An ethnobotanical survey of medicinal plants used in Terai forest of western Nepal

Abstract

Background

Nepal Himalayas have been known as a rich source for valuable medicinal plants since Vedic periods. Present work is the documentation of indigenous knowledge on plant utilization as natural remedy by the inhabitants of terai forest in Western Nepal.

Methods

Study was conducted during 2010–2011 following standard ethnobotanical methods. Data about medicinal uses of plants were collected by questionnaire, personal interview and group discussion with pre identified informants. Voucher specimens were collected with the help of informants, processed into herbarium following standard methods, identified with the help of pertinent floras and taxonomic experts, and submitted in Department of Botany, Butwal Multiple Campus, Tribhuvan University, Nepal for future references.

Results

During the present study 66 medicinal plant species belonging to 37 families and 60 genera has been documented. These plants were used to treat various diseases and ailments grouped under 11 disease categories, with the highest number of species (41) being used for gastro-intestinal disorders, followed by dermatological disorders (34). In the study area the informants’ consensus about usages of medicinal plants ranges from 0.93 to 0.97 with an average value of 0.94. Herbs (53%) were the primary source of medicine, followed by trees (23%). Curcuma longa (84%) and Azadirachta indica (76%) are the most frequently and popularly used medicinal plant species in the study area. Acacia catechu, Bacopa monnieri, Bombax ceiba, Drymaria diandra, Rauvolfia serpentina, and Tribulus terrestris are threatened species which needs to be conserved for future use.

Conclusions

The high degree of consensus among the informants suggests that current use and knowledge are still strong, and thus the preservation of today's knowledge shows good foresight in acting before much has been lost. The connections between plant use and conservation are also important ones, especially as the authors note that neither the local inhabitants nor the government is addressing the potential loss of valuable species in this region.

Background

The Rig-Veda written during 4500 BC to 1600 BC is believed to be the oldest repository of human knowledge about medicinal usages of plants in Indian subcontinent. In Nepal, although such old documentation is still not rediscovered, but the knowledge on plant utilization is believed to be very old. According to WHO [1], about 80% of the world’s population, especially in the rural areas depends on herbal medicine for their healthcare needs. About 90% of the Nepalese people reside in rural areas where access to government health care facilities is lacking [2]. The ethnic people residing in different geographical belts of Nepal depends on wild plants to meet their basic requirements and all the ethnic communities have their own pool of secret ethnomedicinal and ethnopharmacological knowledge about the plants available in their surroundings [2–20], which has been serving rural people with its superiority. Due to changing life style, extreme secrecy of traditional healers and negligence of youngsters, the practice and dependence of ethnic societies in folk medicines is in rapid decline globally, therefore, ethnobotanical exploitation and documentation of indigenous knowledge about the usefulness of such a vast pool of genetic resources is deliberately needed [21–30]. We selected Terai forest of Rupandehi district and adjoining areas for ethnomedicinal investigation because this area is very rich in phytodiversity and tribal population. Besides other usages of plants the practice of oral tradition for healthcare management of human and domesticated animals using herbal medicines is still prevalent among the inhabitants of the area. They have enormous knowledge about medicinal uses of plants and this knowledge is mostly undocumented and transmitted orally from generation to generation. Recently due to unplanned developmental programs, increasing modern healthcare facilities and impact of modern civilization in this area, natural resources as well as traditional knowledge and tribal cultures are depleting rapidly at an alarming rate. Therefore, it is urgent to explore and document this unique and indigenous, traditional knowledge of the tribal community, before it diminishes with the knowledgeable persons. Further, documentation of indigenous and traditional knowledge is very important for future critical studies leading to sustainable utilization of natural resource and to face the challenges of bio-piracy and patenting indigenous and traditional knowledge by others. Besides, to the best of our knowledge no ethnobotanical work has been carried out in this area. Keeping these things in mind present study was proposed to document the ethnomedicinal knowledge in terai forest of western Nepal. Aims of the present study are:

• (A) Identification and documentation of plant species used for the treatment and prevention of various diseases and ailments in the study area.

• (B) Identification of most common and popularly used medicinal plant species for the treatment and prevention of various diseases and ailments in the study area.

• (C) Find out the level of consensus agreement between the informants regarding the uses of particular medicinal plant(s) for the treatment of particular disease category.

