Knowledge and Traditional Uses of Some Aromatic and Cosmetic Plants Species in the Western Highlands of Cameroon ()
1. Introduction
Plants have always played a major role in the survival of humanity and have been traded between countries for years because of their ability to synthesize a large number of complex organic molecules with biological activities [1]. This is the case, of Prunus africana in Cameroon, whose fresh bark has been exported since the 1980s, nearly 1500 tonnes in 1980 and 2000 tonnes in 1990 [2] [3]. This trade has gradually given rise to rapid exploitation of the species, resulting directly in an alarming destruction and regression of supporting ecosystems [4] [5]. According to FAO (1995) and [6] the preservation of the biodiversity and the sustainable and rational use of natural resources is becoming imperative without which the sustainable development of future generations cannot be ensured.
The Convention on Biological Diversity (CBD), ratified in 1992 in Rio, is an international treaty, which recognises the sovereign right of states over their biological resources and reaffirms their responsibility for the conservation and sustainable use [7]. Because of some limits of this treaty, member states met in 2010 at the 10th Conference of the parties in Nagoya and adopted a protocol on Access and Benefit Sharing (ABS) from the utilisation of genetic resources. This protocol takes into account the intellectual property and traditional knowledge of indigenous peoples and local communities. Indeed, the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) recognises that the culturally and socially diverse environmental knowledge of indigenous people and local communities contributes greatly to the assessment and formulation of policies on biodiversity and ecosystem services, and needs to be taken into account in the process of conservation and sustainable use of biological resources [8]. Therefore, the Nagoya Protocol on access to genetic resources and fair and equitable sharing of benefits arising out of their utilization appears to be the ideal solution [9]. According to the International Union for Conservation of Nature (IUCN), the ABS process is a concrete example of valuing biodiversity and ecosystem services, but also a good way to promote conservation and sustainable use of natural resources.
Cameroon has one of the greatest biological diversities in the Congo Basin with aromatic and medicinal plants that are a source of essential oils. Despite this wealth, which could constitute an important source of revenue as confirmed by the high global demand recorded in recent years [10], the country is still struggling to set up value chains for these products according to the ABS principles. However, Cameroon’s commitments to ABS have been formalized in a legal framework adopted by its government in 2021. Since 2012, the pilot project for the development of the Echinops giganteus plant in the Bamboutos Mountain has enabled the Cameroonian government to take a pragmatic approach to achieve this result. As E. giganteus is certainly not the only species that can be exploited in the area, it was necessary to have an idea of the species that can potentially be exploited under the ABS process. Knowing that the virtues of plants and their uses are very old and are transmitted through generations over time, ethnobotanical surveys seem to be one of the reliable approaches for the discovery of new compounds likely to be valorised by the ABS process [11] [12]. The present study is a contribution to the valorisation of natural resources used in the Western highlands of Cameroon following the ABS principles. The general objective of the work is to make an inventory of the ancestral knowledge held by the populations of Western Highlands of Cameroon on aromatic and/or cosmetic plant resources. More specifically, plant resources used as aromatics and/or cosmetics were identified and their associated traditional knowledge was presented.
2. Materials and Methods
2.1. Study Site
The Western highlands of Cameroon is located between latitudes 05˚20' and 7˚00'North and between longitudes 10˚03' and 12˚00'East. This region is characterised by a diversified relief with altitudes varying between 800 and 2740 m. The climate is of the Sudano-Guinean type with temperatures varying from 16˚C to 27˚C and relative humidity between 40% and 100%. The average rainfall is 1900 mm/year. The soils are mainly red ferralitic soils, though hydromorphic soils can also be observed. The vegetation is essentially made up of dense forests and swamps [13] [14]. The data collection areas are shown in Figure 1.
2.2. Ethnobotanical Surveys
Ethnobotanical surveys were conducted between July 2017 and May 2018 among traditional practitioners, herbalists and healers in 12 localities spread over five divisions as presented in Table 1. Semi-structured questionnaires were used with the assistance of traditional practitioners. Information was collected on the aromatic and cosmetic plants exploited, their vernacular names, the parts used, the activities of the local population in relation to the management and sustainable use and the importance of cited species in food, health, and socio-cultural life.
2.3. Collection and Identification of Species
Species were identified in situ with the help of botanists. Fertile samples of unidentified species were collected with secateurs, filmed with a camera, wrapped in newspaper, pressed, dried and further identified at the National Herbarium in Yaoundé.
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Figure 1. Location of data collection areas in the Western Highlands of Cameroon.
2.4. Data Processing and Analysis
XLSTAT software was used for data analysis. The importance of each species was evaluated from the relative frequency of citation [15] calculated as follows:
(1)
where Nu represented the number of people who cited the species and Nt, the total number of surveys.
Similarly, the ethnobotanical importance of the identified aromatic plants was assessed by calculating the diversity index and the fairness index of the survey.
