Prices and sold amount dynamics , endogenous knowledge and distribution of Picralima nitida ( Stapf )

Picralima nitida (Apocynaceae) represents is an important African medicinal plant species. It is frequently used in traditional medicine and pharmaceutical industries for drugs manufacturing against infectious diseases, malaria and diabetes and commercially traded as well. Despite its importance, the species is becoming rare, especially in the Dahomey Gap because of it is commercial importance. There is an issue about the controversy of the plant species on its distribution across both regions. Without further forest resources inventory, it is difficult to address efficiently the issue of the controversy of its distribution, the unsustainable use and the endogenous knowledge about of plant species usages. Ethnobotanical surveys were conducted in the Dahomey Gap with 120 informants randomly selected and interviewed. A literature review of scientific papers and books was also used to provide information on the sale prices dynamic, amount sold per units, uses, distribution area Open Peer Review


Introduction
Picralima nitida is one of the most important medicinal plant species in the West and Central African folk medicine (Bickii et al., 2007;Odebiyi & Sofowora, 1978) as it. In West African folk medicine, P. nitida is widely used for the treatment of several diseases, such as febrifuge and cure for infectious disease (Akabassi et al., 2017), malaria (Betti et al., 2013), diabetes (Teugwa et al., 2013), and as a pain killer (Aguwa et al., 2001). In Central African folk medicine, the species is used in different ways. For instance, in Cameroon and Guinea, a decoction of the fruit and the bark is taken to treat coughs or typhoid fever (Adjanohoun et al., 1996). In the fangs Pahouin tribes in Gabon and Cameroon, the fruits and barks are chewed in small quantities to appease hunger during long walks in the bush (Bickii et al., 2007).
As a result of the above, the plant species are under threats at various levels management and based on data on the International Union Conservation for Nature (IUCN) Red List of Threatened plant species, there are no conservation initiatives in place for the rare P. nitida plant species, and it is considered as threatened. At the regional local level, available studies showed that the plant species are vulnerable because of the overexploitation of its organs that restricts its geographical area of distribution. For instance, in the typical Guinea-Congolese (GC) region (Nigeria), the species occurs freely in the wild without any forms of management practices and it is considered under threat of extinction (Gbadamosi, 2014). In the eastern region of Cameroon, P. nitida is considered as the first critically endangered plant species among the four species used by the indigenous populations for the typhoid fever treatment (Betti, 2004). Similarly, in the Dahomey Gap (DG) region (Benin), P. nitida is also considered as very rare and encountered at low density in many areas (Akabassi et al., 2018;Akabassi et al., 2020). At local level, Holaly et al. (2015) reported the presence and use of P. nitida in the treatment of diabetes in the traditional medicine of the Maritime region of Togo while knowledge about its economic value as well as its distribution is scant. Assogbadjo et al. (2011a) have shown that in the absence of a sustainable management approach, NTFPs with economic value for local populations are often threatened with genetic erosion. Trade in organs impacts the regeneration of plant species leading to their disappearance.
As far as its distribution is concerned, there is a controversy on the exact distribution areas of P. nitida. According to Adjanohoun et al. (1996), the distribution range of P. nitida extends from Côte d'Ivoire to Uganda including the Democratic Republic of Congo and Cabinda region in Angola. However, poor knowledge is available on the distribution of the plant species in Togo. The study of Eyog et al. (2006) reported that P. nitida is a tropical African species that is distributed in Ghana, Côte d'Ivoire, Nigeria, Angola, the Democratic Republic of Congo, Cameroon, and Tanzania. According to Omino (1996), the distribution area of P. nitida does not cover the DG. On the contrary, an early forest inventory study of Akpagana et al. (1994) on the news angiosperm species in the flora of Togo reported vealed that P. nitida is found in the ecological district IV of the country. Such controversy knowledge needs to be clarified if the proper distribution of the plant species has to be assessed for sustainable management approaches of the resource in DG regions (Benin and Togo).
Additionally, the lack of policy and regulations to guide the sustainable use and management of the threatened commercial medicinal plant species of P. nitida medicinal plant species may contribute to putting more pressure on the species in the wild. This paper aims at assessing the price dynamic economic value of P. nitida (Stapf) T. Durand and H. Durand, document the endogenous knowledge on the plant species, and sheds a light on the drivers of species scarcity, and its distribution in DG and GC regions through mix approaches.

