Traditional Uses of Medicinal Plants in Polonnaruwa District in North Central Province of Sri Lanka

Sri Lanka harbors over 3000 plant species, and most of these plants have been of immense importance in the traditional systems of medicine in the country. Although there is a rich reserve of indigenous knowledge on medicinal plants, in-depth studies have not been pursued yet to compile the ethnoflora with traditional medicinal applications for the scientific community. Thus, as a continuation of our ethnobotanical inventory work in different regions in the country, the present study was carried out in one of the administrative districts in the North Central area of Sri Lanka known as Polonnaruwa district. The information on the significance of medicinal plants as curative and preventive agents of diseases was collected through semistructured and open-ended interviews from 284 volunteers who were randomly recruited for the study. Ethnobotanical data were analyzed using relative frequency of citation (RFC), family importance value (FIV), and use value (UV). Out of the total participants, 53.7% claimed the use of herbal remedies. A total of 64 medicinal plants belonging to 42 plant families were recorded, out of which Coriandrum sativum L. (RFC = 0.163) was the most cited species. Out of the 42 plant families recorded, the FIV was highest in Zingiberaceae. Coscinium fenestratum (Goetgh.) Colebr. was found as the plant with the highest use value. Furthermore, the majority of the nonusers of the herbal remedies were willing to adopt herbal products upon the scientific validation of their therapeutic potential. This study revealed that the indigenous herbal remedies are still popular among the local communities in the study area.


Introduction
Medicinal plants have been used since time immemorial in both developing and developed countries; for example, plants were considered as the material basis of traditional Chinese medicine (TCM) as well as many other ethnic medicine traditions in China [1], while the utilization of medicinal plants as a fundamental component of the African traditional health-care system is believed as the oldest and the most assorted of all therapeutic systems [2]. Similarly, the Indian subcontinent is considered as a vast repository of medicinal plants that have been used in indigenous medical treatments, and even in the present era of modern medicine, traditional health-care systems based on plants and plant-derived products are therapeutically employed on the Indian subcontinent [3]. In the Sri Lankan context, indigenous systems of medicine are widely popular among large segments of the Sri Lankan population despite the influx of modern Western medicine. In general, the traditional systems of medicine available in the country are of four types, namely, Ayurveda, Siddha, Unani, and Deshiya Chikitsa. Plants and plant-based formulations are considered as essential components of the Ayurveda and Deshiya Chikitsa systems [4]. Among the native flora of Sri Lanka, more than 1400 plants are employed for medicinal purposes [5]. Considering the ethnobotanical data in other developing countries in the world, particularly in the neighboring country (India) [6], we could speculate that herbal preparations are more popular among the rural communities in Sri Lanka as well. Hence, a rich reserve of indigenous knowledge of herbal remedies for various ailments is expected to have accumulated especially in the rural areas of the country. e documentation of Sri Lankan medicinal plants to the scientific community was initiated during the colonial period of the country, specially with the descriptions of plant specimens collected by Paul Hermann in the 1670s and also with Icones Plantarum Malabaricarum (1694-1718) [7,8]. Although these sources represent a rich source of ethnobotanical knowledge from colonial Ceylon, only a handful of ethnobotanical studies have been conducted over the recent years to document the traditional knowledge on medicinal values of plant species used in indigenous medicine [9,10]. In addition, the book series written by Jayaweera in 1982 on "Medicinal plants (indigenous and exotic) used in Ceylon" [11] are still popular among scientists who are working on medicinal plants and their bioactivities; however, the scientific validation of these traditional claims is still at its infancy. us, as a continuation of our ethnobotanical inventory work in different administrative areas in Sri Lanka, the present study was undertaken to assess the significance and contribution of medicinal plants/herbal therapeutics to the day-to-day life of the inhabitants of Polonnaruwa district in the North Central region in Sri Lanka.
As evident from the ethnobotanical studies conducted in other South Asian countries as well as in Africa, the rural communities exploit plants that are easily available in their surroundings for food and medicaments [12][13][14]. For example, a recent study conducted in Northern Pakistan revealed that the local communities have a rich accessibility of medicinal plants; thus, they opt herbal remedies as lowcost health care for respiratory disorders [15]. Moreover, in the case of herbal therapeutics, people are generally aware about the harmful effects of synthetic medicines, thus realize the importance of a more natural way of life [10]. Moreover, the factors like low financial conditions and unavailability of modern health-care facilities would also limit the access of rural people to synthetic medicines [16]. Hence, the study area for this research has a high potential for utilization and consumption of medicinal plants due to the wide availability of valuable medicinal plants that are unique to the dry zone of Sri Lanka, as well as the presence of rural agricultural communities. Considering all these factors, we hypothesized that the inhabitants in the study area for this research widely utilize medicinal plants as easy and reliable remedies for common disease conditions.

