Artemisia annua

Artemisia annua, also known as Sweet Wormwood, Sweet Annie, or Chinese wormwood (Chinese: 青蒿; pinyin: qīnghāo), is a common type of wormwood that grows throughout the world. It has fern-like leaves, bright yellow flowers, and a camphor-like scent. It averages about 2 m tall and has a single stem, alternating branches, and alternating leaves which range 2.5-5cm in length. It is cross-pollinated by the wind or insects. It is a diploid organism with chromosome number, 2n=36. Sweet Wormwood was used by Chinese herbalists in ancient times to treat fever, but had fallen out of common use, to be rediscovered in 1970 when the Chinese Handbook of Prescriptions for Emergency Treatments (340 AD) was found. This pharmacopeia contained recipes for a tea from dried leaves, prescribed for fevers (not specifically malaria). In 1971, scientists demonstrated that 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. Artemisinin itself is a sesquiterpene lactone with an endoperoxide bridge and has been produced semi-synthetically as an antimalarial that is commonly used in tropical nations which can afford it, preferentially as part of a combination-cocktail with other antimalarials in order to prevent the development of parasite resistance.

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The question as to whether tea made from A. annua should be used to treat malaria is very contentious. Those against argue that artemesinin is not soluble in water and only very low concentrations are achieved that are insufficient to treatment malaria reliably.^[1][2][3] Those for argue that Artemisia annua contains a cocktail of anti-malarial substances, and insist that clinical trials be conducted to demonstrate scientifically that artemisia tea is just as effective in treating malaria as it appears to be where it is regularly used. If it is proven, then it will present itself as a cheaper alternative to commercial pharmaceuticals, and will enable health dispensaries in the Tropics to be much more self-reliant in their malaria treatment. James Duke and Mike Benge et al, Chemical and Engineering News, Letters, Vol 83, No 18, pp4-5.

The plant has also been shown to have anti-cancer properties. It is said to have the ability to be selectively toxic to breast cancer cells [Cancer Research 65:(23).Dec 1, 2005] and some form of prostate cancer, there have been exciting preclinical results against leukemia [1], and other cancer cells.

The proposed mechanism of action of artemisinin involves cleavage of endoperoxide bridges by iron producing all sorts of free radicals (hypervalent iron-oxo species, epoxides, aldehydes, and dicarbonyl compounds) which damage biological macromolecules causing the parasite oxidative stress. Malaria is caused by the Apicomplexan, Plasmodium falciparum, which largely resides in red blood cells and itself contains iron-rich heme-groups (in the from of haemozoin)^[4]. Cancer cells also tend to have higher iron concentrations than normal cells because of their rapid growth rate.

Other uses

In modern-day central China, specifically Hubei Province the stems of this wormwood are used as food in a salad-like form. The final product, literally termed "cold-mixed wormwood" is a slightly bitter salad with strong acid overtones from the spiced rice vinegar used as a marinade. It is considered a delicacy and is typically more expensive to buy than meat.

References

1. ^ Mueller MS, Runyambo, Wagner I, et al. (2004). "Randomized controlled trial of a traditional preparation of Artemisia annua L. (Annual Wormwood) in the treatment of malaria". Trans R Soc Trop Med Hyg 98: 318–21.
2. ^ Räth K, Taxis K, Walz GH, et al. (2004). "Pharmacokinetic study of artemisinin after oral intake of a traditional preparation of Artemisia annua L. (annual wormwood)". Am J Trop Med Hyg 70: 128–32.
3. ^ Jansen FH (2006). "The herbal tea approach for artemesinin as a therapy for malaria?". Trans R Soc Trop Med Hyg 100 (3): 285–6. doi:10.1016/j.trstmh.2005.08.004.
4. ^ Gary H. Posner & Paul M. O’Neil (2004). "Knowledge of the Proposed Chemical Mechanism of Action and Cytochrome P450 Metabolism of Antimalarial Trioxanes Like Artemisinin Allows Rational Design of New Antimalarial Peroxides". Acc. Chem. Res. 37: 397–404.

Novartis' malaria drug Coartem stems from this plant , a cure for fever. Mention of the plant, sweet wormwood-or Artemisia annua L. was found in a Chinese medicine book written on silk, unearthed from a tomb of the West Han Dynasty, which began around 200.B.C Chinese military scientists developed the drug from the plant in the 1970s to treat Chinese soldiers suffering from malaria in Vietnam. In the early 1990s, Novartis struck a deal with the Chinese to buy the rights to Coartem, a combination of a derivative of the plant and another antimalarial treatment, paying a few million dollars up front and royalties on future sales. (excerpt from the Wall Street Journal-November 15,2006)