Study areas
The study areas were in two regions, the Dahomey Gap (DG) and Guinea-Congolese (GC). The GC regions (Cameroon, Central African Republic, Congo Brazzaville, Côte d'Ivoire, Democratic Republic of Congo, Gabon, Ghana, Nigeria, and Uganda) are characterized by rainforests with a rainfall of up to 2500 mm. The average temperature of GC varies between 23 and 29°C with a relative humidity between 65 and 98%. In this region, the species is more distributed in natural vegetation without any forms of management practices (Gbadamosi, 2014). P. nitida species was more used in Cameroon, Congo Brazzaville, Côte d'Ivoire, Democratic Republic of Congo, Gabon, Ghana and Nigeria as medicinal plant. However, the study related to endogenous knowledge and economic value on the species were very limited (Adjanohoun et al., 1996).
On the contrary, the DG region (Benin and Togo) is characterized by savannas that extend down to the coast with a mosaic of rainforest ( Figure 1). There is also mangrove formations subject to tidal regimes. The DG is the dry zone that separates the two blocks of forest in tropical Africa (Bongers et al., 2004). The overall annual rainfall varies between 900-1400 mm. The average temperature of these two regions varies between 25 and 29°C with a relative humidity between 69% and 97%. In this region, P. nitida distribution is limited in home garden. It use is purely medicinal and no study has been carried out on the endogenous knowledge and economic value related to the species.

Economic value and endogenous knowledge of P. nitida in Africa
Sampling approach: Based on preliminary surveys conducted with 90 (45 per country) individuals that were randomly sampled and composed of various ethnic groups that use the plant species in the DG (Togo and Benin). I was found that 85% in Benin and 83% in Togo of respondents had knowledge knew at least one use for the species. This information was used to calculate the sample size according to the formula of Dagnelie (1998).
With n the size of the sample, p the proportion of peoples using the species (p = 0.275; from the preliminary survey), U 1-α/2 = 1.96 is the value of the normal random variable at a probability value of α= 0.05 and d is the margin error of the estimation of any parameter to be computed from the survey. A value of 8% was considered. Under these assumptions, 120 people were sampled during the main survey.  Figure 1 has been reproduced with permission of [Church, 1966].

Data collection
Individual interviews were conducted in Togo and Benin with a total of 120 (60 per country) key informants. The main local languages interviewed were Fon, Goun, Nago, Yorouba, Adja in Benin and Mina, Ewe, Kotafon in Togo. The survey has been piloted before its final implementation. In Benin, the survey covered two phytodistricts (Pobè and Vallée de l'Ouémé where the plant species are encountered (Akoègninou et al., 2006) and 30 informants were selected in each phytodistricts. In Togo, the survey covered Danyi located in ecological district IV (the only area where in of the plant species are encountered (Akpagana et al., 1994) and all the 60 informants were selected. The survey was performed between January and July 2018 and was conducted in the local language using a questionnaire (see Extended data) (Akabassi, 2020c;Akabassi, 2020d). The survey wascarried out through the households using a local guide. The local guide approached households in person and participants aged 18 and over were considered regardless of education level, ethnicity and gender.
The households were selected at random. However, households with sellers of medicinal plants were systematically selected instead of the households without such sellers. At total, 47 households with sellers and 39 without sellers were selected. After this Approach, a focus group discussion has been performed in each country to cross-check information gathered. The key aspects discussed during the focus group were the economic and socio-cultural values of the species, the uses and organs used, the frequency of use and main threats of the species. In Benin, 45 people indicated their willingness to participate in the focus group discussion while 42 people volunteered in Togo. Most informants were selected from localities with at least one P. nitida individual. These localities were Ifangni, Sakété, Adja-Wèrè, Ikpinlè, Kétou, Avrankou, Adjarra (in Benin) and Kouma, Danyi, Akposso-Akébou, Kpalimé-Atakpamé (in Togo). Data were collected on the economic and socio-cultural values of the species, the plant parts used, the usage frequency and the main threats of the species.

