Ethnobotanical survey of plant species for herbal tea in a Yao autonomous county (Jianghua, China): results of a 2-year study of traditional medicinal markets on the Dragon Boat Festival

The study was conducted in Jianghua, where herbal tea has a significant cultural value and it is traditionally consumed. This region is located in Yongzhou City, which borders Guangdong and Guangxi Provinces, between 110° 25′ S–112° 10′ S and 24° 38′ W–25° 15′ W (Fig. 1). It covers an area of 3248 km². The total population of Jianghua was 510,000 inhabitants in 2013. It is the only Yao autonomous county in Hunan Province, with the largest population of Yao nationality in the 13 Yao autonomous counties throughout the country. This area features a subtropical monsoon climate, and the weather is relatively moderate, with an annual average temperature of 18–18.5 °C, and plenty of rainfall. It owns the biggest and most famous medicinal market in Hunan Province and the surrounding region, that is, the traditional medicinal markets at the Dragon Boat Festival.

The Dragon Boat Festival, or known as the Duanwu Festival, is a traditional Chinese cultural holiday. The festival occurs on the 5th day of May in the traditional Chinese calendar. There are three most well-known and widespread activities conducted to celebrate the Dragon Boat Festival, preparing and eating zongzi, drinking realgar wine, and dragon boat racing. These customs could be dated back to over 2500 years ago [4]. The Dragon Boat Festival was held at the summer solstice which is a period of high incidence of disease. Many Chinese folklorists pointed out that the Dragon Boat Festival originated from the concept of people fighting diseases and exterminating evils [5, 6]. So, during the Dragon Boat Festival, some indigenous persons, country doctors, and herbalists collect various kinds of plant and sell them to customers, retailers, or formal vendors at the traditional medicinal market.

Field surveys including informant interview, structured investigation, free-listing tasks, and voucher specimen collection were conducted during the Dragon Boat Festival in 2016 and 2017. A total of 215 vendors between 22 and 83 years of age were interviewed at the traditional medicinal markets at the Dragon Boat Festival in Jianghua, Hunan Province, to record plants used for herbal tea and to document traditional knowledge on their medicinal function, habitat, and conservation status. Of the vendors, 70% were over 50 years of age, and these vendors were almost equally male and female. The study was carried out following the International Society of Ethnobiology Code of Ethics [7], and all of the participants were informed of our intent prior to the start of the interviews. In addition, every vendor signed a benefit-sharing agreement. The majority of the vendors worked independently or in small groups, and when the vendors spoke only the Yao language, translation was required by an individual that we had hired. Vendors were asked to complete structured ethnobotanical questionnaires, which were answered willingly without payment, the questions included (1) Which species are used for herbal tea? (2) Where do you gather this plant? (3) What plant parts can be used for herbal tea? (4) What is the function of this plant in herbal tea? and (5) What plants do Yao people here use for herbal tea? Bunches of medicinal plants were purchased to identify the species and to prepare the voucher specimens followed by the Flora of China (http://​frps.​eflora.​cn/) and the collections in PE (the Herbarium, Institute of Botany, Chinese Academy of Sciences), and KUN (the Herbarium, Kunming Institute of Botany, Chinese Academy of Sciences). We then deposited them in the Ethnobotanical Lab, Minzu University of China. Photographs were taken to record all of the plant species.

The conservation status of each plant was revised by the Information System of Chinese Rare and Endangered Plants (http://​rep.​iplant.​cn/​protlist/​7) (Table 1).

Cognitive salience (CS) [8] and use value (UV) [9] were applied to determine the greatest cognitive and cultural importance of these medical plants in Jianghua.

Free-listing is a method to obtain cognitive salience from relatively large samples [10, 11]. Interviewers collected traditional knowledge from large samples of free-lists which reveal cognitive salience from individuals’ local knowledge. The measure of cognitive salience includes both list position and list frequency irrespective of list length or number of respondents [8, 12]. We interviewed 215 informants and recorded 215 free-lists; here, we calculated the mean cognitive salience (CS) for each listed species,

F is the number of lists where the particular species is mentioned in all lists while Z is the number of informants. B determines how one plant precedes other plants mentioned in a respondent’s list. K is the number of listed species in one informant, and r (i) is the ith order of each plant’s list position.

The closer to the first position (or rank) the item(s) are, the greater the cognitive salience of item(s) is deemed to be.

The use value (UV) is to quantitatively evaluate the relative importance of species [13‐15] used by Yao people,

where Ui refers to the number of medical use cited by an informant for per species and N is the total number of all informants. When there are many use reports mentioned for one plant, it indicates the use value of this plant is high.

