Cultivation of Medicinal Plants in South Africa: a Solution to Quality Assurance and Consistent Availability of Medicinal Plant Materials for Commercialization

Research Paper

Cultivation of medicinal plants in South Africa: A solution to quality assurance and consistent availability of medicinal plant materials for commercialization

Tanga M1, Lewu FB2*, Oyedeji OA3, Accepted 23rd July, 2018 4 Oyedeji OO

1Department of Environmental and ABSTRACT Occupational studies, Faculty of Applied Science, Cape Peninsula University of Medicinal plants are plants which have been identified to have healing properties Technology, P O Box 652, Cape Town and their cultivation recently is gaining popularity due to the increasing 8000, South Africa 2Department of Agriculture, Faculty of preference towards plant-based products as a source of primary health care in Applied Science, Cape Peninsula both developing and developed countries. Cultivation of medicinal plant is a University of Technology, Wellington mitigative measure towards biodiversity conservation and also a viable alternative Campus P O Box X8, Wellington 7654, to overcome problems that are inherent to medicinal plant materials for quality South Africa 3Department of Chemical and Physical assurance and availability for commercialization. However, this is accompanied Sciences, Faculty of Natural Science, with some challenges of plant adaptation to new environment, disease Walter Sisulu University of Science and susceptibility, labour cost and net return. The use of good propagation techniques Technology, P/Bag X1 Mthatha 5099, is imperative to overcome the challenges associated with the production of South Africa 4Department of Chemistry, Faculty of secondary metabolites of interest to our herbal and pharmaceutical industries and Science and Agriculture, University of the implementation of good regulatory policy for safety and quality of medicinal Fort Hare, Alice, South Africa. plants products of standard is critical.

*Corresponding author. E-mail: [email protected]. Tel: 0218645213; Key words: Medicinal plants, cultivation, quality, secondary metabolites, 27725515617. commercialization.

INTRODUCTION

Plants have been of great importance as a source of than 85% of herbal medicines used in traditional health medicine since the time of human civilization and since care systems are derived from different parts of medicinal then their products are being used for different purposes plants (Phondani et al., 2014). such as food, shelter, clothing, health care and as In this regard, there has been an increasing interest agrochemicals (Kamble et al., 2010). worldwide in traditional system of medicine including Plant materials used for medicine include the active South Africa, with substantial increase in the use of herbal- ingredients of roots, stems, leaves, seeds and barks of trees derived medicines, supplements and cosmetics in in various combinations (Ngarivheme et al., 20015). communities (Fisk et al., 2014). Medicinal plants are plants that have healing properties In the recent decades, there has been an indiscriminate and contain mixtures of phytochemicals (Secondary harvesting, over-grazing and uncontrolled metabolites) that may act individually, additively or commercialization of medicinal plant species from the wild synergistically used to treat some illnesses (Mohammed (Barata et al., 2011). Indiscriminate harvesting of medicinal and Mundanthra, 2013). plants has led to an increasing trend in habitat loss locally Presently, medicinal plants are gaining popularity and globally due to environmental degradation and globally as a source of raw material for pharmaceuticals encroachment of alien invasive species which are adversely and traditional health care systems (Kandari et al., 2012). affecting the availability of medicinal plant in the wild According to the World Health Organization (WHO), about (Phondani et al., 2016). 80% of the world population relies (solely or partially) on In South Africa, millions of people in both rural and urban traditional medicine for their primary health care and more communities mostly rely on traditional medicine for their Academia Journal of Medicinal Plants; Tanga et al. 169

