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In 1967, Chinese scientists began to search for new malaria treatments by systematically testing plants used in traditional Chinese medicine. By 1972, they had isolated and chemically characterised artemisinin, from the Chinese medicinal plant, Artemisia annua . Artemisinin and its derivatives* produce rapid clearance of malaria parasites from the blood. They kill all malaria species and all stages of the parasite’s life cycle. They are safe, well-tolerated and rapidly eliminated from the human body. Artemisinin and its derivatives should be taken in conjunction with a partner drug as an Artemisinin Combination Therapy (ACTs -see fact sheet on ACTs).
The artemisinin molecule contains an unusual trioxane ring, which is thought to be the source of anti-malarial activity. However, the detailed mechanism by which the malarial parasite is killed is still the subject of much scientific debate. Because there is growing parasite resistance to established anti-malarial drugs such as chloroquine, the artemisinin family of drugs is increasingly being relied on as the mainstay of malaria treatment. Artemisinin is also showing promise as a possible anti-cancer compound, and has been proposed for use in the treatment of schistosomiasis, another important parasitic disease of the tropics.
(*Artemisinin for clinical use is usually derivatised to improve its stability and solubility. The most common derivatives are dihydroartemisinin, artemether, arteether, artesunate and artelinate.)
Artemisia annua is currently the sole source of artemisinin and plant cultivation will continue to be essential to supplies for the foreseeable future. However, alternative strategies are being developed as part of the solution to artemisinin cost and security of supply. For example;
Multiple sources of artemisinin are required to satisfy projected global demand for ACTs and reduce costs. The CNAP Artemisia Research Project is collaborating with the above projects for maximum impact on ACT production and to ensure that the new technologies do not enter substandard drug or monotherapy supply chains.
The malaria parasite has developed resistance to all classes of anti-malarial drug except artemisinin and this has caused serious problems for malaria control. However there is also some evidence that parasites resistant to artemisinin may have evolved and control measures to contain the emerging resistance are under way.
The WHO has called for an immediate halt to the marketing and sale of single drug oral* artemisinin monotherapies, which are likely to hasten the development of resistance.
(*Injectable or suppository formulations of artemisinin monotherapy are still recommended for the treatment of severe malaria.)
Department of Biology