Quinine was used as a treatment for malaria, at least until synthetic drugs were available. Also known as cinchona, quinine has been used as an effective antidote to malaria for hundreds of years by the indigenous people of Peru. Malaria is transmitted by mosquito and can cause an enlarged liver and spleen, fever, anemia and jaundice. Death can occur from victims becoming so weak they are unable to feed themselves, anemia, or clogged blood vessels. The use of synthetic drugs to treat malaria has produced mosquitoes that are now resistant to treatment. A return to quinine to combat malaria is growing worldwide, as mosquitoes do not have a resistance to it.
Source: Australian National University