Artemisia annua

Artemisia annua belongs to the plant family of Asteraceae and is an annual short-day plant. Its stem is erect and brownish or violet-brown. The plant itself is hairless and naturally grows from 30 to 100 cm tall, although in cultivation plants can reach a height of 200 cm. The leaves of A. annua have a length of 3–5 cm and are divided by deep cuts into two or three small leaflets. The intensive aromatic scent of the leaves is characteristic.{{cite web|title = Artemisia annua (sweet wormwood)|url = http://www.kew.org/science-conservation/plants-fungi/artemisia-annua-sweet-wormwood|publisher = Royal Botanic Gardens|access-date = November 25, 2015|archive-url = https://web.archive.org/web/20151006104942/http://www.kew.org/science-conservation/plants-fungi/artemisia-annua-sweet-wormwood|archive-date = October 6, 2015|url-status = dead}} The artemisinin content in dried leaves is in between 0% and 1.5%.{{cite book|publisher = World Health Organization|title = WHO monograph on good agricultural and collection practices (GACP) for Artemisia annua L.|date = 2006|url= https://www.who.int/medicines/publications/traditional/ArtemisiaMonograph.pdf}} New hybrids of Artemisia annua developed in Switzerland can reach a leaf artemisinin content of up to 2%. Also, four new genotypes developed by a collaboration between the USDA and Purdue University with 2% leaf artemisinin were recently released for researchers involved in the production of artemisinin.{{Cite journal |last1=Wetzstein |first1=Hazel Y. |last2=Janick |first2=Jules |last3=Ferreira |first3=Jorge F. S. |date=2019-11-01 |title=Germplasm Release of Four High-artemisinin Clones of Artemisia annua L. |url=https://journals.ashs.org/hortsci/view/journals/hortsci/54/11/article-p2081.xml |journal=HortScience |language=en-US |volume=54 |issue=11 |pages=2081–2082 |doi=10.21273/HORTSCI14385-19 |issn=0018-5345|doi-access=free }} The small flowers have a diameter of 2–2.5 mm and are arranged in loose panicles. Their color is greenish-yellow. The seeds are brown achenes with a diameter of only 0.6–0.8 mm. Their thousand-kernel weight (TKW) averages around 0.03 g (in comparison, wheat has a TKW of approximately 45 g).{{cite web|title = Using 1,000 Kernel Weight for Calculating Seeding Rates and Harvest Losses|url = http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex81|website = www1.agric.gov.ab.ca|date = 1993-09-01|access-date = 2015-11-15|first = Government of Alberta, Alberta Agriculture and|last=Forestry}}

File:Artemisia annua.jpg

Image:Artemisiaannua.jpg

The growing period of Artemisia annua from seeding through to harvest is 190–240 days, depending on the climate and altitude of the production area. The plant is harvested at the beginning of flowering when the artemisinin content is highest. Dry leaf yields of Artemisia annua plantations vary between 0.5 and 3 tonnes per hectare.{{cite journal|last1 = Simonnet|first1 = X.|last2 = Quennoz|first2 = M.|last3 = Carlen|first3 = C.|title = New Artemisia annua hybrids with high artemisinin content|journal = XXVII International Horticultural Congress-IHC2006: International Symposium on Asian Plants with Unique Horticultural 769|date = 2006|pages = 371–373}}

In terms of the climate A. annua prefers sunny and warm conditions. Its optimal growth temperature lies between 20 and 25 °C. Annual temperature sums of 3500–5000 °C (sum of temperatures higher than 10 °C over one year) are required to guarantee a proper maturing. The rainfall during the growing season should not be less than 600 mm (annual rainfall higher than 1150 mm). Especially the seedlings of A. annua. are susceptible to drought or water logging. The mature plants on the other hand are quite resistant to those climate conditions. Nevertheless, the preferred soil conditions for A. annua are light soils with deep topsoils and good drainage properties. But it is reported, that the plant is adaptable to different soil types. Paired with the relatively low demand on the environment Artemisia annua can have characteristics of a neophytic plant.{{cite journal|last1 = Müller|first1 = Meike|last2 = Brandes|first2 = Dietmar|title = Growth and development of Artemisia annua L. on different soil types|journal = Verhandlungen-Gesellschaft für Ökologie|date = 1997|volume = 27|pages = 453–460}}

