Ethnobotanical Study of Medicinal Plants in Nagelle Arsi District, West Arsi Zone of Oromia, Ethiopia

Ethnobotanical study was conducted in Nagelle Arsi District, Ethiopia with the objective of identifying and documenting medicinal plants, associated indigenous knowledge and ethnobotanical practices of local communities. Household survey using semi-structured interviews, key informant interview, group discussions, field observations and market survey methods were used for data collection. A total 17 kebeles (smallest administrative unit) out of the 34 in the District were selected for this study, from which 90 informants for the household survey were interviewed. Eight key informants per each site were selected following purposive sampling method. Qualitative and quantitative statistical methods, priority ranking, paired comparison, direct matrix ranking, informant consensus and percentage distribution were used for data analysis. A total of 102 medicinal plants belonging to 85 genera and 55 families were collected and identified including four endemic plants to Ethiopia. The finding indicated that 65 species were used for treating human diseases, 31species for both human and livestock diseases and 7 for livestock diseases. Species used for treating cancer, blood pressure, malaria, diabetes, hemorrhoids and prostate problems were identified and documented. Seventeen medicinal plants were found to be wild edibles. Commonly used plant parts were leaves followed by roots and barks. The common routes of administration were oral followed by dermal. It was concluded that although the District was rich in medicinal plants, these species have been under serious threat due to agricultural expansion, deforestation, forest degradation and over harvesting for different purposes including firewood collections. Therefore, urgent conservation measures applying in-situ and ex-situ methods and strengthening sustainable management of natural forest were recommended.


Introduction
Ethnobotanical studies are useful in documenting, analyzing, and communicating knowledge and practices that would contribute to potential bioprospecting and production of commercial medicine for the betterment of human society. Indigenous and local communities have developed their own locality specific knowledge on plant use, management, and conservation (Balick & Cox 1996). Plants are indispensable and most important sources of both preventive and curative traditional preparations for human beings and for their animals since ancient times. Indigenous knowledge and practices have been major factors for the use and domestication of many multipurpose species. Local communities in developing countries such as Ethiopia are still dependent on locally available medicinal plants as about 80% of the country's population live in rural areas where availability and affordability of modern medicines remain out of reach for many families. Limited access to health stations, low number of nurses and medical doctors in those rural areas and lack of modern medicine in most clinics have been common features in many rural areas of Ethiopia.
As a result, indigenous and local communities developed and still making use of their rich knowledge on the taxonomy and use medicinal plants, preparations and applications of local medicines in their vicinity. Medicinal plants have been in use in traditional medicine and contemporary and alternative medicine both in developing and developed countries; thus a large number of people habitually use such medication. And its popularity also stems from the efficacy of the treatment and relative safety, with few or no side effects. Herbal medicines, because of their decentralized nature, are easily and quickly available, relatively cheaper and sustainable alternative to synthetic drugs and pharmaceuticals (Aziz et al. 2018;Wendimu et al. 2007).
Indigenous and local communities in Ethiopia have been using medicinal plants for treating various ailments of both human and livestock for centuries. The strong linkage between medicinal plants and indigenous knowledge has been documented by many authors. Ethnobotanical studies have been widely recognized as critical to identify threatened plants so that appropriate conservation measures are taken in time (Lulekal et al. 2008). However, conservation status of these plants has become a serious concern in many rural areas. The current loss of medicinal plants in the country due to climate change and anthropogenic factors has also negative impacts on indigenous knowledge of the communities that has been associated with these plants and their habitats. Deforestation and forest degradation, agricultural expansion, loss of grasslands and woodlands, over-harvesting, agricultural practices in marginal lands, overgrazing and urbanization are some of the major factors threatening biodiversity in 3 were selected from the age of 18 and above. Age group of the informants consists of young (18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35), middle (36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47)(48)(49) and elders (>50).