Study Area.
Polonnaruwa district is located in the North Central Province of Sri Lanka (Figure 1, Supplementary 1) and has an area of 3,293 km 2 . e district is divided into seven divisional secretariat divisions, which are further subdivided into 295 "Grama Niladhari" divisions. ere are 637 villages, and the total population of the district is reported as 403,335. e majority of the people in the district are engaged in agriculture and animal husbandry. e forest coverage, including the grasslands and marshy lands, is estimated as 346,638.2 ha [17]. Twelve government hospitals located within the district provide modern health-care facilities, while 16 Ayurvedic hospitals and a large number of traditional healers within the local communities are responsible for the provision of traditional health-care system.

Ethnobotanical Field Survey and Data Collection.
Medicinal plant use was documented in all seven divisional secretariat areas (i.e., Dimbulagala, Elahera, Hingurakgoda, Lankapura, Medirigiriya, amankaduwa, Welikanda; see Supplementary 1) in Polonnaruwa district. is survey was carried out from August 2015 to March 2018, and the data were collected from 284 volunteers from the general population of the district who were aged above 30 years, following the method described by Napagoda et al. [10]. In brief, the participants were selected randomly from a list of households in each divisional secretariat area, and visits were made to each of those households for data collection. Informed consent was obtained from each participant in writing prior to the study. A questionnaire was used to collect the information on local name of the plants, source, part(s) used, method of traditional preparation, and some demographic information of the informants such as age, gender, and educational background (Supplementary 2). e ethical approval was obtained from the ethical review committee, Faculty of Medicine, University of Ruhuna, Sri Lanka. SPSS version 20 was used to recode the collected data.

Plant Specimen Collection and Preservation.
Plant species used as herbal remedies were collected, dried, preserved, and mounted on herbarium sheets. e plant materials were identified by one of the authors (MTN), who is a botanist. Botanical names and families were verified using book series titled "Revised Handbook to the Flora of Ceylon" [18] and "Medicinal plants (indigenous and exotic) used in Ceylon" [11]. e botanical names have also been checked with the data available at http://www.theplantlist.org. e specimens were deposited at the Herbarium in the Department of Biochemistry, Faculty of Medicine, University of Ruhuna, Sri Lanka.

Quantitative Analysis of the Ethnobotanical Information.
e knowledge on the usage of medicinal plants was quantitatively assessed by the relative frequency of citation (RFC), family importance value (FIV) of a plant family, and use value (UV) as described in our previous study [10] and the method of Kayani et al. [15] by substituting in the relevant equations given below. RFC and FIV were calculated to quantitatively determine the consensus between informants on the use of medicinal plants in the region as it gives the local importance of a species or a family [15,19,20]. e value of RFC for a particular species of medicinal plants is based on the citing percentage of informants for that particular species, where RFC � FC/N (0 < RFC < 1), in which RFC is the relative frequency of citation, FC is the number of informants who mentioned the species, and N is the total number of informants participating in the study.
Family importance value (FIV) of a plant family was calculated by taking the percentage of informants mentioning the family, where FIV � FC (family)/N × 100, in which FC is the number of informants mentioning the plant family and N is the total number of informants participating in the study.
Use value indicates the relative importance of plant species known locally, and the following formula was used to determine UV: UV i � U i /N i , in which U i is the number of use reports described by each informant for species i and N is the total number of informants describing the specific species i.