The coefficient of similarity (S) of herbal tea plants between Jianghua and Lingnan regions was calculated by the following formula: S = 2c/(a + b) (a and b are species used by Jianghua and Lingnan regions, respectively; c are species in common use) [16].

Chi-square analysis was applied to find whether the traditional knowledge of herbal tea such as plant life form and plant part(s) used varied considerably between Jianghua and Lingnan.

The cognitive salience of 169 species ranked from 0.012 to 0.343 (Table 1); 10 species listed as the most salient are Artemisia argyi Levl. et Van., Stemona tuberosa Lour., Chloranthus fortunei (A. Gray) Solms-Laub., Grangea maderaspatana (L.) Poir., Lophatherum gracile Brongn., Usnea diffracta (Vain.) Articus, Melastoma dodecandrum Lour., Damnacanthus indicus Gaertn., Plantago asiatica L., and Leonurus artemisia (Laur.) S. Y. Hu. The most 20 salient species are listed in Table 2. The greater the value of cognitive salience, the more culturally important the species is. For example, the highest value refers to Artemisia argyi Levl. et Van., which is a fundamental medicinal plant to local people. The least value of cognitive salience is Clematis uncinata Champ.

The use value of 169 species ranked from 0.33 to 1.74. They are Artemisia princeps (1.74), Viscum liquidambaricola (1.68), Viscum diospyrosicola (1.60), Hedyotis auricularia (1.60), Clerodendrum chinense var. simplex (1.57), Cirsium japonicum (1.54), Achyranthes aspera L. (1.52), Schefflera octophylla (Linn.) Frodin (1.51), Panax japonicus (T. Nees) C. A. Mey. (1.48), and Pseudodrynaria coronans (1.47), which are widely and frequently used by local people.

Herbal tea in Lingnan region is based on the theory of traditional Chinese Medicine (TCM); many recipes used in herbal tea are evolved from prescriptions of TCM [17]. However, Yao people in Jianghua did not record their traditional knowledge of herbal tea with books or scripts instead of folksongs and teaching generations by experience and dictation. We compared herbal tea plant in Jianghua with Drug Standard Database (http://​www.​drugfuture.​com/​standard/​), including Chinese PharmacopeiaI (2015 and 1977 versions), Tibetan medicineI, Uygur medicine, and Japanese Pharmacopoeia, and 124 species are not listed in Pharmacopeia (Table 1). Among these 124 species, the medicinal use of not all species can be supported by literatures. For example, Yao people in Jianghua indicated that Achyranthes aspera can relieve pain, which was verified by Barua et al. In 2010, they verified the antinociceptive activity of the methanolic extract of leaves of A. aspera in animal models of nociception [18]. Cirsium japonicum stops bleeding, which was verified by Chen Qi et al. in 2012 [19]. However, most of these 124 species cannot be found in the supporting literatures. Yao people in Jianghua generally believed that Clematis henryi is a good medicine for relieving pain, Heteropanax fragrans can treat rheumatism, and Marsdenia sinensis can treat heatstroke. There is a great need to further study these plant species.

In Jianghua, heat-clearing and detoxifying is the most common medicinal function, followed by treating rheumatism, because the Dragon Boat Festival is at the end of spring and the beginning of summer, weather conditions are hot and humid, so the main plant materials used for herbal tea are focused on heat-clearing and detoxifying and treating rheumatism.

In Jianghua, 22 species were involved in eliminating inflammation; however, of the 83 species used for heat-clearing and detoxifying, 14 species were involved in eliminating inflammation; it shows that 63.6% of the medicinal plant species sold to eliminate inflammation are also used for heat-clearing and detoxifying, so it is important to conduct some studies to understand the dual effect and discover the possible relationship, which is useful for the theoretical construction of the traditional Chinese medicine (TCM).

Over the past 20 years, the safety [20] and pharmacological efficacy [21‐24] of herbal drinks have drawn attention. Findings have elucidated that some phytochemicals in herbal tea are beneficial to human health [25‐28], while some are risky to humans [29‐34]. Therefore, further research is needed to analyze the bioactivity and toxicity of herbal tea. Among 169 species, two of them are forbidden as raw materials for food based on an announcement from The National Health Commission of the People’s Republic of China (http://​www.​nhfpc.​gov.​cn/). They are Dysosma versipellis (Hance) M. Cheng ex Ying and Tripterygium wilfordii Hook. f.

