Journal of Ethnopharmacology 119 (2008) 342–355 Contents lists available at ScienceDirect Journal of Ethnopharmacology journal homepage: www.elsevier.com/locate/jethpharm Review A broad review of commercially important southern African medicinal plants B.-E. van Wyk ∗ Department of Botany and Plant Biotechnology, University of Johannesburg, P.O. Box 524, Auckland Park 2006, South Africa article info abstract Article history: Aims of the study: Commercially important indigenous medicinal plants of southern Africa are reviewed Received 8 May 2008 in the context of fundamental knowledge about their ethnobotany, phylogeny, genetics, taxonomy, bio- Received in revised form 14 May 2008 chemistry, chemical variation, reproductive biology and horticulture. The aim is to explore the rapidly Accepted 16 May 2008 increasing number of scientific publications and to investigate the need for further research. Available online 3 June 2008 Materials and methods: The Scopus (Elsevier) reference system was used to investigate trends in the number of scientific publications and patents in 38 medicinal plant species. Fifteen species of special Keywords: commercial interest were chosen for more detailed reviews: Agathosma betulina, Aloe ferox, Artemisia Biosystematics Chemical variation afra, Aspalathus linearis, Cyclopia genistoides, Harpagophytum procumbens, Hoodia gordonii, Hypoxis heme- Commercial development rocallidea, Lippia javanica, Mesembryanthemum tortuosum, Pelargonium sidoides, Siphonochilus aethiopicus, Medicinal plants Sutherlandia frutescens, Warburgia salutaris and Xysmalobium undulatum. Southern Africa Results: In recent years there has been an upsurge in research and development of new medicinal products Taxonomy and new medicinal crops, as is shown by a rapid increase in the number of scientific publications and patents. Despite the fact that an estimated 10% of the plant species of the world is found in southern Africa, only a few have been fully commercialized and basic scientific information is often not available. Conclusions: The limited available information indicates that some of the plants display remarkable regional variation in morphological, genetic and chemical characters that should be more thoroughly investigated. Basic biological information is needed to guide the rapidly accelerating commercialization process, especially the selection of superior clones, the development of new cultivars and the standard- ization of raw materials. © 2008 Elsevier Ireland Ltd. All rights reserved. Contents 1. Introduction ......................................................................................................................................... 343 2. Commercialized indigenous plant species ......................................................................................................... 343 3. Biosystematic and chemotaxonomic studies ....................................................................................................... 343 3.1. Agathosma betulina (P.J. Bergius) Pillans (Rutaceae)-round leaf buchu ..................................................................... 346 3.2. Aloe ferox Mill. (Asphodelaceae)-bitter aloe, Cape aloe ..................................................................................... 347 3.3. Artemisia afra Jacq. ex Willd. (Asteraceae)-wild wormwood ............................................................................... 347 3.4. Aspalathus linearis (Burm.f.) R. Dahlgren (Fabaceae)-rooibos tea ........................................................................... 347 3.5. Cyclopia genistoides (L.) R.Br. (Fabaceae)-honeybush tea ................................................................................... 348 3.6. Harpagophytum procumbens (Burch.) DC. ex Meissn. (Pedaliaceae)-devil’s claw .......................................................... 348 3.7. Hoodia gordonii (Masson) Sweet ex Decne (Apocynaceae)-hoodia, ghaap ................................................................. 348 3.8. Hypoxis hemerocallidea Fisch. & C.A. Mey. (Hypoxidaceae)-inkomfe, “African potato”..................................................... 348 3.9. Lippia javanica (Burm.f.) Spreng. (Verbenaceae)-fever tea.................................................................................. 349 3.10. Mesembryanthemum tortuosum L. [syn. Sceletium tortuosum (L.) N.E. Br.] (Mesembryanthemaceae)-sceletium, kougoed............... 349 3.11. Pelargonium sidoides DC. (Geraniaceae)-umckaloabo, rabas ............................................................................... 349 3.12. Siphonochilus aethiopicus (Schweinf.) B.L.Burtt (Zingiberaceae)-African ginger........................................................... 