Medicinal plants used by rural Thai people to treat non-communicable diseases and related symptoms

The paper addresses the increasing burden of non-communicable diseases (NCDs) globally and in Thailand, especially among rural and remote communities where access to public healthcare is limited and traditional medicinal knowledge remains important. NCDs, driven by genetic, physiological, environmental, and behavioral factors, account for 41 million deaths annually, with a disproportionate impact in low- and middle-income countries. In Thailand, NCD prevalence and economic burden are rising. Traditional medicinal plant knowledge offers a potential resource for developing treatments with attributes such as multi-target efficacy, availability, and cost-effectiveness. However, this knowledge is eroding. Because traditional diagnosis relies on symptom patterns rather than instruments (e.g., blood pressure cuffs, glucose monitors), directly mapping traditional uses to modern NCD categories is challenging. The study aims to compile and analyze ethnomedicinal plant uses in Thailand relevant to NCDs and their related symptoms to identify promising species for further safety and efficacy research. The specific research questions are: (1) How many plants are used to treat NCDs in Thailand? (2) Which species are most important for specific NCDs? (3) Based on scientific evidence, should those important species be recommended for treatment?

Ethnobotany in Thailand has expanded significantly since 1990, with systematic studies documenting medicinal plant uses across remote locations. Previous work has recorded 2,187 medicinal species (over 20% of the Thai flora) and demonstrated that medicinal knowledge is unique to each village and ethnic group, influencing candidate selection for drug development and potentially reflecting geographic chemotype variation. A prior synthesis focused on Thai ethnomedicinal plants for diabetes (1990–2014), but the volume of reports has sharply increased over decades and diabetes is just one of several major NCDs. Given that traditional healers historically identified illnesses by symptoms rather than instrument-based metrics (e.g., blood pressure, blood glucose), a broader synthesis including NCDs and related symptoms is necessary. The study builds on quantitative ethnobotanical approaches and Bayesian methods previously used to assess over- and underused taxa.

Data sources comprised (1) published ethnobotanical literature (academic books, journal articles, reports, theses in Thai and English) from 1990–2020 retrieved via PubMed, Scopus, Google Scholar, and Thai university libraries; and (2) field interviews conducted by the authors in villages of Chiang Rai and Nan provinces (April 2021–March 2022) under IRB approval (COA MU-DT/PU-IRB 2021/037.0704). Inclusion criteria for literature were: adherence to ethnobotanical standards (preferably with voucher details), use of scientific plant names, Thailand-based locations, relevance to NCDs or related symptoms (cardiovascular, diabetes, chronic respiratory, cancers), and publication within 1990–2020. Traditional illness terms were translated to modern equivalents through direct translation of simple terms, author expertise from field interactions, and consultation with experienced colleagues for ambiguous cases; modern terms like hypertension and diabetes were directly translated when explicitly stated. Fieldwork used purposive and snowball sampling to select key informants (traditional healers). A walk-in-the-woods/home gardens approach and semi-structured interviews elicited local names, parts used, and treated illnesses/symptoms. Voucher specimens were prepared and identified using taxonomic keys and Thai/neighboring floras, and deposited at QSBG Herbarium (QBG) and the Department of Pharmaceutical Botany Herbarium, Mahidol University (PBM). Plant taxonomy was standardized via the World Checklist of Vascular Plants. For analysis, all informants in one study location were combined as a single unit; a “use report” was defined as a single mention (from a studied location) of a species used for a treatment. Use Value (UV) was calculated as UV = ΣUis/nis, where Uis is the number of use reports for species s in location i, and nis is the total number of use reports in location i. Higher UV indicates wider use across locations for a given ailment. A Bayesian approach (BETAINV in Excel) adapted from prior methods was used at the species level, substituting number of use reports as parameter, to identify highly used species supporting the UV results.

