Ethnobiological study on traditional medicinal plants and fungi recorded in the Naxi Dongba sutras

Lijiang is a prefecture-level city in Yunnan Province, Southwest China. It is located in Hengduan Mountains, between 25° 23′–27° 56′ N and 99° 23′–101° 11′ E. The total area of Lijiang City covers 20 600 km² [7]. The terrain of the area is high in the northwestern part and low in the southeastern part, with the highest altitude of 5596 m and the lowest altitude of 1015 m. The maximum altitude difference of Lijiang is 4581 m [8].

The climate of Lijiang belongs to subtropical humid climate [9]. There is abundant rainfall and a distinct dry and wet season. The average annual rainfall is about 1 000 mm, and the rainy season lasts from May to October being particularly pronounced in July and August. The annual average temperature is between 13 °C and 20 °C, the average temperature of the hottest month is 18–26 °C, and the average temperature of the coldest month is 4–12 °C. Lijiang has 2500 h of annual sunshine and 147 kcal/cm² of annual solar radiation [9].

Lijiang has a forest coverage rate of 70%. The area is rich in medicinal materials and other exploitable biological resources and is known as the “kingdom of alpine plants” and “hometown of medicinal materials” [8].

The key areas of the present study were Gucheng District and Yulong County in Lijiang city, Yunnan Province, China. This area is the most concentrated area of the Naxi population in the world, with about 210 000 people, accounting for 68.5% of the total Naxi population. Naxi people live in mountainous areas with inconvenient transportation and abundant biological resources, which is why their tradition is the most convenient mean of resisting diseases. At the same time, the inheritance model of Dongba culture is masters teaching apprentices that makes a better inheritance of the Naxi traditional medicinal culture.

From February to September 2019, we screened the medicinal plants and fungi from the Dongba Sutras with the help of Dongba (the clergies who can read and write hieroglyphs) and translate the hieroglyphs into the Naxi language. Then, we carried out field research with assistance from 104 Naxi folk healers and collected traditional medicinal plant specimens. The basic survey information such as age and gender was collected and recorded. Using semi-structured interviews [10], ethnobotanical knowledge was obtained, including information about the local name, medicinal parts, harvesting methods, preparation methods, and indications of the medicinal plants and fungi from the Dongba Sutras. The informed consent of the participants was obtained before conducting the interviews, and the ethical guidelines prescribed by the International Society of Ethnobiology [11] were followed. The local names were transliterated from the Naxi or local Chinese pronunciation into the Roman alphabet following the Scheme for the Chinese Phonetic Alphabet [12] and the Basic Rules for Hanyu Pinyin Orthography [13]. The diseases treated by the medicinal plants and fungi from the Dongba Sutras were classified according to the International Classification of Primary Care (ICPC-2) [14] of the WHO (World Health Organization) [15, 16].

With the help of Naxi folk healers, 3–5 specimens of each species were collected, and the information about their habitats (e.g., altitude, latitude, longitude, and vegetation type), plant morphology (e.g., plant height, color of flowers, and corolla type), and date of the collection were recorded. The scientific and Chinese names were recorded on the label. These specimens were stored at the Herbarium, Yunnan Branch, Institute of Medicinal Plants, Chinese Academy of Medical Science (IMDY).

The following literature was used to identify the family and species names of the collected plants: Flora of China [17], Flora Reipublicae Popularis Sinicae [18], and Flora Yunnanica [19]. The scientific names were checked on The Plant List website [20]. All the plants listed are sorted at family level circumscription follows APG IV [21].

The data obtained in this study were analyzed using Microsoft Office Excel (2010) spreadsheet software. Quantitative data analysis was conducted using the informant consensus factor (ICF) method and the number of citations. ICF was calculated as ICF = (Nur - Nt)/(Nur - 1), where Nur is the sum of plant species used by all the respondents to treat a particular disease, and Nt is the number of identical plant species used by all the respondents to treat a particular disease [22].

A total of 104 respondents were interviewed (Table 1). Among them, male respondents highly outnumbered the female respondents, and 79.81% of them were over 50 years old. Naxi people live in mountainous areas and commonly collect medicinal plants. In this harsh environment, men have an advantage over women due to their physical abilities. Because the experience of treating diseases is based on long-term practice, the medical experience mastered by older healers is more comprehensive and reliable than those learned by younger healers. Moreover, it ensures the reliability of the knowledge obtained in this survey.

