.

Antimicrobial Activity

Ryan et al (2000) have carried out some antimicrobial trials against a range of microorganisms. At the 1:100 dilution level, Lemon Myrtle completely inhibited Clostridium sp and Aspergillus sp and Staphylococcus aureus, Escherichia coli, Salmonella typhimurium, Mycobacterium phlei, and Candida albicans had minimal growth. It was also found that Lemon Myrtle was able to slow down the growth of various microorganisms.

The antimicrobial properties could make Lemon Myrtle useful in helping to treat topical skin infections as well as respiratory infections however, citral can have skin sensitising effects. The IFRA (International Fragrance Association) recommends that citral and oils with high citral levels be quenched with essential oils high in d-limonene such as Lemon, Lime, Grapefruit, Mandarin and Orange. The high citral content makes Lemon Myrtle useful for air purification (Kerr 2000, Ryan et al 2000).

Other Uses

Other potential uses of Lemon Myrtle as cited by Kerr (2000), Katzer (1999), Taylor (1996) and Webb (2000) indicate that B. citriodora is uplifting and also has properties that help to relax.

Safety

Due to the high citral content of the essential oil, there is a risk of sensitisation when applied topically, so always use diluted, and take care with sensitive, diseased or damaged skin. The potential for skin irritation can be reduced if used in conjunction with high d-limonene content essential oils such as Lemon, Mandarin and Sweet Orange. The recommendation by the IFRA is 80% citral quenched with 20% d-limonene for skin applications. This could translate to 4% B. citriodora, 1% Sweet Orange and 95% Essential Base Cream. Avoid contact with the eyes. Avoid using on children under 2 years of age. As with other citral rich oils, do not take orally in cases of glaucoma (Tisserand and Balacs 1995).

One safety precaution when using B. citriodora oil is to ensure that paper and cloth towels (especially natural fibres such as cotton) are saturated with water as soon as possible after coming into contact with large quantities of the oil, for instance when cleaning up a spill or just being sloppy. High citral oils are easily and rapidly oxidized (on fibres with a high surface area) and this reaction can cause the paper or cloth to catch on fire.

References

Clarke I and Lee H (1994): Name that Flower: Melbourne University Pres: Melbourne, Australia

Fergeus J (2000): What will be the next big oil from Australia: Paper presentation: Australian Botanical Products, Melbourne, Australia

Katzer G (1999): Lemon Myrtle: www-ang.kfunigraz.ac.at/~katzer/engl/back_cit.html

Kerr J (2000): Essential Oil Profile - lemon myrtle: Aromotherapy Today: 16: 12-15 (December 2000)

McMurry J (1992): Organic chemistry: Brooks/Cole: Pacific Grove, California, USA

Ryan T, Cavanagh H, Wilkinson J: Antimicrobial activity of Backhousia citriodora oil: simply Essential: 38: 6-8 (December 2000)

Taylor R: Lemon Myrtle the essential oil: CSIRO Rural Research: 172: 18-19 (Spring 1996)

Tisserand R and Balacs T (1995): Essential Oil Safety: Churchill Livingstone: Hong Kong, Melbourne, New York

Webb M (2000): Bush Sense: Griffin Press: Adelaide, Australia 

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