Dysosma versipellis: Podophyllotoxin, a chemical compound isolated from D. versipellis, is recorded to show cytotoxicity resulting emesis, diarrhea, and hepatic and central nerve system lesion [35‐38]. However, due to its chemical function similar to colchicine, podophyllotoxin and its derivatives have been synthesized and utilized as anti-tumor drugs [39]. Besides, it was recorded to be used as an antiviral material for treating condyloma acuminatum caused by human papilloma virus (HPV) [40]. D. versipellis is largely be utilized for clearing heat and detoxification, rheumatism, and promoting blood circulation by Yao people in Jianghua. However, due to excessive consumption, the conservation status of D. versipellis on “China’s red list” is registered as vulnerable. At present, D. versipellis is cultivated in Jianghua.

Tripterygium wilfordii: The extract of T. wilfordii, a Chinese herb, has anti-inflammatory and immunosuppressive activities and an established history of use in the treatment of rheumatoid arthritis [41, 42]. However, the most common side effects of T. wilfordii are gastrointestinal tract disturbances, such as diarrhea, leukopenia, thrombocytopenia, rash, skin pigmentation, and malfunction of the male and female reproductive system [43].

The resurgence of interest in natural products has fueled the global herbal tea market. In 2013, Yujing Liu recorded 241 species used for herbal tea in Lingnan Region (China) [1]. By comparing the herbal tea plants commonly used by Jianghua and Lingnan, there are 23 common plant species, among which, there were 17 species that had consistent function and 6 species have different functions.

By comparing the 6 species having different functions in Jianghua and Lingnan, we cannot confirm that they have various medical functions. Achyranthes aspera, Fagopyrum dibotrys, Lonicera confuse, Lonicera japonica, Dendranthema morifolium, and Juncus effusus are heat-clearing and detoxifying herbs. In Chinese medicine, the lower the fire is equal to clear heat. We found that there may be a relationship between detoxifying and antibacterial or anti-inflammation properties, because most of the plants with detoxifying properties have antibacterial or anti-inflammation effects (Table 3) [44‐52]. For Gleditsia sinensis, Jianghua people pointed that it can induce diuresis, and the Lingnan people indicated that it can relieve pathological heat and remove dampness through diuresis. This may represent a direction for our study of the activity of Chinese herbs. So it will be necessary to verify the pharmacological activity in the future.

By comparing the herbal tea plants commonly used by Jianghua and Lingnan, the coefficient of similarity of herbal tea plants is 11.2%, which is low. We compared all plant parts used in the Jianghua and Lingnan regions. The common used plant parts are whole plant, root, leaf, stem, rhizome, tuber, flower, fruit, bark, seed, pith, branch, and shoot thorn. In Lingnan region, there are several particular used plant parts. They were aerial part, bulb, kernel, bud, peel, stigma, stem node with horns, and pollen. However, in Jianghua region, the particular used parts are pod, shoot, and fruit cluster. We selected all common used parts to do statistical analysis with chi-square analysis; the results (p value < 0.05, χ² = 61.333) show the used plant parts varied significantly between these two different regions. Hence, the variation of used plant part in two regions accounts not only for the particular mentioned used parts but for varied usage rate of each common used part. For example, in Lingnan region, root (20.78%) is the most frequently mentioned used part, while in Lingnan region, it is whole plant (38.36%). The variation of plant part used suggests that the medical plant tradition is far different between the Lingnan and Jianghua regions. The low coefficient of similarity and the variation of plant part used reflect a relatively great difference of herbal tea plant tradition between Jianghua and Lingnan.

In the ethnobotanical surveys, we found that there are 14 poisonous species, which need to be payed attention. They are Pothos chinensis (Raf.) Merr., Typhonium flagelliforme (Lodd.) Blume, Trachelospermum jasminoides (Lindl.) Lem., Asarum sagittarioides C. F. Liang, Dysosma versipellis (Hance) M. Cheng ex Ying, Celastrus orbiculatus Thunb., Tripterygium wilfordii Hook. f., Senecio scandens Buch.-Ham. ex D. Don, Hemsleya macrosperma C. Y. Wu ex C. Y. Wu et C. L. Chen, Reineckia carnea (Andr.) Kunth, Eomecon chionantha Hance, Fallopia multiflora (Thunb.) Harald., Stemona tuberosa Lour., and Schizocapsa plantaginea Hance. In addition, we do not know if there is a phenomenon of substitutes or adulterants in Jianghua traditional market. Based on the Drug Standard Database, we listed the originality of all of the species (Table 1). So, the plants that are nonexistent in the Drug Standard Database need to be scientifically investigated for their efficacy and safety in the future.