Literature search approach
In the typical GC region, data were collected through a literature search. The original articles obtained from various databases including Google Scholar (www.scholar.google.fr), ScienceDirect (www.sciencedirect.com), Scopus, PubMed Central, and African Journals Online (www.ajol.info) in addition to reports and thesis. Biodiversity databases (www.prota.org (and GBIF.org) were used to gather information on the importance of the species. The main research theme used were: "Economic value" AND "Picralima nitida"; "Endogenous knowledge" AND "Picralima nitida"; "Economic value" "Distribution" "Picralima nitida" "Togo" AND "Benin". A total of 21 published articles between 1996 and November 2018 were selected based on their importance for the topic. All articles not dealing with ethnobotanical importance and distribution of P. nitida were excluded. Letters, encyclopedia, case-reports, manuals, and guidelines were also excluded. The data that were extracted from selected articles were the socioeconomic importance, the different traditional uses of P. nitida organs, mode of preparation, dosage, and coordinates of study location.

Ethics and consent
Ethical approval was not sought for this study. The study is deemed by the researchers to be low risk, as it did not record any identifying information of participants; was not an interventionalor clinical-based study. However, consent has been received from community leaders and participants of the DG and ensured that the informed consent was received for data collection and analysis.

Data analysis
The importance of P. nitida for the surveyed populations was determined by the calculation of the use frequency of the plant properties (FUP).

FUP Rv Rah Raf
Ne is the total number of interviewees; Rv, Rah and Raf are the number of old, adult and young interviewees that used the property, respectively. A property was considered as 'credible' in case FUP is above 50% (Assogbadjo et al., 2011a;Camou-Guerrero et al., 2008).
The most used plant organ was identified through the computation of the index value related to useful organs (IVO).

100;
Nvo, the number of properties in the organ; Ne, the total number of identified properties.
Further, based on the literature review and the above analysis, absolute global credibility (AGC) for each use was calculated using the following formula: With N pu the distribution areas of the use X, N tp the total distribution area of the species. Usage is considered absolute if AGC ≥ 50%. The countries (Uganda and the Central African Republic) where no information was obtained on the use value of the species were not taken into account.
Basing on the collected data, the uses of the species were grouped into three fields of traditional application, namely: medicine, medico-magic and culture. A use was considered medicinal when results from the use of one part of the species associated or not with other plants or ingredients of an animal without any ritual, prayers or incantations. Use was considered as medicomagic when it associates the medicinal use with ritual, prayers or incantations. Use was considered cultural when practices during ritual ceremonies, funeral ceremonies, weddings, sacrificial rites and handicrafts.
Distribution and density of P. nitida. Data collection and analysis. In the DG, the samples of P. nitida were collected during the ethnobotanical survey carried out between January and July 2018 in both Benin and Togo to assess the density and the distribution of the species. The zones of the presence of the species in Benin (phytogeographical districts of "Pobè and Vallée de Ouémé") and Togo (ecological subdivision IV of Togo) were explored. The presence of P. nitida was obtained through a field exploration in collaboration with the local population largely the medicinal plant dealers to identify the presence of the species. The georeferenced coordinates were recorded for each sample of P. nitida identified. A total area of 4,590.52 km² was explored in Benin compared to 115.765 km² in Togo.
In the typical GC region, data on the species distribution were collected through the GBIF website. The species occurrence coordinates were gathered from the GBIF.org (16 May 2018) GBIF Occurrence Download https://doi.org/10.15468/dl.powalw and ArcGIS 10.2 (ESRI, Redlands, California, USA) were used to create a distribution map showing the current spatial distribution of the species. In this present study, the occurrence points of P. nitida were qualified of average when the number of occurrence points gathered did not reach two hundred. When it exceeds two hundred, it qualified as high.

