Lemon Myrtle (Backhousia citriodora): Benefits, Uses, Dosage, and Safety in Herbal Medicine

What is Lemon Myrtle (Backhousia Citriodora)?

Lemon Myrtle, or Backhousia citriodora, is a small evergreen tree native to the rainforests of northeastern Australia, known for its highly aromatic leaves that emit a strong lemon-like scent and are used in traditional Aboriginal medicine and modern herbal remedies.

Botanical Classification and Taxonomy

The scientific name of Lemon Myrtle is Backhousia citriodora. This plant belongs to the family Myrtaceae, order Sapindales, class Eudicots, division Magnoliophyta, and kingdom Plantae. It is commonly known as Lemon Myrtle in Australia and as Lemon Myrtle or Lemon Tree in other regions. The synonyms for this plant include Backhousia citriodora and regional names such as Lemon Myrtle, Lemon Tree, and Citriodora.

The following table shows the full taxonomy of this plant.

Plant Description and Morphology

Lemon Myrtle is a small to medium-sized evergreen shrub that typically grows up to 2-3 meters in height, with a compact, rounded form.

Its leaves are narrow, elongated, and slightly curved, measuring approximately 5-10 centimeters in length, with a leathery texture and a serrated edge. The flowers are small, white to pale yellow, and clustered in dense, spherical inflorescences, emitting a subtle, lemon-like fragrance. The root system is fibrous and shallow, adapting well to rocky or sandy soils.

The plant has a distinctive citrus aroma, with a textured, aromatic bark and leaves that exude a strong, sharp scent when crushed.

Native Habitat and Distribution

Lemon Myrtle is native to the northeastern regions of Australia, specifically the rainforests of Queensland and New South Wales.

It thrives in tropical and subtropical climates, preferring warm, humid environments with well-drained soil. The plant is typically found in shaded, moist areas within native forests, often near water sources. Its natural range extends along the eastern coast of Australia, from northern Queensland down to southern New South Wales.

Lemon Myrtle requires consistent moisture and partial to full shade to flourish in its native habitat.

Plant Parts Used Medicinally

The medicinally used parts of Lemon Myrtle include the leaves, flowers, and bark.

Leaves are the most commonly utilized component, often harvested during the flowering season for their high essential oil content. Flowers are also used, particularly in traditional formulations, for their aromatic and therapeutic properties. The bark, while less frequently used, contains compounds with antimicrobial and anti-inflammatory effects.

These parts are typically dried and ground into powders or distilled into essential oils for medicinal applications.

Phytochemical Composition

Lemon myrtle (Backhousia citriodora) contains a variety of active compounds, primarily responsible for its therapeutic effects.

These include high concentrations of citral, a monoterpene that contributes to its aromatic profile and antimicrobial properties. Secondary metabolites such as flavonoids and phenolic compounds are also present and contribute to its antioxidant and anti-inflammatory activities. Chemical markers like limonene and geraniol are key components that define its unique phytochemical fingerprint.

These compounds work synergistically to provide the plant's medicinal benefits.

Pharmacological Properties

Lemon myrtle (Backhousia citriodora) exhibits a range of pharmacological properties that make it valuable in herbal medicine.

Its therapeutic actions include antimicrobial, anti-inflammatory, and antioxidant effects, which contribute to its use in treating infections and inflammatory conditions. The biological activity of lemon myrtle is largely attributed to its high concentration of citral, a compound known for its broad-spectrum antimicrobial properties. Pharmacodynamically, citral interacts with cellular membranes and enzyme systems to exert its therapeutic effects.

System-level effects of lemon myrtle may include modulation of immune responses and support for digestive health.

Mechanisms of Action

The mechanisms of action of Lemon Myrtle (Backhousia citriodora) involve its bioactive compounds interacting with cellular and biochemical pathways to exert therapeutic effects.

At the cellular level, its essential oils, particularly citral and limonene, modulate membrane permeability and enzyme activity. Biochemical pathways include the inhibition of inflammatory mediators such as COX-2 and 5-LOX, reducing oxidative stress and inflammatory responses. These compounds also target specific systems, such as the gastrointestinal and respiratory tracts, by enhancing mucosal protection and reducing mucus secretion.

