Medicinal Plant Use for Type-2 Diabetes Treatment in the Traditional Vietnamese Medicine System of Southern Vietnam

Author

Lan Truong, The Graduate Center, City University of New YorkFollow

Date of Degree

6-2022

Document Type

Dissertation

Degree Name

Ph.D.

Program

Biology

Advisor

Douglas Daly

Committee Members

Michael Balick

Lisa Offringa

John Rashford

Renuka Sankaran

Eleanore Wurtzel

Subject Categories

Alternative and Complementary Medicine | Botany | Nutritional and Metabolic Diseases

Keywords

medical ethnobotany, complementary and alternative medicine, traditional Vietnamese medicine, Mekong River Delta, medicinal plants, Buddhism

Abstract

This ethnobotanical study examines the traditional health care system of the Mekong River Delta in Vietnam. The basic inquiry focuses on how the healers in the traditional Vietnamese medicine (TVM) system are treating a disease relatively new in Vietnam, type-2 diabetes (T2D). The study includes a description of the system in which the healers work. The research design compares two locations, one on the mainland (Rạch Giá City) and the other on a nearby island (Phú Quốc Island).

There are six chapters. The first chapter establishes foundational information about the region, population, and the traditional medical system. The results of the research are reported in the following four chapters, starting with an analysis of the TVM system. The patterns in the healer choices of medicinal plants for T2D are established in the next chapter, followed by a chapter reporting the anti-diabetic activity of these species as evaluated with standard diabetes assay that tests for α-glucosidase inhibition. The last research chapter compares these results to the enzyme inhibitory activity of a random species collection. This research tests a fundamental assertion in medical ethnobotany that a healer-selected approach to selection of medicinal materials is more efficacious than the random sampling of local plants. The final chapter summarizes the research findings.

Chapter 1 is a literature review that provides the foundation for interpreting traditional medicine as it is practiced in the region. The complex TVM system is discussed in detail in order to provide background information integral to interpreting the results in the research chapters.

The broad agricultural plains of the MRD provide the background character for southern Vietnam. The MRD region developed a unique medicinal system, partly as a result of the biocultural attributes that distinguish this area from the more northern sections of the country. Traditional Vietnamese Medicine (TVM) is found linked to Buddhist monasteries throughout the KG landscape.

Traditional Vietnamese Medicine has deep roots in the south of Vietnam, while traditional Chinese medicine (TCM) is primarily practiced in northern Vietnam. TVM is a formal system that requires rigorous training and certification. The TVM approach to T2D is different from Western medicine but complementary to this more recently introduced approach to healthcare.

The prevalence of T2D matches the progression of the economy of the country. The increased prosperity is seen in increased access to excess calories and is linked to an increasingly sedentary population.

Chapter 2 is a detailed examination of the TVM healers and the context in which they operate. Traditional healers are the focus of the study as they are the knowledge holders, but study findings reveal that TVM is more than a group of healers. The entire TVM system includes the institutions (Buddhist monasteries) and the participation of the many other individuals who complete the system. Demographic data from two locations are examined to see if there are significant differences in the characteristics of the healer populations; only the age differences differentiated the two locations in any meaningful way. As a result, the healer demographics are combined and the TVM system is treated as representative of Kiên Giang province.

The healer demographics show a diversity in age (ranging from 31 to 72). Healers in Rạch Giá (RG) are on average 10 years older than those in Phú Quốc (PQ). The healers began practicing at an average age of 29 years old. Survey interviews documented that the aging healer population is resulting in Buddhist organizations’ efforts to recruit and train a new generation of healers.

There is a gender ratio of 3:18 (females:males). This gender ratio is an interesting development with potential future implications for a system that previously excluded women.

There is a consensus that T2D has rapidly risen today and this increase is a concern for the region. Traditional healers collaborate with the Western medicine system for diagnosis and some aspects of the treatment of T2D. There is variability in the cited causes of the increase of T2D, although “soda consumption” is generally recognized as a problem and the adoption of a plant-based diet (as part of the Buddhist tradition) is acknowledged as a potential preventative solution.

Herbal medicines are central to TVM treatment for T2D. The supply chain depends on a team of paid staff and volunteer members involved in the collection, preparation, storage, and dispensing of plant material. Plant harvesters or collectors are the most common source of medicines, in which they wildcraft, principally from local forests. Alternate sources include plant cultivation in temples and home gardens. Interviews show that healers from the two study sites rely on one another to supply complementary species.

The central link of all TVM participants in the system is the adherence to the Buddhist belief of “good karmic deeds/merits” accruement, in which charitable work will be rewarded in the afterlife. The reliance of volunteers in the system and the shared use of physical facilities (temple grounds) allows TVM to be a free or donation-based health system accessible to the general public.

Chapter 3 focuses on the plants that TVM healers identified as foundational to their T2D treatments of T2D. This part of the research analyzes the patterns in the species used by traditional healers, searching for both common and unusual species and herbal admixtures/ combinations.

Healers identified 36 species they use for T2D treatments, with individuals using between one and seven species. There is a mean of 3.4 species in a healer’s T2D pharmacopeia.

There are no species that dominate the healer plant selections. Only six species were chosen by more than 15% of the healers (3 or more healers out of 20). Only two species, Vernonia amygdalina Delile and Momordica charantia L. (garden variety), are used by 30% or more of the healers. The most common species used is V. amygdalina, reported by nine healers (45%). About two-thirds of the species are used by a single healer, which indicates remarkable individuality is a characteristic found among all the healers.

