Ethnobotanical study of medicinal plants in the Hawassa Zuria District, Sidama zone, Southern Ethiopia

Description of the study area

The Hawassa Zuria district (07° 01′ 54″ to 07° 50′ 36″ N and 38° 15′ 39″ to 38° 25′ 43″ E) is located 290 km from Addis Ababa in the Sidama zone, Southern Nations, Nationalities, and Peoples’ Region (SNNPR) of Ethiopia, bordering Tula town in the east, Lake Hawassa in the north, the Oromia region in the west, and the Boricha district to the south (Fig. 1). This district has a total population of 124,472, of whom 62,774 are men and 61,698 women [7]. The altitudinal range is 1700 m to 1850 m.a.s.l. The annual mean maximum and minimum temperatures are 30 °C and 17 °C, respectively, and the mean annual rainfall is 1015 mm. The size of the district is 22,643 ha and the dry zone accounts for 75% [29] and consists of 23 kebeles (farmers’ associations).

Fig. 1

Map of Hawassa Zuria district, Sidama zone, Southern Ethiopia. Study area kebeles: (1) Dore Bafeno, (2) Galo Argiso, (3) Jara Damowa, (4) Jaro Dado, (5) Lebu Korem, (6) Jara Hirnesa, (7) Tenkaka Umbulo, (8) Doyo Otilcho, (9) Jara Gelalcha, (10) Jara Qerara

The study was conducted in ten kebeles in the Hawassa Zuria district, SNNPR, from January to February of 2018. The ten kebeles selected were ‘Dore Bafeno,’ ‘Galo Argiso,’ ‘Jara Damowa,’ ‘Jara Dado,’ ‘Tenkaka Unbulo,’ ‘Lebu Korem,’ ‘Jara Qerara,’ ‘Jara Hirnesa,’ ‘Jara Gelalcha,’ and ‘Doyo Otilcho’ (Fig. 1). The criteria for the selection of these study sites were the availability of traditional healers and recommendations from older people and local authorities.

Sampling informants

In total, 150 informants (118 men and 32 women) were selected among the Sidama people in the Hawassa Zuria district based on recommendations of elders, village administrators, and local guides. The ages of the informants were between 20 to 93 years. Snowball sampling was used and appointments were made prior to visiting the key informants.

Ethnobotanical data collection

The ethnobotanical study was collected from January to February of 2018. The techniques employed for data collection were group discussions, field observations, guided field walks, and a semi-structured questionnaire (see Additional file 1: Table S1). A semi-structured questionnaire that focused on determining the socio-economic status of the participants was prepared, and both informants and key informants were asked to present their knowledge about the medicinal plants they used to treat different ailments, the plant parts used, the method of preparation for the remedy, and details of the administration method and uses other than medicinal.

General and key informants were interviewed in the Sidama language with the assistance of a native translator.

Plant specimen collection and identification

Sample specimens of the plants cited for their medicinal use were collected, numbered, pressed, and dried for identification. Preliminary plant identification was performed in the field and results were reconfirmed at the National Herbarium of AAU. Identification of plant specimens was done using the Flora of Ethiopia and Eritrea book and also by comparisons with authenticated specimens with the help of experts at the National Herbarium of Addis Ababa University. Voucher specimens were deposited in the National Herbarium of Addis Ababa University.

Data analysis

Descriptive statistical methods, in this case percentage and frequency, were used to analyze and summarize the data on medicinal plants as well as their uses and associated knowledge, with MS Excel. According to disease categories in earlier work [30] and with some modification, the ailments were categorized into 14 categories based on the usage reports mentioned by the informants in the study area. The collected data were analyzed through the informant consensus factor and fidelity level [31, 32].

