PROTA, Introduction to Medicinal plants

Plant Resources of Tropical Africa Introduction

List of species

PROTA 11 (1), 2008. Plant resources of tropical Africa. vol. 11 (1). Medicinal plants, vol. 1. ed. by G.H. Schmelzer & A. Gurib-Fakim. Wageningen, PROTA Foundation - Backhuys - CTA. 869 p.

PROTA 11 (2), 2013. Plant resources of tropical Africa. vol. 11 (2). Medicinal plants, vol. 2. ed. by G.H. Schmelzer & A. Gurib-Fakim. Wageningen, PROTA Foundation - CTA. 417 p.

Choice of species of volume 1

PROTA 11(1): ‘Medicinal plants 1’ is the first volume of 4 describing the wild, and sometimes cultivated, plant species of tropical Africa traditionally used in local medicine. Some of these plants are not only used for human health care, but are also applied as veterinary medicine or as poisonous plants used as pesticide, fish poison or dart poison, and narcotic plants. Most species have several other, secondary, uses. PROTA normally assigns one primary use and if relevant, one or more secondary uses to all plant species used in Africa. For instance, the primary use of Voacanga africana Stapf is as a medicinal plant, and thus it is treated in PROTA 11, but it has several secondary uses, e.g. the branches are used in construction and to make musical instruments, the wood is used for firewood, good fibre for rope and yarn can be obtained from the bark and the fruits are considered edible. In Tanzania Voacanga africana is planted for ornamental purposes because of its sweet-scented white flowers. Pharmaceutical companies in Europe extract tabersonine from the seeds, which is readily converted into vincamine, a compound widely used in medicines for geriatric patients. Seed extracts are also used in medicines to treat heart diseases, to lower blood pressure and to treat cancer. Also Natal plum (Carissa spinarum L., synonym Carissa edulis (Forssk.) Vahl) is quite important as a medicinal plant, but its primary use is as a fruit, and consequently Natal plum is described in PROTA 6: ‘Fruits’.

The remaining ‘primary use’ medicinal plants will be included in tomes 11(2) to 11(4). In the final tome 11(4), the ‘secondary use’ medicinal plants will be listed as ‘Medicinal plants with other primary use’ and referred to other Handbook volumes. In PROTA 11, one species is treated which, in addition to the primary use as medicinal plant, also has another primary use and consequently will be described in 2 commodity groups. This species is Jatropha curcas L. (also in PROTA 14: ‘Vegetable oils’).

In this volume the medicinal plant species of several important medicinal plant-containing families are treated, the largest families being Apocynaceae, Asphodelaceae, Caesalpiniaceae, Euphorbiaceae, Loganiaceae, Menispermaceae and Solanaceae as well as 19 other families with few but important medicinal plants.

In PROTA 11(1): ‘Medicinal plants 1’ comprehensive descriptions are given of 134 important medicinal plant species. These major medicinal plants comprise most wild species, but also several cultivated or partly domesticated species. The accounts are presented in a detailed format and illustrated with a line drawing and a distribution map. In addition, accounts of 272 medicinal plants of minor importance are given. Because information on these species is often scanty, these accounts are in a simplified format and usually do not include a drawing or map. For another 491 species the medicinal information was too scarce to justify an individual treatment and they have only been mentioned in the accounts of related species. Each account will highlight traditional and modern uses, phytochemical and pharmacological properties, will make identification of useful species easier and more reliable, will describe most convenient collection (harvest), cultivation and application methods, and will indicate the research and conservation status of the plants.

About two third of the plant species used in tropical Africa have some documented medicinal use, but the actual number is probably higher. For PROTA 11, however, only species have been chosen for which proof was found in the literature on African useful plants that they actually are or have been used as a medicinal plant. Such literature, however, is scarce, often old and usually poor in details about the use. Only species for which at least a practical application is known have been considered for treatment. This means that species mentioned in the literature but only with remarks such as ‘the plant is medicinally used’ or ‘the roots are medicinally used’ have not been included.

