Preliminary exploration of herbal tea products based on traditional knowledge and hypotheses concerning herbal tea selection: a case study in Southwest Guizhou, China

Background Herbal tea usually refers to “beverage plants that do not belong to the genus Camellia”, and it holds a significant historical legacy as a traditional beverage among specific regions and ethnic groups. In light of this, our research aims to investigate and analyze the traditional knowledge pertaining to herbal tea plants used by local people in the Qianxinan Buyi and Miao Autonomous Prefecture, Guizhou Province. We also initiated preliminary efforts to create tea products from herbal tea leaves using various processing techniques. Additionally, we attempted to test hypotheses to elucidate how local people select herbal tea plants. Methods Data related to the use of herbal tea plants in this study were collected through semi-structured interviews and participatory observations in four villages in Qianxinan. Quantitative indicators, including the relative frequency of citation (RFC) and the relative importance (RI) value, were calculated, and the availability of plants was also evaluated. General linear model was performed to examine the relationship between the frequency of citation and resource availability, as well as the correlation between the relative frequency of citation and the relative importance, to test both the resource availability hypothesis and the versatility hypothesis. Centella asiatica tea was processed using techniques from green tea, black tea and white tea, with a preliminary sensory evaluation conducted. Results A total of 114 plant species were documented as being used for herbal teas by local residents, representing 60 families and 104 genera. Of these, 61% of herbal tea plants were found growing in the wild, and 11 species were exotic plants. The family with the highest number of species was Asteraceae (20 species). The study identified 33 major medicinal functions of herbal tea, with clearing heat-toxin and diuresis being the most common functions. General linear model revealed a strong correlation (correlation coefficient of 0.72, p < 0.001) between the frequency of citation and plant availability, as well as a significant correlation (correlation coefficient of 0.63, p < 0.001) between RFC and RI. Under different processing conditions, the characteristics of Centella asiatica tea exhibited variations and were found to be suitable for consumption. Conclusion The consumption of herbal tea serves as a preventive measure against common ailments for local residents. The resource availability hypothesis, diversification hypothesis and the versatility hypothesis were shown to provide some insight into “how and why local communities select plants for use.” Exotic herbal tea plants in the study area also possess valuable therapeutic properties. The processing and production of Centella asiatica herbal tea products hold promising prospects.


