Medicinal Plants for Dermatological Diseases: Ethnopharmacological Signiﬁcance of Botanicals from West Africa in Skin Care

: Skin disease is a severe health issue that affects a lot of people in Africa and is vastly underreported. Because of their availability, affordability, and safety, medicinal plants represent a major source of treatment for various skin diseases in West Africa. This review presents the medicinal plants used in treating skin diseases in West Africa and their available biological activities that have lent credence to their skin care usage. A total of 211 plant species from 56 families are implicated to be used in West Africa for several skin conditions such as aphthous ulcers, burns, eczema, scabies, sores, and wounds. Fabaceae is the most-implicated family (30 species) for the treatment of skin diseases, followed by Combretaceae (14 species) and Asteraceae (13 species). Most of the medicinal plants used are trees (93); leaves (107) were the most-used plant part, and decoction (73) was the preferred preparation method for the medicinal plants. The biological activities related to the pathology of skin diseases, such as antimicrobial and anti-inﬂammatory properties of 82 plants, have been evaluated. Based on their minimum inhibitory concentration, the most active antimicrobial plant is Brillantaisia lamium . Among the isolated phytochemicals, betulenic acid and lespedin were the most active, while plants such as Kigelia africana and Strophanthus hispidus showed signiﬁcant wound-healing activities. This review highlights research gaps in the ethnobotanical studies of many West African countries, the biological activities of plants used to treat skin diseases, and the cosmetic potential of these plants.


Introduction
The human body's largest and most vulnerable organ is the skin.It serves as a barrier and shield between the internal organs and direct microbial contamination and ultraviolet radiation [1].It contains three layers: the epidermis, dermis, and subcutaneous.The epidermis, the outermost layer, protects the skin against infections caused by some microbes [2].The dermis comprises follicles and glands and is essential for regulating body temperature, while the subcutaneous layer contains a network of connective tissues and fat [2].Despite the dry and infertile nature of the skin, it is still home to millions of microbes, some of which are essential in preventing skin invasion by pathogens [3].The nature of the skin significantly influences the type and abundance of microbes present, causing skin diseases or infections.For example, Corynebacterium and Staphylococcus species are abundant in the moist areas of the skin, while sebaceous areas are predominantly occupied by Propionibacterium species [4].Also, different skin or systemic diseases may arise from broken skin or an imbalance between beneficial microbes and pathogens [5].
Skin disease is the fourth most common cause of illnesses in humans [6].However, this may be inaccurate because reports have shown that a large percentage of people suffering 2 of 46 from different skin conditions do not consult dermatologists [7].Medicinal plants have long played a significant role in treating a wide range of illnesses, including skin diseases, which are not always reported but are self-treated [8].In the last few decades, extensive efforts have focused on documenting medicinal plants to identify species that may be used in drug development [9].Among these, some studies have reported or reviewed the plants used to treat skin diseases around the globe.For example, there is documentation of medicinal plants used for skin diseases in southern Africa, Pakistan, the south Balkan, and the eastern Mediterranean regions [10][11][12].Many people in West Africa rely on traditional medicine/medicinal plants due to their accessibility and believe they are more potent and efficient in curing disease than conventional medicines or healthcare, which is inadequate in the region [13,14].Also, many skin diseases tend to be so persistent and recurring that patients resort to many remedies, including herbal ones [1].Therefore, quite a number of studies have aimed at documenting plants used to treat skin diseases in different West African countries.For example, the Akwa Ibom state of Nigeria [15], the northern region of the Republic of Benin [16], the northwest region of Cameroon [17], and many others.
Moreover, to validate the traditional uses of some of the documented plants, some other studies have tested the extracts from the plants for pharmacological activities related to skin diseases, such as antioxidant, anti-inflammatory, and antimicrobial activities, to prove their efficacy.For example, Rosamah et al. [1] investigated the pharmacological significance of Macaranga in dermatological diseases; Udegbunam et al. [18] confirmed the therapeutic activity of Crinum jagus in wound healing; and Anacardium occidentale extracts were tested on pathogenic microbes to verify its usefulness in skin care cosmetics by Gonçalves and Gobbo [19].There are also many similar studies, but this information is scattered in the literature, which may account for the fact that none of the many cosmetic plants recognized by the European Pharmacopoeia are of West African origin [20].This also underscores the significance of studies in this field.Therefore, this review aims to appraise all available information on the use of plants for treating skin diseases in West Africa to highlight research gaps and give a proper direction to future research on the dermatological significance of medicinal plants from West Africa.

