Potential of Polygonum cuspidatum Root as an Antidiabetic Food: Dual High-Resolution α-Glucosidase and PTP1B Inhibition Profiling Combined with HPLC-HRMS and NMR for Identification of Antidiabetic Constituents

The genus Polygonum: An updated comprehensive review of its ethnomedicinal, phytochemical, pharmacological activities, toxicology, and phytopharmaceutical formulation

Polygonum is a plant genus that includes annual and perennial species and is found at various temperatures, from northern temperate regions to tropical and subtropical areas. The genus Polygonum has been used for centuries for various disorders, including hypertension, intestinal and stomach pain, dysuria, jaundice, toothaches, skin allergies, hemorrhoids, cardiac disorders, kidney stones, hemostasis, hyperglycemia, and others. Various databases, including Google Scholar, Scifinder, ScienceDirect, PubMed, Scopus, ResearchGate, and Web of Science, were utilized to collect pertinent scientific literature data. According to bibliographic studies, the Polygonum genus possesses various compounds from different families, including phenolic acids (gallic acid, caffeic acid, quinic acid, p-coumaric acid, ferulic acid, protocatechuic acid, chlorogenic acid, and many other compounds), flavonoids (quercetin, catechin, epicatechin, quercitrin, kaempferol, myricetin, etc.), tannins, stilbenes (polydatin and resveratrol), terpenes (α-pinene, β-caryophyllene and β-caryophyllene oxide, bisabolene, β-farnesene, etc.), fatty acids (decanoic acid, lauric acid, linoleic acid, oleic acid, palmitic acid, stearic acid, dodecanoic acid), polysaccharides, and others. Various chemical and biological activities (in vitro and in vivo), such as antioxidant, antimicrobial, anticancer, antitumor, anti-inflammatory, antidiabetic, antiparasitic, hepatoprotective, neuropharmacological, gastroprotective, diuretic, antipyretic, and others, have been described in several biological studies involving this species. An updated summary of Polygonum species and their ethnomedicinal, phytochemical, toxicological, pharmacological, and phytopharmaceutical formulations is necessary. Considering the numerous potentialities of the Polygonum species and their wide-ranging use, it is extremely essential to provide knowledge by compiling the accessible literature to identify the topics of intense investigation and the main gaps to better design future studies. The objective of this review is to give readers a better understanding, greater comprehension, and in-depth knowledge of the genus Polygonum's traditional applications, phytochemistry, pharmacology, toxicological features, and galenic formulation. Several species of this genus have been detailed in this review, including those that were frequently used in traditional medicine (P. minus, P. aviculare, P. hydropiper, P. cuspidatum, and P. multiflorum) and many of the genus' therapeutic species, like P. equisetiforme, which do not get enough attention.

Efficient screening of pancreatic lipase inhibitors from Rheum palmatum by affinity ultrafiltration-high-performance liquid chromatography combined with high-resolution inhibition profiling

INTRODUCTION

Pancreatic lipase is one of the most important key targets in the treatment of obesity. Inhibition of pancreatic lipase can effectively reduce lipid absorption and treat obesity and other related metabolic disorders.

OBJECTIVES

The goal of this study is the efficient screening of pancreatic lipase inhibitors in the root and rhizome of Rheum palmatum using affinity ultrafiltration-high-performance liquid chromatography (AUF-HPLC) combined with high-resolution inhibition profiling (HRIP).

METHODS

Potential pancreatic lipase ligands and pancreatic lipase inhibitors in ethyl acetate fraction of R. palmatum were screened using AUF-HPLC and HRIP, respectively. All screened compounds were identified by HPLC- quadrupole time-of-flight (Q-TOF)/MS. Eight compounds were screened out by both AUF-HPLC and HRIP, and six compounds were screened out by either AUF-HPLC or HRIP alone. The pancreatic lipase inhibitory activities of all screened compounds were verified by enzyme inhibition assay and molecular docking.

RESULTS

Five new potent pancreatic lipase inhibitors were discovered, namely procyanidin B5 3,3'-di-O-gallate (IC50 = 0.06 ± 0.01 μM), 1,6-di-O-galloyl-2-O-cinnamoyl-β-D-glucoside (IC50 = 12.83 ± 0.67 μM), 1-O-(1,3,5-trihydroxy)phenyl-2-O-galloyl-6-O-cinnamoyl-β-D-glucoside (IC50 = 17.84 ± 1.33 μM), 1,2-di-O-galloyl-6-O-cinnamoyl-β-D-glucoside (IC50 = 18.39 ± 1.52 μM), and 4-(4'-hydroxyphenyl)-2-butanone-4'-O-β-D-(2"-O-galloyl-6"-O-cinnamoyl)-glucoside (IC50 = 2.91 ± 0.40 μM). It was found that procyanidin B5 3,3'-di-O-gallate showed higher pancreatic lipase inhibitory activity than the positive control orlistat (IC50 = 0.12 ± 0.02 μM).

CONCLUSION

The combination of affinity ultrafiltration-high-performance liquid chromatography (AUF-HPLC) and high-resolution inhibition profiling (HRIP) could reduce the risk of false-negative screening and missed screening and could achieve more efficient screening of bioactive compounds in complex natural products.

Natural Products and Diabetes: (-)-Epicatechin and Mechanisms Involved in the Regulation of Insulin Sensitivity

Type 2 diabetes (T2D) is a disease that occurs when cells do not respond normally to insulin, a condition called insulin resistance, which leads to high blood glucose levels. Although it can be treated pharmacologically, dietary habits beyond carbohydrate restriction can be highly relevant in the management of T2D. Emerging evidence supports the possibility that natural products (NPs) could contribute to managing blood glucose or counteract the undesirable effects of hyperglycemia and insulin resistance. This chapter summarizes the relevant preclinical evidence involving the flavonoid (-)-epicatechin (EC) in the optimization of glucose homeostasis, reducing insulin resistance and/or diabetes-associated disorders. Major effects of EC are observed on (i) intestinal functions, including digestive enzymes, glucose transporters, microbiota, and intestinal permeability, and (ii) redox homeostasis, including oxidative stress and inflammation. There is still a need for further clinical studies to confirm the in vitro and rodent data, allowing recommendations for EC, particularly in prediabetic and T2D patients. The collection of similar data and the lack of clinical evidence for EC is also applicable to other NPs.

Advances for pharmacological activities of Polygonum cuspidatum - A review

CONTEXT

Polygonum cuspidatum Sieb. et Zucc (Polygonaceae), the root of which is included in the Chinese Pharmcopoeia under the name 'Huzhang', has a long history as a medicinal plant and vegetable. Polygonum cuspidatum has been used in traditional Chinese medicine for the treatment of inflammation, hyperlipemia, etc.