The educational level of the respondents was generally low, and most of them had no higher education. However, this did not affect the reliability of the results, because the acquired traditional knowledge has truly maintained the characteristics of the Naxi people.

The respondents were mainly Naxi (71.158%), followed by the Lisu (15.38%). Other ethnic groups included Han, Tibetan, Bai, and Yi. All of these people lived in Naxi communities, and their medical skills were learned from Naxi healers. All the respondents were folk healers. Although there are many ways to learn medical skills, most respondents (70.19%) developed their medical experiences with the help of their ancestors. None of the respondents had regular jobs, and many of them were local Dongba who were priests and folk healers.

According to our investigation, a total of 85 species of medicinal plants and fungi belonging to 51 families and 71 genera were recorded in the Dongba Sutras (Table 2). In the middle and high altitude areas, the main tree species belonged to the families Pinaceae, Cupressaceae, Ericaceae, and Fagaceae. Almost all parts of these plants can be used as medicine, especially their branches, which are often used by Naxi priests for various sacrificial activities. The highest numbers of plant species recorded belonged to the families Asteraceae (six species) and Polygonaceae (six species), followed by the Rosaceae (four species). It is worth mentioning that from the genus Rheum alone, we recorded three species. In addition to Rheum officinale recorded in the Pharmacopoeia of People’s Republic of China [23], we also recorded R. delavayi and R. likiangense, but their usage was different from that of R. officinale recorded in the Pharmacopoeia of People’s Republic of China.

Of all recorded species, herbaceous plants (49 species) accounted for the greatest number (Table 3), followed by trees (21 species) and shrubs (5 species). As herbaceous plants can more easily survive in a new environment than trees and shrubs [24], especially in the alpine mountains inhabited by the Naxi people, there is a lack of diversity of tree species, whereas the low herbaceous plants were abundant. At the same time, herbaceous plants are more convenient to collect than other plant life forms. Thus, the utilization rate of herbaceous plants is higher than that of trees and shrubs.

The medicinal parts of 85 medicinal plant and fungus species used by the respondents are indicated in Tables 4 and 10. The Naxi people knew that different medicinal parts have different effects. According to our analysis, in addition to the plant’s medicinal efficacy, the difficulty of its collection also affects which parts would be used. The Naxi people preferred to collect easily collectible plant parts as raw materials for medicinal preparations. Among plant life forms, herbs and small shrubs are most commonly used as medicines, and the respondents reported that for this purpose, they used whole plants, roots, or rhizomes, whereas when trees, big shrubs, or woody vines are used for medicinal preparations, the respondents used stems, branches, leaves, or bark. The flowering and fruiting periods of these plants are short; therefore, their fruits, seeds, flowers, and buds are seldom used as medicinal parts. Plant secretions are rarely used as medicinal materials because of the difficulty of their collection.

Most of the medicinal plants in the Dongba Sutras are common plants in the studied area. The abundance of medicinal plants, determined according to the classification of abundance by Germany Ecologist Oscar Drude [25], is shown in Table 5. According to this classification, the highest number of species used by the respondents is forest species, such as Quercus aquifolioides, Q. aliena var. acuteserrata, Populus rotundifolia var. bonatii, and Pinus yunnanensis. The group with few or dispersed organism included only three species: Poria cocos, Dobinea delavayi, and Panax japonicus var. major. Although the medicinal materials from these species are rarely found in the wild, they have been cultivated in the area and thus have been successfully used as medicines.

Since ancient times, Naxi people have lived in mountainous areas, where transportation is inconvenient. The medicines they used were collected in the mountains, and rare medicinal plants were cultivated in their courtyards in order to be convenient for collection. Therefore, the medicinal plants described in the Dongba Sutras were mainly wild plants, accounting for 76.47% of all medicinal plants described in the Dongba Sutras (Table 6). Because of the small population of Naxi people, their use of wild medicinal plants does not present a threat to the stability of wild plant populations.

