EVALUATION OF PHYTOTHERAPY (Herbalism) N.Z.Nyazema

• EVALUATION OF PHYTOTHERAPY (Herbalism)
  N.Z.Nyazema
  Department of Clinical Pharmacology, Medical School.
  P.O. Box A 178, Avondale,
  Harare, Zimbabwe
  E-mail: Nyazema@healthnet.zw
  
  Introduction
  
  Traditional Medicine, TM, can benefit from critical evaluation of the armamentarium of its remedies in at least two different ways.
  
  First, there is need to show which traditional treatments may be prompted as being clinically effective, and information fed back to he traditional practitioners. Such positive feedback will be of special importance, when factors such as economic unfeasibility or lack of social acceptance inhibit the application of the western synthetic drug armamentarium. Scientific insight into the physicochemical and pharmacological properties of the therapeutic principles may help to improve the utility of plants. For example, some in-vitro studies have shown that Abrus precatorius, Pterocarpus angolensis DC and Ozoroa insignis Del. which are widely used in areas of Zimbabwe where schistosomiasis is endemic, are effective in-vitro against Schistosome haematobium (Ndamba et al, 1994). Thus confirming their use in traditional medical practice for the treatment of Schistosomiasis.
  
  Secondly, research into TM phytotherapy can identify pharmacologically inactive therapies and harmful drugs, which should actively be discouraged. An example is a commonly used bulbous plant, Buphone distcha (Fig. 3.1) with psychoactive principles which are highly toxic and result in brief reactive psychosis.
  
  Research carried out must be seen as an effort to amalgamate TM and SM. For instance, a SM doctor treating a patient in Zimbabwe should be aware of the possibility that his patient is concurrently consulting or taking some TM remedies. There must therefore not be holes in his history taking. This is particularly important since plant products remain chemical entities, however complex the composition. Besides having biological effects in human beings, plant products used in phytotherapy must be dealt with by the body in the same manner any modern drug or pharmaceutical preparation is handled. It must be appreciated that in general, the effects of a drug on the body are governed by the effects of the body on that drug. Casual relationship between chemical entities of plant remedies and their toxicity remain hidden for the traditional healers and their patients. However capable these individuals may be able to detect gross symptoms of acute toxicity, such as abdominal cramps or phytotoxicity, it is open to serious question, whether they will ever recognize inconspicuous adverse events/reactions, such as carcinogenesis and teratogenesis or foetotoxicity (Nyazema, 1996). Admittedly traditional experience with herbal remedies may be a powerful tool in the detection of predictable and striking symptoms of acute toxicity. However, traditional experiences may be of little help in the recognition of harmful interactions with conventional drugs.
  
  These are some of the issues that have to be addressed in order to describe, explain, control and predict the side effects (both beneficial and adverse) and use of traditional herbal remedies, in a defined time, space and population. Great care has, therefore, to be taken in the ethnobotanical/pharmacological research. Precautions to be taken, particularly when trying to understand an adverse event/reaction due to herbal remedy, have been adequately described. Traditional experience mentioned above needs therefore to be supplemented with orthodox data from research and surveillance. Bearing in mind that herbal suppliers and traditional medical practitioners are not obliged to report suspected adverse reactions and when herbal procedures are of variable quality.
  
  From experience that has been gained so far in Zimbabwe the best way of amalgamating TM and SM interests is to gather field data. This requires anthropological skills, since it is difficult to judge the reliability and accuracy of an informant's report of a certain drug/herbal use, if one is unfamiliar with its cultural context. Sometimes traditional medical practitioners do not easily part with their information or they may deliberately supply you with material from the wrong plant. It is also necessary, however, to have an open eye for non-anthropological details. Supposing a traditional remedy for diabetes would cause weight loss, the therapy might well be a rational one, since non-insulin-dependent diabetes may be relieved by reducing obesity. However, when a field worker fails to note that people treated with the drug become less obese, the pharmacist evaluating the remedy might see little reason to perform a specific experiment on weight loss (Croom Jr., 1983). It is ideal to perform evaluation exercises at this level with a multi disciplinary team if funds permit. A well-qualified ethnobotanist, who combines anthropological abilities with botanical expertise, could do it on his own. The scientific identification of the plant used in phytotherapy, secured by a determinable voucher specimen, forms the indispensable hinge between field observation and experimental evaluation. This is particularly important if phytochemical and pharmacological studies are to be carried out in the future.
  
  It is important, however, to realize that if one wishes to begin a study of the chemical constituents of useful plants, one will find oneself collaborating with colleagues from a diverse range of academic fields such as, for example, pharmacognosy, ethnopharmacology and natural products chemistry.
  
  Pharmacognosy, the study of naturally occurring compounds - particularly those from plants - that can be used medicinally and in other ways, draws both upon biology and chemistry. From the beginning pharmacognosy focused on the identification, preparation and commercialization of drugs, the majority of which came from plants at that time. From this practical foundation, pharmacognosists have developed sophisticated techniques which allow them to isolate active principles, determine their chemical structure, understand the way they are produced in living organisms and show the effect they have on people. These researchers also explore ways of producing greater quantities of natural drugs through tissue cell culture, genetic manipulations and other technical methods.
  
  Ethnophamacology, on the other hand, places greatest emphasis on describing the medicinal properties in remedies used by local people. It also focuses on how they select, prepare and administer these curative plants and animals. This approach, which combines perspectives from chemistry, botany and anthropology, requires ethnopharmacologists to divide their time between the laboratory and the field. In order to select plants for chemical analysis, they interact with specialist plant users, such as herbalists, hunters and fishermen, who have developed an empirical knowledge of chemical compounds by tasting and smelling plants, observing the effects of medicinal herbs on patients and noting the link between the morphology and the curative powers of plants. Because of their close link to local people, some ethnopharmacologists seek to apply their knowledge and discoveries to improve health conditions in the communities in which they work.
  
