Professor Jacob Midiwo is at the Department of Chemistry, University of Nairobi, Kenya, Africa Dr John Clough is at Syngenta, Bracknell, UK

Aspects of African Biodiversity

Proceedings of the Pan Africa Chemistry Network Biodiversity Conference Nairobi, 10-12 September 2008

By J. O. Midiwo, J. M. Clough

The Royal Society of Chemistry

Copyright © 2010 The Royal Society of Chemistry
All rights reserved.
ISBN: 978-1-84755-948-7

Contents

CHALLENGES AND OPPORTUNITIES FOR AFRICA: AN OVERVIEW OF KEY THEMES FROM THE PACN BIODIVERSITY CONFERENCE S.C. Smith, 1,
EXPLORING THE THERAPEUTIC POTENTIALS OF AFRICAN MEDICINAL PLANTS C. Wambebe, 8,
NATURAL PRODUCTS FROM PLANT BIODIVERSITY AND THEIR USE IN THE TREATMENT OF NEGLECTED DISEASES J.O. Midiwo, 11,
IN VITRO AND IN VIVO ANTIPLASMODIAL ACTIVITY OF KENYAN MEDICINAL PLANTS M. O. Nanyingi, K.B. Kipsengeret, C.G. Wagate, B.K. Langat, L.L. Asaava and J.O. Midiwo, 20,
ANTI-LARVAL ACTIVITY OF CRUDE PLANT EXTRACTS FROM VITEX SCHILIEBENII AND VITEX PAYOS (VERBENACEAE) G.N. Makua, I.O. Ndiege, A. Hassanali and P.K. Tarus, 29,
NATURAL PRODUCTS AS LEADS FOR NEW AND INNOVATIVE CROP PROTECTION CHEMICALS J.M. Clough, 34,
EXPLOITING PHYTOCHEMICAL DIVERSITY TO CONTROL PESTS OF AGRICULTURE AND VECTORS OF HUMAN AND ANIMAL DISEASE A.M. Hooper, Z.R. Khan, B. Torto, M.A. Birkett, T J. Bruce, J.A. Pickett, 43,
ROOT CHEMICALS COULD OFFER OPPORTUNITIES FOR BREEDING FOR SWEET POTATO RESISTANCE TO THE WEEVIL Cylas puncticollis Boheman (COLEOPTERA: APIONIDAE) H. Muyinza, P.C. Stevenson, H. Talwana, D.R. Hall, D. I. Farman and R.O.M. Mwanga, 49,
THE ROLE OF BIOTECHNOLOGY IN MEETING THE BIODIVERSITY CONSERVATION CHALLENGE OF AFRICA A.B. Salifu, 58,
FARMERS AS A TREASURE CHEST OF BIODIVERSITY – THE CASE OF SORGHUM [Sorghum bicolor (L.) moench] IN ETHIOPIA, A FIVE DECADE ANALYSIS F. Mekbib, 65,
DELIVERY OF APPROPRIATE CATTLE GENOTYPES TO EASTERN AFRICAN SMALLHOLDER FARMERS THROUGH IN-VITRO EMBRYO PRODUCTION TECHNOLOGIES – THE TECHNICAL PROCEDURES, PROSPECTS AND CHALLENGES H.M Mutembei, S.E. McClintock, B. Muasa, R. Origa, Jimbo, S. V. T. Tsuma, E.R. Mutiga, A.E. McClintock and A.M Okeyo, 84,
LEVELS OF SOME NUTRIENTS AND NON-ESSENTIAL METALS IN COWS’ WHOLE MILK FROM ADDIS ABABA, ETHIOPIA E. Admasu, B.S. Chandravanshi, T. Wondimu, and G. Akalu, 91,
WATER, WATER EVERYWHERE AND WHEN FOUND NOT FIT TO DRINK S.O. Wandiga, 105,
FOUNDATION FOR ANALYTICAL SCIENCE AND TECHNOLOGY IN AFRICA AND ITS ROLE IN THE PRESERVATION OF ENDANGERED SPECIES S. Lancaster, N. Richards and A. Gachanja, 126,
Jua Kali METALLURGICAL INDUSTRIES AS POINT SOURCES OF THE HEAVY METALS LEAD AND CADMIUM TO AQUATIC SYSTEMS IN KENYAN URBAN AREAS S.M. Mule and C.M. Nguta, 131,
AN ASSESSMENT OF EFFLUENT TREATMENT TO REDUCE HEAVY METAL LEVELS IN EFFLUENT FROM A BATTERY MANUFACTURING CONCERN E. Muleya and F. Chiumira, 137,
SPECTROSCOPIC DETECTION OF GASEOUS AMMONIA IN THE ENVIRONMENT C.B.O. Kowenje and D. C Doetschman, 143,
JATROPHA CURCAS L. AS A SOURCE FOR THE PRODUCTION OF BIODIESEL IN KENYA A. W Wagutu, S. C Chhabra, CL. Thoruwa, T.F. Thoruwa and R.L.A. Mahunnah, 152,
JATROPHA BIODIESEL AS AN ALTERNATIVE TRANSPORT FUEL IN ZIMBABWE C S. Shonhiwa, F. P. Gudyanga and Z. Chiguvare, 160,
BIOMASS, BIO-BASED PRODUCTS AND BIOENERGY P.C Vieira, 176,
MUNICIPAL SOLID WASTE AS A RESOURCE RATHER THAN A WASTE. A PRELIMINARY STUDY OF BIOMASS FROM GITHURAI MARKET, AN OPEN MARKET IN THE OUTSKIRTS OF NAIROBI CITY N Muriithi, C. Soi and J. M. Keriko, 188,
SUBJECT INDEX, 192,

