Quinine side effects include deafness, low blood platelets, and an irregular heartbeat. Use can make one more prone to sunburn. While it is unclear if use during pregnancy causes harm to the baby, use to treat malaria during pregnancy is still recommended. Quinine is an alkaloid, a naturally occurring chemical compound. How it works as a medicine is not entirely clear. Quinine was first isolated in 1820 from the bark of a cinchona tree. Bark extracts have been used to treat malaria since at least 1632. It is on the World Health Organization's List of Essential Medicines, the most effective and
Cinchona "plea for the correct spelling of the genus "Chinchona"". A Spanish physician, Juan Fragoso wrote of bark powder from an unknown tree in 1600 that was used for treating various ills. Nicolas Monardes also wrote of a New World bark powder used in Spain in 1574. Both identify the sources as trees that do not bear fruit and having heart-shaped leaves and it has been suggested that these references could be to "Cinchona" species. The name Quina-Quina or Quinquina was suggested as an old name for Cinchona used in Europe and based on the native name used by the Quechua