**3. PFASs as a threat to sub-Saharan African medicinal plants**

For centuries, medicine plants have played a therapeutic role in the lives of millions of people in developing countries worldwide, and in sub-Saharan African regions, in particular. In addition, it has been reported that, due to their bioactive organic chemical compounds content, also referred to as phytochemicals, these plants have been able to play a defensive role against major chronic ailments in both host-metabolic or genetic dysfunctional and infectious diseases, thus making them beneficial for human and animal health [86, 87]. In sub-Saharan African countries (**Figure 1**), millions of people depend on medicinal plants for their primary healthcare therapy for obvious reasons such as, these people are inhabitants who live closer to the natural vegetation such as forests, with an estimated 216,634,000 ha of closed forest [12] and savannas\_ the later having been reported to be rich in biodiversity with an estimated 71% of vegetation of these ecosystems being medicinal plants, the easy and free access to these plants, as well as the prohibitive cost of orthodox products [87, 88].

Furthermore, the reviewed literature has reported that many different plant species might be used to treat specific ailment(s) in various sub-Saharan African countries, as well as a particular plant being used for the same kind of illness in two or more countries, thus implying the variety and abondance of these plants in the region and the history that these countries previously shared. For example, a recent article reported on antimalarial medicinal plants used in Benin, Burkina Faso, Cameroon, DRC, Ethiopia, Gabon, Ghana, Guinea, Kenya, Mali, Namibia, Nigeria, Uganda, Senegal, South Africa, Rwanda, Togo, Zambia and Zimbabwe (thus representing all the sub-Saharan regions, see **Figure 1**), with the following plant species used in numerous countries, namely: *Azadirachta indica* (Benin, Burkina Faso, Ghana, Guinea, Ethiopia, Kenya, Nigeria, Togo, Uganda and Zimbabwe), *Nauclea latifolia* (Benin, Cameroon, Gabon, Ghana, Guinea, Kenya, Nigeria, Senegal and Togo), *Carica papaya* (Benin, Ghana, Guinea, Nigeria, Togo, Uganda, Zambia and Zimbabwe*), Cassia siamea* (Benin, Burkina Faso, Ghana, Guinea, Nigeria, Togo,

#### *Medicinal Plants Threatened by Undocumented Emerging Pollutants: The Sub-Saharan African… DOI: http://dx.doi.org/10.5772/intechopen.103825*

Zambia and Zimbabwe)*, Ficus sur Forssk* (Burkina Faso, Gabon, Guinea, Kenya, Namibia, Nigeria, Togo and Uganda), *Cassia occidentalis* L*.* (Benin, Kenya, Ghana, Namibia, Nigeria, Zambia and Zimbabwe), *Jatropha curcas* L (Benin, Ghana, Guinea, Ethiopia, Nigeria, Uganda and Zambia)*, Maytenus* sp. *nov.* A. (Benin, Guinea, Kenya, Nigeria, Senegal, Sudan and Zambia), *Tamarindus* indica L. (Benin, Ethiopia, Guinea, Kenya, Uganda, Togo and Zambia)*, Vernonia amygdalina* (Benin, Ghana, Kenya, Namibia, Nigeria, Uganda and Zambia), *Tithonia diversifolia* A. Gray (Burkina Faso, Guinea, Nigeria, Uganda, Rwanda and Zimbabwe), *Adansonia* digitata L. (Benin, Namibia, Nigeria, Togo and Zambia), *Momordica foetida* Schumach. (Ethiopia, Ghana, Uganda, Zambia and Zimbabwe), *Securidaca longepeduculata* Fresen (Namibia, Nigeria, South Africa and Zambia), and *Flueggea virosa* (Willd.) Voigt (Benin, Kenya, Togo and Uganda), *Ximenia americana* L. (Guinea, Kenya, South Africa and Zambia), and *Zanthoxylum chalybeum* Engl (Kenya, Rwanda, Uganda and Zambia) [11]; and for the management of human immunodeficiency virus (HIV) and other sexually transmitted infections (STIs) in the sub-Saharan region, *Ximenia americana* has been in use (Zambia, Uganda and Kenya), and *Azadirachta indica* (Uganda and Kenya) [89–91]. Similarly, numerous studies have highlighted the antidiabetic potential of several hundreds of sub-Saharan African medicinal plants [4].