The synergistic effects of these mechanisms contribute to its efficacy in herbal medicine.

Therapeutic Uses

Lemon Myrtle (Backhousia citriodora) is valued in herbal medicine for its wide range of therapeutic uses.

It is commonly used to treat digestive issues such as indigestion, bloating, and nausea due to its carminative and anti-inflammatory properties. The plant is also effective in managing skin conditions like eczema and psoriasis because of its antimicrobial and soothing effects. Additionally, it is used to alleviate respiratory problems such as coughs and sore throats due to its expectorant and decongestant qualities.

Lemon Myrtle may also support immune function and help reduce inflammation in the body.

Preparation Methods and Forms

The preparation methods for Lemon Myrtle involve using the plant in various forms, including essential oil, powder, and dried leaves.

Essential oil is commonly extracted through steam distillation and used in aromatherapy or topical applications. The dried leaves can be brewed into teas or infused into oils for medicinal purposes. Powdered Lemon Myrtle is often added to capsules or tablets for standardized dosing.

It can also be used fresh in culinary applications, though this is less common in herbal medicine.

Dosage and Administration

The typical dosage of Lemon Myrtle (Backhousia citriodora) for medicinal use ranges from 500 to 1,500 mg per day, divided into two to three doses, with the exact amount depending on the intended therapeutic effect and individual health status.

Safety, Side Effects, and Contraindications

Lemon Myrtle (Backhousia citriodora) is generally considered safe when used in moderate amounts as a food or herbal supplement, but it may cause mild gastrointestinal discomfort in some individuals, and its safety during pregnancy, breastfeeding, and for children has not been thoroughly established.

Drug Interactions

While Lemon Myrtle (Backhousia citriodora) is generally considered safe when used in moderate amounts, it may interact with certain medications, particularly those affecting the liver or blood clotting, and its essential oils should be used with caution in conjunction with anticoagulants or during pregnancy.

Toxicity and Precautions

Lemon myrtle (Backhousia citriodora) is generally considered safe when used in typical culinary or medicinal doses, but it may cause mild gastrointestinal discomfort in some individuals, and excessive use could lead to liver toxicity, particularly in those with pre-existing liver conditions.

Cultivation and Harvesting

Lemon myrtle (Backhousia citriodora) is typically cultivated in tropical and subtropical regions with well-drained soil and a warm climate, with harvesting of its leaves occurring primarily during the cooler months to ensure optimal essential oil content and flavor profile.

Processing and Extraction

The processing and extraction of Lemon Myrtle (Backhousia citriodora) typically involve harvesting the leaves, drying them to reduce moisture content, and then using methods such as steam distillation or cold pressing to obtain the essential oils, which are rich in citral and other volatile compounds.

Storage and Shelf Life

Lemon Myrtle (Backhousia citriodora) should be stored in an airtight container in a cool, dry, and dark place to maintain its potency and flavor, with a shelf life of up to 12 months when properly preserved.

Scientific Research and Evidence

Scientific research on Lemon Myrtle (Backhousia citriodora) has primarily focused on its antimicrobial, antioxidant, and anti-inflammatory properties, with studies suggesting potential applications in treating infections, reducing oxidative stress, and managing inflammatory conditions.

Traditional and Historical Uses

Lemon Myrtle (Backhousia citriodora) has been traditionally used by Indigenous Australian communities for its medicinal properties, including treating digestive issues, skin conditions, and as a natural antiseptic and antifungal agent.

Regulatory Status

Lemon Myrtle (Backhousia citriodora) is not currently approved as a medicinal herb in the United States or the European Union, but it is recognized and used in Australian and some other countries for its potential therapeutic properties.

Sustainability and Conservation

Lemon Myrtle (Backhousia citriodora) is not currently approved as a medicinal herb in the United States or the European Union, but it is recognized and used in Australian and some other countries for its potential therapeutic properties.