Study area

Rupandehi district is situated in the Terai region of western Nepal. It lies between 83⁰27'.955" to 83⁰28'.255" E and 27⁰40'.016" to 27⁰40'.252" N geographical limits in 1360 Km² area at altitudinal variation from 105 to 258 meters. Rupandehi district (Figure 1) is surrounded by hilly districts (Palpa and Arghakhanchi) in North, by Mahrajganj district of Uttar Pradesh (India) in south, by Nawalparasi district in East and by Kapilvastu district in west. It has tropical climate with maximum temperature beyond 40⁰C during summer (May- June) and below 10⁰C during winter (December- January) and annual rainfall is about 1250 mm. Geographically, it is divided into Chure region (14.5%); Bhabar region (0.6%) and Terai region (84.9%). The famous river and rivulets of this district are Tinau, Rohini, Danaw, Pahela, Kanchan, Kothi, Danda, Koili etc. All the rivers flow from north to south. The climatic condition of the study site is tropical type and predominated by Sal forest. The forest area of the district is divided into community forest, religious forest and personal forest [31]. The vegetation of the study is dominated by sal (Shorea robusta) forest along with sissoo (Dalbergia sissoo), saj (Terminalia alata) khayar (Acacia catechu), baheda (Terminalia bellirica), dabdabe (Garuga pinnata), khaniyu (Ficus semicordata), asuro (Justica adhatoda), dhaiyaro (Woodfordia fruticosa), and titepati (Artemesia indica) etc. The main highway Siddhartha Rajmarga runs from the middle part of Shankar Nagar VDC. All the parts of Shankar Nagar VDC and its surrounding areas are interconnected by network of road and are easily accessible for the field visits.

Figure 1

Location map of study site.

Ethnography

The Tharu and the Magar are the main ethnic societies of the study area. They live in association with Chhetri, Brahmin, Thakuri, Gurung, Damai, Kumal, Bote, Majhi, Mushahar, Kami, Newar and others communities. Total population of the district was 7, 08,419 [32] The Tharu tribal community share 10.57% population of the district [31]. They are scattered all along the southern foot hills of the Himalayas. The greater parts of their population resides in Nepal, although they are also scattered in the adjacent Indian district of Champaran, Maharajganj, Gorakhpur, Siddharthnagar, Basti, Balrampur, Baharaich, Shravasti, Lakhimpur-Kheri, and Nainital. There are several endogamous sub groups in the Tharu community, such as Rana, Kathuria, Dangauria, Kochila, and Mech. Tharu people choose plain lands at the jungle side or river side for house construction. They like to settle in the group of their own community members, thus their houses are found dense within a small area. Tharu people used to live in joint family traditionally and it is practiced up to now. In Tharu village, the duty of maintaining good relations among villagers, as well as conducting the village’s affairs, falls on the Mahaton (Village chief). A mahaton is elected by Gardhurryas (Tharu house hold chief) from among themselves. A Mahaton is elected, but once elected; the office becomes hereditary, unless a particular incumbent is considered a misfit. The assembly of Gardhurryas can remove an unsuccessful Mahaton. The role of mahaton in the assembly of Gardhurryas is like that of a chairman and a judge who keep others view in mind, gives the final communal decision. Due to their own believes, judgement policy and living together in close vicinity, they are considered as native Tribal community of Terai region. In Nepal Tharu tribal community is settled in the southern part of the country from the east to west along Indo-Nepal boarder and the adjacent valleys and plains between the Chure hilly regions. The Tharus are famous for their ability to survive in the moist Terai region which is deadly to outsiders due to malaria. They are farmer by occupation and cultivate rice, mustard, corn and lentils but also collect forest products such as wild fruits, vegetables, medicinal plants and material to build their houses, hunt wild animals and fishes [33].

Materials and methods

Field works and collection of data

Field studies were conducted from March 2010 to May 2011. Methods of Martin [34] were followed for the collection of data and voucher specimen during the field study. First of all local administrative officers were consulted with the explanation of aims and objectives of the research for the identification of resource persons (informants). They give advice regarding the people who would be the best sources of information. Researchers meat these peoples and explain the research theme. These informants often suggested other potential informants. In order to insure a sample that includes representatives of whole community, we attempted to interview peoples from variety of age groups, sex, socio-economic and ethnic community (for detail information about gender, age, ethnicity, and occupation of informants please see Table 1). The criteria for the selection of informants for the interview were their reputation in the society regarding their knowledge about herbal medicines and traditional healthcare system. Total 55 informants were identified from Shankar Nagar VDC and surrounding areas. They are reputed knowledgeable persons of the society and the collected data from these informants represent the whole community, because they are knowledgeable healers, villagers, senior citizens, teachers, social workers etc. Prior to survey, a questionnaire was designed and pre-tested with five informants to find out its suitability for present study and modified according to response of informants. The revised questionnaire was used for gathering data about medicinal plants of the study area. Pre informed consent was obtained from the resource persons before interview. Field survey was conducted taking traditional healers as a guide and voucher specimens of cited medicinal plants were collected and their local identity was re-confirmed by other informants. During data collection three visits (in each visit author stay for four days in study area) was conducted and information’s were collected. The information obtained was cross checked with the other informants. The local names, habit, wild/cultivated, availability of medicinal plants, need of conservation and efforts made by inhabitants and traditional medicinal uses of plants were carefully recorded. Finally, group discussion ware made with the healers and local people to know their perception about the use of traditional folk medicines, awareness about the conservation of phytodiversity and indigenous knowledge.

