Cinchona has been historically sought after for its medicinal value, as the bark of several species yields quinine and other alkaloids. These were the only effective treatments against malaria during the height of European colonialism, which made them of great economic and political importance. Trees in the genus are also known as fever trees because of their anti-malarial properties.
The artificial synthesis of quinine in 1944, an increase in resistant forms of malaria, and the emergence of alternate therapies eventually ended large-scale economic interest in cinchona cultivation. Cinchona alkaloids show promise in treating falciparum malaria, which has evolved resistance to synthetic drugs. Cinchona plants continue to be revered for their historical legacy; the national tree of Peru is in the genus Cinchona.
Etymology and common names
The bark of trees in this genus is the source of a variety of alkaloids, the most familiar of which is quinine, an antipyretic (antifever) agent especially useful in treating malaria. For a while the extraction of a mixture of alkaloids from the cinchona bark, known in India as the cinchona febrifuge, was used. The alkaloid mixture or its sulphated form mixed in alcohol and sold quinetum was however very bitter and caused nausea, among other side effects.
Cinchona alkaloids include:
- cinchonine and cinchonidine (stereoisomerswith R1 = vinyl, R2 = hydrogen)
- quinine and quinidine (stereoisomers with R1 = vinyl, R2 = methoxy)
- dihydroquinine and dihydroquinidine(stereoisomers with R1 = ethyl, R2 = methoxy)
They find use in organic chemistry as organocatalysts in asymmetric synthesis.
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.