The Secret of Health in the Daily Cuisine: the Typical Health Vegetables in the Local Markets in Central Myanmar CURRENT STATUS: UNDER REVIEW

Background Central Myanmar locate in the Indo-Burma Biodiversity hotspot, and Barma people is the main ethnic group which had settled there over thousands years ago. Nevertheless, as the major Myanmar ethnic group, Bamar people were ignored in Ethnobotanical studies. Market surveys are considered a good strategy for the preliminary screening of potential Ethnopharmacological plant resources. In the present study, we focused on the local health knowledge of vegetables of Bamar people in local markets. In the present study, we surveyed the local markets, then recorded, collected, identified and catalogued the typical vegetables, and document the knowledge of health benefits of the collected vegetables, then analyze the information of vegetables and local knowledge. The observation and interviews were used in field study, and the Ethnobotanical Indexes were used to analyze the local knowledge. We compare the local knowledge we collected with traditional medicine literatures.


Abstract
Background Central Myanmar locate in the Indo-Burma Biodiversity hotspot, and Barma people is the main ethnic group which had settled there over thousands years ago. Nevertheless, as the major Myanmar ethnic group, Bamar people were ignored in Ethnobotanical studies. Market surveys are considered a good strategy for the preliminary screening of potential Ethnopharmacological plant resources. In the present study, we focused on the local health knowledge of vegetables of Bamar people in local markets.

Materia and methods:
In the present study, we surveyed the local markets, then recorded, collected, identified and catalogued the typical vegetables, and document the knowledge of health benefits of the collected vegetables, then analyze the information of vegetables and local knowledge. The observation and interviews were used in field study, and the Ethnobotanical Indexes were used to analyze the local knowledge. We compare the local knowledge we collected with traditional medicine literatures.

Background
Local knowledge of health is great treasure for resource development and drug discovery in Pharmacology. Health food especially health vegetables are important resources for local people to maintain health [1], especially in Asian countries such as China, India, Thailand and Japan. For example, for the popularity of traditional health preserve principle, the dietetic Chinese herbs were used widely in Chinese daily cuisine [2]. In India, people used Medicinal flavor plants such as turmeric and cumin in cooking to treat digestion problems [3]. In the native people's home gardens in North Thailand, mango, jackfruit and lemon grass were very common, for cooking Traditional functional food [4]. The health benefits of Japanese fermented soy "natto" had been verified by some scientific researches such as Nagata et al (2016) [5] and Fujita et al (2012) [6].Local people had abundant knowledge of the collection, preparation, cooking, cultivation, edible safety, health function and resource management of the vegetables [7]. According to our previous researches, there were abundant functional compounds in health vegetables [8]. Besides, health vegetables were important sources of micro-minerals and vitamins [9] [10]. Therefore, these vegetables had enormous potential for health related researches and industries such as drug discover, food nutritional engineering and pharmaceutical industry. Finding inspiration from the local health knowledge in daily cuisine became a focus in Ethnopharmacology and Ethnobotany. However, most of the local knowledge just was known by native people or transmitted in small and limited areas. That means these knowledge would be very easy to disappear with time [7]. Moreover, the global change and biodiversity loss would promote the disappearing of and local knowledge [11]. Hence, it was very necessary to collect, document, analyze and explain scientifically the local knowledge of health vegetables. There were many researches about local health food had been published in the mainstream journals of Ethnobiology, Ethnopharmacology and Alternative Medicine such as Journal of Ethnobiology and Ethnomedicine, Journal of Ethnopharmacology, Economic Botany, etc. Nevertheless, for some less developed countries or remote poor regions, there were still few related researches.
Myanmar, lies between China and India, is well known for its rich biodiversity and culture diversity. As one of the key regions designated as global hotspots for biodiversity protection, Myanmar had an abundance of plant resources [12]. The U.S. National Herbarium, the Forest Department of Myanmar and the University of Yangon had provided a Myanmar plant checklist contained over 3000 species [13], KM [3]. Therefore, beside medicine, Myanmar people also used food to keep health and treat ailments by following Vinaya in traditional lifestyle, as the well-known Myanmar proverb went that "medicine was food, food was medicine". However, there were still few researches in international journals and books. The only several related researches published in English showed rich local medicinal knowledge of the ethnic minority communities in Chin State [16], Shan State [17], Kachin State [18] and Mon State [19]. Nevertheless, as the major Myanmar ethnic group, Bamar people seemed be ignore in Ethnobotanical studies.
Market surveys were considered as a good strategy for the preliminary screening of potential Ethnopharmacological plant resources [7]. According to the related previous researches, markets were important to glimpse the diversity and trade structure of the medicinal flora of a country or region [20][21][22][23]. Markets also reflected the public health and epidemic diseases of local communities [24]. Participating in markets was an important way for people to exchange goods, information and knowledge. As "showing stages" of local knowledge, local markets had been focused on by many researchers [25]. Local food markets were systems for food material and information exchange, which delivered health, economic, environmental and social benefits to the local communities [26]. In general, vegetables should be kept fresh before sale, so most of the vegetables in food market were from local place. Therefore, local food markets were ideal places to research the diversity and use knowledge of local vegetables [27][28][29][30].
With the funding of National Science Foundation of China and Southeast Asia Biodiversity Research Institute, Chinese Academy of Sciences (SEABRI-CAS) and the supports of Myanmar Forest Research Institute (FRI), we designed and carried the present study ** . In our preliminary investigation, we found that there was great diversity of vegetables in the local food markets of Myanmar [8].
It raised questions below to us: 1) how many species of local typical vegetables were sold in these markets? 2) How many species of them were regarded as health vegetables by local people? 3) Which