Background
Chinese tea culture can be traced back to ancient times, boasting a remarkable antiquity.According to The Classic of Tea by Yu Lu in the Tang Dynasty (around year 780), tea has a history over 5000 years in China.The earliest tea drinking in Chinese history is associated with the emperor Shennong (茶之为饮, 发乎神农氏), who is credited with establishing Chinese agriculture and medicine.Shennong supposedly tested hundreds of wild herbs to see whether they had any therapeutic use.Multiple research reports show that flavonoids, alkaloids, phenols and other biologically active ingredients with immune-boosting characteristics are found in herbal teas [1,2].Herbal teas can even improve people's mental health [3][4][5][6].Additionally, herbal teas include polyphenols, saponins, oligosaccharides, selenium, zinc and other useful components and are an important source of antioxidants [7].
Typically, tea is regarded to be a beverage produced from the leaves and buds of the genus Camellia (sect.Thea, including C. sinensis var.sinensis, C. sinensis var.assamica, C. sinensis var.dehungensis, C. taliensis, C. crassicolumna).The term "herbal tea" is currently ambiguous but it generally refers to infusions made from the roots, stems, leaves, flowers, fruits and even whole plants of various plant species excluding those from the Camellia genus [8].Herbal tea plants can be used alone or in conjunction with other herbs to make beverages.According to Traditional Chinese Medicine and other ethnomedical systems of China, internal heat can build up in the body, especially during the transitions between seasons [9].People typically rely on herbal plants to prevent and treat ailments in their daily lives in places where medical clinics are underequipped [10,11].Preclinical research provides support for the use of herbal teas in the treatment of various illnesses [12].For instance, the plant Linum usitatissimum, used to make traditional tea drinks "Emolientes and Emolienteros" from Peru, demonstrates the capacity to repair liver damage [13].In Greece, chamomile tea (Matricaria chamomilla) may reduce the risk of thyroid cancer [14], while the legume tea plants Aspalathus linearis and Cyclopia intermedia from South Africa exhibit anti-mutagenic properties [15].Similarly, the infusion of Chrysanthemum morifolium, a popular Asteraceae plant in Japan, has shown improvements in type II diabetes conditions [16].Eagle tea, primarily produced in southwest China from the leaves of Litsea coreana, contains total flavonoid, which can lower serum triglycerides in rat blood and liver tissue as well as prevent lipid absorption [17].Additionally, Dihydromyricetin found in vine tea (Ampelopsis grossedentata) has the ability to mitigate oxidative stress [18].These findings underscore the potential of various herbal teas in the prevention and management of chronic metabolic disorders.
A wide variety of herbal tea plants can be found in township markets and are extensively consumed in 27 provinces of China [19].Herbal tea beverages are highly popular in southern China due to their capacity to reduce internal heat and address various medical conditions.At present, there is not much research on herbal tea in Guizhou, except for eagle tea and Kuding tea, and research status regarding herbal tea uses is still not fully understood [20,21].Therefore, we performed the study in an effort to fill the gap left by the limited documentation of herbal tea in Guizhou.
In recent years, both in China and abroad, there has been a growing focus on researching herbal tea and developing new products using fresh plant leaves as the primary raw material [17,22,23].Additionally, the traditional tea-making processes have seen enhancements.
Steps such as fixation, withering, fermentation, rolling and drying are crucial in the tea processing industry [24].These steps not only enhance the color, aroma and taste of tea but also significantly improve its flavor quality.Moreover, they increase the content of active ingredients in herbal tea.Currently, the processing of herbal tea primarily involves processes like evaporation, fermentation, rolling and drying [25][26][27], and it is in the early stages of being systematized.Centella asiatica, a plant belonging to the Apiaceae family, is widely used by locals in the study area for various purposes.Previous research has indicated that Centella asiatica is rich in a variety of phenolic compounds, such as rutin, quercetin and chlorogenic acid [26,28], which are recognized for their antioxidant properties.Therefore, we aim to investigate the impact of different processing techniques on the quality of Centella asiatica herbal tea.This research will serve as a reference for the processing of other types of herbal teas.
In 2017, Gaoue et al. [29] synthesized existing research theories and pathways, reviewing and discussing 17 major ethnobotanical theories and hypotheses.More and more effort has been made to develop theories and hypotheses to promote ethnobotany as a hypothesis-and theory-driven discipline [30][31][32].Hypotheses including resource availability hypothesis, diversification hypothesis and versatility hypothesis were put forward to address "how and why do local people select plants for use" [29].The resource availability hypothesis states that a given plant is used because it has more accessibility or local abundance [33].The versatility hypothesis predicts that people are more likely to retain knowledge, use and access to a plant that has a greater number of applications for humans [33,34].It is believed that plants that are used more tend to be plants with a large use category, which is measured by the relative importance (RI) of plants to reflect the utilization degree of a certain plant in the local community [34].The diversification hypothesis is proposed to contribute to the understanding of the reasons why exotic species are incorporated into local medical systems which alien plants could help fill therapeutic gaps not filled by native plants [35].Theoretical hypotheses could provide the basic structure of a discipline, help explain and predict phenomena, promote innovation and discovery and promote the further development of the discipline.Without a solid theoretical foundation, ethnobotanical research will lack direction and coherence, making it difficult to achieve lasting progress.Thus the present work also is intended to test these three hypotheses put forward by other ethnobotanists, as well as to discuss the possible selection strategies related to the use of herbal tea plants in China.

