Taxonomically, the genus Elaeis is a member of the order Arecales [1] , family Palmae, subfamily Cocoideae, subtribe Elaeidinae [2] [3]. The genus Elaeis [4] consists of two main species, the common oil palm Elaeis guineensis (the African oil palm) native to Africa, and Elaeis oleifera or Elaeis melanococca (the American oil palm) indigenous to South and Central America. A third species is sometimes considered, Elaeis odora or Barcella odora, though its taxonomy has not been confirmed. The genus Elaeis is present in the tropical regions of Africa and in Central and South America [5]. The genus Elaeis has a trans-Atlantic (Africa-America) distribution, with E. oleifera from the neotropics and E. guineensis from Africa [5]. E. guineensis is the major economic species, as fruits of E. oleifera have much lower oil content and are used only locally in their natural area of distribution.

Health and disease are measures of the effectiveness with which human groups, combining cultural and biological resources, adapt to their environment [6]. The use of traditional medicine and medicinal plants in most developing countries, as a normative basis for the maintenance of good health, has been widely observed. In human society from time immemorial medicinal plants have played an important role in prevention and control of diseases. Medicinal plants continue to provide valuable therapeutic agents, both in modern and in traditional medicine [7]. At least 80% of the world’s populations especially in developing countries use plant materials as their source of primary health care [8]. Palms “the princess of the plant Kingdom”, represents one of the most important plant family with respect to human use. In local terms, food and medicine is not strictly separated, and palm products operate in many ways that cannot be isolated from the larger ensembles of elements and practices of which they are part. Oil palm has been described as ‘‘probably the most useful tree in West Africa’’ [9]. In Africa, palm oil has many traditional uses [10]. The oil palm is as old as creation. The use of oil palm by early humans is well known from the archaeological records. Such uses date back to at least 4000 years BP [11] , and it appears that people in West Africa were actively cultivating oil palm as early as 3600 - 3200 BP [12]. Human use of oil palm may date as far back as 5000 years in West Africa; in the late 1800s, archaeologists discovered palm oil in a tomb at Abydos dating back to 3000 BCE [13]. Excitingly, both E. guineensis and E. oleifera are typically closely associated with human settlements and movement [14]. Oil palm was used medicinally before any written records surviving to modern times. Oil palm is among the plants well known for its pharmacological properties [15]. Anecdotally, a variety of medicinal uses have been ascribed to oil palm, including all parts of the plant [16] [17]. E. guineensis has medicinal and other uses [18]. Besides its domestic, economic and environmental value, every part of the oil palm is valuable for medicinal purposes [19] [20]. E. guineensis is a plant widely used by the traditional natives of oil palm growing areas, particularly West Africa [15].

Ethno-botany is defined as the traditional knowledge of indigenous communities about surrounding plant diversity and how various people make use of indigenous plants found in their localities, that is, how communities of a particular region make use of indigenous plants in the region for food, clothing, shelter, medicine and other domestic activities [21]. Native people can tell much about their local plants in the area of ethno-medicinal and cultural uses. They also know how to prepare the plant for these uses, when and how to harvest it and which parts, and also when and where it grows. This traditional knowledge of plant use has been gained by trial and error over centuries and is priceless and irreplaceable. Indigenous knowledge is extremely important to humanity. One of the vital applications of indigenous knowledge systems and practices of plants is in the human and animal health care. Recent international policy resolutions have recognised the importance of indigenous knowledge and the potential of traditional vegetables in promoting nutrition and health [22]. This invaluable knowledge is being lost by the destruction of the natural ecosystems, the acculturation and anthropogenic activities of these people [23]. It is knowledge we can in fact learn from if we stop this destruction of the ecosystem [24]. Knowledge of medicinal plants combined with spirituality continues to thrive in Africa today [25]. Some recent ethno-botanical field studies confirm that divination still plays a major role in the traditional knowledge systems, and palms are still used for this purpose just as they were many years ago [26] [27] [28]. Ethno-medicinal use of plants is one of the most successful tools used in pharmaceutical industry searching new therapeutic agents for various fields of biomedicine [29]. Palms are prominent elements in African traditional medicines [30]. There is a dire need to document, preserve, perpetuate and incorporate the traditional medicinal uses of palms in general, oil palm in particular into the primary health care system. It is said that taste all and hand the knowledge down [31]. It is, however, a challenge to find detailed information on the traditional medicinal uses of oil palm, which are an integral part of indigenous medicinal systems.

