Medicinal plants: An invaluable, dwindling resource in sub-Saharan Africa.

Journal of Ethnopharmacology ∎ (∎∎∎∎) ∎∎∎–∎∎∎

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Contents lists available at ScienceDirect

Journal of Ethnopharmacology journal homepage: www.elsevier.com/locate/jep

Medicinal plants: An invaluable, dwindling resource in sub-Saharan Africa Mack Moyo, Adeyemi O. Aremu, Johannes Van Staden 1 Research Centre for Plant Growth and Development, School of Life Sciences, University of KwaZulu-Natal, Pietermaritzburg, Private Bag X01, Scottsville 3209, South Africa

art ic l e i nf o

a b s t r a c t

Article history: Received 5 February 2015 Received in revised form 17 April 2015 Accepted 19 April 2015

Ethnopharmacological relevance: The use of plant species for different therapeutic/medicinal purposes is well-entrenched in sub-Saharan Africa. Aim of the review: To provide a critical and updated review of the enormous medicinal plant heritage in sub-Sahara Africa with regards to the abundance, importance, conservation status and potential means to help sustain their availability for future generations. Methods: A comprehensive literature search involving different online databases, books and thesis were conducted in order to obtain, collate and synthesize available information on various fundamental aspects pertaining to African medicinal plants. Results: African biodiversity hotspots are endowed with a high level of endemic species with a significant portion possessing medicinal value. Apart from the extensive ethnobotanical uses of medicinal plants found in Africa, scientific validation of their biological potential such as antimicrobial, antioxidant, anti-inflammatory, anti-diabetic properties have been recognized. Together with the demand arising from their biological efficacies, other anthropogenic factors are exerting conservation strains of the wild population of these medicinal plants. Even though researchers have acknowledged the importance and value of conserving these medicinal plants, several challenges have hampered these efforts on the Continent as a whole. Conclusions: The rich flora occurring in sub-Saharan Africa suggests enormous potential for discovery of new chemical entity with therapeutic value. However, concerted efforts focused on documenting the conservation status of African medicinal plants are pertinent. Application of different biotechnological techniques is needed to sustain these valuable botanical entities, especially to meet increasing pharmaceutical demand. Most importantly, increased public enlightenment and awareness may help eradicate the prejudice against cultivation of medicinal plants. & 2015 Published by Elsevier Ireland Ltd.

Keywords: Biodiversity Biotechnology Conservation Cultivation Ethnobotany Herbal medicine Micropropagation

1. Introduction Despite the unavailability of supporting empirical data (Quiroz et al., 2014), the statement that ‘80% of the continent's population depends on herbal medicine for their primary health care’ (Dold and Cocks, 2002; Fomogne-Fodjo et al., 2014; Ibrahim et al., 2014; Jäger et al., 1996; Jusu and Sanchez, 2013c; McMillen, 2012; Mulholland, 2005; Olorunnisola et al., 2015; Orwa et al., 2008; WHO, 2002; Yemele et al., 2015; York et al., 2011) has almost become synonymous with African ethnobotanical and ethnopharmacological literature. Based on this statistic, the rationale for many ethnopharmacological studies has been that a large proportion of the African population

E-mail address: [email protected] (J. Van Staden). Tel.: þ27 33 2605130.

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depends on medicinal plants for their primary health care needs (van Andel et al., 2012). According to Pouliot (2011), researchers and policymakers still rely on outdated estimates because recent quantitative data on the use of medicinal plants do not exist. Notwithstanding, it is undeniable that medicinal plants have played a pivotal role in primary health care in Africa for centuries. Significant pharmacological research has been done to validate the use of plant extracts as medicinal remedies in sub-Saharan Africa (Moyo et al., 2015). The rich history of African cultures and their innovative utilization of plants as a source of remedies have been passed down through generations largely by oral tradition (Soelberg et al., 2015). Besides the gradual loss of ethnobotanical knowledge due to lack of documentation, most authors have highlighted the overharvesting of medicinal material from their natural habitat as one of the major threats to the preservation of traditional medicine. In order to conserve wild plant species, there is a need for reliable

http://dx.doi.org/10.1016/j.jep.2015.04.034 0378-8741/& 2015 Published by Elsevier Ireland Ltd.

Please cite this article as: Moyo, M., et al., Medicinal plants: An invaluable, dwindling resource in sub-Saharan Africa. Journal of Ethnopharmacology (2015), http://dx.doi.org/10.1016/j.jep.2015.04.034i

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M. Moyo et al. / Journal of Ethnopharmacology ∎ (∎∎∎∎) ∎∎∎–∎∎∎

data on their distribution and level of use (Ahrends et al., 2011). In many parts of Africa where some studies have been conducted, there are few signs of unsustainable harvesting of medicinal plants, for example reduction in the size of bulbs and other traded plant parts (Williams et al., 2007a), erratic and irregular supply of certain plants at medicinal markets, and increasing distances to harvesting sources (Towns et al., 2014; Williams et al., 2013). In light of the perceived increase in demand of medicinal plants for both the local and international markets, it is imperative for African countries to assess the conservation status of their flora using the standard IUCN Red List Categories. To date South Africa is the only country in the world that has assessed the threat statuses of its entire flora based on the IUCN Red List guidelines but with additional categories, namely, Critically Rare, Rare and Declining (Williams et al., 2013). Medicinal market quantitative surveys can provide a credible source of baseline data on volumes of traded plant species, estimated magnitude of wild population depletion and sustainability of harvesting (Williams et al., 2007a). In their study of medicinal geophytes traded in South African medicinal markets, Williams et al. (2007a) proved that the size of bulbs sold had significantly decreased between 1995 and 2001. Such studies generate valuable data on the magnitude of trade and medicinal plants most at risk of overharvesting, which can contribute to species specific conservation measures. This provides important baseline information for threat and conservation status assessments of medicinal taxa. In this review we highlight the rich floral biodiversity found in Africa, the overexploitation of medicinal plants and their conservation statuses according to the IUCN Red List Categories. In order to ensure and guarantee continuous benefits, we also discuss the currently available and viable methods with potential to help sustain the overall African rich medicinal flora. Even though more than 5400 medicinal plants are recognized and documented in Africa (Iwu, 2014; Neuwinger, 2000), the main emphasis in the current review was on the 51 plant species (from 30 families) published in the African Pharmacopeia and deemed to be the most important on the Continent (Brendler et al., 2010). Nevertheless, other valuable medicinal plant species not captured in the African Pharmacopeia were also highlighted where necessary.