Results and discussion
Economic value and endogenous knowledge of P. nitida in Africa Dynamics of selling price and amount sold per unit of P. nitida across both regions. The survey conducted in the DG revealed that the fruits of P. nitida are sold at variousforms and selling price tends to vary according to the selling form of the specie. Indeed, the largest fruit of P. nitida (about 1000 g) costs US$1 per unit, the average fruit size of (about 700 g) costs US$0.80. T and the smallest fruit size of (about 300 g) costs US$0.5. On the contrary, one seed cost US$ 0.05 and a kilogram of P. nitida seeds cost between US$6 and US$10.
In the GC region (Ghana), P. nitida seeds that were dried, powdered, encapsulated, and sold as "Picap capsules" cost between US$12.99 and US$225 depending on the quantity (see link 1 in the reference section). In Cameroon, seeds, bark, and fruit were sold (US$5 for 550 g of seeds or bark) in local markets (Betti, 2002;Betti, 2004). In Congo, 800 g of fruit cost about US$1 (see link 2 in the reference section). This indicated how the species can contribute to household income. Although, P nitida products were more expensive in the DG than the GC region, we noted the lack of price standardization across region. This lack of price standardization across region may be due to the various forms of sale of the same species. This constitute a difficulty of carrying out comparison studies across both regions.
P. nitida is very rare in this region and this probably justifies the high prices observed in the DG. The species was mainly found in home gardens and/or house yards in the DG. The domestication of non-timber forest species like P. nitida is an opportunity to alleviate poverty with positive benefits on the environment, since new plantations of P. nitida will contribute to reducing the greenhouse gas emission. It is therefore important to develop a management program for the sustainable use and trade of the species. This can offer more jobs and help in poverty alleviation in countries such as Cameroon where the species contributes to 12% of household income (Yakeu Djiam, 2012).

Various usages of P. nitida and loss of endogenous knowledge across both regions.
For medicinal purposes, the P. nitida plant species have various usages across both regions. In the DG, for example, 24 uses of the organs of P. nitida including roots, bark, leaves, and seeds were cited by the respondents ( Table 1). Out of that number, only seven uses were identified as credible (infectious diseases, angina, malaria, bellyaches, rituals, analgesic, and diabetes). The overall credibility of the uses was 75.94% in Benin and 70.94% in Togo implying that the use of the organs of the P. nitida is very important in the DG for healthcare. More importantly, the seeds were the most important organ used in the DG (79.16%) in Benin and (83.33%) in Togo). Consequently, the species is highly threatened since the removal of this organ causes the species death and this canlead to the extinction of wild populations of P. nitida, as already reported by Akabassi et al. (2017) and Assogbadjo et al. (2011b).
The credibility uses the value that was around 70.00% in both countries may imply that populations of the two countries have similar harvesting practices and utilizations of the specie for healthcare. For instance, Mina, Fon, and Ewe are the common ethnic groups that are encountered in both countries and they tend to share similar cultures and ancestral traditions native from the Tado kingdom in Dahomey (Kossi, 1990). The common practices observed may also be explained by the fact that the two countries neighboring countries that share the same borders and population of each country share common knowledge through ethnic groups cohabitation.
Focusing on the loss of endogenous knowledge and the drivers of species rarity, some factors have been highlighted. One of the key factors is related to harvesting practices that are based on the overuse of P. nitida organs. Adding to that abiotic factors such as climate and soil erosion could also explain the issue of resource scarcity.
All these factors have also contributed to weaken local knowledge about the species among local populations since fewer plant species means fewer usages as well. Overcoming such loss may call for developing the campaigns of information and  sensitization about the importance of conserving and sustainably using and managing P. nitida in both regions.
In the GC region, 24 uses of the organs of P. nitida (roots, bark, leaves, seeds, fruits, and wood), were cited (Table 2).
Only four uses were mentioned as credible (diabetes, malaria, fever, and sexual weakness). These results confirmed those of WHO (2011) which estimates that 90% of the recipes recorded in Africa are based on plants and 80% of local African populations depend on medicinal plants for their health care. Diabetes and malaria were the mains diseases that cause more mortality in Africa WHO (2011) and moreover, the recent study predicted that there will be some 438 million diabetic patients in 2030, most of them living in developing countries (WHO, 2011). Therefore the use of medicinal plants remain important to fight against this diseases.
The overall credibility of the plant uses in the GC region was 60.85%, indicating that P. nitida was important in this region. The seed was the most important organ used in the Guinea-Congolese region followed by the wood, fruit, leaves, bark, and root (Table 2). Based on the results of these Table 1 & Table 2, it can be argued that the species is highly used in both regions for healthcare purposes. Since the seeds constitute the regeneration organ of the plant species, the overuse of these organs can lead to genetic diversity and local knowledge loss.
In both regions, P. nitida was most frequently used against malaria, followed by measles, diabetes, worms, sexual weakness, hernia, fevers, infectious diseases, and diarrhea, as well as for shovel handles and spoons (Table 3). Shovel handles and spoons were a specific use in the GC region. Among these diseases, malaria is a principal cause of mortality and poverty in Africa (WHO, 2011). The use of the organs of P. nitida to treat these diseases will contribute to reducing mortality and poverty in Africa.
Knowledge of the species was significantly greater than in the GC region (Figure 2). This difference may be explained by the affinity of the population to the resource and its availability and or accessibility in the DG compared to GC.
The different uses of the species mentioned in this paper could help local communities to benefit from programs related to the promotion of the use of medicinal plant species for healthcare purposes oriented mainly around malaria as it is of the common diseases encountered in both regions.
Some uses were specific to certain regions with good credibility as the case of the use of the seeds to treat tonsillitis in the DG. Moreover, the fact that some uses were specific to each climate zone will be relevant when defining for each zone a valorization program of the species. These results are corroborate with those of Fakeye et al., 2000;Fakeye et al. (2004) who were showed the antimicrobial property of P. nitida stem bark extract in the pharmaceutical field.
In both climate zones (DG and GC regions), among the uses identified, 26 were of medicinal, three in medico-magic, and three cultural (Table 4). However, some specificities exist among each region as we will highlight in the section below. The medicomagic use was specifically reserve to the adult and old people. This difference of number of uses between these three fields of use  Shovel handles and spoons 55.55 Table 4. Medicinal, medico-magic and cultural practices of P. nitida organs.

