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 standard dose of Lemon Myrtle (Backhousia citriodora) for general use is typically 200-500 mg per day, depending on the specific condition being addressed.

It is important to use a standardized extract with a concentration of 10-20% limonene to ensure potency and consistency. The herb should be taken 1-2 times daily, preferably with meals to reduce the risk of gastrointestinal discomfort. Treatment duration should not exceed 4-6 weeks unless otherwise directed by a healthcare professional.

Due to its potent properties, it is crucial to follow these guidelines to avoid overuse and potential adverse effects.

Safety, Side Effects, and Contraindications

Lemon myrtle is generally considered safe when used in typical medicinal doses, but it may cause mild side effects such as gastrointestinal discomfort or allergic reactions in some individuals.

Side effects are rare but can include nausea, stomach upset, or skin irritation upon contact. People with known allergies to citrus fruits or related plants should exercise caution, as lemon myrtle contains similar compounds. It is contraindicated for individuals with hypersensitivity to the plant's essential oils or those experiencing severe allergic reactions.

During pregnancy, lemon myrtle should be avoided due to limited safety data and potential risks to fetal development.

Drug Interactions

Lemon myrtle (Backhousia citriodora) may interact with certain pharmaceuticals due to its potential effects on liver enzymes and metabolism.

It is important to consult a healthcare provider before using lemon myrtle if you are taking medications, as it may alter the effectiveness or side effects of drugs. Interactions with supplements such as vitamin C, echinacea, or ginkgo biloba can enhance or diminish their effects. Combining lemon myrtle with other herbal supplements may increase the risk of adverse reactions or reduce the absorption of specific nutrients.

Always discuss potential interactions with a qualified healthcare professional before starting any new supplement regimen.

Toxicity and Precautions

Toxicity and Precautions: Lemon Myrtle is generally considered safe when used in typical culinary or medicinal amounts, but excessive consumption can lead to adverse effects.

The toxic dose for Lemon Myrtle is not well established, but symptoms of poisoning may occur with ingestion of large quantities. Long-term safety data is limited, though moderate use over extended periods has not shown significant harmful effects in most cases. Poisoning risks are low when following recommended dosages, but caution is advised for individuals with sensitive systems or allergies.

Always consult a healthcare professional before using Lemon Myrtle for therapeutic purposes.

Cultivation and Harvesting

Lemon Myrtle (Backhousia citriodora) is typically grown in well-drained, loamy soils with a slightly acidic to neutral pH.

It thrives in full sun to partial shade, though it requires at least 6 hours of direct sunlight daily for optimal growth. Regular watering is necessary, but the plant is drought-tolerant once established, so avoid overwatering to prevent root rot. Propagation is most effectively done through cuttings or seed, with cuttings having a higher success rate and faster growth. The plant reaches maturity in 2 to 3 years, with the best harvest time occurring in late winter to early spring when the leaves are most aromatic.

Harvesting involves carefully plucking the leaves or using pruning shears to cut the stems, ensuring minimal damage to the plant.

Processing and Extraction

Processing and Extraction of Lemon Myrtle involves several key steps to preserve its aromatic compounds and medicinal properties.

The plant material is typically dried to reduce moisture content and prevent microbial growth. Drying is often done in the sun or using low-temperature methods to maintain the essential oils. Extraction methods such as steam distillation are commonly used to capture the volatile components.

The distillation process yields essential oils that are rich in citral, a compound responsible for its distinctive lemon scent and therapeutic effects.

Storage and Shelf Life

The storage and shelf life of Lemon Myrtle (Backhousia citriodora) depend on proper preservation to maintain its potency and flavor.

The shelf life of dried Lemon Myrtle leaves is typically 1 to 2 years when stored correctly. It is light sensitive, so it should be kept in a cool, dark place away from direct sunlight. Moisture control is essential to prevent mold and degradation; store in a sealed container to maintain dryness.

Ideal storage conditions include a temperature range of 15-20°C and low humidity.

Scientific Research and Evidence

Scientific research has increasingly focused on Lemon Myrtle's potential health benefits, particularly its antimicrobial and anti-inflammatory properties.

Clinical trials have explored its efficacy in treating respiratory infections and skin conditions, with some studies showing promising results. In vitro studies have demonstrated its ability to inhibit the growth of various bacteria and fungi, supporting its use in natural remedies. Pharmacological research highlights the presence of active compounds like citral and limonene, which contribute to its therapeutic effects.

These findings provide a foundation for further exploration of Lemon Myrtle in herbal medicine.

Traditional and Historical Uses

Traditional and Historical Uses of Lemon Myrtle (Backhousia citriodora) date back to the indigenous peoples of Australia, who used the plant for its medicinal properties.

The leaves were traditionally chewed to treat toothache and gum disease due to their antimicrobial effects. Lemon Myrtle was also used in rituals and as a ceremonial plant by Aboriginal communities. Its aromatic qualities made it valuable in traditional healing practices for its ability to soothe and purify.

The plant's use in herbal medicine has been documented for centuries, highlighting its long-standing significance in natural healing systems.

Sustainability and Conservation

The sustainability of Lemon Myrtle (Backhousia citriodora) is a critical concern due to its limited natural range and the pressures of wild harvesting.

Wild harvesting has led to significant depletion of natural populations, particularly in regions where the plant is native, such as eastern Australia. Conservation status assessments indicate that the species is under threat, with some populations classified as vulnerable due to habitat loss and overharvesting. Cultivation alternatives are being explored to reduce reliance on wild sources and support sustainable supply.

These efforts include developing commercial growing methods that mimic natural conditions to ensure long-term viability.