Facilitated Visual Interpretation of Scores in Principal Component Analysis by Bioactivity-Labeling of 1H-NMR Spectra-Metabolomics Investigation and Identification of a New α-Glucosidase Inhibitor in Radix Astragali

Astragali Radix: comprehensive review of its botany, phytochemistry, pharmacology and clinical application

Astragali Radix (A. Radix) is the dried root of Astragalus membranaceus var. mongholicus (Bge) Hsiao or Astragalus membranaceus (Fisch.) Bge., belonging to the family Leguminosae, which is mainly distributed in China. A. Radix has been consumed as a tonic in China for more than 2000 years because of its medicinal effects of invigorating the spleen and replenishing qi. Currently, more than 400 natural compounds have been isolated and identified from A. Radix, mainly including saponins, flavonoids, phenylpropanoids, alkaloids, and others. Modern pharmacological studies have shown that A. Radix has anti-tumor, anti-inflammatory, immunomodulatory, anti-atherosclerotic, cardioprotective, anti-hypertensive, and anti-aging effects. It has been clinically used in the treatment of tumors, cardiovascular diseases, and cerebrovascular complications associated with diabetes with few side effects and high safety. This paper reviewed the progress of research on its chemical constituents, pharmacological effects, clinical applications, developing applications, and toxicology, which provides a basis for the better development and utilization of A. Radix.

Biodiscoveries within the Australian plant genus Eremophila based on international and interdisciplinary collaboration: results and perspectives on outstanding ethical dilemmas

In a cross-continental research initiative, including researchers working in Australia and Denmark, and based on joint external funding by a 3-year grant from the Novo Nordisk Foundation, we have used DNA sequencing, extensive chemical profiling and molecular networking analyses across the entire Eremophila genus to provide new knowledge on the presence of natural products and their bioactivities using polypharmocological screens. Sesquiterpenoids, diterpenoids and dimers of branched-chain fatty acids with previously unknown chemical structures were identified. The collection of plant material from the Eremophila genus was carried out according to a 'bioprospecting agreement' with the Government of Western Australia. We recognize that several Eremophila species hold immense cultural significance to Australia's First Peoples. In spite of our best intentions to ensure that new knowledge gained about the genus Eremophila and any potential future benefits are shared in an equitable manner, in accordance with the Nagoya Protocol, we encounter serious dilemmas and potential conflicts in making benefit sharing with Australia's First Peoples a reality.

In vitro α-glucosidase inhibitory activity of Tamarix nilotica shoot extracts and fractions

α-glucosidase inhibitors represent an important class of type 2 antidiabetic drugs and they act by lowering postprandial hyperglycemia. Today, only three synthetic inhibitors exist on the market, and there is a need for novel, natural and more efficient molecules exhibiting this activity. In this study, we investigated the ability of Tamarix nilotica ethanolic and aqueous shoot extracts, as well as methanolic fractions prepared from aqueous crude extracts to inhibit α-glucosidase. Both, 50% ethanol and aqueous extracts inhibited α-glucosidase in a concentration-dependent manner, with IC₅₀ values of 12.5 μg/mL and 24.8 μg/mL, respectively. Importantly, α-glucosidase inhibitory activity observed in the T. nilotica crude extracts was considerably higher than pure acarbose (IC₅₀ = 151.1 μg/mL), the most highly prescribed α-glucosidase inhibitor on the market. When T. nilotica crude extracts were fractionated using methanol, enhanced α-glucosidase inhibitory activity was observed in general, with the highest observed α-glucosidase inhibitory activity in the 30% methanol fraction (IC₅₀ = 5.21 μg/mL). Kinetic studies further revealed a competitive reversible mechanism of inhibition by the plant extract. The phytochemical profiles of 50% ethanol extracts, aqueous extracts, and the methanolic fractions were investigated and compared using a metabolomics approach. Statistical analysis revealed significant differences in the contents of the crude extracts and fractions and potentially identified the molecules that were most responsible for these observed variations. Higher α-glucosidase inhibitory activity was associated with an enrichment of terpenoids, fatty acids, and flavonoids. Among the identified molecules, active compounds with known α-glucosidase inhibitory activity were detected, including unsaturated fatty acids, triterpenoids, and flavonoid glycosides. These results put forward T. nilotica as a therapeutic plant for type 2 diabetes and a source of α-glucosidase inhibitors.

