Artemisinin and its derivatives are a group of drugs that possess the most rapid action of all current drugs against Plasmodium falciparum malaria. Treatments containing an artemisinin derivative (artemisinin-combination therapies, ACTs) are now standard treatment worldwide for P. falciparum malaria. Artemisinin is isolated from the plant Artemisia annua, sweet wormwood, a herb employed in Chinese traditional medicine. It can now also be produced using genetically engineered yeast. Chemically, artemisinin is a sesquiterpene lactone containing an unusual peroxide bridge. This peroxide is believed to be responsible for the drug's mechanism of action. Few other natural compounds with such a peroxide bridge are known. The drug is also increasingly being used in Plasmodium vivax malaria, as well as being a topic of research in cancer treatment.