Indigenous plants used by the Otuo tribe of Owan East Local Government Area , Edo State , Nigeria

Background:  Traditional medicine remains an integral part of the Otuo tribe in Owan East Local Government Area of Edo State. Aim:  The study is aimed at documenting the ethnobotany of the Otuo tribe by evaluating the uses of plants found in the area, identifying the importance value (IV), fidelity level (FL) and principal taxonomic groups of the plants. Methods:  Data were gathered following an oral interview of unlettered herbal practitioners. Literate men, women and young settlers in the community were cross-examined using a semi-structured questionnaire. Fifty respondents made up this study size. Data were collated to report botanical names, common and vernacular names of the species of plants surveyed. Information on the use, methods of preparation and plant part used was documented. The FL and IV were determined. Results:  101 plants belonging to 46 families were reported. The best-represented family was the Fabaceae with 11 species followed by the Euphorbiaceae with 6 species. Of the 101 plants, 80 plants have medicinal uses and 58 have other economic uses. Amongst the medicinal plants,  Azadirachta indica  had the highest FL and IV of 100 and 1.0, respectively, followed by  Cymbopogon citratus  with FL of 96; both plants are used to treat malaria. The major ailments treated with plants by the Otuo tribe include malaria, cataracts, rheumatism and dysentery, amongst others. Conclusion:  The people of Otuo are rich in plant-based remedies. They devotedly practise local medicine use because it is cost-effective and efficient, thereby contributing greatly to the economic development of the area.


Introduction
Ethnobotany is an aspect of plant science that deals with the general use of plants in a particular environment or society (Sofowora 1982).It studies the relationship between man, plant and the various roles plants play in the environment and what meanings society or the environment give to them.Plant use is unique to different areas of the world, and some of these plants have specific and special purposes.The plants used by any tribe or region may include drug plants, food plants, ceremonial plants, etc. Ethnobotany was historically practised by explorers who recorded the use of plants by the natives of an area in their travels.The historical knowledge of these plants was largely based on casual observations and use record, which formed the basis of today's knowledge of plant usage (Cotton 1996).Various disciplines have emerged from the field of ethnobotany, and one of such is ethnomedicine.
Ethnomedicine is the use of plants by members of an indigenous culture for which there is no organised medical system or formal training by the prescriber.In the traditional African healing system, ethnomedicine is also referred to as folk medicine, herbal medicine and native medicine.According to the World Conservation Union (WCN), approximately one-quarter of all prescription drugs are derived from plants and many of these come from the humid tropical forests (Oseni 1989).The plant parts used in ethnomedicine include the roots, leaves, bark, twigs, flowers and seeds.Plants are either used fresh or dry mostly in the form of decoction.Generally, more than one species of plant are used in preparation of the decoction.Some traditional medicines are of pharmaceutical value, while others combine the pharmaceutical with supernatural powers.
Traditional medicine is an integral part of the people who practise it.An indication of the strength of the traditional (indigenous) culture is seen because a large number of herbalists still practise and heal different ailments with herbal remedies.Although some of the practices involve rituals and superstition, most of the remedies are based on rather simple preparation and application of plants commonly found in the area.The insight of these medical remedies is jealously guarded and controlled by a few individuals, many of whom are elders and they are respected by the inhabitants of the area.Many of the people have used herbal remedies.The people of Otuo continue to use herbal remedies because they are cheaper, easily available and have produced positive results when used in time past.
In Nigeria, traditional medicine is used to treat a host of health conditions such as mental disorders, fractures, insomnia and infertility (Enwereji 1999).Notable contributions towards Nigerian medicinal plants have been made by Ainslie (Ainslie 1937), who was the first to list plants used in native medicine in Nigeria (Akpata 1979;Ayensu 1978;Gill 1992;Gill & Opara 1988;Idu & Olorunfemi 2000;Idu & Omoruyi 2003;Lambo 1979;Mume 1976;Sofowora 1986Sofowora , 1993)).The knowledge and utilisation of folk medicine by aboriginal cultures are useful for conservation of cultural traditions and biodiversity and for community healthcare and drug discovery in the present and future.Thus, traditional medicine should not be considered as a system of old, but as a heritage that needs refinement and development.This study is aimed at exploring and documenting the ethnobotany of the Otuo tribe.Otuo is surrounded by a mountainous terrain with a climate comparable to that of a rainforest zone which promotes the growth and development of a rich biodiversity.The natives are mainly involved in agriculture, weaving, pottery and blacksmithing.The major agricultural products are yam and cocoa.The majority of the plants found here have botanical and medicinal properties.

