Quinine. Molecular graphic of quinine, a drug used to treat malaria. Quinine (formula: C20.H24.N2.O2) is obtained from the bark of the cinchona tree (Cinchona sp.), native to South America. The atoms are here represented as spheres, and are colour- coded: carbon (yellow), hydrogen (white), nitrogen (blue) and oxygen (red). Quinine has been used to treat malaria for over 300 years. Malaria is a tropical disease caused by the presence of Plasmodium sp. protozoa in the blood. Quinine is effective at destroying the sex forms of the parasite, preventing them multiplying. Its use has been largely superceded by synthetic alternatives.