A compound in liquorice may help to stop people with a herpes virus from developing cancer, research suggests.
Liquorice comes from the plant Glycyrrhiza glabra
A team at New York University found the compound - glycyrrhizic acid - could stop the virus triggering a form of cancer called Kaposi sarcoma.
The infection causes tumours to develop in tissues below the skin, and in internal organs. It is often found in people with a depressed immune system.
The research is published in the Journal of Clinical Investigation.
Many of the herpes viruses that infect people can sit latent in cells for long periods of time.
But when they are reactivated, they can cause painful symptoms and distress.
While treatment for active infections is progressing nicely, it remains very challenging to treat latent infections.
In particular, progress in treating herpes virus latency has lagged behind.
The New York team showed that glycyrrhizic acid (GA) could kill cells that were harbouring the herpes virus associated with Kaposi sarcoma.
The compound was able to disrupt the action of the key genes that control the virus' ability to stay lurking in a cell, latent, but with the potential to trigger disease.
As a result, production of crucial proteins was knocked out of kilter, destroying the delicate balance between virus and cell, and leading to the death of the infected cells.
The researchers say their work is the first time an anti-viral agent has been found that specifically targets genes required to maintain the virus in a latent state.
They hope it could lead to the development of new drugs to combat latent viral infections.
In an accompanying commentary, Dr Jeffrey Cohen, from the US National Institutes Of Health, said: "While a compound present in liquorice may seem like an unlikely candidate for the treatment of virus-associated cancers, it is important to remember that other traditional drugs have proved highly effective for some infectious diseases.
"Extracts of the wormwood plant, which is a traditional Chinese medication for treatment of febrile illnesses, contain artemisinin - derivatives of this compound have become first-line treatments for drug-resistant malaria.
"Thus, derivatives of GA or other traditional medicines might be used in the future for treating human diseases caused by latent virus infections."
Liquorice, derived from the root of Glycyrrhiza glabra, has been used for more than 4,000 years as a flavouring agent in foods, beverages, and tobacco.
It is also used as an alternative medicine for the treatment of gastric and duodenal ulcers, sore throat, bronchitis, cough, arthritis, adrenal insufficiency, and allergic diseases.