Quantitative analysis

The informant consensus factor was calculated using the formula ICF = nur-nt/nur-1, where ICF denotes the informant consensus factor, nur is number of use citations, and nt is the number of species used [33]. ICF values range from 0.00 to 1.00. High ICF values are obtained when only one or a few plant species are reported to be used by a high proportion of informants to treat a particular ailment. Low ICF values indicate that informants disagree over which plant to use. High ICF values can thus be used to find particularly important species in searches of bioactive compounds [34]. Fidelity level was used to analyze plant use with the formula FL = Np/N*100, where Np denotes number of informants who reported the use of the plant to treat a particular disease and N represents the number of informants who used the plants as a medicine [33].

Jaccard’s coefficient of similarity (JCS) was calculated to evaluate medicinal plant species compositions and degrees of similarity among different areas. Similarity values were calculated between the present study area (Hawassa Zuria district) and other areas in similar agroecological zones which had been studied by other researchers in different parts of Ethiopia. The formula used to calculate the JCS is JCS = c/(a + b + c), where JCS is Jaccard’s coefficient of similarity, a is the number of species found in habitat A, b is the number of species found only in habitat B, and c is the number of common species found in habitats A and B [35].

Preference ranking

Key informants were selected to assess the degree of effectiveness of medicinal plants when used to treat human and livestock diseases following Martin [36]. The medicinal plants believed to be most effective to treat an illness were given the highest value (5), while the least effective received the lowest values (1). The value of each species was summed and the rank for each species was determined based on the total score. This helped to indicate the most effective medicinal plants used by the community to treat diseases.

Direct matrix ranking

By following Cotton [37], direct matrix ranking was conducted in order to compare multipurpose medicinal plants commonly reported by informants. Based on the relative benefits obtained from each plant, eight multipurpose plant species were selected and seven use diversities of these plants were listed. Three key informants were chosen to assign use values for each attribute (5 = best, 4 = very good, 3 = good, 2 = less, 1 = least used). The use categories include food, fodder, house construction, farming utensils, material cleaning, cultural value, and firewood. Based on data obtained from the informants, the average use diversity value for each species was determined and the values for each species were finally summed and ranked.

Medicinal plants in the Hawassa Zuria district

A total of 105 medicinal plant species belonging to 95 genera and 52 families were recorded in the study area (Table 1). Fabaceae (11 species) was represented by the highest number of plant species, followed by Lamiaceae (seven species), Cucurbitaceae (six species), Euphorbiaceae (five species), Solanaceae and Asteraceae (four species each) (Fig. 2). Anacardiaceae, Boraginaceae, Capparidiaceae, Malvaceae, Myrtaceae Poaceae, and Rutaceae were represented by three species each, whereas Celastraceae, Meliaceae, Moraceae, Musaceae, Rosaceae, Rubiaceae, and Verbenaceae were represented by two species each. Each of the remaining families was represented by one species (see Additional file 2: Table S2).

Fig. 2

Distribution of medicinal plant species across the different families

Endemic medicinal plant species

Among the documented medicinal plants in the study area, 71% of species were indigenous and 20% were introduced to Ethiopia. Five endemic plant species were recorded, representing 5% of all medicinal plant species in this study (Table 2).

Therapeutic indications

In the present study, 48% the reported medicinal plants were used only to treat human diseases, 45% were used for human and livestock ailments, and 8% were used only for livestock diseases. It was also found that 16% of the species were indicated to treat gastrointestinal ailments, followed by general and unspecified diseases at 14%, dermatological infections/diseases at 10%, and skeletomuscular system disorders, respiratory system diseases, and insect and ectoparasites diseases at 9% each (Fig. 3).

Fig. 3

Main therapeutic indications of diseases

Habits of growth and parts of plants used

Medicinal plants were mainly harvested fresh (66%), whereas the remaining (34%) were used in a dry form. The results showed that medicinal plants used to treat human and livestock ailments consisted of 35 herbs (34%), 34 trees (33%), 29 shrubs (28%), and six climbers (6%) species. Thus, the most common form of medicinal plant in the study area was a herb, followed by trees and shrubs (Fig. 4).