Methodology
A comprehensive search of major journal websites and academic databases, such as African Journal Online, Google Scholar, ScienceDirect, Scopus, and Web of Science, was conducted.This aimed to retrieve all published ethnobotanical studies in the West African region up until September 2023.The keywords used in the search include the names of West African countries, ethnobotany, medicinal plants, indigenous plants, skin diseases, skin ailments, cosmetics, wounds, and West Africa.From the papers retrieved, plants used for skin diseases were extracted from the general ethnobotany.Plant names and their family were verified and updated using databases, namely: Tropicos (www.tropicos.org;accessed on 7 October 2023), World Flora Online (https://www.worldfloraonline.org/;accessed on 29 November 2023), and WFO Plant List website (https://wfoplantlist.org/plant-list; accessed on 7 October 2023).The selection of articles for this review was made on the basis of the following criteria: It is published in English or translated to English.

2.
At least one plant is listed for the treatment of skin diseases.

3.
It studied the bioactivity of at least one of the plants in the list of plants documented.4.
If the ethnopharmacological study is carried out outside West Africa but examines the bioactivity of any documented plants used to treat skin diseases in the region.
Figure 1 shows the PRISMA flowchart for the inclusion and exclusion procedure.4. If the ethnopharmacological study is carried out outside West Africa but examines the bioactivity of any documented plants used to treat skin diseases in the region.
Figure 1 shows the PRISMA flowchart for the inclusion and exclusion procedure.

Diversity of the Medicinal Plants Used for Skin Diseases in West Africa
The western part of Africa is a tropical region with high annual rainfall and temperature.Hence, it is known to have a wide flora diversity.A total of 211 taxa are reported in this review as used in the treatment of various skin diseases or infections in the western part of Africa (Table 1).In comparison, 100 plant species were reportedly used for skin diseases in southern Africa [10], 545 species in Pakistan [11], and 967 in the South Balkan and East Mediterranean region [12].Over 90% of the plants were reported from Nigeria, the Republic of Benin, Togo, Ghana, Cameroon, and the Ivory Coast, implying a large research gap in the ethnobotanical studies of many West African countries.The reported taxa belong to 56 different families.Among these, plants of the Fabaceae family were overwhelmingly preferred for combating skin diseases in West Africa, as 30 species

Diversity of the Medicinal Plants Used for Skin Diseases in West Africa
The western part of Africa is a tropical region with high annual rainfall and temperature.Hence, it is known to have a wide flora diversity.A total of 211 taxa are reported in this review as used in the treatment of various skin diseases or infections in the western part of Africa (Table 1).In comparison, 100 plant species were reportedly used for skin diseases in southern Africa [10], 545 species in Pakistan [11], and 967 in the South Balkan and East Mediterranean region [12].Over 90% of the plants were reported from Nigeria, the Republic of Benin, Togo, Ghana, Cameroon, and the Ivory Coast, implying a large research gap in the ethnobotanical studies of many West African countries.The reported taxa belong to 56 different families.Among these, plants of the Fabaceae family were overwhelmingly preferred for combating skin diseases in West Africa, as 30 species from 23 genera represent them.This is followed by the family Combretaceae, with 14 species, half of which are from the genus Combretum.Asteraceae and Euphorbiaceae are also well represented, with 13 and 12 species, respectively (Figure 2).Overall, nine families-Fabaceae (30), Combretaceae (14), Asteraceae (13), Euphorbiaceae (12), Phyllanthaceae (8), Rubiaceae (8), Moraceae (8), Malvaceae (7), and Apocynaceae (7)-represented over 50% of the recorded plant species, while 22 species, were the only members of their respective families.The legume family (Fabaceae) is one of the most influential families of angiosperms in terms of medicinal uses across communities and regions worldwide [21].Despite being the third largest family, its wide distribution worldwide could be a major reason for its widespread usage in traditional medicine [21].The sustained use of the species of the Fabaceae family over time may also indicate their biological activities, and the phytochemistry of many species in this family has supported this hypothesis, showing that they contain critical active metabolites [22].The biological activities and chemistry of the family Combretaceae have also revealed a wide range of useful phytochemicals [23].However, other genera apart from the genera Combretum and Terminalia are rarely explored [24].Asteraceae is the largest plant family and has always been highly represented in many ethnobotanical studies, and the family members are known to contain phytochemicals of medicinal importance [25].

