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WHO Monographs on Selected Medicinal Plants - Volume 2
(2004; 358 pages) View the PDF document
Table of Contents
View the documentIntroduction
View the documentGeneral technical notices
View the documentRadix Althaeae
View the documentHerba Andrographidis
View the documentRadix Angelicae Sinensis
View the documentFlos Calendulae
View the documentFlos Caryophylli
View the documentRhizoma Cimicifugae Racemosae
View the documentFolium cum Flore Crataegi
View the documentRadix Eleutherococci
View the documentAetheroleum Eucalypti
View the documentFolium Eucalypti
View the documentCortex Frangulae
View the documentFolium et Cortex Hamamelidis
View the documentSemen Hippocastani
View the documentHerba Hyperici
View the documentAetheroleum Melaleucae Alternifoliae
View the documentFolium Melissae
View the documentAetheroleum Menthae Piperitae
View the documentFolium Menthae Piperitae
View the documentFolium Ocimi Sancti
View the documentOleum Oenotherae Biennis
View the documentRhizoma Piperis Methystici
View the documentCortex Pruni Africanae
View the documentCortex Rhamni Purshianae
View the documentFlos Sambuci
View the documentRadix Senegae
View the documentFructus Serenoae Repentis
View the documentFructus Silybi Mariae
View the documentHerba Tanaceti Parthenii
View the documentRadix Urticae
View the documentFolium Uvae Ursi
View the documentAnnex: Participants in the Second WHO Consultation on Selected Medicinal Plants
 

Aetheroleum Melaleucae Alternifoliae

Definition

Aetheroleum Melaleucae Alternifoliae is the essential oil obtained by steam distillation of the leaves and terminal branchlets of Melaleuca alternifolia (Maiden and Betche) Cheel (Myrtaceae) (1-3).

Synonyms

No information available.

Selected vernacular names

Australian tea tree, tea tree (1-5).

Geographical distribution

Indigenous to Australia, where it is grown commercially (6, 7).

Description

A narrow-leaved tree not exceeding 6 m. Entire plant glabrous; leaves alternate. Flowers scattered in an interrupted spike; stamens more than 12mm long united at their bases to form 5 distinct bundles; capsule persisting within fruiting hypanthium (6-8).

Plant material of interest: essential oil

General appearance

A colourless to pale-yellow liquid (1-3).

Organoleptic properties

Odour: myristic (1, 2).

Microscopic characteristics

Not applicable.

Powdered plant material

Not applicable.

General identity tests

Physico-chemical properties, thin-layer and gas chromatography (1, 2).

Purity tests

Microbiological

Tests for specific microorganisms and microbial contamination limits are as described in the WHO guidelines on quality control methods for medicinal plants (9).

Chemical

Refractive index: 1.475-1.482 (1-3);
Optical rotation: +5° to +15° (1-3);
Relative density: 0.885-0.906 (1-3);
Solubility in alcohol: soluble in two volumes of 85% ethanol at 20°C (1-3).

Pesticide residues

The recommended maximum limit of aldrin and dieldrin is not more than 0.05mg/kg (10). For other pesticides, see the European pharmacopoeia (10), and the WHO guidelines on quality control methods for medicinal plants (9) and pesticide residues (11).

Heavy metals

For maximum limits and analysis of heavy metals, consult the WHO guidelines on quality control methods for medicinal plants (9).

Radioactive residues

Where applicable, consult the WHO guidelines on quality control methods for medicinal plants (9) for the analysis of radioactive isotopes.

Chemical assays

Contains not less than 30% (w/w) of terpinen-4-ol (4-terpineol) and not more than 15% (w/w) of 1,8-cineole (also known as cineol, cineole or eucalyptol) (1, 2). The oil must contain: not less than 3.5% sabine; 1-6% α-terpinene; 10-28% γ-terpinene; 0.5-12.0% p-cymene; not less than 30% terpinen-4-ol; and 1.5-8.0% α-terpineol, as measured by gas chromatography (1-3).

Major chemical constituents

The major constituents are terpinen-4-ol (29-45%), γ-terpinene (10-28%), α-terpinene (2.7-13.0%) and 1,8-cineole (4.5-16.5%) (8, 12-15). Other mono-terpenes present in significant quantities (1-5%) include α-pinene, limonene, p-cymene and terpinolene. The structures of the major monoterpenes are presented below.