2. Floristic richness and biodiversity hotspots in Africa The botanical diversity in different parts of the African continent and the inherent ethnobotanical knowledge has been the mainstay of localized traditional herbal medicine systems for thousands of years. However, the globalization of medicinal plants has increasingly exposed these local plant resources to overexploitation, leading to the extinction of some important species. Today, most medicinal plants remain locally-derived, but are utilized internationally. Plants originating from Africa constitute about 8% of the 1100 medicinal plants commercialized globally (Brendler et al., 2010). The increasing commercial value of products from African plants, often available as processed materials in modern packaging and in various dosage forms including teas, tinctures, tablets, capsules and ointments has been critically reviewed (Amoo et al., 2014b; Dzoyem et al., 2013; Mahomoodally, 2013; Makunga et al., 2008; Mncwangi et al., 2012; Moyo and Van Staden, 2014; Stewart and Cole, 2005; Van Wyk, 2008; Vermaak et al., 2014). The richness of medicinal plant resources in Africa emanates from the vast floral diversity found across the continent, particularly the eight biodiversity hotspots (Table 1). Globally, about 44% of all vascular plant species are confined to only 1.4% of the earth's land surface area (Myers et al., 2000), depicting the high level of floral richness. Biodiversity hotspots in Africa, namely, the Succulent Karoo, Maputaland Pondoland Albany, Cape Floristic Region, Madagascar

and the Indian Ocean Islands, the Horn of Africa, the Guinean Forests West Africa, Coastal Forests of Eastern Africa and the Eastern Afromontane region, are characterized by unique floral richness and high levels of endemism (Table 1). The Succulent Karoo, which primarily consists of winter rainfall desert and the newly recognized Horn of Africa are the only two hotspots that are entirely arid (CEPF, 2003). However, unlike the Succulent Karoo which has been wellcharacterized, taxonomic research of the Horn of Africa flora is still largely incomplete and ongoing. According to Ahrends et al. (2011) declining resources for basic biodiversity inventories have affected the tropical regions particularly hard, thus their flora remains severely understudied. The highest level of endemism (89.2%) is found in the Madagascar hotspot with 11 endemic plant families, 310 plant genera and 11,600 plant species (Myers et al., 2000). Based on the level of species endemism, endemic species/area ratios and habitat loss, Madagascar has been classified as the hottest hotspot in the world (Myers et al., 2000). Understandably, one of the major concerns is the loss of Malagasy medicinal plants due to anthropogenic activities from areas that have not yet been explored (Norscia and Borgognini-Tarli, 2006). A similar trend of extensive unique and sharply distinct flora occurs in the Cape Floristic Region with 69% endemism and which holds five of South Africa's 12 endemic plant families and 160 endemic genera (CEPF, 2001; Onstein et al., 2014). It is interesting to know that despite the sustained taxonomic research over the past few decades, new plant species (Magee and Manning, 2010; Muasya et al., 2012; Powell and Magee, 2013) are still being identified and described in the Cape Floristic Region. The floristically complex Maputaland Pondoland Albany hotspot, consists of 39 endemic vascular plant genera, and has significant numbers of ‘Critically Endangered' (83), ‘Endangered’ (128) and ‘Vulnerable’ (323) species (CEPF, 2010). The hotspot's warm temperate forests have a high tree richness of nearly 600 species and a remarkable stem succulent flora (CEPF, 2010). In the Coastal Forests of Eastern Africa hotspot, about 43%of the plant species and 2%of genera are estimated to be endemic (Lovett, 1998a,b,c). Compounding the fragility of this ecosystem is the fact that about 70%of the endemic species and 90%of endemic genera are found in forest habitants (Lovett, 1998c). On the other hand, the mountains of the Eastern Afromontane hotspot though geographically disparate and widely scattered along the eastern edge of Africa, have remarkably similar flora (Lovett, 1998c). The area includes the Eastern Arc Mountains, the Ethiopian Highlands, Tanzanian Highlands and the Chimanimani Highlands in eastern Zimbabwe. Relatively fewer ethnobotanical studies have been undertaken in this region, despite the extraordinary high degree of botanical diversity with some areas reportedly harbouring 3000–4000 plant species per 10,000 km² (Schlage et al., 2000). Furthermore, Schlage et al. (2000) concluded that relatively few of the medicinal taxa found in the Usambara Mountains of the Eastern Arc Mountains have been phytochemically and pharmacologically characterized in detail. Remarkably, the Eastern Arc Mountains is endowed with enormous richness and diversity comprising about 40 endemic plant genera and more than 1100 plant species (CEPF, 2012). The Guinean Forests of West Africa hotspot is also composed of an extensive array of unique plants, including approximately 1800 endemic species.

3. The over-exploitation of medicinal plants in sub-Saharan Africa The scramble for medicinal plants for local trade and utilization has been recorded in different parts of the continent for many years. As far back as 1946, Jacob Gerstner, a missionary in South Africa predicted the imminent extinctions of ‘doomed’ medicinal plants (Gerstner, 1946; Williams et al., 2013). In particular, Gerstner (1946) highlighted the overexploitation of Warburgia


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Table 1 Floristic richness in biodiversity hotspots in Africa (CEPF, 2015). Biodiversity hotspot

Original size (km²)

Hotspot vegetation remaining (km²)

No. of species

No. of endemic species

Endemism (%)

Coastal forests of East Africa Eastern Afromontane Guinean Forests of West Africa Horn of Africa Madagascar and Indian Ocean Islands Maputaland-Pondoland-Albany Succulent Karoo The Cape Floristic Region

291,250 1,017,806 620,314 1,659,363 600,461 274,136 102,691 78,555

29,125 106,870 93,047 82,968 60,046 67,163 29,780 15,711

4000 7600 9000 5000 13,000 8100 6356 9000

1750 2356 1800 2750 11,600 1900 2439 6210

43.8 31.0 20.0 55.0 89.2 23.5 38.4 69.0

salutaris (G.Bertol.) Chiov. (syn.Warburgia breyeri Pott.) for medicinal purposes. Remarkably, Warburgia salutaris is currently classified as ‘an endangered species’ (Hilton-Taylor et al., 1998). To date, the paucity of concrete and reliable statistical data on the levels of harvesting remains a major bottleneck in assessing the magnitude of the medicinal plant trade across the continent. The few quantitative medicinal market surveys that have been undertaken in South Africa (Dold and Cocks, 2002; Williams et al., 2000a; Williams et al., 2007f), Ghana (van Andel et al., 2012), Gabon (Towns et al., 2014), Benin (Quiroz et al., 2014), Sierra Leone (Jusu and Sanchez, 2013c, 2014c) and Tanzania (McMillen, 2012) have highlighted the high risk posed by overexploitation of medicinal plants. Accordingly, van Andel et al. (2015) have reiterated the scarcity of data on the effects of commercial harvesting of medicinal plants on their natural populations. Quantitative medicinal market surveys provide a snapshot of a country's medicinal flora including species diversity, commonly traded plant parts and extent of harvesting. Therefore, such surveys are a key instrument in assessing conservation priorities and identifying plant species at high risk of overharvesting and unsustainable utilization (Dold and Cocks, 2002). Furthermore, medicinal market-derived data such as individual plant sizes can be used to make inferences about the status of wild plant populations (Williams et al., 2007a; Williams et al., 2007e). However, despite their importance, medicinal plant markets in Africa remain under-characterized (Dzoyem et al., 2013; Quiroz et al., 2014). The unique floral diversity and richness on the African continent has attracted significant scientific exploration in the search for new therapeutic pharmaceuticals, especially in the past few decades. The international interest in African medicinal plants dates back to the time of arrival of European settlers on the continent. Examples of early collection, preservation (as herbarium specimens) and extensive ethnobotanical observations of medicinal plants include works of John Smyth in 1695 97, Henry Tedlie in 1792–1818 and Peter Thonning in 1799–1803 in Ghana (Soelberg et al., 2015). Elsewhere, Pelargonium sidoides DC., a medicinal plant endemic to South Africa and the Lesotho Highlands, was introduced into the European herbal market at the turn of the 20th century for the treatment of tuberculosis (Bladt and Wagner, 2007; Brendler and Van Wyk, 2008). Remarkably, Pelargonium sidoides has become one of the most widely researched African medicinal plant in European laboratories (Brendler and Van Wyk, 2008; Moyo and Van Staden, 2014). Research and astute marketing have led to the international commercial success of Pelargonium sidoides involving a network of harvesters, buyers, processors and international pharmaceutical manufacturers (Moyo and Van Staden, 2014). Recently, Currais et al. (2014) used the rich ethnpharmacological knowledge of local communities in São Tomé and Príncipe in the Guinean Forests of West Africa Hotspot to identify and screen neuroprotective compounds relevant to Alzheimer's disease from medicinal plants. Similarly, there is growing interest in Malagasy medicinal plants, one of the biggest islands in the world renowned for its high degree of endemic plant species

