Ethnobotanical Leaflets 12: 164-170. 2008.
Ethnomedicinal Use of Plant Species in Ijesa Land of Osun State, Nigeria
J. Kayode1, L. Aleshinloye1 and O. E. Ige2
1Department of Plant Science, University of Ado-Ekiti, Ado-Ekiti, Nigeria
2Department of Plant Science and Biotechnology, Adekunle Ajasin University, Akungba-Akoko, Nigeria
Issued 15 March 2008
A combination of social survey and direct field observation was used to identify the medicinal plant species used in Ijesa land of Osun State, Nigeria. Voucher specimens of the species were obtained and the relative abundance for each of the identified botanical species was determined.
A total of 45 plant species belonging to 30 families were identified. Our survey indicated they were used in the control of 22 diseases. Tribal information of these species is passed from one generation to another. These species were found to have multiple uses in the study area. Only 29% of the species were cultivated in the study area. A considerable proportion of these plant species were extracted predatorily and collections were done indiscriminately without consideration for size and age. At present, only 47% of the medicinal plants fall in the abundant category for this study area. Most of these abundant species were cultivated for their fruits, seeds, leaves or vegetables. Finally, strategies that would enhance the conservation of the species in the study area were proposed.
The Ijesa are a distinct ethnic Yoruba indigenous group in Osun State, Nigeria. They are found in local government areas in Ilesa West, Ilesa East, Oriade, Obokun and Atakumosa. Ijesa, like other Yoruba groups, cherished and preserved their culture seriously (Kayode 2002). Part of this culture is the use of plant species for the maintenance of their health.
A great many ethnomedicinal studies have been conducted in Nigeria (Gill 1992). However, according to Kayode (2006), most of these studies were conducted on a scattered basis usually by various ethnic groups of the country. There is however a dearth of such studies carried out on the ethnomedicinal values of plant species in Ijesa land. Recent initiatives revealed that Ijesaland, like other areas situated in the rainforest region of the country, is fast experiencing massive deforestation.
Thus, the study being reported here is part of an on going project aimed at the evaluation and conservation of useful plant species in Nigeria currently being conducted at the Department of Plant Science, University of Ado Ekiti, Ado-Ekiti, Nigeria.
MATERIALS AND METHODS
A combination of social surveys and direct field observations (after Lipp 1989) was used in this study. A major market center was identified in each local government area of Ijesa land. In each market center, botanical vendors were identified and surveys of the medicinal plant species sold in the markets were carried out. The vendors were interviewed with a view to determine the source of the species and their conservation status. Voucher specimens of the species were obtained.
Also, two rural communities that could still be described as being far from urban influence were selected in each local government area of Ijesa land. In each community, 20 individuals who had each maintained continued domicile in the village for 20 years were selected and interviewed on the plant species utilized for medicinal purpose. Voucher specimens of the species identified by the respondents were also collected.
All the interviews (market and village interviews) were conducted with a fairly open framework that allowed for focus, conversational and two-way communication. The voucher specimens were taken to the Herbarium of the Department of Plant Science, University of AdoEkiti, Ado-Ekiti, Nigeria for proper identification and preservation.
The relative abundance of each of the identified botanical species was determined within 1 km radius from the center of the community and defined using the abundance scale of Bongas et al (1998) as occurrence of less than five individuals as rare (R), 5 to 10 individuals as occasional (O), 1I to 30 individuals as frequent (F), 31 to100 individuals as abundant (A), and over 100 individuals as very abundant (VA).
Secondary information was obtained from records at the Health Departments of each of the local government secretariats, Osun State Ministry of Health and General Hospital, Ilesa, Osun State. Information on the nature of active ingredients present in each of the botanicals that were identified was obtained from the literature.
