The importance of tropical rain forests as sources of medicinal plants used in traditional health systems and of raw material required for modern drug development is briefly discussed. The need for the conservation and sustainable use of these natural resources is emphasized.
Considering the yearly loss of tropical rainforests (total area lost each year equivalent to 4-5 times the size of the Netherlands), one can easily foresee a drastic reduction in the size and quality of this biotope, with the exception of a few protected areas scattered around the globe. At this deforestation rate, the luxuriant tropical fauna and flora, including plants with known or potential medicinal value, will be decimated and indigenous medical knowledge has little chance to survive. Rainforest deforestation poses a clear threat to human safety by causing inter alia, landslides, floods and desertification, soil erosion and the spread of some diseases, such as malaria. The extinction of medicinal plants and medicine men, however, presents a more hidden health risk to both developing countries and (newly) industrialized societies. This article focuses on the role medicinal plants play in both modern and traditional health care systems. These plants also represent an important class of so-called non-timber forest products that provide a sustainable and economically viable alternative to the ongoing destructive exploitation of the rainforests.
Rainforests contain no less than 60% of all higher plant species known on earth and they provide all that is needed for human survival, including remedies against disease. Through evolution, plants have developed large numbers of chemical substances to defend themselves against insect pests and fungal and other pathogenic diseases. Some of these agents can also act within the human body against microorganisms and other causes of disease, and represent an important source of natural drugs. Their highly complex molecular structures often surpass the imagination of the chemist and cannot easily be reproduced in the laboratory.
More than 35,000 plant species are being used in various human cultures around the world for medical purposes and many of them are subjected to uncontrolled local and external trade (Lewington, 1993). So far, natural products from fewer than 40 tropical species have been incorporated into modern medicine and only a fraction of the tropical flora has been thoroughly analysed for their pharmacological activity. Therefore, the annual extinction rate of an estimated 3,000 plant species is a matter of great concern as it could imply the loss of a potential drug against an incurable condition, such as dementia, cancer, influenza or AIDS. The resulting health impact on the basic needs of the population in developing countries is equally important and will be discussed separately.
Health care and botany have evolved as inseparable domains of human activity: the medicine man (shaman) is often regarded as the first botanical professional in human history. Whereas western medicine, as taught in most medical schools around the world, has largely switched from natural to manufactured drugs, plant products are still of paramount importance in traditional health care systems of developing countries.
In traditional therapies of certain indigenous communities, herbs are administered along with chants, dance and spiritual ceremonies to expel bad spirits and to help reharmonizing the sick person with his or her environment. Plants, however, also serve a less metaphysical role, as anticonceptives in indigenous birth control procedures or to counteract tangible pathogenics such as fungi and parasites (e.g. worms, malaria). In developing countries, medicine men and women are particularly knowledgeable about the recognition and treatment of common diseases. In Amazonia, at least 1,300 plant species are being used as medicines, poisons or narcotics (Schultes, 1979). Traditional healers are also skilled botanists and have a great talent for locating the requisite plant from the green vastness that makes up their natural pharmacy. In Latin America and Africa, this knowledge has largely remained undocumented and is handed down orally from father to son or from mother to daughter. Today's younger generations often have very different ambitions and, therefore, these traditional skills are doomed to get lost even faster than the plants themselves. This is why ethnobotanists compare the death of a shaman to the loss of a national library and invest much effort in assembling this knowledge as written accounts. Recent examples of such endeavours include The Healing Forest by Schultes and Raffauf (1990) which is a treatise on the health care traditions of Amazonian Indians, and Rainforest Remedies: One Hundred Healing Herbs of Belize by Arvigo and Balick (1994).
In recent years, traditional healing in distant forest areas has come under pressure from novel diseases such as influenza and tuberculosis (Shapiro, 1993), that have often revealed the superiority of 'white man's capsules'. This course of events has greatly affected the prestige of the local healers and has also opened the market for expensive and less necessary western drugs. Apart from the heavy drain imposed on foreign exchange reserves by these imports, the existing available and often equally effective traditional equivalents have been forced into disuse and oblivion.
Although western medicine has been integrated to some extent with ancient health care systems in Asia, it has become the dominant method in most larger hospitals around the world. In non-hospital care in most developing countries, traditional and modern systems operate independently without a clear hierarchy, whereas in rural areas only traditional healing and herbal self-care may be at hand. In these countries, there is a great demand for medicinal plants that often come from the forests. In the future, the use of these plants can be expected to increase further due to population growth and the increasing importance being attached to traditional health care by the World Health Organization (WHO). WHO's 'Health for All by the Year 2000' campaign emphasizes the urgent need for the conservation of medicinal plants (see following page for the text of the Chiang Mai Declaration", from Akerele, 1991). This same initiative has launched a first step toward a more rational use of herbal medicines in the Carribean, following a recent pharmacological evaluation of their effectiveness and safety ( for example, the Tramil Project; see in Rabineau, 1991).
In the second half of this century, 'chemical' drugs have largely replaced plant products in mainstream medicine. This development is in line with the prevailing concept of disease, the belief in human-initiated progress, and the quest for pure therapeutic substances that contain no more than one active principle.
