Artemisia annua, also known as sweet wormwood, sweet annie, sweet sagewort or annual wormwood (Chinese: 青蒿; pinyin: qīnghāo), is a common type of wormwood native to temperate Asia, but naturalized throughout the world.
It has fern-like leaves, bright yellow flowers, and a camphor-like scent. Its height averages about 2 m, and the plant has a single stem, alternating branches, and alternating leaves which range from 2.5–5 cm in length. It is cross-pollinated by wind or insects. It is a diploid plant with chromosome number 2n=18.
In 1971, scientists demonstrated the plant extracts had antimalarial activity in primate models, and in 1972, the active ingredient, artemisinin (formerly referred to as arteannuin), was isolated and its chemical structure described. Artemisinin may be extracted using a low boiling point solvent, such as diethylether, and is found in the glandular trichomes of the leaves, stems, and inflorescences, and it is concentrated in the upper portions of plant within new growth.
Research to develop antimalarial drugs led to the discovery artemisinin, which is extracted from Artemisia annua, a herb traditionally used as a fever treatment. While most TCM herbs are boiled at high temperature that can damage the active ingredient in Artemisia annua, one traditional source says that this herb is to be steeped in cold water; knowing this, scientists found that a better extract was obtained by using a low-temperature ether-based extraction method, and by adding detoxification and purification processes, they could create a drug with sufficient active ingredient to be effective.
Artemisinin is a sesquiterpene lactone with an endoperoxide bridge and has been produced semisynthetically as an antimalarial drug. The efficacy of tea made from A. annua in the treatment of malaria is contentious. According to some authors, artemesinin is not soluble in water and the concentrations in these infusions are considered insufficient to treat malaria. In 2004, the Ethiopian Ministry of Health changed Ethiopia's first line antimalaria drug from sulfadoxine/pyrimethamine (Fansidar), which has an average 36% treatment failure rate, to artemether/lumefantrine (Coartem), a drug therapy containing artemesinin which is 100% effective when used correctly, despite a worldwide shortage at the time of the needed derivative from A. annua. A 2012 review said that artemisinin-based remedies are the most effective drugs for the treatment of malaria. A 2013 review suggested that although Artemisia annua may not cause hepatotoxicity, haematotoxicity, or hyperlipidemia, it should be used cautiously during pregnancy due to a potential risk of embryotoxicity at a high dose.
Despite global efforts in combating malaria, it remains a large burden for the population, particularly in tropical and subtropical regions. Although WHO recommends artemisinin-based remedies for treating uncomplicated malaria, artemisinin resistance can no longer be ignored. The causes that affected the emergence of artemisinin resistance include, for example, the use of artemisinin-based remedies. Encouraging herbal alternatives are in the pipeline, but the only indelible solution for the eradication of malaria would be for the creation of an effective vaccination. Emergence of artemisinin resistance has been identified in Cambodia and the border of Thailand. It will likely spread to other endemic areas across the world in the impending future. As of 2013, it seems that the pathogenic agent of malaria is slowly becoming resistant to artemisinin-based drugs.
The proposed mechanism of action of artemisinin involves cleavage of endoperoxide bridges by iron, producing free radicals (hypervalent iron-oxo species, epoxides, aldehydes, and dicarbonyl compounds) which damage biological macromolecules causing oxidative stress in the cells of the parasite. Malaria is caused by apicomplexans, primarily Plasmodium falciparum, which largely reside in red blood cells and itself contains iron-rich heme-groups (in the form of hemozoin).
A University of Washington, Seattle study claims to have had success using Artemisinin in attacking cancer cells when combined with iron. Artemisinin reacts with iron to form free radicals that kill cells. Since cancer cells uptake relatively large amount of iron than normal cells, they are more susceptible to the toxic effect of artemisinin. They covalently attached artemisinin to the iron-carrying plasma glycoprotein transferrin. The study found that holotransferrin-tagged artemisinin, when compared with artemisinin, was very potent and selective in killing cancer cells. Thus, this 'tagged-compound' could potentially be developed into an effective chemotherapeutic agent for cancer treatment. 
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|Wikimedia Commons has media related to Artemisia annua.|
- Distribution of Artemisinin in Artemisia annua
- Project to improve artemesinin yield at the University of York (UK)
- Data sheet about Artemisia annua from Purdue University