Inhibitory effect of epigallocatechin-3-O-gallate on α-glucosidase and its hypoglycemic effect via targeting PI3K/AKT signaling pathway in L6 skeletal muscle cells

Epicatechin Isolated from Litchi chinensis Sonn. (Litchi) Fruit Peel Ethyl Acetate Extract Modulated Glucose Uptake in Chang Cells and Suppressed ROS Production in RAW 264.7 Macrophages

Bioactive flavonoid epicatechin has been reported in the peel of litchi fruit but isolated from its hydroalcoholic extracts. This study isolated epicatechin with cellular glucose uptake modulatory and ROS production inhibitory properties from the ethyl acetate (EtOAc) extract using a bioassay-guided approach. The fruit peel was defatted with hexane and sequentially extracted using dichloromethane (DCM), EtOAc, methanol (MeOH) and water. In vitro phytochemical models, namely antioxidant (Fe3+ reducing, radical scavenging and anti-linoleic acid peroxidative) and glycaemic control (α-glucosidase and α-amylase inhibitory and glucose uptake modulatory), were employed for the bioassay-guided isolation, while the isolated compound was characterised using NMR and mass spectrometry and assessed for dose-dependent inhibition of α-glucosidase and lipopolysaccharide (LPS)-induced cellular ROS production, as well as modulation of cellular glucose uptake. Relative to the other extracts, the EtOAc extract had appreciable phenol and flavonoid contents, which perhaps influenced its potent anti-lipid peroxidative (65.0%) and α-glucosidase inhibitory (52.4%) effects. The α-glucosidase inhibitory potency of the fractions (1-8) from the EtOAc extracts correlated with their flavonoid contents, with fraction 5 outperforming other fractions. The fraction comprised a pool of fractions obtained from the DCM:MeOH:water (7:3:0.281 v/v/v) solvent system. LC-MS revealed the predominant presence of epicatechin in fraction 5, which was later isolated from one of the sub-fractions (sub-fraction 4) of fraction 5. This sub-fraction had stronger anti-lipid peroxidative (65.5%), α-glucosidase inhibitory (65.8%) and glucose uptake modulatory (38.2%) effects than the other sub-fractions from fraction 5, which could have been influenced by the isolated epicatechin. Moreover, the isolated epicatechin inhibited α-glucosidase (IC50 = 35.3 µM), modulated cellular glucose uptake (EC50 = 78.5 µM) and inhibited LPS-induced ROS production in RAW 264.7 macrophages in a dose-dependent fashion [IC50 = 18.9 µM; statistically comparable (p > 0.05) to ascorbic acid, IC50 = 9.57 µM]. Epicatechin from litchi peel EtOAc extract could potentiate glucose uptake modulatory, α-glucosidase inhibitory and ROS suppressive capacities, which could be influential in the use of litchi fruit peel for managing diabetes and associated oxidative damage.

Lipophilic derivatives of EGCG as potent α-amylase and α-glucosidase inhibitors ameliorating oxidative stress and inflammation

Uncontrolled hyperglycemia leads to increased oxidative stress, chronic inflammation, and insulin resistance, rendering diabetes management harder to accomplish. To tackle these myriads of challenges, researchers strive to explore innovative multifaceted treatment strategies, including inhibiting carbohydrate hydrolases. Herein, we report alkyl-ether EGCG derivatives as potent α-amylase and α-glucosidase inhibitors that could simultaneously ameliorate oxidative stress and inflammation. 4″-C18 EGCG, the most promising compound, showed multifold improvement in glycaemic management compared to acarbose, with 230-fold greater inhibition (competitive) of α-glucosidase (IC50 0.81 µM) and 3-fold better inhibition of α-amylase (IC50 3.74 µM). All derivatives showed stronger antioxidant activity (IC50 6.16-15.76 µM) than vitamin C, while acarbose showed none. 4″-C18 EGCG also downregulated pro-inflammatory cytokines and showed no significant cytotoxicity up to 50 µM in primary human peripheral blood mononuclear cells (PBMC), non-cancerous cell line, 3T3-L1 and HEK 293. The in silico binding affinity analysis of 4″-C18 EGCG with α-amylase and α-glucosidase was found to exhibit a good extent of interaction as compared to acarbose. In comparison to EGCG, 4″-Cn EGCG derivatives were found to remain stable in the physiological conditions even after 24 h. Together, the reported molecules demonstrated multifaceted antidiabetic potential inhibiting carbohydrate hydrolases, reducing oxidative stress, and inflammation, which are known to aggravate diabetes.