primary health care needs due to their easy accessibility importation (US$462.8 million) and exportation and affordability of plant materials with good knowledge (US$1034.8 million) of medicinal plants into Europe and know-how amongst the local communities between the period 1991 to 2002. In the last three decades, (Mahomoodally, 2013; Oliver, 2013). This is increasingly there has been a substantial growth in herb and herbal putting pressure on wild population with little or no product markets across the world. According to the mitigative measures like medicinal plant cultivation that Secretariat of the Convention on Biological Diversity, the may enhance quality, quantity, biomass production and global sales of herbal products were estimated to be quality control measures such as monitoring of metabolites US$60,000 million in 2002 (Food and Agricultural production and optimization of production techniques. Organization, 2007). Every year, about five hundred thousand tons of dried medicinal plants are traded internationally, with Importance of medicinal plants substantial quantities in South Africa’s national and local markets. More than 50% of the plants are harvested from Plants are the primary source of all medicines in the world the wild, and the demand for these materials keeps and provide mankind with new remedies (Beyene et al., increasing (Traffic International, 2015). The utmost form of 2016). traditional medicine has always remained the use of herbs Medicinal plants are the “backbone” of traditional which are highly lucrative in the international market. The medicine and are considered to have some important annual revenue of Western Europe between 2003 and 2004 ingredients which can be used in drug development and was US$ 5 billion (Chaudhary et al., 2010). synthesis. They play a critical role in the development of The trade in pharmaceutical plants is dominated by only human cultures around the world and also have a a few countries with three international trade centers; promising future because there are millions of plants Germany, USA, and Hong Kong. Twelve countries make up around the world with yet to be discovered medicinal 80% of both the exports and imports from the world activities (Singh, 2015). market. The major markets are in the developed countries, Traditional systems of medicine have become a topic of while the bulk of pharmaceutical plants are exported from global importance during the past decade. Presently, in developing countries, not or only little processed from many developing countries, a large proportion of the developing countries and they are of wild origin (Barata et population rely heavily on traditional practitioners, who al., 2011). The trade also contributes as a source of revenue uses exclusively medicinal plant materials for treatment of to millions of families involved in medicinal plants various illnesses on the account that medicinal plants are collection, with women often playing the major role of curative with no side effects (Rasool, 2012). supplying medicinal plant materials to pharmaceutical Although there may be the availability of orthodox industries. Although accurate data is lacking, available medicine in these countries, herbal medicines have always information indicates that trade is increasingly growing upheld fame popularity for historical and cultural reasons especially in Europe where 90% of commercially used (Hosseinzadeh et al., 2015; Vishwakarma et al., 2013). medicinal plant materials are collected from the wild Medicinal plants have many different characteristics. (Traffic International, 2015). When used in the treatment of diseases, it can be synergic, In South Africa, medicinal plant trade is a large and supportive and preventive (Rasool, 2012). At the moment, growing industry. It operates in both the formal and there is an increasing interest in the field of research on the informal sectors of the economy which involves a few metabolomics profile of medicinal plant species due to the stakeholders in the Eastern Cape but a greater number of remarkable diversity of both chemical and biological commercial harvesters from Kwa-Zulu Natal, Gauteng and activities of naturally occurring secondary metabolites Western Cape provinces (Williams, 2004). present in different plant species. This has led to the development of novel and sensitive techniques to detect some of these biologically active ingredients with improved Over-harvesting of medicinal plants isolation techniques to meet human’s medicinal needs (Hosseinzadeh et al., 2015). Medicinal plants are being harvested in increasing volume from the wild population all over the world creating pressure on plant diversity and population in the wild. In Trade in medicinal plants the recent decades, the demand for medicinal plants has increased from 8 to 15% per year in Europe, North Generally, every year more than 500,000 tons of plant America, and Asia (Ross, 2005; Bentley, 2010). materials of about 60,000 plant species are traded based on Furthermore, over 25% of prescribed medicines in their medicinal, nutritional and aromatics properties developed countries are derived from wild plant species (WHO. 2015). According to Barata et al. (2011), there has and up to 80% of people in developing countries are totally been a significant increase in the dependent on herbal medicine for their primary Academia Journal of Medicinal Plants; Tanga et al. 170

