Details on Eucalyptus essential oil 

There are many compounds in Eucalyptus spp.. While the same compounds exist in many of the species, some compounds can be found in only one or a few species. Within species the quantity of essential oil and the specific compounds in the essential oil and extracts of dry and fresh leaves, buds, mature fruit, and bark vary with the origin of the tree and the age of the leaves.

E. globulusis one of the more important species of Eucalyptus. The essential oil in the leaves is commonly used for medicinal purposes. On average, between 70 and 95% of the oil is 1,8-cineole (eucalyptol). However, some studies have shown the oil to contain as little as 4% 1,8-cineole. The essential oil from the fruit, buds, and branches contain from 15-57% 1,8-cineole.

Other major components in the oil are:

• aromadendrene -- 8-23% in fruit, bud, and branch oils and 50-350 ppm in the leaves
• camphene -- traces in leaf oil
• cryptone -- 0-18% in leaf oil
• p-cymene -- <1-27% in leaf oil
• d-limonene -- traces in leaf oil
• alpha-phellandrene -- traces in leaf oil
• alpha-pinene -- <1-18% in leaf oil
• beta-pinene -- traces in leaf oil
• spathulenol -- <1-17% in leaf oil
• y-terpinene -- traces in leaf oil
• alpha-thujene -- 0-12% in fruit, bud, and branch oils

Other important compounds found in the leaves, buds, branches, and bark include:

• antioxidants (from bark) -- eriodictyol, naringenin, quercetin, rhamnazin, rhamnetin, taxifolin
• citriodorol
• cuminaldehyde -- 25-135 ppm in the leaves
• epiglobulol -- one study indicated 28,000 ppm in leaves
• euglobals -- These compounds are believed to have anti-tumor promoting activity.
• d-linalool -- leaves
• pinocarvone -- leaves
• rutin -- leaves
• tannins -- as much a 11% have been found in dry powdered leaves. Several activities have been attributed to tannins including antidysenteric, antimutagenic, antinephritic, antioxidant, antiviral, bactericide, cancer-preventive, hepatoprotective, pesticide, psychotropic, and viricide properties.
• gamma-terpinene -- leaves
• terpineol -- leaves

E. citriodora essential oil contains mainly citronellol (approximately 58%), which is best known for its aromatic properties. Other compounds in the plant include:
 

• aromadendrene
• citronellal -- 50-18,020 ppm in the leaves
• citronellic acid -- 1% in leaf oil
• citronellol -- 7.6% in leaf oil and 230-4,000 ppm in the leaves
• citronellyl acetate -- 24% in leaf oil and 20-130 ppm in the leaves
• p-cymene -- 10-180 ppm in the leaves
• limonene -- 20-1,420 ppm in the leaves
• linalool -- 15-180 ppm in the leaves
• alpha-pinene -- 5-380 ppm in the leaves
• tannin
• terpinene -- 1-180 ppm in the leaves
• terpinolene -- 5-160 ppm in the leaves
• ursolic acid

E. camaldulensis essential oil (from the leaves) ranges from less than 1 to over 2%. The quantity of 1,8-cineole in the oil ranges from 15-78%. Other compounds in the leaves include:
 

• betulinic acid
• eucalyptic and eucalyptolic acid
• oleanolic acid
• ursolic acid

Other Eucalyptus spp. of note and some of the compounds in them include:
 

• E. amplifolia, E. blakelyi, E. grandis, and E. tereticornis contain euglobals.
• E. cladocalyx contains traces of cyanogenic glycosides.
• E. cornea leaves contain up to 25% tannins.
• E. dives oil contains 33% piperitone.
• E. dunnii oil contains 48-58% 1,8-cineole, 5-7% globulol, 10-16.5% alpha-pinene, and 3-8% alpha-terpineol.
• E. macarthurrii oil contains 50% geranyl acetate.
• E. macrocarpa contains macrocarpal A, believed to be antibacterial.
• E. macarorryncha contains 12-20% rutin.
• E. maidenii and E. smithii oils contain 70-85% 1,8-cineole.
• E. viminalis oil contains high quantities of phellandrene (an inhalation irritant) and traces of cyanogenic glycosides.

It is very difficult to determine the potential for adverse reactions with the use of Eucalyptus treatments. This is because, as previously stated, the type and quantity of compounds depends on the species (which often is not indicated on the label of purchased preparations), the age of the leaves, the method used for drying leaves, buds, and bark, and the preparation methods of essential oils and extracts. In addition, many studies on adverse reactions do not indicate the species or preparation method used, complicating the situation. While Eucalyptus spp. can cause adverse reactions, the U.S. Food and Drug Administration has approved the use of eucalyptus oil and 1,8-cineole (eucalyptol) for human food use. The Council of Europe also has approved the use of the oil as a human food additive (at a level of 15 ppm). In France, infusions of E. globulus leaves can be registered as products for the treatment human benign bronchial disorders without toxicological studies. However, some toxicological studies are required for the registration of powdered leaf formulas.

Eucalyptus spp. contain high levels of phenolics and terpenoids which can be toxic. Animals such as the koala which eat Eucalyptus have developed methods for detoxifying the compounds in the liver. In addition, they have bacteria that degrade tannin-protein complexes. Most animals do not have this ability.

Several adverse reactions have been attributed to the use of or contact with Eucalyptus oils, extracts, and fresh and processed plant material. Some of the specific compounds that can be toxic or cause adverse reactions include: 1,8-cineole, cyanogenic glycosides, rutin, and tannins. Most studies on adverse reactions have been conducted with rodents and most documented cases of adverse reactions focus on humans. Less information is available on livestock.