Design of Scaffolds Based on Zinc-Modified Marine Collagen and Bilberry Leaves Extract-Loaded Silica Nanoparticles as Wound Dressings

Purpose

In this study, wound dressings were designed using zinc-modified marine collagen porous scaffold as host for wild bilberry (WB) leaves extract immobilized in functionalized mesoporous silica nanoparticles (MSN). These new composites were developed as an alternative to conventional wound dressings. In addition to the antibacterial activity of classic antibiotics, a polyphenolic extract could act as an antioxidant and/or an anti-inflammatory agent as well.

Methods

Wild bilberry leaves extract was prepared by ultrasound-assisted extraction in ethanol and its properties were evaluated by UV-Vis spectroscopy (radical scavenging activity, total amount of polyphenols, flavonoids, anthocyanins, and condensed tannins). The extract components were identified by HPLC, and the antidiabetic properties of the extract were evaluated via α-glucosidase inhibitory activity. Spherical MSN were modified with propionic acid or proline moieties by post-synthesis method and used as carriers for the WB leaves extract. The textural and structural features of functionalized MSN were assessed by nitrogen adsorption/desorption isotherms, small-angle XRD, SEM, TEM, and FTIR spectroscopy. The composite porous scaffolds were prepared by freeze drying of the zinc-modified collagen suspension containing WB extract loaded silica nanoparticles.

Results

The properties of the new composites demonstrated enhanced properties in terms of thermal stability of the zinc-collagen scaffold, without altering the protein conformation, and stimulation of NCTC fibroblasts mobility. The results of the scratch assay showed contributions of both zinc ions from collagen and the polyphenolic extract incorporated in functionalized silica in the wound healing process. The extract encapsulated in functionalized MSN proved enhanced biological activities compared to the extract alone: better inhibition of P. aeruginosa and S. aureus strains, higher biocompatibility on HaCaT keratinocytes, and anti-inflammatory potential demonstrated by reduced IL-1β and TNF-α levels.

Conclusion

The experimental data shows that the novel composites can be used for the development of effective wound dressings.

Anti-Inflammatory, Antidiabetic, and Antioxidant Properties of Extracts Prepared from Pinot Noir Grape Marc, Free and Incorporated in Porous Silica-Based Supports

This study presents properties of hydroethanolic extracts prepared from Pinot Noir (PN) grape pomace through conventional, ultrasound-assisted or solvothermal extraction. The components of the extracts were identified by HPLC. The total content of polyphenols, flavonoids, anthocyanins, and condensed tannins, as well as antioxidant activity and α-glucosidase inhibitory activity of extracts were evaluated using UV-vis spectroscopy. All extracts were rich in phenolic compounds, proving a good radical scavenging activity. The extract obtained by conventional extraction at 80 °C showed the best α-glucosidase inhibitory activity close to that of (-)-epigallocatechin gallate. To improve the chemical stability of polyphenols, the chosen extract was incorporated in porous silica-based supports: amine functionalized silica (MCM-NH2), fucoidan-coated amine functionalized silica (MCM-NH2-Fuc), MCM-41, and diatomite. The PN extract exhibited moderate activity against Gram-positive S. aureus (MIC = 156.25 μg/mL) better than against Gram-negative E. coli (MIC = 312.5 μg/mL). The biocompatibility of PN extract, free and incorporated in MCM-NH2 and MCM-NH2-Fuc, was assessed on RAW 264.7 mouse macrophage cells, and the samples showcased a good cytocompatibility at 10 µg/mL concentration. At this concentration, PN and PN@MCM-NH2-Fuc reduced the inflammation by inhibiting NO production. The anti-inflammatory potential against COX and LOX enzymes of selected samples was evaluated and compared with that of Indomethacin and Zileuton, respectively. The best anti-inflammatory activity was observed when PN extract was loaded on MCM-NH2-Fuc support.