healthcare (Hamilton, 2004). was made to monitor plant species listed as threatened and In South Africa, about 72% of black South Africans rely protected species of the National Environmental exclusively on traditional health care system for their Management Biodiversity Act (NEMBA) Act N0: 10 of 2004 survival, which involves the use of medicinal plants between 2005 to 2020 by provincial and National (Mander et al., 2007). The increasing demand for herbal Authorities. In 2010, the Department of Environmental drugs and natural health products by the growing affair launched a R20 million conservation project on population, without putting in place a mitigating measure medicinal plants species in Limpopo to promote and like medicinal plants cultivation may result in some of these protect endermic medicinal plants species in South Africa plants going into extinction (Chen et al., 2016). through the Indigenous Knowledge System (IKS) of the According to the International Union for Conservation of South Africa Trust. Notwithstanding, the project did Nature (IUCN), there are between 50,000 to 80,000 encountered financial mismanagement for its collapse. flowering plant species used for medicinal purposes Moreover, despite the tremendous efforts put in place as worldwide. Among these, about 15,000 plant species are conservation strategies, the issues of shifting from under threats of extinction from overharvesting from the subsistence to commercial harvesting of medicinal plants wild and habitat destruction (Bentley, 2010) and 20% of materials as an employment opportunity is posing these wild resources have already been nearly exhausted unprecedented extinction threat to the wild population as with the increasing human population and plant setback to the aforementioned. consumption (Ross, 2005). Even though these pressures have been known for years, the accelerated loss of species and habitat destruction worldwide has increased the risk of Prospects of medicinal plants cultivation extinction of medicinal plants, especially in South Africa as a result of the high demand by the increasingly large There is a global increase in the demand of medicinal plant population. products which is estimated to worth R2.9 billion per annum (Sobiecke, 2014). In South Africa a large business venture has been created in the interest of plant derived Conservation strategies of wild medicinal plants medicines with estimated value of R270 million per annum collection (Dold and Cocks, 2002; Wiersum et al., 2006). In KwaZulu-Natal, it is estimated that 1.9 tons of the Extensive studies have been carried out on the indigenous African ginger containing 52,000 plants is conservation and sustainable use of medicinal plants traded annually (Mander, 1998). The aerial part of Khoi- (Larsen and Olsen, 2007; Uprety et al., 2012) and various San`s traditional plant “Buchu” is sold at $56/kg and the forms of recommendations have been made regarding their seeds are sold for R20000.00 per Kilogram (Moolla and conservation, inventorying and monitoring systems to Viljoen, 2008). coordinate both in-situ and ex-situ conservation strategies The ethanolic formulation of Pelargonium sidoides (Hamilton, 2004). extracts (Eps 7630) called “Umckaloaba” is reported to be Ex-situ cultivation is practiced through seed germination the most successful phytomedicine in the world (Van Wyk, and in vitro cloning. Recommendations on medicinal plants 2011; Theisen and Muller, 2012) with a very high market conservation have been developed on both in-situ and ex- potential especially in Germany recording 80 million Euros situ conservation (Huang, 2011) with the knowledge of per annum (Van Wyk, 2011). The economic benefits of their geographical distribution and biological some South African indigenous medicinal plants is an characteristics (Chen et al., 2016). encouragement to promote the cultivation of medicinal Nurseries and nature reserves are measures put in place plants as a viable option for livelihood enhancement that to maintain the medicinal efficacy of plants as bioactive needs to be addressed especially in rural communities compounds can be influenced by intrinsic or extrinsic (Lewu et al., 2007a, b). This will significantly contribute to factors which can then be monitored thereof, while job creation with potentials to improve South Africa’s botanical gardens and seed banks are ex-situ conservation economy (Moolla and Viljoen, 2008; Street and Prinsloo, strategies for future replanting (Mohammed and 2012). Mundanthra, 2013; Maywa, 2016). In this regard, medicinal plants cultivation is gaining Plant diversity database which is available for an update attraction as an emerging sector of self-employment to in all provinces of South Africa has been created in order to subsistence and commercial farmers (Rashid et al., 2014). produce a national flora that will go life on the world wide Also, there is a growing interest in medicinal plant research web by 2020 (Victor et al., 2014). Through the International focusing on cultivation and processing of medicinal plants Union for the conservation of nature (IUCN) red list by some government agencies and academic institutions category, the South African national biodiversity institute especially those that are in high demand within and outside (SANBI) has created a comprehensive national plant red list the country. The optimization of propagation techniques for South African plants (Raimondo et al., 2009). A mandate will definitely be a remedial action to ensure a sustainable Academia Journal of Medicinal Plants; Tanga et al. 171