The diversity index (ID) indicates the number of respondents who use the species and how this knowledge is distributed among them [16]. It varies between 0 and 1 and is obtained using the following formula:
(2)
where Ux is the number of uses cited by a respondent and Ut the total number of uses.
If ID is low (< 0.5), then few people know the species; but if ID is high (> 0.5), then the species is well known.
The fairness index (FEI) measures the degree of agreement between respondents regarding the different uses of the species [16]. It varies between 0 and 1 and is obtained using the following formula:
(3)
where IDmax is the value of the highest diversity index found.
3. Results
3.1. Information about the Respondents
A total of 251 individuals having knowledge on aromatic and/or cosmetic plants were surveyed. Table 2 presents the socio-cultural characteristics of the people surveyed in each of the selected localities. Among them, 82.1% were males while 17.9% were female. The age of the respondents varied between 25 and 81 years. People over 50 years of age were the most represented with 56.2%. Of all the people surveyed, traditional practitioners were the most represented (38.6%), followed by herbalists (31.1%) and healers (25.1%). In all the localities surveyed, the Bamilékés ethnic group was the most represented with 55.3%, followed by the Bamoun with 29.5%.
3.2. Floristic Composition of the Plants Recorded
A total of 103 species of aromatic and/or cosmetic plants were identified during the survey. They were distributed in 81 genera and 46 families, the most represented of which were: Lamiaceae (18 species), Asteraceae (10 species), Euphorbiaceae and Zingiberaceae (7 species each), the Fabaceae (5 species), Apiaceae and Piperaceae (4 species). Bignoniaceae, Anacardiaceae, Campanulaceae, Periplocaceae, Olacaceae, Myristicaceae, Ruscaceae, Guttifereae, Passifloraceae and Acanthaceae were the less represented families with one species each.
3.3. Morphological Types
Grasses represented 66% of the species recorded, followed by trees (21%), with the shrubs and lianas representing only 10% and 3% respectively (Figure 2).
3.4. Usage Categories of Identified Species
Several categories of uses were identified, namely: medicinal (56.31%), food (6.80%), cosmetic (10.68%) and cultural (1.94%) (Figure 3). In all categories of
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Table 2. Summary of respondents’ socio-cultural information.
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Figure 2. Proportion of the morphological types of aromatics and/or cosmetics plants recorded.
use, leaves (111citations) were the most used organ followed by barks (32 citations), fruits (27 citations) and roots (25 citations).
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Figure 3. Proportions of the different categories of use of the listed species. Caption: Med: medicine, Med + Fd: medicine + food, Cos: cosmetics, Med + cos: medicine + cosmetics, Ali: food, Cult: cultural, Med + Fd + cos: medicine + food + cosmetics.
3.5. Relative Frequency of Citation, Diversity and Equitability of Use of the Plants Listed
The results of the various indices and the frequency of quotations for each species surveyed are presented in Table 3. The 10 most cited species were Eryngium foetidum (9.52), Chenopodium ambrosioides (5.56), Ocimum gratissimum (5.56), Piper umbellatum (4.37), Cinnamomum zeylanicum (3.97), Aframomum melegueta (2.78), Citrus limon (2.38), Costus afer,Cyperus rotundus and Mondia whitei (1.98 each). Among the least cited species are Satureja punctata,Pycnostachys meyeri,Pychnantus angolensis,Robus forticorpus,Plectranthus madagascarensis,Premna zenkeri,Physalis angulata,Peperomiavulcanica,with a citation frequency of less than 0.5.
Overall the diversity index values where below 0.5 and varried between 0.02 and 0.22, which means that the plants are not very well known by the respondents.
Low values for the species use equitability index were recorded. This reflects a low degree of homogeneity of knowledge among the respondents. However, the highest values were observed for the 10 species mentioned above, which indicates that knowledge of the uses of these species is evenly distributed among the surveyed populations.
3.6. Traditional Knowledge Associated to the Use of the Identified Plants
The traditional knowledge held by the populations of the different localities in relation to aromatic and cosmetic plants is presented in Table 4 below. This table shows that:
• The populations make use of the genetic resources of aromatic and cosmetic plants in several fields, but especially to treat illnesses such as coughs, sexual weakness, cysts, diabetes, prostate, rheumatism, filaria, insomnia, female sterility, jaundice, scabies, haemorrhoids, arterial hypertension, asthma, but also for mystical-magical illnesses;
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Table 3. Frequency of citation, diversity, and equitability of uses of the identified aromatic species.
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Table 4. List of species identified with their use patterns.
• Decoction is the most widely used method of preparing phytomedicines;
• The oral route is the most commonly used method of administering phytomedicines. However, for dermatoses or diseases related to the epidermis (threadworms, scabies, shingles, etc.), poultices and baths are the most popular methods.