Fig. 4

Growth forms of the reported plant species

The informants of the study area reported that leaves (56%) were the dominant plant part used to prepare remedies, followed by fruits (15%), roots (12%), bark (5%), seeds, stems and bulbs (4%), shoot tips (2%), and flowers and latex (1%) (Fig. 5).

Fig. 5

Plant parts used in the study area

Medicinal plants used for treatment of human health problems

A total of 50 species belonging to 46 genera and 30 families were recorded to treat human diseases. In the study area, 34 human ailments were identified to be treated by many medicinal plants (see Additional file 3: Table S3.). A single plant can treat a number of human ailments, and a single ailment can be treated by a number of plants. For instance, stomachache is a major disease and can be treated by 41 medicinal plants (Table 3).

Medicinal plants used to treat livestock aliments

A total of eight species belonging to seven genera and seven families were recorded as being used to treat livestock diseases. In this study, livestock diseases are treated with fewer plants compared to those used to treat human diseases. A total of 13 livestock diseases were treated by eight species of plants (Table 4). The most common diseases which affect animals in the study area were wounds, ticks, placenta delay, and swelling.

Medicinal plants used to treat both human and livestock health ailments

A total of 47 species belonging to 46 genera and 32 families were recorded as being used to treat both human and livestock diseases. In the Hawassa Zuria district, 22 types of human and livestock ailments were recorded (Table 5) and 47 medicinal plants were identified to treat both human and livestock ailments.

Sociodemographic characteristics of the respondents

One hundred fifty informants participated in the ethnobotanical survey of the Hawassa Zuria district. Of these, 118 (78.6%) were men, 32 (21.4%) were women, and 30 were key informants. The majority of respondents were more than 50 years old (42.4%) and 56 informants ranged in age between 36 and 50 years (37.4%). Thirty informants were between 20 and 35 years old (20%). The majority of informants had attended elementary school (48%) (Table 6). Seventy-six percent were farmers and 83% were followers of the protestant religion (see Additional file 4: Table S4).

Medicinal plant knowledge with respect to gender, age, and education

Significantly more (p < 0.05) medicinal plants were known by men than by women, by informants in the age group above 50 years compared to those aged between 20 and 35 years and between 36 and 50 years, among literate informants who attended elementary school than by illiterate informants (Table 7).

Jaccard’s coefficient of similarity

The highest Jaccard’s coefficient of similarity in the composition of medicinal plants was found between the study area and Wondo Genet district (15.5%), whereas the degree of similarity was lower with Mana Angetu (8.96%) (Table 8). Possible reasons for the similarity and differences between the study area and other areas may be the agroecological climatic conditions in the region.

Informant consensus factor

The diseases in the study area were grouped into 14 disease categories based on the usage reports by the informants and the resemblance to the disease category. A total of 61 diseases treated by 105 plant species were documented in the study area. Among the disease categories, the categories with the highest informant consensus factor (ICF) values were insects and ectoparasites (0.95), followed by fever (0.91) and sensory neuron diseases (0.86) (Table 9). The medicinal plants that had higher ICF values were presumed to be more common and effective when used to treat a certain disease. However, fetal disease and the pregnancy-related category had a lower ICF value (0.59). Lower ICF values indicated that the informants disagreed on the taxa to be used as a treatment within the disease category. The highest plant use citation was found for gastrointestinal issues (418), followed by sensory neuron diseases (297) and then general and unspecified diseases (241).

Fidelity level

Eucalyptus globules (100%) and Ensete ventricosum (87.27%) were the two plant species with the highest fidelity levels. These were in the gastrointestinal ailment and fetal disease pregnancy-related categories, respectively, and were followed by Moringa stenopetala (81.69%) and Catha edulis (74%) correspondingly within the cardiovascular system disease and genito-urinary ailments categories. A higher fidelity level (FL) can imply that a particular plant purpose is preferred if informants mentioned it often. In contrast, the lowest fidelity level value was assigned to Dodonaea viscosa subsp. angustifolia (29.17%), followed by Croton macrostachyus (31.18%) from insects and ectoparasites and the skeletomuscular system disorders category, respectively. A lower fidelity level implies that a particular plant purpose is not preferred (Table 10).