- Coverage: Data from 230 locations (224 from literature, 6 from fieldwork; 28 key informants interviewed in field, aged 54–72) yielded 2,100 use reports related to NCDs and 63 NCD-related illnesses/symptoms. The study documented over 700 medicinal plant species used for NCDs and related symptoms (reported as 766 species for NCDs in the abstract; 873 species when including related symptoms and across categories), spanning 179 vascular plant families. - Distribution of use reports: Cardiovascular diseases including kidney problems: 707 use reports; chronic respiratory diseases: 637; diabetes and related symptoms (including obesity): 632; cancers: 164. Within categories: hypertension had 259 mentions; improving blood circulation 110; kidney diseases 142; sputum 342 and asthma 205 (respiratory); diabetes 468 (within diabetes-related); beriberi 73. - Families: Fabaceae had the highest overall use reports (205), followed by Asteraceae (95), Rubiaceae (89), Lamiaceae (88), with additional high-use families including Poaceae, Acanthaceae, Phyllanthaceae, Zingiberaceae, Euphorbiaceae, Rutaceae, Apocynaceae, Menispermaceae, Solanaceae, Piperaceae, and Malvaceae (each >40 species represented). Fabaceae led in chronic respiratory, diabetes-related, and cardiovascular uses. - Top species overall by use reports/UV: Tinospora crispa (31 use reports), Senna siamea (28), Andrographis paniculata (21), Orthosiphon aristatus (21); also highlighted: Phyllanthus emblica, Physalis angulata, Cymbopogon citratus, Piper sarmentosum. - Cardiovascular/kidney: 382 species cited; most had 1–2 reports, 76 species had 3–9. Highest UV: Imperata cylindrica and Orthosiphon aristatus (widely used for hypertension and kidney diseases). Hypertension most often treated with Senna siamea, followed by Mimosa pudica, Piper nigrum, Rauvolfia serpentina, Moringa oleifera, Thunbergia laurifolia. Blood circulation: Tinospora crispa and Biancaea sappan. Kidney problems: Salacia chinensis, Dioecrescis erythroclada, Orthosiphon aristatus. - Chronic respiratory: 311 species cited; sputum (186 species) and asthma (133) most treated. Sputum: Phyllanthus emblica and Garcinia cowa most frequent; also Piper sarmentosum, Albizia myriophylla, Oxyceros horridus. Asthma: Heptapleurum leucanthum (highest), Cymbopogon citratus next; others include Acalypha indica, Millingtonia hortensis, Euphorbia hirta, Datura metel, Zingiber purpureum, Clausena excavata. Lung diseases (47 reports): Plantago major most used. Bronchitis (28–30 reports): Physalis angulata most used. - Diabetes and related symptoms/obesity: 329 species; 632 use reports (468 directly for diabetes). Tinospora crispa had the highest UV and use reports. Phyllanthus amarus and Senna siamea had 12 reports each (P. amarus: 11 for diabetes; S. siamea: 7 for diabetes, 5 for beriberi). Other frequently cited: Andrographis paniculata, Orthosiphon aristatus, Tectona grandis, Momordica charantia, Physalis angulata, Drynaria quercifolia, Morinda elliptica, Ziziphus oenoplia. - Cancers: 125 species for unspecified cancers; specific cancers sparsely reported. Most-cited included Suregada multiflora, Capparis micracantha, Ficus hispida, Stemona tuberosa. - Bayesian analysis: Identified 108 species as highly used; substantial overlap with high-UV species (e.g., Orthosiphon aristatus, Phyllanthus amarus, Physalis angulata, Heliotropium indicum, Piper sarmentosum).

The study situates rising NCD prevalence in Thailand within broader global trends and sociocultural change, noting that traditional healers historically diagnose by symptoms rather than instrument-based measures and consider NCDs to be modern conditions. Consequently, traditional plant uses for NCDs derive from treating symptom clusters consistent with NCDs. Despite extensive use (over 700 species), relatively few plants have strong scientific validation for efficacy or safety in NCD contexts. Evidence examples include Tinospora crispa, which shows antidiabetic effects in animal models (improved glucose utilization, insulin sensitivity, increased plasma insulin) but limited or non-significant effects in human trials; Andrographis paniculata, with evidence for improving insulin resistance and organ protection in animal models and traditional use for multiple ailments, though not officially recommended for diabetes in Thai national lists; and Orthosiphon aristatus, which has antihypertensive evidence both as a component of a multi-herb formulation comparable to captopril and via its active metabolite methylripariochromene A, with supportive clinical trial data. Phyllanthus emblica and Cymbopogon citratus, widely used for sputum and cough, are accepted in Thai traditional and modern medicine products. Many other frequently cited species (e.g., Phyllanthus amarus, Physalis angulata, Heliotropium indicum, Piper sarmentosum) lack robust efficacy data aligned with traditional claims. The findings underscore the need for rigorous pharmacological and clinical studies to validate efficacy, standardize preparations, and assess safety, especially given chronic use in NCDs and potential long-term toxicity accumulation. Sociocultural preferences and trust in traditional remedies, along with accessibility and cost, support the continued use of medicinal plants, emphasizing the importance of preserving and scientifically evaluating traditional knowledge.

Ethnomedicinal data from 230 Thai locations documented over 700 plant species used to treat NCDs and related symptoms, with concentrated use in cardiovascular/kidney conditions, chronic respiratory diseases, and diabetes-related conditions. A subset of species showed high use values and Bayesian support, highlighting candidates for further investigation. However, scientific evidence for efficacy and safety is lacking or insufficient for many highly used species. The study proposes prioritized lists of species for future efficacy and toxicity assessment across NCD categories and strongly recommends comprehensive pharmacological and clinical evaluations to guide safe and effective integration of traditional medicines into NCD management.

- The dataset reflects traditional uses compiled from literature and limited recent fieldwork; many reported uses lack robust scientific validation for efficacy or safety. - Mapping traditional symptom-based diagnoses to modern NCD categories introduces potential misclassification and interpretive uncertainty. - Literature sources varied in methodological detail; informant-level data were often unavailable, necessitating aggregation by location and potentially influencing quantitative indices (UV, Bayesian estimates). - The chronic nature of NCD treatment raises safety concerns regarding long-term use and possible cumulative toxicity, which were not assessed. - Potential regional chemotypic variation and preparation differences were not systematically controlled or analyzed.