☯ TCM Properties

Category: transforming phlegm

Temperature: cool

Taste: pungent, bitter

Meridians: lung, large intestine, bladder

Functions:

Promotes expectoration, resolves Phlegm-Heat and Dryness, relieves coughing, tonifies Lung Yin and relieves the bronchi; Promotes sweating, expels Wind-Heat, reduces fever, promotes eruptions, opens the sinuses and relieves pain; Clears Damp-Heat, reduces infection and inflammation, stimulates immunity, stops discharge and expels parasites; Promotes tissue repair, reduces inflammation, benefits the skin and repel insects; Supports the pancreas and lowers Blood sugar

Traditional Chinese Uses

An Ye is the leaf of the blue gum Eucalyptus globulus (Folium Eucalypti), a naturalized Myrtaceae tree used in later Chinese materia medica. Pungent, bitter and cool, entering the Lung, Large Intestine and Bladder channels, it releases the exterior and dispels Wind-Heat, clears Heat and resolves toxicity, transforms Phlegm and stops cough, and clears Damp-Heat while killing parasites and relieving itching.

It is used for wind-heat common cold and influenza with fever, cough and asthma with high fever and thick phlegm, and for malarial fevers; internally for Damp-Heat enteritis, diarrhea and dysentery; and topically as a wash for eczema, scabies, tinea, burns and boils. It is typically decocted (about 6-15 g), or the aromatic oil applied externally. Because its actives are volatile, aromatic and heat-sensitive, it should not be over-boiled.

Western Herbalism Properties

Actions:

antimicrobialexpectorant

Botanical Description

An Ye is the leaf of eucalyptus trees, principally Eucalyptus globulus Labill. (Tasmanian blue gum) and Eucalyptus robusta Sm. (swamp mahogany), tall evergreen trees in the Myrtaceae native to Australia and now widely planted in subtropical southern China and elsewhere for timber, windbreaks, and essential oil. Mature trees reach 20-55 m with smooth bark that sheds in long strips revealing pale grey to bluish-white underbark. Juvenile leaves are opposite, sessile, ovate, glaucous-blue; adult leaves are alternate, petiolate, lanceolate to falcate, 10-30 cm long, leathery, dark green, and pendulous, with conspicuous oil glands giving a strongly aromatic camphoraceous-balsamic odour when crushed. Flowers are showy, with numerous creamy-white stamens and a woody capsular fruit. Mature leaves are collected, partly shade-dried, and used whole or shredded.

Active Constituents

1,8-Cineole (eucalyptol)

Monoterpenoid cyclic ether

Concentration: 60-85% of the leaf essential oil (oil yield ~1-3.5% of dried leaf)

The principal bioactive of eucalyptus leaf. A secretolytic/mucolytic and bronchodilating agent that thins airway mucus and eases expectoration. It has well-documented anti-inflammatory activity, inhibiting arachidonic-acid metabolism and cytokine production (LTB4, PGE2, IL-1β, TNF-α), which underlies its steroid-sparing effect in asthma and COPD.

alpha-Pinene

Bicyclic monoterpene

Concentration: Typically 1-10% of the essential oil

Contributes broncho-relaxant and antimicrobial activity and acts as a mild anti-inflammatory. It is also a recognised airway irritant at high concentration.

p-Cymene

Aromatic monoterpene

Concentration: Minor essential-oil component (~1-5%)

Displays analgesic, antioxidant and antimicrobial actions and potentiates the antibacterial effect of the co-occurring oxygenated terpenes.

Limonene

Monocyclic monoterpene

Concentration: Minor essential-oil component (trace-6%)

Adds antioxidant and mild anti-inflammatory activity and contributes to the characteristic aroma.

Euglobals and macrocarpals

Phloroglucinol-monoterpene / sesquiterpene adducts

Concentration: Minor (leaf-specific acylphloroglucinols)

Potent anti-inflammatory and antimicrobial phloroglucinol derivatives characteristic of Eucalyptus; inhibit granuloma formation and bacterial growth in vitro.

Ellagitannins (e.g. eucalbanin, tellimagrandin)

Hydrolysable tannins

Concentration: Variable, several % of dried leaf

Astringent polyphenols with antioxidant and antiviral activity; account for part of the traditional use of the leaf decoction for infections and inflamed mucosa.

Flavonoids (rutin, quercetin, eucalyptin)

Flavonoids / flavonol glycosides

Concentration: Variable

Antioxidant and vascular-protective flavonoids that scavenge free radicals and complement the anti-inflammatory action of the terpene fraction.