Additionally, a valuable review article has highlighted the commercial importance of African medicinal plants, including 13 species (i.e., *Catharanthus roseus*, *Centella asiatica*, *Coffea arabica*, *Cissampelos pareira*, *Cyclopia genistoides*, *Pausinystalia johimbe*, *Synsepalum dulcificum*, *Sclerochiton illicifolius*, *Strophanthus gratus*, *Physostigma venenosum*, *Thaumatococcus daniellii, Voacanga africana* and *V. thouarsii*) which are sources of commercially important chemical constituents, and has, to some extents, represented approximately 10% of commercially developed medicinal plants [13]. The review has further suggested that presently Africa is home to more than 80 beneficial commercial medicinal plant species that are on international markets, and this, in our view confirms the argument that the demand for medicinal plants, including African, is increasing at an alarming rate [7]. Interested readers are encouraged to read this remarkable review article [13] as it depicts a well-informed selection of most popular and important medicinal plants distributed in the different sub-Saharan regions (**Figure 1**).

Nevertheless, albeit the promising prospects of these plants as alluded to, knowledges on African medicinal plants are still very limited in comparison to other societies, such as the Chinese and Indian; this is so because, unlike in China and India where medicinal plants have extensively been researched and documented, studies of African medicinal plants have not been taken seriously. For example, recent evidence from sub-Saharan-southern African region highlighted 257 plant species from this region that are used traditionally for the treatment of viral respiratory ailments, but only one of these plants has this far been tested for its ability to constrain respiratory viruses by means of its ethnobotanical usage [92]; while of the 555 medicinal plants identified to treat inflammation and pain, from the same region, only few have been relatively screened for their anti-inflammatory properties, which prompted the researchers to recommend that further studies be undertaken in that regard [93]. Substantial, this lack of seriousness in this domain has led to information on African medicinal plants either being unavailable or fragmented and, in the end, incompletely documented [12, 13].

Certainly, the challenges that sub-Saharan African medicinal plants are subjected to are numerous [4]. For instance, it has been indicated that there's an urgent need to increase the documentation on sub-Saharan African medicinal plants because of their accelerated losses due to anthropogenic activities [12]. For example, the rate of the loss of natural forest cover or deforestation on the African continent is one of the highest globally [7, 12]. Basically, the global deforestation rate stands at 0.6%, but this rate is at 6.5%, 5.0% and 2.1% in sub-Saharan Africa for countries such as the Cote d'Ivoire, Nigeria and the DRC respectively [12, 94]. Additionally, sub-Saharan African medicinal plants are affected by unsustainable harvesting methods [7, 11, 13, 16, 87], fires, wattle expansion or eradication program and grazing [7, 87], coupled with human settlement expansions, including urbanization, as well as inexistent or weak legislations and/or enforcement failure of existing rules and regulations [16].

Moreover, the most recent challenge threatening the prospects of sub-Saharan African medicinal plants, in our opinion, is the contamination of these plants by PFASs. Hence, unlike in the developed world, where the assessment and monitoring of PFASs prevalence in the natural environment are at an advanced stage [4], it is only recently that PFAS studies from the sub-Saharan African region have started emerging [54]. Thus, during the last two decades there has been reports on PFAS from South Africa, Nigeria, Kenya, Ethiopia, Ghana, Burkina Faso and Ivory coast, Tanzania and Uganda [4, 54, 95, 96]. It is worth mentioning that the continent has over 50 countries, which suggests that PFAS studies are still limited on the continent at large. All available evidence has reported higher level concentrations of specific PFASs in analyzed samples, compared to allowed international standards. For example, higher levels of PFOS and PFOA were reported in tap water from Ghana, but lower in tap and bottled water from Burkina Faso [95]. Similarly, PFASs have been reported in wastewater from wastewater treatment plants (WWTPs) and ultimately in several surface water systems in sub-Saharan Africa, including in South Africa, Kenya, Nigeria, Ghana and Ethiopia [54, 95–97]. Hence, it can be argued that inefficiently treated wastewater represents a risk to plants, including medicinal plants, to which PFAS-contaminated water is or might be applied to. And this is substantiated by the literature that has confirmed that WWTPs are PFAS-contamination hotspots, are considered as the most common point sources of PFASs to surface water [98, 99]. Similarly, available evidence has indicated that the cultivation of medicinal plants at a commercial scale has started emerging from the sub-Saharan African region, with countries such as South Africa, Uganda, Kenya, Tanzania and the DRC having taken the initiatives toward the commercial cultivation of these plants, with high probabilities that surface water (e.g., river water) is used or luckily to be used, like it is the case in South Africa, to irrigate the lands on which medicinal plants are planted with such water, to alleviate the burden of water shortage, for instance. This is a huge potential risk and a threat to medicinal plants.