Whey Protein Sodium-Caseinate as a Deliverable Vector for EGCG: In Vitro Optimization of Its Bioaccessibility, Bioavailability, and Bioactivity Mode of Actions

Epigallocatechin gallate (EGCG), the principal catechin in green tea, exhibits diverse therapeutic properties. However, its clinical efficacy is hindered by poor stability and low bioavailability. This study investigated solid particle-in-oil-in-water (S/O/W) emulsions stabilized by whey protein isolate (WPI) and sodium caseinate (NaCas) as carriers to enhance the bioavailability and intestinal absorption of EGCG. Molecular docking revealed binding interactions between EGCG and these macromolecules. The WPI- and NaCas-stabilized emulsions exhibited high encapsulation efficiencies (>80%) and significantly enhanced the bioaccessibility of EGCG by 64% compared to free EGCG after simulated gastrointestinal digestion. Notably, the NaCas emulsion facilitated higher intestinal permeability of EGCG across Caco-2 monolayers, attributed to the strong intermolecular interactions between caseins and EGCG. Furthermore, the emulsions protected Caco-2 cells against oxidative stress by suppressing intracellular reactive oxygen species generation. These findings demonstrate the potential of WPI- and NaCas-stabilized emulsions as effective delivery systems to improve the bioavailability, stability, and bioactivity of polyphenols like EGCG, enabling their applications in functional foods and nutraceuticals.

Novel molecular hybrids of EGCG and quinoxaline: Potent multi-targeting antidiabetic agents that inhibit α-glucosidase, α-amylase, and oxidative stress

Diabetes mellitus is a multifactorial disease and its effective therapy often demands several drugs with different modes of action. Herein, we report a rational design and synthesis of multi-targeting novel molecular hybrids comprised of EGCG and quinoxaline derivatives that can effectively inhibit α-glucosidase, α-amylase as well as control oxidative stress by scavenging ROS. The hybrids showed superior inhibition of α-glucosidase along with similar α-amylase inhibition as compared to standard drug, acarbose. Most potent compound, 15c showed an IC50 of 0.50 μM (IC50 of acarbose 190 μM) against α-glucosidase. Kinetics studies with 15c revealed a competitive inhibition against α-glucosidase. Binding affinity of 15c (-9.5 kcal/mol) towards α-glucosidase was significantly higher than acarbose (-7.7 kcal/mol). 15c exhibited remarkably high antioxidant activity (IC50 = 18.84 μM), much better than vitamin C (IC50 = 33.04 μM). Of note, acarbose shows no antioxidant activity. Furthermore, α-amylase activity was effectively inhibited by 15c with an IC50 value of 16.35 μM. No cytotoxicity was observed for 15c (up to 40 μM) in MCF-7 cells. Taken together, we report a series of multi-targeting molecular hybrids capable of inhibiting carbohydrate hydrolysing enzymes as well as reducing oxidative stress, thus representing an advancement towards effective and novel therapeutic approaches for diabetes.

Flavonoids as dual-target inhibitors against α-glucosidase and α-amylase: a systematic review of in vitro studies

Diabetes mellitus remains a major global health issue, and great attention is directed at natural therapeutics. This systematic review aimed to assess the potential of flavonoids as antidiabetic agents by investigating their inhibitory effects on α-glucosidase and α-amylase, two key enzymes involved in starch digestion. Six scientific databases (PubMed, Virtual Health Library, EMBASE, SCOPUS, Web of Science, and WHO Global Index Medicus) were searched until August 21, 2022, for in vitro studies reporting IC50 values of purified flavonoids on α-amylase and α-glucosidase, along with corresponding data for acarbose as a positive control. A total of 339 eligible articles were analyzed, resulting in the retrieval of 1643 flavonoid structures. These structures were rigorously standardized and curated, yielding 974 unique compounds, among which 177 flavonoids exhibited inhibition of both α-glucosidase and α-amylase are presented. Quality assessment utilizing a modified CONSORT checklist and structure-activity relationship (SAR) analysis were performed, revealing crucial features for the simultaneous inhibition of flavonoids against both enzymes. Moreover, the review also addressed several limitations in the current research landscape and proposed potential solutions. The curated datasets are available online at https://github.com/MedChemUMP/FDIGA .