Preference ranking

Ten key informants were asked to compare seven medicinal plants based on their knowledge of medicinal plants for the treatment of stomach problems by assigning a score of five for the most effective medicinal plants and one for the least effective medicinal plants. Eucalyptus globulus Labill. was ranked as the most preferable medicinal plant for stomachache, followed by Nigella sativa L. (Table 11).

The output of the preference ranking indicated that Tragia brevipes Pax., Ricinus communis L., and Acacia etbaica Schweinf. were the most preferable medicinal plants for treating wound diseases in livestock (Table 12).

According to the results, cancer was the most common disease challenging both humans and livestock in the Hawassa Zuria district. The preference ranking results showed that Cucumis dipsaceus Ehrenb. ex Spach was the medicinal plant preferred as a treatment for cancer both in human and livestock, followed by Rotheca myricoides (Hochst.) Steane & Mabb. and Euphorbia abyssinica J.F.Gmel. (Table 13).

Other uses of medicinal plants in the study area

The majority of respondents reported that the medicinal plants can also be used as food, fodder, and as house construction materials in the study area (see Additional file 5: Table S5). In this case, 33% of the medicinal plant species were reported to be used for food, the highest rate, followed by fodder (28%), and house construction materials (26%) (Fig. 8).

Fig. 8

Use categories and number of plant species

Direct matrix ranking

Key informants evaluated the functionality of multifunctional medicinal plants to the local people and indicated their scores for each medicinal plant (on a scale of 1 to 5). Eight medicinal plants were selected to be evaluated in seven usage categories. The output of the direct matrix analysis found Ensete ventricosum to be the preferred medicinal plant used for various purposes by the local people, followed by Olea welwitschii (Knobl.) Gilg & G. Schellenb., and Dodonaea viscose subsp. angustifolia (Table 14).

Threats to medicinal plants

Numerous factors are considered as threats to the medicinal plants in the study area. According to the responses from the key informants, the major threat to medicinal plants was agricultural expansion (30%) followed by firewood collection (23%) and environmental degradation (20%) (Fig. 9).

Fig. 9

Threats to medicinal plants in the study area

Comparison with previous ethnobotanical studies

Moringa stenopetala (Baker f.) Cufod. was the most frequently used plant for amoeba, hypertension, and malaria treatment in the present study and similarly Asnake et al. [23] reported this plant use for malaria in Boricha district. Tamiru and Asalfew [41] reported for inflammation, wound, diabetes, eye disease, and headache treatment in Mirab Badwacho district. Tilahun et al. [56] reported this plant use mainly as vegetable for food. In Wonago district, this plant used for vomiting [3].

Nicotiana tabacum L. was the most frequently used plant and reported to be used against Snakebite, toothache, and headache in our study. Similarly, Yigezu et al. [57] and Tamiru and Asalfew [41] mentioned this plant use for snake bite and toothache. This plant in five reports of study in Ethiopia stated its wide spread use in treatment of black leg, tick infestation, wound, leech, diarrhea, and gonorrhea [41, 42, 51, 57, 58].

Tragia brevipes Pax was used for evil eye, cancer, anthrax, and diarrhea in the present study, whereas it is used for babesiosis and abdominal pain in other study areas [26, 58]. Cucumis dipsaceus was documented for cough, cancer, and black leg treatment in the current study. Asnake et al. [23] and Sintayehu [27] reported this plant use for malaria, intestinal parasite, pneumonia, gonorrhea, and stomach problem.

Croton macrostachyus reported in the present study for the treatment of bone fracture, tuberculosis, gastritis, and goiter. Gonfa et al. [24] reported this plant only for tuberculosis purpose in Dale district. Yigezu et al. [57] found out the use of this plant for treatment of bloat in cattle. However, this plant was reported for the treatment of stomachache in Mirab Badwacho district [41], in Dale district [24], and Benna tsemay district [13]. Mirutse [46] and Melesse [44] mentioned the use of this plant for the treatment of snakebite. This plant was reported for the treatment of malaria in Boricha [23] and Amaro district [51]. Other studies reported this plant use for the treatment of wound [24, 51, 58].