In Sub-Saharan Africa, traditional medicine has been for centuries and still is the most affordable and accessible health care system. Medicinal plants contribute significantly to rural livelihoods of the people and social equilibrium in Africa. The demand of local and international markets is continuously growing, as well as bio-prospecting activities searching for sources of news drugs.

As a result of their widely and unsustainable use, increasing economic importance, and environmental factors, medicinal plants resources are diminishing at an alarming rate. Besides, the loss of indigenous knowledge on medicinal plants and traditional medicine is increasing, especially in Africa, as a result of death of the older people who have traditionally been the custodians of this knowledge, and the socio-cultural transformation of societies. This situation calls for policies and research programs, both at national and international levels, for conservation and sustainable use of medicinal plants, as well as for the protection of indigenous communities’s rights over the use of their traditional knowledge.

Choice of species of volume 2

PROTA 11(2): ‘Medicinal plants 2’ is the second volume of 4 describing the wild, and sometimes cultivated, plant species of tropical Africa traditionally used in local medicine. Some of these plants are not only used for human health care, but are also applied as veterinary medicine or as poisonous plants used as pesticide, fish poison or dart poison, and narcotic plants. Most species have several other, secondary, uses. PROTA normally assigns one primary use and if relevant, one or more secondary uses to all plant species used in Africa. For instance, the primary use of Terminalia avicennioides Guill. & Perr. is as a medicinal plant, and thus it is treated in PROTA 11(2), but it has several secondary uses, e.g. its wood is used in construction and for implements, as firewood and for charcoal production, and its foliage is used as forage and for dyeing cloth. The bark and leaves of Terminalia ivorensis A.Chev. are also used in traditional medicine, but the primary use of this species is as a timber tree, and consequently it is described in PROTA 7(2): ‘Timbers 2’.

The remaining ‘primary use’ medicinal plants will be included in volumes 11(3) and 11(4). In the final tome 11(4), the ‘secondary use’ medicinal plants will be listed as ‘Medicinal plants with other primary use’ and referred to other Handbook volumes.

In this volume the medicinal plant species of the families Asclepiaceae, Balanophoraceae, Capparaceae, Combretaceae, Convolvulaceae, Physenaceae and Rutaceae are treated, as well as Dichrostachys cinerea (L.) Wight & Arn. (Mimosaceae) which has been added because the article was already available although other Mimosaceae species with medicinal usage will be treated in volume 11(3).

In PROTA 11(2): ‘Medicinal plants 2’ comprehensive descriptions are given of the 146 most important medicinal plant species, comprising mainly wild species but also some cultivated or partly domesticated species, and illustrated with a distribution map and sometimes also line drawing. For another 263 species the medicinal information was too scarce to justify an individual treatment and they have only been mentioned in the accounts of related species. Each account will highlight traditional and modern uses, phytochemical and pharmacological properties, will make identification of useful species easier and more reliable, will describe most convenient collection (harvest), cultivation and application methods, and will indicate the research and conservation status of the plants.

About two third of the plant species used in tropical Africa have some documented medicinal use, but the actual number is probably higher. For PROTA 11, however, only species have been chosen for which proof was found in the literature on African useful plants that they actually are or have been used as a medicinal plant. Such literature, however, is scarce, often old and usually poor in details about the use. Only species for which at least a practical application is known have been considered for treatment. This means that species mentioned in the literature but only with remarks such as ‘the plant is medicinally used’ or ‘the roots are medicinally used’ have not been included.

In Sub-Saharan Africa, traditional medicine has been for centuries and still is the most affordable and accessible health care system. Medicinal plants contribute significantly to rural livelihoods of the people and social equilibrium in Africa. The demand of local and international markets is continuously growing, as well as bio-prospecting activities searching for sources of news drugs.

As a result of their widely and unsustainable use, increasing economic importance, and environmental factors, medicinal plants resources are diminishing at an alarming rate. Besides, the loss of indigenous knowledge on medicinal plants and traditional medicine is increasing, especially in Africa, as a result of death of the older people who have traditionally been the custodians of this knowledge, and the socio-cultural transformation of societies. This situation calls for policies and research programs, both at national and international levels, for conservation and sustainable use of medicinal plants, as well as for the protection of indigenous communities’ rights over the use of their traditional knowledge.