Earlier reviews on African palm ethno-medicine [30] and on ritual uses of palms in traditional medicine [32] covered some aspects of traditional medicinal uses of palms in general, including E. guineensis. Earlier other reviews on diet and health aspects [20] and on medicinal uses [33] were limited to some aspects of traditional medicinal uses of E. guineensis. In addition, a review of the health benefits of the leaf extracts of E. guineensis has been provided extensively [34]. However, the present review is to provide detailed and additional information on traditional medicinal uses of E. guineensis and E. oleifera. This review paper aims at the exploration, perpetuation and preservation of indigenous knowledge of the oil palm possessing medicinal properties for the benefit and further questionnaire survey. This review, therefore, is set to produce an update by exploring many of the documented traditional medicinal uses of the different plant parts and/or their products of oil palm and their implications in human health. The review, however, does not extend to the core botanical aspects of the oil palm. By analyzing ethno-medicinal studies in one database we were able to demonstrate the value of oil palm in traditional medicine, and provide recommendations for the areas that should be targeted in future ethno-botanical surveys. This ambitious and wide-ranging article attempts to compile in one place everything that is known or speculated about Elaeis in a multidisciplinary tour-de-force.

The study is concerned with the ethno-medicinal uses of oil palm in the world. Two species of Elaeis namely E. guineensis and E. oleifera were included in the present study. In this study, ethno-medicine data of different parts and products of oil palm were extracted from reliable sources of traditional medicine. In addition, published scientific reports about the ethno-medicinal uses of this herbal medicine were collected via literature search in databases such as Medline, PubMed, Embase, Science Direct, Scopus, SID and Google Scholar during October, 2018 to November, 2018. The authors carried out a meta-analysis to review and assemble existing information on the ethno-medicinal uses of Elaeis spp. based on a diverse set of case studies and ethno-botanical studies. Traditional medicinal use records were organized by each plant part used for the above two oil palm species in each publication. Traditional medicinal uses were reviewed according to palm species and categories of plant part and or their product.

The results are organized following the part of oil palm used for each of the two species.

Vast information is available on ethno-medicinal uses of E. quineensis across the African and American continents in several references, published between 1937 [60] [104] and till date [52] [68] [74]. On contrary, scanty information is found on ethno-medicinal uses of E. oleifera across the American continent in only one reference published in 1997 [18]. Although there were several studies on ethno-medicinal uses of E. guineensis in Africa: East Africa (Rwanda), West Africa (Togo, Liberia, Guinea, Benin, Nigeria, Ghana, Islans of Fernando Po and Burkina Faso), Central Africa (Cameroon and Gabon), North Africa (Moracco) and East and Central Africa (Democratic Republic of Congo), there was only one study on ethno-medicinal uses of E. guineensis and E. oleifera in America: Central America (Nicaragua) [18]. It indicates that E. guineensis is probably the most useful oil palm species in West Africa, while E. oleifera the most useful oil palm species in Central America.

We found references to ethno-medicinal uses of E. guineensis in sub-Saharan Africa [26] [46] [60] [62] [63] [65] [73] [74] [86] [87] [88] [89] [98] , and they were used for different purposes. Based on the published information, the ethno-medicinal usefulness of E. guineensis in African continent is remarkably high. E. guineensis is native to tropical Africa, from Sierra Leone in the west through the Democratic Republic of Congo in the east. It is native to west and southwest Africa, specifically the area between Angola and The Gambia; the species name guineensis refers to the name for the area, Guinea, and not the modern country which now bears that name. It is generally agreed that the E. guineensis is originated from the equatorial tropical rain forest region of Africa, precisely along the gulf of Guinea. It was domesticated in its native range, probably in Nigeria, and moved throughout tropical Africa by humans who practiced shifting agriculture at least 5000 years ago. European explorers discovered the oil palm tree in the late 1400’s, and distributed it throughout. The species is also now naturalised in Madagascar, Sri Lanka, Malaysia, Indonesia, Central America, the West Indies and several islands in the Indian and Pacific Oceans. E. guineensis exists in the wild type and cultivated state. E. guineensis is cultivated in humid tropical regions of Africa, Central and South America and Asia. E. guineensis is present in Africa (Angola, Benin, Burundi, Cameroon, Central African Republic, Congo, Congo Democratic Republic, Côte d’Ivoire, Equatorial Guinea, Gabon, Gambia, Ghana, Guinea, Guinea-Bissau, Kenya, Liberia, Madagascar, Malawi, Mauritius, Nigeria, Reunion, Sao Tome and Principe, Senegal, Sierra Leone, Sudan, Tanzania, Togo, Uganda and Zimbabwe [38] [105] [106] [107] ; Central America (Caribbean, Costa Rica, Dominican Republic, Guatemala, Honduras, Martinique, Nicaragua and Panama) [105] [107] [108] , South America (Bolivia, Brazil (Amazonas, Bahia and Para), Colombia, Ecuador (Galapagos Islands), Paraguay, Peru, Suriname and Venezuela [105] [107] [108] [109] , North America (Mexico and USA (Florida and Hawaii)) [108] [109] [110] , Oceania (Cook Islands, Fiji, French Polynesia, Guam, Marshall Islands, Micronesia, Federated states of New Caledonia, Niue, Palau, Papua New Guinea and Solomon Islands) and it is of introduced origin and non-invasive [107] [109] and Asia (Cambodia, China, Christmas Island (Indian Ocean), India (Andaman and Nicobar Islands, Andhra Pradesh and Kerala), Indonesia (Java and Sumatra), Malaysia (Peninsular Malaysia, Sabah and Sarawak), Myanmar, Philippines, Sri Lanka, Thailand and Vietnam [105] [107] [108] [109]. Our expectation that E. guineensis would be used extensively in traditional medicine and far more than on the African continent was not confirmed by our survey of the relevant literature.