Data collection
Semi-structured interviews were conducted following Cotton (1996). These interviews were made with the help of translators who were conversant with the local language (Afan Oromo). But before conducting the interview, open discussions were held with to get consensus from the informants and also to clearly explain the objectives of the study. After consensus was reached, the interviews were conducted and data collected. The interviews were done mostly in the field in order to avoid the probable confusions with regard to the identity of medicinal plants. Moreover, the morphological characteristics, habitats and habits of medicinal plants were observed and recorded during and after the interviews. To correlate the common name with its scientific name, we collected plant specimens in the field, showed them to those interviewed in order to confirm the correct name of each uses of each species.
Group discussions were conducted in three different agroecological zones with number of 30 local community members which included eight traditional healers.
Guided field walks were also included in data collection aimed at observing, feeling, smelling and tasting different medicinal plants with the help of local informants. These ethnobotanical data collections were found to be more explanatory than talking without visualizing the plants. On the other hand, this guided field walk was used as an opportunity to record data on habitat, habit, and appearance, relation with other species and also for collecting voucher specimen.
Furthermore, market survey was made by selecting representative market places of the study area. Different sellers are interviewed and recorded the type of herbal drug sold in the market and multipurpose medicinal plants such as timber, farm implement, walking stick, food, spices, forage, wild edible fruits and traditional drug. And also data degree of utilization, variety, and economic importance of medicinal plants for the local community were collected.

Plant specimens collection and Identification
Herbarium samples of the listed medicinal plants were collected and recorded with the help of informants. The voucher specimen were coded, pressed, properly dried and taken to the National Herbarium of Addis Ababa University. Preliminary identification was also done in the field and further confirmation and identification of unknown species was done by using taxonomic key, comparison of authenticated voucher specimens deposited in Addis Ababa University herbarium and by the help of experts. Nomenclature of plant species follows published volumes of the Flora of Ethiopia and Eritrea.

Data analysis
Descriptive statistical method such as percentage and frequency distribution were employed to analyze and summarize the data on medicinal plants and associated knowledge. The relevant information collected and reported by local people, plant habit, plant parts used, methods of preparation, dosages and route of applications were analyzed through descriptive statistics.
Information provided by different informants was calculated using informants' consensus factor (ICF) following Leonti et al. (2001). Seven use-categories were used for that purpose. An ICF value close to one is taken as an indication of high intra-cultural consensus, that is, more healers use the same plant species, where as, a value close to zero as a low probability of similarity in use of plants by different informants.
Preference or priority ranking was calculated for seven selected medicinal plants important to treat human and livestock stomach problem and degree of scarcity in each Kebeles following Martin (1995). These plants were chosen based on the information obtained from key informants. Eight key informants from each study site were selected and invited to rank these plants. Accordingly, each informant given the highest value for the most effective medicinal plants used by local community to treat stomach problem and least scarce plant species, and the lowest value for the plants species that is the least preferred medicinal plants and commonly available (not scarce). The values assigned by each key informant for each of the seven medicinal plants were summed up and the total scores were calculated and ranked.
To compare the relative importance of those medicinal plants in multipurpose role and dominant use, a use value ranking was done following Martin (1995) and Cotton (1996). Eight key informants were chosen to give use value to each medicinal plant species. The use values were given as five = best, four= very good, three = good, two = less used, one= least used, zero = not used. Based on the relative benefits obtained from each plant species, each key informant gave scores for each use value for six multipurpose medicinal plants and then average value (average score) of the total value of each use diversity for each species in each study site were summed up and ranked to compare the degree of preference and the various uses of the plant species in each study site.
Paired comparison is another analytical technique used for evaluating the degree of preferences or levels of importance of certain selected medicinal plants. After random arrangement the pairs ordered alphabetically and numbered them sequentially. Five of the most important medicinal and wild edible plants of the study areas (based on their high use values as perceived and suggested by most informants of each study area) were selected and paired comparison was done following Martin (1995).