A. annua is best sown in rows to facilitate the removal of weeds, which has to be done mechanically or manually because herbicides are typically not used. It is recommended to sow 1.4 – 2 seeds per square meter. The fertilizer requirements are at a low level. Potassium should be used as base fertilizer. It is taken up by the plant during the whole growing season. Nitrogen is required during early branching stages, an amount of approximately 70 kg N/ha is sufficient for the plant.{{cite journal|last1 = Simon|first1 = James E|title = Artemisia annua L.: A promising aromatic and medicinal|journal = Advances in New Crops|date = 1990|pages = 522–526|display-authors=etal}} Phosphate on the other hand is required during the blooming stages. Phosphate fertilization can lead to a higher artemisinin content in the leaves.{{cite journal|last1 = Kapoor|first1 = Rupam|last2 = Chaudhary|first2 = Vidhi|last3 = Bhatnagar|first3 = AK|title = Effects of arbuscular mycorrhiza and phosphorus application on artemisinin concentration in Artemisia annua L|journal = Mycorrhiza|date = 2007|volume = 17|issue = 7|pages = 581–587|pmid = 17578608|doi=10.1007/s00572-007-0135-4|s2cid = 13498398}} The application of salicylic acid to the leaves shortly before harvesting the plant also can raise its artemisinin content.{{cite journal|last1 = Pu|first1 = Gao-Bin |display-authors=etal |title = Salicylic acid activates artemisinin biosynthesis in Artemisia annua L|journal = Plant Cell Reports|date = 2009|volume = 28|issue = 7|pages = 1127–1135|pmid = 19521701|doi=10.1007/s00299-009-0713-3|s2cid = 29237295 }} Besides few viral diseases, Artemisia a. has no major diseases that need to be controlled.

The harvest of the plant is best done when plants reach peak artemisinin, which may be in the state of flower budding, for early-flowering cultivars. However, for late flowering cultivars that were reported to reach peak artemisinin in early September in the United States, the harvest will happen about a month before the flowering stage when plants produce more artemisinin in leaves. This peak artemisinin in early September was observed for Brazilian, Chinese, and Swiss clones in West Virginia.{{Cite journal |last1=Ferreira |first1=Jorge F. S. |last2=Benedito |first2=Vagner A. |last3=Sandhu |first3=Devinder |last4=Marchese |first4=José A. |last5=Liu |first5=Shuoqian |date=2018-08-13 |title=Seasonal and Differential Sesquiterpene Accumulation in Artemisia annua Suggest Selection Based on Both Artemisinin and Dihydroartemisinic Acid may Increase Artemisinin in planta |journal=Frontiers in Plant Science |volume=9 |doi=10.3389/fpls.2018.01096 |doi-access=free |issn=1664-462X |pmc=6102481 |pmid=30154807}} Drying the plants before extraction will significantly increase artemisinin as dihydroartemisinic acid and artemisinic acid seem to be converted into artemisinin.{{Cite journal |last1=Ferreira |first1=Jorge F. S. |last2=Luthria |first2=Devanand L. |date=2010-02-10 |title=Drying Affects Artemisinin, Dihydroartemisinic Acid, Artemisinic Acid, and the Antioxidant Capacity of Artemisia annua L. Leaves |url=https://pubs.acs.org/doi/10.1021/jf903222j |journal=Journal of Agricultural and Food Chemistry |language=en |volume=58 |issue=3 |pages=1691–1698 |doi=10.1021/jf903222j |pmid=20050663 |issn=0021-8561}} The whole plant is harvested and cut into branches which are dried in the sun or an oven. Some report that drying artemisia plants at 45 °C for 24h increased artemisinin and maintained leaf antioxidant capacity.{{Cite journal |last1=Ferreira |first1=Jorge F. S. |last2=Luthria |first2=Devanand L. |date=2010-02-10 |title=Drying Affects Artemisinin, Dihydroartemisinic Acid, Artemisinic Acid, and the Antioxidant Capacity of Artemisia annua L. Leaves |url=https://pubs.acs.org/doi/10.1021/jf903222j |journal=Journal of Agricultural and Food Chemistry |language=en |volume=58 |issue=3 |pages=1691–1698 |doi=10.1021/jf903222j |pmid=20050663 |issn=0021-8561}} The dry branches are shaken or beaten to separate the leaves from the stem. The leaves are then packed into fabric bags and shipped for further processing. The optimum storage conditions are either 20 °C with 85% relative humidity (RH) or 30 °C with 30–40% RH.

