An ethnobotanical study of medicinal plants used by the Tengger tribe in Ngadisari village, Indonesia

The people of Tengger, Indonesia have used plants as traditional medicine for a long time. However, this local knowledge has not been well documented until recently. Our study aims to understand the utilization of plants in traditional medicine by the people of Tengger, who inhabit the Ngadisari village, Sukapura District, Probolinggo Regency, Indonesia. We conducted semi-structured and structured interviews with a total of 52 informants that represented 10% of the total family units in the village. The parameters observed in this study include species use value (SUV), family use value (FUV), plant part use (PPU), and the relative frequency of citation that was calculated based on fidelity level (FL). We successfully identified 30 species belonging to 28 genera and 20 families that have been used as a traditional medicine to treat 20 diseases. We clustered all the diseases into seven distinct categories. Among the recorded plant families, Poaceae and Zingiberaceae were the most abundant. Plant species within those families were used to treat internal medical diseases, respiratory-nose, ear, oral/dental, and throat problems. The plant species with the highest SUV was Foeniculum vulgare Mill. (1.01), whereas the Aloaceae family (0.86) had the highest FUV. Acorus calamus L. (80%) had the highest FL percentage. The leaves were identified as the most used plant part and decoction was the dominant mode of a medicinal preparation. Out of the plants and their uses documented in our study, 26.7% of the medicinal plants and 71.8% of the uses were novel. In conclusion, the diversity of medicinal plant uses in the Ngadisari village could contribute to the development of new plant-based drugs and improve the collective revenue of the local society.


Introduction
The interaction between humans and plants has been long described as one of the factors influencing human civilization, especially in medicinal fields [1]. Documentation of the medicinal use of plants through ethnobotanical studies enables the development of contemporary drugs and treatments as well as for plant conservation [2,3]. Many ethnobotanical studies around PLOS ONE PLOS ONE | https://doi.org/10.1371/journal.pone.0235886 July 13, 2020 1 / 16 a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 mode of preparation, or method of processing the plants. All of the head family units were males since norms, values, and local wisdom are based on patriarchal culture [17]. The age of the informants ranged from 25 to more than 45 years, where four were between the ages of 25-30, sixteen were ranging from 31-35, eighteen were between 36-40, nine were ranging from 41-45, and five informants were older than 45 years. The interview activities were carried out in their entirety using a questionnaire. Informant selection was based on the Snowball Sampling technique, by determining the key person. A key-person is one who possesses strong power within society. The subsequent informants are determined by the direction of the previous respondents.

Taxonomical identification and herbarium
Taxonomical identification was conducted to verify the samples that were raised during the interviews. An herbarium was also prepared to obtain dry specimens supporting the taxonomical identification. However, the herbarium method was used only for unknown species. Photo documentation and herbarium of medicinal plants were then identified by Christin Risbandini under the laboratory of plant bioscience and biotechnology, Institut Teknologi Sepuluh Nopember, Indonesia using key dichotomy and some references [18,19].