(Table 1). However, ethnobotanical knowledge of the Malagasy flora remains poorly investigated, hence only about 10% of its medicinal plant species have been screened for biological activities (Norscia and Borgognini-Tarli, 2006). Loss of ethnobotanical knowledge and increasing degradation of natural habitats on the island continues to reduce abundance of medicinal plants, thereby limiting the potential for new discoveries (Novy, 1997). Likewise, van Andel et al. (2015) highlighted the lack of data on commercial harvesting and extraction of medicinal plants as a high risk factor in the development of herbal pharmaceuticals.

4. Conservation: status, causes and challenges of medicinal plants in sub-Saharan Africa Conservation concerns on natural resources especially plant species remain a global challenge (Affolter and Pengelly, 2007; Hamilton, 2004). Sadly, the rate at which plant biodiversity is being lost is projected to increase (Ahrends et al., 2011). Based on available data (IUCN, 2014), the severity of this problem as indicated by the high number of plant species currently under strain (critically endangered, endangered or vulnerable) is well pronounced in African countries such as Cameroun (54%), Madagascar (51%), Tanzania (46%), Gabon (36%), Nigeria (36%), Congo DR (33%), Côte d'Ivoire (33%), and Kenya (29%). The general decrease in plant diversity are often due to multiple factors such as habitat destruction, competition from alien species and mortality from introduced diseases, pollution and overexploitation for diverse uses including food, shelter and medicinal purposes (Affolter and Pengelly, 2007; Canter et al., 2005). Medicinal application of plants is one of the principal uses of the natural resources with regards to the high number of species (Iwu, 2014; Schippmann et al., 2002). Overall, the value of medicinal plants is essentially infinite based on their significant contributions to healthcare, financial income, cultural identity and livelihood security (Hamilton, 2004). In African, an estimated 9% of the 60000 described plant taxa possess over 16300 therapeutic uses (Neuwinger, 2000). Table 2 provides an overview of the biological activities of the 51 top ranked medicinal plants found in Africa. As indicated by the number of peer-reviewed papers on three major scientific databases (Science Direct, Web of Science and Scopus), the 51 plants have been a major focus of research including safety evaluation and chemical characterization (Table 3). In addition, pre-clinical and clinical trials have also been conducted for some of the medicinal plants. The majority (47%) of these medicinal plants, for example, Agathosma betulina (South Africa), Boswellia sacra (Somalia), Cyclopia spp. (South Africa) and Warburgia salutaris (South Africa, Swaziland, Mozambique, Zimbabwe) have low/narrow distribution occurring only in 1–5 countries on the Continent (Fig. 1). Even though this narrow occurrence may enhance the economic value of such valuable medicinal plants, it inevitably aggravates the conservation strain on the limited populations especially in the presence of high demand from the local and international markets.


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Table 2 An overview of African most important 51 medicinal plants (Brendler et al., 2010). The species name and family are according to WCSP (2013). Family

Species

Common name

a

Life bDistribution form range in Africa

Examples of typical biological activities

Conservation status (reference)

Aizoaceae

Sceletium tortuosum (L.) N.E. Br.

H

L

Sedative Anti-depressant

Least concern (Victor and Powell, 2005)

Annonaceae

Xylopia aethiopica (Dunal) A.Rich.

W

M

Aphloia theiformis (Vahl) Benn.

W

L

Apiaceae

Centella asiatica (L.) Urb.

Centella, Pepperwort

H

L

Apocynaceae

Carissa spinarum L. (Syn: Carissa edulis (Forssk.) Vahl)

W Climbing numnum, Natal plum, Currant bush

A

Apocynaceae

Catharanthus roseus (L.) G.Don

Madagascar periwinkle

H

L

Apocynaceae

Cryptolepis sanguinolenta (Lindl.) Schltr.

Ghanaian quinine, Yellowdye root

W

M

Apocynaceae

Bitterghaap

H

L

Apocynaceae

Hoodia gordonii (Masson) Sweet ex Decne. Mondia whitei (Hook.f.) Skeels

African ginger, White's ginger

O

L

Apocynaceae

Rauvolfia vomitoria Afzel.

Poison devil's pepper

W

M

Apocynaceae

Strophanthus gratus (Wall. and Hook.) Baill.

O

M

Apocynaceae

Voacanga africana Stapf ex Scott-Elliot

Climbing oleander, Cream fruit, Rose allamanda, Smooth strophanthus Small fruit wild frangipani

Antimicrobial Bronchitis Female infertility Anti-diuretic Antimicrobial Anti-inflammatory Anthelmintic Antimicrobial Anti-inflammatory Anti-nociceptive Anti-ulcer Wound healing Sickle-cell anaemia Anti-cancer Anthelmintic Purgative Antimicrobial Hypertension Hodgkin's disease Anti-cancer Antimicrobial Anti-malaria Anti-inflammatory Antihyperglycaemic Appetite suppressant Anti-diabetic Aphrodisiac Purgative Anthelminthic Anxiety and depression Anti-hypertensive Nervous and mental disorder Parasitic skin diseases Cardiovascular disorders

Not accessed

Aphloiaceae

Sceletium herb, Kanna, Channa, Kougoed African grains of Selim, Ethiopian pepper, Senegal pepper Mountain peach

W

A

Apocynaceae

Xysmalobium undulatum (L.) W.T.Aiton

Milk bush, Bitter H root

L

Bignoniaceae

Kigelia africana (Lam.) Benth.

Sausage tree, Cucumber tree

W

A

Burseraceae

Boswellia sacra Flueck.

Frankincense, olibanum-tree

W

L

Burseraceae

Commiphora myrrha (Nees) Engl.

Somali-Myrrhe

W

L

Canellaceae

Warburgia salutaris (G.Bertol.) Chiov. (syn. Warburgia breyeri Pott.)