There is currently only one document on E. oleifera ethno-medicinal properties [18]. Since our literature search was rather intensive we conclude that there are no ethno-botanical studies focusing on the ethno-medicinal usefulness of E. oleifera distributed in Central America, Northern South America, Brazil, Colombia and Madagascar. E. oleifera is native to tropical Central America and South America. The main belt runs through the southern latitudes of Cameroon, Côte d’Ivoire, Ghana, Liberia, Nigeria, Sierra Leone, Togo and into the equatorial region of Angola and the Congo. However, traditional medicinal uses of this species were not reported from any one of these countries. No ethno-botani­cal uses have been formally reported from Ecuadorean populations of E. oleifera. In Ecuador, the only indigenous name reported in the literature comes from the Achuar communities, where it is known as Yunchik [111]. However, there is a limited amount of information from other countries about traditional uses, which include folk remedies, beverages, insect repellents and cooking [14]. There are many parts of the world yet to be explored for ethno-medicinal uses of E. quineensis and E. oleifera. Further studies and collecting trips may generate a more complete picture and suggest answers to why (or if) there are few traditional medicinal uses of E. oleifera compared to other common species E. quineensis. Future ethno-botanical surveys should be directed at the central African region, because palm species richness (and plant species richness in general) is particularly high in this area, and only few ethno-botanical studies available have focused on this region.

The importance of E. guineensis crop is due to their medicinal properties and utilization as food [35]. The review of literature revealed that both oil palm species of the genus Elaeis under study were found to be involved in various traditional medicinal practices in African and American continents. E. quineensis has a wide range of ethno-medicinal uses as it was cited to treat ailments like malaria, anaemia, gonorrhoea, amenorrhea, menorrhagia, hernia, rheumatism, bronchitis, hepatitis, small pox, measles, influenza, fever, dysentery, pleurisy, lumbago, cancer, asthma, diabetes, epilepsy, headache, earache, perinatal abdominal pain, hiccoughs, convulsions, filariasis, candidiasis, Tinea cruris. Further, it was cited to reduce mental fatigue and mental disorders, to reduce palpitations and heart trouble, to regulate body temperature, to heal ulcers, boils, piles, cuts and fractures, for sexual impotence, male and female sterility, easy flow of menses, miscarriage, to reduce bleeding during pregnancy, to promote easy delivery of women, for postpartum placental retention, to increase milk flow in nursing mothers, to encourage children to walk at an early age, to accelerate maturity and softness of boils and abscesses, to remove thorns from body and a poison antidote. E. oleifera has a narrow range of ethno-medicinal uses as it was cited to cure only stomach or gastrointestinal disorders (e.g. stomach ache, ulcers, etc.). The data revealed that while E. guineensis was found relevant in several use categories, E. oleifera was found relevant in few use categories. With 258 medicinal use records for different use categories (infections/infestations, digestive system disorders, genito-urinary system disorders, ritual/magical uses, respiratory system disorders, pain, inflammation, skin/subcutaneous cellular tissue disorders, injuries, pregnancy/birth/puerperium disorders, muscular-skeletal system disorders, circulatory system disorders, endocrine system disorders, poisonings, veterinary medicine, nervous system disorders, nutritional disorders, blood system disorders, cultural diseases and disorders, mental disorders, abnormalities and defined symptoms), E. guineensis tops the list of palms used in traditional medicine in Africa [112]. It means that among numerous palms used in African traditional medicine, E. quineensis has been widely used in the traditional medicine due to its edibility. Further, ostentatious that palm oil or red palm oil always comes from E. guineensis, this was the most commonly documented palm species for medicinal purposes in Africa. Our review shows that E. guineensis has been, and probably still are pervasive in African medicinal systems. Its use in medicines reflects the spiritual framework of traditional medical practices, and African oil palms themselves are important and often crucial in disease treatment and prevention. Since E. guineensis is mainly found in the home gardens [35] , it is commonly used in African traditional medicine as a household remedy. The documented ethno-medicinal uses may be attributed to the presence of a high concentration of minerals and various other phytochemicals of diverse chemical structure. However, there is no assurance that E. guineensis used for the treatment of a particular disease has any biologically active component; it may only be its symbolic or spiritual meaning that serves as a powerful ingredient. The results of this study provide the basis for further pharmacological studies on the herbal remedies used. The present study concluded that further clinical and phytochemical experimentation is needed.

