UTILIZATION AND CONSERVATION OF MEDICINAL PLANTS IN AFRICA

• UTILIZATION AND CONSERVATION OF MEDICINAL PLANTS IN AFRICA
  
  Dr. Charles M. Nshimo,
  Senior Lecturer, Faculty of Pharmacy
  Muhimbili University College of Health Sciences
  P.O. Box 65022, Dar es Salaam, Tanzania.
  Tel. 255- 051-151244.
  Fax 255-015-151244,
  
  Email: plan@muchs.ac.tz
  
  ABSTRACT
  
  Traditional medicine in Africa is still an important health provider to the majority of the people in rural areas. Plants commonly used in traditional medicine are being over harvested and are disappearing. Better utilization of plants lies in educating traditional healers and contemporary researchers on proper exploitation of medicinal plants. Methods of propagation of indigenous plants must be thought for continuation of the practice and drug industry. Collaboration between traditional healers and modern doctors should be emphasized. Traditional healers should be screened for knowledge of diagnosing for the diseases they claim to treat. Only those who can, are then asked for the plants they use which can be good leads in the discovery programs. As collaborators, traditional healers should eventually benefit in case of any discovery from the information they give. Apart from pharmacological screening for the claimed activity, a general screening should also be conducted on the medicinal plants in order to discover other new activity. Drugs in form of galenicals should be preferred to pure compounds where necessary.
  
  INTRODUCTION
  
  Tanzania, like most African countries can not satisfy the needs for modern drugs to its people because the cost of imported drugs is almost prohibitive. On the other hand the country has an enormous wealth of information of medicinal plants which are not only cheap and abundant but also culturally acceptable. The World health organization estimates that 80% of the people in developing countries are totally dependent on traditional medicine as a source of their health care (1). Traditional medicine in Tanzania is therefore an important form of primary health care for the majority of the people especially those living in the rural areas. One of the necessary goals for the success of primary health care, is the availability and use of suitable drugs.
  
  Plants have always been a common source of medicaments either in form of traditional preparations or as pure active principles. It is therefore necessary to identify the locally available plants for extract that could be added to the national list of drugs, or that could even replace those pharmaceutical preparations that need to be imported. Little regard however, has been given to plants potentially useful in traditional medicine. As a result they are declining rapidly due to habitat destruction like logging, fuel wood consumption, cattle ranching, forest farming and over exploitation. Contemporary research in traditional medicine is heavily oriented towards medicinal plants such that once an abundant plant used in traditional medicine is published to have medicinal value, a ruthless search for the plant is started and ends only when the plant is no longer found. Plants most commonly used by traditional healers are over harvested to a point of extinction. An example is that of two plants, securidaca longipenduculata Fren and Euphorbia quadrangularis pax. Which two decades ago were abundant in Mwanza and Shinyanga regions in Tanzania, but due to their usefulness in treating infertility and general body weakness respectively, the plants have been over harvested to a point that they are at present rare in the regions. They are now at traditional healers' home compounds where they are grown and protected for use in traditional healing practice.
  
  The importance of conservation of medicinal plants.
  
  Plants are a recognized source of prescription drugs, non prescription drugs, herbal remedies, spices, sources of edible oils, pharmacology probes for scientific research, insecticides and plant hormone regulators (2).
  
  Plant parts most commonly used by traditional healers are the roots and barks. Tree barks are usually rich in secondary metabolites partly accounting for their popularity as a source of drugs in traditional medicine. The phloem part of the bark is the principal food conducting tissue of the vascular plants and the root constitutes the underground part of the plant axis specialized as an absorbing and anchoring organ (3). Since both organs are essential for plant survival, unskilled debarking and cutting of roots from medicinal plants, should be condemned outright.
  
  Authorities in Africa may not be aware of the importance that is now being placed by pharmaceutical companies and environmentalists elsewhere on the study and conservation of plants as a source of medicinally active agents. At present for example, there are more than 121 useful prescription drugs containing chemical compounds of known structure, obtained from higher plants that are used throughout the world (4). Most of the flora in Tanzania has not been studied for its biological activity as a consequence plants which become extinct before they are studied, a cure for diseases like some forms of cancer and AIDS etc., which has not been found may have been lost with it. Research into new drugs for these diseases is continually turning to traditional medicine. There is therefore an urgent need to identify and protect plant species used in traditional medicine. This is necessary for the continuation of the practice and the drug industry. An urgent step to be taken in order to protect plants from unnecessary exploitation is for Africa to start a Database for medicinal plants. All aspects of research into African plants especially those used in traditional medicine, say since 1970, be entered into the database. The information should then be made available to all researchers interested in working on plants in Africa. The move will prevent unnecessary duplication of research work and therefore protect plants from further collection destruction. Research can then be concentrated on plants that have not been studied in terms of biological activity and chemical constituents before they become extinct.
  