Medicinal plants diversity and associated Knowledge
A total of 102 medicinal plants belonging to 85 genera and 55 families that were used for treating human and livestock ailments were collected and identified (Appendix 1). Four medicinal plants endemic to Ethiopia were also identified during this study. Top five Plant Families with the highest number of medicinal plants included Fabaceae (seven species in seven general), Asteraceae (seven species in six genera), Lamiaceae (seven species in four genera), Solonaceae (six species in four genera) and Euphorbiaceae (five species in three genera). Trees and shrubs were the most commonly used medicinal plants comprising of 71.6% (shrubs represented by 37 species and tress 36 species) followed by herbs (23.5% or represented by 24 species). Besides, three climbers and two lianas were used as medicinal plants in the study area (Appendix 1).
Most identified and documented species (65 species or 63.74%) were used for treating human diseases, 30 species (29.40%) for treating both human and livestock diseases and seven species (6.86%) were used for treating only livestock diseases.
Out of the 90 informants participated in this study, males were 48 (53%) and females were 42 (47%). Comparison of their indigenous knowledge showed that women were more knowledgeable on medicinal plants collected from homegradens and men were better on species collected from wild. Furthermore, comparison between old (both men and women as one group (and young including boys and girls) showed that elders had better knowledge on medicinal plants than young inhabitants. It was documented that traditional healers do transfer their knowledge to the eldest son in their family and try to keep their knowledge as top secret.

Plant parts used for preparing traditional medicine
Commonly used plant parts by local communities to treat human and livestock disease included leaves, roots, barks and seeds. Leaves were the most widely used plant parts (46.66%) followed by roots and barks ( Table 1). The total number of species in Table 1 was greater than the total number of documented species showing the fact that different parts of the same plant were used for preparing remedy for different treatments (Appendix 2).

Types of human and livestock diseases treated with a number of species
Local communities used one or many species to prepare remedies. This study documented that a total of 30 human diseases were treated with a total of 65 plant species using 168 different types of preparations. Some plant species mixed with others plant species or mixtures of various substances were used to treat number of ailments (Table 2 and Appendix 2).
Similarly, the study showed that 13 livestock diseases were found to be treated with a total of 37 plant species and 68 preparations. For example, Anthrax is treated with 25 different plant species (Table 3 and Appendix 2).

Preparations, routes of administration and dosages
According to informants' perception, 85% of herbal preparations were from freshly collected plant materials followed by 15% of dried parts of the plants. There were number of mixtures using hot or cold water, coffee or milk. On the other hand, it was perceived that as volume of solvents increase, the time required for healing increases, reduces uncomfortable taste and limit adverse side effects. Methods of preparation included crushing and boiling, powdering for chewing, squeezing, grinding, smoking, washing, rubbing and cream treatments (Table  4 and Appendix 2). Traditional healers also used mixing two or more medicinal plants to treat selected ailments. For example, leaves of Artemisia rehan was mixed with bark of Croton macrostachyus for the treatment of evil eyes. Different applications were reported by the informants in the treatment of various human and livestock ailments (Appendix 2). The commonly recorded routes of administration were oral (53.33 %), followed by dermal (40 %), nasal (4%) and optical (2.66%). The most preferred mode of administration was oral because it was reported to be more effective for various ailments such as anti-parasites, and anti-bacterial diseases.
Different measuring materials such as glass of water, cup of tea, cup of coffee, tea spoons, and a range of litters were used to determine dosage. Most of the time prescriptions are based on age of the patient, gender; pregnancy status and the amount of remedies given by traditional healers. It was noted that dosages also vary based on indigenous knowledge of individuals. There also variations in time of the day, treatment duration, and mixture of substances. During this study, it was observed that there was a gap in having standard dosage determination among different traditional healers.