Field survey and data collection
The survey was carried in 10 regular markets of Mandalay Region, Magway Region, Yangon Region and Nay Pyi Taw Union Territory (Fig. 1), representing the typical food markets of Central Myanmar.
Because Mandalay is regarded as the center of Myanmar culture, half of these markets were in the Mandalay City. In total, 277 vegetable stalls or shops with random selection were investigated and plants species found in these stalls and shops were recorded. Vegetables that are not largely worldwide cultivated were of the major focus for our survey.
The frequency of occurrence of each vegetable were investigated and evaluated in the following methods. Firstly, we cruised the target market quickly and counted the number of shops or stalls with numeric counters, for the purpose of knowing the sizes and number of the shops or stalls to establish the number of randomly selected shops or stalls in each target market. Secondly, we used digital cameras to record the full image of vegetables soled at each randomly selected shop or stall. Finally, we recorded species found at each shop or stall by reviewing the photos. After that, the frequency of occurrence for each species was calculated. Meanwhile, the owners of these shops or stalls were set as the informants for participatory observation and semi-structured interviews. Data were organized in Excel sheet for further analysis. Voucher specimens of species were prepared and identified with

Species identification
Voucher specimens were collected for most species (70%) and deposited at the Herbarium of Myanmar Forest Research Institute (RAF) and Herbarium of Kunming Institute of Botany (KUN) (Appendix A), except for those common vegetables such as cabbage, tomato and eggplant. The identification was based on "A Checklist of the Trees, Shrubs, Herbs, and Climbers of Myanmar" [13] and the flora of surrounding area such as Flora of China [33] and Flora of Yunnan [34]. The scientific names were finally checked using service provided by The Plant List [35].

Categorizing functions and conservation status of the vegetables with health benefits
In traditional and local (folk) medicinal systems, the descriptions of ailments and diseases were usually diverse, which may cause difficulties in analysis. Thus, it was necessary to normalize the information with common standards before analysis. In the present study, all of the ailments were categorized with the classification of the patient's reason for encounter (CPRE)" from WHO.

Quantitative ethnobotany analysis
The use reports were prepared following Tardío and Pardo-de-Santayana (2008) [37], which were further used for calculating quantitative ethnobotany indices including frequency of citation (FC), relative frequency of citation (RFC) and use value (UV).
Frequency of citation (FC) was calculated as the sum of informants that cite a use for a particular species. Relative frequency of citation (RFC) was used to show the importance of each species in the study area [41]. The values of RFC were calculated according to the formula: Where FC s was the Frequency of Citation and N was the total number of informants in the survey. A high RFC value for a species indicates that the species was used both frequently and by a high proportion of informants in the study area.
Use value (UV) was used to measure the relative importance of species used locally [38]. The values of UV were calculated according to the formula: Where Ui was the number of use reports cited by each informant for a given species and n refers to the total number of informants. A high value of UV indicates that a species is important and used frequently in the study area.

Bibliographies Comparison
The information of health benefits were compared with available literatures of Traditional Myanmar In total, 132 plant taxa were documented, collected and identified to species level and two to genera level, which were belonged to 47 botanical families and 116 different genera (Appendix A). The most commonly found family was Fabaceae (17 species), followed by Cucurbitaceae (10 species). At genus level, most genera (105) contained one species while only 10 genera contained more than two species. Genera with most numbers of species were Allium (four species) and Citrus (four species).
More than half (75 taxa) of them were herbaceous plants, followed by trees (27 species

The most popular vegetables
In total 2,361 use-reports (UR) were obtained from 277 informants. Twenty-five taxa had more than

The wild vegetables
Twenty eight species were not cultivated but collected from wild environment (Table 1). Amongst which Dregea volubilis (UR = 230) was the most frequently seen species in the markets and followed by Centella asiatica (UR = 105). These species were also recorded as medicinal plants in the in authoritative on Traditional Myanmar Medicine [15,[39][40].

