Ethnobotanical Study of Medicinal Plants Used to Treat Human Diseases in Berbere District, Bale Zone of Oromia Regional State, South East Ethiopia

This paper reports an ethnobotanical study that focused on the traditional medicinal plants used by local communities to treat human diseases. Ethnobotanical study of medicinal plants was carried out from June 25 to September 5, 2015, in Berbere district of Oromia region, Ethiopia. The study focused on documentation of medicinal plants used to treat various human diseases in the study area. Ethnobotanical data were collected using semistructured interviews, group discussion, guided field walks, and observations with participants. Preference ranking, paired comparison, direct matrix ranking, and informant consensus factors (ICF) were used to analyze the importance of some plant species. A total of 70 medicinal plants, distributed in 56 genera and 46 families, were collected and identified. Plant family with the highest medicinal plants in the study area used for various diseases treatment was Euphorbiaceae (11.4%). The result of growth form analysis showed that shrubs constituted the highest proportion of medicinal plants (48.6%). Roots, 43 (44.8%), were the most frequently utilized plant parts for preparation of traditional herbal medicines. Crushing was a widely used mode of preparation of traditional remedies where oral administration (37.5%) was the dominant route. The highest informants consensus factor (ICF) values were linked to gonorrhea and syphilis disease (0.95); the lowest was linked with external parasites and wound (0.69). Local people in the study area possess traditional knowledge of medicinal plants to treat various human ailments; however, agricultural expansion and disinterest of young generation became the major threat to medicinal plants. It is, therefore, necessary to preserve this indigenous knowledge on traditional medicines by proper documentation, identification of plant species used, and herbal preparation. To save medicinal plants from further loss, involving local communities in cultivation of the most utilized medicinal plants is recommended.


Introduction
Plant resources have remained an integral part of human society throughout history. After fulfilling the primary needs like food and shelter, man has sought for a suitable remedy among plants for curing various diseases [1].
Traditional medicine is defined as indigenous medicine that is used to maintain health and to prevent, diagnose, and treat physical and mental illnesses differently from allopathic medicine based on theories, beliefs, and experiences [2]. Traditional medicine has been used for thousands of years with great contributions made by practitioners to human health, particularly as primary health care providers at the community level and has maintained its popularity worldwide [3]. According to Sofowora [4], about 60-85% of the population in every country of the developing world has to rely on traditional medicine. The practice of traditional medicine is widespread in China, India, Japan, Pakistan, Sri Lanka, Thailand, and Korea [5]. In China, traditional medicine accounts for around 40% of all health care delivered and is used to treat roughly 200 million patients annually [6].
In Ethiopia, plants have been used as a source of medicine from time immemorial to treat different ailments due to its long history, and traditional medicine has in fact 2 Evidence-Based Complementary and Alternative Medicine become an integral part of culture [7]. These traditional medical practices and remedies are recorded in oral tradition and in early medico-religious manuscripts and traditional pharmacopoeias, which, according to the estimates of some historians, date back to the 15th century AD [8].
Ethiopia possesses about 6,000 species of vascular plants which could be due to its different topography and climatic conditions [9]. About 80% of human population and 90% of livestock rely on traditional medicine in this country [10]. Traditional medicine of Ethiopia is commonly used to treat various human and livestock ailments. Traditional healers known by different names in different parts of the country are the primary players in the curative aspect of traditional medicine practice [11]. Thus, this study was initiated to document the traditional medicinal plants knowledge accumulated by local communities of Berbere district.

Study Area.
Berbere district is situated between 06 ∘ 33 N and 06 ∘ 75 N and 039 ∘ 95 E and 040 ∘ 29 E. It is located at about 526 km southeast of Addis Ababa, in Bale Zone of Oromia Regional State. This district has 17 kebeles which are characterized by undulating highlands in the north and lowlands in the south (Figure 1).

Selection of Study Sites.
A reconnaissance survey of the study area was conducted from June 25 to July 5, 2015. The study sites were selected depending on recommendation from elders, local authorities, and altitudinal range. Thus, the study was carried out in eight kebeles from two agro-climatic zones.

Selection of Participants.
A total of 60 participants (41 men and 19 women) were selected randomly from the representative kebeles. Representative common participants and knowledgeable traditional medicine practitioners (key participants) of Berbere district were selected using random and purposive sampling approaches, respectively, following Martin [12]. Twenty key participants were selected purposively and systematically based on the recommendations of knowledgeable elders, local authorities, and development agents. The selection of key participants was also based on the quality of explanations that particular participants gave during an interview. Local healers automatically qualified as key participants being traditional experts who are guardians of indigenous knowledge on medicinal plants.