  Whereas nutritional chemists measure the quantities of specific nutrients found in edible animals and plants in order to discover the extent to which they fulfill dietary requirements, they may focus on traditional foods consumed by local people, carrying out analyses of wild and managed edible plants not studied previously by other nutritionists.
  
  Finally, another groups that one may find important to collaborate with are natural products' chemists. They work on a broad range of biological compounds that include latex and resins employed in industrial process, essential oils used to make perfumes and other substances that have diverse applications. Chemists with a particular interest in agriculture focus on natural insecticides, as well as on the macronutrients found in plants used as 'green' fertilizer to enrich the soil. Other researchers study hallucinogenic and narcotic substances employed in ritual or recreation as well as naturally occurring poisons which people use for hunting, fishing and other activities.
  
  Although all focus on naturally occurring chemical compounds, these researchers exhibit different degrees of breathe in their academic formation and practical experience. However, they all would contribute to an effective strategy that may be developed in an attempt to find new biologically active constituents in plants.
  
  Strategy in the search for new biologically active constituents
  
  Plants of interest, based on ethnobotanical history, are collected, processed and tested in first tier bioassays, which are relevant to the therapeutic areas and analogous to the historical approaches utilized (Hambuger and Hostettman, 1991). The most promising initial leads are then processed further for phytochemical analyses where it is possible to obtain pure compounds in milligram amounts. Those products meeting in-vitro criteria, when compared against the best available therapeutics for comparison, are structurally characterized and subjected to confirmatory biological testing. The selection to proceed to animal testing or determination of safety efficacy is primarily based on structural novelty associated with confirmatory bioactivity. In some companies compounds that are able to lead to patent protection and have positive confirmatory bioassay results are than scaled up to provide gram quantities for animal testing. Compounds whose in-vivo activities compare favorably with the best available marketed therapeutics are significantly scaled up to provide hundreds of grams and proceed to detailed formulation. Not all plant products or herbal medicines are industrially processed. Those that are industrially processed become registered as medicinal product by the Medicines Control Authority of Zimbabwe, a drug regulatory body, in order to protect the public. Fig. 1 summarizes the process that has to be followed before a compound appears on the market as a drug or as a medicinal product.
  
  As has been stated earlier the approach adopted to obtain an exploitable pure plant constituent involves interdisciplinary work in botany, pharmacognosy, pharmacology, chemistry and toxicology. The approach can be formulated as follows:
  
  1. Selection, collection, botanical identification and preparation of plant material;
  2.Extraction with suitable solvents and preliminary analysis;
  3.Biological and pharmacological screening of crude extracts;
  4.Chromatographic separation of pure bioactive constituents, guided by bioassay
  (activity - guided fractionation);
  5.Structure determination/elucidation;
  6.Analysis and pharmacological profile of pure compounds;
  7.Toxicological testing;
  8.Partial or total synthesis.
  structure modification
  
  Although this is the best scientific approach of going about drug development, it takes a long time for a plant product to be available on the market. Many a time even if the drug becomes available on the market, it will always be beyond the reach of the very people who, gave the useful ethnobotanical information. This concern has been always expressed by consumers including traditional healers.
  
  The ethics of searching for new plant products
  
  There is increasing interest primarily by corporations of the North in the knowledge of indigenous peoples, primarily of the South. This interest has been fuelled by the growth of new technologies in genetic engineering and biotechnology and realization that industrial products of great commercial value can be made from the knowledge of indigenous peoples and local communities of biological resources using these technological advancements. The value of this knowledge has long been known. For example, as mentioned earlier in Chapter 1, of the 120 active compounds currently isolated from higher plants and widely used in modern medicine today, 75% show a positive correlation between their modern therapeutic use and the traditional use of the plant from which they were derived (Fransworth et al 1985). Sometimes the traditional use may have come about as a result of the Doctrine of Signature and Similitude found in all societies (Nyazema et al 1994). The use of traditional knowledge reportedly increases the efficiency of phytochemical screening of biologically active compounds (Balick, 1990). The value of the world market for medicinal plants derived from leads given by indigenous and local communities is rising. It is said to run into billions of US dollars.
  
  The Trade-Related Intellectual Property Rights (TRIPS in Appendix 3.1) provisions in GATT 1994 seek to globalize the dominant patent paradigm of the industrialized countries, mainly the USA. These provisions guarantee ownership rights to products made in the laboratories of the North from the knowledge of indigenous peoples and local communities. The knowledge system of these communities; their innovations in the intellectual commons; the societal and informal context in which they produce and innovate; and the purpose for which they do so - are all denied recognition. Only the North's industrial model of innovation is recognized. The cumulative collective system of innovation of traditional communities is excluded by definitions in TRIPs provisions.
  
  Therefore before beginning an ethnopharmacological project, there is need to consider the ethical implications. At present there is much debate about how the benefits from the marketing of new products derived from living organisms should be shared (Boom, 1990; Posey, 1990 a & b). Such products may be manufactured directly from materials in organisms, or be synthetic, but with their discovery based partly on studies of natural compounds in organisms. In Zimbabwe, like in most developing countries, the indigenous people have a knowledge base that stimulates the selection and screening of specific plant organisms.
  
  Commercial enterprises must therefore recognize the need to share benefits, including profits with the indigenous people. In addition, local people must be compensated for their intellectual contribution to discovering novel, plant-derived commodities (Appendix 3.2). Researchers, and everyone else involved in prospecting useful plants, share in the responsibility to ensure that the benefits get to the right people.

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