Health functions and medicinal uses
Many of the vegetables were cited as functional food with health benefit by the informants (106 taxa, 80.3%) while others were just regarded as "good for health" (26 taxa, 19.7%). The traditional knowledge on treatment of ailments was enlisted in Appendix B. Dyspepsia/indigestion (33 taxa), vitamin/nutritional deficiency (18 taxa), diarrhea (15 taxa) and weakness/tiredness general (8 taxa) were the major treatments or functions of the vegetables cited (Fig. 3). containing [15], [39] and [40]. In these publications and researches, respectively, 57 species were recorded in [15], 21 in [40], and 15 in [39] (Appendix B). Comparing the local health knowledge recorded in the present study and the records of these previous authoritative publications and researches, the local health knowledge of 35 species were similar with the records in [15], 17 in [40], and five in [39] (Fig. 4).

Discussion 4.1 Rich diversity of vegetable resources
We found a rich diversity of vegetable resources covering a broad range of genera and families from the markets of central Myanmar. The most frequently cited vegetables were commonly appeared elsewhere in the region, and been noted as "staple goods", which reflects the fact that large scale cultivated vegetables comprises the major source of vegetables for the urban population of central Myanmar. However, still, twenty-eight species were of the vegetables we recorded were collected from wild places.
Among the taxa recorded, 57 species were also noted as medicinal plants by Defilipps [42]. In Koch Bihar District of West Bengal of India, 125 species were recorded as edible plants [43].
Twenty-six taxa were assessed by The International Union for Conservation of Nature. Just only one species (Kaempferia candida) was designated as endangered species at the Vulnerable (VU) level, while others were not endangered. The only endangered species was just only noted two times (UR = 2) by two isolated informants. The informants claimed that they cultivated the plant in their home gardens.

Important vegetables and their health function
From the results of quantitative analysis, some of the recorded plants were important for local people.
These plants were used repeatedly in the local daily cuisines, some of them had health functions claimed by local people (Fig. 5).

11: Centella asiatica
As indicated by the values of UV and RFC, mango (Mangifera indica) was the most cited vegetable in the present study. As a native species [44], Mangifera indica had been used by Myanmar people for a long time [45], and in multiple ways. There was a well-noted proverb saying "Mango was the best fruit and tea leaf was the best leaf" [46]. The mango leaves were used as medicine for treating diarrhea, and the young sour fruits are made into salad, while the matured sweet fruits are one of the most famous tropical fruits.
Fermented tea leaf (La-phet) was a unique vegetable to be found in Myanmar [46]. It was a typical traditional gradient in the daily serve to the tables. It was considered to be beneficial to digestion by local people. The main species of used was Camellia sinensis var. assamica, which was identical to that of Pu'er tea in Chinese Tea. According to the informants, the fermented sour tea leaf is beneficial to digestion.
Chili (Capsicum annuum) is an important gradient in Myanmar's cuisines as well as in its neighboring countries. The uses of C. annuum in South and Southeast Asia could be traced to 500 years ago when Portugal merchants introduced the species to India [47]. There were many cultivars sold in the markets, and the appearance and taste vary. Not only as a popular spice, C. annuum was a common medicinal plant in Traditional Myanmar Medicine [15]. It is used to treat cold diseases and digestion problems by local people.
Okra (Abelmoschus esculentus), originated from Africa and spread to almost all of the tropical and sub-tropical regions [48][49], is very common in Myanmar daily diet and used to treat diabetic patients. Water spinach (Ipomoea aquatic) is one of the most popular vegetable in Myanmar, and it is usually cooked with mushrooms, where water spinach was a powerful antidote activity to relieve the poison of mushrooms according to the informants.
Fabaceae was the most used family including 17 species by local people. They were mainly cultivated as the source of protein which mainly contained in the seeds. Apart from seeds, local people also collect tender leaves, shoots, flowers and flesh roots as vegetables. For example, the tender shoots, fruits and flesh roots of Psophocarpus tetragonolobus were collected as vegetables in different seasons by local people. In Traditional Myanmar Medicine, the tender fruits were used to treat diabetes, while the leaves were used to treat eye diseases and toothache. The previous research showed that the leaves of this species is rich in protein, and vitamin A and C [50].
Species from Zingiberaceae were also important component in the local cuisine. Eight Zingiberaceae species were recorded in the present study with Curcuma longa (UR = 80) as the mostly frequently occurred species. C. longa was also named as Turmeric in English which was one of the most famous medicinal plants produced in tropical area. It could be used to treat digestion problems, according to the informants. Curcumin was identified as the functional ingredient of the specie, which was a polyphenol that possesses diverse anti-inflammatory and anti-cancer properties following oral or topical administration [8].
All of the vegetables collected from wild were used both for food and traditional medicine [15,[39][40].
These species were common in the natural vegetation of central Myanmar. In Traditional Myanmar Medicine, Dregea volubilis, the most used wild species, was used to treat multiple diseases such as Indigestion, dyspepsia, dysentery, diarrhea and insomnia [50]. The functional compounds of the species were identified as a group of Dregeosides which had effective activities such as antibacterial, antioxidant and antidiabetic [51][52][53]. Centella asiatica could improve the symptoms of insomnia and forgetfulness, according to the informants. In Traditional Myanmar Medicine, C. asiatica was used to treat memory impairment, oliguria and eye diseases [50]. A modern study found that the extract of the species had effective anti-Alzheimer's disease activities [54].
Even the most worldwide common vegetables, such as Solanum melongena and Brassica rapa, which had the highest values of RFC in the present study, were used for health care in particular way by local people. The informants claimed that S. melongena was a good tonic to treat weakness, and B. rapa was used to treat cancer and skin infection (external use). The previous studies had showed that there were some functional compounds with effective activities to human health in these vegetables [55][56][57]. For example, Glucosinolates, a group of effective compounds found in Brassica rapa, had many potential functions such as anti-microbe, anti-cancer and anti-parasites [58]. Nevertheless, there were still no clinic evidence to proof the anti-cancer activities for human body of these compounds.