1,8-cineole (eucalyptol)


α-terpinene


γ-terpinene


and enantiomer terpinen-4-ol (4-terpineol)

Medicinal uses

Uses supported by clinical data

Topical application for symptomatic treatment of common skin disorders such as acne, tinea pedis, bromidrosis, furunculosis, and mycotic onychia (onychomycosis), and of vaginitis due to Trichomonas vaginalis or Candida albicans, cystitis and cervicitis (16-23).

Uses described in pharmacopoeias and in traditional systems of medicine

As an antiseptic and disinfectant for the treatment of wounds (5).

Uses described in folk medicine, not supported by experimental or clinical data

Symptomatic treatment of burns, colitis, coughs and colds, gingivitis, impetigo, nasopharyngitis, psoriasis, sinus congestion, stomatitis and tonsillitis (24, 25).

Pharmacology

Experimental pharmacology

Antimicrobial activity

Aetheroleum Melaleucae Alternifoliae inhibited the growth in vitro of Escherichia coli, vancomycin-resistant Enterococcus faecium, Staphylococcus aureus, metacillin-resistant Staphylococcus aureus, and a variety of Streptomyces species (MIC 0.04-0.50%) (26-30). It also inhibited the growth in vitro of Trichophyton mentagrophytes, Trichophyton rubrum, Microsporum canis, Malassezia furfur, Candida albicans, Cryptococcus neoformans, Pityrospermum ovale and Trichosporon cutaneum (MIC 1.1-2.2mg/ml) (31-35). The susceptibility of 32 strains of Propionibacterium acnes to the essential oil was determined using a broth dilution method. The MIC was 0.25% for five strains, and 0.50% for the other strains (36). Several chemical constituents of the oil, linalool, terpinen-4-ol, α-terpineol, α-terpinene, terpinolene and 1,8-cineole, inhibited the growth in vitro of a wide variety of microorganisms, including Candida albicans, Escherichia coli and Staphylococcus aureus (MIC 0.06-0.50% v/v) (27).

Toxicology

The dermal median lethal dose (LD50) of the essential oil in rabbits is >5.0mg/kg body weight, since 5.0mg/kg resulted in the deaths of two out of 10 treated rabbits (37). The oral LD50 in rats is 1.9g/kg body weight (range of doses 1.4-2.7 g/kg) (24, 25, 37, 38). The signs of severe toxicity are respiratory distress, and coma with diarrhoea (26, 38). A few cases of toxicosis after topical application of high doses of the essential oil to dogs and cats have been reported. Symptoms included central nervous system depression, weakness, and lack of coordination and muscle tremors that were resolved within 2-3 days after supportive treatment (39).

Clinical pharmacology

Vaginitis and cervicitis

A study without controls assessed the safety and efficacy of a 40% emulsified solution of Aetheroleum Melaleucae Alternifoliae in 13% isopropyl alcohol in the treatment of 130 women with cervicitis or vaginitis due to Trichomonas vaginalis or vaginitis due to Candida albicans. Intravaginal application of tampons saturated with a 20% emulsified solution healed cervicitis due to Trichomonas vaginalis after four weekly treatments. In patients with vaginitis due to Trichomonas vaginalis, intravaginal application of a 1% emulsified solution using a saturated tampon, as well as vaginal douching, resulted in clinical cures and restoration of the cervix (21). In another study without controls, 28 women with vaginitis due to Candida albicans were treated with vaginal pessaries (containing 0.2 g essential oil) every night for 90 days. After 30 days of treatment, 24 patients were already free of symptoms such as leukorrhoea and burning sensation, and 21 were free of Candida albicans (17).

Cystitis

A randomized, double-blind, placebo-controlled trial assessed the efficacy of the essential oil in the treatment of 26 women with chronic ideopathic colibacilli cystitis. Patients were treated with 8 mg essential oil, in an enteric capsule form, orally three times daily for 6 months. After treatment, 54% of the essential oil-treated group were free of symptoms, compared with only 15% in the placebo group. However, approximately 50% of the asymptomatic patients still showed evidence of colibacilli and leukocytes in their urine (17).