Field methods
The field trip was done in February 2016.The ethnobotanical data were collected through oral interviews of the herbal practitioners, men, women and young settlers in the community using a semi-structured questionnaire.The respondents were followed into the bush for identification and collection of plant parts.The total number of respondents was 50, consisting of 46 men and 4 women.Data were collated to give the botanical names, common names and local names of the various plant species.Information about their use, method of preparation and specific plant part used was also recorded.
The assistance of some natives of the clan coupled with the offer of cash incentive facilitated the ease with which the informants divulged their ethnobotanical and ethnomedicinal knowledge.Interviews were documented with photos of the plants.

Species identification
Plants were identified using textbooks, online catalogues and at the University of Benin Herbarium.Voucher copies of plants in the form of photographs taken were deposited in the Herbarium of the Department of Plant Biology and Biotechnology, University of Benin.

Data analysis
Fidelity level (FL) quantifies the importance of the species for a given purpose which is defined as the ratio between the number of informants who independently suggested the utilisation of a particular species for treatment of a particular ailment and the total number of informants (Idu et al. 2008).
FL was calculated using the following equation: where Np represents the number of informants that reported a use of a plant species to treat a particular ailment.
N represents the total number of informants.
The importance value (IV) measures the importance of a species to the community.IV was calculated using the following equation: http://www.jomped.co.zaOpen Access IV=nis/n where nis represents the number of informants who consider a species most important and n represents the total number of informants.

Results and discussions
A total of 101 plant species belonging to 46 families were collected.Of these plants, 80 had medicinal uses.The surveyed plants are arranged alphabetically using their botanical name, family names, local name, vernacular name, part used and method of prescription or uses in Table 1.The IV, quotation frequency and FL were also recorded.The plants have been used by the respondents and according to them the plants are effective.
Of the 101 plants, 43 were trees growing in the forests, around farms and in dwelling areas, 29 shrubs, 19 of herbaceous habit and 2 under shrubs (Figure 2).The most represented family was the Fabaceae with 11 species followed by Euphorbiaceae with 6 species and Apocynaceae, Moraceae and Poaceae with 5 species each (Table 2).Economically, the plants are used for various purposes which include birth (during naming ceremonies of newborn babies), traditional marriages, for building and fencing, as edible seeds and fruits and so on (Figure 3).
Home gardens were associated with the majority of the houses visited and most of the plants encountered there have both medicinal and economic uses.One of the most abundant species found in dwelling areas is Calotropis procera which is used to treat cough.(1) The leaves are used to treat malaria and arthritis.
A decoction of the fresh leaf is made.Take half a glass three times daily for arthritis and take a glassful three times daily for malaria.
(    Plants with medicinal uses summed up to 80 (Table 1) and are used to treat a host of ailments.Medicinal plants used to treat stomach pain and cough were the most abundant followed by those used in treating rheumatism, skin infection, fever, gonorrhoea and diabetes (Figure 4).

