Interactions between components of the essential oil of Melaleuca alternifolia

J Appl Microbiol. 2001 Sep;91(3):492-7. doi: 10.1046/j.1365-2672.2001.01406.x.

Abstract

Aims: This study compared the antimicrobial activity of Melaleuca alternifolia (tea tree) oil with that of some of its components, both individually and in two-component combinations.

Methods and results: Minimum inhibitory concentration and time-kill assays revealed that terpinen-4-ol, the principal active component of tea tree oil, was more active on its own than when present in tea tree oil. Combinations of terpinen-4-ol and either gamma-terpinene or p-cymene produced similar activities to tea tree oil. Concentration-dependent reductions in terpinen-4-ol activity and solubility also occurred in the presence of gamma-terpinene.

Conclusion: Non-oxygenated terpenes in tea tree oil appear to reduce terpinen-4-ol efficacy by lowering its aqueous solubility.

Significance and impact of the study: These findings explain why tea tree oil can be less active in vitro than terpinen-4-ol alone and further suggest that the presence of a non-aqueous phase in tea tree oil formulations may limit the microbial availability of its active components.

MeSH terms

  • Anti-Infective Agents, Local / chemistry
  • Anti-Infective Agents, Local / pharmacology*
  • Candida albicans / drug effects
  • Cyclohexane Monoterpenes
  • Escherichia coli / drug effects
  • Herb-Drug Interactions
  • Magnoliopsida / chemistry*
  • Microbial Sensitivity Tests
  • Monoterpenes*
  • Oils, Volatile / chemistry
  • Oils, Volatile / pharmacology
  • Plant Oils / chemistry
  • Plant Oils / pharmacology*
  • Plants, Medicinal / chemistry*
  • Pseudomonas aeruginosa / drug effects
  • Solubility
  • Staphylococcus aureus / drug effects
  • Tea / chemistry
  • Terpenes / chemistry
  • Trees / chemistry

Substances

  • Anti-Infective Agents, Local
  • Cyclohexane Monoterpenes
  • Monoterpenes
  • Oils, Volatile
  • Plant Oils
  • Tea
  • Terpenes
  • gamma-terpinene
  • terpinenol-4