Life Forms, Plant Parts Used, Mode of Preparation, and Conservation Statuses of the Plants
Over 60% of the plants implicated in this paper are woody species, comprising trees (93, 44%) and shrubs (40, 19%) (Figure 3).Other life forms are herbs (61, 29%) and climbers (17, 8%).Some studies have reported that herbs are the most-used medicinal plants due to their ease of harvesting [60,61].Though this may be true for some individual studies, a holistic review of the ethnobotany of an area or an ailment category has revealed, in most cases, the prevalence of trees in traditional medicine [62,63].Additionally, West Africa, being a tropical area, could be responsible for the abundance of trees in the region.
Regarding the plant parts or organs used in formulating or preparing various herbal medicines, leaves were more frequently used (107) than any other plant.Roots (55) and stems (39) were next, while all other plant parts had less than 20 use reports(Figure 4).The use of leaves in herbal remedies has always been highly reported, and the literature suggests it may be due to their ease of harvest [64].It is also possible that leaves are especially well used for skin diseases because other reports on skin diseases [10,11] documented similar findings.However, the relatively high frequency of roots after the leaves could be related to the high prevalence of woody species implicated in this study.Also, the roots of plants are believed to contain a high quantity of phytochemicals because of their role in the absorption of nutrients [64].Regrettably, harvesting medicinal plants' roots for medicinal purposes poses the greatest conservation risk to plants because they are difficult to regenerate.Considering the mode of preparation, decoction (73) was the most preferred method, followed by crushing/juicing (50), and powdering, grinding, or pounding (39) (Figure 5).The decoction method has been reported as the most common method of preparation of medicinal plants around the world [17].However, there is no clear scientific reason why the method is widely used.The use of the method of crushing or juicing in this review may be attributed to the nature of the disease, as it is the easiest and quickest method to apply the extracts from the plant topically to the skin.Figure 6 shows the number of plants used to treat different skin diseases; wounds, being the

Life Forms, Plant Parts Used, Mode of Preparation, and Conservation Statuses of the Plants
Over 60% of the plants implicated in this paper are woody species, comprising trees (93, 44%) and shrubs (40, 19%) (Figure 3).Other life forms are herbs (61, 29%) and climbers (17, 8%).Some studies have reported that herbs are the most-used medicinal plants due to their ease of harvesting [60,61].Though this may be true for some individual studies, a holistic review of the ethnobotany of an area or an ailment category has revealed, in most cases, the prevalence of trees in traditional medicine [62,63].Additionally, West Africa, being a tropical area, could be responsible for the abundance of trees in the region.The dried powder of the seed is applied topically.Wounds [16] two plants (Aframomum melegueta and Mangifera indica) have a conservation status of data deficient (DD).It was observed in this paper that most of the plants with no conservation assessments are herbs and climbers, implying that most conservation efforts have been centered on tree species.This highlights the need to intensify conservation studies on herbs and climbers that are used medicinally as they are also prone to extinction, like trees [65].Regarding the plant parts or organs used in formulating or preparing various herbal medicines, leaves were more frequently used (107) than any other plant.Roots (55) and stems (39) were next, while all other plant parts had less than 20 use reports (Figure 4).The use of leaves in herbal remedies has always been highly reported, and the literature suggests it may be due to their ease of harvest [64].It is also possible that leaves are especially well used for skin diseases because other reports on skin diseases [10,11] documented similar findings.However, the relatively high frequency of roots after the leaves could be related to the high prevalence of woody species implicated in this study.Also, the roots of plants are believed to contain a high quantity of phytochemicals because of their role in the absorption of nutrients [64].Regrettably, harvesting medicinal plants' roots for medicinal purposes poses the greatest conservation risk to plants because they are difficult to regenerate.Considering the mode of preparation, decoction (73) was the most preferred method, followed by crushing/juicing (50), and powdering, grinding, or pounding (39) (Figure 5).The decoction method has been reported as the most common method of preparation of medicinal plants around the world [17].However, there is no clear scientific reason why the method is widely used.The use of the method of crushing or juicing in this review may be attributed to the nature of the disease, as it is the easiest and quickest method to apply the extracts from the plant topically to the skin.Figure 6 shows the number of plants used to treat different skin diseases; wounds, being the highest, are treated with 65 plants.Skin ulcers are treated with 46 plants and skin spots with 58.The pain associated with wounds and ulcers may account for the observed figures.As for skin spots, it is general knowledge that many people love spotless skin.
An assessment of the recorded plants' conservation statuses revealed a lack of conservation status data for 43% of the recorded plants.Among the plants with conservation records, 113 have a conservation status of least concern (LC).Six plants (Afrofittonia silvestris, Afzelia africana, Allanblackia floribunda, Gossypium hirsutum, Khaya grandifoliola, and Vitellaria paradoxa) have a conservation status of vulnerable (VU), while two plants (Aframomum melegueta and Mangifera indica) have a conservation status of data deficient (DD).It was observed in this paper that most of the plants with no conservation assessments are herbs and climbers, implying that most conservation efforts have been centered on tree species.This highlights the need to intensify conservation studies on herbs and climbers that are used medicinally as they are also prone to extinction, like trees [65].

