**3. Indigenous knowledge capital in the use of medicinal plants of the Tay ethnic group in Thai Nguyen province**

Knowledge of medicinal plants depends upon ecological diversity along with differences in languages and cultures of ethnic communities. The knowledge of the use of plants varies within each ethnic group and between ethnic groups. It is of great significance to learn and research knowledge of using traditional medicinal plants to provide a database for science. Knowledge of using medicinal plants is very diverse, the same species has many different uses. Knowledge of using medicinal plants is often supplemented through experiences from medical practice, as well as from failures in the process of using medicinal plants. The knowledge used is associated with the culture, beliefs, and customs of each ethnic group and each locality.

#### **3.1 Experience in identifying and collecting medicinal plants**

Traditional knowledge of plant names and uses depends on the experience of local people. The folk names of plants are the source of the diversity of traditional


**Table 1.**

*Total of medicinal plants used by Tay ethnic group in Thai Nguyen province.*

**Figure 2.** *Number of plant species by most representative family used for medicinal purposes in the study area.*

knowledge. In addition, the system of folk names and ways of recognizing plants is passed down from generation to generation in the community.

Through research and interviews with people who have experience in using medicinal plants, it was found that the Tay people in Thai Nguyen province know how to use many types of medicinal plants. Most of the families in the Tay ethnic community know some medicine to cure some common diseases such as fever, headache, and stomachache, and are famous for treating stomach ailments, nervous breakdowns, and fractures. Depending on the type of disease, one tree or several trees can be used. The Tay people have many simple but effective remedies. In general, the use of plants to make medicine is very diverse and depends on each remedy as well as the treatment experience of the physician.

The Tay people have a unique way of naming medicinal plants, the names of medicinal plants are often based on the shape and characteristics of parts of the plant such as leaves, stems, roots, flowers, and fruits, which have similar characteristics to the shape, characteristics of a certain subspecies to name. Or the Tay people have many different ways of recognizing medicinal plants, which can be based on the plant's life form, such as "thảu" is used to indicate the life form of climb; "nhả" refers to a life form that is mainly herbaceous, "khảu" refers to the habitat of medicinal plants in the forest. In addition, based on the color of the parts of the tree to name them: "khảo" means "white"; "đăm" means "black"; "lưởng" means "gold"; "đẻng" means "red". This is a very interesting explanation for the naming of medicinal plants of the Tay people, helping the Tay people remember medicinal plants more easily, avoid confusion and pass it on to the next generation more effectively.

#### **3.2 Plants parts used**

Research on the used parts of medicinal plants not only shows the richness and diversity in the healing power of those parts but also has great conservation significance, at the same time, the study of medicinal plant parts partly assesses the sustainability of the exploitation and use of medicinal plant resources in ethnic minority communities. The results of the parts used as medicine according to the experience of the Tay ethnic group in Thai Nguyen province are shown in **Figure 3**, [6].

**Figure 3.** *Plant parts used for their medicinal properties (Percentage).*

The research results on the frequency of using plant parts for healing show that leaves and stems are two parts that are used more than other parts such as flowers, fruits, seeds, roots, bark, and sap. The leaf represents the most used plant part (48.0%), followed by stem (26.5%), root (20.2%), whole plant (15.6%), flower (3.4%), fruit (5.9%), seed (2.8%), and bark (6.5%). This can be due to easy accessibility and availability of leaves among other plant parts. The use of leaves for medicinal purposes is preferred by most ethnobotanical studies because it is less likely to affect the survival of the plant as compared to roots [14–16]. Similar results were also shown in the study on medicinal plants of the Co Tu ethnic group in the buffer zone of Bach Ma National Park [17]. Many studies conducted around the world also show that leaves are used more than other parts of the plant [18–20]. The use of medicinal leaves reduces the level of threat to medicinal plants or helps in the sustainable harvesting of medicinal plants. Further, it has been reported that roots and bark are not sustainable for the development of traditional medicine [21].

Five different modes of medicine preparation were documented. Decoction (47.7%) was the most frequently quoted mode of preparation (**Figure 4**, [6]), followed by crushing (29.9%), sauna (18.0), pickle wine (11.8%), and raw (5.6%). It was also found that for some plants, different modes of preparation were used to treat different diseases. For example, leaves of *Glycosmis parviflora* (Sims) Little were prepared as a decoction for treatment of rheumatism and bone pain cure which may also be prepared as a sauna for treatment of edema.

#### **3.3 Combination of medicinal plants**

Medicinal plants make important contributions to the health care system of local communities. The collected ethnobotanical data is a valuable source for the development of new drugs in the future. The purpose of research on the conservation of ethnic medicinal plants is not only towards the conservation of medicinal plant genetic resources but also to preserve and promote the experience and knowledge of ethnic groups in the use and development of medicines.

The Tay ethnic people in Thai Nguyen province combined some species to treat a few diseases (**Table 2**, [6]). For example, a decoction of *Abutilon indicum* (L.) Sweet (leaf), *Trevesia palmata* (Roxb. ex Lindl.) Visan. (stem), *Pandanus tonkinensis* Martelli ex. Stone (fruit), *Eclipta prostrata* L. (stem, leaf), *Schefflera heptaphylla* (L.) Frodin (root), is used to treat kidney disease. Similarly, a decoction of *Schefflera heptaphylla* (L.) Frodin (root), *Argyreia acuta* Lour. (stem and leaf), *Sigesbeckia orientalis* L. (whole plant) and *Schefflera venulosa* (Wight & Arn.) Harms in Engl. & Prantl (root) is used to treat neurological, and cerebrovascular stroke. The plants which were used more than once by Tay ethnic people to treat several diseases are *Schefflera heptaphylla* (L.) Frodin, *Plantago major* L., (2); *Elephantopus scaber* L., *Achyranthes aspera* L., (3); *Streblus asper* Lour. (4).

R = root; S = stems; W = whole plant; L = leaf; F = fruit; B = bark; RF = rind of fruit.