Issue of food safety
Food safety was always an important topic. In the present study, some species found in the market are known to be poisonous or carcinogenic. The informants were aware the risk of consuming these species and local knowledge were available on the preparation and treatment of the raw plant materials before consume. The preparation includes blanching in boiled water, stewing with long time, boiling with detoxification material and salting. Some previous studies in food chemistry showed that the preparation methods can help to reduce toxins to certain degree [56]. For example, the corms of Colocasia esculenta were rich in needle-like calcium oxalate crystals which had heavy irritation to the oral and respiratory mucosa, but boiling long time with high temperature could reduce the irritation. High temperature cooking could also degrade the nephrotoxic compounds in Archidendron pauciflorum. For Azadirachta indica, the tender shoots and leaves should be boiled with sour material such as tamarinds until the bitter taste become thin first, then make salads and soups, because the bitter compounds of the species were regarded as toxic substances [8]. Yet, risks was still persisting, better management approaches for regulating and monitoring these poisonous vegetables and public awareness and education were fundamentally needed.

Conclusion
The diversity and use of the health vegetables in central Myanmar were very rich. The most frequent species were Capsicum annuum, Solanum melongena, Brassica rapa, Camellia sinensis var. assamica and Ipomoea aquatic, while Mangifera indica, Capsicum annuum, Abelmoschus esculentus, Ipomoea aquatic and Cucumis sativus had the richest uses and knowledge. These frequently used species were also used in Traditional Myanmar medicine, according to the records in the traditional Myanmar herb books. Just only one species (Kaempferia candida) was designated as Vulnerable (VU) by IUCN but not used frequently. According to the previous studies of some of the important species on Pharmacology, the related activities may be anti-bacterial, anti-fungus, anti-virus, anti-inflammation and antioxidation. In the present study, some species were poisons, local people had knowledge to reduce toxins. However, from the perspective of public health, just depend on the local knowledge to treat the problem of the food safety of health vegetables was not enough. The health department of government should to make policies to manage the sale the poisonous plant materials and guide the citizens to treat them before eating. Future researches could pay more attention to the material foundation of the health functions of these plants and their potential in natural drug discovery.

Declarations Ethics approval and consent to participate
The authors declare that they have no competing interests.

Consent for publication
The people interviewed were informed about the study's objectives and the eventual publication of the information gathered, and they were assured that the informants' identities would remain undisclosed.

Availability of data and materials
Please contact author for data requests.
YXF organized the study team, and provided the technical supports and guidance. ZY and LJW designed and executed the research plan. wrote the manuscript. MMS provided the technical guidance and Myanmar language translation service in field works. CWW provided the technical guidance in data analysis and English writing. TTS, AMM and PPH recorded and organized the data.
LJW and ZY identified the specimen and checked the information. All authors took part in the field works. All authors were involved in the drafting and revising of the manuscript and approved the final revision. Figure 1 the study sites and markets    Appendixanddata.xlsx