CHAPTER 1

CHALLENGES AND OPPORTUNITIES FOR AFRICA: AN OVERVIEW OF KEY THEMES FROM THE PACN BIODIVERSITY CONFERENCE

S.C. Smith

Syngenta, Crop Protection Research Chemistry, Jealott’s Hill International Research Centre, Bracknell, Berkshire RG42 6EY, UK

1 INTRODUCTION

A wall of three-dimensional tiles representing different micro-organisms provided an impressive backdrop in the Conference Centre of Nairobi University, an appropriate setting indeed for the inaugural Conference on Biodiversity of the Pan Africa Chemistry Network. This prologue chapter will give a flavour of the wide range of topics covered at the conference and will highlight some of the key themes that emerged from the individual scientific contributions. Much of the material was provided to the participants at the end of the conference in a ‘rapporteur summary’ and I would like to gratefully acknowledge the valuable contributions of my co-rapporteurs in distilling out the main points.

Firew Mekbib from Ethiopia defined biodiversity during one of the sessions as ‘the totality of genes, species and ecosystems in a region’. The range of presentations at this conference reflected the diversity of science that impacts our understanding and practical utilisation of the rich biodiversity in Africa. They included areas such as: African and global plant biodiversity; the use of natural products in medicines and crop protection; biofuels; management and conservation of biodiverse ecosystems; genetic variation in crops and animals; environmental monitoring of pollutants; and waste management.

Syngenta has summarised its goal as ‘bringing plant potential to life’. In doing so, sustainable agriculture is of fundamental importance and this relies on maintaining the biodiversity of agricultural environments. As an example, Syngenta is a member of the Global Crop Diversity Trust, a foundation committed to conserving crop diversity for global food security. It was therefore of particular interest to see how many of the presentations touched on this theme, reflecting the importance of agriculture in Africa and the real challenges it faces in the future.

The conference began with a thought-provoking puppet show from the Chanuka Express Theatre Company, which highlighted some of the concerns of young Africans about the adverse impact man can have on our environment. The play focused on the indiscriminate use of pesticides, the problem of polluted water, and human actions upsetting the balance of nature. In reality, there is an enormous global challenge to increase agricultural productivity in a sustainable way, with limited land, to meet the requirements for food, feed, fibre and fuel of a growing and increasingly affluent population. The biodiverse ecosystems we currently have need to be maintained, while increasing the quality and quantity of production from existing land. A loss of biodiversity makes an ecosystem more vulnerable to changes in the environment. There may be fewer species to support fundamental ecosystem functions, such as pollination. Realistically, the agricultural challenge can only be achieved through technological innovation, which will include chemical pest control and biotechnology. Modem crop protection chemicals comply with strict environmental regulations and bring great benefits to agriculture. Unfortunately, the best products are not always readily available to African farmers who, instead, may have to rely on older or generic chemicals with the associated issues of regulation and stewardship.