Muranga, Pepper W Bark Tree

L

Anti-convulsant Anti-duretic Antispasmodic Anti-diarrhoeal Molluscicidal Central nervous system degenerative diseases Anti-diarrhoeal Antispasmodic Wound healing Antimicrobial Anti-plasmodial Cytotoxic Antimicrobial Anti-inflammatory Cytotoxic Rheumatoid arthritis Antimicrobial Anti-inflammatory Anti-ulcer Antimicrobial Molluscicidal Anti-diuretic Cytotoxic

Not accessed

Least concern (Gupta, 2013)

Not accessed

Not accessed

Not accessed

Data deficient insufficient information (Raimondo et al., 2008) Endangered (Williams et al., 2008b)

Not accessed

Not accessed

Not accessed

Least concern (Kamundi and Victor, 2005) Least concern (Foden and Potter, 2005g) Lower risk/near threatened (Thulin, 1998)

Not accessed

Endangered (Hilton-Taylor et al., 1998)


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Table 2 (continued ) Family

Species

Common name

a

Life Distribution form range in Africa



Clusiaceae

Garcinia kola Heckel

Bitter kola

W

M

Vulnerable (Cheek, 2004)

Combretaceae

Combretum micranthum G.Don

Kinkeliba (benin) W

M

Combretaceae

Terminalia sericea Burch. ex DC.

Silver clusterleaf, Silver terminalia

W

M

Compositae

Artemisia afra Jacq. ex Willd.

Wormwood

H

L

Compositae

Gymnanthemum coloratum (Willd.) H. Rob. and B. Kahn (Syn:Vernonia colorata (Willd.) Drake)

Bitter leaf

W

A

Compositae

Vernonia amygdalina Delile (Syn: Gymnanthemum amygdalinum (Delile) Sch.Bip. ex Walp.)

Bitter leaf

W

A

Convolvulaceae

Ipomoea pes-caprae subsp. brasiliensis (L.) Beach morning H Ooststr. glory, Goat's foot

A

Euphorbiaceae

Euphorbia hirta L.

Asthma plant, Red euphorbia

H

A

Geraniaceae

Pelargonium sidoides DC.

Umckaloabo, South African Geranium

H

L

Hypericaceae

Harungana madagascariensis Lam. ex Poir.

Haronga

W

M

Hypoxidaceae

Leguminosae

H Hypoxis hemerocallidea Fisch., C.A.Mey. & African star Avé-Lall. grass, African potato Acacia senegal (L.) Willd. Gum tree, Three- W thorned acacia, White gumacacia Aspalathus linearis (Burm.f.) R.Dahlgren Rooibos tea W

Antimicrobial Antioxidant Anti-hepatotoxic Anti-inflammatory Antidiabetic Anti-viral Antimicrobial Anthelmintics Anti-malaria Diuretic Antioxidant Antimicrobial Anti-inflammatory Anti-carcinogenic Anti-diabetic Adaptogen (stress and anxiety) Antimicrobial Antioxidant Anti-malaria Cardiovascular Cytotoxic Anthelmintic Sedative Anthelmintic Antimicrobial Anti-malarial Anti-inflammatory Antimicrobial Anti-diabetic Anti-plasmodial Antioxidant Hepato-protective Antimicrobial Antihistaminic Anti-inflammatory Antispasmodic Antimicrobial Antispasmodic Antiprotozoal Anti-inflammatory Acute bronchitis Antimicrobial Anti-virus Immunomodulatory Antioxidant Antimicrobial Anti-plasmodial Anti-protozoan Anti-diarrhoeal Anti-inflammatory Anti-inflammatory Anti-mutagenic Cytotoxic Antimicrobial Anti-diabetic

L

Least concern (Foden and Potter, 2009)

Leguminosae

Cajanus cajan (L.) Millsp.

Pigeon pea

W

A

Leguminosae

Cyclopia spp.: Cyclopia genistoides (L.) Vent., Cyclopia intermedia E.Mey., Cyclopia subternata Vogel (syn Cyclopia falcata (Harv.) Kies), Cyclopia sessiliflora Eckl. and Zeyh.

Honeybush tea, mountain tea

W

L

Antioxidant Antispasmodic Anti-mutagenic Anti-malaria Sickle-cell anaemia Cytotoxic Antioxidant Anti-mutagenic

Leguminosae

Griffonia simplicifolia (DC.) Baill.

Griffonia

W

M

Leguminosae

b

L

A

Anti-inflammatory Depression, psychiatric and

Not accessed

Least concern (Foden and Potter, 2005i)

Least concern (Foden and Potter, 2005b)

Least concern (Foden and Potter, 2005e)

Least concern (Foden and Potter, 2005d)

Least concern (Foden and Potter, 2005f)

Not accessed

Least concern (De Castro et al., 2012)

Not accessed

Declining (Williams et al., 2008a)

Not accessed

Not accessed

Cyclopia genistoides¼Near threatened; Cyclopia intermedia, Cyclopia subternata ¼ Declining (Schutte-Vlok and Raimondo, 2011.); Cyclopia sessiliflora¼ Near threatened (Raimondo, 2014) Not accessed


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Species

Common name

Leguminosae

Sutherlandia frutescens (L.) R.Br. (Syn: Cancer bush, Lessertia frutescens (L.) Goldblatt and J.C. Balloon pea, Manning subsp. Frutescens) Sutherlandia

Malvaceae

a

b


W

L

Adansonia digitata L.

W Baobab tree, Lemonade tree, Tartaric acid tree, Monkey bread

A

Malvaceae

Hibiscus sabdariffa L.

W

A

Meliaceae

Trichilia emetica Vahl

Roselle, Florida cranberry, sour sour, Jamaica sorrel Natal mahogany

W

A

Moringaceae

Moringa oleifera Lam.

W

A

Pedaliaceae

Harpagophytum procumbens (Burch.) DC. Devil's claw ex Meisn. (unresolved)

H

L

Phyllanthaceae

Antidesma madagascariense Lam.

Rosaceae

Drumstick tree, Tree of life, Horseradish tree

W

L

Prunus africana (Hook.f.) Kalkman

Bois de gaulette blanc Red Stinkwood

W

A

Rubiaceae

Danais fragrans (Lam.) Pers.

Liane jaune

W

L

Rubiaceae

Sarcocephalus latifolius (Sm.) E.A.Bruce. (Syn: Nauclea latifolia Sm.)

W

M

Rutaceae

Agathosma betulina (P.J.Bergius) Pillans

African peach, Guinea peach, Sierra Leone peach, Country fig Buchu

W

L

Rutaceae

Toddalia asiatica (L.) Lam.

Orange climber

O

M

Strelitziaceae

Ravenala madagascariensis Sonn.

O

L

Xanthorrhoeaceae Aloe ferox Mill.

Traveller's tree, Traveller's palm Cape aloe

H

L

Xanthorrhoeaceae Bulbine frutescens (L.) Willd.

Snake flower

H

L

Zingiberaceae

Aframomum melegueta K.Schum.