On closer analysis, however, over 25% of all prescription drugs in the Organization for Economic Co-operation and Development (OECD) countries, and up to 60% of those in Eastern Europe, prove to consist of unmodified or slightly altered higher plant products (The Lancet, 1994). They embrace such important therapeutic categories as anticonceptives, steroids (e.g. prednisone) and muscle relaxants for anaesthesia and abdominal surgery (all made from the wild yam); quinine and artemisinin against malaria; digitalis derivatives for heart failure; and the anticancer drugs vinblastin / vincristin, etoposide and taxol. These agents cannot be (fully) synthesized in a cost-effective manner. Therefore, their production requires reliable supplies of plant material, either from cultivation or from the wild. Such is the case for the wild yam Dioscorea composita (Hemsl.), which cannot be cultivated and is exported from Mexico and other countries in quantities of hundreds of tons.
These few examples should make one realize how modern drug delivery
depends on the continuing availability of raw materials and how vulnerable
it is to the exhaustion of natural resources. This awareness is even more
pertinent to clients of health products stores and herbalists, since natural
non-prescription formulae may contain rare and even endangered wild plants
that are regarded, often unjustly, as more powerful than their cultivated
analogues (Fuller, 1991). So far, only three species of medicinal plants
have been listed by CITES, the Convention on International Trade in Endangered
Species of Wild Fauna and Flora (Lewington, 1993).
Saving Lives by Saving Plants
We, the health professionals and the plant conservation specialists who have come together for the first time at the WHO/IUCN/WWF International Consultation on Conservation of Medicinal Plants, held in Chiang Mai, 21-26 March 1988, do hereby reaffirm our commitment to the collective goal of "Health for All by the Year 2000" through the primary health care approach and to the principles of conservation and sustainable development outlined in the World Conservation Strategy.
Recognise that medicinal plants are essential in primary health care, both in self-medication and in national health services;
Are alarmed at the consequences of loss of plant diversity around the world;
View with grave concern the fact that many of the plants that provide traditional and modern drugs are threatened;
Draw the attention of the United Nations, its agencies and Member States, other international agencies and their members and non-governmental organisations to:
The vital importance of medicinal plants in health care;
The fact that plant resources in one country are often of critical importance to other countries;
The significant economic value of the medicinal plants used today and the great potential of the plant kingdom to provide new drugs;
The continuing disruption and loss of indigenous cultures, which often hold the key to finding new medicinal plant that may benefit the global community;
The urgent need for international cooperation and coordination to establish programmes for conservation of medicinal plants to ensure that adequate quantities are available for future generations.
Natural drugs and medicinal plants, along with other non-timber forest products, already yield important economic returns (Table 1). They compare favourably in monetary terms with logging and cash cropping (Peters, Gentry and Mendelsohn, 1989; Balick and Mendelsohn, 1992), and contribute in providing better prospects for sustainable forest use (Quansah, 1994).
Table 1. Market value of timber and non-timber forest products (NTFPs)
|Product||Year||Value in million US$||Reference||Comments|
|1985||100||Farnsworth, 1988||World sales; profit 88%|
|Pilocarpin||1989||29||Elisabetski, 1991||US sales|
|Jamu*||1992||1000||Gollin, 1992||Indonesia, local markets|
|Brazil nuts||1983||216||Duke, 1988||Brazilian exports to USA|
|Essential oils||1983||63||Duke, 1988||Imports into USA|
|Rattan||1983||87||de Beer & McDermott, 1989||Exports from Indonesia|
|All NTFPs||1983||127||de Beer & McDermott, 1989||Exports from Indonesia|
|Timber||1986||6700||FAO, 1987||World exports|
*traditional line of health products and herbal remedies.
The pharmaceutical industry has recently rediscovered the tropical rainforests as an unmatched source of chemicals with potential for new drug development (Pistorius and van Wijk, 1993), which promises additional revenues. Thousands of plant extracts of all continents are being screened for activity against HIV and cancer in the laboratories of the U.S. National Cancer Institute. For example, Merck Sharpe & Dome, a New Jersey based pharmaceutical company, has paid US$1 million for research rights in Costa Rica and has agreed to contribute 25% of profits made from Costa Rican plants to rainforest conservation in Costa Rica (Sittenfeld and Gamez, 1993). Shaman Pharmaceuticals Inc., a pioneer in ethno-directed natural product research since 1989, considers indigenous people as partners and only collects plant samples on the indication of a shaman. This approach appears to be more effective than random collection methods (Cox and Balick, 1994) and has already resulted in the discovery of three novel drugs. Before long, one of these drugs, SP 303, will become available as a neat monocomponent drug against herpes simplex and secretory diarrhea (Rozhon and King, 1996). SP 303, soon to be known as Provir and Virend, originates from an ordinary weed in Peru that can be harvested in a sustainable way. The expected market value may be hundreds of millions of U.S. dollars. Part of the profits will be returned to the Indian communities in the form of support for cultural and health care projects and nurseries for endangered medicinal plants (King and Tempesta, 1994). As a further consequence of this development, the prestige of the shaman will be upgraded, also in western eyes.
Even today, plant diversity is still indispensable for human well being and provides all or a significant number of the remedies required in health care. Forests, and particularly tropical rainforests represent vast natural pharmacies by virtue of their enormous, largely untapped source of plant material and their related indigenous knowledge of its medical use. Considering the role played by plant-derived products in human health, these resources are at the focal point of a new argument for more effective rainforest conservation. Prudent harvesting of rainforest products, however, requires ensuring a high degree of sustainability and a permanent dialogue with the native populations concerned. Medicinal plants may help build a bridge between quite different medical systems, providing the best of two worlds and allowing their practices to become more complementary.
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