Anti-inflammatory effects of Melaleuca alternifolia essential oil on human polymorphonuclear neutrophils and monocytes

Free Radic Res. 2004 Aug;38(8):805-11. doi: 10.1080/1071576042000220247.


Objective and design: The fungicidal and bactericidal actions of the essential oil (EO) of Melaleuca alternifolia seem well established, but their anti-inflammatory and anti-oxidative effects remain unclear. In this study, we investigated in vitro the possible role of whole M. alternifolia EO as a modulator of the oxidative response, i.e. reactive oxygen species (ROS) production, of leukocytes (monocytes and polymorphonuclear neutrophils (PMNs)) in humans.

Methods: Whole blood leukocytes from healthy human volunteers (n = 7), isolated from erythrocytes by haemolytic shock, were incubated for 30 min with M. alternifolia EO (0-0.1%) to determine their ROS production by flow cytometry with or without stimulation of cells. We compared the effects of 3 different stimulating agents acting differently on transductional pathways to stimulate the ROS production: a phorbol ester (PMA), formyl-methionyl-leucyl-phenylalanine (fMLP) and opsonised zymosan (OZ).

Results: As attested by the Krüskall-Wallis test, M. alternifolia EO at 0.1% directly stimulated ROS production by PMNs (x 8.7 vs. 0% EO, p < 0.05) and increased the intracellular ROS produced by monocytes. Whichever the stimulating agent used (PMA, fMLP or OZ), M. alternifolia EO decreased the intracellular ROS production at the dilution of 0.1% by PMNs and monocytes, more so with PMNs.

Conclusion: M. alternifolia EO may be both a direct active mediator of the bactericidal action of the circulating leukocytes and may be efficient in protecting the organism from an excess of ROS, through an anti-oxidant and radical scavenging activity.

MeSH terms

  • Anti-Inflammatory Agents / chemistry
  • Anti-Inflammatory Agents / pharmacology*
  • Flow Cytometry
  • Humans
  • Hydrogen Peroxide / metabolism
  • Melaleuca / chemistry
  • Monocytes / drug effects*
  • Monocytes / metabolism
  • Neutrophils / drug effects*
  • Neutrophils / metabolism
  • Reactive Oxygen Species / metabolism
  • Signal Transduction / drug effects
  • Tea Tree Oil / chemistry
  • Tea Tree Oil / pharmacology*


  • Anti-Inflammatory Agents
  • Reactive Oxygen Species
  • Tea Tree Oil
  • Hydrogen Peroxide