Plant names

Family: Apart from the classic family name, the family name in accordance with the Angiosperm Phylogeny Group (APG) classification is also given where it differs from the classic name.

Synonyms: Only the most commonly used synonyms and those that may cause confusion are mentioned.

Vernacular names: Only names in official languages of regional importance in Africa are included: English, French, Portuguese and Swahili. It is beyond the scope of PROTA to give an extensive account of the names of a species in all languages spoken in its area of distribution. Checking names would require extensive fieldwork by specialists. Although regional forms of Arabic are spoken in several countries in Africa, the number of African plant species that have a name in written, classical Arabic is limited. Arabic names are therefore omitted. Names of plant products are mentioned under the heading ‘Uses’.

Origin and geographic distribution

To avoid long lists of countries in the text, a distribution map is added for all species. The map indicates in which countries a species has been recorded, either wild or planted. It should be realized that for many species these maps are incomplete because they are prepared on the basis of published information, the quantity and quality of which varies greatly from species to species. This is especially the case for wild species which are not or incompletely covered by the regional African floras, and for cultivated species which are only planted on a small scale (e.g. in home gardens). For some countries (e.g. Central African Republic, Chad, Sudan, Angola) there is comparatively little information in the literature. Sometimes they are not covered by recent regional or national floras and although species may be present there, this cannot be demonstrated or confirmed. For some major species, a distribution map has been omitted because there is too little information on distribution.

Properties

The phytochemistry of the different plant parts is given, with emphasis on the bioactive compounds. Where possible, a link is made between the traditional uses of a plant part, the active compounds isolated from it and pharmacological tests confirming or not confirming the activity of these active compounds, or of the plant extracts containing active compounds.

Description

A morphological characterization of the species is given. The description is in ‘telegram’ style and uses botanical terms. Providing a description for the general public is difficult as more generally understood terms often lack the accuracy required in a botanical description. A line drawing is added for a number of species to complement and visualize the description.

Management

Descriptions of husbandry methods including fertilizer application, irrigation, and pest and disease control measures are given under ‘Management’ and under ‘Diseases and pests’. These reflect actual practices or generalized recommendations, opting for a broad overview but without detailed recommendations adapted to the widely varying local conditions encountered by farmers. Recommendations on chemical control of pests and diseases are merely indicative and local regulations should be given precedence. PROTA will participate in the preparation of derived materials for extension and education, for which the texts in this volume provide a basis, but to which specific local information will be added.

Genetic resources

The genetic diversity of many plant species in Africa is being eroded, sometimes at an alarming rate, as a consequence of habitat destruction and overexploitation. The replacement of landraces of cultivated species by modern cultivars marketed by seed companies is another cause of genetic erosion. Reviews are given of possible threats for plant species and of the diversity within species, and reference is made to the IUCN Red list of threatened species where relevant. Information on ex-situ germplasm collections is mostly extracted from publications of Bioversity International (formerly the International Plant Genetic Resources Institute – IPGRI).

References

The main objective of the list of references given is to guide readers to additional information; it is not intended to be complete or exhaustive. Authors and editors have selected major and other references; ‘major references’ are limited to 10 references, the number of ‘other references’ is limited to 20. The references listed include those used in writing the account. Where the internet was used, the website and date are also cited. Where data available on the internet have been used, the website and date are also cited.

• G.H. Schmelzer, PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
• A. Gurib-Fakim, Faculty of Science, University of Mauritius, Réduit, Mauritius

• C.H. Bosch, PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
• M.S.J. Simmonds, Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AB, United Kingdom
• R. Arroo, Leicester School of Pharmacy, Natural Products Research, De Montfort University, The Gateway, Leicester LE1 9BH, United Kingdom
• A. de Ruijter, PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

• R.H.M.J. Lemmens, PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
• L.P.A. Oyen, PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands