Trans-anethole (a flavour component of anise and fennel), estragole (found in basil), eugenol (from clove bud oil) and isoeugenol (in ylang ylang) are some of the ingredients that show potential of becoming anti-inflammatory substances in the first study of its kind to assess the value of using certain essential oil compounds to treat inflammation caused by fine particles of polluted air.
“Nowadays, there is increased interest in complementary and alternative medicine”
Miriana Kfoury, Lebanese University
“Nowadays, there is increased interest in complementary and alternative medicine,” says Miriana Kfoury, from the Lebanese University and lead author of the study. “People are choosing these treatments because they are more personal, less invasive and often have lower costs. Thus, any prevention approach or treatment that utilises natural compounds, such as essential oils, is trusted and accepted particularly to neutralise the constant threat from air pollution.”
Kfoury and her team first collected air pollutant samples in Beirut then introduced them to human cell cultures of normal bronchial epithelial cells and cancer derived hepatic cells. The cells started to secrete pro-inflammatory cytokines, which normally increase when the immune system is fighting an infection and has endured tissue damage. The researchers established that trans-anethole, estragole, eugenol and isoeugenol all have cytotoxicity, which means they could cause cell death at relatively high concentrations. They were able to determine the level of cytotoxicity of these oil compounds, which is important to establish the maximum dose for the assessment of anti-inflammatory properties.
In the second round of tests, the four compounds were introduced to a combination of cell lines and air pollutants to see whether these could protect liver and lung cells damaged by fine particle air pollutants. The essential oil compounds tested were found to decrease the level of cytokine IL-6 by up to 96 per cent and cytokine IL-8 by 87 per cent.
“This finding merits further exploration to explain the mechanism of action of essential oils components in cells and to search for any synergistic effect between essential oils components by testing mixtures. In vivo studies will also be necessary,” says Kfoury.
But Roy Harrison, an environmental health and risk management professor at the University of Birmingham in the United Kingdom and one of the editors-in-chief of the Climate and Atmospheric Science, a Nature partner journal, says he does not believe that studies of “this kind” tell us a great deal. “Observations obtained at high exposures in human cell lines do not necessarily predict the behaviour in people,” he tells SciDev.Net. “The essential oil components that were tested probably have an anti-oxidant activity, which would be expected to reduce inflammation. There are many natural anti-oxidants in fruits, vegetables, nuts and wine, which would probably have the same effect in experiments of this kind.”
This piece was produced by SciDev.Net’s South-East Asia & Pacific desk.