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, is found in the glandular trichomes of the leaves, stems, and inflorescences, and is concentrated in the upper portions of plants within new growth.{{cite journal |vauthors=Duke SO, Paul RN |title=Development and Fine Structure of the Glandular Trichomes of Artemisia annua L. |journal=Int. J. Plant Sci. |volume=154 |issue=1 |pages=107–18 |year=1993 |doi=10.1086/297096 |jstor=2995610|s2cid=86584892 |url=https://zenodo.org/record/1235684 }}
{{cite journal |vauthors=Ferreira JF, Janick J |title=Floral Morphology of Artemisia annua with Special Reference to Trichomes |journal=Int. J. Plant Sci. |volume=156 |issue=6 |page=807 |year=1995 |doi=10.1086/297304 |s2cid=84594350 }}

The first isolation of artemisinin from the herb occurred from a military project known as Project 523, following the study of traditional medicine pharmacopoeias performed by Tu Youyou and other researchers within the project.{{cite web|url=https://www.theguardian.com/science/2015/oct/05/youyou-tu-how-maos-challenge-to-malaria-pioneer-led-to-nobel-prize|title=Tu Youyou: how Mao's challenge to malaria pioneer led to the Nobel prize|author=Tom Phillips|date=October 6, 2015|work=The Guardian}} A. annua contains diverse phytochemicals, including polyphenols such as coumarins, flavones, flavonols, and phenolic acids which have unknown biological properties in vivo.{{Cite journal|title = Flavonoids from Artemisia annua L. as antioxidants and their potential synergism with artemisinin against malaria and cancer|journal = Molecules|date = 2010-04-29|pages = 3135–3170|volume = 15|issue = 5|doi = 10.3390/molecules15053135|pmid = 20657468|pmc = 6263261|first1 = Jorge F. S.|last1 = Ferreira|first2 = Devanand L.|last2 = Luthria|first3 = Tomikazu|last3 = Sasaki|first4 = Arne|last4 = Heyerick|doi-access = free}}{{cite journal | last1=Nahar | first1=Lutfun | last2=Guo | first2=Mingquan | last3=Sarker | first3=Satyajit D. | title=A review on the latest advances in extraction and analysis of artemisinin (Review) | journal=Phytochemical Analysis | volume=31 | issue=1 | year=2019 | issn=0958-0344 | pmid=31370102 | doi=10.1002/pca.2873 | pages=5–14| s2cid=199382005 | url=http://researchonline.ljmu.ac.uk/id/eprint/10865/3/A%20review%20on%20the%20latest%20advances%20in%20extraction%20and%20analysis%20of%20artemisinin.pdf }} Other phytochemicals include 38 sesquiterpenes. Dihydroartemisinin is the active metabolite of artemisinin, and artesunate is a water-soluble derivative of artemisinin.

Research to develop antimalarial drugs led to the discovery of artemisinin in the 1970s by the Chinese scientist Tu Youyou, who shared the 2015 Nobel Prize in Physiology or Medicine.{{cite journal|doi=10.1016/j.cell.2011.08.024|title=Artemisinin: Discovery from the Chinese herbal garden|year=2011|last1=Miller|first1=Louis H.|last2=Su|first2=Xinzhuan|journal=Cell|volume=146|issue=6|pages=855–8|pmid=21907397|pmc=3414217}}{{cite journal|doi=10.1038/448106a|title=Hard to swallow|year=2007|journal=Nature|volume=448|issue=7150|pages=105–6|pmid=17625521|bibcode=2007Natur.448S.105.|doi-access=free}} An improved extract was obtained by using a low-temperature ether-based extraction method, further showing the artemisinin derivative artemether to be an effective antimalarial drug.