Acne

A randomized, single-blind, comparison trial evaluated the safety and efficacy of topical application of a gel containing either 5% essential oil or 5% benzoyl peroxide in the treatment of mild to moderate acne in 119 patients. The results demonstrated that both preparations significantly reduced the number of inflamed and non-inflamed lesions (open and closed comedones) after 3 months of daily treatment (P < 0.001), although the onset of action of the gel containing the essential oil was slower than that of the gel containing benzoyl peroxide. Patients treated with the oil-containing gel reported fewer side-effects than those treated with the benzoyl peroxide-containing gel (16).

Foot problems

A randomized double-blind, placebo-controlled clinical trial evaluated the efficacy of a cream containing either 10% (w/w) essential oil, 1% tolnaftate or a placebo in the treatment of 104 patients with tinea pedis due to Trichophyton rubrum, T. mentagrophytes and Epidermophyton floccosum. After application of the cream twice daily for 4 weeks, 30% of the essential oil-treated patients, 85% of the tolnaftate-treated patients and 21% of the placebo-treated patients showed conversion to a negative culture (P < 0.001). Both the essential oiltreated group and tolnaftate-treated group demonstrated significant improvement in the clinical symptoms of scaling, inflammation, itching and burning sensation, compared with the placebo group (P < 0.001). The cream containing the essential oil reduced symptomatology of tinea pedis as effectively as that containing tolnaftate, but was no better than the placebo in achieving a mycological cure (22). A study without controls assessed the efficacy of three products in the treatment of 60 patients with tinea pedis due to Trichophyton rubrum, T. mentagrophytes and Epidermophyton floccosum, as well as other conditions such as bromidrosis, inflamed corns, calluses, bunions, fissures and mycotic onychia (onychomycosis) of the toenails. Eight patients were treated with 100% essential oil, 40 patients were treated with a 40% emulsified solution of the essential oil in 13% isopropyl alcohol and 12 were treated with an ointment containing 8% essential oil, twice daily for 3 weeks to 4 years. The 100% essential oil was assessed as fair to poor in the treatment of mycotic onychia. The 40% emulsified solution reduced the symptoms of bromidrosis, and inflammation of corns, calluses and bunions. The 8% ointment was effective in the symptomatic treatment of tinea pedis due to T. mentagrophytes and Epidermophyton floccosum, but was less effective against T. rubrum (23).

A randomized, double-blind, multicentre comparison trial assessed the efficacy of 100% essential oil or 1% clotrimazole in the treatment of 117 patients with distal subungual mycotic onychia. Patients received twice-daily applications for 6 months, and debridement and clinical assessment were performed at 0, 1, 3 and 6 months. After 3 months, approximately 50% of each group reported improvements. After 6 months, clinical assessment showed partial or full resolution in approximately 60% of each group (19).

The efficacy of the essential oil was assessed in an open study of 35 patients with furuncles on the axilla, back, ear, face, forearm, neck and scalp. The furuncles were painted with the essential oil two or three times daily, after thorough cleaning. In the group treated with the essential oil, only one furuncle required incision, and in 15 patients, the furuncles were completely cured after 8 days of treatment. The only adverse reaction was slight temporary stinging reported by three patients. In the untreated control group, furuncles on five of the 10 patients required incision and the infected site of the furuncles was still apparent after 8 days (20).

Contraindications

Aetheroleum Melaleucae Alternifoliae is contraindicated in cases of known allergy to plants of the Myrtaceae family.

Warnings

Not for internal use. Keep out of reach of children (see Adverse reactions).

Precautions

No information available on general precautions or precautions concerning drug interactions; drug and laboratory test interactions; carcinogenesis, mutagenesis, impairment of fertility; teratogenic and non-teratogenic effects in pregnancy; nursing mothers; or paediatric use. Therefore, Aetheroleum Melaleucae Alternifoliae should not be administered during pregnancy or lactation or to children without medical supervision.

