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A compound derived from tree bark has potential as a preventative treatment for malaria, according to a study published in PLoS Medicine.

The treatment targets the early stages of malaria infection. This would make it more difficult for the parasite to develop the kind of drug resistance that hampers conventional malaria treatment programmes. 

Scientists isolated a new molecule, tazopsine, from bark collected in Madagascar's eastern rain forest. They found that N-cyclopentyl-tazopsine, a less-toxic compound derived from the molecule, was effective against early, liver-stage malaria parasites in animal tests.

However, the compound is ineffective once infection has reached the red blood cells.

Tazopsine comes from the stem bark of the plant Strychnopsis thouarsii. It is the sole ingredient in a traditional tea used as a treatment for malaria infection. The authors of the study hope that variants of tazopsine-related molecules can be tested to find one of low toxicity, suitable for clinical trials.

A resurgence of malaria since the 1980s, combined with a shortage of conventional drugs, has forced many Madagascans to rely on medicines from more than 200 plants to fight the disease. This has triggered scientific interest, as Madagascar's long isolation from neighbouring countries has resulted in a unique mix of plants and animals.

There is currently a shortage of treatments which target the malaria parasite after it migrates to the liver and before it reproduces into the bloodstream and infects red blood cells. (See Malaria hijacks liver cells to avoid immune system)

The lead author of the study, Dominique Mazier, of the Pierre and Marie Curie University in Paris, France, said if a drug is eventually developed to specifically target the parasite in the liver, this could prove significant in combating drug resistance. "The chances for a resistant parasite to appear are minimal," she said.

A member of the research team, Philippe Rasoanaivo of the Malagasy Institute of Applied Research (IMRA) in Antananarivo, Madagascar, told SciDev.Net that tests on chimpanzees were due to begin this year in Gabon, while tests on rhesus monkeys would be done in Thailand before the end of 2007.

Reference: PLoS Med doi:10.1371/journal.pmed.0030513 (2006)

Link to full paper in PloS Medicine