Hypoglycemic effect of Taraxacum officinale root extract and its synergism with Radix Astragali extract

Taraxacum officinale (dandelion) and Radix Astragali are traditional medicinal and edible plants with high nutritional value. In this study, the synergistic hypoglycemic effect of DRE and Radix Astragali extract (RAE) was evaluated. Our results showed that water extract of dandelion (DRE-w), mainly containing polysaccharides (63.92 ± 1.82 mg/g), total flavonoid (2.57 ± 0.06 mg/g), total phenolic compounds (8.93 ± 0.34 mg/g), and saponins (0.54 ± 0.05 mg/g), exhibited significantly inhibitory effect on α-glucosidase and α-amylase. DRE-w and RAE had synergistic hypoglycemic effect; we found that DRE-w and its combination with RAE could relieve the state of insulin resistance in IR-HepG2 cells. The combination could more significantly increase the glucose consumption and intracellular glycogen content, and improve the activity of hexokinase and pyruvate kinase in IR-HepG2 cells. In summary, DRE and its combination with RAE can be developed as the drugs or functional foods for diabetes prevention and treatment.

Identification of α-glucosidase inhibitors from Cortex Lycii based on a bioactivity-labeling high-resolution mass spectrometry-metabolomics investigation

Cortex Lycii, as a kind of traditional Chinese medicines, have shown prospects in the prevention of diabetes and its complications. However, there is comparatively little information regarding the characterization of potentially hypoglycemic compounds derived from Cortex Lycii. In this study, we performed a global non-selective investigation of α-glucosidase inhibitors in Cortex Lycii based on a bioactivity-labeling high-resolution mass spectrometry-metabolomics method. Samples of Cortex Lycii were collected from different Chinese provinces and their ethyl acetate extracts were analyzed using an in vitro α-glucosidase inhibition assay for bioactivity-labeling. The ethyl acetate extracts were also subjected to liquid chromatography-mass spectrometry analysis and multivariate data analysis was subsequently conducted to identify correlations between the bioactivity measured from the enzyme-involved test and the profiles obtained based on high-resolution mass spectrometry. The variables contributing significantly to the separation of the more-active from the less-active samples were considered to indicate the potential target ions of active compounds. MS/MS fragment patterns and nuclear magnetic resonance analyses were used to identify the potential target ions. The developed platform mentioned above facilitated rapid identification of four α-glucosidase inhibitors, namely, N-p-trans-coumaroyltyramine (1), N-trans-caffeoyl-tyramine (2), (9R,10E,12Z)-9-hydroxy-10,12-octadecadienoic acid (3a), and (9S,10E,12Z)-9-hydroxy-10,12-octadecadienoic acid (3b) from Cortex Lycii. The α-glucosidase inhibitory activities of compounds 3a and 3b with IC₅₀ values of 1.0413±0.0551 and 1.0423±0.0049 mM, respectively, are reported here for the first time. Enzyme kinetics revealed that both 3a and 3b were non-competitive inhibitors of α-glucosidase, with Ki values of 2.20 and 2.24 mM, respectively. In short, the presented work identified compounds 3a and 3b as potential α-glucosidase inhibitors with higher inhibitory activity and a different mode of inhibition compared to the standard α-glucosidase inhibitor, acarbose. The integrated approach adopted in this study can be extended as a normalized procedure to rapidly identify active compounds, even from complex extracts, and can readily be adapted for the study of other natural products.

Fermentation of Danggui Buxue Tang, an ancient Chinese herbal mixture, together with Lactobacillus plantarum enhances the anti-diabetic functions of herbal product

Background

Danggui Buxue Tang (DBT), an ancient Chinese herbal decoction containing Astragali Radix and Angelicae Sinensis Radix at a ratio of 5: 1, is prescribed for menopausal women. Flavonoids and its flavonoid glycosides are considered as the major active ingredients within the herbal decoction; however, their amount is not controllable during the preparation. Besides, the aglycons within DBT are believed to have better gut absorption and pharmacological efficacy.

Methods

The herbal extract of DBT was fermented with Lactobacillus plantarum. The amounts of flavonoid glucosides and its aglycones in the fermented product were analyzed by using UPLC-MS/MS. In addition, in vitro assays were employed to evaluate the efficacy of the fermented DBT in regulating the activities of α-glucosidase, α-amylase and lipase, as well as their antioxidant capacity (DPPH and T-AOC assays) and anti-glycation property (BSA-methylglyoxal, BSA-fructose, and arginine-methylglyoxal models).