OBJECTIVE

This article reviews the pharmacological action and the clinical applications of Polygonum cuspidatum and its extracts, whether in vivo or in vitro. We also summarized the main phytochemical constituents and pharmacokinetics of Polygonum cuspidatum and its extracts.

METHODS

The data were retrieved from major medical databases, such as CNKI, PubMed, and SinoMed, from 2014 to 2022. Polygonum cuspidatum, pharmacology, toxicity, clinical application, and pharmacokinetics were used as keywords.

RESULTS

The rhizomes, leaves, and flowers of Polygonum cuspidatum have different phytochemical constituents. The plant contains flavonoids, anthraquinones, and stilbenes. Polygonum cuspidatum and the extracts have anti-inflammatory, antioxidation, anticancer, heart protection, and other pharmacological effects. It is used in the clinics to treat dizziness, headaches, traumatic injuries, and water and fire burns.

CONCLUSIONS

Polygonum cuspidatum has the potential to treat many diseases, such as arthritis, ulcerative colitis, asthma, and cardiac hypertrophy. It has a broad range of medicinal applications, but mainly focused on root medication; its aerial parts should receive more attention. Pharmacokinetics also need to be further investigated.

Role of anthraquinones in combating insulin resistance

Insulin resistance presents a formidable public health challenge that is intricately linked to the onset and progression of various chronic ailments, including diabetes, cardiovascular disease, hypertension, metabolic syndrome, nonalcoholic fatty liver disease, and cancer. Effectively addressing insulin resistance is paramount in preventing and managing these metabolic disorders. Natural herbal remedies show promise in combating insulin resistance, with anthraquinone extracts garnering attention for their role in enhancing insulin sensitivity and treating diabetes. Anthraquinones are believed to ameliorate insulin resistance through diverse pathways, encompassing activation of the AMP-activated protein kinase (AMPK) signaling pathway, restoration of insulin signal transduction, attenuation of inflammatory pathways, and modulation of gut microbiota. This comprehensive review aims to consolidate the potential anthraquinone compounds that exert beneficial effects on insulin resistance, elucidating the underlying mechanisms responsible for their therapeutic impact. The evidence discussed in this review points toward the potential utilization of anthraquinones as a promising therapeutic strategy to combat insulin resistance and its associated metabolic diseases.

Acyl-quinic acids from the root bark of Acanthopanax gracilistylus and their inhibitory effects on neutrophil elastase and cyclooxygenase-2 in vitro

Eleven new acyl-quinic acids (AQAs) 1a-9, and 18 known AQAs 10-27 were isolated from the root bark of Acanthopanax gracilistylus W. W. Smith (Acanthopanacis Cortex). The planar structures of 1a-9 were determined based on their HR-ESIMS, IR, and NMR data. The absolute configurations of 1a-6 were identified by comparing the experimental and the calculated electronic circular dichroism (ECD) spectra. This is the first report of the isolation of AQAs from Acanthopanacis Cortex. Notably, 1a-6 were determined as unusual oxyneolignan-(-)-quinic acids heterodimers, representing a new class of natural products. The inhibitory activities of 1a-27 on neutrophil elastase (NE) and cyclooxygenase-2 (COX-2) were studied in vitro, and the results indicated they possessed significant inhibitory activities on COX-2. Among them, the IC50 values of 1a-9 were 0.63±0.014, 0.75±0.028, 0.15±0.023, 0.63±0.016, 0.30±0.013, 35.63±4.600, 8.70±1.241, 16.51±0.480, 0.69±0.049, 0.39±0.017, and 0.26±0.080 μM, respectively. This study represents the inaugural disclosure of the anti-COX-2 constituents found in Acanthopanacis Cortex, thereby furnishing valuable insights into the exploration of novel COX-2 inhibitors derived from natural reservoirs.

Pluronic-F-127-Passivated SnO2 Nanoparticles Derived by Using Polygonum cuspidatum Root Extract: Synthesis, Characterization, and Anticancer Properties

Nanotechnology has emerged as the most popular research topic with revolutionary applications across all scientific disciplines. Tin oxide (SnO₂) has been gaining considerable attention lately owing to its intriguing features, which can be enhanced by its synthesis in the nanoscale range. The establishment of a cost-efficient and ecologically friendly procedure for its production is the result of growing concerns about human well-being. The novelty and significance of this study lie in the fact that the synthesized SnO₂ nanoparticles have been tailored to have specific properties, such as size and morphology. These properties are crucial for their applications. Moreover, this study provides insights into the synthesis process of SnO₂ nanoparticles, which can be useful for developing efficient and cost-effective methods for large-scale production. In the current study, green Pluronic-coated SnO₂ nanoparticles (NPs) utilizing the root extracts of Polygonum cuspidatum have been formulated and characterized by several methods such as UV-visible, Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray (EDAX), transmission electron microscope (TEM), field emission-scanning electron microscope (FE-SEM), X-ray diffraction (XRD), photoluminescence (PL), and dynamic light scattering (DLS) studies. The crystallite size of SnO₂ NPs was estimated to be 45 nm, and a tetragonal rutile-type crystalline structure was observed. FESEM analysis validated the NPs' spherical structure. The cytotoxic potential of the NPs against HepG2 cells was assessed using the in vitro MTT assay. The apoptotic efficiency of the NPs was evaluated using a dual-staining approach. The NPs revealed substantial cytotoxic effects against HepG2 cells but failed to exhibit cytotoxicity in different liver cell lines. Furthermore, dual staining and flow cytometry studies revealed higher apoptosis in NP-treated HepG2 cells. Nanoparticle treatment also inhibited the cell cycle at G0/G1 stage. It increased oxidative stress and promoted apoptosis by encouraging pro-apoptotic protein expression in HepG2 cells. NP treatment effectively blocked the PI3K/Akt/mTOR axis in HepG2 cells. Thus, green Pluronic-F-127-coated SnO₂ NPs exhibits enormous efficiency to be utilized as an talented anticancer agent.

