13 December 2007 | EN
Traditional healers are joining forces with plant chemists in Kenya to develop antimalarials isolated from plants, reports Tatum Anderson.
In the shadow of Mount Kenya, traditional healer Jack Githae enters what he describes as his 'natural pharmacy'. It's a dense area of bush where elephants occasionally wander packed with a range of plants and trees from the African olive to the prickly euphorbia.
Githae quickly identifies a plant that he uses to treat patients with malaria. With a well-worn machete, a hoe and a pair of hand shears, he cuts off some of the tree's roots, prunes the branches and chisels off a few wafer-thin shavings of bark.
But rather than create a traditional remedy to treat a patient, he wraps up his harvest and sends it to the Kenya Medical Research Institute (KEMRI) in the country's capital Nairobi.
Githae is just one of a growing band of traditional healers who are working with scientists in the hunt for the next malaria wonderdrug.
The search for compounds
The search for compounds
Once a week, healers bring the plants they use to treat malaria to KEMRI. Scientists at the institute's Centre for Traditional Medicine and Drug Research, headed by Geoffrey Rukunga, then test the plants. KEMRI also consults with botanists at Kenya's National Herbarium to ensure the plants are correctly classified.
Rukunga's team has tested thousands of plants in the search for a compound that can kill the malaria parasite and is safe enough to be turned into a commercial drug.
The collaboration between healers and scientists in Kenya is likely to be fruitful, says Githae. "We are very rich in plants that cure malaria," he says. "I am surprised it has taken so long to develop products."
For example, a plant known as neem is used to prevent malaria in East Africa, and some species of aloe are used as traditional treatments.
|Some species of Aloe are
used as traditional medicines
Drugs derived from natural products are hugely important to the modern pharmaceutical industry. Antibiotics and aspirin were first isolated from bacteria and willow, respectively, and the first ever antimalarial drug, quinine, came from the bark of the South American cinchona tree.
To identify a potential antimalarial compound, the KEMRI scientists must first separate hundreds of likely plant components and test every one.
Each is exposed to the malaria parasite under laboratory conditions –– a process known as in vitro screening. If an isolated, purified compound successfully kills the parasite, it is next tested on animals infected with malaria.
Rukunga says that any compounds that kill 75 per cent of the parasites in an animal but that leave human cells unaffected are likely to be classified as a 'lead compound', a molecule that could potentially be turned into a drug.
So far, only five of the plant-derived compounds have been tested on animals, but those will not be followed up as they do not kill three-quarters of the parasites. Hundreds of others have not reached this stage because they perform poorly in the in vitro screen, or because they kill human cells in addition to the malaria parasite.
There is huge enthusiasm among Rukunga's scientists to find an African cure for what is seen as an African problem — 90 per cent of deaths from malaria happen on the continent. And there are armies of other scientists all over Kenya extracting and testing active ingredients from plants and trees.
Scientists are looking for new drugs because of the risk that the malaria parasite will develop resistance to established drugs, leaving little left to fight Kenya's biggest child killer.
"It would be a catastrophe if we didn't have cures," says Jacob Midiwo, an expert in natural-product research who heads another team testing antimalarial plants at the University of Nairobi. "At the moment, we have 7,000 deaths per day on this continent. If we didn't have antimalarials you can imagine what that would be like. It would just wipe out generations."
Constraints on progress
Constraints on progress
But there are many problems that make the elusive cure harder to track down, of which inadequate funding is the largest.
|Geoffrey Rukunga at KEMRI
with a plant extract
|Credit: WHO/Andy Craggs|
Although there are plenty of enthusiastic phytochemists able to extract and purify compounds, funds for research and training are paltry.
One team does not have an in vitro screening facility; another cannot test promising compounds for their toxicity to human cells. Rukunga's team needs a spectroscopy machine to help determine the chemical structure and purity of their isolated compounds –– essential for characterising a potential drug. Often samples have to be sent abroad to institutes such as the UK-based London School of Hygiene and Tropical Medicine.
But despite frugal use of resources in the laboratories, such as limiting expensive high-performance liquid chromatography to only particularly promising compounds, the costs of drug discovery are still prohibitive.
Another big problem is intellectual property. Scientists may be reluctant to share their results with others because there are often no hard-and-fast rules on who owns the knowledge. Kenya has regulations to guard intellectual property rights, but there are none on benefit sharing, least of all with indigenous communities.
As a result, many scientists will do ad hoc research on different natural products ––rather than systematically scouring for compounds –– that never progresses beyond publication in a scientific journal, says Francois Gasengayire of the International Development Research Centre, a Canadian donor to various schemes to promote and research natural products. "Scientists operate in a vacuum. But to get a product, we need a critical mass [of compounds]."
Keeping home-grown products
Keeping home-grown products
There are several initiatives aimed at trying to keep research on the continent.
One is aimed at encouraging scientists to share resources more effectively. Hashim Warsama Ghalib, of the UN's Tropical Disease Research Group based at WHO, agrees that collaboration is the only way that cures will be found on the continent. "The system for development of drugs cannot be completed in one centre," he says, "but everybody's doing their own thing".
For instance, the group has funded Rukunga's laboratory and will certify it as an international antimalarials screening centre in the next few months. The centre will then be able to carry out in vitro screening on samples sent by scientists from all over southern and eastern Africa. Another screening centre is being developed for West Africa.
|Jacob Midiwo and student
|Credit: Tatum Anderson|
"There is a need for a centre of excellence to set the pace in Africa," says Ghalib.
In addition, KEMRI is drawing up a series of agreements laying out exactly who owns the knowledge when samples are handed over to other institutions with suitable equipment. And crucially, there are agreements being set up for traditional healers like Githae to ensure that their initial and essential contribution will be rewarded financially.
But, despite these initiatives, the fact is that the next steps in drug development–– including chemically synthesising the compound so that it can be produced cheaply in large quantities — are unlikely to happen in Africa anyway.
The problem, again, is funding. There is precious little in the way of training for scientists who desperately want to do this type of work, says Erastus Mutuku Kitonyi, a phytochemist at the University of Nairobi who believes he will have to go abroad for training.
Scientists in his position are often forced to learn a new language and to leave their families for years at a time while they train abroad. Some scientists at KEMRI have had to learn Greek or Japanese before starting their PhDs; many never return.
Lead compounds emerging from Africa are likely to be handed over to pharmaceutical companies or public–private partnerships in the West.
Rukunga is a pragmatist. "If we can't do it in Africa, we have to collaborate with the West," he says. He expects to discover a lead compound within two years that will be handed over to a drug developer.
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