Results

The fermentation of DBT with L. plantarum drove a completed conversion of calycosin-7-O-β-D-glucoside and ononin to calycosin and formononetin, respectively. The chemical transformation could be probably mediated by β-glycosidase within the fermented product. Several in vitro assays corresponding to anti-diabetic functions were compared between parental DBT against its fermented product, which included the activities against α-glucosidase, α-amylase and lipase, as well as anti-oxidation and anti-glycation. The fermented DBT showed increased activities in inhibiting α-glycosidase, suppressing DPPH radical-scavenging and anti-glycation, as compared to the original herbal product.

Conclusion

These results suggested that DBT being fermented with the probiotic L. plantarum could pave a new direction for fermentation of herbal extract, as to strengthen its pharmacological properties in providing health benefits.

Chemical Profiling of Astragalus membranaceus Roots (Fish.) Bunge Herbal Preparation and Evaluation of Its Bioactivity

Astragalus membranaceus (Fish.) Bunge is a perennial herb distributed in the northern part of China, and its roots, namely, Hang qi, are included as a natural ingredient in dietary supplement formulations commonly used to treat different disorders such as respiratory infections, diabetes, and heart failure. The availability of a simple method for the determination of the quality of Astragalus herbal preparations could be a challenging issue for commercial purposes. In this study, a liquid chromatography–mass spectrometry (LC–MS)/MS based approach was used to characterize specialized metabolite recovery of 3 commercial hydroalcoholic extracts of A. membranaceus (AMG1, AMG2, AMG3) in addition to a hydroalcoholic extract of A. membranaceus root (AST). The hypoglycemic effect, cholinesterase inhibition, and antioxidant activities were also evaluated. Thirty-one compounds, of which 19 polyphenols and 12 saponins, were identified. The extracts were also quantified by using a sensitive and selective Q-Trap system for their content in flavonoids and astragalosides, selecting astragaloside I and IV as chemical markers. From our results, AMG3 preparation (Axtragyl) was the most abundant in terms of both specialized classes of metabolites, showing a fingerprint similar to that of AST. Interestingly, tested enzyme inhibition ability of flavonoids, daidzein (11) and formononetin (19), reported a higher α-glucosidase inhibition in comparison with that of acarbose used as positive control. The in silico study clarified the interactions among the molecules and the importance of having a free hydroxy group. Moreover, Axtragyl was able to exert protective effects in Caco-2 cells treated with hydrogen peroxide, confirming its ability as a potential protective agent in intestinal injury.

NMR-based metabolomic profiling of the differential concentration of phytomedicinal compounds in pericarp, skin and seeds of Momordica charantia (bitter melon)

Momordica charantia is a medicinal plant which is widely used in different traditional medicinal systems to treat several diseases. We have identified the differential distribution of phytomedicinally important metabolites in the pericarp, skin and seeds of M. charantia fruit via NMR spectroscopy. Multivariate statistical analysis showed a clustering of the metabolic profiles of seeds and pericarp, and their clear separation from the metabolic profile of the skin. The total phenolic and flavonoid content of the fruit extracts were estimated via bioassays, the radical scavenging activity was estimated via in vitro DPPH and ABTS assays and an inhibitory activity test of α-glucosidase was also performed. The pericarp and seeds contained significant amounts of phenolic compounds and flavonoids, indicating that they are a good source for antioxidants. The skin contained a significantly higher amount of phytosterols such as Charantin and momordicine, which are known to correlate with antidiabetic activity.

Anil Kumar N, Sharopov F, Ramírez-Alarcón K, Ruiz-Ortega A, Abdulmajid Ayatollahi S, Valere Tsouh Fokou P, Kobarfard F, Amiruddin Zakaria Z, Iriti M, Taheri Y, Martorell M, Sureda A, N. Setzer W, Durazzo A, Lucarini M, Santini A, Capasso R, Adrian Ostrander E, -ur-Rahman A, Iqbal Choudhary M, C. Cho W, Sharifi-Rad J. Antidiabetic Potential of Medicinal Plants and Their Active Components

Diabetes mellitus is one of the major health problems in the world, the incidence and associated mortality are increasing. Inadequate regulation of the blood sugar imposes serious consequences for health. Conventional antidiabetic drugs are effective, however, also with unavoidable side effects. On the other hand, medicinal plants may act as an alternative source of antidiabetic agents. Examples of medicinal plants with antidiabetic potential are described, with focuses on preclinical and clinical studies. The beneficial potential of each plant matrix is given by the combined and concerted action of their profile of biologically active compounds.