Ultra-high performance liquid chromatography-quadrupole/time-of-flight mass spectrometry-based lipidomics reveals key lipid molecules as potential therapeutic targets of Polygonum cuspidatum against hyperlipidemia in a hamster model

Polygonum cuspidatum is a homology of traditional medicine and functional food widely distributed around the world. Our previous study on the hyperlipidemic animal model demonstrated that Polygonum cuspidatum was effective in ameliorating hyperlipidemia, which is characterized by lipid disorders. Herein, the regulatory effect of Polygonum cuspidatum on lipid metabolism needs to be known if its hypolipidemic mechanism is desired to clarify. In this study, an ultra-high performance liquid chromatography-quadrupole/time-of-flight mass spectrometry-based lipidomic strategy was first applied to investigate the lipidomic patterns of high-fat diet-induced hyperlipidemic hamsters when treated with Polygonum cuspidatum. The results showed that Polygonum cuspidatum improved the lipidomic profile of hyperlipidemia. A total of 65 differential lipids related to the hypolipidemic effect of Polygonum cuspidatum were screened out and identified, and these differential lipids covered various categories, such as phosphatidylcholines, phosphatidylethanolamines, triacylglycerols, sphingomyelins and so on. Orally administrated Polygonum cuspidatum restored these differential lipids back to normal or nearly normal levels. This study adopted lipidomics to reveal the key lipid molecules as potential therapeutic targets of Polygonum cuspidatum against hyperlipidemia, which would provide a scientific basis for its clinical application.

A Strategy for Pinpointing Natural Bioactive Components Using Two-Dimensional Bioassay Profilings Combined with Comprehensive Two-Dimensional Countercurrent Chromatography × High-Performance Liquid Chromatography

Inspired by the interpretation of two-dimensional (2D) nuclear magnetic resonance spectra, an efficient strategy was proposed for pinpointing bioactive components from complex natural products. An off-line comprehensive countercurrent chromatography (CCC) × high-performance liquid chromatography (HPLC) was employed to achieve a 2D chemical chromatogram, and 2D bioassay profilings were obtained from bioassays of the eluent of the first dimension (¹D) CCC and the eluent of the second dimension (²D) HPLC. Then 2D chemical chromatograms and 2D bioassay profilings were matched for pinpointing bioactive natural components from complex matrices. Thus, bioactive components in a complex matrix could be efficiently analyzed, separated, and bioactivity-determined. This experimental scheme was successfully demonstrated with a traditional medicinal herb Polygonum cuspidatum Sieb. et Zucc. The feasibility of this 2D strategy was verified with tyrosinase inhibition assay, α-glucosidase inhibition assay, DPPH radical scavenging assay, and ABTS^•+ decolorization assay. Eight natural inhibitors were successfully pinpointed and identified from P. cuspidatum. Both pieceid-2″-O-gallate (10) and vanicoside B (20) were screened and identified as natural tyrosinase inhibitors for the first time. Meanwhile, vanicoside B (20) was also found as the strongest α-glucosidase inhibitor among all the isolated components. Most of the compounds exhibited much higher radical scavenging activities. Compared with traditional methodology based on one-dimensional chromatographic separation, the present 2D strategy would be more precise, efficient, and convenient to screen and separate bioactive compounds from complex matrices.

In Vitro and in Silico Analysis of Phytochemicals From Fallopia dentatoalata as Dual Functional Cholinesterase Inhibitors for the Treatment of Alzheimer’s Disease

Current studies have found that butyrylcholinesterase (BuChE) replaces the biological function of acetylcholinesterase (AChE) in the late stage of Alzheimer’s disease. Species in the genus of Fallopia, rich in polyphenols with diverse chemical structures and significant biological activities, are considered as an important resource for screening natural products to against AD. In this study, thirty-four compounds (1–34) were isolated from Fallopia dentatoalata (Fr. Schm.) Holub, and their inhibitory effects against AChE and BuChE were assessed. Compounds of the phenylpropanoid sucrose ester class emerged as the most promising members of the group, with 31–33 displaying moderate AChE inhibition (IC50 values ranging from 30.6 ± 4.7 to 56.0 ± 2.4 µM) and 30–34 showing potential inhibitory effects against BuChE (IC50 values ranging from 2.7 ± 1.7 to 17.1 ± 3.4 µM). Tacrine was used as a positive control (IC50: 126.7 ± 1.1 in AChE and 5.5 ± 1.7 nM in BuChE). Kinetic analysis highlighted compounds 31 and 32 as non-competitive inhibitors of AChE with Ki values of ∼30.0 and ∼34.4 µM, whilst 30–34 were revealed to competitively inhibit BuChE with Ki values ranging from ∼1.8 to ∼17.5 µM. Molecular binding studies demonstrated that 30–34 bound to the catalytic sites of BuChE with negative binding energies. The strong agreement between both in vitro and in silico studies highlights the phenylpropanoid sucrose esters 30–34 as promising candidates for use in future anti-cholinesterase therapeutics against Alzheimer’s disease.

Chemical Characterization, α-Glucosidase, α-Amylase and Lipase Inhibitory Properties of the Australian Honey Bee Propolis

The use of functional foods and nutraceuticals as a complementary therapy for the prevention and management of type 2 diabetes and obesity has steadily increased over the past few decades. With the aim of exploring the therapeutic potentials of Australian propolis, this study reports the chemical and biological investigation of a propolis sample collected in the Queensland state of Australia which exhibited a potent activity in an in vitro α-glucosidase inhibitory screening. The chemical investigation of the propolis resulted in the identification of six known prenylated flavonoids including propolins C, D, F, G, H, and solophenol D. These compounds potently inhibited the α-glucosidase and two other enzymes associated with diabetes and obesity, α-amylase, and lipase on in vitro and in silico assays. These findings suggest that this propolis is a potential source for the development of a functional food to prevent type 2 diabetes and obesity. The chemical analysis revealed that this propolis possessed a chemical fingerprint relatively similar to the Pacific propolis found in Okinawa (South of Japan), Taiwan, and the Solomon Islands. This is the first time the Pacific propolis has been identified in Australia.

Novel Functional Food from an invasive species Polygonum cuspidatum: Safety evaluation, Chemical Composition, and Hepatoprotective Effects

Accidentally, we found that the shoots of Polygonum cuspidatum (SPC) have been consumed for centuries as a traditional vegetable in the Shennongjia region of China. Local residents believe that SPC has biological effects such as antibacterial, anti-aging, and antioxidant. To provide scientific support for the use of SPC as a functional food, SPC was evaluated in terms of safety, chemical composition, antioxidant activity both in vivo and in vitro. In the first, SPC exhibited no adverse cytotoxic effects or acute toxicity in mice. Then the chemical composition of SPC was determined by UHPLC-ESI-QTOF-MS/MS. 22 compounds were identified from the SPC extracts, including phenolic, flavonoid, stilbene, and anthraquinone. Finally, an acute ethanol-induced oxidative stress model in mice showed hepatoprotective effects. In brief, our study indicated that SPC is a safe, multi-functional food with antioxidant and hepatoprotective activities. Importantly, the consumption of SPC as a functional food provides a novel strategy of efficient utilization of the invasive plant.