Biological Activities of the Recorded Plants
Millions of beneficial microorganisms and pathogens inhabit the skin surface, and their imbalance or breaking of the skin could cause skin diseases [3,5].Skin diseases recorded in this review and treated with medicinal plants include abscesses, athlete's foot, boils, measles, skin spots, as well as ulcers, whitlows, wounds, and many other skin infections.Due to the diversity and nature of these diseases, medicinal plants employed in treating skin disorders should possess pharmacological properties such as antibacterial,

Biological Activities of the Recorded Plants
Millions of beneficial microorganisms and pathogens inhabit the skin surface, and their imbalance or breaking of the skin could cause skin diseases [3,5].Skin diseases recorded in this review and treated with medicinal plants include abscesses, athlete's foot, boils, measles, skin spots, as well as ulcers, whitlows, wounds, and many other skin infections.Due to the diversity and nature of these diseases, medicinal plants employed in treating skin disorders should possess pharmacological properties such as antibacterial,

Biological Activities of the Recorded Plants
Millions of beneficial microorganisms and pathogens inhabit the skin surface, and their imbalance or breaking of the skin could cause skin diseases [3,5].Skin diseases recorded in this review and treated with medicinal plants include abscesses, athlete's foot, boils, measles, skin spots, as well as ulcers, whitlows, wounds, and many other skin infections.Due to the diversity and nature of these diseases, medicinal plants employed in treating skin disorders should possess pharmacological properties such as antibacterial, antifungal, antioxidant, anti-inflammatory, and wound-healing activities.Still, the review revealed that a large percentage of the studies have focused on the antibacterial and antifungal studies of the plants used in the treatment of skin diseases.In contrast, only a few studies explored other biological activities.However, it should be noted that researchers have addressed, to a large extent, the recommendations from a previous study [10] by studying the response of some neglected bacteria to botanicals used in skin diseases.Out of the 211 plant species recorded in this review, the biological activities of 82 plants have been assessed (Table 2), while over 60% of the plants are yet to be evaluated for any activities related to skin diseases, highlighting the wide gap in research into the biological activities of traditionally used medicinal plants.
Most of the studies in this review examined the antibacterial and antifungal activities of the plants using different types of dermatophytes.Some of the most commonly chosen skin pathogens include the bacteria Staphylococcus aureus, Epidermophyton floccossum, Bacillus subtilis, and Pseudomonas aeruginosa, while species of fungi in the genus Candida, especially C. albicans, were the most commonly tested fungi.Biological activities are a means of validating the efficacy of the traditional uses of plants.However, some of the activities recorded in Table 2 may not necessarily validate the use of the plants against skin diseases because the plant parts reportedly used in traditional medicine are different from those tested, and it is common knowledge that the type and quantity of the phytochemicals accumulated by different plant parts may be widely different.For example, the leaf juice of Achyranthes aspera is folklorically used to treat skin ulcers [15], but Gupta et al. [70] evaluated the antimicrobial activities of its root and stem.Likewise, the antimicrobial activities of the stem bark of Lannea acida were evaluated [133], but ethnobotanical records showed the use of its leaves in skin diseases [15,25].Some of the most active antibacterial and antifungal plants based on their low MIC include the aerial part of Brillantaisia lamium (6.25 µg/mL), the essential oil of the seeds of Monodora myristica (8 µg/mL), the leaves of Flueggea virosa (8 µg/mL), the leaves of Dacryodes edulis (12.5 µg/mL), the essential oil from the aerial parts of Ageratum conyzoides (64 µg/mL), the aerial parts of Clerodendrum splendens (64 µg/mL), and the leaves of Pistia stratiotes (125 µg/mL).As regards the range of microorganisms susceptible to the extracts, alcohol extracts of Aloe vera leaf gel inhibited 115 skin pathogens [81].Conversely, some plants were completely inactive, while others had very high MICs, thus making them inactive.For example, the aqueous extract from leaves of Lannea microcarpa was not active in all the skin pathogens tested [134], while the leaves of Sansevieria liberica and the roots of Hannoa undulata had a MIC value of 62.5 mg/mL each [127,151].Some of these studies have confirmed or validated the ethnobotanical use of the plants, while others did not support their use.This may be due to the solvent extract used for the biological activities.It is also common practice to prepare herbal remedies using more than one plant for a single ailment for synergistic purposes or to treat the disease and symptoms [64].Therefore, it is important to test the biological activities of medicinal plants following the traditional method of preparation and administration.The extract inhibited pathogenic fungi, namely, C. albicans, M. luteus, M. roseus, P. aeruginosa, and S. aureus, with zones of inhibitions between 12-18 mm.