Table 1 Detail of informants interviewed in terai forest of western Nepal

Processing of voucher specimens for herbarium preparation and identification

The voucher specimens were brought to the laboratory and processed for herbarium specimen preparation [34–36] and identified with the help of available floras and other pertinent literatures [8, 11, 23, 37–42] and submitted in department of Botany, Butwal Multiple Campus, Tribhuvan University, Nepal for future references. The botanical identities of collected specimens were confirmed by Dr. M. P. Panthi, and Mr. B. R. Nepali, Taxonomist, Tribhuvan University, Kathmandu, Nepal. Plant names were checked according to International Plant Name Index [43].

Statistical analysis

The data were spreads on Excel sheet to summaries and to identify various proportions like plant families, habit, availability of medicinal plants, plant parts used as medicine, methods of use, frequency of citation and popularly used medicinal plants in the study area. Frequency of citation was calculated by following formula-

$$\text{Frequency of citation(\%)}=\frac{\text{Number of informats who cited the species}}{\text{Total number of informats interviewed}}\times 100$$

(1)

Factor of informants consensus (F_IC) for different ailment categories was calculated for testing homogeneity on the informant's knowledge followed by the method provided by Trotter and Logan and Heinrich et al. as under [44, 45].

$${\text{F}}_{\text{IC=}}\frac{{\text{N}}_{\text{UR}}-{\text{N}}_{\text{TAXA}}}{({\text{N}}_{\text{UR}}-1)}$$

(2)

Where N_{UR =} number of use report in a particular illness category and N_{TAXA =} number of taxa used to treat that particular category by informants.

Result and discussion

Medicinal plants and their uses

Altogether 66 medicinal plants belonging to 37 families and 60 genera were documented from the study area (Table 2). The documented medicinal plants and their ethnomedicinal uses along with common name have been summarized in Table 2. These plant species are used for the treatment and prevention of many ailments and diseases grouped under 11 ailment categories (Table 3). The common sickness for the tribal in the study area are cold, cough, bronchitis, diarrhoea, dysentery, gastritis, headache, backache, cuts, wounds etc. Symptoms of the diseases given by the tribes in local language with their bio-medical terms are given in Table 4. Exact doses and duration of treatment are considered as intellectual property of informants, so as per their request this information is not included in the present paper. Curcuma longa (84%), Azadirachta indica (76%) are the most frequently and popularly used medicinal plant species in the study area.

Table 2 Ethnomedicinal plants of Terai forest in western Nepal and their traditional therapeutic uses

Table 3 Different ailments of study area grouped under different ailment categories with their biomedical terms and factor of informants’ consensus

Table 4 Symptoms of the diseases given by the tribes in terai forest of western Nepal and their equivalent bio-medical terms

Growth forms, plant parts used, method of collection, processing and administration

Out of 66 medicinal plants recorded from study area, highest number of plants belongs to herb (53%) followed by tree, shrubs and climber (Figure 2). Higher uses of herbs for medicinal purposes may be due to easy availability and high effectiveness in the treatment of ailments in comparison to other growth forms. Almost every plant parts are used for the medication either singly or in combination with other plants. Entire plant is used in the majority of cases followed by leaf, root and bark (Figure 3). Plant parts used as medicine is collected by healer themselves from natural resources. Generally fresh parts are collected for use from nature. Various plant parts are collected in different seasons at different stage of maturity and are dried in shade and stored in dry places away from direct sunlight for their use during off season/unavailability. As far as mode of use and administrations are concerned majority of the plants are used in form of juice, followed by decoction (Figure 4). Majority of the medicinal formulations are administrated orally in ailment categories other than dermatological. In dermatological problems plants are administrated topically as well as orally.

Figure 2

Life form of plants used as medicinal plants in Terai forest of western Nepal.

Figure 3

Plant parts used for the management of various healthcare problems in Terai forest of western Nepal.

Figure 4

Processing of medicinal plant/part(s) for crude drug preparation in the study area.