Alligator pepper

H

A

Zingiberaceae

Siphonochilus aethiopicus (Schweinf.) B.L. Natal ginger, Burtt Wild ginger,

H

L


neurological disorders Antioxidant Anti-inflammatory Anti-diabetic Anti-HIV Anxiety Antioxidant Anti-inflammatory Anti-cancer Cardiovascular diseases Antioxidant Anti-hypertensive Degenerative diseases Antimicrobial Anti-inflammatory Anti-trypanosomal Anti-plasmodial Anthelmintic Hepatoprotective Anti-pyretic Antioxidant Antimicrobial Anti-inflammatory Anthelmintic Anti-hypertensive Antispasmodic Arthritis Anti-cancer Degenerative diseases Wound healing Anti-inflammatory Analgesic Antioxidant Anti-malaria Antimicrobial Antidiabetic Antimicrobial Anti-malarial Anti-inflammatory Kidney disease Anti-malaria Wound-healing Skin diseases Antimicrobial Anti-malarial Anthelmintic/ antitry-panosoma Anti-diuretic Anti-inflammatory Antispasmodic Diuretic Antimicrobial Anti-malarial Cytotoxic Cardiovascular diseases Anti-inflammatory Antimicrobial Anti-septic Laxative Skin diseases Wound healing Antimicrobial Antioxidant Anti-inflammatory Neuro-protective Aphrodisiac Antimicrobial Anti-inflammatory


Least concern (Foden and Potter, 2005h)

Least concern (Foden and Potter, 2005a)

Not accessed

Least concern (Williams et al., 2008c)

Not accessed

Least concern (Raimondo et al., 2012a)

Not accessed Vulnerable (World Conservation Monitoring Centre, 1998)

Not accessed

Not accessed

Declining (Trinder-Smith and Raimondo, 2008) Least concern (Foden and Potter, 2005j)

Not accessed Least concern (Raimondo et al., 2012b) Least concern (Foden and Potter, 2005c) Not accessed

Critically endangered (Lötter et al., 2006)


67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66

7


Zygophyllaceae

a b

Species

Common name

Balanites aegyptiaca (L.) Delile

African ginger root Soapberry tree

a

b




Uterine relaxing W

A

Antimicrobial Antioxidant Anti-malaria Antidiabetic Anthelmintic Molluscicidal

Not accessed

Life form: W ¼small shrubs and trees, H¼ herbaceous plants, O ¼ vines (lianas and non-woody vines), cushion plants and rosettes, canes and palm-like plants. Distribution range in Africa: L¼ 1–5 countries, M ¼ 6–20 countries, A ¼ more than 20 countries

In recent times, the African medicinal plant industry has come under more scrutiny as a result of the growing concern over the sustainability of wild plants, which is usually the main source of traditional medicines (Dzoyem et al., 2013). Using the top 51 important plant species in Africa as a case study, Table 2 highlights the current conservation status of these medicinal plants. Approximately 20% of the widely used medicinal plants are currently under several threats (Critically Endangered, Endangered, Vulnerable or Declining) while the conservation status of 43% of these species has not been evaluated (Fig. 2). Given their importance in African Tradition Medicine, the absence of such crucial data is worrisome and urgent action is necessary to assess their conservation statuses. Although 35% of the plant species are classified as ‘least concern’, it is important to emphasize that the majority of the data were solely based on an South Africa survey, a country known for a greater conservation drive than other African countries. Thus, the ‘least concern’ status recorded for some of these plant species may differ in other African countries. Generally, information regarding species that are sold, their prices, and the marketed volumes are the first steps in identifying species with conservation or resource management priorities (Affolter and Pengelly, 2007; van Andel et al., 2012). However, the shortage or absence of scientific data on these important aspects of medicinal trade in Africa is common and remains a major challenge (Dzoyem et al., 2013). With the increasing recognition of the importance and value of such data, recent quantitative surveys evaluating the volumes of medicinal plants traded have been documented for few African countries such as South Africa (Williams et al., 2000b; Williams et al., 2007 g), Ghana (van Andel et al., 2012), Gabon (Towns et al., 2014), Tanzania (McMillen, 2008) and Sierra Leone (Jusu and Sanchez, 2013a). Data generated from these studies will certainly contribute toward the evaluation of the conservation status of the commonly used medicinal species. Findings from these aforementioned studies indicate that natural populations of medicinal plants are selectively targeted and their collection poses special problems for conservationists. Their sustainability is strongly influenced by the vegetation type of collection, relative abundance and growth rates (Lubbe and Verpoorte, 2011). Schippmann et al. (2002) also highlighted that the susceptibility of medicinal plant species to overharvesting remain a function of life forms and plant part used. Woody plants (shrubs and trees) constitute the bulk (65%) of the 51 most important African medicinal plants (Fig. 3). Although collection of leaves from such woody plants pose less strain on their survival, the de-barking or collection of the roots which remain a common practice in African Traditional Medicine cause enormous strain and increase mortality in species such as Prunus africana and Wurburgia salutaris. In South Africa, an estimated 85% of the medicinal plants harvested, and widely used, constitute the non-renewable parts such as bulbs, rhizomes and bark (Mander, 1998). Similar

high utilization of non-sustainable harvesting of such organs have also been reported in countries such as Sierra Leone (Jusu and Sanchez, 2013a), Gabon (Towns et al., 2014), South Africa (Dold and Cocks, 2002; Keirungi and Fabricius, 2005) and Ghana (van Andel et al., 2012). With any medicinal plant, the removal of wood, bark, bulbs/corms, roots, or whole plants generally leads to the death of an individual species (Cunningham, 1993; Gupta, 2013; Jusu and Sanchez, 2014a). In contrast, the harvest of leaves, fruits, or seeds is often considered less destructive or detrimental to plant survival. However, intensive pruning may eventually affect reproductive performance of such species. From an ecological perspective, these problems can be summarized in the following categories: (1) rates of growth, survival and reproduction; (2) population structure and dynamics, (3) community structure and composition, plant-animal and plant-plant interactions and (4) nutrient and organic matter dynamics, energy exchange (Ticktin, 2004). Thus, researchers must take into consideration the above dynamics (which correspond to different ecological levels) while designing and evaluating approaches with potential to mitigate the negative effects of medicinal plant overharvesting.