Study area
Qianxinan Miao and Buyi prefecture (at 104° 35′-106° 32′ east longitude, 24° 38′-26° 11′ north latitude) is located in the southwest of Guizhou Province in Southern China.The total area of the prefecture is 16, 805 km 2 , accounting for 9.7% of the total area of the province.According to official statistics from 2019, the registered population of the prefecture reached more than 3,688,100.The prefecture has 35 ethnic minorities including Buyi, Miao, Hui and Han, among which Buyi has the largest population.The region has a humid subtropical monsoon climate, with an average annual temperature of 13.8-19.4°C and an average annual rainfall of 1352.8 mm.The forest area of the prefecture is 1.010 million hm 2 , the forest area is 1,027,000 hm 2 , and the forest coverage rate reaches 61.17% [36].Our research covered four counties/cities (Xingyi City, Zhenfeng County, Wangmo County and Ceheng County) with relatively concentrated ethnic minorities and rich traditional cultural diversity (Fig. 1).

Ethnobotanical survey
Ethnobotanical surveys on the utilization of herbal tea plants in Qianxinan Prefecture were carried out in the four villages in the studied counties from June 2020 to October 2021.After explaining the purpose of our study to the local community government and obtaining permission, the local community staff were invited to join us in the field survey as translators.Informants were selected by snowball sampling [37].Altogether 110 informants (53 women and 57 men) aged between 14 and 86 were interviewed (Table 1), from four ethnic groups: Buyi, Miao, Yi and Mongolian.Semi-structured interview and participatory observation were used to collect information on herbal tea plants from selected informants [38].Herbal tea plant specimens were collected in the field, and photographs of the plants were also taken while the informants were there.
Using descriptions in the Flora of China (http:// www.iplant.cn/) as a guide, herbal tea plant specimens were identified and cataloged to the herbal tea plants list.PuBiao network pharmacopoeia (http:// www.zhong yoo.com/, https:// db2.ouryao.com/) was used to confirm whether herbal tea plants were used for medicinal herbs.The exotic plant species were screened according to the "Alien Invasive Flora of China" (five volumes) [39][40][41][42][43], and their origin was determined by referring to the "Flora of China".

Data analysis
Relative frequency of citation (RFC) was used to show the local importance of each collected herbal tea plants [44].The relative frequency of citation (RFC) formula is: The frequency of citation (FC) refers to the number of informants mentioning the particular species, and N (1) is the total number of informants, without considering the use categories of species [45].Theoretically, the value range of this indicator is 0 < RFC < 1.The larger the index, the higher the importance of the species in the survey area.Jaccard index (JI) is calculated to compare similarities in herbal tea uses between four counties (cities) [46].The Jaccard Index formula is: a is the number of plant species utilized only in region A; b is the number of plant species utilized only in region B; c is the number of plant species utilized in both regions.
The relative importance (RI) of the species was calculated according to the formula [47].
The purpose of the RI is to investigate the types of use of a given species by respondents and the specific uses within each category, so that the "number of use categories" and "the number of types of uses" can be used to calculate the degree of use of the plant in a particular region or culture.NUC (number of use categories) is the quotient between the number of use types of a plant and the number of use types of the most used plant [46]; NT (number of types) is the quotient between the number of uses of the plant and the number of uses of the most important species.
Resource availability of herbal tea plants was assessed according to informants' description and authors' observation during fieldwork which was ranked by scoring one (most rare) to five (most common).General linear model was performed using SPSS (27.0.1) to analyze the correlation between the frequency of citation and resource availability, as well as the correlation between relative frequency of citation and the relative importance, to test both the resource availability hypothesis and the versatility hypothesis [33,34,48].The correlationship image was created using the Origin Por 2022 software (Version 9.9) [49].

Materials
Fresh leaves of Centella asiatica were collected from Centella asiatica experimental site of West Campus of Guizhou University in April 2023.Fresh samples were processed into green tea, black tea and white tea, respectively.

