An ingredient commonly found in toothpaste could be employed as an anti-malarial drug against strains of the malaria parasite that have grown resistant to one of the currently used drugs. The discovery was described in a study published in the journal Scientific Reports.

When a mosquito infected with malaria parasites bites someone, it transfers the parasites into their bloodstream via its saliva. These parasites work their way into the liver, where they mature and reproduce.

After a few days, the parasites leave the liver and hijack red blood cells, where they continue to multiply, spreading around the body and causing symptoms, including potentially life-threatening complications.

Malaria kills over half a million people each year, predominantly in Africa and south-east Asia. While a number of medicines are used to treat the disease, malaria parasites are growing increasingly resistant to these drugs, raising the spectre of untreatable malaria in the future.

The team of researchers at the University of Cambridge employed the Robot Scientist 'Eve' in a high-throughput screen and discovered that triclosan, an ingredient found in many kinds of toothpaste, may help fight against drug-resistance.

When used in toothpaste, triclosan prevents the build-up of plaque bacteria by inhibiting the action of an enzyme known as enoyl reductase (ENR), which is involved in the production of fatty acids.

Scientists have known for some time that triclosan also inhibits the growth in culture of the malaria parasite Plasmodium during the blood-stage, and assumed that this was because it was targeting ENR, which is found in the liver. 

Working with 'Eve', the research team discovered that in fact, triclosan affects parasite growth by specifically inhibiting an entirely different enzyme of the malaria parasite, called DHFR.

DHFR is the target of a well-established antimalarial drug, pyrimethamine; however, resistance to the drug among malaria parasites is common. The researchers showed that triclosan was able to target and act on this enzyme even in pyrimethamine-resistant parasites.

Triclosan inhibits both ENR and DHFR, the researchers say it may be possible to target the parasite at both the liver stage and the later blood stage.

"The discovery by our robot 'colleague' Eve that triclosan is effective against malaria targets offers hope that we may be able to use it to develop a new drug. We know it is a safe compound, and its ability to target two points in the malaria parasite's lifecycle means the parasite will find it difficult to evolve resistance," concluded Lead author Dr. Elizabeth Bilsland, now an assistant professor at the University of Campinas, Brazil.