Data analysis
Fidelity Level (FL). The relative frequency of citation was calculated using the fidelity level (FL) formula according to Friedman et al. [20] and Ouedraogo et al. [21]. FL is the percentage of informants who claim to use certain plant species for particular healing processes. This reflects the preference of people for a specific plant species in a particular medicinal treatment. It was calculated using the following equation: Where Np is the number of informants who mentioned or claimed the use of plant species for a particular healing process/medicinal treatment. N is the total number of informants who cited the plant species for various kinds of medicinal treatment.
Species Use Value (SUV). SUV signifies the value of a medicinal plant species used by the people from Ngadisari village. It is calculated as the sum of the informant species use values (UV is ) for a particular medicinal species divided by the total number of informants (N i ). The SUV was calculated according to Hoffman and Gallaher [22] as follows: Family Use Value (FUV). FUV was calculated as described by Phillips and Gentry [23], signifying the use value of a given plant family that is used as medicine by the people from Ngadisari village. The calculation follows the below equation: Where ∑UV s represents the sum of the use values for all species belonging to a particular family divided by the total number of species in the same family.
Plant Part Value (PPV). The plant part value is presented as the percentage of utilized parts of plants (stem, leaves, root, fruit, bark, and flower) that are used as medicinal bioresources. The PPV is calculated according to Gomez-Beloz [24] as follows: Where ∑RU (plant part) and ∑RU represent the sum of the cited plant parts and the total number of cited uses for a given plant, respectively.
The highest number of species in one category was found in the category of IM with 12 species, followed by nine species in RT and six species in DD (Table 1). We also observed that five species found in this study were used to treat more than one disease in distinct categories. For instance, fennel, locally named Adas (Foeniculum vulgare Mill.) has been used to treat urticaria/hives (DD), cough (RT), and to overcome motion sickness (OT). Betelvine (Piper betle L.) has also been used for more than one disease including leucorrhoea (UGP), hives or urticaria (DD), and worm disease (GI). This demonstrated that the use value of these species is quite high compared with that of other medicinal plants [22]. Previous studies also demonstrated that fennel is frequently used as medicinal plants in Indonesia [12,25] and is abundantly present in this region [9]. Our data showed that F. vulgare is categorized as a plant used to treat dermatological problems (DO). People of Tengger inhabiting Ngadisari village use F. vulgare to treat urticaria, hives, or itching. Our results are also in accordance with other studies that revealed F. vulgare as a traditional medicine for people suffering from itching or other dermatitis problems [26].  [27] and Salehi et al. [28] reported the use of Aloe vera to treat hair problems. Meanwhile, the use of Acorus calamus L. to treat fever has been reported by Rajput et al. [29]. Also, A. graveolens and A. fistulosum L. have been used by traditional Chinese and Indonesian people to reduce blood pressure and cough, respectively [30,31]. Finally, nine species were reported to have low SUV (0.01) in the present study (Fig 2). High or low SUV may be due to extensive or minimum ethnobotanical uses of the reported species, respectively. Similar results were also reported by Hussain et al. [32], where the highest SUV represents the most exploited medicinal plants used to treat a specific ailment.

Species and family use value
In total, 30 medicinal plant species have been recorded in our study. All belong to 20 different families, with Poaceae and Zingiberaceae being dominant in the study area (each consisting of four species) followed by Apiaceae (three species). The remaining families were represented by one or two species (Table 2). Poaceae and Zingiberaceae were the most representative medicinal plant families in our study. This finding might be due to the high accessibility of these species in that region. This further supports that dominant plant families and species are commonly used by local people for disease treatment [32]. Moreover, most of the species within both families are cultivated by people of Tengger in the Ngadisari village. The occurrence of dominant plant species and families in the study area is also related to favorable climate and environmental conditions [33,34]. As a result of the abundance, these species are commonly used as a basic ingredient of Jamu-an Indonesian traditional medicine [35]. Sharifi-Rad et al. [36] also described that plants from the Zingiberaceae family are a potential source of bioactive phytochemical.
The total number of species within a given family has been calculated to obtain their FUV. Our results showed that Aloaceae had a high FUV (0.86), followed by Acoraceae (0.80), Piperaceae (0.69), and Euphorbiaceae (0.65). Other families represented low FUV (< 0.60) ( Table 2). High values of FUV might be because the plant species were cited by a large number of people in the study area. In addition, some reports have described similar results. For example, A. vera or locally named as crocodile's tongues has been frequently used in some regions such as Southern Africa [37], Asia [38], Nigeria [39], and India [40] to treat dry skin, for improving skin integrity, and to decrease the appearance of acne, skin burn, and wrinkles.
A. calamus is also cited by other ethnobotanical studies around the world including China [41], India [42], Nepal [43] to treat fever, diarrhea, bronchitis, tumors, skin diseases, and cough treatment [29]. Reported species from Piperaceae has also highly cited in the previous study [11]. Finally, another high FUV in this study was obtained by Euphorbiaceae with only one species (Jatropha curcas). The Tengger people use this Barbados nut species to treat mouth ulcers and hyperuricemia. Our data supports other studies; for example, Abdelgadir and Staden [44] reported that its latex is used for ailments such as headache, toothache, mouth ulcers, cold, and cough. Abu Bakar et al. [45] also reported that J. curcas is potentially used to treat hyperuricemia.

