Adults go on to lives of recurrent episodes of fever and debility. Worse yet, the parasites are becoming resistant to drugs of the quinine type, which have long been mainstays of malaria treatment. American scientists looked for this familiar herb in parks around Washington, D.C., repeated the findings of their Chinese colleagues, and added to the knowledge about artemisinin by determining its chemical structure and preparing related molecules. Malaria parasites which are resistant to quinine are still susceptible to artemisinin, and better yet, artemisinin can treat the most dangerous form of malaria, when the parasite enters the brain. Devising that approach, and modifying artemisinin to be longer-acting, tested chemists' skill and inspiration.
Tamoxifen is patterned on natural estrogen, but with some synthetic modification.
Artemisinin can be found right in this plant, but it's extensively purified before any further development work. About a quarter of prescription medicines today are ultimately derived from some source in nature, but are modified by chemical synthesis and certainly highly purified. Nor are the ones more directly from natural sources or models necessarily better or safer than those generated by completely synthetic means. To illustrate the blurring of natural and synthetic, although aspirin is chemically very similar to the active principle in willow bark tea, used by both the ancient Greeks and the Native Americans to treat headache and arthritis, aspirin is made from chemicals derived from petroleum. One thing we can say, though, is that, in the U.S., anything sold as having a specific medicinal effect, whether of natural or synthetic origin, must be a pure chemical entity, backed up by various required clinical studies.