title: Terpinen-4-ol, the main component of the essential oil of Melaleuca alternifolia (tea tree oil), suppresses inflammatory mediator production by activated human monocytes.
abstract: OBJECTIVE
  To evaluate potential antiinflammatory properties of tea tree oil, the essential oil steam distilled from the Australian native plant, Melaleuca alternifolia.
  
  
  METHODS
  The ability of tea tree oil to reduce the production in vitro of tumour necrosis factor-alpha (TNFalpha), interleukin (IL)-1beta, IL-8, IL-10 and prostaglandin E2 (PGE2) by lipopolysaccharide (LPS)-activated human peripheral blood monocytes was examined.
  
  
  RESULTS
  Tea tree oil emulsified by sonication in a glass tube into culture medium containing 10% fetal calf serum (FCS) was toxic for monocytes at a concentration of 0.016% v/v. However, the water soluble components of tea tree oil at concentrations equivalent to 0.125% significantly suppressed LPS-induced production of TNFalpha, IL-1beta and IL-10 (by approximately 50%) and PGE2 (by approximately 30%) after 40 h. Gas chromatography/mass spectrometry identified terpinen-4-ol (42 %), a-terpineol (3 %) and 1,8-cineole (2%, respectively, of tea tree oil) as the water soluble components of tea tree oil. When these components were examined individually, only terpinen-4-ol suppressed the production after 40 h of TNFalpha, IL-1beta, IL-8, IL-10 and PGE2 by LPS-activated monocytes.
  
  
  CONCLUSIONS
  The water-soluble components of tea tree oil can suppress pro-inflammatory mediator production by activated human monocytes.
authors.affiliation: Department of Microbiology and Infectious Diseases, School of Medicine, Flinders University, Adelaide, Australia. Prue.Hart@flinders.edu.au
authors.forename: P H
authors.initials: PH
authors.lastname: Hart
authors.forename: C
authors.initials: C
authors.lastname: Brand
authors.forename: C F
authors.initials: CF
authors.lastname: Carson
authors.forename: T V
authors.initials: TV
authors.lastname: Riley
authors.forename: R H
authors.initials: RH
authors.lastname: Prager
authors.forename: J J
authors.initials: JJ
authors.lastname: Finlay-Jones
mesh_terms: D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D000081005:Cyclohexane Monoterpenes; D003511:Cyclohexanols; D053138:Cyclohexenes; D016207:Cytokines / Q000096:biosynthesis*; D004655:Emulsions / Q000494:pharmacology; D000077591:Eucalyptol; D006801:Humans; D007375:Interleukin-1 / Q000096:biosynthesis; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000187:drug effects / Q000276:immunology; D008610:Menthol / Q000031:analogs & derivatives* / Q000494:pharmacology; D009000:Monocytes / Q000187:drug effects / Q000276:immunology*; D039821:Monoterpenes; D010946:Plants, Medicinal; D012995:Solubility; D020947:Tea Tree Oil / Q000737:chemistry / Q000494:pharmacology*; D013729:Terpenes / Q000494:pharmacology*; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D000081005:Cyclohexane Monoterpenes; D003511:Cyclohexanols; D053138:Cyclohexenes; D016207:Cytokines; D004655:Emulsions; D007375:Interleukin-1; D008070:Lipopolysaccharides; D039821:Monoterpenes; D013729:Terpenes; D014409:Tumor Necrosis Factor-alpha; D008610:Menthol; C016775:alpha-terpineol; C034019:terpinenol-4; D020947:Tea Tree Oil; D000077591:Eucalyptol