Results and Discussion
As speculated, the results of this study revealed that the majority of the inhabitants who have participated in this study depended on the indigenous plant resources as treatments and preventive measures against a number of disease conditions.
Out of the total of 284 informants, 132 (53.7%) claimed the use of medicinal plants for the treatment of various ailments such as diabetes, inflammatory conditions, and skin diseases, while the rest of the informants (46.3%) mentioned the nonadherence to herbal remedies. In addition, these plants are also used as energy boosters and cosmetics. Among those people, 47.6% firmly believed in the safety and low adverse effects associated with the herbal formulations and mentioned this as a reason for their preference. In addition, the previous success with herbal remedies (35.86%) was also a main contributing factor for the people to continue with plant-based therapies. Unlike the observations of our previous ethnobotanical study conducted in Gampaha District, Western Province of Sri Lanka [10], some people (2.76%) stated that the nonavailability of modern health-care facilities in their villages was a reason for them to opt for herbal remedies. e majority of the users (67.9%) claimed the use of herbal preparations at the initial stage of a disease before going for any other medications, while 26.01% have mentioned the simultaneous usage with other medications. Only 6.1% stated the use of herbal therapeutics as a last resort, when other treatment methods have failed. e knowledge of the herbal remedies had transferred through generations while the influence of media in promoting the use of herbal therapeutics could not be neglected (Table 1). e study revealed the use of 64 medicinal plants belonging to 42 plant families, out of which Coriandrum sativum L. (RFC � 0.163) was the most cited species, followed by Zingiber officinale Roscoe (RFC � 0.146) and Hygrophila auriculata (Schumach.) Heine (RFC � 0.109). e family importance value was highest in Zingiberaceae (22.8%) ( Table 2). e highest use value was reported for Coscinium fenestratum (Goetgh.) Colebr. e most dominant life form of the species reported was herbs (37.5%; Figure 2). e most frequently used part of the plant was leaves (36.2%; Figure 3), followed by seeds/fruits (18.9%). Medicinal plants used in folk herbal remedies were prepared and administered in various forms. e most common preparation method was infusion (34.4%) while 14.9% were used in the form of a paste (Figure 4). e percentage of oral administration (71.1%) of herbal preparation was much higher than the external or topical application (24.3%) and inhalation (4.6%). Most of the crude drugs were prepared from single plant species; however, combinations of multiple species as well as the use of adjuvants such as honey, sugar, coconut milk, salt, and coconut oil have also been reported. For example, a paste prepared from the fruit of Myristica fragrans Houtt. with the juice of Citrus aurantifolia (Christm.) Swingle is a common remedy for stomachache while honey or sugar is added to most of the infusions to reduce the bitter taste. e summary of the medicinal plant species used in Polonnaruwa district to treat various disease conditions is given in Table 3.
As depicted in Figure 5, herbal remedies were used by the inhabitants of Polonnaruwa district against 15 broad categories of ailments/conditions reporting the highest number of species against swellings/pains or sprains. Further, the local people in the study area utilize medicinal plants (around 30 plant species) for the treatment of other classical inflammatory symptoms like fever [10,21] or chronic inflammatory diseases like asthma [22].
Interestingly, the medicinal uses of some of the plants mentioned by the informants have not been documented in the literature particularly in the popular book series on Sri Lankan medicinal plants by Jayaweera [11], for example, the use of Spondias dulcis Parkinson for high blood pressure and Hemidesmus indicus (L.) R. Br. ex Schult., Artocarpus heterophyllus Lam, and Scoparia dulcis L. for diabetes. erefore, the documentation of this rich undocumented ethnobotanical knowledge could offer new avenues for pharmacological investigations on prospective new drugs of herbal origin. Moreover, plant species like Asparagus racemosus Willd, Terminalia bellirica (Gaertn.) Roxb., Piper Scientifica betle L., Murraya koenigii (L.) Spreng., Citrus aurantium L., Citrus aurantifolia (Christm.) Swingle, and Zingiber officinale Roscoe have been identified as remedies for snake bites in a recent ethnobotanical study conducted in Western and Sabaragamuwa Provinces in Sri Lanka [9]; however, none of the informants participated in the present study mentioned about the utility of those plants in the treatment of snake bites. Besides, some of the informants mentioned that the wealth of knowledge is rapidly diminishing due to the dearth of elderly people who are knowledgeable on folklore medicine as well as lack of interest in younger generation to systematically study these traditional healing systems. us, our findings would enable the preservation of local knowledge which is obtained by trial and error and transferred over generations. In addition, a dramatic degradation of habitat due to construction work and the ruthless use and overexploitation of medicinal plants by local people and the traders of medicinal plants solely for commercial purposes were observed during the field survey. As an example, it has been mentioned that there is a high demand in the local market specially for Salacia reticulata Wight, a plant which was also documented in Icones Plantarum Malabaricarum as           as an imported spice in the local markets in Sri Lanka. Although the majority of the people in the nonuser category (50.9%) had used some kind of herbal therapeutics at some stage of their lives, the usage was discontinued mainly due to the difficulty in the preparation and collection of plant materials from their surroundings (59%). In addition, the relatively long period of time taken for healing, unpleasant smell, and the taste has also hindered their use. Moreover, some have profusely refused such remedies, due to the unavailability of scientific records on the safety and the efficacy of herbal formulations. Interestingly, 75.4% of these nonusers mentioned that they would shift to herbal products if the efficacy of these products could be scientifically validated.

Conclusion
is study reports the first in-depth ethnobotanical survey in the North Central Province of Sri Lanka, where agriculture is the primary livelihood of the inhabitants of the area. Among 64 medicinal plants belonging to 42 reported plant families, the family importance value was highest in Zingiberaceae. e most popular medicinal plants among the inhabitants of Polonnaruwa district include Coriandrum sativum L., Zingiber officinale Roscoe, and Hygrophila auriculata (Schumach.) Heine. Despite the eroding folkloric knowledge that depended on the oral tradition for its transmission to successive generations, the indigenous herbal remedies are still popular among the local communities in the study area. Moreover, even the majority of the nonusers are ready to shift to herbal products upon the scientific validation of the therapeutic efficiency, and it signifies the necessity of comprehensive pharmacological and phytochemical investigations of these traditional formulations.

Abbreviations
RFC: Relative frequency of citation FIV: Family importance value UV: Use value.

Data Availability
e data used to support the findings of this study are included within the article.
Ethical Approval e ethical approval was obtained from the ethical review committee, Faculty of Medicine, University of Ruhuna, Sri Lanka.

Consent
Informed consent was obtained in writing prior to the study. 10 Scientifica