5. Cultivation of medicinal plants in sub-Saharan Africa: myth or solution? The medicinal plants sector is vastly diverse encompassing the collectors/gatherers, local vendors and consumers as well as heavily dependent industries such as nutraceutical and pharmaceutical companies that require large volume of raw material (Dzoyem et al., 2013). Thus, this diversity in interested parties has influenced the currently available conservation methods and will inevitably determine the success of any future approaches/solutions. In order to curb the incessant pressure on the wild populations of medicinal plants, meticulous measures that will guarantee the continuous supply of these valuable natural resources is pertinent (Affolter and Pengelly, 2007; Gandhi et al., 2014; Sharma and Pandey, 2013; van Andel et al., 2015; WHO, 2003). Adequate protection of some species can be achieved through increased regulation and the introduction of sustainable wild harvesting methods however, a more viable longterm option may involve an increase in domestic cultivation of medicinal plants (Canter et al., 2005; Geldenhuys, 2007; Moshi and Mhame, 2013; Schippmann et al., 2002). 5.1. Challenges encountered with cultivation of medicinal plants Cultivation of food crops is wholly accepted as the means of ensuring food security for the increasing population globally. In contrast, the issues of cultivation of medicinal plants have evoked diverse responses (Cordell, 2014; Sarasan et al., 2011). The substantial investment required for cultivation remain a major


67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132


8

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66

Table 3 Summary of research endeavors of African most important 51 medicinal plants (Brendler et al., 2010). The data were sourced from three databases (Science direct ¼ SD, Web of Science ¼ WOS and Scopus ¼SC) using the name of plants as search words, without any time limit (up till 11th April, 2015). The information may not be fully comprehensive but are only meant to provide an indication of research endeavors for comparative purposes. Family

Species

Number of peerreviewed publications SD

WOS SC

Evidence of safety test

Any pre-clinical Examples of common type or or clinical trials? class of phytochemicals

Aizoaceae Annonaceae Aphloiaceae

Sceletium tortuosum Xylopia aethiopica Aphloia theiformis

59 280 42

40 162 16

73 833 45

Yes Yes Yes

Yes No No

Apiaceae Apocynaceae

Centella asiatica Carissa spinarum (Syn: Carissa edulis

1468 82 (197) 4260

1142 42 (44) 5896

3939 Yes 100 Yes (245) 10802 Yes

Yes No

284 109 41 36 31 64 22 94 44 83 74 (2)

597 230 95 121 2564 182 45 377 188 237 214 (0)

Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes

Yes Yes No Yes No No Yes No Yes Yes No

303 61 133 115 0 (32) 386 (2)

1306 197 288 610 2 (157) 1397 (52)

Yes Yes Yes Yes Yes

No No No Yes No

Yes

Yes

1 383

5 1298

Yes Yes

No Yes

Catharanthus roseus

Alkaloids, phenolics, flavonoids, anthocyanins Alkaloids Sterol glycosides Phenolic acids, coumarins Alkaloids, flavonoids Alkaloids, cardiac glycosides Alkaloids Cardiac glycosides Phenolic acids,sterols Essential oil, terpenoids Essential oil, terpenoids Drimane sesquiterpenoids

Convolvulaceae Euphorbiaceae

220 129 61 110 136 141 63 234 106 234 92 (Syn 1) Garcinia kola Heckel 380 Combretum micranthum 176 Terminalia sericea 359 Artemisia afra 296 Gymnanthemum coloratum (Syn:Vernonia colorata) 1 (Syn 116) Vernonia amygdalina (Syn: Gymnanthemum amygdalinum) 476 (Syn 9) Ipomoea pes-caprae subsp. brasiliensis 8 Euphorbia hirta 898

Geraniaceae

Pelargonium sidoides

275

194

661

Yes

Yes

Hypericaceae Hypoxidaceae Leguminosae

Harungana madagascariensis Hypoxis hemerocallidea Acacia senegal Aspalathus linearis Cajanus cajan. Cyclopia spp.: Cyclopia genistoides, Cyclopia intermedia, Cyclopia subternata (syn Cyclopia falcata, Cyclopia sessiliflora Griffonia simplicifolia Sutherlandia frutescens (Syn: Lessertia frutescens subsp. Frutescens)

155 132 1964 489 2475 2060

74 114 721 323 5010 769

289 238 3236 1065 7926 3911

Yes Yes Yes Yes Yes Yes

Yes Yes Yes Yes Yes No

Essential oil, sterols, alkaloids Terpenoids, phenolic acids, flavonoids Coumarins, phenolic acids, flavonids Essential oil Phenolics, sterols Gum Arabic, rutin flavonoids Phenolic acid Phenolic acids, flavonoids

1326 2917 123 308 (18) (66)

Yes Yes

Yes Yes

Phenolics Terpenoids

364

803

Yes

Yes

Betulinic acid, tartaric acid, flavonols, sterols, terpenoids, alkaloids Flavonol glycoside Phenolic acids Phenolic acids, flavonoids Iridoids, flavonoids, sterols Terpenoids, phenolics Sterols, fatty acids Alkaloids, saponins, phenols, sterols, terpenoids Alkaloids, terpenoids

Bignoniaceae Burseraceae Canellaceae

Clusiaceae Combretaceae Compositae

Cryptolepis sanguinolenta Hoodia gordonii Mondia whitei Rauvolfia vomitoria Strophanthus gratus Voacanga africana Xysmalobium undulatum Kigelia africana Boswellia sacra Commiphora myrrha Warburgia salutaris (syn. Warburgia breyeri.)

No

Alkaloids Alkaloid, terpenoids Terpenoids, saponins, tannins, flavones, flavonoids Alkaloids, terpenoids Alkaloids, terpenoids

Malvaceae

Adansonia digitata

2023 166 (Syn 41) 453

Meliaceae Moringaceae Pedaliaceae Phyllanthaceae Rosaceae Rubiaceae

Hibiscus sabdariffa Trichilia emetica Moringa oleifera Harpagophytum procumbens Antidesma madagascariense Prunus africana Danais fragrans

1013 170 1836 465 15 509 5

859 71 1366 352 12 158 4

3119 196 5493 1086 23 811 5

Yes Yes Yes Yes Yes Yes Yes

Yes No Yes Yes No Yes No

Sarcocephalus latifolius (Syn: Nauclea latifolia)

29 84 (114) (443)

Yes

Yes

Agathosma betulina Toddalia asiatica Strelitziaceae Ravenala madagascariensis Xanthorrhoeaceae Aloe ferox Bulbine frutescens

44 (Syn 226) 97 241 53 305 55

42 112 44 169 37

97 548 95 440 89

Yes Yes Yes Yes Yes

Yes No No Yes Yes

Zingiberaceae

132

108

341

Yes

Yes

Rutaceae

Aframomum melegueta

Alkaloids, phenolics Alkaloids, flavones, tannins Terpenoids, sterols Essential oil, terpenoids Saponins, sesquiterpene lactones Flavonoids, terpenoids, cardiotonic glycosides

Essential oils, flavonoids Alkaloids, coumarins, terpenoids Sterols, flavonoid, terpenoids Hydroxyanthracene derivatives Knipholone-type phenylanthraquinones Gingerol, shogaol, terpenoids


67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66

9


Species

Zygophyllaceae

Number of peerreviewed publications

Siphonochilus aethiopicus Balanites aegyptiaca

SD

WOS SC

59 549

34 299

Abundant 31%

Low 47%

Moderate 22%

Fig. 1. Frequency of the distribution of 51 most important African medicinal plants across the continent. Low/narrow¼ 1–5 countries, Moderate¼ 6–20 countries, Abundant ¼more than 20 countries.