Artemisinin is a sesquiterpene lactone with an endoperoxide bridge and has been produced as an antimalarial drug. The efficacy of tea, made with either water or urine and A. annua, for the treatment of malaria is dubious, and is discouraged by the World Health Organization (WHO).{{cite journal| author=van der Kooy F, Sullivan SE| title=The complexity of medicinal plants: the traditional Artemisia annua formulation, current status and future perspectives. | journal=J Ethnopharmacol | year= 2013 | volume= 150 | issue= 1 | pages= 1–13 | pmid=23973523 | doi=10.1016/j.jep.2013.08.021 |type=Review }} Research has found that artemisinin is not soluble in water and the concentrations in these infusions are considered insufficient to treat malaria.{{cite journal | title=Randomized controlled trial of a traditional preparation of Artemisia annua L. (Annual Wormwood) in the treatment of malaria | journal=Trans R Soc Trop Med Hyg | year=2004 | volume=98 | pages=318–21 | doi=10.1016/j.trstmh.2003.09.001 | pmid=15109558 | issue=5 | last1=Mueller | first1=Markus S | last2=Runyambo | first2=Nyabuhanga | last3=Wagner | first3=Irmela | last4=Borrmann | first4=Steffen | last5=Dietz | first5=Klaus | last6=Heide | first6=Lutz}}{{cite journal | title=Pharmacokinetic study of artemisinin after oral intake of a traditional preparation of Artemisia annua L. (annual wormwood) | date=1 February 2004| journal=Am J Trop Med Hyg | volume=70 | pages=128–32 | pmid=14993622 | issue=2 | last1=Räth | first1=K | last2=Taxis | first2=K | last3=Walz | first3=G | last4=Gleiter | first4=CH | last5=Li | first5=SM | last6=Heide | first6=L | doi=10.4269/ajtmh.2004.70.128 | doi-access=free }}{{cite journal | author=Jansen FH | title=The herbal tea approach for artemesinin as a therapy for malaria? | journal=Trans R Soc Trop Med Hyg | year=2006 | volume=100 | issue=3 | pages=285–6 | doi=10.1016/j.trstmh.2005.08.004 | pmid=16274712 }} A 2012 review stated that artemisinin-based remedies are the most effective drugs for the treatment of malaria.{{cite journal| pmid=22855752| year=2012| last1=Fairhurst| first1=RM| last2=Nayyar| first2=GM| last3=Breman| first3=JG| last4=Hallett| first4=R| last5=Vennerstrom| first5=JL| last6=Duong| first6=S| last7=Ringwald| first7=P| last8=Wellems| first8=TE| last9=Plowe| first9=CV| last10=Dondorp| first10=AM| title=Artemisinin-resistant malaria: Research challenges, opportunities, and public health implications| volume=87| issue=2| pages=231–41| doi=10.4269/ajtmh.2012.12-0025| pmc=3414557| journal=The American Journal of Tropical Medicine and Hygiene}} A 2013 review suggested that although Artemisia annua may not cause hepatotoxicity, haematotoxicity, or hyperlipidemia, it should be used cautiously during pregnancy owing to a potential risk of embryotoxicity at a high dose.{{cite journal | pmid=22736625 | year=2013 | last1=Abolaji | first1=AO | last2=Eteng | first2=MU | last3=Ebong | first3=PE | last4=Brisibe | first4=EA | last5=Dar | first5=A | last6=Kabir | first6=N | last7=Choudhary | first7=MI | title=A safety assessment of the antimalarial herb Artemisia annua during pregnancy in Wistar rats | volume=27 | issue=5 | pages=647–54 | doi=10.1002/ptr.4760 | journal=Phytotherapy Research| s2cid=22650085 }}

The WHO has approved riamet (Coartem), a combination of lumefantrine (120 mg) and artemether (an artemisinin derivative extracted with ether, 20 mg) in repeat treatments over two days, producing efficacy of up to 98% against malaria.

