The first and last time a natural product gained wide acceptance as a treatment for malaria was in the 16th century. It was then that the therapeutic action of the bark of the cinchona tree was disclosed by the natives of Peru to Jesuit missionaries, who, in turn, brought the word of its utility to Europe. Quinine, the alkaloid isolated in 1834 from cinchona bark by the French chemist Pelletier, became the main treatment for malaria until the 1930's when synthetic antimalarials were developed. Plants, in addition to cinchona, that have been used against fevers and malaria include Dichroa febrifuga, which grows in China. However, its alkaloid, febrifugine, was found to be too toxic for use in humans. Recently, again in China, a naturally derived antimalarial compound has been investigated that may, eventually, rival quinine in importance. In view of the number of chloroquine-resistant strains of Plasmodium falciparum emerging in Asia, South and Central America, and Africa, the need for new antimalarials cannot be overemphasized (1).
In 1967 the government of the People's Republic of China embarked on a systematic examination of indigenous plants used in traditional remedies as sources of drugs (2). One such plant, a pervasive weed with a long history of use, is known as qing hao (3) (Artemisia annua L., sweet wormwood, annual wormwood). Its earliest mention occurs in the Recipes for 52 Kinds of Diseases found in the Mawangdui Han dynasty tomb dating from 168 B.C. In that work, the herb is recommended for use in hemorrhoids. This plant is mentioned further in the Zhou Hou Bei Ji Fang (Handbook of Prescriptions for Emergency Treatments) written in 340 A.D. The author, Ge Hong, advised that to reduce fevers one should soak one handful of qing hao in 1 sheng (about 1 liter) of water, strain the liquor, and drink it all (4). Later, Li Shizhen, the famous herbalist, whose death 390 years ago was recently commemorated in China (5), wrote in his Ben Cao Gang Mu (Compendium of Materia Medica) of 1596, that chills and fever of malaria can be combated by qing hao preparations (6, 7). A decoction of A. annua and Carapax trionycis was suggested in the Wenbing Tiaobian in 1798 as a treatment for malaria (7).
Attempts to confirm the antipyretic and antimalarial activity of a hot-water extract of A. annua were disappointing. In 1971, it occurred to an investigator that low-temperature extraction of the plant, that is, with ethyl ether, should be tried (2). Crude ether extracts produced encouraging results in mice infected with the malaria parasite Plasmodium berghei. Further refinement of the antimalarial fractions led in 1972 to the isolation of a plant constituent that had not been reported previously in the chemical literature. The Chinese named the crystalline compound qinghaosu (8) [QHS, qing hau sau (9), arteannuin (6)], meaning "active principle of qing hao," and the more Western sounding name, "artemisinine." Because the material is a terpene, rather than an alkaloid or amine, which the "ine" suffix suggests, the...
This is a preview. Get the full text through your school or public library.