Fidelity level
According to Imran et al. [46], the fidelity level (FL) is useful to determine the level of species importance in relation to a particular disease. FL shows the percentage of respondents who mention the use of a plant species for the same main purpose. Ouedraogo et al. [21] reported that relative frequency of citation could also be counted based on FL. This is designed to measure species importance for specific purposes. Our results showed that FL of the 30 plant species ranged from 1.92 to 80% (Table 3). A. calamus demonstrated the highest FL for fever (80%), followed by A. graveolens (76.92%) and A. fistulosum (71.15) for treating hypertension and cough, respectively. Based on a previous study, plants with a high percentage of FL are more frequently used as bio-pharmacological resources [47] and should be considered for further conservation program [48] bioassays and phytopharmacological investigation [49,50]. Some species have low percentage of FL (1.92%) related to various diseases (Table 3). Examples include, S. muricatum, Z. zerumbet, C. nardus, C. domestica, P. guajava, G. mangostana, P. foetida, S. alata, K. galanga, C. sativum, Brassica sp. Low fidelity levels might also explain the low abundance of plant species in this region. Furthermore, it might also indicate that there is little information about the use of this medicinal plant among the people of Tengger in the  Ngadisari village. Even though some plants possess low FL, these species should not be abandoned to preserve traditional knowledge of the society in treating some diseases as reported by Chaachouay et al. [51].

Plant part use and mode of preparation
According to Hoffman and Gallaher [22], calculating the use of plant parts (Plant Part Use) is useful to determine the dominant plant parts being used as medicinal ingredients. Plant parts are capable of accumulating diverse and interesting natural compounds. They attract attention because of their ability to act as factories, producing and offering important pharmaceutical potential [52]. Our results showed that leaves were the most predominantly utilized plant parts at 61.5%, while gum, stem bark and bulb represent parts that are infrequently used by people of Ngadisari (Fig 3).
Leaves are the major plant components commonly reported to be used as herbal medicine materials in Indonesia [8,53] and also in other countries [54][55][56]. Leaves are common and favorite parts used for medicinal treatment preparation because of easy handling and sustainability [57,58]. The latter is linked to the survival rate of medicinal plants. Removing the leaves biomass within reasonable limits does not interfere with the plant life, compared to collecting the stem, root, or whole plant, which may risk the plant life [59]. Moreover, many reports have showed that leaves contain diverse plant secondary metabolites [60]. In the present study, no data have been obtained for the use of flowers as medicinal materials. This might offer other perspectives for further investigation. Furthermore, our data have also shown the use of more than one plant part from the same plant species. For instance, J. curcas leaves and stem have been used to treat hyperuricemia and mouth ulcer, respectively.
People from the Ngadisari village use many methods to prepare plant parts before using them as herbal medicine. The decoction is considered the main mode of preparation (40.9%), followed by pounding (15.9%) and burning (13.6%). Meanwhile, eating raw (9.1%) and smearing (6.8%) contribute and of the total mode of preparation in the present study. Other miscellaneous modes of preparations constitute the remaining 13.6% (Fig 4). Some other studies have also mentioned the same results, where the most common method of preparation is decoction [61][62][63]. Simple, easy handling and inexpensive are the major reasons why this mode of preparation is widely used by society [64]. Moreover, other reports also demonstrated that decoction might increase the efficiency of plant extraction and therefore increase its bioactivity [65].
Some plants can be prepared without any processing. For example, leaves of A. graveolens are eaten raw to reducing hypertension symptoms and leaves of A. vulgaris are applied directly by clogging into the nose to stop nosebleeds. All this local knowledge is preserved and applied by the people of Tengger in Ngadisari village. This practice is common in other regions in Indonesia such as in Madura and Bali [5,66].

Conclusions
Our results highlighted the use of medicinal plants by people from the Ngadisari village, Indonesia. A total of 30 medicinal plant species were recorded in the present study. They belong to 20 different families, where Poaceae and Zingiberaceae were the most representative families. A high number of plant species were used for treating internal medical diseases, respiratorynose, ear, oral/dental, and throat problems. Leaves were the most popular plant part used and decoction was the most common method of preparation. These findings indicated potential roles of medicinal plants used in the Ngadisari village. Furthermore, our study characterized the cultural values of the people of the Ngadisari village. The species use, family use values and fidelity levels presented here may be used to further support plant conservation and pharmacological studies for new drug discovery. Out of all the plants we reported, approximately 26.7% were novel medicinal plants. In addition, 71.8% of the plant uses we documented of medicinal species were also novel. Some highly cited species recorded in our study warrant further biochemical analyses to evaluate their bioactive substances. Moreover, in vitro plant tissue culture could also be used as an alternative way to conserve medicinal plants documented in this study. Finally, the information we obtained could enable the local communities to develop, market, and profit from dried herbal products, which then substantially improving the collective revenue of the local society.