Cultural practices
Malaria -Angina -Diabetes-Analgesic -Against abortion Diarrhea -Hemorrhoid -Measles -Fevers -Cough -Bellyaches -Infectious diseases Infertility -Painful period-Cancer -Disinfection -Tension-Toothache -Sexual weakness-Hernia -Jaundice -Vomiting Inhumation rituals -Good luck -Paralysis Weaning -Wedding rutual-Utensils -Initiation Rites in couvents of "Egoungoun and Oro" (traditional religions) may be due to the fact that in Africa, certain knowledge, especially spiritual or magical, remains the property of the initiates and the elderly. This knowledge is difficult bequeathed to young people who do not yet have a high wisdom degree. The use of medicinal plants in the medico-magic field in black Africa is characterized by a set of local beliefs, strongly anchored in the founding myths of local communities and giving an important place to spirits, incantations and ancestors. These magicoreligious beliefs are most often reserved for initiates and the elderly with a high wisdom degree because the results deriving from incantatory words are often irreversible.
In the DG, each of the above-mentioned uses as of use by local populations, whereas in the GC region, P. nitida was not considered for medico-magic use. The cultural differences and specific local population needs between the two climates zones may also explain this variation in use (Dadjo et al., 2012).
In both climate zones (DG and GC regions), among the uses identified, 26 were of medicinal, three in medico-magic and three cultural (Table 4).

Distribution and density of P. nitida across both regions Distribution and density of P. nitida in the DG region.
During the investigation in Togo, P. nitida was found in the southwest of the country, 185 km from Lomé at 800 m altitudes in the "Danyi Dzogbégan" region at the monastery "Abbaye d'ascension". This region is situated in ecological district IV, corresponding to dense semi-deciduous forests. P. nitida was not found in natural vegetation. The distribution map of the species elaborated by Adjanohoun et al. (1996) did not include Togo. This may be due to the lack of available information on the species in 1996 or the absence of the species in natural habitats. Moreover, the great number of individuals of the species observed in the monastery may be introduced after 1996.
In Benin, P. nitida was found in the forest in the phytogeographic zones of "Pobè and Vallée de l'Ouémé" located in the southeast of the country and characterized by the GC climate conditions. The occurrence of the species decreases either in latitude from the south or in longitude from the southeast. Besides, P. nitida was found in home gardens and home yards in the DG. However, the species is almost absent in the dry forests of the DG (Figure 4).
The DG is not a suitable habitat for the species because of the dry climate in this region. The occurrence of the species in this region may be the results of the long domestication process due to the importance of the species to the local populations. This may explain why some authors (Eyog et al., 2006;Omino, 1996) do not consider the DG to be a distribution area of P. nitida.