Food therapy is an important characteristic of Chinese culture and traditional Chinese medicine (TCM). “One Root of medicine and food” is a summary of the Chinese people’s understanding of medicine and food and their relationship [26]. The life of the Naxi people is closely related with medical dietary plants, and their medicinal diets are indispensable to the health of their communities [27]. Among the medicinal plants in the Dongba Sutras, 22 species can be consumed as vegetables, fruits, dried fruits, or condiments (Table 7). For example, Lagenaria siceraria, Brassica rapa, Foeniculum vulgare, and Allium ascalonicum are common vegetable species. Setaria italica var. germanica is also used as food. For a long time, the Naxi people considered that these foods and vegetables can be used to treat and prevent diseases. Thus, they recorded them in the Dongba Sutras. Some of these medicines are used to prepare tea and do not have any negative side effects. For example, the aerial parts of Elsholtzia rugulosa which has the effect of relieving summer heat. The plant as a substitute for tea is easy to collect and prepare and has widely been used by the Naxi people. This indicated that in the Naxi people, maintaining a healthy daily diet is a very important factor in disease prevention.

The folk preparation methods of traditional Naxi medicine were relatively simple (Fig. 1a); most of them included washing and direct drying of the plant material (49.18%), followed by crushing (20.49%), soaking (13.93%), using fresh products (9.84%), blending with other agents (3.28%), and carbonization (3.28%). The medium used in the soaking process was mainly wine or water, whereas the medium used in blending included edible oils, vinegar, and honey, etc. The use of fresh plant parts as medicine is characteristic of Naxi medicine because this method is simpler to use than other methods. In this method, the medicinal parts are removed from the plants and washed, and they are used after mashing or chewing. In addition, juice extracted directly from the plant is also a common method of fresh plant intake and is mostly used for topical application. The main method of medicine consummation was oral, followed by topical and rarely buccal (Fig. 1b). Oral administration included three methods: boiling in water, washing in warm water, and drinking after soaking.

The informant consensus factor (ICF) is a measure of information diversity. The higher the ICF value, the greater the difference among plant species used in the treatment of a given disease, and the lower the ICF value, the smaller the difference among plant species used in the treatment of a disease [22]. We found that the medicinal plants and fungi in the Dongba Sutras are used to treat 96 conditions, which can be classified into 13 disease groups according to ICPC-2 (Table 8 and Table 9). The highest ICF values were recorded for the eye group (F), cardiovascular group (K), and psychological group (P) (ICF = 1.50), followed by the neurological group (N), female genital group (X), and male genital group (Y) (ICF: 1.00). Among the medicinal plants provided by different respondents, there are very few (only one or none) identical plants that can be used to treat the same group of diseases. This showed that there are many differences among Naxi people in the methods of treating a specific disease, i.e., that they have low consensus about disease treatment methods. There are two possible reasons for this: (1) as the Naxi people live in biodiversity-rich areas, the abundant medicinal plant resources provided them with a wide choice of medicinal plants to use [28], and (2) different Naxi folk healers may have different degrees of understanding of the same disease (e.g., some may be focused more on the symptoms of a disease, but ignore or miss the real cause of the disease).

Further analysis indicated that most of the plant species were utilized for the group of digestive diseases (D; Nur=36, Nt=15), followed by the respiratory (R; Nur=29, Nt=13,), musculoskeletal (L; Nur=21, Nt=12), and the general and unspecified disease group (A; Nur=21, Nt=5). The ICF values of these four disease groups were low: Group D: 0.60, Group R: 0.57, group L: 0.45, and group A: 0.75. These low values indicated that these four groups of diseases are common diseases in Naxi people living areas, and Naxi folk healers have a high consensus on the treatment of these diseases.

For the treatment of diabetes (T89: Diabetes Insulin Dependent or T90: Diabetes Non-Insulin Dependent), which is an endocrine disease that belongs to the group of endocrine/metabolic and nutritional, only one plant species was cited in the Dongba Sutras. Diaphragma juglandis fructus, the dry wood diaphragm tissue (xylem septa) that grows inside the walnut (Juglans regia), was reported as a medicinal plant that can be used to treat diabetes, and the consensus on this treatment was high. A previous study reported that the flavonoids from Diaphragma juglandis fructus have significant anti-diabetic activity [29]. This shows that as the knowledge on folk medicine is collected from long-term practical experience, its scientific nature has yet to be proven by modern science. With more research, more information from traditional medicinal practices will be scientifically proven.

