Artemisinin: An Ancient Remedy for Modern Malaria

Sometimes old remedies can be the best, particularly when they've been around for a couple thousand years. Take sweet wormwood, for example. Archaeological findings indicate that the Chinese were using wormwood to treat malaria more than 2,000 years ago. The weed—Artemisia annua or qing ho in Chinese—is even mentioned in the Recipes for 52 Kinds of Diseases, an early medical text found in a tomb dating from 168 BC. But its curative powers were not put to a rigorous test until 1967, when the government of the People's Republic of China began to examine systematically indigenous plants used in traditional remedies as potential sources of drugs.

The initial studies were disappointing. Extracts prepared by soaking sweet wormwood—a relative of tarragon—in hot water did not show the anticipated fever-reducing and antimalarial activities. Then in 1971 an investigator decided to try preparing a low-temperature extract of the plant with an organic solvent. The results looked encouraging. Crude extracts appeared to kill Plasmodium in mice that had been infected with the parasite. One year later, researchers had isolated a plant constituent never before described. The crystalline compound was given two names: qinghaosu and the more Western-sounding artemisinin. Scientists have since synthesized a series of qinghaosu derivatives that appear to be more potent that artemisinin itself. These drugs have not been generally available in many countries but have been used extensively for the treatment of drug-resistant falciparum malaria in China and Southeast Asia.

In a test tube at least, artemisinin kills P. falciparum almost as effectively as chloroquine, one of the leading antimalarial medications. It appears that artemisinin is taken up by Plasmodium and chemically cleaved, generating a free radical intermediate that then poisons the malaria parasite by damaging or destroying one or more of its essential proteins. What makes the rediscovery of artemisinin so exciting is that thus far no one has reported the emergence of drug-resistant Plasmodium strains.