Distribution of P. nitida in Guinea-Congolese region.
In all the countries of the Guinea-Congolese region (Cameroon, Central African Republic, Congo Brazzaville, Côte d'Ivoire, Democratic Republic of Congo, Gabon, Ghana, Nigeria, and Uganda), P. nitida was found in the forests. In Cameroon, P. nitida occurred in forests (52%) and farms (30%) (Yakeu Djiam, 2012). The occurrence point of P. nitida can be qualified in two ways (Figure 3). In Upper Guinea (from Guinea and Sierra Leone to Ghana" Western Region"), the occurrence of P. nitida was average. In Lower Guinea (Nigeria and eastward; "West Central Region"), P. nitida had many occurrences that may be justified by the highest rainfall observed in this area, especially in western Cameroon, which experiences 3,000 mm of precipitation per year (Lefèvre, 1967).
Individual-level responses to the ethnobotanical survey and geographical distribution locations are available as Underlying data (Akabassi, 2020a; Akabassi, 2020b).

Local population perception on the drivers of the scarcity of the P. nitida species across both regions.
The mains factors that contributed to the scarcity of the P. nitida species were the overuse, climate change, deforestation and endogenous knowledge loss. The overuse was the main driver of scarcity of the P. nitida species in the DG followed by climate change and endogenous knowledge loss. In the GC region, the main drivers of scarcity of the P. nitida species were deforestation, overuse and climate changes ( Figure 4). Overexploitation, deforestation and changing climatic conditions contribute to the loss of indigenous plants and hence endanger traditional and biodiversity dependent community medicines. This result corroborated with those of Shanley & Luz (2003) who showed that forest degradation has diminished the availability of some widely used medicinal plant species and many of these medicinal plants have no botanical substitute, and pharmaceuticals do not yet exist for some of the diseases for which they are used.

Conclusion
The organs of P. nitida (seed, bark, and fruit) are sold in the DG and GC region at various forms and prices. This stresses out the issue of lack of standardization methods to estimate efficiently the economic value of NTFP as well as the difficulty of cross-region comparison. The species has a total of 24 uses in medicine, medico-magic, and culture in the Dahomey gap and GC region with more credible uses and knowledge in the DG. P. nitida is rarer in the DG than in the GC region. The overuse, endogenous knowledge loss and deforestation appeared the main driver of scarcity of the species in both climatic zones. The Seeds was the most important organ used around the study area. The Adapted management strategies are needed for the sustainable use and conservation of the species in the two climatic zones.

Recommendations
To ensure sustainability of the species, it is necessary to: -carry out forest inventory and resource capacity in both regions in order to know the exact distribution areas and preference ecology of the species; -set up a domestication program for sustainable use and management of the species; -assess the effect of climate and habitat on morphological characteristics and fruit production of Picralima nitida in order to know the mains causes of the scarcity of the species in Dahomey Gap; -evaluate the natural seed germination and seedling growth of Picralima nitida.

Data availability
Underlying data This study contains the following underlying data: Additional information has been added to the annotated manuscript itself (available here). Please have a look for further assessment.

Material and methods:
Some remarks have been directly added into the annotated manuscript itself (available here). Please have a look and respond accordingly.

Results (The missing key results):
These two results need to be added in the paper to tackle the issue at stake in this paper: About the drivers of local/ endogenous knowledge loss across both regions; and 1.
About the drivers of the scarcity of the resource across both regions. 2.

Discussion:
The importance of endogenous knowledge on plants used to treat various diseases across both regions, 1.
The factors causing the erosion/loss of local knowledge; 2.
The factors affecting the current distribution of the plant species across both regions, and 3.
The opportunity to overturn the issue of endogenous knowledge's loss and approaches to slow down the loss of the scarce plant species while ensuring it sustainable management across both regions.

4.
Additional information has been added to the annotated manuscript itself (available here). Please have a look for further assessment.

Conclusion:
In this section, please assess whether the paper has contributed to answer to the following aspects of your research paper (the specific objectives of the paper): The price and selling amounts dynamics of P. nitida (Stapf) T. Durand and H. Durand across both regions; ○ Documenting the various uses of the plant species and the drivers of loss of local/endogenous knowledge about usages of that plant species across both regions; ○ Shed a light on the drivers of species scarcity, and its distribution across both regions.

