Artemisinin is an antimalarial drug derived from the sweet wormwood. Artemisinin is a sesquiterpene lactone (a compound composed of three isoprene units bound to cyclic organic esters) distilled from the dried leaves or flower clusters of the sweet wormwood. The antifebrile (fever-reducing) properties of the plant were first discovered in the 4th century AD by Chinese doctors, who called the plant Artemisia annua and recommended a natural medicine in the form of artemisia annua tea. In the centuries that followed, the drug was commonly used to treat hemorrhoids and malaria. The active agent artemisinin was isolated from plants in the 1970s; The compound is widely known as artemisinin. Today, several artemisinin derivatives, including artesunate and artemether, are used to treat malaria.
Artemisinin is effective against all the malaria-causing protozoans of the plasmodium genus. The drug is particularly suitable for the treatment of infections with the chloroquine-resistant parasite and multidrug-resistant plasmodium falciparum, the most deadly of malaria protozoans. Artemisinin targets plasmodium at the schizozoite stage of development. The schistozoites mature from the cospore -- a parasitic form transmitted to humans from anopheles mosquito saliva -- and contain insoluble iron called hemozoin. Hemozoin is formed in schizozoites because they feed on hemoglobin in the cytoplasm of human red blood cells. Artemisinin contains a peroxide group that reacts with heme, a reaction that is suspected of causing the production of free radicals that attack parasite proteins, killing the organism.
Artemisinin can be given orally, intramuscular or as a suppository. The drug reached peak plasma levels within hours of administration and acted quickly, significantly reducing the burden of the malaria parasite in the first few days of treatment. Artesunate is unique among artemisinin-derived drugs because it can be administered intravenously, allowing the drug to take immediate effect. For this reason, artesunate is used to treat cerebral malaria, an acute disease characterized by the rapid spread of the parasite to the brain and death within 72 hours if left untreated. Artemisinin appears to have few side effects in humans. However, animal studies have shown that high doses can cause neurotoxic symptoms, including respiratory depression and gait instability. These symptoms have been linked to brain stem degeneration, but it is unclear whether humans experience similar neurodegenerative effects at high doses.