The data on the medical use of traditional preparations from all parts of E. guineensis display a wide spectrum of applications in African and American continents. E. guineensis and E. oleifera were cited as being used for treatment of more than a disease. This confirms the multi-curative ability of medicinal plants, in general, oil palm in particular. The review also revealed that the indigenous people have administering preparations made from bark, roots, leaves, infructescence/inflorescence, fruits and seeds of Elaeis. While only fruits of E. oleifera were used in traditional medicines, all parts of the E. guineensis were used in traditional medicines. However, the most commonly used part was the leaf, followed by the fruit, seed, root, inflorescence/infructescence. The ethno-medicinal uses of all the mentioned parts were found in both older and recent literature, although most of the recent medicinal use records were associated with the palm leaf. Every part of E. guineensis has been of use in the various traditional and folk systems of medicines where E. guineensis palms are found to be indigenously growing. All plant products of the E. guineensis were used in traditional medicines. However, the most commonly used part was the palm oil extracted from the mesocarp of fruits, followed by the palm kernel oil extracted from the seed, plant sap extracted from the palm heart and palm wine. Each part of the oil palm tree has some medicinal property and is thus commercially exploitable.

Analysis of data revealed that some of the plant parts and crude products of E. guineensis were used in traditional medicine purely, while other plant parts and crude products were used in traditional medicine mostly without being mixed with other plants, and less commonly in mixtures, sometimes in mixture with products of animal origin (e.g. tortoise, giant black ant, electric fish, crocodile, snail, shea butter, etc.). It means that in some treatments, the oil palm is the central element of traditional medicines. In other cases, oil palm is used in mixtures with other plants and or animals or products. Hence, oil palms are not the primary ingredient, but support the medicinal treatments in some way, like in the case of palm oil, used as a medium to blend and make coherent the various ingredients. It is noteworthy that palm wine and palm oil, which are commonly consumed in Africa, often assist the treatment and the contact with the supernatural world. Because several traditional medicinal uses of E. guineensis listed in the literature could not be unequivocally referred to a particular species, the picture we draw remains somewhat incomplete with regards to the taxonomic basis for ethno-medicinal uses.

Ethno-medicinal uses of E. quineensis were documented for 17 different ethnic groups in 5 different countries in Africa and one country in America. The analysis of data revealed that the dominant ethnic groups associated with the usage of different parts of African oil palm in traditional medicine were Mano/Idoma in Liberia [71] [87] , Yoruba in Nigeria [66] [82] [88] , Idoma in Nigeria [50] , Otuo in Nigeria [68] , Ikot Ekpene, Abiakpo Ikot Essien, Abiakpo Edem Idim, Ikot Enwang, Adatak and Uruk UsoIkot in Nigeria [39] , Annang in Nigeria [36] , Ibibio in Nigeria [54] , Igala in Nigeria [99] , Miskitu in Nikaragua [18] ), Bubis in the Island of Fernando Po (Personal communication), Masango in Gabon [89] and Baka in Cameroon [43]. On contrary, ethno-medicinal uses of E. oleifera were documented for only one ethnic group Miskitu in only one country Nikaragua in Central America [18]. The review also revealed that over many years, these local communities in Africa and America have acquired valuable practical knowledge on the traditional medicinal uses of oil palm and therefore to some extent actively manage their health guided by indigenous knowledge. It is imperative that this knowledge, which is mostly passed by word of mouth from generation to generation, should be adequately documented for referral purposes. Furthermore, the active participation of such natural custodians and practitioners of valuable knowledge is guaranteed in bioactive principles and the development of new drugs. There is a need to build on the existing resources of indigenous landraces of Elaeis species by improving on their management to sustain the plant genetic resources as well as further domestication of highly valued indigenous landraces of Elaeis species. Focus is to be given to indigenous/ tribal/ ethnic/ minorities in these countries with contributions to definitions of these groups, the extent of their diversity, and the importance of their traditional medicinal knowledge of local oil palm resources. The few studies we reviewed that explained the medicinal uses of oil palms in detail were classic anthropological works that embraced studies of the entire native African tribes and cultures [43] [50] [87]. The best accounts of traditional medical practices came from those who spent years among the local people, not only observing but also sharing their everyday life. Many of the oil palm uses mentioned in our review came from these sources, but in many cases we do not know whether the cited medicinal uses are still practiced today, as recent studies on African medicinal plants are scarce.