  Propagation and domestication of plants in Africa
  
  Due to uncontrolled harvesting of medicinal plants by traditional healers, it is now rare to find an abundance of popular medicinal plants. One must travel long distances looking for medicinal plants that a decade ago used to be in his/her neighborhood. It is now very common for example, for traditional healers migrating from one region to another n search of indigenous forests where medicinal plants are still found. A lot of areas are turning into deserts and governments are now aware of the hazard. A campaign for planting trees has been launched, but not for the disappearing medicinal plant species. Forestation is being done through planting trees from nurseries most of them being exotic, not indigenous to the areas. In a few years the countries will turn green with trees but will be of no use to traditional healers and the practice of traditional medicine. Methods of propagation of indigenous medicinal plants in areas where they existed should be emphasized while educating traditional healers by way of seminars, workshops, etc., on proper exploitation of existing medicinal plants.
  
  Protection of traditional medicine
  
  The practice of traditional medicine in Tanzania is an old profession like other professions. There must be a truth in traditional healing otherwise nobody would pay a traditional healer some money seeking for his help if there was no real cure otherwise traditional healers would have ceased to exist. It is therefore a source of income for these people. Not everybody can become a traditional healer. The way it goes, at least from my experience, an old traditional healer selects his successor from one of his/her children or a close relative like a grand child. The favored one is then privately trained the norms of traditional healing for many years before he/she becomes a traditional healer and only after the death of the old traditional healer. He/she always accompanies the traditional healer to the forests for plant collection. Secrecy is always emphasized. No traditional healer would like somebody else to know the plants he/she uses in treating his/her patients. This is partly the reason why research in traditional medicinal plants through interview with traditional healers in certain cases has been disappointing. Some success into medicinal plants has however been obtained through folk medicine where a person who has initially had experience with a useful drug effect from a plant extract relates this information to another person. The only problem with this system is being more susceptible to variation and distortion of information during its passage from person to person.
  
  Traditional healers should therefore be allowed to practice officially. The important thing they should be made to accept is for them to be given special training in hygiene, standardization of herbal portions and dosage according to age and weight.
  
  Discovery of drugs from traditional medicine
  
  In order for research into traditional medicine to succeed, traditional healers must be convinced on the importance of their collaboration with modern doctors for the common good of the patient. They should also be assured of future benefits in case of a discovery as a result of the information they give. For those who accept to collaborate and are prepared to reveal the medicinal plants they use, a competent doctor can interview the healers on how they diagnose their patients for the diseases they claim to treat. Only those traditional healers who correctly describe symptoms for the diseases are included into the collaboration, and asked to show the plants they use for treating the diseases. The plants are then collected and screened for the pharmacological activity. Where activity is confirmed economic dosage forms are developed for use in health care. Isolation of pure compounds is an expensive process. In some cases though depending on the activity, isolation of the active ingredient(s), structure elucidation and modification are necessary before a suitable dosage form is considered.
  
  It is however not a comprehensive screening to test for the pharmacological activity claimed by traditional healers alone. The basic premise of pharmacological screening is not to allow true biologic activity to go undetected even though the activity may be new, unexpected and unique. Digitalis for example, was originally classified by folklore as a diuretic. When tested in a general screen of the type of Hippocratic screen for Pure or Crude Drug Materials, digitalis produced dramatic activity that established it as a possible cardiotonic agent. An important initial screen must be designed to be unbiased, general in scope and comprehensive rather than being specifically directed to detect one particular type of activity. It is also important that the initial screen must be reliable and produce reliable results (5). Apart from screening medicinal plants for the claimed pharmacological activity alone, the above general method for screening plant extracted should be carried out for detecting of new and unique activities.
  
  For the above to be possible, scientists in Africa must be enthusiastic, energetic and highly motivated to organize and implement interdisciplinary research programs for cheaper utilization of natural resources of drugs. These sources are usually available in abundance and can provide safe, stable and effective galenical products. The products have an advantage over pure compounds of being effective and cheap to prepare. For example, chemically standardized tincture of Atropa Belladonna for use in treating stomach ulcers, has a therapeutic efficacy at least equivalent to that of a standardized dose of atropine sulphate (the major ingredient of A. Belladonna). The manufacture of a stable standardized tincture would be cheaper than importation of atropine tablets (2). The alkaloid reserpine, can be commercially extracted from natural sources for about $0.75/kg while its synthesis would cost about $1.25/kg, so it is obvious that natural sources for this drug is cheaper (4). Practical industrial synthesis for such important drugs such as digoxin and digitoxin are not available.
  