supply of good quality plant materials to our local environmental factors such as light, temperature, moisture communities and plant-based industries contributing and nutrient availability that are annually unstable (Tang et towards biodiversity conservation and environmental al., 2015). health (Davis et al., 2012). The requirements for seed germination (temperature, soil pH, light, moisture and nutrients) vary between plants and among species which greatly influence germinability. In Introducing medicinal plants cultivation for general, seed germination remains the key to modern commercialization in South Africa agriculture as critical event in determining the success of plant species. To meet up with the demand and supply of Cultivation of medicinal plants plant materials for commercialization, a fundamental understanding of the protocol for seed germination is The cultivation of medicinal plants can be a means of essential to medicinal plant production. Several studies on sustainable supply of medicinal plants materials with different plant species have been carried out by some quality assurance to the market. However, there is little researchers showing the influence of some of these factors available information in this exercise, with much attention on seed propagation (Table 1). on crop cultivation for food security. Currently, the consumption of herbal medicines is widespread due to the presence of useful compounds within plants of medicinal Vegetative propagation potential. This has raised a lot of interest in medicinal research with increasing support from government and This is the multiplication of plants through vegetative parts; industries, with the interest most specifically to it is a fast, expensive and more labour intensive process commercialize the products. Different cultivation practices with a lot of technical applications compared to seed such as planting date, fertilizer application, irrigation propagation. Vegetative propagation can be through systems and harvesting methods need to be optimized to cuttings, grafting, budding and micro propagation. It is a improve growth, yield and quality of medicinal plant process of plant multiplication in which a portion or materials. Cultivation of medicinal plants with the use of fragment of the plant body functions as a propagule and controlled environments will be a viable alternative that develops into a new individual (Megersa, 2017). offers the opportunity to overcome the problems that are Among the different methods of vegetative propagation, inherent in herbal extracts such as extract variability, cutting is regarded as the most preferred and best method contamination, misidentification, instability and a means to as it retains and conserve the genetic diversity of the plant manipulate the yield of bioactive compounds. However, the (Dumroese et al., 2016). Cuttings are any vegetative parts of propagation of some medicinal plants in a new habitat may plants that can fully develop to the parent materials when be challenging due to local adaptation of some medicinal subjected to favorable condition for regeneration plants to their natural environments (Lewu et al., 2007b) (Hartmann et al., 2002). and low germination rate (Vines, 2004). Several studies on vegetative propagation of medicinal Also, specific information about the requirements for plants have been investigated by some researchers such as: seed germination, growth and pollination is usually not Chandra et al. (2015) who reported highest rooting available since these plants are introduced into cultivation. percentage in the macro propagation of Holostemma Ade- Propagation success of new plants in an environment will kodien, tested in vermiculate and vermicompost growth depend on the understanding of the basic principles of media using different concentrations of IBA and IAA growth plant propagation which usually takes place through seed hormones. and vegetative propagation (Hartmann et al., 2002). Danu et al. (2015) investigated the sprouting and rooting percentage of Paris polyphylla Smith, using various soil composition with different concentrations and Seed propagation combinations of IBA and GA3 hormones (50, 100 and 150 mg/L) treatments. Combination of 100 mg/L GA3 and 100 Seed propagation is a means of large scale multiplication of mg/L IBA demonstrated highest sprouting and rooting plants which takes a longer period for plants to reach percentage in soil: loam: sand (3:2:1). maturity. It is a less expensive process in which the crop stands a chance to compensate for the time lost in seed germination. Seed germination is a vulnerable stage in the Cultivation of medicinal plants: A solution for life cycle of pants (Kigel, 1995). biodiversity conservation in South Africa It is the process of reactivation of metabolic machinery of seed which starts with inhibition in completion with radicle The cultivation of South African medicinal plants has emergence from the seed coat giving rise to a seedling. It is increased over the years, due to their high demand in the a complex phenomenon which is influenced by genetic and market by herbal practitioners, pharmaceutical industries Academia Journal of Medicinal Plants; Tanga et al. 172

Table 1: Advances on factors that influences seed germination potential.