Ethnobotanical Data Collection.
Ethnobotanical data were collected from July 6, 2015, to September 5, 2015. The standard data collection methods [12][13][14] have been followed to document indigenous knowledge of the local community on health, use, conservation, and threats of medicinal plants. The techniques employed for data collection were semistructured interviews, group discussion, guided field walks, and observations with participants. Semistructured interviews were undertaken based on checklist of questions prepared in English and translated to 'Afaan Oromo' , the language of local people. Information was carefully recorded during an interview with a participant. The interview was guided to cover the key topics on the checklist. The place and the time for interview were set based on the interest of the participants. Field observations were performed with the help of local guides on the morphological features and habitats of each medicinal plant species in the field. Brief group discussions were made with participants regarding the medicinal plants in the study area. The discussions were conducted on threats to medicinal plants, conservation of the medicinal plants, and transferability of knowledge in the community. Letter of consent was taken from Jimma University, prior to the data collections. Verbal consents were also obtained from the participants by performed group discussions about the objectives of the study prior to the interviews, and all data were collected through their oral consents.

Voucher Specimen Collection.
The voucher specimens were collected onsite during guided field walk, numbered, pressed, dried, and deep frozen for identification. Identification of specimens was carried out both in the field and in the herbarium. Identification was also carried out using Flora of Ethiopia comparing with already identified specimens. Finally, the identified specimens were stored at the National Herbarium of the Addis Ababa University, Ethiopia.
2.6. Data Analysis. The collected ethnobotanical data were entered into Excel spreadsheet 2007 and summarized using descriptive statistical methods such as frequency, percentage, tables, and graphs. Preference ranking and paired comparison were computed following [13]. Preference ranking was conducted for five important medicinal plants used to treat stomachache. Ten randomly selected participants from total key participants were participated in this exercise to identify the best preferred medicinal plants for treatment of stomachache.
In paired comparison, ten participants were selected and asked to choose the best item from every pair according to personal perception in treating wound. The total number of possible pairs [15] was obtained by applying the formula n (n-1)/2, where n is the number of medicinal plants being compared. A total rank of paired comparison was obtained by summing the number of times each item was chosen. An item with the highest frequency of choices had the highest score.
Direct matrix ranking is used to compare multipurpose uses of a given plant species based on information gathered from participants, number of multipurpose species were selected out of the total medicinal plants, and use diversities of these plants were listed for four randomly selected key participants to assign use values to each species.
Informants consensus factor (ICF) was calculated for each category to identify the agreements of the participants on reported cures for the group of ailments. The ICF was calculated as follows [15].
Evidence-Based Complementary and Alternative Medicine where ICF is informants consensus factor, nur is number of use citation in each category, and nt is number of species used.  Figure 2). This finding shows that the most represented life forms of medicinal plants in the study area were shrubs followed by herbs. Similar findings were also reported in the earlier works in Ethiopia. For instance, [19] identified 46.8% shrubs and 24.1% herbs from Cheffa semi-wetland; [17] documented 46% shrubs and 25% herbs from Boosat subdistrict; [20]  collected 37% of shrubs from Sekoru district, Jimma Zone. The more recent studies conducted by [21,22] also reported the dominance of shrubs for preparation of traditional medicines. However, other findings [18,[23][24][25] indicated that herbs were the most frequently used plant categories.

Plant Parts Used to Treat Human Diseases.
People of the study area harvest different plant parts for the preparation of traditional remedies (e.g., leaves, roots, seeds, barks, and fruit). In the study area, 43 species (44.8%) were harvested for their roots (Figure 3). This is because it is believed that roots contain more concentration of the active ingredients.
The finding of the roots as the contributor of higher number of plant species used for medicinal purpose than other plants parts is in line with similar study conducted by [17], in which roots (31.4%) were reported as the most widely used plant part followed by leaves 24.4%. The study conducted by [20] showed that roots 42% as a major plant parts used and [26] also documented root 35.8% as a major plant parts used in the treatment of human ailments. In        this regard, [27] have indicated that plant harvest involving roots, rhizomes, bulb, bark, and stem has a serious effect on the survival of the mother plant in its habitat. However, the findings of [18,21,[28][29][30] indicated that traditional medicinal preparations mainly involve the use of leaves. As leaves of medicinal plant species were also reported to be harvested for most remedy preparations next to roots, collection of leaves could be promoted as a more sustainable method since in most cases at least many leaves are left over on the parent plant [24].