  
  
  The Tanzania Situation
  
  
  
  Tanzania is estimated to have about 60,000 traditional healers, the majority of which live in rural areas where the majority of the population is (6). It has about 1800 modern doctors mostly located in urban areas. Therefore traditional medicine is likely to dominate in the near future due to its affordability, uses locally available and culturally acceptable remedies, readily available and efficient traditional healer's network.
  
  The Tanzanian government recognized the importance of traditional medicine in the country to an extent that in 1974 an Institute of Traditional Medicine was established in the Muhimbili University College of Health Sciences. The main objectives of the institute are to promote field ethnobiomedical data collection from traditional healers, traditional birth attendants and communities. Documentation and storage of information and materials pertaining to all aspects of traditional medicine enhance phytochemical and pharmacological screening of potential medicinal substances in plants, animal parts and mineral substances. Other objectives include intensification of anthropological work to retrieve, document and store information pertaining to the customs and traditional practices in traditional medicines. Initiate and promote clinical trials on promising traditional medicines and furtherance of utilization of traditional practice in the country. The other objective is to promote conservation of medicinal and aromatic plants through in-situ and ex-situ conservation strategies and disseminate research information on national, regional and international level.
  
  Plants found to be of potential medicinal value are, in collaboration with the Faculty of Pharmacy, formulated for use as part of the drug supply in the health care system.
  
  Conclusion
  
  Plants are important to traditional healers and the future well being of traditional medicine. It is also a cheap source of drugs in pharmaceutical industries in Africa. Stern measure must be taken to protect the vulnerable species from extinction. The formation of a database for plants that have already been studied is essential so that research can be concentrated on plants that have not been worked on. The success of research in the development of new drugs from plants needs the cooperation of traditional healers in revealing the plants they use in their practice. However they must be motivated to reveal their secrets. Governments should recognize the importance of traditional medicine as part of primary health care.
  
  Medicinal Plants Used by the Majority of the population and frequently cited by most of traditional healers
  
  Plant Family Part used Vernacular name Uses
  
  1. Cassis didymobotria L. Leguminosae Leaves Njolwa mbogo Anemia, Athlemintic, laxative
  
  2. Ficus stulhmanii Walp. Moraceae Stem bark nkuyu Treats chronic wounds
  
  3. Harrisonia abysinica Oliv. Simaroubaceae Roots Bulatula Bilharzia, chronic wounds
  
  4. Terminalia serica Burch. Combretaceae Roots Njima Diarrhea, vomiting, stomach problems
  
  5. Securidaca longipenduculata Polygalaceae Roots Nengonengo Treats infertility in both men and
  
  Fren women
  
  6. Euphporbia quadrangularis Euphorbiaceae Arial parts Lonzwe General body weakness
  
  Pax.
  
  7. Entada abyssinica Steud. Mimosaceae Root bark Nfutwa mbula Chronic cough, headache, stomach pains
  
  8. Albizia vesicolor Welw. Mimosaceae Root bark Ntindwa nzagamba Anemia, Athlemintic, sterility in women
  
  9. Strychino heterodoxa Gilg. Loganiaceae Roots Mpande pande Inflammations and fevers
  
  10. Gnidia kraussiana Thymilaeaa Tuber Kafulungusha Constipation, swollen stomach
  
  
  REFERENCES
  
  1. Balandrin, M.F., J.A., Wurtele, E.S., and Bollinger, W.H.: Natural Product Chemicals: Sources of Industrial and Medicinal Materials. Science. 228: 1154-1160,1985
  
  
  2. Farnsworth, N.R., Akerele, O., Binger, A.S. and Guo, G.: Medicinal Plants in Therapy. Bulletin WHO 63(6) 965-981. 1981
  
  3. Esau, K.: Plant Anatomy. Second Ed. John Wiley & Sons. New York, Chicester, Brisbane, Toronto. 270-304. 1965.
  
  4. Farnsworth, N.R. and Morris, R.W.: Higher Plants - the sleeping giant of drug development. Am. J. Pharm. 147 (2) 46-52, 1976.
  
  5. Malone, M.H. and Robichaud, R.C.: Hippocratic Screen for Pure of Crude Drug Materials. Lloydia 25: 320-332 1962
  
  6. Weenan, H., Nkunya, M.H.H., Bray, D.H., Mwasumbi, L.S., Kinabo, L.S. and Kaimali, V.A.EB: Antimalarial Activity of Tanzanian Medicinal Plants. Planta Medica 56: 368-370. 1990.

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