Processing
The fresh leaves from the same batch were combined and then divided into three equal samples, each weighing one  kilogram.Then each sample was processed into tea samples of Centella asiatica green tea, Centella asiatica black tea and Centella asiatica white tea according to green tea, black tea and white tea processing standard [50].
The processing of Centella asiatica green tea primarily involves evaporating, rolling and drying, the processing of Centella asiatica black tea follows the steps of withering, rolling, fermenting and drying, while the processing of Centella asiatica white tea consists of withering and drying.

Diversity
In total, 114 species of herbal tea plants representing 60 families and 104 genera were recorded in Qianxinan (Table 2), and they were widely distributed in various families.The majority of herbal tea plant species in the survey area were found along roadsides (48 species) and in fields (29 species).They were also present under the forests, near houses and in grasslands.The Asteraceae family had the highest number of plant species (20 species), followed by the Lamiaceae family, which included seven herbal tea plant species.The Rosaceae, Apiaceae and Fabaceae families each had five species of herbal tea plants, while other families had fewer species.The life forms were mainly herbs (accounting for 61.4%), followed by shrubs (22.8%), trees (8.8%) and vines (9.7%) (Fig. 2).Most of herbal tea plants are also found in Chinese Materia Medica, which proves that herbal tea plants have the same origin as medicine and food (Table 2).Local communities commonly adopted simple methods for herbal tea plant preparation, either by washing the plants for immediate use or by drying them for later utilization.These approaches require minimal investment, involve simple procedures and facilitate easy preservation, making herbal tea popular.
Local people in Qianxinan utilized various parts of herbal tea plant resources, encompassing 11 different types: whole plants, roots, leaves, stems, fruits, flowers, aboveground parts, seeds, velamina, buds and seedcases.During the survey, a total of 157 occurrences of these parts were documented (Fig. 3).The whole plant and leaf parts of the plant are the preferred choices for daily herbal teas due to their accessibility and abundance.The whole plant was the most frequently mentioned (with 55 occurrences, 35%) which serves the dual purpose of reducing waste during the processing and increasing production of herbal tea plants.Roots, leaves, stems and fruits were also common utilization parts, with mentions ranging from 10 to 30 times.In contrast, flowers, aboveground parts, seeds, velamina, buds and seedcases were mentioned fewer than 10 times, indicating their relatively infrequent usage.
The collection of herbal tea plants can take place throughout the year, and different parts of the plant can be gathered for tea consumption at various times of the year (Table 2).Local inhabitants noted that different plant parts offer distinct flavors and nutritional benefits.For example, Buddleja officinalis was collected locally in February and March as special natural dyes and can be decocted for herbal tea.The tea prepared from flowers has a mellow and sweet taste.Fruits of Pyracantha fortuneana can serve as snacks, or be dried and soaked for a beverage with sweet and brisk taste.Different parts can be employed in diverse ways, either for medicinal purposes or for daily consumption, depending on their characteristics.The tea prepared from flowers often had a mellow and sweet taste, while the taste of tea made from leaves was relatively mellow and astringent.
The highest level of similarity in species-level herbal tea uses was observed between Zhenfeng and Ceheng, with a Jaccard index (JI) of 0.17.Conversely, the most significant differences were found between Zhenfeng and Wangmo, with a JI of 0.06.When examining the genus level, the utilization of herbal tea plant resources exhibited the highest similarity between Zhenfeng and Ceheng (JI = 0.18), while the similarity between Zhenfeng and Wangmo was lower (JI = 0.07).