Ranking and scoring 3.4.1 Medicinal plants used for treatment of types of ailments
Eight traditional healers were asked to rank seven medicinal plants based on their indigenous knowledge using the degree of treatments for human and livestock disease and effectiveness. Bacterial, parasitic and fungal diseases were reported to be the most common in the study area. Verenonia amygdalina, Croton macrostachyus, and Podocarpus falcatus, were ranked as the most useful medicinal plants for treating parasitic and bacterial diseases (Table 5). Hagenia abyssinica was also pereceived as important medicinal plant for treating tape worm problems.

Direct matrix ranking
Using direct matrix ranking method most important multipurpose species were identified. The eight key Informants reached consensus on the rank and score for six highest preferred multipurpose species by considering their value or desirability. Accordingly, Syzgium guineense was found to be the most important multipurpose plant scoring 23 followed by Allophylus abyssinicus and Celtis africana, each scoring 20 (Table 6).

Paired comparisons for five marketable medicinal plants
A paired comparison was made for five medicinal plants which have market values in the study area. Ximenia americana and Syzgium guineense were the most highly preferred species (Table 7). These species were found in local market places during their fruiting season and sold to different users. All these species were found in natural forest in the wild.

Informant consensus
Ten most popular plant species agreed upon during the study were selected and ranked. It was observed that some of medicinal plants were in higher demand and most frequently used by the local community than others. Informant consensus analysis showed that Ruta chalepensis (14%), followed by Ocimum lamiifolium (11%) and Vernonia amygdalina (13%) were most importany medicinal plants for treating human ailments (Table 8).

Economic importance of some medicinal plants in the study area
In addition to their medicinal value, several plant species recorded during this study do play an important role in economic activities of the local communities. Some wild and cultivated medicinal plants such as Podocarpus falcatus, Agave sisalina, Artemisia rehan, Brassica olearcea, Croton macrostachyus, Coriandrum sativum, Cordia africana, Celtis africana, Ekebergia capensis, Hagenia abyssinica, Lippia adoensis,Moringa stenopetala, Opuntia ficus-indica, Olea europea subsp.cuspidata, Prunus africana, Ricinus communis, Ruta chalepensis, Syzgium guineense, Withania somenifera, are commonly collected and sold in the local or urban market places. Olea europea subsp.cuspidata, and Ekebergia capensis. Withania somenifera, Brassica olearcea are used for smoking traditional bee hives. It was reported that the good smell of smoke from these species has been used to attract bees to bee hives. Several of the documented medicinal plants (for example, Opuntia ficus-indica, Syzgium guineense and Ximenia Americana) are also widely used for human consumption as fruits. Coriandrum sativum, Lippia adoensis, Ruta chalepensis and Brassica olearcea are highly demanded for their condiment value in almost all markets in the study area. Furthermore, a number of tree species were used to produce good quality timber and also for construction including Podocarpus falcatus, Cordia africana, Croton macrostachyus, Celtis africana, Ekebergia capensis, Hagenia abyssinica and Prunus africana. It was recorded that 1Pices of timber was sold for 250 to300 Ethiopian Birr or $9-13 US Dollars in local market. Moringa stenopetala was perceived as the most important and widely used plant species for different human ailments and food value and was sold 150 Ethiopian Birr per kg or $6.12 US Dollars. Artemisia rehan and Ricinus communis werea lso commonly sold in the markets (Table 9).

Threats to medicinal plants
This study covered three different agroecological zones: High lands (altitude range greater than 2500 m asl), mid altitudinal range (1500-2500m asl) and low lands (< 1500m asl). The highest numbers of medicinal plants were collected from altitude between 1500-2500m asl followed by low land areas.
According to perception of pastoralists and observations during this study, major factors causing decline of medicinal plants and associated indigenous knowledge included anthropogenic and natural factors (climate change). Agricultural land expansion into forest and grasslands, deforestation, over exploitation of some selected species, land degradation, unsustainable fuel wood and charcoal production and overgrazing were identified as anthropogenic problems in the area. Frequent drought was perceived as natural problem resulting in environmental degradation and loss of species in the lowland areas (Table 10). Ten Informants' ranked their degree of damage. Deforestation was identified as the main threatening factor, followed by agricultural land expansion, fuel wood and charcoal production.