Recommendations:
As key recommendations, the authors should suggest some solutions to safeguard the loss of local/endogenous knowledge and approaches for sustainable management of the plant species around across both regions.

Competing Interests:
No competing interests were disclosed.
I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above.
Reviewer Report 27 October 2020 https://doi.org/10.21956/aasopenres.14183.r27676 © 2020 Yobo C. This is an open access peer review report distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Christian Mikolo Yobo
Département d'Ecosystèmes Terrestres, Institut de Recherche en Ecologie Tropicale du Centre National de Recherche Scientifique et Technologiques (IRET/CENAREST), Libreville, Gabon The paper deals with the importance of Picralima nitida (Stapf) T. Durand and H. Durand, known as an important African medicinal plant species in Dahomey Gap region in general and in Togo in particular, especially at the glance of its: i) economic value, ii) endogenous knowledge and distribution. However, the paper failed to take into consideration several aspects such as i) poor knowledge about the exact distribution of the Picralima nitida plant species, ii) the issue of erosion of local knowledge and the need for its safeguard; iii) the causes of plant species (Picralima nitida) rarity, and iv) any available initiatives/interventions that have been carried out to address the issue along with any available policy and available regulations in place to guide sustainable management of biodiversity in general and Picralima nitida medicinal plant species in particular. Undermining such background knowledge has contributed to lowering the quality and strength of the paper. As a result, in its current stage, the paper could not be accepted for indexing, unless important ameliorations are made.
Please see my detailed comments in the PDF file found here.

If applicable, is the statistical analysis and its interpretation appropriate? Not applicable
Are all the source data underlying the results available to ensure full reproducibility? Partly

Are the conclusions drawn adequately supported by the results? No
Competing Interests: No competing interests were disclosed.
Reviewer Expertise: NTFP Socioeconomics, Livelihood assessment, Ethnobotany, NTFP value chains assessment, NTFP resource management, and policy and regulation assessment

I confirm that I have read this submission and believe that I have an appropriate level of
Introduction R: I would rather suggest that the authors focus on the background of his paper as follows: In Dahomey Gap's region or West African region, they should point out the following… A: This recommendation has been taken into account in the indicated part of the manuscript.
R: I think that this general objective does not capture the full content of the paper as a result I suggest the following one "This paper aims at assessing the economic value, document the endogenous knowledge on the plant species, and sheds a light on the distribution of Picralima nitida ( ScienceDirect (www.sciencedirect.com), Scopus, PubMed Central and African Journals Online (www.ajol.info) in addition to reports and thesis. Biodiversity databases ( www.prota.org and GBIF.org) were used to gather information on the importance and occurrence coordinates of the species. The main research theme used were: "Economic value" AND "Picralima nitida"; "Endogenous knowledge" AND "Picralima nitida"; "Distribution" AND "Picralima nitida"; "Togo" AND "Picralima nitida"; "Benin" AND "Picralima nitida". A total of 66 published articles were obtained and 31 published articles between 1996 and November 2018 were selected based on their relevant for the topic. All articles not dealing with ethnobotanical importance and distribution of P. nitida were excluded. Letters, encyclopaedia, case-reports, manuals and guidelines were also excluded. The data that were extracted from selected articles were the socio-economic importance, the different traditional uses of P. nitida organs, mode of preparation, dosage and coordinates of study location.

Introduction:
Remove: It is a small tree which reaches 4-35 m in height. Its wood is pale yellow, hard, elastic and fine-grained with a high polish. P. nitida bears white flowers (about 3 cm long) with yellowish ovoid fruits at maturity. The leaves are broad and oblong with tough tiny lateral nerves of 14-24 pairs. This section is out-of-place.
○ "In addition to its medicinal uses, P. nitida provides an income to millions of households in Africa." How so? Explain via an additional sentence.
○ "The species is known as a febrifuge and a cure for infectious disease, malaria, diabetes and pain (Aguwa et al., 2001;Akabassi et al., 2017;Betti et al., 2013;Teugwa et al., 2013)". -The issue of string citation (listing multiple authors at end of sentence) is a pervasive problem in this manuscript. By placing multiple consulted sources at the end of a sentence implies all information in that sentence can be attributed to those authors -thus per implication they (authors) stated exactly the same information -in which case why cite more than one, when the most authoritative would suffice? This issue must be corrected by placing sources immediately after used fact inside the sentence, when dealing with multiple authors in a sentence, so as to explicitly attribute a specific fact to a specific source. Correct throughout the manuscript. ○ Figure 1: does not show the full distribution range of the species, especially in southern Africa.
○ "There is a need to dispel the ambiguity over the distribution areas of this species and to document the important threats to its conservation." Where is the threat analysis and discussion?