Health care effect of herbal tea plants
The locals not only use herbal tea plants for making beverages but also incorporate them into their daily lives for various purposes such as seasoning, food coloring, and spices.The local population believes that herbal tea plants provide a wide range of health advantages effectively addressing a spectrum of 33 significant health disorders (Table 2).Clearing heat-toxin was the most commonly stated property, and there were 46 species that had this function and were mainly distributed in Asteraceae family (14 species, accounting for 30%).Diuresis and nourishing the liver were frequently cited by locals as the intended effects of consuming herbal tea, and these properties were associated with plants from the Fabaceae family (three species, accounting for 15%) and the Lamiaceae family (three species, accounting for 21%), respectively.Clearing heat and eliminating dampness (a total of 13 species, including three species from Apiaceae family), diminishing inflammation (13 species           = Exotic plant in total, three species of Caprifoliaceae), and invigorating the spleen to promote digestion (a total of 12 species, including three species from Rosaceae family) were also found to be prevalent within their respective plant families.Additionally, moistening the lung and relieve cough (a total of 12 species), hemostatis (a total of 11 species) and lowering blood pressure (a total of 10 species) were also frequently mentioned therapeutic benefits (Fig. 4).

Resource availability hypothesis, versatility hypothesis and diversification hypothesis
According to the evaluation on the availability of recorded herbal tea plants, 14 species were most common plants (12%), 33 species were more common plants (29%), 30 species were common plants (26%), 22 species were less common plants (19%), and 15 species were uncommon plants (13%).The most common plants can be collected on the roadside, in front of and behind houses, where people live.The results showed that the frequency of citation of herbal tea plants in the study area was positively correlated with their availability (r = 0.72, p < 0.001) (Fig. 5A).There were 55 herbal tea plants with relative importance higher than one, including Centella asiatica, Lonicera similis, Taraxacum mongolicum, Artemisia argyi, and Houttuynia cordata.General linear model showed a significant positive correlation between the relative importance of herbal tea plants and the frequency of mentions (r = 0.63, p < 0.001).Houttuynia cordata (RFC = 0.51, RI = 1.60),Centella asiatica (RFC = 0.38, RI = 2) and Lonicera similis (RFC = 0.37, RI = 1.8), were the most commonly used species for tea by locals (Fig. 6).Apparently, locals preferred to mention and use plants with higher versatility (Fig. 5B).
There were 11 exotic plants, accounting for 10.5% (Table 3), which were Erigeron annuus, Bidens Pilosa, Crassocephalum crepidioides, Bidens bipinnata, Eclipta prostrata, Sonchus oleraceus, Oenothera rosea, Oenothera rosea, Amaranthus tricolor, Stellaria aquatica, Cyperus rotundus and Olanum pseudocapsicum.Most of these plants were native to the Americas, followed by Asia, Africa and Europe.The RI values of 11 exotic plants were all above 0.6 (Table 3), and they were often used in the treatment of malaria.The number of native plants to treat gynecological diseases was similar to the number of exotic plants, but there were differences in the parts used.At present, half of the exotic herbal tea plants listed in the study area had been included in the books of Chinese Materia Medica (Table 2), and Senna occidentalis had been included "Processing standard of Chinese herbal slices in Guizhou Province (贵州省中药饮片炮制规范)".In multipurpose herbal tea plants (RI > 1), 83% (46 species) were native plants.Although the RI value of exotic plants was relatively lower than native plants, they were rich in flavonoids, polyphenols, terpenoids and other compounds to treat certain diseases and were incorporated into the local medical system in the folk (Table 3).

Preliminary exploration of Centella asiatica tea products
The RI value of Centella asiatica was one, and its types of uses covered food, medicine, and was usually used as tea drinks, with the effects of clearing heat-toxin and dampness, eliminating swelling, promoting blood circulation and removing blood stasis.The tea was prepared by boiling it at a ratio of 1:50 tea for 5 mins, and the sensory quality of the tea was assessed based on attributes such as color, aroma, taste, leaf structure, and more.Regarding the appearance, the white Centella asiatica tea was distinctive in that it was not rolled, and the tea leaves remained intact and uniform.In contrast, the green and black tea processes required rolling, resulting in a more uniform appearance of tea leaves.In terms of the color of the tea, all three processes yielded a bright, yellow soup, with the white tea process producing a slightly lighter color.The taste of the tea varied across the different processes, with the green and black tea processes offering rich and diverse flavor profiles.Aroma differences were observed between the black tea process and the other two processes due to the fermentation (25-28 °C, 85% relative humidity-RH, three hours) involved in the black tea process, which produced a stronger woody aroma.Regarding the leaf structure, the leaves were spread out uniformly under all three processing conditions.Notably, the leaves of the green tea were found to be softer compared to those of the other tea samples (Fig. 7, Table 4).

