Though it has been synthesized in the lab, the bark of the cinchona tree is the only known natural source of quinine. The medicinal properties of the cinchona tree were originally discovered by the Quechua Indians of Peru and Bolivia; later, the Jesuits were the first to bring the cinchona to Europe.
Quinine was the first effective treatment for malaria caused by Plasmodium falciparum, appearing in therapeutics in the 17th century. It remained the antimalarial drug of choice until the 1940s, when other drugs replaced it. Since then, many effective antimalarials have been introduced, although quinine is still used to treat the disease in certain critical situations. Quinine is available with a prescription in the United States and over-the-counter, in very small quantities, in tonic water. Quinine is also used to treat lupus and arthritis. Until recently, quinine was also a common "off-label" treatment for nocturnal leg cramps. This practice is now considered dubious by the FDA