A systematic analysis of anti-diabetic medicinal plants from cells to clinical trials

Background

Diabetes is one of the fastest-growing health emergencies of the 21st century, placing a severe economic burden on many countries. Current management approaches have improved diabetic care, but several limitations still exist, such as decreased efficacy, adverse effects, and the high cost of treatment, particularly for developing nations. There is, therefore, a need for more cost-effective therapies for diabetes management. The evidence-based application of phytochemicals from plants in the management of diseases is gaining traction.

Methodology

Various plants and plant parts have been investigated as antidiabetic agents. This review sought to collate and discuss published data on the cellular and molecular effects of medicinal plants and phytochemicals on insulin signaling pathways to better understand the current trend in using plant products in the management of diabetes. Furthermore, we explored available information on medicinal plants that consistently produced hypoglycemic effects from isolated cells to animal studies and clinical trials.

Results

There is substantial literature describing the effects of a range of plant extracts on insulin action and insulin signaling, revealing a depth in knowledge of molecular detail. Our exploration also reveals effective antidiabetic actions in animal studies, and clear translational potential evidenced by clinical trials.

Conclusion

We suggest that this area of research should be further exploited in the search for novel therapeutics for diabetes.

Improvement in post-partum uterine involution in rats treated with Apios americana

OBJECTIVE

Apios americana, a plant used as a staple ingredient of native American diets, has various properties, including anti-cancer, anti-hyperglycemic, hypotensive, and anti-inflammatory activity. In Japan, Apios is used as a post-natal medication. After parturition, women undergo a period of recovery as they return to pre-pregnancy conditions. However, few health products that aid post-partum recovery are on the market. We explored whether Apios can accelerate the post-partum recovery process, in particular the involution of the uterus.

METHODS

Female rats kept in individual cages were mated with two male rats, with the exception of the control group (female rats without mating, on basal diet; n=6). After delivery, rats were divided into five groups based on their diet: basal diet (model; n=6); basal diet+oral intake at 5.4 g/kg of Chanfukang granules (a Chinese patent medicine preparation for post-partum lochia) (positive; n=6); basal diet containing 10% Apios powder (low; n=6); basal diet containing 20% Apios powder (medium; n=6); basal diet containing 40% Apios powder (high; n=6). Five days later, uteri and spleens were weighed. Uterus and spleen indices for each rat were calculated by dividing visceral weight by the total weight. Hormone and cytokine concentrations were measured using enzyme-linked immunosorbent assay (ELISA). Histological analysis of uteri was completed using hematoxylin and eosin (H&E) staining. Expression of matrix metalloproteinases and inhibitors in uteri was measured by western blotting.

RESULTS

Our results showed that Apios treatment reduced the post-partum uterus index and regulated the hormone concentrations. Moreover, we found that the process of uterine involution was accelerated, based on morphological changes in the uterus. In addition, our results indicated that Apios alleviated the inflammatory response induced by the involution process. Transforming growth factor β was also found to be regulated by Apios. There were significant downregulation of matrix metalloproteinases and upregulation of their inhibitors by Apios, which suggested that Apios increased the rate of the collagen clearance process.

CONCLUSIONS

These results, based on experimental observations at the molecular and protein levels, verified our hypothesis that Apios can improve uterine involution, and demonstrated the potential application of Apios in post-partum care.

Chemical Constituents of Apios americana Tubers and Their Inhibitory Activities on Nitric Oxide Production in Lipopolysaccharide-Stimulated RAW 264.7 Macrophages

Apios americana is an important food crop producing edible tubers with high nutritional and medicinal values and is widely cultivated in many countries. Despite its usefulness, research on its secondary metabolites and biological activities has been limited. In the present study, a new coumaronochromone, (2 R,3 S)-3,7,4'-trihydroxy-5-methoxycoumaronochromone (1), and two new isoflavone glucosides, 7,2',4'-trihydroxy-5-methoxyisoflavone-4'- O-β-d-glucopyranoside (3) and 5,7,4'-trihydroxyisoflavone-7- O-β-d-gentiotrioside (5), were isolated from the tubers of A. americana via chromatographic separation. Seventeen known compounds (2, 4, and 6-20) were also obtained from this plant part. The chemical structures of 1, 3, and 5 were determined by the interpretation of spectroscopic data. The absolute structure of the new compound 1 was established from experimental and calculated electronic circular dichroism spectra. This is the first study to determine the absolute configuration of a 3-hydroxycoumaronochromone derivative. The potential anti-inflammatory activity of the 20 isolates obtained was evaluated by measuring their inhibitory effects on nitric oxide production in lipopolysaccharide-stimulated RAW 264.7 macrophages. Among the isolates, seven compounds (1, 3, 6-8, 15, and 20) showed substantial inhibition of nitric oxide production in RAW 264.7 cells, with the most active being compound 1 (IC₅₀ value of 0.38 ± 0.04 μM).

Effects of C-Glycosides from Apios americana Leaves against Oxidative Stress during Hyperglycemia through Regulating Mitogen-Activated Protein Kinases and Nuclear Factor Erythroid 2-Related Factor 2

Main components of Apios americana leaves extract (ALE) were flavonoid C-glycosides, including vitexin (46.7%), schaftoside (18.9%), and orientin (4.32%). In vitro, ALE restored glucose consumption, glucose uptake, and glycogen content in glucose-induced hepatic cells. Exposure of HepG2 cells to high glucose resulted in reactive oxygen species and O₂^- accumulation, while ALE alleviated these increases by 47 ± 0.68 and 68 ± 0.74%, respectively. Glucose increased c-Jun N-terminal kinase (JNK) and decreased extracellular signal-regulated kinases 1 and 2 (ERK1/2) and p38 phosphorylation, while ALE reduced p-JNK and p-p38 but not p-ERK1/2, accompanied by nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase-1, and NAD(P)H quinine oxidoreductase 1 downregulation. In vivo, the lifespan of Caenorhabditis elegans was more violently shortened by paraquat under hyperglycemia, while ALE protected this damage in N2 worms (2.6 times extension) but not in daf-16 mutants. Furthermore, p38/PMK-1 and Nrf2/SKN-1 expressions in worms were suppressed by glucose, which were reversed by ALE treatment. These results suggest that ALE prevents glucose-induced damage via regulating specific mitogen-activated protein kinases and Nrf2 pathways.