Reasons for the use of herbal teas by local people
Our survey revealed that the local population has limited familiarity with the six major types of Camellia tea, which include green tea, black tea, dark tea, white tea, oolong and yellow tea.In contrast, there are a wide variety of herbal plants in Qianxinan, which are easily accessible and can be processed.The 114 species of herbal tea plants recorded in this survey are regarded as the traditional beverage plants of local people, of which 67 species are Chinese medicinal plants (58%).The medicinal functions of these plants are quite comprehensive, and their long-term use in the local area has proven effective in preventing, treating, and managing common Fig. 4 The efficacy of herbal tea and number of plants illnesses.Asteraceae plants are known for their potent in clearing heat-toxin, as well as their ability to disperse blood stasis and alleviate pain.They also exhibit cooling effects on the blood and are frequently found in herbal form, making them convenient for collection.Whether ingested or applied topically, they can rapidly eliminate toxins from the body or the body's surface [61].Rosaceae plants, on the other hand, are rich in saponins, which have a notable impact on blood vessels.They can reduce capillary permeability, minimize blood seepage, and serve as effective hemostatic agents [62].The Apiaceae family is particularly noteworthy for its capacity to promote blood circulation, dispel blood stasis, alleviate itching and pain, and address issues related to dampness and cold.These plants excel in enhancing circulation and dispelling surface coldness [63].Argyreia pierreana can be used both externally and internally, and it offers therapeutic benefits including clearing heat-toxin, treating traumatic injuries, as well as possessing anti-inflammatory and hemostatic properties [64].Perilla frutescens, Lophatherum gracile and Plantago asiatica have demonstrated diuretic effects [65][66][67].Mentha canadensis is effective in treating gastrointestinal diseases and infectious diseases, with pharmacological activities that include hepatoprotective, anti-inflammatory and antioxidant properties [68].
Every ethnic group engages in subsistence activities to sustain its way of life, fulfill its most fundamental needs and support further development during their interactions with nature [69].Local residents note that the harvesting time for herbal tea is spread throughout all seasons, and they collect the useful parts for consumption in accordance with the plant's growth cycle.In spring and summer, when plants are in the vegetative growth stage, in addition to gathering parts for drinking, locals also harvest plant buds for use in dishes to meet their nutritional needs.During summer and autumn, when plants are in the reproductive growth stage, many are collected as whole plants, which can also be dried and used for medicinal purposes.In autumn and winter, when the aboveground parts of plants wither and the plants go dormant, the roots are collected and boiled since they contain higher levels of active ingredients.The consuming of herbal tea, using the traditional sun-drying method [70], and selling the excess in local markets to supplement their livelihoods are common practice among the Buyi people.
Frequently mentioned are plants that are readily available in proximity to people's living areas, making availability a significant factor influencing their preference for herbal tea.The resource availability hypothesis effectively elucidates the connection between the presence of herbal tea plants and their utilization by the local population across the study area.Eclipta prostrata (L.) L 1.3 America Rich in triterpenoid saponins, flavonoids; it has the effect of nourishing liver and kidney, cooling blood and stopping bleeding [58] Erigeron annuus (L.) Pers 1.0 Eastern America Rich in vanillic acid, ferulic acid, 4-hydroxyacetophenone; in folk it is commonly used in the treatment of malaria, and it has the ability to clear heat-toxin,, and aid digestion [56] Oenothera rosea L'Her.ex Ait 1.0 Southern North America Rich in kaempferol, ursolic acid, luteolin; in folk it is mainly used to decrease inflammation and pain caused by trauma [56] Senna occidentalis (Linnaeus) Link 1.5 Tropical America Rich in β-sitosterol, daucosterol; in folk it is regarded as traditional medicine, and its efficacy is mainly evident in the treatment of malaria [59] Solanum pseudocapsicum L 1.1 Mexico, the Caribbean and South America The whole plant is poisonous, and root has analgesic effect, and can be used to treat lumbar muscle strain [60] Sonchus oleraceus L 1.2 Europe and the Mediterranean Rich in luteolin, apigenin and other glycosides; in folk it is commonly used to treat icteric hepatitis and is often eaten as a wild vegetable [56] Processing of Centella asiatica tea product Different processing methods yield three distinct types of Centella asiatica tea, each characterized by variations in color, aroma, taste and unique qualities.The color of tea soup is influenced by several factors during processing, with the quality characteristics of green tea primarily shaped by the fixation process.Fixation (enzyme inactivation), a critical step in green tea processing, serves to deactivate enzymatic activity within the leaves, thereby minimizing enzyme-driven oxidation and chlorophyll degradation.This preserves the distinctive characteristics of green tea leaves [71].In our preliminary experiments, we observed that residual moisture on the surface of freshly cleaned Centella asiatica leaves causes them to stick together.Consequently, we employ an evaporating method without rapid leaf agitation during fixation.Evaporating durations within the range of 1-5 mins optimize the retention of DPPH (1,1-Diphenyl-2-picryl-hydrazyl) scavenging compounds in herbal tea [23,26].
In the production of black tea, the key process is fermentation, which leads to moisture loss in the leaves during the initial withering phase.Following rolling, leaf cell disruption reaches 80%, initiating decomposition reactions primarily driven by macromolecules, as well as phenolic oxidation and chlorophyll degradation under enzymatic influence.These processes impart multi-layered taste characteristics to the fresh leaves [27,72].In our experiments, fermentation was conducted at 25-28 °C and 85% relative humidity for three hours, resulting in the transformation of leaf color from green to deep green.The Centella asiatica black tea produced exhibited a dark green appearance, with a light yellow infusion.Furthermore, polyphenols undergo gradual transformation during the extended withering process [25,73], contributing to the development of a sweet and mellow taste profile.
Withering is a crucial stage in shaping the distinctive quality of white tea.The study revealed that the drying time required for the simple white tea processing is  shorter in comparison to the processing times for green and black teas.This is primarily because the white tea process does not involve rolling the leaves; instead, the leaves are stretched, and there is a notable spacing between them.This allows the tea sample to dry faster and the processing time to be shortened.In sensory evaluation, the key parameters for assessing quality are appearance, aroma and taste, as these factors significantly influence consumer acceptance.Overall, Centella asiatica white tea has few processing steps and basically imitated the traditional processing of the locals.The beneficial ingredients could be effectively preserved, while maintaining a sweet and smooth taste akin to traditional processing methods.The processing of Centella asiatica green tea and black tea may lead to a reduction in certain essential components of the leaves.However, it may also give rise to novel elements not present in traditional processing methods.Therefore, it is of significance to conduct in-depth investigations into the chemical composition of Centella asiatica tea under varying processing conditions.Such research holds great practical significance in optimizing the utilization of Centella asiatica resources.
The initial attempts have been made at Centella asiatica product processing also serve as a means to promote the diversification of beverages for urban residents and those residing in areas without Centella asiatica distribution.