Study Findings of the study Sources Investigated the effects of water and Temperature diversity influences germination capacity in many temperature on seed germination and species, relating to different strategies adopted as a consequence of (Moral, 2013). emergence as a seed hydrothermal time the heterogeneity of the habitat and microclimatic seasonality model intrinsic to their ecosystems Seed age, temperature, light and pre-chilling conditions had an Influence of seed source, pre-chilling, light and influence on seed germination of pelargonium sidoides. At (Lewu et al., temperature on the germination of South temperatures higher than 25°C germination was reduced by 60% 2010). African Pelargonium sidoides. and at pre-chilling there was a drop by 29% in seed germination compared to other treatments. Germination percentage of bush tea differed with the temperature Investigated the effects of seed germination treatments, with the highest (75%) at 20 - 25°C. There was a high and vegetative propagation of bush tea germination percentage at constant temperature than at alternate (Araya, 2005). (Athrixia phylicoides), temperature and in a continuous light than alternate light. Condition. Saline water had an influence on growth attributes, an efficient antioxidant mechanism was present in quinoa, activated by salts Effect of saline water on seed germination and during germination and early seedling growth and total antioxidant (Panuccio t al., early seedling growth of the halophyte quinoa capacity was higher under salt stress than in water. Also, osmotic 2014). and ionic stress factors had different degrees of influence on germination and development. This study has demonstrated that the hydrothermal time model Hydrothermal time models for conidial framework developed to describe the effects of temperature and (Barth et al., germination and mycelial growth of the seed water potential on physiological processes in seeds can also be 2005). pathogen Pyrenophora semeniperda successfully applied to germination and growth processes in ascomycete seed pathogen Temperature requirements for seed The different stages of development, from embryo growth to leaf germination and seedling development development, occur continuously in response to different (Vandelook and determine timing of seedling emergence of temperatures. Differences in timing of emergence between the Assche, 2008). three monocotyledonous temperate forest three species studied are caused by a subtle difference in spring geophytes temperature effects on germination and seedling development Toxicity of salts varies with environmental conditions, treated Interactive effects of salt, light and seeds were better in moderate temperatures. The salts did not temperature on seed germination and (Zehra et al., affect viability of seeds which probably entered into dormancy. recovery of a Halophytic grass-Phragmites 2013). During extended exposure to high salinity and temperature stress, karka seeds wereprevented from germination.

and the increasing awareness of medicinal plants identification prevent the risk of contamination, steady conservation. Opportunities have been created for farmers supply of plant materials, control of post-harvest handling, to cultivate medicinal plants which have helped to reduce effective monitoring of products standard, easy plant the issue of competition between farmers (Reinten and certification procedure, minimized batch-batch product Coetzee, 2002). Research projects have been conducted in variability and provides a platform of agreement between South Africa on the cultivation and commercialization of wholesalers and growers (Mathe and Mathe, 2008). indigenous plants materials to reduce pressure of wild Cultivation of medicinal plants provides the opportunity plants collection. A handful of indigenous South African to optimize the production of secondary metabolites of medicinal plants are under cultivation in the different interest with information on the best season and time of provinces (Table 2). harvest and ultimately increase volume. Herbal medicines and supplements derived from medicinal plants are usually assessed for quality assurance to ensure their safety before Cultivation of medicinal plants: A possible solution of commercialization (Govindaraghavan and Sucher, 2015). product qualityand commercialization Quality assessment measures need to be put in place to address safety and efficacy as well as, consistent Medicinal plant cultivation is a solution to meet up with the monitoring of the entire value chain to ensure the delivery demand in the market and an advantage for pharmaceutical of quality finished products to local and international industries and herbal practitioners to have control over herbal markets. However, this depends on the processing their raw materials (Martins, 2014). Providing a reliable and storage conditions, which may have an influence on Academia Journal of Medicinal Plants; Tanga et al. 173

Table 2: Cultivation practice and uses of some South African medicinal plants species.

