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Artemisia in Africa

For over 2000 years the Chinese have used Sweet Wormwood (Artemisia annua), mainly as a herbal tea preparation, for treating malaria and fevers. Studies in China in the 1970s led to the isolation and characterisation of artemisinin as the principal anti-malarial compound, and drug companies now extract and purify the compound in manufacturing the medicine in tablet form. In 2004, the World Health Organisation (WHO) adopted Coartem, an artemisinin-based combination therapy (ACT), as the recommended first-line treatment for malaria in Africa.

Artemisia annua
credit: Ahmed Hassanali, ICIPE:

For drug companies that have invested in ACT production, maintaining supplies of artemisinin is now a high priority. Until relatively recently much of the plant material was sourced from remote mountain regions in China where Artemisia annua grows wild. However, it is now being grown commercially in Asia, and also in Africa. Plans for a new extraction facility in Moshi, northern Tanzania are underway, and Novartis, producer of Coartem, has recently announced plans to expand cultivation in Kenya, Tanzania and Uganda to more than 1000 hectares.

Increasing demand

Demand for ACTs is anticipated to rise to several hundred million treatments within the next few years. However, despite the health as well as income benefits that growing Artemisia in Africa have to offer, there are concerns that the approach of using purified artemisinin could lead to resistance. Professor Ahmed Hassanali, a chemical ecologist at the International Centre of Insect Physiology and Ecology (ICIPE) says that, "Use of purified treatments in therapeutic anti-malarial preparations, which has led to resistance, is well known. In both Asia and Africa, malaria patients are no longer responding to chloroquine, a safe and previously efficacious treatment, and the sulphadoxine-pyrimethamine drugs, such as fansidar, indicating that malaria parasites in these two continents have become multi-drug resistant." Hassanali has also expressed concern that, despite the establishment of extraction companies in East Africa to make the drug more easily and cheaply available to patients, most ACT therapies are still currently too costly as a treatment for the poor - those that suffer the major burden of malaria.

Research on a drug based on the whole leaf of A. annua may provide an alternative solution. Scientists at ICIPE, collaborating with the Kenya Medical Research Institute (KEMRI) and the Natural Uwemba System for Health (NUSAG), a Tanzanian NGO, have been working to provide a cheaper yet efficacious malaria treatment. A proof-of-concept study, which commenced in June 2004 and ended in February this year, has yielded encouraging results. Clinical studies involving 48 patients with uncomplicated malaria have shown the whole-leaf drug to have impressive efficacy in treating the disease with no significant side effects. Phytochemical studies have suggested that it is the presence a number of flavonoids in the crude, unpurified extract of the plant, that have preserved its efficacy and prevented the parasite acquiring resistance during its long use in China. The test results have indicated that the artemesinin and other constituents may have a synergistic effect, which may be the key in preventing the development of resistance to artemesinin-based anti-malarial drugs.

Comparable results

Importantly, the research team has also shown that it is possible to manufacture whole-leaf A. annua anti-malarial tablets with comparable levels of artemisinin and other constituents to other ACT therapies. Using phytochemical analysis to guide the manufacturing process is key, not least because artemisinin content can vary between plants grown in different locations and between seasons. To make the whole-leaf drug, leaves are ground to a very fine powder and thoroughly mixed, which has proved effective in ensuring that each tablet has a standard dose of the drug.

The source plants being used by the team are grown in Arusha, and, encouragingly for African farmers, have been shown to yield a higher concentration of artemisinin than Chinese plants. Ongoing research will hopefully discover how growing conditions affect concentration level. Further studies aim to characterise key constituents that contribute to the anti-malarial activity of A. annua, leading to a selection of appropriate varieties or hybrids based on the optimum constituents of artemesinin and other key compounds. Hassanali is hopeful that this will allow a detailed business plan for large-scale planting and commercial production to be put in place for further production of whole-leaf A. annua-based drugs.

Artemisia is, however, difficult to propagate from its tiny seeds and cuttings prove a more successful means of multiplication. Such vegetative propagation is particularly useful for maintaining genetic qualities, such as the level of artemisinin. In Mozambique, the regional programme for the World Agroforestry Centre (ICRAF) has been training farmers how to propagate cuttings of a hybrid capable of growing in warmer climates. In co-operation with a number of local partners, including the Mozambique Ministry of Agriculture and Rural Development (MADER), ICRAF is also training farmers how to process Artemisia leaves in order to get much needed income from selling Artemisia-based medicines.

For further information on project in Mozambique see World Agroforestry website

Based on article written by Naftali Kure

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1st September 2005