Adverse reactions

Allergic contact dermatitis after external application and ingestion of Aetheroleum Melaleucae Alternifoliae has been reported (26, 40-44). No adverse reactions were reported in two patch tests using preparations containing up to 5% essential oil (45, 46). Accidental ingestion of 10 ml essential oil caused confusion, disorientation and loss of coordination in a 23-month-old child (47). Ingestion of 2.5 ml essential oil by a 60-year-old man resulted in a severe rash and a general feeling of malaise (48). Induction of a comatose state lasting 12 hours, followed by 36 hours of a semi-conscious state accompanied by hallucinations, was reported in one patient after ingestion of approximately half a cup (120 ml) of the essential oil. Abdominal pain and diarrhoea lasting up to 6 weeks were also reported (38).

Dosage forms

Essential oil (1, 2). Store in a well-filled, airtight container, protected from heat and light.

Posology

(Unless otherwise indicated)

External application of the essential oil at concentrations of 5-100%, depending on the skin disorder being treated (16-23).

References

1. Essential oils - oil of Melaleuca, terpinen-4-ol type. AS 2782-1997. Sydney, Standards Association of Australia, 1997.

2. Deutscher Arzneimittel-Codex, Suppl. 8. Stuttgart, Govi-Verlag, 1996.

3. Oil of Melaleuca, terpinen-4-ol type (tea tree oil). ISO 4730:1996(E). Geneva, International Organization for Standardization, 1996.

4. Farnsworth NR, ed. NAPRALERT database. Chicago, University of Illinois at Chicago, IL, March 17, 1998 production (an online database available directly through the University of Illinois at Chicago or through the Scientific and Technical Network [STN] of Chemical Abstracts Services).

5. Osborne F, Chandler F. Australian tea tree oil. Canadian Pharmacy Journal, 1998, 131:42-46.

6. Cribb AB, Cribb JW. Useful wild plants in Australia. Sydney, Fontana/Collins, 1981.

7. Penfold AR, Morrison FR. Tea tree oils. In: Guenther E, ed. The essential oils. Vol. IV. New York, NY, D. Van Norstrand Co., 1950:60-72.

8. Southwell I, Lowe R, eds. Tea tree. The genus Melaleuca. Sydney, Harwood Academic Publishers, 1999.

9. Quality control methods for medicinal plant materials. Geneva, World Health Organization, 1998.

10. European pharmacopoeia, 3rd ed. Strasbourg, Council of Europe, 1996.

11. Guidelines for predicting dietary intake of pesticide residues, 2nd rev. ed. Geneva, World Health Organization, 1997 (document WHO/FSF/FOS/97.7).

12. Guenther E. Australian tea tree oils. Perfumery and Essential Oils Record, 1968:642-644.

13. Swords G, Hunter GLK. Composition of Australian tea tree oil (Melaleuca alternifolia). Journal of Agricultural and Food Chemistry, 1978, 26:734-737.

14. Brophy JJ et al. Gas chromatographic quality control for oil of Melaleuca terpinen-4-ol type (Australian tea tree). Journal of Agricultural and Food Chemistry, 1989, 37: 1330-1335.

15. Verghese et al. Indian tea tree (Melaleuca alternifolia Cheel) essential oil. Flavour and Fragrance Journal, 1996, 11:219-221.

16. Bassett IB et al. A comparative study of tea tree oil versus benzoyl peroxide in the treatment of acne. Medical Journal of Australia, 1990, 153:455-458.

17. Belaiche P. Letter to the editor. Phytotherapy Research, 1988, 2:157.

18. Blackwell AL. Tea tree oil and anaerobic (bacterial) vaginosis. Lancet, 1991, 337:300.

19. Buck DS et al. Comparison of two topical preparations for the treatment of onychomycosis: Melaleuca alternifolia (tea tree) oil and clotrimazole. Journal of Pharmacy Practice, 1994, 38:601-605.

20. Feinblatt HM. Cajeput-type oil for the treatment of furunculosis. Journal of the National Medical Association, 1960, 52:32-34.

21. Pena EF. Melaleuca alternifolia oil. Its use for trichomonal vaginitis and other vaginal infections. Obstetrics and Gynecology, 1962, 19:793-795.

22. Tong MM et al. Tea tree oil in the treatment of tinea pedis. Australas Journal of Dermatology, 1992, 33:145-149.

23. Walker M. Clinical investigation of Australian Melaleuca alternifolia oil for a variety of common foot problems. Current podiatry, 1972, 18:7-15.