Common Species Propagation Place of cultivation Parts used Uses name Siphonochilus Secondary roots and Flu, cold ,malaria, charm, appetite African ginger Seeds and rhizomes Mpumalanga, Limpopo aethiopicus rhizomes suppressant and sedative Eriocephalus Seeds, cuttings, layering Wild rosemary Western cape, Eastern Cape Leaves Asthma, throat and lung infections africanus and division of roots Northern Cape, Eastern Cape, Fever, ulcer, poor appetite, diabetics, cold, flu, Sutherlandia Leaves and young Cancer bush Seeds and cuttings KwaZulu Natal, Western Cape, gastritis, cough, asthma, rheumatism, urinary frustescens stem Mpumalanga tract infection, stress, anxiety Treatment of liver, kidney and bladder Harpagophytum Northern West, Northern Cape, Free Devil`s claw Seeds, secondary tuber Root diseases, stimulate appetite and for procumbens state indigestion Eastern cape, KwaZulu Natal, Hypoxis Tuber, leaves and Treatment of urinary tract infection African potato Seeds Mpumalanga, Limpopo, Gauteng, hemerocallidea bulbs ,testicular tumor heart weakness North West, Free state Rocky grassland of the Eastern cape, Rhizome, leaves, Fever, rheumatism, asthma, constipation , Tulbaghia violacea Wild garlic Seeds KwaZulu Natal, Limpopo bulbs flower cough and cold Limpopo, Free State, Mpumalanga, Roots, leaves, barks, Moringa oleifera Drumstick tree Seeds and cuttings Headache, ulcers, diarrhoea, wounds KwaZulu Natal, Gauteng immature pods Cough, chest pain, bronchitis, fever, sore Pelargonium sidoides Kalwerbossie Seeds and cuttings Eastern cape, Free state, Gauteng whole plant throat, dysentery, diarrhoea Abdominal pain, constipation, cancer, Limpopo, KwaZulu Natal, Northern Warburgia salutaris Pepper Tree Seeds and cutting Whole plant rheumatism, stomach ulcer, malaria, Gauteng influenza Pineapple Limpopo, Mpumalanga, Free State, Eucomis antumnalis Seeds and leaf cutting Bulb Fever, stomach ache, colic, flatulence, syphilis flower Eastern Cape Western cape, Southern KwaZulu Aloe ferox Bitter aloe Seeds and stem cuttings Natal, South Eastern part of Free leaves Arthritis, eczema, hypertension, stress, State All provinces of South Africa except Leaves, stems and Cough, fever, headache, loss of appetite, Artemisia afra wormwood Roots and stem cutting in the Northern cape province roots intestinal worms

Source: (Mahomoodally, 2013; Street and Prinsloo, 2012; McMaster, 2007; Herbert, 2006; Joffe, 2005). Academia Journal of Medicinal Plants; Tanga et al. 174

the quality of final product. processing conditions will help to increase the market value Product quality depends on active ingredients which are of medicinal plant products. influenced by intrinsic and extrinsic factors. These factors bring about major changes in metabolites creating differences in the final content during every production. It Influence of regulatory policy on safety and quality of is therefore of utmost importance to understand the medicinal plants products dynamics in secondary metabolite for consistency in chemical profiles as well as, biological activities of The use of many plants products as food or dietary medicinal plants. Recently, some scientific investigations supplement is associated with some problems of have been carried out on the synthesis of plant secondary classification in some countries (Martins, 2014). As a result, metabolite in response to various factors that deviate from quality tests and production standards tend to be less the optimal production of plant secondary metabolites controlled and, in some cases, traditional health (Table 3). practitioners may not be licensed. The safety of medicinal plant product is imperative to the general public (Kasilo and Trapsida, 2011). All manufactured herbal products are Challenges in medicinal plant cultivation required to be licensed as “traditional herbal medicinal product” (Raynor et al., 2011; UNESCO, 2013). Like Medicinal plants are widely used traditionally throughout orthodox medicines, it is compulsory that they are human development in the treatment of various illnesses as accompanied by a comprehensive information like a source of primary health care in most communities. precaution, prescription, side effect, storage and regulatory However, the source of plant material is mostly dependent information (Martins, 2014). on the wild, except recently, where there is a growing However, in the developing countries where many attention towards medicinal plants cultivation for unregistered and poorly regulated herbal products are sold biodiversity conservation, enhancement of secondary freely on the market with little or no restraint, license metabolite of interest, product quality and for assurance of cannot be obtained for some herbal medicines. steady supply of plant materials. However, this is Furthermore, the myth that natural products are not associated with some unforeseen challenges that may arise poisonous and are devoid of adverse effects often lead to without expectations. wrong usage and unrestrained intake which may result in In medicinal plant cultivation, the future for some less poisoning and acute health problems. This is not limited to known species are unpredictable; some of them being developing countries, but also exists in highly developed perennial will require several years for maturity before countries, where the general public often resorts to harvesting and therefore investment in them could “natural” products without any proper information on the represent a considerable commercial risk (Canter et al., side effects; especially in the case of excessive use 2005). Medicinal plant cultivation goes with a series of (UNESCO, 2013). questions like the accessibility of plant materials in the In South Africa, advances have been made in the quality wild, disease susceptibility, labour cost and adaptation to a control of medicinal plant products by creating a Medicinal new environment may be slow. In a situation where there is Control Council to ensure the quality control of herbal an excess of a particular medicinal plant in a very large medicines, promote the safety of high-quality traditional population in the wild, it becomes very easy for medicinal medicine, and to contribute in the capacity building of collectors to harvest these materials with little or no cost in traditional healers (Felhaber and Gericke, 1996). the wild to sell at cheaper prices. This makes it difficult and unworthy to such a plant to be cultivated with the application of labour cost of cultivation to sell at a higher Conclusion price of which buyers will prefer to buy at cheaper price from those collectors from the wild. The high and growing interest of medicinal plant products Agro-environmental conditions of cultivated medicinal as a means of primary health care system in both developed plants are usually not the same to that of the wild habitat. and developing countries gives a prospect to medicinal However, secondary metabolite biosynthesis is induced by plants as a suitable substitute for crop cultivation, an the extra-optimal influence of biotic and abiotic factors option for a source of employment and livelihood where optimal environment will tend to increase biomass enhancement, with little or no competition in product production, rather than the synthesized secondary quality, efficacy and commercialization process. The metabolite usually needed to cope with stress (Pavarini et manipulation and optimization of secondary metabolites of al., 2012). interest will rest be assured for a consistent supply of plant Also, post-harvest processing and market availability are materials, price affordability and efficacy in their functions. very critical because their negligence would lead to an Propagation process will be accompanied with modern irreversible quality loss of raw materials. Thus, good technology to meet up with the high demands of Academia Journal of Medicinal Plants; Tanga et al. 175