Method of Preparation, Dosage, and Administration.
In the collection of data concerning the preparation of medicine, participants reported various skills associated with herbal preparation. The results showed that the most remedies were prepared from a single plant or plant parts (73%) and preparation from combined plant species was 27%. Similarly, various research findings reported the use of single plant species or parts for traditional remedy preparation [22,23,31]. The potency of using a mixture of different plant or plant parts increased compared to using a single plant to cure a disease is evident. The majority of the remedies (78.6%) in the study area were prepared from fresh parts of medicinal plants followed by dried form (15.7%) and (5.7%) prepared either from dry or fresh plant parts. The study conducted by [32] indicated that 86% of preparations were in fresh form and [33] reported that most of (64%) medicinal plants were used in fresh form and 36% in dried from. The dependency of local people on fresh materials is mostly due to the effectiveness of fresh medicinal plants in treatment as the contents are not lost before use compared to the dried forms.
The local communities employ various methods of preparation of traditional medicines for different types of diseases. The preparations vary based on the type and actual site of disease treated. The principal methods of remedy preparation were reported to be through crushing, which accounted for 30 preparations (38.5%) followed by pounding which accounted for 14 preparations (18.8%), powdering accounted for 10 preparations (14.6%), squeezing accounted for 7 preparations (10.4%), decoction accounted for 4 preparations (8.3%), crushing and pounding together accounted for three preparations (5.2%), and 4.2% of traditional medicines were prepared using concoction (Figure 4). Crushing as the most common mode of preparation is in agreement with the findings of [20,34] who noted that the principal method of remedy preparation was through crushing. However, [27] in a similar study on people of Wonago District reported that powdering was a dominant method of preparation of remedy. Medicinal plants were applied through different routes of administration (Table 1). In the study area, the substantial proportions of prescriptions were administered orally (37.5%), followed by external application (13.5%), creaming (10.4%), and dry bath (8.3%). This result is in line with the findings of [29,32,35]. Internal ailments were commonly treated by making the patient drink herbal preparations; tooth infection was treated by crushing and applies on the remedial plant part on the tooth surface; skin infections such as ringworm were treated by creaming herbal preparations on an infected skin.
Concerning the dosage, local people of the study area used various units of measurement such as finger length (e.g., for root, bark, and stem), pinch (e.g., for powdered), and numbers (e.g., for leaves, seeds, fruits, and flowers) and locally made spoons from plants were used to estimate and fix the amount or dosage of medicine. For human disease treatment, the smallest number is one and the highest is 7 for the case of leaves. In the case of palm measurement units, the lowest is half palm and the highest is 3 palms depending on the age of the patients. The lack of precise dosage is one of the drawbacks of traditional medicinal plants [33,36]. Tip part of the index figure is commonly used as a measurement of dose [37]. The result of [19] from Tehuledere district, South Wollo, showed that about 31% preparations were taken with known dosages mostly quantified by spoon, cup of tea, palm, and other equipment. The majority plant remedies (69%), however, are taken with no fixed dosage.
According to respondents, preparations were prescribed to patients differently for different age groups, sex, and other conditions. The dosage prescription for children was mostly lower than for adults. The amounts of remedy and prescription rates were generally dependent on the degree and duration of the ailment. Treatment durations varied between 1 and 7 days. This result is in line with the result of [29] in which treatment durations varied between 1 and 7 days.
Recovery from the disease, disappearance of the symptoms of the diseases, fading out of the disease sign, and judgment of the healer to stop the treatment were some of the criteria used in determining duration in the administration of the dosage. Most of the remedies were reported to have no serious adverse effects except vomiting and temporary inflammations. This could be attributed to the low toxicity of the remedy preparations of the medicinal plant species used by the traditional healers in the study area. A similar study by [36] indicated that some herbal preparations are considered harmless.

Knowledge on Medicinal Plants.
Ethnomedicinal knowledge is concentrated in the elderly and relative members of the community and difficult in its transfer from the elders to the young generation. Most of the respondents (79%) preferred to transfer their indigenous knowledge to their family verbally and the remaining participants (21%) through showing the medicinal plants in the fields. Indigenous knowledge transfer to the young generation is considered poor which may cause erosion of the practice. The study revealed that medicinal plant knowledge transfer to the young generation is affected by modernization. This might be related to the diminishing of interest of the young generation on indigenous knowledge. Similar result was reported by [20] where young people showed disinterest on traditional medicinal plants.