In this systematic review, the ethno-botanical studies conducted on oil palm (Elaeis spp.) indicate that of the two species of Elaeis under study, E. guineensis has been used extensively in local treatment of various ailments, while few ethno-medicinal uses of E. oleifera have been documented. Every part of E. guineensis has been of use in various traditional and folk systems of medicines where E. guineensis is found to be growing. Virtually all the different parts and products of the E. guineensis plant have one or more ethno-medicinal uses and have been used for different purposes in various parts of the African and American continents. According to the results of this study, all parts of E. quineensis have health and equitable benefits, in general, and have immense potential in the treatment of gonorrhoea, menorrhagia, and bronchitis, headache, rheumatism, to promote healing of fresh wounds and treat skin infections. The data revealed that E. guineensis is conspicuous in traditional medicines in Africa contributing to healthcare of rural dwellers. Properly studied and recorded, this traditional knowledge could revolutionize the world of medicine.

Based on literature survey and screening, it can be deduced that although E. quineensis is traditionally used in the treatment of various diseases for long time, no preliminary screening on the chemical composition, potential therapeutic properties, clinical and toxicological aspects of different plant parts and products has been carried out. Hence, researchers may have to focus on understanding of the total composition of different plant parts and products of oil palm to explore its potential in indigenous health care system. Further research is also required to explore therapeutic properties, clinical and toxicological aspects of this plant. Considering the significance of African oil palm in the field of ethno-medicinal science, work must be carried out to exploit the therapeutic utility of this plant to combat diseases. Attention must be given on the development of modern drugs after thorough investigations on the bioactivity, mechanism of action, pharmacotherapeutics, toxicity and similar aspects of chemical constituents of African oil palm extracts. There is still a lot of scope in this field for better utilization of this wonder plant. As the global scenario is now changing towards the use of nontoxic plant products having traditional medicinal use, development of modem drugs from oil palm should be emphasized for control of various diseases. In fact, time has come to make good use of centuries―old knowledge on oil palm through modern approaches of drug development.

The review also revealed that over many years, several local communities in Africa have acquired valuable practical knowledge on the traditional medicinal uses of oil palm and therefore to some extent actively manage their health guided by indigenous knowledge. There is an urgent need for agricultural research centres, national agricultural research systems, universities, and community-based organizations to work together under a shared policy framework with the aim of developing a strong evidence based health care linking traditional knowledge and modern medicine. A comprehensive proactive policy framework is the best way to conserve indigenous knowledge and incorporate the same into the primary health care system.

There are many parts of the world yet to be explored for ethno-medicinal uses of E. quineensis and E. oleifera. Further studies and collecting trips may generate a more complete picture and suggest answers to why (or if) there are few traditional medicinal uses of E. oleifera compared to other common species E. quineensis. Future ethno-botanical surveys should be directed at the central African region, because palm species richness (and plant species richness in general) is particularly high in this area, and only few ethno-botanical studies have focused in this region. A better understanding of the cultural context of medicinal use of oil palm species is needed in order to obtain a more accurate and complete insight into palm-based traditional medicines. Effort must be made to provide meticulous reports on traditional remedies, as the enduring value of African medicines lies not only in the materials used, but also in the methods and the concepts underlying them.

The authors declare no conflicts of interest regarding the publication of this paper.

Reddy, M.T., Kalpana, M., Sivaraj, N., Kamala, V., Pandravada, S.R. and Sunil, N. (2019) Indigenous Traditional Knowledge on Health and Equitable Benefits of Oil Palm (Elaeis spp.). Open Access Library Journal, 6: e5103. https://doi.org/10.4236/oalib.1105103