⚠ Drug Interactions

Substrates of CYP3A4 / CYP1A2 / CYP2B6

Moderate Evidence: Probable

1,8-Cineole is a demonstrated inducer of hepatic cytochrome P450 enzymes (CYP3A, CYP1A2, CYP2B), shown to accelerate drug oxidation and shorten barbiturate sleeping time in animal models and to induce CYP activity in human hepatocytes. Enzyme induction can lower plasma concentrations of drugs cleared by these pathways.

Clinical note: Regular high-dose or supplemental eucalyptol may reduce exposure to narrow-therapeutic-index CYP substrates; monitor when combined with such medicines.

Oral hypoglycaemic agents / insulin

Moderate Evidence: Theoretical

Eucalyptus leaf extracts lower blood glucose in animal and preliminary studies, so concurrent use with antidiabetic drugs could have an additive blood-glucose-lowering effect.

Clinical note: Monitor blood glucose if eucalyptus leaf preparations are used with diabetes medication.

Dosage

Form	Amount	Frequency	Duration	Population	Notes
decoction	6-15g	Daily	—	—	—

Preparation Methods

Dried-leaf infusion / decoction

Parts: leaf

Dried mature leaves (typical adult dose ~1.5-3 g, or 4-6 g in TCM decoction) are infused in boiling water and taken as a warm tea for cough and phlegm, or used as a gargle. The steam of the hot infusion is also inhaled to relieve congestion.

Steam inhalation of the essential oil

Parts: leaf essential oil

A few drops of eucalyptus oil are added to hot (not boiling) water and the vapour inhaled to loosen mucus and relieve nasal and bronchial congestion. Not for use in infants or young children because of laryngospasm risk.

Diluted topical / gut-soluble oral capsule

Parts: leaf essential oil, 1,8-cineole

The oil is applied diluted in a carrier for chest rubs and joint pain, or taken as standardized enteric-coated cineole capsules (200 mg) in clinical practice. The undiluted essential oil must never be swallowed neat: as little as a few millilitres can cause serious CNS and respiratory toxicity.

Clinical Studies

Anti-inflammatory activity of 1.8-cineol (eucalyptol) in bronchial asthma: a double-blind placebo-controlled trial

Juergens UR, Dethlefsen U, Steinkamp G, Gillissen A, Repges R, Vetter H (2003) Respiratory Medicine Randomized double-blind placebo-controlled trial

Thirty-two patients with steroid-dependent bronchial asthma received 200 mg 1,8-cineole three times daily or placebo for 12 weeks. The cineole group tolerated a significantly greater reduction in oral prednisolone dose (36% vs 7%), demonstrating a steroid-sparing anti-inflammatory effect.

DOI: 10.1053/rmed.2003.1432 Link

Efficacy of cineole in patients suffering from acute bronchitis: a placebo-controlled double-blind trial

Fischer J, Dethlefsen U (2013) Cough Multicentre randomized double-blind placebo-controlled trial

242 patients with acute bronchitis received 200 mg cineole three times daily or placebo for 10 days. The cineole group showed significantly greater improvement in a bronchitis symptom sum-score and in frequency of coughing fits after 4 days.

DOI: 10.1186/1745-9974-9-25 Link

Concomitant therapy with Cineole (Eucalyptole) reduces exacerbations in COPD: a placebo-controlled double-blind trial

Worth H, Schacher C, Dethlefsen U (2009) Respiratory Research Multicentre randomized double-blind placebo-controlled trial

242 patients with stable COPD received 200 mg cineole three times daily or placebo as add-on therapy for 6 months over winter. Concomitant cineole significantly reduced the frequency, severity and duration of exacerbations compared with placebo.

DOI: 10.1186/1465-9921-10-69 Link

Historical Texts

Zhonghua Bencao (Encyclopedia of Chinese Materia Medica)

Modern (1999)

Eucalyptus is not a herb of classical Chinese antiquity; it was introduced to China in the 19th century and its leaf (An Ye / Da Ye An) is recorded in modern Chinese materia medica for cough, phlegm and skin infections.

Traditional Australian Aboriginal and European folk usage

Pre-modern to 19th century

The leaf was long used by Aboriginal Australians for fever and wounds and was adopted into Western herbal practice as an antiseptic and expectorant during the 1800s.

References

European Medicines Agency, Committee on Herbal Medicinal Products (HMPC). Assessment report on Eucalyptus globulus Labill., folium . European Medicines Agency (EMA/HMPC) (2013) [DOI]
Juergens UR. Anti-inflammatory properties of the monoterpene 1.8-cineole: current evidence for co-medication in inflammatory airway diseases . Drug Research (2014) [DOI]
Chinese Pharmacopoeia Commission. Pharmacopoeia of the People's Republic of China (Folium Eucalypti) . China Medical Science Press (2020) [DOI]

An Ye