text: Other chemicals Alongside the alkaloids, many cinchona barks contain cinchotannic acid, a particular tannin, which by oxidation rapidly yields a dark-coloured phlobaphene called red cinchonic, cinchono-fulvic acid, or cinchona red.
  In 1934, efforts to make malaria drugs cheap and effective for use across countries led to the development of a standard called "totaquina" proposed by the Malaria Commission of the League of Nations. Totaquina required a minimum of 70% crystallizable alkaloids, of which at least 15% was to be quinine with not more than 20% amorphous alkaloids.
  Species
  There are at least 24 species of Cinchona recognized by botanists. There are likely several unnamed species and many intermediate forms that have arisen due to the plants' tendency to hybridize.
  Cinchona anderssonii Maldonado
  Cinchona antioquiae L.Andersson
  Cinchona asperifolia Wedd.
  Cinchona barbacoensis H.Karst.
  Cinchona calisaya Wedd.
  Cinchona capuli L.Andersson
  Cinchona fruticosa L.Andersson
  Cinchona glandulifera Ruiz & Pav.
  Cinchona hirsuta Ruiz & Pav.
  Cinchona krauseana L.Andersson
  Cinchona lancifolia Mutis
  Cinchona lucumifolia Pav. ex Lindl.
  Cinchona macrocalyx Pav. ex DC.
  Cinchona micrantha Ruiz & Pav.
  Cinchona mutisii Lamb.
  Cinchona nitida Ruiz & Pav.
  Cinchona officinalis L.
  Cinchona parabolica Pav. in J.E.Howard
  Cinchona pitayensis (Wedd.) Wedd.
  Cinchona pubescens Vahl
  Cinchona pyrifolia L.Andersson
  Cinchona rugosa Pav. in J.E.Howard
  Cinchona scrobiculata Humb. & Bonpl.
  Cinchona villosa Pav. ex Lindl.