Materials and Methods
Study area: "The study areas were typical GC regions (Cameroon, Central African Republic, Congo Brazzaville, Côte d'Ivoire, Democratic Republic of Congo, Gabon, Ghana, Nigeria and Uganda" -incorrect. The study area was confined to DG countries, Togo and Beninrephrase. ○ Figure 2: "…characterized by rainforests with a rainfall of up to 2500 mm, and the DG region (Benin and Togo) characterized by savannas that extend down to the coast with a mosaic of rainforest ( Figure 2)." Figure 2 does not show mosaic of rainforests or savannas.

Results/Discussion
○ Economic value: "P. nitida seeds were dried, powdered, encapsulated and sold as "Picap capsules" that cost between US$12.99 and US$225 depending on the quantity…" -For which region/country is this? How old is this information? How scientifically correct is the information that is derived from a non-peer-reviewed web-based source. ○ (https://thegradekratom.com/product/akuamma-seeds/). -web addresses not to be included in text -relocate to reference section. ○ "P. nitida products were more expensive in the DG." -more than?
○ "The domestication of non-timber forest species like P. nitida is an opportunity to alleviate poverty with positive benefits on the environment, since new plantations of P. nitida will contribute to reduce the greenhouse gas emission."-this is such a general statement as to apply to any plant species -relook. ○ "It is therefore important to develop a management program for the sustainable use of the species." On the contrary, no information has been provided to indicate unsustainable use or harvesting. So why is a management program necessary? Because it is rare? But could be due to abiotic factors such as climate and soil, not necessary due to adverse anthropogenic actions. Relook.

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Endogenous knowledge: Bark -is this stem bark or root bark? ○ Bellyaches -replace with stomach aches.
○ "This indicated that P. nitida is very important in the the DG." -this is a prime example of some of the many unprofessional editorial issues abound in this paper.
○ Table 1 and Table 2: Why are leaves presented in plural, but other organs in singular? ○ Table 1 and Table 2: Indicate if the fruit is mature and ripe, or not.
○ Table 1 and Table 2: Stem -does this include wood+bark?
○ "The seed was the most important organ used in the DG (79.16% in Benin and 83.33% in Togo)." Why and what would be the conservation impact/population sustainability impact? Discussion needed.
○ "The seed was the most important organ used in the Guineo-Congolese region followed by the wood, fruit, leaves, bark and root (Table 2)." -Why and what would be the conservation impact/population sustainability impact? Discussion needed.
○ "In the DG and GC regions, P. nitida was most frequently used against malaria, followed by measles, diabetes, worms, sexual weakness, hernia, fevers, infectious diseases and diarrhoea, …" Are there any biochemical/microbiology papers found that scientifically validate these claims? Discussion needed.
○ "… uses were specific to certain regions with good credibility as the case of the use of the seeds to treat tonsillitis in the DG." Is there any biochemical/microbiology papers found that scientifically validate these claims? Discussion needed.
○ "The different uses of the species mentioned in this paper could help local communities to benefit from the medicinal values of the species." -how so? Statement not clarified. Explanation needed.
○ Effect of climate gradient on density and distribution: P. nitida was found at very low density in the DG (0.020 ind./km2 and 1.75 ind./village in Togo and 0.022ind./km2 and 1.87 ind./village in Benin). Is this information coming from literature (not cited). If not, then how was this determined? Individuals per village are meaningless -we do not know how large the village is. Density must only be expressed as individuals per km 2 .
○ Distribution of P. nitida in Guineo-Congolese region: "In the Upper Guinea (from Guinea and Sierra Leone to Ghana" Western Region"), the occurrence of P. nitida was average. What constitutes average? Occurrence categories not presented in Materials and Methods section.

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In Lower Guinea (Nigeria and eastward; "West Central Region"), P. nitida had many occurrences …"-What constitutes many occurrences? Occurrence categories not presented in Materials and Methods section.