Source : Webster's Revised Unabridged Dictionary (1913)

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}.]

Source : WordNet®

quinine
     n : a bitter alkaloid extracted from chinchona bark; used in
         malaria therapy