4. Discussion
The results (Table 2) showed that the majority of respondents were male (82.1%) and range in age from 25 to 81 years. The high representation of men may be due to the fact that the surveys were more oriented towards traditional medicine professionals. Moreover, it would seem that there are very few women in this sector of activity because women who frequently use plants with medicinal potentials are very badly regarded [17]. In previous works, some authors justified the low representation of women in the traditional health sector by the fact that there is an ancestral belief that women’s role in society is limited to taking care of the home and family [17] [18]. Ngoule and collaborators found similar results (60.41% men) in their surveys of essential oil medicinal plants in Douala markets [19]. According to the same authors, activities related to plant health generate significant income allowing men to support their families, which is why they are more represented than women in this sector of activity.
The age group over 50 years was the most represented (Table 2). Indeed, older people are more likely to provide the most reliable information, as they hold much of the endogenous knowledge, which is part of oral traditions [20], [21]. In addition, knowledge about the virtues of plants is generally transmitted from father to son over generations [22]. But nowadays young people are increasingly disinterested in traditional knowledge, which could result in the disappearance of knowledge on plant use [23]. Several authors agree, showing that knowledge of the virtues and uses of plants is acquired with age through years of experience and passed on from one generation to another [24].
The Bamiléké represent 55.3% of the population surveyed (Table 2). The high representation of Bamilekes can be justified by the location of the study area, since the Western Highlands are populated in great majority by the Bamilekes. Moreover, this ethnic group strives to maintain and safeguard their culture and traditions with the help of traditional leaders whose authority is established and respected by all [19].
Among the species listed, the Lamiaceae was the most represented botanical family. This could be explained by the fact that the Lamiaceae includes most of the aromatic and condiment plants and species therefore are highly prized by the cosmetic industries. Indeed, Alliaceae, Apiaceae and Lamiaceae are the three main botanical families of aromatic plants [25]. By comparison, the study by Mpondo and collaborators carried out in the upper Nyong division shows rather a strong representation of Euphorbiaceae [23]. This is probably due to the fact that the agro-ecological zone of the studies differs and therefore the farmer's conception of plant use will also vary. In addition, the present work concerns aromatic and cosmetic plants while that of Mpondo and collaborators was based only on medicinal plants and in a single division.
The majority of the respondents appeared to use grasses for different purposes (Figure 2). The high use of grasses could be an indicator of their abundance in the study area. In addition, the herbaceous stratum is represented by small species that grow and regenerate rapidly and are therefore permanently available [26]. Mpondo Mpondo having obtained similar results had found during their raids on the study sites that the areas close to the dwellings were covered with grass, thus justifying the high use of it in traditional medicine by the different ethnic communities of Douala [27].
Leaves were the most commonly used organs (Figure 3). The frequent use of leaves can be justified not only by the fact that the organ is easy to harvest but also by the abundance of chemical compounds they contain. Indeed, they are the site of synthesis of several metabolites responsible for the biological properties of plants [28] [29] [30]. The plants listed were mainly used for therapeutic purposes (Figure 4), which could be in line with the popular belief that all plants are healing, provided that one knows how to use them. Moreover, the use of plants for medicinal purposes is a common and ancestral practice in Africa. Today, more than 80% of the African population do not have access to modern health care and medicines and therefore rely on traditional medicine for treatment [23].
The results show that traditional knowledge related to aromatic and cosmetic plants is mainly health-related (Table 4). And in particular for questions related to the mystical order. In fact, we counted 07 plants used for these purposes, namely Eryngium foetidum, Chenopodium ambrosioides, Ocimum gratissimum, Pipercapense, Cinnamomum zeylanicum, Aframomum melegueta and Cyperus rotundus. But of these, one in particular, Eryngium foetidum, is known by local people in almost all the study locations for its mystical-magical powers. Such knowledge is held only by the indigenous communities that hold the ancestral knowledge and cannot be exploited without their agreement and without
compensation because, as stipulated in Article 8 of the CBD, States must ensure that the traditional knowledge of the people is respected, preserved and promoted by all users of its resources.
5. Conclusion
This study highlighted the ethnic knowledge in the Western Highlands of Cameroon on the aromatics and/or cosmetic plants used by the population. A total of 103 species from 81 genera and 46 families were recorded in the area, having four (04) principal categories of uses, medicinal, food, cosmetic and cultural. These populations use several organs of these species, notably: leaves, barks, roots and fruits. Ten species: Eryngium foetidum,Chenopodium ambrosioides,Ocimum gratissimum,Piper umbellatum,Cinnamomum zeylanicum,Aframomum melegueta,Citrus limon,Costus afer,Cyperus rotundus and Mondia whitei are very well known and used by the populations. The knowledge held by the local populations is of great interest to the scientific community, to governments and even to industrialists who could see in these aromatic and cosmetic plants and their derivatives a means of further enrichment. Thus, at the end of this work, we can say that there are many plants in the West Cameroon Highlands that can be valorised according to the principle of access and benefit sharing.
Acknowledgements
The present study was carried under the SEP2D AAP1-55 project funded by the French Cooperation and the V.MANE FILS Enterprise.