Inhibition of α-glucosidase activity by curcumin loaded on ZnO@rGO nanocarrier for potential treatment of diabetes mellitus

Curcumin (Cur) is an acidic polyphenol with some effects on α-glucosidase (α-Glu), but Cur has disadvantages such as being a weak target, lacking passing the blood-brain barrier and having low bioavailability. To enhance the curative effect of Cur, the hybrid composed of ZnO nanoparticles decorated on rGO was used to load Cur (ZnO@rGO-Cur). The use of the multispectral method and enzyme inhibition kinetics analysis certify the inhibitory effect and interaction mechanism of ZnO@rGO-Cur with α-Glu. The static quenching of α-Glu with both Cur and ZnO@rGO-Cur is primarily driven by hydrogen bond and van der Waals interactions. The conformation-changing ability by binding to the neighbouring phenolic hydroxyl group of Cur increased their ability to alter the secondary structure of α-Glu, resulting in the inhibition of enzyme activity. The inhibition constant (Ki, Cur  > Kis,ZnO@rGO-Cur ) showed that the inhibition effect of ZnO@rGO-Cur on α-Glu was larger than that of Cur. The CCK-8 experiments proved that ZnO@rGO nanocomposites have good biocompatibility. These results suggest that the therapeutic potential of ZnO@rGO-Cur composite is an emerging nanocarrier platform for drug delivery systems for the potential treatment of diabetes mellitus.

Diabetes Pharmacotherapy and its effects on the Skeletal Muscle Energy Metabolism

The disorders of skeletal muscle metabolism in patients with Type 2 diabetes mellitus (T2DM), such as mitochondrial defection and glucose transporters (GLUTs) translocation dysfunctions, are not uncommon. Therefore, when anti-diabetic drugs were used in various chronic diseases associated with hyperglycemia, the impact on skeletal muscle should not be ignored. However, current studies mainly focus on muscle mass rather than metabolism or functions. Anti-diabetic drugs might have a harmful or beneficial impact on skeletal muscle. In this review, we summarize the upto- date studies on the effects of anti-diabetic drugs and some natural compounds on skeletal muscle metabolism, focusing primarily on emerging data from pre-clinical to clinical studies. Given the extensive use of anti-diabetic drugs and the common sarcopenia, a better understanding of energy metabolism in skeletal muscle deserves attention in future studies.

Bioactive Dairy-Fermented Products and Phenolic Compounds: Together or Apart

Fermented dairy products (e.g., yogurt, kefir, and buttermilk) are significant in the dairy industry. They are less immunoreactive than the raw materials from which they are derived. The attractiveness of these products is based on their bioactivity and properties that induce immune or anti-inflammatory processes. In the search for new solutions, plant raw materials with beneficial effects have been combined to multiply their effects or obtain new properties. Polyphenols (e.g., flavonoids, phenolic acids, lignans, and stilbenes) are present in fruit and vegetables, but also in coffee, tea, or wine. They reduce the risk of chronic diseases, such as cancer, diabetes, or inflammation. Hence, it is becoming valuable to combine dairy proteins with polyphenols, of which epigallocatechin-3-gallate (EGCG) and chlorogenic acid (CGA) show a particular predisposition to bind to milk proteins (e.g., α-lactalbumin β-lactoglobulin, αs1-casein, and κ-casein). Reducing the allergenicity of milk proteins by combining them with polyphenols is an essential issue. As potential 'metabolic prebiotics', they also contribute to stimulating the growth of beneficial bacteria and inhibiting pathogenic bacteria in the human gastrointestinal tract. In silico methods, mainly docking, assess the new structures of conjugates and the consequences of the interactions that are formed between proteins and polyphenols, as well as to predict their action in the body.