350 3.13. Sutherlandia frutescens (L.) R.Br. [syn. Lessertia frutescens (L.) Goldblatt & J.C.Manning] (Fabaceae)-cancer bush, sutherlandia ......... 350 3.14. Warburgia salutaris (Bertol.f.) Chiov. (Canellaceae)-pepperbark tree ...................................................................... 351 3.15. Xysmalobium undulatum (L.) W.T.Aiton (Apocynaceae)-uzara ............................................................................. 351 ∗ Tel.: +27 11 489 2412; fax: +27 11 489 2411. E-mail address: [email protected]. 0378-8741/$ – see front matter © 2008 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.jep.2008.05.029 B.-E. van Wyk / Journal of Ethnopharmacology 119 (2008) 342–355 343 4. Discussion ........................................................................................................................................... 351 Acknowledgements ................................................................................................................................. 351 References .......................................................................................................................................... 352 1. Introduction other important medicinal plant species is traded in large volumes on local markets but have as yet only been formally commercial- Africa, and especially southern Africa, has a rich diversity of ized to a limited extent. Several of the plants listed in Table 1 are plants. Recent statistics show that about 25% of the total number of endemic to southern Africa and some of them are treated in detailed higher plants in the world is found in Africa south of the Sahara. reviews in this volume. According to the “African Plant Checklist and Database Project” In order to gain some insight into the scientific and/or commer- (Klopper et al., 2006), a total of 50,136 angiosperm taxa occur in cial interest in South African medicinal plants, a literature search tropical Africa and southern Africa. This figure is based on a recent was conducted with the well-known Scopus literature reference merging of two major data bases—EPFAT (Enumération des plantes system maintained by Elsevier. Using the scientific names of the à fleurs d’Afrique) and FSA (Flora of southern Africa). The combined species and the “quick search” option, varying numbers of “hits” checklist shows a total of 32,424 taxa in tropical Africa and 22,755 were obtained for those species listed in Table 1. The searches were taxa in southern Africa. A useful reference book on the medicinal carefully executed to include main synonyms and other commercial plants of the whole of the African continent (Neuwinger, 2000) species of the same genus where relevant (e.g. Cyclopia). The results lists more than 5400 medicinal plant taxa and over 16,300 medic- are summarized in Table 2, which outlines the number of scientific inal uses. It is generally accepted (e.g. Geldenhuys and Van Wyk, publications and the number of citation in patents in recent years. 2002) that natural resources will play a major role in the socio- The general trend is one of an increasing number of papers and economic development of the African continent. The angiosperm citations since 1995, although this is not true for all the species. The species count for southern Africa (Germishuizen and Meyer, 2003) popularity of Centella asiatica and Withania somnifera in Ayurvedic is 21,817 and the count for the Cape Floristic Region (Goldblatt and medicine is reflected in the large number of citations and publica- Manning, 2001) is 8888. Van Wyk and Gericke (2000) estimated tions over many years. Relatively large numbers are also seen for that about 3000 medicinal plants are regularly used in southern those species that are well established in tropical Africa as impor- Africa. An annotated checklist of traditional medicinal plants of tant medicinal plants (e.g. Adansonia digitata, Kigelia africana and southern Africa (Arnold et al., 2002) gives a total of 3481 plant Prunus africana). These species have been of limited commercial taxa, of which 2942 are administered to people only. Basic infor- interest in South Africa despite their popularity elsewhere. mation about the most widely used species can be found in Van Table 2 reveals a rapid increase in the number of publica- Wyk et al. (1997), Van Wyk and Gericke (2000) and Diederichs tions and patent citations for several indigenous species that (2006). This diversity represents a very valuable resource, not only were scientifically practically unknown and unstudied prior to for commercial development but also for basic scientific study. 1995. Raw material of some species has only become available This paper is aimed at reviewing southern African medicinal in commercial quantities in recent years, so that the number of plants that are currently