Eucalyptus oil (Eucalyptus citriodora)
Synonyms / Common Names / Related Terms
1,8-cineole, aerial eucalyptus, Australian fever tree leaf, blauer gommibaum, blue gum, cajuputol [C10H18O], camphor oil, catheter oil, cider gum, cineole [C10H18O], crown gall, cypellocarpa C., E. camaldulensis (red gum), E. citriodora (lemon-scented gum), E. coccifera (Tasmanian snow gum), E. dalrympleana (mountain gum), E. ficifolia (red flowering gum), E. fructicetorum F. Von Mueller, E. globulus Labillardiere, E. gunnii (cider gum), E. johnstonii (yellow gum), E. leucoxylon (white ironbark), E. maculate, E. occidentalis, E. parvifolia, E. pauciflora subsp. niphophila (snow gum), E. perriniana (spinning gum), E. saligna, E. sideroxylon (red ironbark), E. smithii R.T. Baker, E. urnigera (urn gum), E. viminalis Labill (euvimals), essence of eucalyptus rectifiee, essencia de eucalipto, eucalypti aetheroleum, eucalypti folium, eucalytpo setma ag, eucalyptol [C10H18O], Eucalyptus camaldulensis, Eucalyptus cladocalyx, eucalyptus dried leaves, eucalyptus essential oil, eucalyptus flower, eucalyptus globules tree, Eucalyptus globulus, eucalyptus leaf extract , eucalyptus pollen, Eucalyptus polybractea, Eucalyptus robusta, Eucalyptus spp., fevertree, gommier bleu, gum tree, kafur ag, lemon eucalyptus extract, lemon-scented gum, macrocarpal A, macrocarpal B, malee, mountain gum, Myrtaceae (family), oil of Eucalyptus citriodora, oleum eucalypti, red flowering gum, red gum, red ironbark, schonmutz, snow gum, southern blue gum, spinning gum, stringy bark tree, Tasmanian blue gum, Tasmanian snow gum, urn gum, verbenone, white ironbark, yellow gum.
Mechanism of Action
- Constituents: There are more than 500 species of Eucalyptus, ranging from shrubs to several hundred-foot trees. Eucalyptus leaves and oil are utilized for medicinal and other uses, such as fragrance in perfumes. Volatile oils are derived principally from species that are rich in 1,8-cineol (eucalyptol, a monoterpene), such as Eucalyptus globulus Labillardiere (blue gum), E. smithii, or E. fructicetorum. E. globulus Labillardiere is the most common medicinal species.40 Eucalyptus oil preparations may contain up to 80% 1,8-cineole.30 1,8-cineol is present in the oils of other plants as well, such as
. Other compounds present include macrocarpals (phloroglucinol-sesquiterpenes), other monoterpenes (D-limonene, α-pinene, β-pinene, p-cymene), alkaloids, eucalyptin, phenols, flavonoids (6,8-di-C-methylkaempferol 3-methyl ether; oleanolic acid; 2 alpha,3 beta-dihydroxyurs-12-en-28-oic acid), 8-desmethyl-eucalyptin, tannins, terpenoid phenolaldehydes, 2'6'-dihydroxy-3'-methyl-4'-methoxy-dihydrochalcone, and verbenone, a monoterpene bicyclic ketone.21,10,41,16,18,42,40,40,3,4 The exact mechanism of action of eucalyptus oil is unknown at this time, but may involve antimicrobial and anti-inflammatory effects.
- Anti-inflammatory and pulmonary effects: An in vitro study of human blood monocytes reported dose-dependent, significant inhibition of multiple cytokines, with suggested application in the treatment of airway inflammation.24,25 Anti-inflammatory activity and anti-nociceptive effects have been demonstrated elsewhere in animal models26,1 and may be related to antioxidant activity38. In addition, expectorant activity29, antioxidant effects39, and effects on surface tension in respiratory distress syndrome43 have been studied. Burrow et al. reported stimulation of nasal cold receptors without effects on nasal resistance to airflow44, thus hypothesizing that the oil may simply act as a counter-irritant. Acknowledging possible slight symptomatic benefit and antimicrobial activity in respiratory conditions, Riechelmann et al. demonstrated that the in vitro function of human ciliary respiratory cells is impaired at higher concentrations of eucalyptus oil.45
- Antimicrobial effects: The antimicrobial effects of eucalyptus have been studied in animal and basic science research. It has been suggested that the Australian Koala's ingestion and skin surface excretion of eucalyptus may serve an anti-parasitic function (and may also serve a homeostatic/thermal regulatory function).29 In vitro anti-fungal properties have been reported in multiple eucalyptus species.22,23 Anti-viral activity against herpes simplex virus (HSV-1, HSV-2) has been demonstrated in cell culture.30 Eucalyptus oil in laboratory and laundry testing has shown significant reduction in live mites35, and repellent activity against four biting arthropods36. Studies of medicinal plant extracts have demonstrated broad antimicrobial activity of eucalyptus17,19,6 against Alicyclobacillus acidoterretris, Bacillus cereus, E. coli, Enterococcus faecalis, MRSA, Propionibacterium acnes, S. aureus, fungus including C. albicans isolates21,4,Trichophyton mentagrophytes, and other Gram-positive bacteria. Specific activity against periodontopathic bacteria, such as Porphyromonas gingivalis, Actinobacillus actinomycetemcomitans, Fusobacterium nucleatum, Streptococcus mutans, and Streptococcus sobrinus18,4,20 has been reported. Crown gall, a plant tumor obtained from E. globules, has shown antibacterial activity against E. faecallis, Ps. Aeruginosa, Bac. Subtilis and Staph. epidermidis.2 Extract of Eucalyptus comaldensis (50mg in 0.1mL medium) at pH 5.35 caused death of T. vaginalis after 24 hours.12 An in vitro study in rat liver suggested that protonophoric activity may contribute to the cytotoxicity and antimicrobial properties.3
- Cytotoxic activity: Eucalyptus camaldulensis has been screened for cytotoxic activity against human ECV-304 cells.27
- Insect repellant: Essential oil extracted from dried fruits of eucalyptus (Eucalyptus camaldulensis), have been tested for their repellency against the adult females of Culex pipiens.32 Eucalyptus oil has been tested for its ability to repel Aedes albopictus mosquitoes under laboratory conditions.33 Eucalyptus oil (15%) gave protection to humans for least three hours; the protection time was prolonged to five hours after adding 5% vanillin. The larvicidal activity and repellency of eucalyptus oil has been tested against three mosquito species: Aedes albopictus, Ae. aegypti, and Culex pipiens pallens.34
- Vascular effects: Hong et al. conducted a study of topical Eucalyptamint® (eucalyptus oil, lanolin, and 15%
) on cutaneous blood flow and temperature.37 Ten healthy subjects served as their own controls and consecutively received either the active agent or placebo. Subjective ratings, blood flow, and skin and muscle temperature were monitored for 60 minutes following application. Subjective perceptions were not significantly different, although blood flow, skin, and muscle temperatures were significantly altered for 45 minutes compared to placebo or to baseline measurements.
- Other effects: Other research into eucalyptus' mechanism of action has included demonstration of anti-tumor promoting effects with in vitro and in vivo studies of euglobal compounds isolated from eucalyptus plants8,9,46; induction of apoptosis in human myeloid leukemia cells10; inhibition of human plasminogen activator inhibitor28; examination of a serotonergic (5HT3) mechanism; appetite suppressant effects in animal feeding studies31; stimulation of insulin secretion; and enhancement of muscle glucose uptake and metabolism in diabetic animal models11. Alpha-pinene and eucalyptus globules oil, has been shown to inhibit nuclear translocation of Nuclear Factor Kappa B.46,47 An in vitro study demonstrated that high concentrations of essential oils may reduce human nasal respiratory cell ciliary activity.45
- There is limited available human pharmacodynamic/kinetic information on eucalyptus. Lipophilic monoterpenes appear to be readily absorbed orally, with a primarily oxidative metabolism that may require induction of the cytochrome P450 enzyme system and subsequent urinary excretion.16 Gastrointestinal absorption of eucalyptus is rapid and is likely enhanced by lipids and milk. Eucalyptus is believed to be eliminated via the gastrointestinal tract and the lungs.
- Eucalyptol (1,8-cineole), which is present in eucalyptus oil, is well absorbed via inhalation with a reported peak plasma level at 18 minutes.48
- Eucalyptol (1,8-cineole) has been found in vitro and in animals to possess cytochrome P450-inducing activity.14,13,15
- Verbenone, a monterpene bicyclic ketone, is a component of the essential oil from
species, such as eucalyptus globules.42 In one study, verbenone was found to be converted to 10-hydroxyverbenone by rat and human liver microsomal cytochrome P450 enzymes, and indicated that CYP2A6 is a principal enzyme in verbenone hydroxylation in humans.
- The uptake and transepithelial transport of the three main constituents, macrocarpal A (M-A), macrocarpal B (M-B), and cypellocarpa C (Cy-C), from the fruits of Eucalyptus globulus Labill. were investigated.5 The intestinal absorption of M-A, M-B, and Cy-C was passive diffusion as the dominating process and Cy-C was partly ATP-dependent.
