Scientists have discovered a second new compound that could eventually be developed into a medicine to help eradicate malaria.
Mefloquine was one of around 250,000 chemical compounds tested for malaria-killing activity in the 1960s by the United States military who needed to protect troops from malaria in the tropics.
Despite tests which rapidly test for malaria being around for several years, overtreatment of malarial drugs still takes place in Africa.
The drug partly responsible for more than halving the rate of malaria over the last 30 years and which won this year's Nobel Prize for Physiology or Medicine has a long history of use.
Tu Youyou sifted through 2,000 ancient herbal remedies to develop a drug that now treats hundreds of millions of people a year.