Inhibitory effects of phenolic glycosides from Trollius chinensis Bunge on α-glucosidase: inhibition kinetics and mechanism

Two undescribed phenolic glycosides, trochinenols B-C (1-2), together with four known analogues (3-6), were isolated from the functional tea Trollius chinensis Bunge and their α-glucosidase inhibitory kinetics and mechanism were...

Approaches to Decrease Hyperglycemia by Targeting Impaired Hepatic Glucose Homeostasis Using Medicinal Plants

Liver plays a pivotal role in maintaining blood glucose levels through complex processes which involve the disposal, storage, and endogenous production of this carbohydrate. Insulin is the hormone responsible for regulating hepatic glucose production and glucose storage as glycogen, thus abnormalities in its function lead to hyperglycemia in obese or diabetic patients because of higher production rates and lower capacity to store glucose. In this context, two different but complementary therapeutic approaches can be highlighted to avoid the hyperglycemia generated by the hepatic insulin resistance: 1) enhancing insulin function by inhibiting the protein tyrosine phosphatase 1B, one of the main enzymes that disrupt the insulin signal, and 2) direct regulation of key enzymes involved in hepatic glucose production and glycogen synthesis/breakdown. It is recognized that medicinal plants are a valuable source of molecules with special properties and a wide range of scaffolds that can improve hepatic glucose metabolism. Some molecules, especially phenolic compounds and terpenoids, exhibit a powerful inhibitory capacity on protein tyrosine phosphatase 1B and decrease the expression or activity of the key enzymes involved in the gluconeogenic pathway, such as phosphoenolpyruvate carboxykinase or glucose 6-phosphatase. This review shed light on the progress made in the past 7 years in medicinal plants capable of improving hepatic glucose homeostasis through the two proposed approaches. We suggest that Coreopsis tinctoria, Lithocarpus polystachyus, and Panax ginseng can be good candidates for developing herbal medicines or phytomedicines that target inhibition of hepatic glucose output as they can modulate the activity of PTP-1B, the expression of gluconeogenic enzymes, and the glycogen content.

Potential antidiabetic phytochemicals in plant roots: a review of in vivo studies

Background

Medicinal plants are used to treat various disorders, including diabetes, globally in a range of formulations. While attention has mainly been on the aerial plant parts, there are only a few review studies to date that are focused on the natural constituents present in the plant roots with health benefits. Thus, the present study was performed to review in vivo studies investigating the antidiabetic potential of the natural compounds in plant roots.

Methods

We sorted relevant data in 2001-2019 from scientific databases and search engines, including Web of Knowledge, PubMed, ScienceDirect, Medline, Reaxys, and Google Scholar. The class of phytochemicals, plant families, major compounds, active constituents, effective dosages, type of extracts, time of experiments, and type of diabetic induction were described.

Results

In our literature review, we found 104 plants with determined antidiabetic activity in their root extracts. The biosynthesis pathways and mechanism of actions of the most frequent class of compounds were also proposed. The results of this review indicated that flavonoids, phenolic compounds, alkaloids, and phytosteroids are the most abundant natural compounds in plant roots with antidiabetic activity. Phytochemicals in plant roots possess different mechanisms of action to control diabetes, including inhibition of α-amylase and α-glucosidase enzymes, oxidative stress reduction, secretion of insulin, improvement of diabetic retinopathy/nephropathy, slow the starch digestion, and contribution against hyperglycemia.

Conclusion

This review concludes that plant roots are a promising source of bioactive compounds which can be explored to develop against diabetes and diabetes-related complications.

Graphical abstract

New Approaches on Japanese Knotweed (Fallopia japonica) Bioactive Compounds and Their Potential of Pharmacological and Beekeeping Activities: Challenges and Future Directions

Known especially for its negative ecological impact, Fallopia japonica (Japanese knotweed) is now considered one of the most invasive species. Nevertheless, its chemical composition has shown, beyond doubt, some high biological active compounds that can be a source of valuable pharmacological potential for the enhancement of human health. In this direction, resveratrol, emodin or polydatin, to name a few, have been extensively studied to demonstrate the beneficial effects on animals and humans. Thus, by taking into consideration the recent advances in the study of Japanese knotweed and its phytochemical constituents, the aim of this article is to provide an overview on the high therapeutic potential, underlining its antioxidant, antimicrobial, anti-inflammatory and anticancer effects, among the most important ones. Moreover, we describe some future directions for reducing the negative impact of Fallopia japonica by using the plant for its beekeeping properties in providing a distinct honey type that incorporates most of its bioactive compounds, with the same health-promoting properties.

Hepatotoxicity or hepatoprotection of emodin? Two sides of the same coin by 1H-NMR metabolomics profiling

Emodin is the major anthraquinone component of many important traditional Chinese herbs, such as Rheum palmatum L. and Polygonum multiflorum Thunb. They have been popular health products but recently aroused concerns about their hepatotoxicity, which are believed to be arising from the contained anthraquinones, such as emodin. However, emodin exerts potent hepatoprotective ability, such as anti-fibrotic, anti-oxidative, and anti-inflammatory effects. In this study, 1H NMR based metabolomics approach, complemented with histopathological observation, biochemical measurements, western blotting analysis and real-time quantitative PCR (RT-qPCR), was applied to interpret the paradox of emodin (30 mg/kg, 10 mg/kg BW) using both healthy mice (male, ICR) and chronic CCl4-injured mice (0.1 mL/kg, 0.35% CCl4, 3 times a week for a month). Emodin exerted a weight loss property associated with its lipid-lowing effects, which helped alleviate CCl4-induced steatosis. Emodin effectively ameliorated CCl4-induced oxidative stress and energy metabolism dysfunction in mice liver via regulating glucose, lipid and amino acid metabolism, and inhibited excessive inflammatory response. In healthy mice, emodin only exhibited hepatoxicity on high-dosage by disturbing hepatic anti-oxidant homeostasis, especially GSH and xanthine metabolism. This integrated metabolomics approach identified the bidirectional potential of emodin, which are important for its rational use.