- The antibacterial activity of Eucalyptus globulus leaf extract was determined for 56 isolates of Staphylococcus aureus, 25 isolates of Streptococcus pyogenes, 12 isolates of Streptococcus pneumonia, and seven isolates of Haemophilus influenza obtained from 200 clinical specimens of patients with respiratory tract disorders.7 MIC50s for these species were 64, 32, 16, and 16mg/L, respectively. MIC90s were 128, 64, 32, and 32 mg/L, respectively. MBCs were 512, 128, 64, and 64mg/L, respectively. These results suggest that further studies to clarify the possible therapeutic role of E. globulus leaf extract in the treatment of respiratory tract infection are warranted.
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- Brantner, A. H., Asres, K., Chakraborty, A., Tokuda, H., Mou, X. Y., Mukainaka, T., Nishino, H., Stoyanova, S., and Hamburger, M. Crown gall -- a plant tumour with biological activities. Phytother Res 2003;17(4):385-390. 12722146
- Spiridonov, N. A., Arkhipov, V. V., Foigel, A. G., Shipulina, L. D., and Fomkina, M. G. Protonophoric and uncoupling activity of royleanones from Salvia officinalis and euvimals from Eucalyptus viminalis. Phytother Res 2003;17(10):1228-1230. 14669263
- Takahashi, T., Kokubo, R., and Sakaino, M. Antimicrobial activities of eucalyptus leaf extracts and flavonoids from Eucalyptus maculata. Lett Appl Microbiol 2004;39(1):60-64. 15189289
- Yang, X. W., Guo, Q. M., Wang, Y., Xu, W., Tian, L., and Tian, X. J. Intestinal permeability of antivirus constituents from the fruits of Eucalyptus globulus Labill. in Caco-2 Cell Model Bioorg Med Chem Lett 2-15-2007;17(4):1107-1111. 17118653
- Sartorelli, P., Marquioreto, A. D., Amaral-Baroli, A., Lima, M. E., and Moreno, P. R. Chemical composition and antimicrobial activity of the essential oils from two species of Eucalyptus. Phytother Res 2007;21(3):231-233. 17154233
- Salari, M. H., Amine, G., Shirazi, M. H., Hafezi, R., and Mohammadypour, M. Antibacterial effects of Eucalyptus globulus leaf extract on pathogenic bacteria isolated from specimens of patients with respiratory tract disorders. Clin Microbiol Infect 2006;12(2):194-196. 16441463
- Takasaki, M., Konoshima, T., Fujitani, K., Yoshida, S., Nishimura, H., Tokuda, H., Nishino, H., Iwashima, A., and Kozuka, M. Inhibitors of skin-tumor promotion. VIII. Inhibitory effects of euglobals and their related compounds on Epstein-Barr virus activation. (1). Chem Pharm Bull (Tokyo) 1990;38(10):2737-2739. 1963812
- Takasaki, M., Konoshima, T., Kozuka, M., and Tokuda, H. Anti-tumor-promoting activities of euglobals from Eucalyptus plants. Biol Pharm Bull 1995;18(3):435-438. 7550098
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- Gray, A. M. and Flatt, P. R. Antihyperglycemic actions of Eucalyptus globulus (Eucalyptus) are associated with pancreatic and extra-pancreatic effects in mice. J Nutr 1998;128(12):2319-2323. 9868176
- Mahdi, N. K., Gany, Z. H., and Sharief, M. Alternative drugs against Trichomonas vaginalis. East Mediterr Health J 2006;12(5):679-684. 17333809
- Pass, G. J., McLean, S., Stupans, I., and Davies, N. Microsomal metabolism of the terpene 1,8-cineole in the common brushtail possum (Trichosurus vulpecula), koala (Phascolarctos cinereus), rat and human. Xenobiotica 2001;31(4):205-221. 11465406
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- Miyazawa, M., Shindo, M., and Shimada, T. Oxidation of 1,8-cineole, the monoterpene cyclic ether originated from eucalyptus polybractea, by cytochrome P450 3A enzymes in rat and human liver microsomes. Drug Metab Dispos 2001;29(2):200-205. 11159812
- McLean, S. and Foley, W. J. Metabolism of Eucalyptus terpenes by herbivorous marsupials. Drug Metab Rev 1997;29(1-2):213-218. 9187519
- Kumar A, Sharma VD, Sing AK, and et al. Antibacterial properties of different Eucalyptus oils. Fitoterapia 1988;59(2):141-144.
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- Juergens, U. R., Stober, M., Schmidt-Schilling, L., Kleuver, T., and Vetter, H. Antiinflammatory effects of euclyptol (1.8-cineole) in bronchial asthma: inhibition of arachidonic acid metabolism in human blood monocytes ex vivo. Eur J Med Res 9-17-1998;3(9):407-412. 9737886
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