Cinchona (Cinchona calisaya) Cinchona is native to Central and
South America. The use of cinchona against malaria was discovered 
by serendipity: an earthquake in Peru resulted in the falling of trees 
into the lake from which, an Indian, urged by his thirst in an attack 
of malaria drank and cured. Cinchona was named for the Spanish 
Countess Cinchon, the wife of the Viceroy of Peru who recovered 
from malaria by using the bark. The active ingredient of the bark is 
an alkaloid quinine first isolated in 1820 by the French chemists
J.B. Caventous and P.J. Pelletier. Synthetic quinine became available 
in 1944 and from these came various quinine based drugs such as 
chloroquine and hydroxychloroquine.  Apart from malaria, they are 
used to treat conditions such as  rheumatoid arthritis. Overdose of 
quinine can cause retinal artery occlusion and prolonged use of 
chloroquine and to certain extent hydroxychloroquine is associated 
with cataract and maculopathy.