Artemisinin antimalaria drug molecule. Computer illustration showing the structure of a molecule of the antimalaria drug artemisinin. Atoms are represented as spheres and are colour-coded: carbon (large, white), hydrogen (small, white) and oxygen (red). This drug is extracted from the leaves of the wormwood plant (Artemisia annua) and has been used in Chinese herbal medicine for over 2000 years. Its antimalarial action was discovered in the 1970s. Artemisinin is effective against populations of the malaria parasite (Plasmodium sp.) that have become resistant to other drugs. It is most often used in combination with other drugs, at treatment known as artemisinin-based combination therapy (ACT). However, an increase in prescribing artemisinin on its own is leading to an increase in resistance to the drug. Malaria causes over 1 million deaths annually.