Discussions 4.1 Medicinal Plants Diversity and Habitats Comparisons
The study result showed that Nagelle Arsi District was rich in medicinal plants having 102 species in 85 genera, and 55 families. Fabaceae, Asteraceae, Lamiaceae and Solonaceae were most important families with many medicinal plants. Similar results were reported from different parts of Ethiopia (Kidane et al. 2018;Lulekal et al. 2008;Lulekal 2013;Yineger 2005). Most medicinal species were found in natural vegetations (wild) in agreement with previous reports (Awas & Demissew 2009;Gebrehiwot 2010;Issa et al. 2018;Kidane et al. 2018;Lulekal et al. 2008;Yineger 2005) and also indicating the fact that there is high need to conserve and sustainably manage forest ecosystems and grasslands to ensure availability of these medicinal plants for current and future generations.
The habitats of most medicinal plants were mid altitudinal ranges. Similar results have been reported from other study areas (Abdela et al. 2018;Gebrehiwot 2010). On the other hand, this altitudinal range is the most favorable for cereal crop production causing a serious concern of further loss of medicinal plants. This concern need to be noted and practical action is needed on time to minimize the unregulated negative impacts of agricultural expansions on medicinal plants.

Indigenous knowledge on the use and parts used of medicinal plants
Indigenous and local communities rely on herbal medicines to prevent and cure various health problems. Traditional healers have been playing an important role in the primary health care system of the rural community who had less access and could not afford the cost of modern medication. We documented that old and middle aged women and men had more knowledge than the young generation in agreement with previous research findings ( Asfaw and Nigatu 1995;Awas 2007;Gemedo-Dalle et al. 2005;Giday et al. 2003;Teklehaymanot 2007). It was also observed that the young generation showed no interest to learn and make use of traditional medicines. The other practical challenge noted during this study was that there was no documentation of indigenous knowledge by traditional healers as the knowledge is transferred orally to the eldest son in the family. Leaves were the most widely used plant parts in Nagelle Arsi District followed by roots in agreement with many studies elsewhere (Giday et al. 2003;Kidane et al. 2018). However, other research results reported roots as the most frequently used plant parts in many areas in Africa (Abdela et al. 2018;Issa et al. 2018;Lulekal et al. 2008;Lulekal et al. 2013).

Comparative assessments on medicinal plants used for treating ailments, parts used and routes of administration
Shrubs were the most commonly used (43 %) followed by trees (35%) and herbs (22 %). This finding was not in agreement with report by Isa et al. (2018) who documented that the dominant medicinal plants in Algoz area, South Kordofan, Sudan were herbs followed by trees and shrubs. The dominance of trees and shrubs in Nagelle Arsi District could be an indicator of high degree of unregulated agricultural expansion into high forests, woodland and grasslands resulting in loss of herbaceous species.
The majority of remedies in the study area were prepared from fresh materials of leaves, barks, roots, and fruits of the plants. Most of them were prepared by crushing, boiling, chewing, smoking, grinding, and powder forms.
The most commonly used route of administration was oral followed by dermal. Oral administration was preferred because it was believed to be more effective in agreement with research results from somewhere else (Gebrehiwot 2010;Giday et al. 2003).
It was also observed that traditional medicine was prescribed or given based on the age of the patient, gender and pregnancy status. And also amount or volume of remedies given by traditional healers varies according to their respective indigenous knowledge. It was also noted that dosage still remains serious concern as there was diffrences among healers for treating the same kind of health problem by applying different dossages of the same herbal medicine as there was no established standard of measurement. Similar problem was also reported from other places (Ashagre et al. 2016;Gebrehiwot 2010;Lulekal et al. 2008;Tolasa 2007;Yineger 2005). Lack of precision and standardization has been mentioned as a global drawback of the traditional healthcare system that needs to be rectified by putting in place global and national system that would recognize the role and contribution of traditional healers and also that ensures effective benefit sharing mechanism including intellectual property