RESULTS AND DISCUSSION
A total of 45 plant species belonging to 30 families (Table 1) were identified. These were reported to be used in the control of 22 diseases (Table 2). The ethnomedicinal knowledge of the peoplebeing passed down from one generation to anotherhad now formed a part of the peoples culture. Most species were found to have multiple uses in the study area. Only 13 of the species, representing 29% of the total, were cultivated within the study area (Table 3). Among the species, C. papaya, C. citrullus, M. indica, P. guajava and P. guineensis, were cultivated for their fruits and/or seeds, which apart from their nutritional values, also constituted major sources of income in the study area. S. bicolor and Z. mays were also cultivated for their grains that formed the bulk of the major food supply. G. arboreum and N. tobacum were cultivated purely for their economic values as they formed parts of the major cash crops in the study area. B. alba and V. amygdalina were cultivated for their leafy vegetables. The cultivation of C. articulatus was attributed to its leaves used for wrapping and its stems used as a source of raw-material for the production of mats. C. tora was being cultivated to provide shade.
Also shown in Table 3 is that a considerable proportion of these plant species (42%) were extracted predatorily. Such extraction entailed the destruction of sources (Homman 1994, Kayode and Ogunleye 2008). Thus such destructions, in an environment where most of the species were growing wild, might likely contribute to genetic erosion of plant species in the study area. Field observation revealed that debarking of these species was done indiscriminately and quite often they were circularly carried out. Previous studies by Cunniingham (1988) and Kayode (2008) had revealed that circular debarking often leads to the death of the plants. Most of the identified species were indigenous species with poor reproduction and regenerative capacities (Kayode 2004, 2008). Momma (1992, 1994) had revealed that when the rate of regeneration is slower than the capacity to extract, the integrity of the mother plant is no longer protected hence extraction ad infinitum could no longer be guaranteed.
Though over 50% of the plant species (see Table 3) were extracted non-predatorily, yet field observation revealed that collection of plant parts were often accomplished by pulling or cutting of the branches, thus making such collection to be destructive. Collections were done indiscriminately without consideration for size and age. Such collections, according to Kayode and Ogumleye (2008), often results in species depletion. Results from this study revealed that only 47% (Table 3) of the medicinal plants were in abundant category in the study area. Most of these abundant species were cultivated for their fruits, seeds, leaves or vegetables. C. afer, E. caryophyllus and O. subscorpioides grow freely and their wildlings were usually preserved while E. convolvuloides, N. lotus, P. stratiotes and P. muellerianus grow widely as weeds in the study area.
Field observation also revealed that medicinal parts, often dried, of the plant species observed as frequent and rare were being sold in the markets sampled in the study area. Marketing is done by women vendors who often traveled several kilometers to collect their botanical stocks. In conclusion, a high population growth rate (2.8%) and poverty rate in Nigeria, coupled with the diminishing economic resources of the country, has forced people to access plants which were formerly considered as cheap resources for their immediate needs. At present, the rate of deforestation in the country is unprecedented; hence, the need for the conservation of these resources cannot be over-emphasized. The major goal of such conservation efforts should ensure the protection of all representative vegetation types. Consequently, as suggested previously by Shinwari and Khan (2000), researchers need to develop a deep understanding of plant life cycles, pollination and dispersal mechanisms, biochemical analyses and relationships among species and their habitats.
Threatened species should be identified and their cultivation encouraged, trainings should be conducted on proper method(s) of collection and drying, identification and sustainable harvesting. In situ conservation methods, which according to Moore (1990) will involve the maintenance of species in their original self-perpetuating populations, should be carried out. Kayode (2008) and Kayode and Ogunleye (2008) have stressed the need for each district, such as a local government area, to have a botanical garden where most of the medicinal plant species can be cultivated and preserved.
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Table 1. Identified medicinal plant species in Ijesa land, Osun State, Nigeria.
Table 2. Diseases cured by the identified medicinal plant species in Ijesa land, Osun State, Nigeria.
Table 3. Ecological attributes of the medicinal plant species in Ijesa land, Osun State, Nigeria.