A review of commercially important African medicinal plants

Data on the relative importance and research status of commercially relevant African medicinal plants are needed for developing new research strategies in order to stimulate much-needed ethnopharmacological research and to promote the commercialization of African plants.

To present an illustrated bird's eye view and comparative analysis of the relative popularity and importance of commercialized African medicinal plants. A comparison is made between the general popularity and commercial importance of the species (as indicated by their footprint on the World Wide Web) and their scientific popularity and importance (as indicated by the number of research publications). The inventory and review is strongly focussed to cover all or most of the medicinal plant raw materials in the international trade that are exported from African countries, with less emphasis on those that are regularly traded on local and regional markets within Africa.

The review is based on literature data, Scopus and Google searches, commercial information and the author's own experience and observations.

More than 5400 plant species are used in traditional medicine in Africa, of which less than 10% have been commercially developed to some extent. Africa is home to more than 80 valuable commercial species that are regularly traded on international markets, including phytomedicines (e.g. Harpagophytum procumbens and Pelargonium sidoides), functional foods (e.g. Adansonia digitata and Hibiscus sabdariffa) and sources of pure chemical entities (e.g. caffeine from Coffea arabica and yohimbine from Pausinystalia johimbe). According to the Scopus results, about 60% of all recent publications on African medicinal plants appeared in the last decade, with an average of 280 papers (28 per year) for 85 prominent species of international trade. The most popular African species for research (number of publications in brackets) were: Ricinus communis (5187), Aloe vera (2832), Catharanthus roseus (2653), Sesamum indicum (2534), Strophanthus gratus (2514), Coffea arabica (2431), Citrullus lanatus (2215), Momordica charantia (2047), Withania somnifera (1767), Trigonella foenum-graecum (1687), Acacia senegal (1373), Centella asiatica (1355), Griffonia simplicifolia (1010), Hibiscus sabdariffa (987), Tamarindus indica (973) and Catha edulis (947). The top species in terms of recent research interest (% of publications in last decade) were: Hoodia gordonii (95%), Cyclopia genistoides (93%), Sceletium tortuosum (90%), Agathosma betulina (89%), Pelargonium sidoides (86%), Boswellia papyrifera (85%), Lessertia (Sutherlandia) frutescens (84%), Boswellia sacra (83%), Mondia whitei (81%), Hibiscus sabdariffa (80%), Hypoxis hemerocallidea (80%) and Tylosema esculentum (80%). Both lists reflect the recent interest in functional foods and dietary supplements.

Despite a marked recent increase in the number of publications on indigenous medicinal plants and dietary supplements, Africa lags behind Europe and Asia in terms of the number of products that have been commercialised and the percentage of the flora that is utilized for international trade. There is a tremendous potential for developing new crops and new products but much work remains to be done to generate more focussed and relevant pre-clinical data and convincing proof of concept through clinical studies.