A study led by University of Arizona researcher Kelly Bright has found that carvacrol - the substance in oregano oil that gives the pizza herb its distinctive warm and aromatic smell and flavour - is effective against norovirus, causing the breakdown of the virus' tough outer coat.

Norovirus, also known as the winter vomiting disease, is the leading cause of vomiting and diarrhoea around the world.

"Carvacrol could potentially be used as a food sanitiser and possibly as a surface sanitiser, particularly in conjunction with other antimicrobials," said Bright.

"We have some work to do to assess its potential but carvacrol is an interesting prospect," she said.

Bright and her team - former graduate student Damian Gilling, former visiting scholar Masaaki Kitajima and current doctoral student Jason Torrey - determined whether oregano oil and carvacrol, the primary active component in oregano oil, were effective against mouse norovirus.

In the experiments, oregano oil had limited efficacy but carvacrol resulted in a nearly 10,000-fold reduction in viral infectivity within an hour. In other words, it is 99.99 percent effective against the virus.

"Carvacrol does not act as quickly as bleach, which will act in minutes or even seconds, but it is still effective," Bright said.

Since carvacrol is a plant compound, it is generally regarded as safe for human consumption, Bright added.

This is also the first study that looks at the mechanism of breakdown in detail of a plant antimicrobial on a non-enveloped virus, Bright said.

Nonenveloped viruses like noroviruses tend to be the ones that target the gastrointestinal tract. Their tough outer protein shell - called the capsid - makes them resistant against stomach acid and allows them to travel through the gastrointestinal tract unharmed.

Bright's research revealed the exact mechanism of how this plant compound kills a no enveloped virus.

"Carvacrol acts directly on the virus' outer shell and breaks it down," she said.

"The virus needs that capsid to attach to the human cell, so if you break down that shell, it won't be able to cause an infection. In addition, it breaks down the virus' RNA genome.

These effects are therefore likely irreversible, so the mechanism of action is an example of true virus inactivation," said Bright.

The study is published in the journal of Applied Microbiology.


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