Integrated multiplatform-based metabonomics and network analysis to explore the mechanism of Polygonum cuspidatum on hyperlipidemia

Hyperlipidemia is a major risk factor and pathological basis for cardiovascular diseases. Polygonum cuspidatum (HZ), a famous traditional Chinese medicine, is frequently used to treat hyperlipidemia. However, little is known about its underlying mechanism. Herein, an integrated approach combining multiplatform-based metabonomics and network analysis was adopted to elucidate the ameliorative mechanism of HZ on hyperlipidemia. The global metabolomic characters of HZ on hyperlipidemia were investigated by GC-MS and LC-MS based metabonomics. Significant metabonomic alterations were observed in hyperlipidemic group, which could be restored by HZ supplementation. Furthermore, the drug-ingredients-target-metabolic pathway network was constructed, and the result indicated that HZ exhibited hypolipidemic efficacy through resveratrol, polydatin, torachrysone-8-O-β-D-(6'-oxayl)-glucoside, physciondiglucoside, (+)-catechin, β-sitosterol, quercetin, luteolin and physovenine acting on phospholipase A2, unspecific monooxygenase, arachidonate 15-lipoxygenase, aromatic-L-amino-acid decarboxylase, alcohol dehydrogenase and triacylglycerol lipase. In conclusion, this study explored potential mechanism of HZ on hyperlipidemia with the aid of the integrated approach combining multiplatform-based metabonomics and network analysis, which might provide a theoretical basis for the clinical application of HZ.

Antioxidant and Antidiabetic Activity of Proanthocyanidins from Fagopyrum dibotrys

Proanthocyanidins are natural glycosidase inhibitors with excellent antioxidant activity. This study aims to search for a new source of proanthocyanidins for the prevention and treatment of type 2 diabetes with higher content and better activity and get their structure elucidated. First, the total proanthocyanidins contents (TOPCs), antioxidant activity, antidiabetic activity of seven common Polygonaceae plants were analyzed and compared. Then proanthocyanidins from the rhizome of Fagopyrum dibotrys were purified, and the detailed structure was comprehensively analyzed by ultraviolet visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FT-IR), ¹³C nuclear magnetic resonance spectroscopy (¹³C NMR), reversed-phase high-performance liquid chromatography-electrospray mass spectrometry (RP-HPLC-ESI-MS), and matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS). The rhizome of F. dibotrys showed the highest TOPCs, the strongest antioxidant, and antidiabetic activities; the TOPCs, antioxidant and antidiabetic activities were all very significantly positively correlated. Proanthocyanidins purified from the rhizome of F. dibotrys showed better antidiabetic activity than grape seed proanthocyanidins (GsPs). Seventy-two proanthocyanidins from trimer to undecamer with a mean degree of polymerization (mDP) of about 5.02 ± 0.21 were identified with catechin and epicatechin as the dominant monomers. Conclusion: Proanthocyanidins are the main antioxidant and antidiabetic active substances of F. dibotrys and are expected to be developed into potential antioxidant and hypoglycemic products.

Bioactive amides from Polygonum cuspidatum

One pair of new amides enantiomers (1a and 1b) and two known amides were isolated from the rhizomes of Polygonum cuspidatum. Their structures were established using UV, IR, HRESIMS, and NMR data. Notably, compound 1 possesses unique C-C connection between feruloyltyramine and resveratrol. Their absolute configurations were determined by the ECD method. All compounds were evaluated for their α-glucosidase inhibitory activity and compounds 2 and 3 showed significant inhibitory activity with IC₅₀ values of 2.82 and 13.06 μmol/L, respectively (positive control acarbose, IC₅₀ 385 μmol/L).

(-)-Epicatechin-An Important Contributor to the Antioxidant Activity of Japanese Knotweed Rhizome Bark Extract as Determined by Antioxidant Activity-Guided Fractionation

The antioxidant activities of Japanese knotweed rhizome bark extracts, prepared with eight different solvents or solvent mixtures (water, methanol, 80% methanol_(aq), acetone, 70% acetone_(aq), ethanol, 70% ethanol_(aq), and 90% ethyl acetate_(aq)), were determined using a 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical-scavenging assay. Low half maximal inhibitory concentration (IC₅₀) values (2.632–3.720 µg mL⁻¹) for all the extracts were in the range of the IC₅₀ value of the known antioxidant ascorbic acid at t₀ (3.115 µg mL⁻¹). Due to the highest extraction yield (~44%), 70% ethanol_(aq) was selected for the preparation of the extract for further investigations. The IC₅₀ value calculated for its antioxidant activity remained stable for at least 14 days, while the IC₅₀ of ascorbic acid increased over time. The stability study showed that the container material was of great importance for the light-protected storage of the ascorbic acid_(aq) solution in a refrigerator. Size exclusion–high-performance liquid chromatography (SEC-HPLC)–UV and reversed phase (RP)-HPLC-UV coupled with multistage mass spectrometry (MSⁿ) were developed for fractionation of the 70% ethanol_(aq) extract and for further compound identification, respectively. In the most potent antioxidant SEC fraction, determined using an on-line post-column SEC-HPLC-DPPH assay, epicatechin, resveratrol malonyl hexoside, and its in-source fragments (resveratrol and resveratrol acetyl hexoside) were tentatively identified by RP-HPLC-MSⁿ. Moreover, epicatechin was additionally confirmed by two orthogonal methods, SEC-HPLC-UV and high-performance thin-layer chromatography (HPTLC) coupled with densitometry. Finally, the latter technique enabled the identification of (−)-epicatechin. (−)-Epicatechin demonstrated potent and stable time-dependent antioxidant activity (IC₅₀ value ~1.5 µg mL⁻¹) for at least 14 days.

Discovery of 5-(3-bromo-2-(2,3-dibromo-4,5-dimethoxybenzyl)-4,5-dimethoxybenzylidene)thiazolidine-2,4-dione as a novel potent protein tyrosine phosphatase 1B inhibitor with antidiabetic properties

Protein tyrosine phosphatase 1B (PTP1B) is a well-validated target in therapeutic interventions for type 2 diabetes mellitus (T2DM), however, PTP1B inhibitors containing negatively charged nonhydrolyzable pTyr mimetics are difficult to convert to the corresponding in vivo efficacy owing to poor cell permeability and oral bioavailability. In this work, molecules bearing less acidic heterocycle 2,4-thiazolidinedione and hydantoin were designed, synthesized and evaluated for PTP1B inhibitory potency, selectivity and in vivo antidiabetic efficacy. Among them, compound 5a was identified as a potent PTP1B inhibitor (IC₅₀ = 0.86 μM) with 5-fold selectivity over the highly homologous TCPTP. Long-term oral administration of 5a at a dose of 50 mg/kg not only significantly reduced blood glucose levels, triglycerides (TG) and low-density lipoprotein cholesterol (LDL-C) levels but also ameliorated insulin sensitivity in diabetic BKS db mice. Moreover, 5a enhanced the insulin-stimulated phosphorylation of IRβ, IRS-1 and Akt in C2C12 myotubes. A histopathological evaluation of liver and pancreas demonstrated that 5a increased liver glycogen storage and improved islet architecture with more β-cells and fewer α-cells in diabetic mice. Thus, our work demonstrated that compound 5a could serve as a lead compound for the discovery of new antidiabetic drugs.