The use of herbal tea in modern society
Herbal teas are widely consumed in Yunnan, Guizhou, Guangxi, etc., offering both excellent taste and beneficial effects.With the increasing popularity of natural health teas, herbal teas have garnered the attention of many consumers.Examples include Ku Ding Tea (Ilex kaushue), honeysuckle tea (Lonicera similis), and Guangxi sweet tea (Rubus chingii var.suavissimus).The production of herbal teas has embraced innovation in traditional processing methods to cater to the diverse needs of the modern era.Leveraging the advantages of herbal tea plants, such as their pleasant taste, aroma and heat-clearing properties, and addressing the challenge of bitterness, well-prepared herbal teas can offer a delightful taste along with their therapeutic benefits [74].In herbal tea processing, various techniques can be employed, including traditional drying and storage, as well as the creation of concentrated liquid or solid packaging formats to meet different requirements.It's worth noting that the chemical composition content of the roots, stems, and leaves of herbal tea plants often differs.Therefore, making the best use of all parts of the plant can enhance the overall utilization rate of herbal tea plants.Currently, there is a need to reasonably, scientifically and comprehensively exploit the existing herbal tea plant resources and explore them from the perspective of plant biochemistry to develop new herbal tea plant products.
The processing and consumption of teas can also be adapted to the current fast-paced and convenient lifestyles of people by creating herbal tea beverages in teabag form or formulating them into liquid herbal tea beverages [75].However, the proliferation of new herbal tea beverages like Wahaha and Nongfu Spring has led to the decline of traditional tea beverages.In an attempt to cater to the preferences of the majority of consumers, many manufacturers have started incorporating various food additives into herbal tea beverages, often overlooking the inherent nutritional value of the herbal tea plants themselves in pursuit of the commercial herbal tea beverage market [9].The safety of consuming herbal tea beverages and the biological activity and toxicity of herbal tea plants are still subjects of ongoing research.The development of herbal tea beverages should be based on research into the pharmacological activities and constituents, ensuring their safety for consumption in both the pharmaceutical and food industries.
Furthermore, in alignment with the government's initiative to revitalize rural areas, local governments should encourage agricultural cooperatives to collaborate with businesses and educational institutions for the cultivation of suitable herbal tea plant varieties in the region and establish cultivation parks.This not only fosters the growth of the local herbal tea industry but also advances the herbal tea sector as a whole, contributing to the livelihoods of local residents.