Carbohydrates, alkaloids, [ The extract displayed significant activities against different strains of multi-drug resistant S. aureus.
Alkaloids, flavonoids, phenol, tannins and terpenoids [159] Vitellaria paradoxa Nuts, leaf, stem and root Antimicrobial/Ethanol Extracts showed activity against pathogens with zones of inhibition between 11 and 30 mm and MIC values between 60 and 70 mg/mL.Alkaloids, carbohydrates, saponins, steroids, and tannins [160,161] Xanthosoma sagittifolium Leaf, stalk, and root Antifungal/Ethanol The extract inhibited the pathogenic fungi, T. rubrum, with an inhibition diameter of 18 mm, close to the standard drug, amphotericin (20 mm).
Cardiac glycoside, flavonoids, tannins, phenols, and terpenoids [162,163] Xylopia aethiopica Fruit Antimicrobial/Aqueous.methanol and essential oil The extract was active against the pathogenic fungi, namely Microsporum canis, M. equinum, and T. mentagrophyte with inhibition zones of 2.84 to 3.5 mm.The oil extract also showed significant activity against B. subtilis, Enterobacter aerogenes, E. coli, S. pyogenes, S. aureus, and Serratia marcescens.Candida albicans was highly susceptible to the methanol extract zone of inhibition of 25.0 mm.α-pinene, β-linalool, α-terpineol, pinocarveol, terpinene-4-acetate, α-thugene, β-phellandrene, β-caryophyllene, γ-terpinene, 1,8-cineole, acetyleugenol, benzylbenzoate, eugenol, cis-ocimene, and sabinene Plant secondary metabolites are the ingredients that confer therapeutic effects on medicinal plants [72].An assessment of the antimicrobial activities of the phytochemicals of the plants in Table 2 was carried out.Though many of the plants have been evaluated for their phytochemistry, only a few phytochemicals have their antimicrobial activities carried out against skin pathogens.The alkaloidal fraction of Annickia chlorantha stem back showed significant antifungal activities both in vitro and in vivo [88].Tamokou et al. [98] isolated seven compounds from the aerial part of B. lamium, among which lespedin (MIC = 6.25 µg/mL) and aurantiamide acetate (MIC = 50 µg/mL) significantly inhibited the growth of the tested skin pathogens.Betulenic acid isolated from the leaves of Mallotus oppositifolius also displayed a noteworthy activity against a dermatophyte, Microsporum langeronii with MIC value of 1.86 µg/mL [135].Betulenic acid elicited the best antimicrobial activity with the lowest MIC value in this review.
Further research is required on the metabolite to ascertain its biotoxicity and synergistic effect with other antimicrobial metabolites to further explore its potency in developing a commercially available antimicrobial agent.Regarding the antioxidant and antiinflammatory activities of the plants, ethanol extracts of the leaves of Chassalia kolly showed excellent activities with an IC 50 of 0.05 µg/µL and also showed higher anti-inflammatory activities than aspirin [103].This is traditionally used in the treatment of ringworm [34].Similarly, using the xylene and chorioallantoic membrane (CAM) anti-inflammatory model, Cyathula prostrata showed moderate activity [115], despite its traditional use for sores and rashes [28].It is recommended that further studies into the activities of C. kolly be carried out to assess its complete activities, isolate active metabolites, and harness its potential in treating skin ailments.
Wounds are one of the most common skin problems that may occur in any part of the skin due to breaking/puncturing the skin or rupturing other body tissues.For the wound-healing activities of the plants, the n-butanol fraction of the hydroethanolic leaf extract of Trianthema portulacastrum accelerated wound healing in rats by increasing the contraction and epithelialization of the wound and decreasing the level of inflammatory markers [157].This result validated the use of the plant in the management of wounds in Nigeria [15].The alkaloidal extract from the stem bark of Alstonia boonei also significantly increases the rate of contraction of the wound and reduced the epithelialization period in vivo [83]; the plant is traditionally used for snakebites [36].Similarly, in an in vivo study, the methanol extracts of the leaves and roots of Strophanthus hispidus and the roots and stem bark of Kigelia africana significantly increased wound contraction at days 11 and 7, respectively [131].Agyare et al. [76] revealed that the aqueous and methanol extracts of Alchornea cordifolia displayed wound-healing capacity at days 1 (p < 0.05) and 9 (p < 0.001).Other plants implicated in the study that have demonstrated wound-healing capacity include Anthocleista djalonensis [92], Clerodendrum splendens [108], and Carapa procera [101].