Off-line multidimensional high performance thin-layer chromatography for fractionation of Japanese knotweed rhizome bark extract and isolation of flavan-3-ols, proanthocyanidins and anthraquinones

A methodology based on off-line multidimensional thin-layer chromatography was developed for isolation of several secondary metabolites from bark of Japanese knotweed (Fallopia japonica Houtt.) rhizomes. Successive fractionation steps using PLC silica gel and HPTLC silica gel or HPTLC cellulose plates in combination with various developing solvents enabled isolation of (+)-catechin, (-)-epicatechin, (-)-epicatechin gallate, procyanidin B1, procyanidin B2, procyanidin B3, proanthocyanidin B dimer gallate, emodin, emodin-8-O-glucoside and emodin-8-O-malonyl-glucoside. Their identity was confirmed by HPTLC, HPTLC-MSⁿ and for most of them also by ¹H NMR and 2D NMR analyses. To the best of our knowledge emodin-8-O-malonyl-glucoside, procyanidins B1 and B2 were for the first time isolated from this plant material. HPTLC and HPTLC-MSⁿ analyses were also performed as support of fractionation/isolation process, leading to first detection of some compounds in bark of Japanese knotweed rhizomes and Japanese knotweed rhizomes in general: procyanidins B1 and B2, methyl derivatives of emodin bianthrone and emodin bianthrone-hexose, resveratrol-malonyl-hexoside and taxifolin derivatives. Characterization of flavan-3-ols and proanthocyanidins was facilitated by post-chromatographic derivatization of the corresponding chromatographic zones with 4-dimethylaminocinnamaldehyde (DMACA) detection reagent.

POCU1b, the n-Butanol Soluble Fraction of Polygoni Cuspidati Rhizoma et Radix, Attenuates Obesity, Non-Alcoholic Fatty Liver, and Insulin Resistance via Inhibitions of Pancreatic Lipase, cAMP-Dependent PDE Activity, AMPK Activation, and SOCS-3 Suppression

This study investigated the effects of the n-BuOH soluble fraction of Polygoni Cuspidati 80% ethanol extract (POCU1b) on high-fat diet (HFD)-induced obesity, non-alcoholic fatty liver (NAFL), and insulin resistance (IR) to find a safe and more effective agent. HPLC profiling of POCU1b identified seven marker compounds. POCU1b increased glycerol release, cyclic adenosine monophosphate (cAMP) level, and inhibited phosphodiesterase (PDE) activity. Seven weeks of POCU1b treatment decreased body weight gain, weight and adipocyte size in fat tissues, serum lipids, and triglyceride and lipid droplets in the livers of HFD-fed rats. POCU1b improved blood glucose, insulin sensitivity, and impaired insulin secretion in the pancreas. Further, POCU1b ameliorated adiponectin, leptin, IL-6 and TNF-α levels, increased AMPK and p-ACC expression, activated CPT-1 activity, and suppressed FAS mRNA, SOCS-3 protein expression, and NF-κB DNA-binding activity. When compared with the Xenical^®-treated group, a positive group, the action of POCU1b on body weight was more effective than that of Xenical. POCU1b did not show side effects, such as oily spotting and loss of appetite. These results suggest that POCU1b possesses therapeutic or preventive potential for obesity, NAFL and IR via inhibitions of pancreatic lipase and cAMP-dependent PDE activity, AMPK activation, and SOCS-3 suppression, without oily spotting and loss of appetite.

Lignan Constituents from the Fruits of Viburnum macrocephalum f. keteleeri and Their α-Amylase, α-Glucosidase, and Protein Tyrosine Phosphatase 1B Inhibitory Activities

Eight previously undescribed lignan glycosides, viburmacrosides A-H (1-8), and seven known analogues (9-15) were isolated from Viburnum macrocephalum f. keteleeri fruits through bioactivity-guided fractionation. Their structures and absolute configurations were elucidated by extensive spectroscopic analyses and chemical evidence. Using the well-recognized carbohydrate-hydrolyzing enzymes α-amylase and α-glucosidase, as well as the promising protein tyrosine phosphatase 1B (PTP1B), as inhibitory targets, all isolated compounds were tested for their antidiabetic potential in vitro. Compound 4 displayed potent inhibitory activities with IC₅₀ values of 9.9 ± 0.6 and 8.9 ± 0.5 μM against α-glucosidase and PTP1B, respectively. The enzymatic kinetics results suggested that compound 4 competitively inhibited α-glucosidase while it suppressed α-amylase and PTP1B in the mixed-type manner. These findings supported that V. macrocephalum f. keteleeri fruits may be a new functional food resource with antidiabetic potential.

Natural PTP1B Inhibitors From Polygonum cuspidatum and Their 2-NBDG Uptake Stimulation

Ten active principles (compounds 1-10) have been isolated following protein tyrosine phosphatase 1B (PTP1B) assay-guided fractionation of the methanol extract of the root of Polygonum cuspidatum. The chemical structures of the compounds were characterized mainly by nuclear magnetic resonance (NMR) spectroscopic and physicochemical data. This is the first time that 9,10-anthraquinones (compounds 5-6) have been isolated from P. cuspidatum, and this is the first record of compound 9 from the genus Polygonum. Except for compound 4, all the isolates showed potential inhibitory activity against PTP1B with half-maximal inhibitory concentration IC50 values ranging from 6.3 to 28.9 µM. Furthermore, a kinetic study indicated mixed-competitive inhibition with PTP1B for compounds 2 and 9 and noncompetitive inhibition for compounds 3 and 6. In addition, compounds 2, 3, 6, and 9 also induced the 2-deoxy-2-[(7-nitro-2,1,3-benzoxadiazol-4-yl) amino]-d-glucose uptake stimulation in 3T3-L1 adipocytes at concentrations of 10 and 5 µM. Taken together, the results reveal that P. cuspidatum could be a new source of natural compounds for further research and development of antidiabetic agents.