DDT 2% D/NT/V/EN 18%

58 1018

Evidence of safety test

Any pre-clinical Examples of common type or or clinical trials? class of phytochemicals

Yes Yes

No No

Terpenoids Saponin, flavonoids

benefit of efficient cultivation protocols for highly utilized medicinal plants cannot be over-emphasized. Another major challenge is that based on cultural and spiritual reasons, as African traditional healers are of the opinion that cultivated medicinal species are qualitatively inferior than the wild plants (Schippmann et al., 2002). In attempts to debunk these concerns, researchers have intensified efforts aimed at documenting the possible variations between wild and cultivated medicinal plants (Costa et al., 2013; Malik et al., 2010; Masondo et al., 2013; Moyo et al., 2013; Ncube et al., 2011; Shaik et al., 2011b; White et al., 2008). For the pharmaceutical and other medicinal plant-dependent industries, cultivated plant material is often preferred as it is easier to control the whole supply chain and minimize chemical variation (Lubbe and Verpoorte, 2011). Furthermore, other quality control problems such as adulteration or misidentification of plant material is mostly under check thereby adhering to quality standards and reduced batch-to-batch variations because the plants are grown under fairly controlled conditions (Canter et al., 2005; Sarasan et al., 2011; Schippmann et al., 2002). 5.2. Current cultivation status of medicinal plants in sub-Saharan Africa

not accessed 45% least concern 35%

Fig. 2. Frequency of the conservation status of 51 most important African medicinal plants. D¼declining, DDT¼ data deficient, E ¼endangered, V ¼ vulnerable, NT¼ near threaten.

Others 6%

Herbs 29%

Woody 65%

Cultivation of medicinal plants generally requires intensive care and management. The conditions and duration of cultivation required vary depending on the quality of medicinal plant materials required (WHO, 2003). In sub-Saharan Africa, cultivation of medicinal plants is still at its infancy when compared to Europe and Asia. In recent time, strong initiatives toward commercial cultivation of medicinal plants has been reported in Northern (Egypt, Libya, Morocco, Tunisia), eastern (Uganda, Kenya, and Tanzania), western (Nigeria, Ghana and Sierra Leone) and southern (South Africa and Madagascar) part of the Continent (Moshi and Mhame, 2013). As highlighted in the literature, cultivation efforts for some of the important 51 African medicinal plants such as Acacia senegal (Vengadesan et al., 2002), Adansonia digitata (Sanchez, 2011), Mondia whitei (Aremu et al., 2011), Prunus africana (Stewart, 2003), Pelargonium sidoides (Moyo and Van Staden, 2014) and Harpagophytum spp. (Stewart and Cole, 2005) are considered as a priority among researchers and policymakers. In addition, increasing evidence across the Continent in countries such as South Africa (Keirungi and Fabricius, 2005) and Sierra Leone (Jusu and Sanchez, 2014a) strongly suggest the potential of cultivating other equally valuable medicinal plants on a small and large scale provided the right approach is applied. Notwithstanding the sporadic reports on cultivation of some medicinal plants, there is a clear lack of documented information on the magnitude of such activities. Therefore, more studies are required in this area of research.

Fig. 3. Frequency of plant form based on general appearance of 51 most important African medicinal plants.

5.3. Potential approaches to enhance cultivation of medicinal plants in sub-Saharan Africa

deterrent to investors as cultivated raw materials are usually more expensive than wild harvested plants (Lubbe and Verpoorte, 2011). While the assertion may hold in the short-term, the long-term

Despite the benefits associated with conventional propagation, some plant species are not easy to cultivate, require long regeneration times and have poor germination rates thereby rendering


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10

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66


these approaches ineffective and unattractive. Thus, the use of innovative biotechnology approaches or techniques which help eliminate these aforementioned problems as well as allowing for ease of standardization of the chemical constituents of highly sought after medicinal plants remain relevant (Gandhi et al., 2014; Moyo et al., 2011; Sarasan et al., 2011). The potential of some of these biotechnological approaches/techniques is subsequently highlighted. Plant tissue culture (otherwise known as in vitro propagation or micropropagation) is a vital tool that has afforded the mass propagation, improvement and conservation of medicinal species globally (Rout et al., 2000). Micropropagation has the potential to produce sufficient planting stock for restoring threatened populations as well as for commercial cultivation. Currently, effective micropropagation protocols have been developed for highlyutilized African medicinal plants such as Catharanthus roseus (Moreno et al., 1995), Cyclopia genistoides (Kokotkiewicz et al., 2012), Sutherlandia frutescens (Shaik et al., 2011b), Mondia whitei (Baskaran et al., 2014), Warburgia salutaris (Kowalski and Van Staden, 2001), Centella asiatica (Nath Tiwari et al., 2000; Paramageetham et al., 2004), and Hypoxis hemerocallidea (Moyo et al., 2014). These regenerated plant materials which are often genetically uniform and of superior quality can be made available to small-scale farmers in large numbers, in order to relieve pressure on wild populations, thereby ensuring their conservation (Sarasan et al., 2011). As a control measure and to guarantee wider acceptance in the medicinal plant industry, it is essential that plant materials grown in fields (either conventional or micropropagated materials) are not only analysed in terms of growth and production, but also chemically evaluated and screened for pharmacological efficacy (Geldenhuys, 2007; Jäger and Van Staden, 2000). Various biotechnological techniques have contributed to a better understanding of metabolic pathways involved in the biosynthesis of valuable chemicals (Baque et al., 2012; Ramachandra Rao and Ravishankar, 2002; Sato and Yamada, 2008; Verpoorte et al., 2002). Diverse strategies including the optimization of growth media and culture environments can easily enhance biomass accumulation and phytochemicals in the cells and organs of medicinal plant species (Matkowski, 2008; Murthy et al., 2014). In addition, the use of different phytohormones predominantly cytokinins and auxins have been demonstrated to be a vital elicitor of valuable phytochemicals in a number of well-known African medicinal plants (Amoo et al., 2014a; Aremu et al., 2013; Grobbelaar et al., 2014; Moyo et al., 2014; Shaik et al., 2011a). Plant biotechnological approaches that have proved useful for food and ornamental plants can play a major role in the cultivation of medicinal plants. Considering the unprecedented high rate of loss of floral diversity in Africa, the cultivation of commonly used medicinal plant species is an indispensable approach for their long term sustenance and conservation.

6. Conclusions Concerns that the loss of medicinal plant species is occurring at unprecedented levels are real. Unfortunately, in contrast to terrestrial fauna, the dilemma with plant species is that despite the staggering state-of-conservation statistics, the impacts remain largely invisible to society. Invariably, this has a major influence on society's attitudes and their level of support for plant conservation efforts. Equally disturbing is the paucity of detailed conservation status data for medicinal plant species in most African countries. In this regard, the comprehensive South African conservation assessment model based on the IUCN Red List categories can provide valuable lessons for other Africa countries. Most scientific studies on medicinal plants in Africa have been skewed towards their pharmacological and phytochemical evaluations, whilst

aspects related to their conservation remain largely neglected. For a better understanding of the magnitude of utilization and conservation status of medicinal plant resources, more research is required. Based on the few scattered studies across the African continent, there is categorical evidence indicating the rapid decline of plant species due to numerous factors including overexploitation for medicinal trade. Unless bold and pragmatic action is taken now, our rich medicinal plant heritage in Africa will disappear into obscurity. In this regard, repeated calls for the cultivation of important medicinal plants require serious consideration.