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 malaria parasite.{{cite book |author1=Cumming JN |author2=Ploypradith P |author3=Posner GH |title=Antimalarial Activity of Artemisinin (Qinghaosu) and Related Trioxanes: Mechanism (S) of Action |author-link3=Gary H. Posner |volume=37 |pages=253–97 |pmid=8891104 |doi=10.1016/S1054-3589(08)60952-7 |series=Advances in Pharmacology |date=1996 |isbn=9780120329380 }} Malaria is caused by apicomplexans, primarily Plasmodium falciparum, which largely reside in red blood cells and contain iron-rich heme-groups (in the form of hemozoin).{{cite journal |author=Gary H. Posner & Paul M. O’Neil |title=Knowledge of the Proposed Chemical Mechanism of Action and Cytochrome P450 Metabolism of Antimalarial Trioxanes Like Artemisinin Allows Rational Design of New Antimalarial Peroxides |journal=Acc. Chem. Res. |year=2004 |volume=37 |pages=397–404 |doi=10.1021/ar020227u |pmid=15196049 |issue=6}} In 2015, artemisinin was shown to bind to a large number of cell targets, indicating its potential for diverse effects.{{cite journal | vauthors = Wang J, Zhang CJ, Chia WN, Loh CC, Li Z, Lee YM, He Y, Yuan LX, Lim TK, Liu M, Liew CX, Lee YQ, Zhang J, Lu N, Lim CT, Hua ZC, Liu B, Shen HM, Tan KS, Lin Q | title = Haem-activated promiscuous targeting of artemisinin in Plasmodium falciparum | journal = Nature Communications | volume = 6 | pages = 10111 | pmid = 26694030 | doi = 10.1038/ncomms10111 | pmc=4703832 | year=2015| bibcode = 2015NatCo...610111W }}

Despite global efforts in combating malaria, it remains a large burden for the population, particularly in tropical and subtropical regions. As of 2013, it seems that the pathogenic agent of malaria is becoming resistant to artemisinin-based drugs.[http://csis.org/publication/drug-resistant-malaria News] published on the Center for Strategic and International Studies website (Nov. 7, 2013){{cite journal|last1=Tulloch|first1=Jim|last2=David|first2=Benedict|last3=Newman|first3=Robert D|last4=Meek|first4=Sylvia|year=2013|title=Artemisinin-resistant malaria in the Asia-Pacific region|journal=The Lancet|volume=381|issue=9881|pages=e16–7|doi=10.1016/S0140-6736(12)61820-0|pmid=23122219|s2cid=1814045}} Emergence of artemisinin resistance has been identified in Cambodia and the border of Thailand. Although the WHO recommends artemisinin-based remedies for treating uncomplicated malaria, artemisinin resistance has become a concern. The causes that affected the emergence of artemisinin resistance include the use of artemisinin-based remedies. Encouraging herbal alternatives are in the pipeline, but a more dependable solution for the eradication of malaria would be the creation of an effective vaccination.{{cite journal | pmid= 20578122 | year= 2010 | last1= Chrubasik | first1= C | last2= Jacobson | first2= RL | title= The development of artemisinin resistance in malaria: Reasons and solutions | volume= 24 | issue= 7 | pages= 1104–6 | doi= 10.1002/ptr.3133 | journal= Phytotherapy Research| s2cid= 37901416 }} Resistance will likely spread to other endemic areas across the world.{{cite journal | pmid= 23656342 | year= 2013 | last1= Na-Bangchang | first1= K | last2= Karbwang | first2= J | title= Emerging artemisinin resistance in the border areas of Thailand | volume= 6 | issue= 3 | pages= 307–22 | doi= 10.1586/ecp.13.17 | journal= Expert Review of Clinical Pharmacology| s2cid= 207210000 }}

In traditional Chinese medicine (TCM), A. annua is prepared with water to treat fever. Owing to duplication in ancient TCM sources, A. annua is more commonly referred to as qinghao ({{zh|c=青蒿|p=qīnghāo}}), the modern Chinese name for Artemisia carvifolia, as opposed to its current Chinese name huanghuahao.{{cite web|last1=Liu|first1=Artemisia|title=【2015诺贝尔奖】青蒿素、青蒿、黄花蒿，究竟什么关系？|trans-title=2015 Nobel: Artemisinin, qinghao, and huanghuahao, how are they related?|url=http://www.guokr.com/article/440801/|publisher=guokr|access-date=19 January 2017|language=zh|date=2015-10-09}}

{{Reflist}}

{{Commons category|Artemisia annua}}

• [https://web.archive.org/web/20170208033255/https://hort.purdue.edu/newcrop/proceedings1996/V3-578.html Distribution of artemisinin in Artemisia annua]
• [https://www.york.ac.uk/research/impact/tackling-malaria-with-plants/ Project to improve artemesinin yield at the University of York (UK)]
• [https://hort.purdue.edu/newcrop/CropFactSheets/artemisia.pdf Data sheet about Artemisia annua] from Purdue University

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annua

Category:Medicinal plants of Asia

Category:Flora of Asia

Category:Plants described in 1753

Category:Taxa named by Carl Linnaeus