Gastroprotective and Healing Effects of Polygonum cuspidatum Root on Experimentally Induced Gastric Ulcers in Rats

Polygonum cuspidatum is widely used as food and medicine in Korea, China, and Japan. Its major bioactive components, resveratrol and emodin, reportedly protect against gastric lesions. We therefore aimed to investigate: (1) the gastroprotective effects of P. cuspidatum roots in hydrochloric acid/ethanol (HCl/EtOH)- and indomethacin-induced acute gastric ulcer rat models; (2) the healing effects in an acetic acid-induced ulcer model; and (3) potential mechanisms by measuring gastric acid secretion-related parameters in a pyloric ligation-induced ulcer model, and by measuring antioxidant enzyme and prostaglandin E₂ levels in the gastric tissue of HCl/EtOH-treated rats. Oral administration of P. cuspidatum extract (PCE) at doses of 100 and 300 mg/kg significantly decreased HCl/EtOH- and indomethacin-induced gastric lesions. PCE at 300 mg/kg significantly reduced gastric lesions in acetic acid-induced ulcers. PCE increased superoxide dismutase (SOD)activity and glutathione(GSH) and prostaglandin E₂ levels in gastric tissue, whereas it did not alter gastric acid secretion-related parameters. Our findings indicate that PCE has gastroprotective effects against HCl/EtOH and non-steroidal anti-inflammatory drugs(NSAIDs) and promotes healing of acetic acid-induced ulcers. These gastric mucosal protection and ulcer healing effects are associated with antioxidant effects and the augmentation of prostaglandin E₂ and suggest that P. cuspidatum might be a promising preventive and therapeutic agent for treating gastric ulcers.

Unraveling the complexity of complex mixtures by combining high-resolution pharmacological, analytical and spectroscopic techniques: antidiabetic constituents in Chinese medicinal plants

Medicinal plants have been widely used as (poly)pharmacological remedies and constitute a rich source for antidiabetic drug discovery. In the present study, forty medicinal plant samples collected in China were tested for inhibitory activity against α-glucosidase, α-amylase, and protein-tyrosine phosphatase 1B (PTP1B). Crude ethyl acetate extracts of Dioscorea bulbifera L., Boehmeria nivea Gaudich, Tinospora sagittata Gagnep. and Persicaria bistorta (L.) Samp. showed dual inhibitory activity towards α-glucosidase and PTP1B, and were chosen for further investigation. Subsequent dual high-resolution α-glucosidase/PTP1B profiling or triple high-resolution α-glucosidase/α-amylase/PTP1B profiling combined with HPLC-HRMS and NMR spectroscopy led to the identification of 28 metabolites with one or more bioactivities. Among these, three new phenanthrenes were identified from D. bulbifera, including one new biphenanthrene (10) exhibiting promising dual inhibitory activity towards α-glucosidase and PTP1B with IC50 values of 2.08 ± 0.19 and 3.36 ± 0.25 μM, respectively. Two triterpenoids and one fatty acid from B. nivea and T. sagittata as well as some commercially available fatty acids showed strong PTP1B inhibitory activity with IC50 values in the range of 4.89 ± 0.38 to 53.77 ± 4.20 μM.

Exploring the inhibitory mechanism of piceatannol on α-glucosidase relevant to diabetes mellitus

Due to their association with type 2 diabetes mellitus treatment, α-glucosidase inhibitors have attracted increasing attention of researchers. In this study, we systemically investigated the kinetics and inhibition mechanism of piceatannol on α-glucosidase. Enzyme kinetics analyses showed that piceatannol exhibited strong inhibition on α-glucosidase in a non-competitive manner. Spectroscopy analyses indicated that piceatannol could bind with α-glucosidase to form complexes via high affinity. Further, computational molecular dynamics and molecular docking studies validated that the binding of piceatannol was outside the catalytic site of α-glucosidase, which would induce conformational changes of α-glucosidase and block the entrance of substrate, causing declines in α-glucosidase activities. Our results provide useful information not only for the inhibition mechanism of piceatannol against α-glucosidase but also for a novel target site for developing novel α-glucosidase inhibitors as potential therapeutic agents in the treatment of type 2 diabetes mellitus.

The non-competitive inhibition of piceatannol on α-glucosidase. A combination of dynamic and static process with one binding site. The involvement of hydrophobic interactions and hydrogen bonding. Dietary recommendations for diabetes or potential antidiabetic drug.

Emerging strategies for the activity assay and inhibitor screening of alpha-glucosidase

The high incidence of diabetes mellitus has caused widespread concern around the world, and has quickly become one of the most prevalent and costly chronic diseases.

New phenolic glycosides from Polygonum cuspidatum

Two new isobenzofuranone derivatives, polyphthaliside A (1) and polyphthaliside B (2), and a new isocoumarin derivative, polyisocoumarin (3), were isolated from Polygonum cuspidatum. Their structures were elucidated by detailed spectroscopic analysis and chemical methods. The cytotoxicity activity and PTP1B inhibitory activity of compounds 1-3 were estimated and none of them exhibited activities at a concentration of 10 μM.

2(5H)-Furanone sesquiterpenes from Eremophila bignoniiflora: High-resolution inhibition profiling and PTP1B inhibitory activity

Eremophila bignoniiflora is a shrub distributed throughout inland northern and eastern Australia, and it has been used in several medicinal applications by some Australian Aboriginal people. In our continued search for anti-diabetic constituents from natural resources, the crude ethyl acetate extract of E. bignoniiflora was found to have protein-tyrosine phosphatase 1B (PTP1B) inhibitory activity with an IC₅₀ value of 23.9 ± 1.9 μg/mL. High-resolution PTP1B inhibition profiling combined with HRMS and NMR were subsequently used to investigate the individual compounds responsible for the observed bioactivity of the crude extract. This led to identification of five undescribed 2(5H)-furanone sesquiterpenes, together with 13 flavonoids and phenolic compounds. Dose-response curves of the isolated compounds revealed that two 2(5H)-furanone sesquiterpene cinnamates and three flavonoids exhibited moderate PTP1B inhibitory activity with IC₅₀ values from 41.4 ± 1.4 to 154.5 ± 8.9 μM.

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.

Procyanidin B2 3″-O-gallate Isolated from Reynoutria elliptica Prevents Glutamate-Induced HT22 Cell Death by Blocking the Accumulation of Intracellular Reactive Oxygen Species

In this study, we examined the neuroprotective effects of MeOH extract and bioactive compounds obtained from Reynoutria elliptica seeds using HT22 cells from the murine hippocampal cell line as its underlying molecular basis, which has not yet been elucidated. Our study showed that the MeOH extract of R. elliptica seeds strongly protected HT22 cells from glutamate toxicity. To clarify the responsible compound for the neuroprotective effects, we took an interest in procyanidins of R. elliptica since procyanidins are known to exhibit high structural diversity and neuroprotective activity. To isolate the procyanidins efficiently, a phytochemical investigation of the MeOH extract from R. elliptica seeds using the LC/MS-guided isolation approach was applied, and procyanidin B2 3″-O-gallate (1) was successfully isolated. The structure of 1 was elucidated by analyzing the nuclear magnetic resonance spectroscopic data and LC/MS analysis. The neuroprotective activities of 1 were thoroughly examined using HT22 cells. Compound 1 exhibited a strong antioxidant efficacy and blocked glutamate-mediated increase in the reactive oxygen species (ROS) accumulation. Furthermore, compound 1 significantly inhibited the phosphorylation of extracellular signal-regulated kinase, p38, and c-Jun N-terminal kinase, which were increased by glutamate. These findings prove that the extract of R. elliptica seeds containing procyanidin B2 3″-O-gallate, which is a strong neuroprotective component, can be used as a functional food forattenuating and regulating neurological disorders.