The determination of the general patterns of species choices shows that most of the healers from both sites fit a single group. However, the pattern of species use is sufficiently different for five of the healers that these few individuals are seen as statistically different from the healers in the one main cluster.

Momordica charantia (bitter melon) is collected in two forms, one cultivated and the other collected in the wild; healers attribute higher bioactivity to the wild populations.

Polyherbal (multi-species) formulations are the norm for T2D treatment in the TVM system. These admixtures contain a variety of species, many of which are unique to an individual healer. The use-pattern analyses focus on the primary plant species healers use in their T2D formulations as their complete species list is considered to be proprietary information. Even with this limitation, this individuality is surprising, as more than half (63%) of the reported species are used by only a single healer.

Entire plants are used in most preparations (46%), followed by formulations using wood (19%). The data show a preference for bitter-tasting species (half of the six most commonly used species). Common edible fruit species are included in the healer list, along with some non-fruit organs (wood, leaves). One concerning use was the rare and endangered species Hydnophytum formicarum Jack. This species has a dwindling population due to overharvesting.

The preparations included material from 24 plant families; the three most commonly listed by the healers are Annonaceae, Cucurbitaceae, and Leguminosae. Despite the greater representation of these three families, none of the six most commonly used species are from the same family. The family diversity of species is indicative of the strongly individualistic use of plants by the healers.

Chapter 4 is the analysis of the 35 plant species identified by 20 TVM healers for T2D treatment. The in vitro analytical test for glucose inhibition (anti-diabetic activity) is the α-glucosidase inhibition assay, with acarbose (an anti-diabetic drug) as the control. This anti-diabetic activity screening identifies which species used by healers for T2D treatment are likely to provide effective results in a Western context.

The suite of species analyses provides feedback on efficacy information for the healers and contributes to the growing body of data on plants showing potential for T2D treatment.

The assay identifies 15 species with significant hypoglycemic activity (IC50 < 100 μg/ml). Among these, ten species (27% of the total) have strong activity (IC50 < 50 μg/mL). Twenty species show no significant activity.

Eight of the 24 families tested have species showing only strong anti-diabetic activity (under 50 μg/mL). At the other extreme, in 12 of the families, none of the species show any significant activity.

Similarly, none of the six most used species (at least three healers used each species) in T2D formulations exhibit anti-diabetic activity. The six species are Vernonia amygdalina Delile, Momordica charantia L., Pandanus tectorius Parkinson ex Du Roi, Orthosiphon aristatus (Blume) Miq., Glinus oppositifolius (L.) Aug.DC., and Physalis angulata L.). Helixanthera parasitica Lour. is a parasitic species with high activity variability based on the host species it grows on. Healers indicated a preference for H. parasitica from specific host trees, such as Morus alba L. (another healer-selected species that is among the fifteen species with the highest anti-diabetic activity).

The fact that healers’ choices do not indicate a preference for species with strong anti-diabetic activity may be explained in the context of TVM theory. The guiding principle that governs these formulations is called Quân (King) - Thần (Rooks) - Tá (Knights) - Sứ (Bishops/Pawns). Quân-Thần-Tá-Sứ translates to elements of Vietnamese chess (Cờ Tướng), a popular strategy board game based on Chinese chess (Xiangqi), where the players are hierarchical and influence one another. The variation in healer choices depends on the patients and the healer’s goal of simultaneously treating the many aspects of the disease. In addition, the application of this concept has the potential for a synergistic effect where the combination of plants increases the overall effectiveness. However, plant combinations cannot be tested in the analyses.

Chapter 5 tests the ethno-directed sampling hypothesis, which is central to the study of ethnobotany, as this hypothesis compares the in vitro potential of healer-selected and randomly sampled species. In this study, the test uses the α-glucosidase assay. The comparison is between the 36 healer-selected species and the 52 species randomly collected in the same general area in which TVM healers obtain their wild-collected plants.

No known previous studies show equal or higher bioactivity in a random sample compared to a healer selection. Here, laboratory analyses found that 15 healer-selected species and 29 randomly sampled species have significant α-glucosidase inhibitory activity. These species represent 41.7% of the healer-selected sample and 55.8% of the random sample. There is no statistically significant difference in the relative percentage of species showing significant inhibitory activity between the two samples.

Besides the test of the ethno-directed sampling hypothesis, this study identifies a set of species and assesses them as possible alternative plants for use by TVM healers in T2D treatments. Several of these species have no diabetes studies and presenting them here suggests they might be considered for inclusion in the TVM materia medica, particularly if their other properties (safety) are found to be appropriate. The inclusion of randomly sampled species demonstrating high inhibitory activity can offer potential new sources of anti-diabetic medicines. The addition of new therapeutic species for diabetes treatment can be helpful not only to the traditional healers in the study but for anyone interested in new sources of anti-diabetic herbal medicines.

Chapter 6 is a summary and integration of the preceding research chapters.

This study meets a goal beyond fulfilling the research objectives. The research also achieved a successful cross-cultural collaboration between the U.S. and Vietnamese institutions and governments. This work included the active involvement of the local community as part of the research and the development of international relationships for continued collaboration.

Recommended Citation

Truong, Lan, "Medicinal Plant Use for Type-2 Diabetes Treatment in the Traditional Vietnamese Medicine System of Southern Vietnam" (2022). CUNY Academic Works.
https://academicworks.cuny.edu/gc_etds/4838