Identification of new claims and reliability of reported claims

Reported uses of various medicinal plants were compared with previously published ethnobotanical literatures in Nepal and adjoining areas of India [2–20, 25, 30] which identifies new medicinal uses of Acacia catechu Acalypha indica, Achyranthes aspera, Aegle marmelos, Aloe vera, Artemisia indica, Bauhinia variegata, Bombax ceiba, Calotropis gigantea, Carica papaya, Citrus limon, Colocasia esculenta Coriandrum sativum, Curcuma amada Cuscuta reflexa, Cynodon dactylon, Dalbergia sissoo, Datura metel, Dendrocalamus hamiltonii, Dioscorea pentaphylla, Ficus benghalensis, Gloriosa superba Ipomoea aquatica, Ipomoea batatas, Ipomoea carnea Jacq. ssp. fistulosa Lagenaria siceraria, Lepidium sativum, Linum usitatissimum, Malva parviflora Mentha spicata, Mimosa pudica, Mucuna pruriens, Phragmites vallatoria Polygonum barbatum Rauvolfia serpentina, Ricinus communis Shorea robusta, Solanum nigrum, Terminalia chebula, and Tribulus terrestris are reported for the first time in Nepal and adjoining areas of India. Some of the medicinal plants reported during the present study were reported for biological activities and bioactive constituents responsible for their therapeutic properties [7, 17, 46–50] which justify and validate the usages of these species for medicinal purposes in the study area.

Consensus of agreement about uses of medicinal plants among informants

To gain credibility, scientific studies that utilize traditional knowledge must be reliable. In ethnobotanical studies, consensus analysis provides a measure of reliability for any given claim providing reliable evidence. The product of F_IC ranges from 0 to 1. High value of F_IC indicates the agreement of selection of taxa between informants, whereas a low value indicates disagreement [51]. Recently consensus analysis has been used as an important tool for the analysis of ethnobotanical data [19, 22, 51–58]. In the study area the informants’ consensus about usages of medicinal plants ranges from 0.93 to 0.97 with an average value of 0.94 (Table 3), which shows high level of agreements among the informants. The high level of consensus among the informants about the usages of medicinal plants for the treatment and prevention of various diseases and ailments prevalent in the study area suggests that the ethnomedicinal uses of plants are currently in practice in the study area.

Availability of medicinal plants in terai forest, conservation efforts and needs

As for as availability of medicinal plants is concerned 39% medicinal plants are cultivated for food, fruit, spices and trade; thus are easily available for medicinal purposes. Majority of the 61% wild medicinal plant species are available without difficulty in the study area except Acacia catechu, Bacopa monnieri, Bombax ceiba, Drymaria diandra, Rauvolfia serpentina and Tribulus terrestris which are available with difficulty and needs to be conserved for future use. Unfortunately, neither local inhabitants nor Government is making serious efforts for conservation of medicinal plants in the study area. Unsustainable collection of generative and vegetative parts of medicinal plants from natural resources reduces their population as well as decrease multiplication and regenerative power. There is an urgent need to create awareness among the inhabitants of the study area about sustainable collection, conservation, domestication, small scale (home garden for personal use) as well as large scale (for trade) cultivation of medicinal plants. This will also improve the socio-economic condition of the inhabitants as well as reduce pressure on natural resources.

Knowledge about traditional healing system and its transfer from one generation to other

Bhagirathi Tharu, Mandali Tharu and Khadanand Poudyal are the main expert from the study area. These experts are working in this field since more than 30 years. Though there is a sub health post with less equipped facility in Shankar Nagar VDC and the modern hospital facilities are available in Butwal municipality which is near about 10 km far from Shankar Nagar VDC. The tribal people of the study area prefer traditional medicinal practice to the modern medicinal system because they know more about the medicinal plants which are easily available in their local area and herbal formulations are cooperatively cheaper and free from side effects. The tribal communities of the study area are not exception to the present stream of modernization and the traditional medicinal practice seems to be disappearing among the tribal communities of the study area. During present study it was found that the knowledge about utilization of medicinal plant species is generally accumulated by observation and experiences and transferred to the next generation by words of mouth. Our finding was similar to findings in other parts of India and abroad [24–30]. As indigenous knowledge on usages of medicinal plants is transmitted without any systematic process, and younger generations of the tribes are not interested in traditional healing system because it has no/very little scope for money, so they engage themselves in other occupations. Thus, it is certain that such knowledge is at the risk of disappearance in the future [21].

Conclusion

Present study revealed that the local traditional healers of Rupandehi district, western Nepal are rich in ethnomedicinal knowledge and majority of people rely on plant based remedies for common health problems like headache, body ache, constipation, indigestion, cold, fever, diarrhea, dysentery, boils, wounds, skin diseases, urinary troubles, fractures, round worms, etc. The survey also revealed that all the traditional healers have strong faith on ethnomedicines although they were less conscious about the documentation and preservation of ethno medicinal folklore and medicinal plants. The group discussion and personal interviews show that youngsters of both Tharu and migrant society are less aware about the use of ethnomedicines; our findings are similar to reports from India [58]. On the other hand, traditional healers who are the main repository of ethno medicinal knowledge claim extreme secrecy over their ethnomedicinal knowledge. The traditional healers have strong believe that if they disclose the secrecy about the medicinal properties of particular plant all the medicinal potentialities of the plant will be lost and the remedy will not work properly.