Quinine:The originalantimalarialagent,quininetook its name from the Peruvian Indian word "kina" meaning "bark of the tree" referring to the cinchona tree. From this tree, quinine was first obtained. The Peruvian Indians called it "the fever tree."
奎宁,large and complexmolecule, is the most importantalkaloidfoundincinchona bark. Until World War I, it was the only effective treatment for malaria. In fact, quinine was the first chemical compound to be successfully used to treat an infectiousdisease.
Quinine was isolated in crystalline form in 1820 by J.B. Caventou and P.J. Pelletier. In one of the classical achievements of syntheticorganicchemistry, R.B. Woodward and W. Doering first made synthetic quinine in 1944.
Quinine acts by interfering with the growth andreproductionof thePlasmodium, the malarialparasitethat lives within the victim's red blood cells. Quinine causes the parasites to disappear from thebloodand the symptoms of the disease are thereby alleviated. However, when quinine treatment ends, many patientsrelapse. They suffer another attack of malaria due to the failure of quinine to kill the malarial parasites in cells of the body other than the red blood cells. These parasites persist and, after a time, they reinvade the red blood cells and precipitate the relapse.
Since quinine does not permanentlycuremalaria, better drugs were sought. A number were discovered that replaced quinine during and after World War II. Some of these drugs (such as chloroquine and chloroguanide) are more effective than quinine in suppressing the growth of the blood forms of the malarial parasite. Others (such asprimaquineand pyrimethamine) act upon both the blood andtissuephases of the parasite, producing a complete cure and preventing a relapse.
Quinine has been used outside of malaria as aremedyfor fever and pain and to treat and prevent leg cramps. Prolonged administration of quinine may produce toxic symptoms such asdeafness, disturbances in vision,skinrashes, and digestive upsets.