The plant species with the highest number of use reports were Rheum likiangense (13 use reports), Reineckea carnea (11 use reports), Rheum delavayi (10 use reports), and Hypericum augustinii (10 use reports). Rheum likiangense and R. delavayi are endemic to a small district, and Reineckea carnea and Hypericum augustinii are endemic to China. This emphasizes the uniqueness of Naxi medicinal plants.

Among the medicinal plants in the Dongba Sutras, 25 species are endemic to China, accounting for 29.41% of the total number of medicinal plant species in the Dongba Sutras (85 species) (Table 10). Moreover, there are eight species only distributed in the areas inhabited by Naxi people (Fig. 2), including northwest Yunnan, southwest Sichuan, and Southeast Tibet. Examples include Populus rotundifolia var. bonatii, Rheum likiangense, Chesneya polystichoides, Geranium strictipes, Dobinea delavayi, Wikstroemia delavayi, Rhododendron wardii, and Scutellaria likiangensis.

The Naxi people consider human beings and nature as brothers. This ecological ethics concept lays the foundation for the Naxi people to live in harmony with nature; it shows the most primitive and simple concept of environmental conservation by human beings [30]. The distribution area of these plant species is very small. Although the Naxi people have been using these plants as medicinal materials for a long time, their populations are still stable, indicating that Naxi people attach great importance to plant conservation when collecting these medicinal plants. The Naxi people collect medicinal materials from their surroundings to treat many diseases. They never harm the environment during plant collecting, and they are grateful for being able to take advantage of wild medicinal plants. This fully embodies their idea of maintaining ecological balance. Meanwhile, artificial cultivation was adapted to expand the population of medicinal plants with rare natural resources in order to minimize their impact on wild plant resources.

The medicinal plants used by the Naxi people are diverse. A variety of herbal medicine closely related to the life of the Naxi people was recorded in the Dongba Sutras. A total of 85 species of medicinal plants and fungi belonging to 51 families and 71 genera were recorded in the Dongba Sutras, among which 25 species are endemic to China, and 8 species are distributed in a small region. There were 22 species of medicinal dietary plants recorded in the Dongba Sutras.

The knowledge of traditional Naxi medicine is always in the hands of the elderly and clergy. The traditional apprenticeship between the elderly and the young makes an assurance of the knowledge inheritance from age to age. Dongba, as the clergyman in the Naxi people, records the most important medical knowledge in the Dongba Sutras for better inheritance.

In the processing of medicinal materials, Naxi people make good use of fresh products, medicinal liquids, and plant powders. No complex processing is required from the raw plants to the medicine used, which is very convenient. Medicinal liquids can fully dissolve alcohol-soluble active substances and are easy to store. Different types of mixed powder are used internally or externally suiting the remedy to the different cases, which not only brings convenience to clinical uses but also protects the intellectual property rights of the folk healers because it is hard to know which medicinal plants are used in the powders.

The Naxi ancestors inhabit mountainous areas and are seldom influenced by alien cultures. As a result, the methods of medication are easy to follow, mainly including decocting, oral consumption with warm water, and topical. And the processing technology of Naxi medicine only includes some simple procedures like washing, drying, and crushing.

Four groups of diseases are common diseases in Naxi people living areas: they are the group of digestive diseases (D), followed by the respiratory (R), musculoskeletal (L), and the general and unspecified disease group (A). The Naxi folk healers have a high consensus on the treatment of these diseases.

Hengduan mountainous where the Naxi people who live own one of the greatest abundant biodiversities in the world. Naxi people always keep the scientific ecological ethics concept in mind. The Naxi people never harm the environment during plant collecting, and they are grateful for being able to take advantage of wild medicinal plants. Meanwhile, artificial cultivation is adapted to expand the population of medicinal plants with rare natural resources in order to minimize their impact on wild plant resources.

Dongba Sutras are recorded in hieroglyphics (Fig. 3); thus, only the Dongbas, as the clergymen, can fully understand them. Contents of the Dongba Sutras are all-encompassing. Medical knowledge only takes a small part of the whole contents, and the records are not comprehensive enough. In addition, the folk medicinal knowledge is orally passed down. Thus, it is necessary to further deepen the investigation and research efforts to systematically organize and catalog the Naxi people’s unique traditional medicine, exhibiting its due brilliance.