Ranking of Medicinal Plants.
Preference ranking of 5 medicinal plants that were reported as effective for treating stomachache was conducted after selecting ten key participants. Stomachache is the mostly occurring disease treated by more medicinal plants. The participants were asked to compare the given medicinal plants based on their efficacy. The results showed that Stephania abyssinica scored the highest mark and ranked first indicating that it was the most effective in treating stomachache and followed by Solanum incanum (Table 2).
For medicinal plants that were identified by the participants to be used in treating wounds, a paired comparison was made among six of them using ten participants to know their rank. Wound is frequently occurring external health problem in the study area. The results that were obtained from all the participants were summed up and compared plants were abbreviated in the table. Accordingly, Olea europaea subsp. cuspidata selected five times and stood first indicating that it is the most effective in treating wound followed by Prunus africana, Euphorbia heterophylla, Acacia senegal, Cyphostemma sp., and Clematis simensis ( Table 3). The frequency of wound to be treated by more medicinal plants was also reported by [38] in other parts of Bale region. Nine medicinal plants were documented for wound treatment.
In the study area, a number of medicinal plants were found to be multipurpose species being utilized for a variety of uses. Direct matrix ranking showed that of the total medicinal plants Croton macrostachyus is the most multipurpose use medicinal plant followed by Warburgia ugandensis ( Table 5). The finding of [39] also reported Croton macrostachyus as the highest multipurpose use in Farta district South Gonder Zone of Amhara Regional State. (ICF). The diseases of the study area have been grouped into various categories based on the site of occurrence of the disease, condition of the disease, and treatment resemblance of the disease to the local people. The informant consensus factors have been calculated for each category ( Table 4). The highest ICF (0.95) value was obtained for diseases related to gonorrhea and syphilis and the least one (0.69) was associated with boils, dandruff, eczema, haemorrhoids, scabies, Tinea versicolor, and wound.

Threat and Conservation of Medicinal Plants of Study
Area. Medicinal plants are at increasing risk from destruction of their habitats (agricultural expansion, fire, construction, overgrazing, and urbanization) and over harvesting of known medicinal species [40]. According to [41] about 15,000 medicinal plant species may be threatened with extinction world widely due to habitat loss and over harvesting and it is estimated that the earth is losing one potential major drug every two years. In the study area, the people also rely on medicinal plants for various purposes such as charcoal, medicine, firewood, construction, and food. The major threat to medicinal plants in the study area was agricultural expansion which accounted for 55%, charcoal production (15%), and fire wood accounted for 18%. The result of [42] indicated that intense deforestation became the major threat to medicinal plants in Zay people. According to Evidence-Based Complementary and Alternative Medicine 13    [43]. This indicates that due consideration should be given for conservation of these plants since they are being widely exploited for purposes other than their medicinal value. Availability of medicinal plants has been affected by a dramatic decrease in the area of native vegetation due to agricultural expansion, deforestation, fire, overgrazing, and charcoal and firewood [40,42].
The influences of human on the natural habitat of medicinal plants are the problems for the conservation of medicinal plants and associated knowledge. The effort to conserve medicinal plants in the district was observed to be very poor. Some participants have started to conserve medicinal plants by cultivating at home gardens, though the effort was minimal. About 13.8% of the medicinal plants collected were reported as found cultivated at home gardens and these include plants like Carica papaya, Coffea arabica, and Jatropha curcas. The result of [32] indicated that only 5.7% of medicinal plants were cultivated in home garden showing minimal effort of medicinal plant conservation in Mena Angetu district. Suggestion given by [44] stated that natural resources could be utilized best in sustainable way if management practices are complete. In fact, such valuable activities require appropriate action, and changes by the full range of societies and stakeholders involved in the conservation, production, and management as well as use of medicinal plants. Since an action on conservation and sustainable use of medicinal plants need involvement of various sectors and greater public support, it needs a continuous task of creating public awareness [45]. The review made by Megersa et al. [46] suggested  that identifying serious threats to medicinal plants and how local people manage medicinal plants will help to understand the best conservation strategies.

Conclusions
A study on medicinal plant utilization in area revealed that the communities commonly use medicinal plants for maintaining their primary healthcare. The study resulted in documenting 70 medicinal plants species where Euphorbiaceae is the leading family with the highest proportion of medicinal plants. Most of (58) medicinal plants in the study area were harvested from wild. Shrubs were found to be the dominant growth form of medicinal plants used for preparation traditional remedies and followed by herbs. Roots were found to be the most frequently used plant parts for the preparation of traditional remedies. Traditional medicine preparation mostly involves a single plant and the method of preparation was mainly crushing followed by pounding. Depletion of indigenous knowledge among the people of the study area was serious due to disinterest of young generation to gain the knowledge. Oral based knowledge transfer, unavailability of the species, and influence of modern education were considered as the main factors. The main threat on medicinal plants in the study area arises from agricultural expansion. Utilization of root plant parts for traditional medicine preparation could also be considered as a threat. Although Berbere district was found to be rich in medicinal plant diversity, the effort to conserve the plants and associated indigenous knowledge was observed to be very poor. Thus, conservation of medicinal plants by local communities and responsible bodies is vital to avoid further loss. Moreover, phytochemical and pharmacological investigation is recommended with due consideration to frequently used medicinal plants.

Data Availability
The data used in this study is available from the corresponding author upon request.

Conflicts of Interest
The authors declare that they have no conflicts of interest.