Threats to medicinal plants and potential solutions
The most serious threats to medicinal plants in the study area were agricultural land expansion, deforestation, over exploitation and land degradation, unsustainable fuel wood and charcoal production and overgrazing. Similar threatening factors have been reported from different regions within Ethiopia (Ashagre et al. 2016;Lulekal et al. 2008). This unregulated agricultural expansion resulted from high population growth and lack of land use policy in the Country. With the aim of increasing agricultural productivity, forest lands and grasslands have been converted into farmlands causing loss of local biodiversity including medicinal plants. Increasing agricultural productivity should not be at the expense of forest and grassland biodiversity and associated ecosystem services. Agricultural intensification should be considered as the only option to increase productivity using all technological inputs and human technical expertise. The other threatening factor was overexploitation of medicinal and other plants for timber, fuelwood and construction materials. Increasing energy availability to inhabitants in local towns and promoting plantation forestry to minimize negative impacts on natural forest and woodland ecosystems was noted as critical actions that should be taken as soon as possible. Some of the medicinal plants perceived by local communities as being threatened such as Millettia ferruginea, Urtica simensis, Solanecio gigas and Maytenus addat were also included in the IUCN Red lists. This could be one practical example of the complementary nature of indigenous and scientific knowledge that we need to make use of for the conservation and sustainable use of medicinal plants.
It was recommended that there is high need to conserve medicinal plants and their ecosystems in Nagelle Arsi District and other parts of the Country. Both regional and federal governments should give priority to conservation of these precious resources using both in-situ and ex-situ conservation methods. Ethiopia has good environmental and biodiversity domestic legislations. However, law enforcement remains a practical challenge. Therefore, empowering institutions by both human and financial resources is critical to ensure sustainable utilization of medicinal plants in the Country. There should be strong regulation on production and sale of firewood. Furthermore, putting in place a functional system that would protect intellectual property rights of the traditional healers and also ensures their benefit sharing is important and timely. Technical support and capacity development of traditional healers for safe handling of medicinal plants and and their medicine were identified as important interventions. Bioprospecting on most commonly used medicinal species and establishing pharmacological industries was identified as one area of priority to promote conservation and sustainable use of medicinal plants in Ethiopia. Protection of intellectual property rights, capacity development and participatory bioprospecting researches were identified as important measures that would promote sustainable use of the rich medicinal plants in the study area and beyond.

Conclusion
The findings of this study revealed that Nagelle Arsi District was endowed with several medicinal plant species used for treating human and livestock ailments. Diverse medicinal plants were used for treating different diseases. Human ailments such as stomach discomfort and internal parasites, cough, fever, diarrhea, malaria, hemorrhoids, tapeworm, blood pressure, liver, kidney, toothache, tonsillitis, wound, cancer, headache, diabetes, prostate gland problem, asthma (respiratory complication), and many others were treated using indigenous knowledge of the local communities.
Local communities did prefer to use traditional medicines for their primary health care because of the fact that these remedies were available easily and also cheaper than the modern medicine. As leaves, roots and barks are the most frequently used plant parts for the preparation of remedies; there is a serious concern over the sustainable use of these medicinal plants. There is a need for conservation of these plants and public awareness raising with focus on threats to natural resources in general and medicinal plants in particular.
Although remedies were prescribed and given based on age, gender and pregnancy status, the knowledge gap on the right and effective dosage remained a serious concern calling for close follow up and support from the health sector and also from other related Institutions. The major threats to medicinal plants in the study area were anthropogenic factors such as agricultural land expansion, deforestation, over exploitation and land degradation, fuel wood and charcoal production and overgrazing. Conservation of medicinal plants using both in-situ and exsitu methods, rehabilitation of degraded ecosystems, sustainable use of natural resources and market linkages for potential medicinal plant products were recommended as a result of this study.