Overdoses of the oil in humans cause gastro-intestinal burning, abdominal pain, vomiting, and convulsions, depress respiration and the central nervous system, and may lead to comas and death. The data on deaths caused by consumption of eucalyptus oil in humans are not consistent -- death has occurred after consumption of as little as 4-5 ml, while other people have become ill and recovered after consuming 120-220 ml of the oil. Based on rodent studies, the oral LD50 (the orally consumed dose that is lethal to 50% of the animals) for eucalyptus oil is very high -- 4.44g/kg body weight(BW) for rats and 3.32g/kg BW for mice. The LD50 is lower when only 1,8-cineole is used -- 2.48g/kg BW for rats. The dermal LD50 for rabbits is greater than 5g/kg BW.

Eucalyptus oil is not believed to be teratogenic or contaminate milk. However, some studies have indicated that citronellal and phellandrene, which can be found in some Eucalyptus spp., are weak mutagenics and carcinogenics, respectively.

As with toxicity, the efficacy of eucalyptus oils and extracts is most likely dependent on the their chemical composition. In general, oils from Eucalyptus spp. have antimicrobial properties. Two studies which tested the oils from several species showed that E. citriodora had the most antimicrobial activity. There was no relationship between 1,8-cineole content and antimicrobial activity. Other studies have demonstrated that the oil and leaf extracts of Eucalyptus spp. have antifungal and repellent activity.

Fresh leaves, leaf-extracts, and growth regulators and their intermediaries (which are endoperoxides) of Eucalyptus grandis were tested for their anthelmintic properties by Bennet-Jenkins and Bryant (1996). Leaves were fed to 5 goats with experimental infections of Haemonchus contortus (the barberpole worm) (and natural infections of Ostertagia) for seven days (two days with lucerne/oaten chaff and five days as the sole source of feed). At necropsy, the number of adult H. contortus in the E. grandis-fed goats was 91% lower than the number in 4 control goats. There was no significant difference in the number of Ostertagia. Isolated E. grandis compounds (and synthetic congeners) were affective in vitro and in vivo (in mice and sheep) -- but practical formulation and administration methods for these compounds have not been identified.

Many in vitro and a few in vivo tests have been conducted with extracts and oils of different Ecualyptus species. Following is a summary of some of the specific activities identified for Eucalyptus spp.:
 

• Eucalyptus oil (species not specified)
  • antibacterial -- concentrations ranging from 0.16 to >20 microliters/ml inhibited 22 bacterial strains in vitro.
  • antifungal -- concentrations ranging from 0.25 to 10 microliters/ml inhibited 11 fungi in vitro.
  • repellent activity -- effective in repelling Pediculus humanus (human body louse), with citronellal being the active compound.
• Isolated compounds from Eucalyptus spp.
  • ursolic acid -- exhibited anticholestatic activity and protected against hepatotoxicity (induced by paracetamol and galactosamine) in rats.
  • euglobals -- were shown to have antitumor properties.
• E. camaldulensis -- ethanol extracts showed activity against bacteria and fungi.
• E. globulus
  • antimicrobial -- essential oil has limited activity against Paenibacillus larvae, the causal agent of American foulbrood disease and methanol extracts of leaves at concentrations of 10mg/ml or less inhibited Staphylococcus aureus, Escherichia coli, Pseudomonas aerginosa, and Candida albicans in vitro.
  • antispasmodic -- water/alcohol extracts of leaves decreased smooth muscle contractions in vitro.
  • antifungal -- the oil is believed to have limited antifungal activity, although water extracts were not effective against the fungi Epidermophyton floccosum, Microsporum canis, and Trichophton mentagrophytes.
• E. macarthurii and E. riwagum -- mixed results were obtained when the essential oils were tested for antibacterial and antifungal activity in vitro.
• E. citriodora
  • antiinflammatory -- alcohol extracts of the leaves given to mice at concentrations of 100, 300, and 1,000 mg/kg BW inhibited induced paw oedema in mice by 12, 22, and 49%, respectively.
  • antibacterial and antifungal activity -- essential oil inhibited Bacillus megaterium, Staphylococcus aureus, Escherichia coli, Candida albicans, Aspergillus niger, and Zygorrhynchus spp. in vitro and inhibited ringworm causing fungi.

Listed below are some uses of E. globulus in humans:

• Anodyne -- China
• Antimalaria -- Honduras
• Antiseptic -- China, Honduras, and Turkey
• Arthritis -- China
• Asthma
• Astringent -- Turkey
• Bronchitis -- Mexico and U.S.
• Burn -- China
• Cancer -- Australia (Aborigine), China, Spain, and U.S.
• Catarrh -- Mexico, Turkey, and U.S.
• Cold -- Honduras and Mexico
• Cough -- Honduras
• Deodorant -- Turkey
• Diabetes -- Mexico
• Diaphoretic
• Diphtheria
• Dysentery -- China
• Expectorant -- Honduras
• Fever -- China, Honduras, and Turkey
• Flu -- Mexico
• Gingivitis -- U.S.
• Hemostat -- Turkey
• Inflammation
• Inhalant
• Insect repellent -- Honduras and Venezuela
• Laryngitis -- Mexico
• Malaria -- Spain and Venezuela
• Miasma -- Venezuela
• Purgative
• Respiratory
• Skin diseases (ringworm) -- Guatemala
• Sores, wounds -- China
• Spasms -- Honduras and Turkey
• Stimulant -- Turkey
• Suppurative
• Throat
• Tuberculosis -- China
• Vermifuge
• Tumors (Breast)