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How can modern drug discovery methods enhance the value of African traditional medicines, asks South African drug expert Kelly Chibale.

Africa's biodiversity has the potential to be a major resource for developing pharmaceuticals to treat endemic diseases such as malaria, tuberculosis and HIV/AIDS. It is already the source of a wealth of traditional medicines used by at least 80 per cent of people on the continent.

But unfortunately, much of Africa's biodiversity remains unexploited for health and economic benefits. Decades of research into African traditional medicines by Africans have yet to translate into modern pharmaceutical products.

There are several reasons for this lack of progress. Drug discovery and development efforts are fragmented across the continent. African researchers, in addition to lacking the finance and infrastructure to tackle the disease burden, are also challenged by a limited skills base and poor access to the technological platforms needed for drug research.

The result is that the chemistry of traditional medicines is rarely sampled in modern drug discovery efforts.

It is time to bring the two worlds together.

A critical first step must be for African scientists to create a biomedical resource in the form of a database and physical collection (chemical repository) of purified and characterised natural products from various biodiversity sources, including traditional medicines and their pharmacologically active ingredients, from across the continent.

My colleagues and I have already begun work on this by establishing the Pan-African Natural Products Library (p-ANPL), a consortium of scientists across the continent, with the aim of creating the database and physical collection.

A springboard for action

Such a biomedical resource would provide a much-needed tool for attracting investment in the scientific expertise needed for the next steps of screening, medicinal chemistry and preclinical pharmacology that are vital to creating commercial pharmaceutical products.

But it would have other benefits, not least accelerating the development of sustainable infrastructure for drug discovery from traditional medicines in Africa. It would encourage the establishment of supply and extraction enterprises and could create a culture of collaboration and cooperation between scientists and traditional practitioners.

Benefit sharing programmes could also enable the local cultivation of medicinal plants in appropriate cases. And the process would help to recover or preserve species that might otherwise be lost.

What makes drugs work?

There are other ways in which recent scientific and technological developments can be used to improve the drug discovery process from traditional medicines. These include tapping into data on the genomes of disease vectors and using advances in biochemistry and molecular biology to identify and validate proteins crucial to the survival of disease-causing organisms.

A particular priority should be integrating drug metabolism and pharmacokinetic (DMPK) studies into research on traditional medicines. Such studies evaluate how a drug is processed by the human body and have important implications for the efficacy and toxicity of drugs.

Those engaged in translational research acknowledge that there is a strong interplay between genetics, the socioeconomic environment in which people live and effective treatment of diseases. African scientists must similarly recognise these connections and seek to relate them to traditional medicines.

Improvements in the platforms used for DMPK studies over the past two decades have reduced the failure rate of potential medicines in the pharmaceutical industry from 40 per cent before 1990 to less than ten per cent today.

Using new DMPK tools to re-assess historical traditional medicines and evaluate potential new ones could also help identify treatment failure and toxicity from interactions between drugs — this is particularly important where patients may be using traditional medicines with conventional drugs. The herb ginseng, for example, is known to reduce the anticoagulant effect of warfarin, used to prevent thrombosis and embolism.

China shows how

Experience from other developing regions has already shown the power of modern drug discovery methods in exploiting traditional medicines for health and economic gain. China, for example, has given the world artemisinin — the active ingredient of the Chinese plant Artemisia annua, which is now the preferred treatment, in combination with other antimalarial drugs, for malaria across the globe.

Although A. annua has been used in China for several hundred years in antimalarial herbal remedies, it was not until the chemical structure of artemisinin was revealed that the plant gained international scientific recognition and was accepted into modern medical practice to become a life-saving pharmaceutical.

The development of artemisinin has also spurred agricultural activities across the world to cultivate A. annua, with attendant economic and health benefits.

Integrating modern drug discovery and development practices — including a biomedical database and physical collection of resources — into research on African traditional medicines could provide the foundation for similar successes to emerge from our continent.

Kelly Chibale is a professor of organic chemistry at the University of Cape, South Africa and director of the South African Medical Research Council's Drug Discovery and Development Research Unit.

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