Conclusions
As a commonplace daily beverage, herbal teas in Qianxinan Prefecture serve both medicinal and refreshing purposes for locals.The selected plants reflect accessibility, versatility and remedy augmentation needs as explained by established ethnobotanical hypotheses.Specifically, the resource availability hypothesis and versatility hypothesis provide insight into plant selection patterns, indicating that accessibility and versatility influence use.Additionally, exotic plants fill therapeutic gaps not addressed by native flora, aligning with the diversification hypothesis.This rich documented flora and associated indigenous knowledge is complemented by preliminary experimental efforts showcasing quality variances across processing methods for the widely used Centella asiatica.Green Tea, Black Tea, and White Tea products made from this species exhibit suitable sensorial attributes and utilization potential.Further research should build on these foundations to comprehensively investigate bioactivities, cultivation practices, innovative products and sustainable industry development.By elucidating plant utilization drivers, processing techniques and novel beverage prospects, this study makes valuable progress in understanding and promoting the under-researched domain of herbal teas and associated ethnomedicinal traditions in southwest China.

Fig. 2 Fig. 3
Fig. 2 Life forms of herbal tea plants in Qianxinan Prefecture

Fig. 5 Fig. 6
Fig. 5 Correlation between herbal tea frequency of citation and plants availability and correlation between RFC and RI.A correlation between FC and Availability, B correlation between RI and RFC

Fig. 7
Fig. 7 Centella asiatica tea production process and the soup

Table 1
Statistics on the number of informants

Table 2
The inventory of herbal tea plants used by local people in Southwest Guizhou, China

Table 3
List of exotic herbal tea plants in Qianxinan

Table 4
Comparison of sensory quality of Centella asiatica tea