Conclusions
This review compiled the list of plants used traditionally in Western Africa for combating various skin ailments and the available scientific studies that have been carried out on the plants.A large percentage of the data was reported from a handful of countries, showing a large research gap in many West African countries on the traditional use of plants for skin ailments.The family Fabaceae is by far the most used, while Combretaceae, Asteraceae, and Euphorbiaceae were also well used.The most common habit of the plants was tree; leaf was the most-used plant part; and decoction was the most-preferred method of preparation.The biological activities of 82 out of the 211 plant species have been carried out, which means many plants still need to be investigated for biological activities related to skin diseases in West Africa.Plants such as Brillantaisia lamium, Kigelia africana, and Strophanthus hispidus that have demonstrated strong biological activities related to skin diseases are recommended for further research to identify the active metabolites and their mode of action.

Figure 1 .
Figure 1.PRISMA flow chart showing total studies identified, removed, excluded, and included in the review.

Figure 1 .
Figure 1.PRISMA flow chart showing total studies identified, removed, excluded, and included in the review.

Figure 3 .
Figure 3. Life forms of the reported plants.

Figure 4 .Figure 3 .
Figure 4. Parts of plants used to make herbal remedies.

Figure 3 .
Figure 3. Life forms of the reported plants.

Figure 4 .
Figure 4. Parts of plants used to make herbal remedies.

Figure 4 . 45 Figure 5 .
Figure 4. Parts of plants used to make herbal remedies.Cosmetics 2023, 10, x FOR PEER REVIEW 28 of 45

Figure 6 .
Figure 6.Number of plants used in treating different skin diseases.

Figure 6 .
Figure 6.Number of plants used in treating different skin diseases.

Figure 6 .
Figure 6.Number of plants used in treating different skin diseases.

Table 1 .
Medicinal plants used to treat skin diseases in West Africa.

Table 2 .
Biological activities of the plants used against skin diseases in West Africa.

Table 2 .
Cont.The extracts were also active against E. coli, P. aeruginosa, S. aureus, B. subtilis, and C. albicans with MIC values between 2.5-7.5 mg/mL.