Although the conference highlighted many threats to the environment and potential detrimental effects on biodiversity, we should recognise that these problems present important opportunities for science, and chemistry in particular, both to thoroughly understand the issues and then provide innovative solutions. There are some huge global challenges (such as food, water, energy and health), which were presented with an African dimension. There are also opportunities for innovation in technology and for improving our basic understanding of the underlying sciences. These should provide academics with important, and highly relevant, targets for their research and our young scientists with inspiration to develop their careers in the future. We should also start to feel that, as scientists, we can be driving potential solutions and counter the all-too-common public perception that science is part of the problem.

2 KEY THEMES FROM THE CONFERENCE

Sebsebe Demissew (National Herbarium, Addis Ababa University, Ethiopia) started the conference off in style by introducing the tremendous range of plant diversity in Africa, where there are 40-45,000 species growing across many diverse habitats, equating to over a fifth of the world’s flora. We rely on plants for food, medicines, crop protection, and materials for clothing and building. They also provide ecological services, cleaning our air, water and soil. Wild relatives of cultivated species provide a pool of genetic diversity for future crop improvements. Plants also offer technical and commercial opportunities for Africa. Examples include low-caffeine coffee and the nutritious grain Tef from Ethiopia which are marketed in the West. The latter is a gluten-free crop that is used in health foods and may be of benefit to diabetics. There are some important challenges, which include unsustainable harvesting, burning, human interference, climate change and ensuring local communities benefit from the exploitation of both their natural resources and know-how. Last, but not least, there is a lack of new botanists being trained to help us understand the true untapped potential of African plants.

Africa contains two out of the five global ‘higher biodiversity areas’ and nine biodiversity hotspots. Mkabwa Manoko (University of Dares Salaam, Tanzania) stressed the need to ensure conservation and restoration of Africa’s biodiverse areas and for local communities to share in the benefits derived from any exploitation of biodiversity, particularly where this originated from indigenous knowledge of traditional medicines. Of the drugs prescribed in the USA, 56% have a natural origin, reflecting the importance of this resource. Threats to biodiversity include population growth, invasion by exotic species, destruction of natural habitats and changes in land use. Fundamental inequality between production and consumption is an issue facing Africa, and future shared benefits will rely on equitable partnerships with local communities.

Berhanu Abegaz described NABSA (Network for Analytical and Bioassay Services in Africa, University of Botswana) as an analytical centre of excellence and a model of networking in the discovery of new natural products. He outlined the approach used at NABSA for the identification of secondary metabolites from the huge plant diversity in Africa (sometimes via ethnobotanical approaches), as well as research into their properties, biosynthesis and function. NMR instruments operating at frequencies up to 600 MHz are used in this research, and are also available on a service basis for other African scientists. Importantly, this centre of excellence goes some way towards making up for labs elsewhere that are often poorly equipped, enabling African scientists to engage in short-term collaborations, publish in high-impact journals, and to begin to compete at an international level. It also encourages African scientists to work on African problems.

Jacob Midiwo (NAPRECA, University of Nairobi) then went on to discuss the opportunities that plant-derived remedies present for the treatment of neglected diseases in Africa. The WHO estimates that 80% of the world’s population already rely on traditional plant-derived medicines. There are still opportunities for new therapies; for example, over 500 plants are potential sources of anthelmintics. The high levels of active components (up to 10-15% in some cases) offer the possibility of field treatments based on plant extracts. This would avoid the need for very expensive drug development, which is out of the reach of most African organisations. Malaria is a critical global problem with 300-500 million cases a year, 80% of which are in Africa. In Kenya alone, 22 million people are at risk, and children are particularly vulnerable. However, trying to control malaria is like ‘shooting at a moving target’ as resistance develops rapidly. African ‘ethno-medicines’ or ‘Herbal Combination Therapies’ (HCTs) based on plant extracts may offer an alternative to ACTs (Artemisinin Combination Therapies). Professor Midiwo described a bioassay-guided fractionation approach to the identification of novel compounds such as diprenylated flavanones. The next challenge is to develop novel formulation methods for these compounds. Lawrence Arot Manguro (Maseno University, Kenya) also used bioassay- guided fractionation in the isolation of sesquiterpenes from the African evergreen tree Warburgia ugandensis as potential antifungals.