Allium sativum L. was the most frequently used plant for abdominal pain, malaria, and mitch in the present study. This findings also agreed with the study conducted in Wonago district [3], Mirab Badwacho [41], Kembata [44], and Amaro district [12]. The plant product also has been used for other infections in upper respiratory tract [41]. Miruts et al. [52] and Mesfin et al. [12] reported this plant use for headache in Sheko and Amaro district respectively.

Aloe adigratana Reynolds. was a new Aloe species mentioned for the first time in the present study. It was reported in the present study for the treatment of skin disease and gastritis. The previous studies conducted in other area mentioned the use of Aloe spp. for cold and malaria treatment in Kembata [44] and Boricha district [23]. Rotheca myricoides (Hochst.) Steane & Mabb. also known by the synonym Clerodendrum myricoides was reported to be used for mitch, cancer, and toothache treatment in the present study. Similarly, Yibrah [58] reported the use of this plant for teeth pain in Kochore district. Asnake et al. [23] reported the plant to be used against malaria in Boricha district.

Ensete ventricosum reported in the present study for placenta delay and weight gain in livestock and human. Unsimilarly, Reta [25], Giday et al. [52], and Andarge et al. [59] reported this plant for diarrhea, bone fracture, and tumor respectively. Olea welwitschii was commonly reported to be used for eye disease, headache, and gastritis in this study. Previous studies in Wayu Tuka and Tulu Korma district mentioned this plant for stomachache and gonorrhea disease treatment [60, 61].

Ricinus communis reported in the present study for the treatment of coughing, constipation, and swelling. However, Kassa [61] and Amenu [62] mentioned this plant for anthrax treatment in Tulu Korma and Ejaji district. Other studies in south western Ethiopia stated its use in treatment of rabies, sudden illness, blotting, wound, and mastitis [20, 60–63]. Eucalyptus globulus was the most frequently used plant and reported to be used for headache, mitch, stomachache, coughing, and common cold in our study. Similarly, it has been reported for common cold and influenza in Wayu Tuka district [60], Gimbi [64], and Dawuro zone [59]. Regassa [25] reported this plant use for malaria, typhoid, Ascarsis, and acute sickness in Hawassa city.

Nigella sativa L. was used for stomachache, gastritis, and headache in the present study. Similarly, this plant was reported for stomachache and headache in Hawassa city [25]. Others reported it for asthma, leprosy, and strepto thricosis in Wayu Tuka district [60] and Nekemet [65]. Acacia etbaica reported in the present study for the treatment of wound, cancer, and swelling. Similarly, Dinkissa et al. [66] mentioned this plant for wound treatment in Awash National park. However, Eneyew et al. [67] mentioned this plant for snakebite and evileye treatment in Fitche district.

Euphorbia abyssinica was reported for swelling, gastritis, malaria, and headache treatment in the current study. Similarly Abera [64] reported it for gastrointestinal disease in Ghimbi district. Ascaris, gonorrhea, warts, rabies, and venereal disease were the diseases mentioned on previous studies [64, 67]. Dodonaea viscose subsp. angustifolia was the most frequently used plant for evil eye and diarrhea in the present study. This findings disagree with the study conducted in other areas which stated the plant use for bone fracture, herpes, liver ailments wound, and acute sickness [25, 61, 62, 65].

According to the comparison of our findings with others ethnobotanical study in Ethiopia, novel plant uses of some medicinal plants were documented. Aloe adigratana, Tragia brevipes, Cucumis dipsaceus, Rotheca myricoides, Ricinus communis, and Dodonaea viscose subsp. angustifolia was completely novel use in our study area and never ever reported in other similar investigations. The pharmacological activity of these plants are novel findings that only known in this area for such medicinal purpose.