Procyanidin A2, an anti-diabetic condensed tannin extracted from Wendlandia glabrata, reduces elevated G-6-Pase and mRNA levels in diabetic mice and increases glucose uptake in CC1 hepatocytes and C1C12 myoblast cells

To reduce the global burden of diabetes in an affordable way great attention has been paid to the search for functional foods and herbal remedies. One of the most popularly used functional foods in the North Eastern region of India is tender shoots of Wendlandia glabrata DC. In the current study identification of active anti-diabetic constituent of the tender shoots of W. glabrata was guided through α-glucosidase inhibition and procyanidin A2 was identified with IC₅₀ 0.27 ± 0.01 μg mL⁻¹ making it potential source for postprandial management of DM type 2. The study has also demonstrated procyanidin A2 as a potent anti-diabetic agent that exhibits significant glucose-6-phosphatase inhibitory activities and downregulated mRNA level in diabetic mice as well as increases glucose uptake in hepatocytes and myoblast cells. This study revealed that easily available tender shoots of W. glabrata could be used to make specific dietary recommendations for consumption for affordable management of diabetes.

Wendlandia glabrata and procyanidin A2 isolated thereof are exhibited significant anti-diabetic effect.

Progress in the discovery of naturally occurring anti-diabetic drugs and in the identification of their molecular targets

Diabetes mellitus (DM), a chronic metabolic disease, severely affects patients' life and intensively increases risks of developing other diseases. It is estimated that 0.4 billion individuals worldwide are subjected to diabetes, especially type 2 diabetes mellitus. At present, although various synthetic drugs for diabetes such as Alogliptin and Rosiglitazone, etc. have been used to manage diabetes, some of them showed severe side effects. Given that the pathogenesis of type 2 diabetes mellitus, natural occurring drugs are beneficial alternatives for diabetes therapy with low adverse effects or toxicity. Recently, more and more plant-derived extracts or compounds were evaluated to have anti-diabetic activities. Their anti-diabetic mechanisms involve certain key targets like α-glucosidase, α-amylase, DPP-4, PPAR γ, PTP1B, and GLUT4, etc. Here, we summarize the newly found anti-diabetic (type 2 diabetes mellitus) natural compounds and extracts from 2011-2017, and give the identification of their molecular targets. This review could provide references for the research of natural agents curing type 2 diabetes mellitus (T2DM).

Quadruple high-resolution α-glucosidase/α-amylase/PTP1B/radical scavenging profiling combined with high-performance liquid chromatography-high-resolution mass spectrometry-solid-phase extraction-nuclear magnetic resonance spectroscopy for identification of antidiabetic constituents in crude root bark of Morus alba L

In this paper, quadruple high-resolution α-glucosidase/α-amylase/PTP1B/radical scavenging profiling combined with HPLC-HRMS-SPE-NMR were used for studying the polypharmacological properties of crude root bark extract of Morus alba L. This species is used as an anti-diabetic principle in many traditional treatment systems around the world, and the crude ethyl acetate extract of M. alba root bark was found to inhibit α-glucosidase, α-amylase and protein-tyrosine phosphatase 1B (PTP1B) with IC₅₀ values of 1.70 ± 0.72, 5.16 ± 0.69, and 5.07 ± 0.68 μg/mL as well as showing radical scavenging activity equaling a TEAC value of (3.82 ± 0.14) × 10⁴ mM per gram extract. Subsequent investigation of the crude extract using quadruple high-resolution α-glucosidase/α-amylase/PTP1B/radical scavenging profiling provided a quadruple biochromatogram that allowed direct correlation of the HPLC peaks with one or more of the tested bioactivities. This was used to target subsequent HPLC-HRMS-SPE-NMR analysis towards peaks representing bioactive analytes, and led to identification of a new Diels-Alder adduct named Moracenin E as well as a series of Diels-Alder adducts and isoprenylated flavonoids as potent α-glucosidase and α-amylase inhibitors with IC₅₀ values in the range of 0.60-27.15 μM and 1.22-69.38 μM, respectively. In addition, these compounds and two 2-arylbenzofurans were found to be potent PTP1B inhibitors with IC₅₀ values ranging from 4.04 to 21.67 μM. The high-resolution radical scavenging profile also revealed that almost all of the compounds possess radical scavenging activity. In conclusion the quadruple high-resolution profiling method presented here allowed a detailed profiling of individual constituents in crude root bark extract of M. alba, and the method provides a general tool for detailed mapping of bioactive constituents in polypharmacological herbal remedies.

Quickly Screening for Potential α-Glucosidase Inhibitors from Guava Leaves Tea by Bioaffinity Ultrafiltration Coupled with HPLC-ESI-TOF/MS Method

Guava leaves tea (GLT) has a potential antihyperglycemic effect. Nevertheless, it is unclear which compound plays a key role in reducing blood sugar. In this study, GLT extract (IC₅₀ = 19.37 ± 0.21 μg/mL) exhibited a stronger inhibitory potency against α-glucosidase than did acarbose (positive control) at IC₅₀ = 178.52 ± 1.37 μg/mL. To rapidly identify the specific α-glucosidase inhibitor components from GLT, an approach based on bioaffinity ultrafiltration combined with high performance liquid chromatography coupled to electrospray ionization-time-of-flight-mass spectrometry (BAUF-HPLC-ESI-TOF/MS) was developed. Under the optimal bioaffinity ultrafiltration conditions, 11 corresponding potential α-glucosidase inhibitors with high affinity degrees (ADs) were screened and identified from the GLT extract. Quercetin (IC₅₀ = 4.51 ± 0.71 μg/mL) and procyanidin B3 (IC₅₀ = 28.67 ± 5.81 μg/mL) were determined to be primarily responsible for the antihyperglycemic effect, which further verified the established screening method. Moreover, structure-activity relationships were discussed. In conclusion, the BAUF-HPLC-ESI-TOF/MS method could be applied to determine the potential α-glucosidase inhibitors from complex natural products quickly.