Acknowledgements We are grateful to the University of KwaZulu-Natal (Pietermaritzburg) and the National Research Foundation (Pretoria), South Africa for financial support. References Affolter, J.M., Pengelly, A., 2007. Conserving medicinal plant biodiversity. In: Wynn, S.G., Fougère, B.J. (Eds.), Veterinary Herbal Medicine. Mosby, Saint Louis, Missouri, USA, pp. 257–263. Ahrends, A., Rahbek, C., Bulling, M.T., Burgess, N.D., Platts, P.J., Lovett, J.C., Kindemba, V.W., Owen, N., Sallu, A.N., Marshall, A.R., Mhoro, B.E., Fanning, E., Marchant, R., 2011. Conservation and the botanist effect. Biol. Conserv. 144, 131–140. Amoo, S.O., Aremu, A.O., Moyo, M., Szüčová, L., Doležal, K., Van Staden, J., 2014a. Physiological effects of a novel aromatic cytokinin analogue in micropropagated Aloe arborescens and Harpagophytum procumbens. Plant Cell, Tissue Organ Cult. 116, 17–26. Amoo, S.O., Aremu, A.O., Van Staden, J., 2014b. Unraveling the medicinal potential of South African Aloe species. J. Ethnopharmacol. 153, 19–41. Aremu, A.O., Cheesman, L., Finnie, J.F., Van Staden, J., 2011. Mondia whitei (Apocynaceae): a review of its biological activities, conservation strategies and economic potential. S. Afr. J. Bot. 77, 960–971. Aremu, A.O., Gruz, J., Šubrtová, M., Szüčová, L., Doležal, K., Bairu, M.W., Finnie, J.F., Van Staden, J., 2013. Antioxidant and phenolic acid profiles of tissue cultured and acclimatized Merwilla plumbea plantlets in relation to the applied cytokinins. J. Plant Physiol. 170, 1303–1308. Baque, M.A., Moh, S.-H., Lee, E.-J., Zhong, J.-J., Paek, K.-Y., 2012. Production of biomass and useful compounds from adventitious roots of high-value added medicinal plants using bioreactor. Biotechnol. Adv. 30, 1255–1267. Baskaran, P., Kumari, A., Van Staden, J., 2014. Embryogenesis and synthetic seed production in Mondia whitei. Plant Cell, Tissue Organ Cult., 10.1007/s1124011014-10695-x. Bladt, S., Wagner, H., 2007. From the Zulu medicine to the European phytomedicine Umckaloabos. Phytomedicine 14 (Suppl. 1), S2–S4. Brendler, T., Eloff, J.N., Gurib-Fakim, A., Phillips, L.D., 2010. African Herbal Pharmacopoeia. Association for African Medicinal Plants Standards (AAMPS), Port Louis, Republic of Mauritius. Brendler, T., Van Wyk, B.E., 2008. A historical, scientific and commercial perspective on the medicinal use of Pelargonium sidoides (Geraniaceae). J. Ethnopharmacol. 119, 420–433. Canter, P.H., Thomas, H., Ernst, E., 2005. Bringing medicinal plants into cultivation: Opportunities and challenges for biotechnology. Trends Biotechnol. 23, 180–185. CEPF, 2001. Ecosystem Profile: The Cape Floristic Region, South Africa. 〈http://www. cepf.net/resources/hotspots/africa/Pages/default.aspx〉 (accessed 30.01.15). CEPF, 2003. Ecosystem Profile: The Succulent Karoo Hotspot, Namibia and South Africa. 〈http://www.cepf.net/resources/hotspots/africa/Pages/default.aspx〉 (accessed 30.01.15) . CEPF, 2010. Ecosystem profile: Maputaland Pondoland Albany Biodiversity hotspot. 〈http://www.cepf.net/resources/hotspots/africa/Pages/default.aspx〉 (accessed 30.01.15). CEPF, 2012. Ecosystem profile: Eastern Afromantane biodiversity hotspot. 〈http://www. cepf.net/resources/hotspots/africa/Pages/default.aspx〉 (accessed 30.01.15). CEPF, 2015. The biodiversity Hotspots. Critical Ecosystem Partnership Fund. 〈http://www. cepf.net/resources/hotspots/Pages/default.aspxCritical〉 (accessed 30.01.15). Cheek, M., 2004. Garcinia kola. The IUCN Red List of Threatened Species. Version 2014.3. 〈http://www.iucnredlist.org/details/34715/0〉 (accessed 08.01.15). Cordell, G.A., 2014. Phytochemistry and traditional medicine the revolution continues. Phytochem. Lett. 10 xxviii-xl. Costa, P., Gonçalves, S., Valentão, P., Andrade, P.B., Romano, A., 2013. Accumulation of phenolic compounds in in vitro cultures and wild plants of Lavandula viridis L'Hér and their antioxidant and anti-cholinesterase potential. Food Chem. Toxicol. 57, 69–74. Cunningham, A.B., 1993. African Medicinal Plants: Setting Priorities at the Interface Between Conservation and Primary Healthcare, People and Plants Working Paper. United Nations Educational, Scientific and Cultural Organisation (UNESCO), Paris, France.


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Phylogenetic exploration of commonly used medicinal plants in South Africa.

Glycans in Medicinal Chemistry: An Underexploited Resource.

AN ETHNOBOTANICAL STUDY OF MEDICINAL PLANTS USED IN VILLAGES UNDER JONGILANGA TRIBAL COUNCIL, MPUMALANGA, SOUTH AFRICA.

Traditional medicines in Africa: an appraisal of ten potent african medicinal plants.

Medicinal plants of the Kamiesberg, Namaqualand, South Africa.

An ethnobotanical survey of medicinal plants in Trinidad.

Cytotoxicity of selected medicinal plants used in Mt. Frere District, South Africa.

Indian Medicinal Plants.

Indian Medicinal Plants.

A bioactivity versus ethnobotanical survey of medicinal plants from Nigeria, west Africa.

Medicinal Plants from the Ouaddaï Province (Chad): An Ethnobotanical Survey of Plants Used in Traditional Medicine.

An ethno-medicinal study of medicinal plants used for the treatment of diabetes.

Neuroprotective effects of medicinal plants.

Antifertility activity of medicinal plants.

Indian Medicinal Plants: Part III.

Phytodentistry: use of medicinal plants.

Indian Medicinal Plants (Part II).

Medicinal plants: another man's poison.

Medicinal Plants in Therapy: Antioxidant Activities.

Medicinal Plants: Their Use in Anticancer Treatment.

Progressive Dwindling in Multiple Sclerosis: An Opportunity to Improve Care.

Bioprospecting medicinal plants for antioxidant components.

Anemone medicinal plants: ethnopharmacology, phytochemistry and biology.

Effect of medicinal plants on wound healing.