What is "chinine"

Quinine \Qui"nine\, n. [F. (cf. Sp. quinina), fr. Sp. quina, or quinaquina, Peruvian bark, fr. Peruv. kina, quina, bark. Cf. Kinic.] (Chem.) An alkaloid extracted from the bark of several species of cinchona (esp. Cinchona Calisaya) as a bitter white crystalline substance, C20H24N2O2. Hence, by extension (Med.), any of the salts of this alkaloid, as the acetate, chloride, sulphate, etc., employed as a febrifuge or antiperiodic. Called also quinia, quinina, etc. [Written also chinine.]