Niaouli Melaleuca quinquenervia is a tree of the Myrtaceae family, which also includes tea tree, nutmeg and guava. It is native to the eastern coast of Australia and New Caledonia.
Niaouli essential oil produced from its leaves is known for its medicinal properties. It is traditionally used to fight against respiratory infections such as colds, rhinitis, influenza, angina, sinusitis but also shingles, chickenpox, oral herpes as well as wounds, psoriasis and acne. It is empirically known to be an antibacterial, fungicide, antiviral, skin tonic, venous decongestant.
It also has an insecticidal and repellent effect. Its most important active ingredients are 1,8-cineole and viridiflorol, which each represent about 30% of the essential oil composition.
Niaouli essential oil decreases the formation of paw edema induced in rats in a dose and time dependent manner. It also has an analgesic and anti-pyretic effect. At a dose of 1,800 mg/kg, it is as effective as 50 mg/kg of lysine acetylsalicylate, a nonsteroidal anti-inflammatory drug. This activity is associated with its oxygenated components, which represent up to 82.76% of its composition and which decrease the release of histamine from mast cells and the production of 5-hydroxytriptamine. These 2 substances are responsible for the transudation of plasma, vasodilation and the formation of edemas. Niaouli essential oil also inhibits the synthesis of kinins which increase vascular permeability and prostaglandins responsible for the migration of leukocytes into the inflamed area.
The analgesic effect is explained by a blockade of the excitation of the afferent nociceptive nerves, which gives Niaouli a central analgesic effect.
Niaouli essential oil significantly drops the temperature. Its anti-pyretic effect is due to the blocking of the production of prostaglandins and the desensitization of peripheral nociceptors (ACHA & al., 2019).
Synergistic activity between 1,8-cineole and chlorhexidine has been demonstrated against MRSA, especially S. Aureus but also E. Coli, K. Pneumoniae, E. Faecalis and C. Albicans. This is because 1,8-cineole acts on the plasma membrane of bacteria, just like chlorhexidine (SIMSEK & al., 2017 ; TAVARES & al., 2020).
The anti-bacterial activity of Niaouli is based on the fact that it surrounds and isolates the bacteria so that it can penetrate its membrane. It also interferes with the energy metabolism of the cell, eventually inducing its lysis (TAVARES & al., 2020).
Niaouli essential oil has an adulticidal effect on the mosquitoes Aedes aegypti, Aedes albopictus and Culex quinquefasciatus. In some cases, 100% mortality is obtained after 30 minutes of contact at a concentration of 40 mg/ml. A larvicidal effect is also observed on all three species, Culex quinquefasciatus being the most sensitive (LEYVA & al., 2016).
In another study from 2010, it caused more than 80% mortality in Aedes aegypti larvae. This effect is associated with 1,8-cineole as well as components present in lower concentrations such as (E)-nerolidol (PARK & al., 2010).
Niaouli essential oil mixed with dipropylene glycol also has a repellent effect on Aedes aegypti. Under laboratory conditions, the repellent effect may last up to 5 hours. In the field, the repellent effect is shorter: it reaches 1 hour 30 minutes. This effect is mainly exerted by the combination of monoterpenes including 1,8-cineole and sesquiterpenes including viridiflorol, which are the two major components of Niaouli essential oil. In addition, in this study, subjects also observed a therapeutic effect on wounds caused by old insect bites (LEYVA & al., 2012).