Charles Wambebe (FAS, FTW, International Medical Research in Africa, Abuja, Nigeria) continued the theme of African medicinal plants. Of the new medicines introduced between 1981 and 2002, 67% are of plant origin. However, less than 10% of the ~70k African plants have been explored for their potential. Intellectual property rights must be considered and benefits shared equitably with local communities and scientists. This creates a need for better professional governance and ethics. Pharma pipelines can be long and expensive and are therefore unrealistic for Africa. There are issues for the development of herbal remedies which will contain mixtures – including safety, quality control (fingerprint profiling) and ethical review of clinical research (most countries do not have a review body at a national level). Despite these issues, there are some success stories, e.g. Niprisan from sorghum, which is licensed to the U.S. company XeChem as a sickle-cell treatment, with a share of the profits fed back to the African research institute.

Tony Hooper (Rothamsted Research, UK) discussed local applications of ‘push-pull’ insect-control strategies with plant-derived semiochemicals and pheromones in the control of crop pests. For example a sudan grass trap crop reduced the number of stem borers on maize grown in adjacent plots. Five thousand African farmers have already been involved in a practical test of the methodology which exploits plant diversity in a very creative way. It was an excellent example of an understanding of chemistry and biotechnology being put to practical use in a local context.

John Clough (Syngenta, UK) described the Syngenta approach to agrochemical discovery and, more specifically, the screening of natural products as potential leads and the synthesis of analogues. Syngenta has collaborated with external partners to acquire novel natural products, ensuring an equitable agreement to share in any successes. Rediscovery of known compounds is common and many natural products are only weakly active, unstable or have undesirable functionality for use as agrochemicals, so relatively few make it through into research programmes. Synthetic strategies take into account the physical properties of targets and scope for simplification. There are significant challenges in the optimisation of natural product leads to commercial agrochemicals, and in some cases this has required the synthesis of thousands of analogues, something that is only feasible within a commercial organisation. Syngenta makes more use of microorganisms than plants as a source of natural products, since it is easier to re-supply larger quantities of compounds produced in this way. Africa must have a huge and diverse array of micro- organisms, and these surely represent a huge research opportunity for the future. Insects and arthropods make up over half of animal species and as such are relatively under-explored as sources of natural products. John Bwire Ochola [International Centre of Insect Physiology and Ecology (ICIPE), Kenya] has been using bioassay-guided fractionation of the venom from Kenyan scorpions in a search for selective insecticides.

Hayder Abdelgader (Agricultural Research Corporation, Sudan) talked about ‘soft pesticides’ – those commercial insecticides with a low impact on beneficial or predatory insects – and their role in integrated pest management in conjunction with natural enemies. This strategy recognises the vital importance of considering the wider agricultural ecosystem when controlling crop pests.

Of the ecosystems on which the world depends, 60% are being degraded. How do we access local knowledge to assess the potential impact on crop diversity and genetic erosion? Firew Mekbib (Harmaya University, Ethiopia) described the key roles farmers can play in the conservation of crop biodiversity in sorghum – known as the ‘camel crop of cereals’ because of its drought tolerance. Interestingly, sorghum farmers have developed their own ‘folk taxonomy tree’ and a local seed bank. This helps them to breed specific varieties for food, feed and materials and to very effectively contribute to long term food security via increasing genetic diversity. The discussion after Firew Mekbib’s presentation highlighted Striga as a neglected African weed in sorghum.

Ethiopian dairy cattle genetics were the subject of the presentation by Henry Mutembei [International Livestock Research Institute (ILRI), University of Nairobi]. There is a rising demand for milk and meat (expected to more than double by 2020) so an understanding and optimisation of cattle genetics will be of great value. There are knock- on beneficial effects in tackling farmer poverty and relieving pressure on natural resources. An in vitro embryo production (IVEP) tool can be applied in cattle breeding to identify, select and conserve key traits. The ambition of ILRI’ s research is to tailor cattle genetics to specific environmental regions and thereby maximise outputs of milk. Tree biodiversity can also be monitored through genetics. J.S. Nantongo (Makerere University, Uganda) described genetic tools that would allow us to understand the gene flow and diversity of forests and thereby identify the most effective strategies for restoration and the conservation of biodiversity.

(Continues…)Excerpted from Aspects of African Biodiversity by J. O. Midiwo, J. M. Clough. Copyright © 2010 The Royal Society of Chemistry. Excerpted by permission of The Royal Society of Chemistry.
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