Life from natural sources

While modern medicine has developed skills, equipment and drugs capable almost of bringing the dead back to life, few appreciate that for 80 per cent of the world's population, when disease or illness strikes, there is still no other recourse but to traditional healers with their know-ledge of medicinal plants and skill in their use. Pharmacognosy, the study of plant medicines, once contributed significantly to the medical curriculum but nowadays its status is almost vestigial. There exists a dichotomy between the developed world, which has largely abandoned plants as its primary source of medicines (though many vital drugs were developed from natural product leads), and the developing world, in which there is scarcely any alternative.

Yet the developed world's interest in drugs obtained from higher plants is increasing once more: enormous profits await the company that identifies and develops the "right" drug, while the paucity of safe, fully effective drugs for the treatment of some illnesses prompts the continued search for novel drugs. The awareness that countries of the developing world are often much richer in flora, the useful properties of which their peoples are adept at exploiting, focuses our attention once more upon plants in the search for new chemotherapeutic agents.

Many researchers will find that Medicinal Resources of the Tropical Forest provides a comprehensive encyclopedia of essential facts and data with which to enhance research reports and lectures. It is, naturally, a specialist publication which will appeal primarily to those who work in this field but also to interested and resolute general readers.

The editors have made a good choice of diverse but complement-ary articles from a number of papers presented at the Tropical Forest Medical Resources and Conservation of Biodiversity Symposium convened at Rockefeller University in January 1992. There are also supplementary papers which expand several interlinking themes, some with long pedigrees in medicine and science - pharmacognosy, drug discovery, natural products chemistry, ethnobotany and ethnomedicine. Uniting these themes are the issues of how we might come to appreciate biodiversity and to develop discrete, nondestructive means for its utilisation, and of conservation and intellectual property rights, all of which are assuming great significance for effectual international cooperation in developing drugs and other products from plants.

The opening six chapters explore the traditions, rationale and potential of using plants as a source of medicines. Also included is a fascinating exploration of approaches that might be adopted in organising pharmaceutical companies with a specific remit for plant product research. Consideration is made of the knowledge to be gained from proper evaluation of the principles of disease aetiology, diagnosis and treatment as understood by traditional healers of the developing world. Progress is much hindered by the diversity of conceptual approaches to disease and treatment and by lack of a common vocabulary that precludes fruitful interaction between scientists, clinicians or healers of the developed and developing worlds, spawning mistrust and, often, unwillingness to collaborate.

Attention is drawn to the distinct differences between modern medicine, with its preference for well-tested single substance drugs directed at selected targets, and old traditional systems of medicine, which frequently employ mixtures of plants compounded for a particular patient on a specific occasion and which might be expected to act on a variety of targets simultaneously.

In using plants as a source of drugs, conservation issues are paramount. The tropical rainforests in many countries are disappearing at a relentless rate, often in the name of modernisation and progress. The plants they contain, perhaps unique to a particular locality, face extinction which, alone, should be cause for concern. Furthermore, plant chemicals may be so complex that synthetic chemists would scarcely dream of creating them (albeit that plants often achieve that which may prove nonviable, if not impossible, when attempted in the test tube) and molecular templates will vanish before being evaluated scientifically. These chapters, easily understood by the enquiring nonprofessional, could well stand publication as a separate volume for a keen and waiting readership.

the following chapters show increasing specialisation according to specific themes, most being selected examples of individual studies. Several chapters survey plant medicine knowledge, use and efficacy in various countries of Africa, Asia and South America, and also amongst discrete tribal communities. The sheer amount of research, labour and, by implication, financial investment, required to develop a single useful drug from many candidate compounds is well illustrated in contributions from pharmaceutical companies and from the United States National Cancer Institute. In recent years the NCI has diversified to investigate possible plant-derived anti-HIV agents and much might be achieved by applying newly discovered compounds to a battery of screening tests to maximise the chance of discovering significant biological activities: drug discovery is often as much fortuitous as it is reasoned and rational.

"Moral" or ethical considerations of medicinal plant exploitation are discussed in important chapters on biodiversity prospecting and property rights - demands on the finite resource; the rights of those in whose territory the plant grows and who have the knowledge and tradition of its use; guidelines for international agreements safeguarding such rights whilst acknowledging the needs of scientists and developers to obtain access to a natural resource; the economics and impact of harvesting a natural resource or, alternatively, selective cultivation (perhaps thus reducing the livelihood of a local population).

This book appears at a time when interest in plants as a source of drugs or medicines is burgeoning. It provides an excellent introduction for those with an interest in the topic, as well as positive ideas and sug-gestions which, were they to be implemented effectively and ideally, would see a vast improvement in humanity's respect for its environment and its acceptance of responsibility for its conservation. Furthermore, a number of useful plant-derived drugs await discovery, ones capable of alleviating mortality and morbidity in various situations of global importance. Unheeded, the hope offered by the contributors to this volume is likely never to be realised.

Geoffrey C. Kirby was lecturer in medical parasitology, London School of Hygiene and Tropical Medicine.