24. Altman PM. Australian tea tree oil. Australian Journal of Pharmacy, 1988, 69:276-278.

25. Altman PM. Australian tea tree oil: a natural antiseptic. Australian Journal of Biotechnology, 1989, 3:247-248.

26. Carson CF, Riley TV. Toxicity of the essential oil of Melaleuca alternifolia or tea tree oil. Journal of Toxicology (Clinical Toxicology), 1995, 32:193-194.

27. Carson CF, Riley TV. Antimicrobial activity of the major components of the essential oils of Melaleuca alternifolia. Journal of Applied Bacteriology, 1995, 78:264-269.

28. Carson CF, Riley TV. In vitro activity of the essential oil of Melaleuca alternifolia against Streptococcus spp. Journal of Antimicrobial Chemotherapy, 1996, 37:1177-1178.

29. Chan CH, Loudon KW. Activity of tea tree oil on methacillin-resistant Staphylococcus aureus (MRSA). Journal of Hospital Infection, 1998, 39:244-245.

30. Nelson RRS. In vitro activities of five plant essential oils against methacillinresistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecium. Journal of Antimicrobial Chemotherapy, 1997, 40:305-306.

31. Concha JM et al. Antifungal activity of Melaleuca alternifolia (tea tree) oil against various pathogenic organisms. Journal of the American Podiatry Medical Association, 1998, 88:489-492.

32. Hammer KA et al. In vitro activity of essential oils, in particular Melaleuca alternifolia (tea tree) and tea tree oil products, against Candida spp. Journal of Antimicrobial Chemotherapy, 1998, 42:591-595.

33. Nenoff P et al. Antifungal activity of the essential oil of Melaleuca alternifolia (tea tree oil) against pathogenic fungi in vitro. Skin Pharmacology, 1996, 9:388-394.

34. Viollon C, Chaumont JP. Antifungal properties of essential oils and their main components upon Cryptococcus neoformans. Mycopathologia, 1994, 128:151-153.

35. Williams LR et al. Therapeutic use for tea tree oil. Australian Journal of Pharmacy, 1997, 78:285-287.

36. Carson CF, Riley TV. Susceptibility of Propionibacterium acnes to the essential oil of Melaleuca alternifolia. Letters in Applied Microbiology, 1994, 19:24-25.

37. Carson CF et al. Efficacy and safety of tea tree oil as a topical antimicrobial agent. Journal of Hospital Infection, 1998, 40:175-178.

38. Seawright A. Tea tree oil poisoning (comment). Medical Journal of Australia, 1993, 159:831.

39. Villar D et al. Toxicity of Melaleuca oil and related essential oils applied topically on dogs and cats. Veterinary and Human Toxicology, 1994, 36:139-142.

40. Apted JH. Contact dermatitis associated with the use of tea tree oil. Australas journal of dermatology, 1991, 32:177.

41. De Groot AC et al. Systemic contact dermatitis from tea tree oil. Contact Dermatitis, 1992, 27:279-280.

42. Knight TE, Hausen BM. Melaleuca oil (tea tree oil) dermatitis. Journal of the American Academy of Dermatology, 1994, 30:423-427.

43. Selvaag E et al. Contact allergy to tea tree oil and cross-sensitization to colophony. Contact Dermatitis, 1994, 31:124-125.

44. Van der Valk PGM et al. Allergisch contacteczeem voor “tea tree” olie. Nederlands Tijdschrift voor Geneeskunde, 1994, 138:823-825.

45. De Groot AC. Airborne allergic contact dermatitis from tea tree oil. Contact Dermatitis, 1996, 35:304-305.

46. Bhushan M, Beck MH. Allergic contact dermatitis from tea tree oil in a wart paint. Contact Dermatitis, 1997, 36:117-118.

47. Jacobs MR, Hornfeldt CS. Melaleuca oil poisoning. Journal of Toxicology (Clinical Toxicology), 1994, 32:461-464.

48. Elliott C. Tea tree oil poisoning. Medical Journal of Australia, 1993, 159:830-831.

 

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