Scientific name
The majority of the plants had high FLs and IVs.Azadirachta indica and Cymbopogon citratus had the highest FLs of 100 and 96 and are both used in the treatment of malaria.A plant can have more than one medicinal uses as in the case of Eucalyptus officinalis, which is used in the treatment of typhoid, urinary tract infection and asthma, and the herbalists in most cases use different plants of their choice to treat a specific ailment; for example, stomach pain can be treated using Crotalaria longirostrata, Dialium indum, Pergularia daemia or Phyllanthus niruri.Most of the plant remedies were prepared from a single plant source, while a few others have to be in combination with other plants.
The plants that have ethnobotanical uses were 58 (Table 2) and the majority of them are used for food.The majority of the plants studied had both economic and medicinal properties like Ficus exasperata which is used as a washing agent for pots and also used in the treatment of piles.Also, Psidium guajava is eaten as a fruit and used medicinally in the treatment of hypertension.
Plants with magical and spiritual use such as Gomphrena celosioides were usually accompanied by some spells and incantations known by the herbalists or witchdoctors alone.
In the Otuo tribe, traditional medicine is still widely practised, and the herbalists believe that plants provide better means of treating various ailments than orthodox medicines.It has been recorded that traditional medicine is the source of primary healthcare to 80% of the world's population (Hoffman & Gallaher 2007).Traditional healers have claimed success in the treatment of various ailments like gonorrhoea, diabetes and other diseases.Ariba et al. (2007) reported that 42.3% of Nigerian clinicians agreed that many patients prefer native medications to modern drugs.This also supports the use of herbs for treatment of various ailments by the Otuo people of Edo State.
In the survey previously performed on the ethnomedicinal plants found in the Otuo clan, 51 species of plants were recorded (Idu et al. 2006), and, of these, 22 were repeated in this study.A total of 79 new plants were recorded in this survey.In total, this study has shown 80 plants with medicinal properties.The ethnomedicinal uses of the plants mentioned in the previous survey are in accordance with this survey.This shows the effectiveness and general use of these plants by the Otuo people.
There is an urgent need to preserve our biodiversity as there is a rapid increase in the extinction of plant species.Conservation should be practised to protect plant species from overexploitation, destruction and extinction.In addition, most of these plants are not being documented (Idu et al. 2006); efforts should be made to record and document the knowledge of traditional medicines by the various herbalists before such knowledge goes extinct.This is important to boost the economic improvements which the sales of these remedies have brought to poor homes in the study area.
A major challenge is the secrecy of the knowledge of the plants by the various herbalists as most of them http://www.jomped.co.zaOpen Access

Conclusion
Otuo tribe has a rich cultural heritage and the people are knowledgeable about the use of countless plants found in their community.The 101 plants surveyed in this study are all medicinal with steady quotation frequencies, FLs and IVs.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.

FIGURE 1 :
FIGURE 1: Map of Owan East Local Government Area showing the study area.

FIGURE 2 :
FIGURE 2: Distribution of Plant types in Otuo, Owan East Local Government Area, Nigeria.
Otuo is one of the major towns in Owan East Local Government Area of Edo State, Nigeria.It is located on latitude 7.00691 and longitude 6.00522 with postcode (ZIP): 313107.It had an area of 1240 km 2 and a population of 154 385 persons as at the 2006 census.Owan East is boarded by Akoko Edo in the north, Etsako West Local Government Area in the east, Ekiti State in the west, Owan-West in the southwest and Esan Central/Uhunmwonde Local Government Area in the south (Figure 1).The local government comprises eight clans: Emai clan, Igue clan, Ihievbe clan, Ikao clan, Ivbi-Mion clan, Ivia-Ada-Obi clan, Otuo clan and Uokha clan.

TABLE 1 :
List of plants with medicinal uses.

Serial number Scientific name Family Vernacular and common names Parts, uses and modes of preparation QF FL (%) IV
(1)hornea cordifolia Mill.Arg.(UBHdt/OE/029)EuphorbiaceaeOva(1)Theleaf is used to treat eye-related problems, such as redness of the eyes.(2)Theleaf is used in combination with other plants to treat Lassa fever.(3)Infusion of fresh leaves is used to treat depression of the head of a newborn.(1)Adecoction of the pineapple is made with other herbs which are used to treat skin infection and typhoid fever.(2)Theunripefruit is a vermifuge.(UBHdt/OE/092)MeliaceaeDogoyaroItisusedtotreatmalaria.Fresh leaves and bark are boiled then filtered.A cup is taken daily for three days.(1)Itisusedtohealthenavel of a newborn baby after the umbilical cord has been cut off.Fresh leaves are squeezed to extract the liquid.The liquid is applied on the navel once a day.(2)Theleavesused to treat cough.ConnaraceaeEbe-khe-ebe(1)The moisture from the leaf is used to stop vomiting.(2)Thefruitiseatenthree times daily to cure hypertension.Table 1 continues on the next page → http://www.jomped.co.zaOpenAccessArecaceaeOtaghie (palm tree) (1) Pound the leaves in a mortar with palm wine.The juice is squeezed and applied to the body to treat convulsion.(2)Pound the leaves and mix with palm wine.Take a cup thrice daily to treat dysentery.(1)Theleaves or bark can be used to treat diabetes and chest pain.(2)It is used to treat irregular menstruation.Cut the bark into pieces and soak for 24 h.Drink a glassful twice daily.

TABLE 2 :
List of plants with economic uses.