Furthermore, there are considerable evidence on the prevalence of PFASs in edible plants we have previously alluded to, in the general environment worldwide [80–85], but the state of these substances, in this regard, in the sub-Saharan African region remains largely unknown and undocumented. However, several countries from this region have been commercially trading with world leading economies (e.g., China and USA) from which PFASs have been reported not only in their natural environments, but also in consumer products that are imported from these world greatest economies by their African commercial patterners [58, 79]; this implies the potential prevalence of PFASs in the general environment of this region as previously alluded by Ssebugere et al. [95] who suggested that the likelihood of PFASs in African environments would certainly be due to the uncontrollable and unregulated importation of PFAS-carrier products from these mass manufacturers to the African countries. Further studies are overdue to substantiate these conjectures, which, if confirmed, represent substantial threats to the general African environment.

*Medicinal Plants Threatened by Undocumented Emerging Pollutants: The Sub-Saharan African… DOI: http://dx.doi.org/10.5772/intechopen.103825*

Similarly, available data further suggest a greater need for investigations to be conducted on the uptake of these compounds by medical plants. In fact, to our knowledge, there is only a single article that has recently reported on the susceptibility of medical plants to PFASs, with the African marigold (*Tagetes erecta* L.) as a typical example [100]. The results from the later study have become a wakeup call, as they suggested medicinal plants as possible conduits of PFASs, including PFOA (94.83 ng/g), PFOS (5.03 ng/g) and PFBS (1.44 ng/g), into humans; and thus represent a huge threat to the entire potential medicinal plants industry of the sub-Saharan African region; and the situation is expected to be exacerbated as the continent embarks on developmental trajectories. Therefore, for this region to remain certain that it maintains its remarkable medicinal plants history and keep its population safe, we are of the opinion that studies, in this regard, should be expanded and diversified in the region, in order for a database of these chemicals on medicinal plants to be efficiently established for the whole of the sub-Saharan African region.

### **4. Conclusions**

The use of medicinal plants to combat diseases and illnesses from which humans suffer is not new. It can thus be said that these plants have a long history. In sub-Saharan Africa the history of medicinal plants is remarkable, huge and divers, transmitted by word of mouth from one generation to another using the thousands of dialects present in the region. Owing it to its tropical and subtropical geographical positions, sub-Saharan Africa is said to be home to an enormous biodiversity of medicinal plants, with over fifty thousand plant species, a quarter of which is well known for their curative potentials. Notwithstanding these possibilities, the region still lacks its own drugs on the global markets due to the limited and/or small-scale type of cultivation of medicinal plants still in practice in the region, coupled with several other challenges that medicinal plants are faced with, including not being sufficiently undocumented, deforestation, conservation inefficiencies, overexploitation or overharvesting, etc. Hence, there isn't any doubt that medicinal plants in sub-Saharan African region are subjected to several encounters. But the most recent of these encounters have been the potential threats from emerging pollutants, i.e., PFASs. These substances are the results of anthropogenic activities unlike their predecessors, the heavy metals, which are naturally find in the environment. To date, there has been over 5000 PFASs manufactured since their dawn in the 1950s. During the manufacturing process that gives life to PFASs, they're given unique properties that make them wanted by several manufacturers of consumer products. Unfortunately, due to these compounds being heavily applied in industrial processes, they have now been detected in different environmental matrices, including water, soil and plants, as well as in animals. PFASs have been even detected in samples from remote areas, far from the places where they were manufactured, with PFOA and PFOS being predominantly studied, owing it to their health concerns. Regardless of PFASs being extensively researched and documented in different parts of the world, the chemicals have remained undocumented in sub-Saharan Africa, to a large extent. This situation is highly concerning in the context of medicinal plants of this region, because PFASs have been proven to translocate and bioaccumulate in plants, and linked to numerous severe diseases, including cancer and diabetes. This state implies that plants, medicinal plants in this case, being a possible pathway through which humans get exposed to these human-made substances. And with medicinal plants being the first line of

defense to combat diseases, illnesses and other daily health needs for millions of low-income people from sub-Saharan Africa, there is cause for serious concern. It is therefore recommended that PFAS studies be expanded and diversified in sub-Saharan Africa. Future studies should also investigate the prevalence of novel or the so called PFAS-substitutes in African environments. The region needs trade-agreements and regulations that make provisions for PFASs from countries with the reputation of manufacturing these chemicals and their alternatives. To valorize its current medicinal plant diversity, the region needs to shift from small to large-scale cultivation of medicinal plants. Routine-based assessment and monitoring of PFASs, their precursors and alternatives in general African environments is also recommended, with an emphasis on the cultivation, harvest or collection, and storing of medicinal plants in areas free of any possible contamination.