Table 3: Factors that influences the synthesis of secondary metabolites in plants.

Studies Finding of the of the study References Biotic and abiotic stresses are tools to increase health related properties of plant materials and understanding elicitation of induced metabolites and Quality from the field: The impact of environmental factors as quality their lifetime is fundamental to quality assessment of secondary metabolite (Ncube et al., 2012) determination in medicinal plants production. Notwithstanding, quality is indeed growing out in the field, harvesting and processing methods. Bioactive compounds in RGT seedlings could be enhanced significantly The improvement of bioactive secondary metabolites accumulation in Rumex through co-culture with fungus Aspergillus sp. However, there is the need (Ding et al., 2018). gmelini Threz through co-culture with endophytic fungi for further research for larger scale bioactive secondary metabolites production. Secondary production in the root and rhizomes of Synopodophyllum Influence of ecological factors on the production of active substances in the anti- hexandrum are greatly influenced by environmental factors contributing to (Liu et al., 2013). cancer plant Sinopodophyllum hexandrum (Royle) ST Ying a geographical differences in different production location Secondary metabolites of the plant materials assessed for seasonal variation Seasonal variation in the production of secondary metabolites and antimicrobial showed concentration differences as well as differences in antimicrobial (Thanga , 2011). activity of two species used in Brazil traditional medicine activities. Environmental factors such as temperature, humidity, light intensity, water, mineral and carbon dioxide influences the growth of plants secondary (Ramakrishna and Influence of abiotic stress signal on secondary metabolites in plants metabolites production. Drought and freezing temperatures can cause Ravishankar, 2011). adverse effects on growth of plants and their productivity. Higher alkaloid levels were recorded for plants under salt or drought stress, Investigated on effects of salts and drought stress on alkaloid production in with levels of ergonovine being higher than those of ergine. Concentrations (Zhang et al., 2011). endophyte-infected drunken horse grass (Achnatherum inebrians of both alkaloids increased over the plant growing period Growing conditions had an influence on the quali-quuantitative profile of Influence of growing conditions on metabolite profile of Ammivisnagaumbels the secondary metabolites, with hydroponics culture having significant (Sellami et al., 2013). with special reference to bioactive furanochromones and pyranocoumarins increase in the active principal components Cultural practices such as fertilization and planting density have an Effects of cultural practices and environmental conditions on yield and quality of influence on growth and productivity, with fertilization improving growth, herbal plants: prospects leading to research on influence of nitrogen fertilization, (Tshivhandekano et total polyphenol, tannins and antioxidant content of herbal tea. Nitrogen planting density and eco-physiological parameters on yield and quality of field- al., 2005). fertilization increases the production of new shoots and content of grown bush tea (Athrixia phylicoides DC) nitrogenous compounds, plant density also increases productivity. Academia Journal of Medicinal Plants; Tanga et al. 176

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