Therapeutic Activity of Green Tea Epigallocatechin-3-Gallate on Metabolic Diseases and Non-Alcoholic Fatty Liver Diseases: The Current Updates

Green tea polyphenols have numerous functions including antioxidation and modulation of various cellular proteins and are thus beneficial against metabolic diseases including obesity, type 2 diabetes, cardiovascular and non-alcoholic fatty liver diseases, and their comorbidities. Epigallocatechin-3-gallate (EGCG) is the most abundant polyphenol in green tea and is attributed to antioxidant and free radical scavenging activities, and the likelihood of targeting multiple metabolic pathways. It has been shown to exhibit anti-obesity, anti-inflammatory, anti-diabetic, anti-arteriosclerotic, and weight-reducing effects in humans. Worldwide, the incidences of metabolic diseases have been escalating across all age groups in modern society. Therefore, EGCG is being increasingly investigated to address the problems. This review presents the current updates on the effects of EGCG on metabolic diseases, and highlights evidence related to its safety. Collectively, this review brings more evidence for therapeutic application and further studies on EGCG and its derivatives to alleviate metabolic diseases and non-alcoholic fatty liver diseases.

Mechanisms Underlying the Effects of the Green Tea Polyphenol EGCG in Sarcopenia Prevention and Management

Sarcopenia is prevalent among the older population and severely affects human health. Tea catechins may benefit for skeletal muscle performance and protect against secondary sarcopenia. However, the mechanisms underlying their antisarcopenic effect are still not fully understood. Despite initial successes in animal and early clinical trials regarding the safety and efficacy of (-)-epigallocatechin-3-gallate (EGCG), a major catechin of green tea, many challenges, problems, and unanswered questions remain. In this comprehensive review, we discuss the potential role and underlying mechanisms of EGCG in sarcopenia prevention and management. We thoroughly review the general biological activities and general effects of EGCG on skeletal muscle performance, EGCG's antisarcopenic mechanisms, and recent clinical evidence of the aforesaid effects and mechanisms. We also address safety issues and provide directions for future studies. The possible concerted actions of EGCG indicate the need for further studies on sarcopenia prevention and management in humans.

Nutritional and medicinal plants as potential sources of enzyme inhibitors toward the bioactive functional foods: an updated review

Enzymes are biologically active complex protein molecules that catalyze most chemical reactions in living organisms, and their inhibitors accelerate biological processes. This review emphasizes medicinal food plants and their isolated chemicals inhibiting clinically important enzymes in common diseases. A mechanistic overview was investigated to explain the mechanism of these food bases enzyme inhibitors. The enzyme inhibition potential of medicinal food plants and their isolated substances was searched in Ovid, PubMed, Science Direct, Scopus, and Google Scholar. Cholinesterase, amylase, glucosidase, xanthine oxidase, tyrosinase, urease, lipoxygenase, and others were inhibited by crude extracts, solvent fractions, or isolated pure chemicals from medicinal food plants. Several natural compounds have shown tyrosinase inhibition potential, including quercetin, glabridin, phloretin-4-O-β-D-glucopyranoside, lupinalbin, and others. Some of these compounds' inhibitory kinetics and molecular mechanisms are also discussed. Phenolics and flavonoids inhibit enzyme activity best among the secondary metabolites investigated. Several studies showed flavonoids' significant antioxidant and anti-inflammatory activities, highlighting their medicinal potential. Overall, many medicinal food plants, their crude extracts/fractions, and isolated compounds have been studied, and some promising compounds depending on the enzyme have been found. Still, more studies are recommended to derive potential pharmacologically active functional foods.

Catechins and Proanthocyanidins Involvement in Metabolic Syndrome

Recent studies on natural antioxidant compounds have highlighted their potentiality against various pathological conditions. The present review aims to selectively evaluate the benefits of catechins and their polymeric structure on metabolic syndrome, a common disorder characterized by a cluster of three main risk factors: obesity, hypertension, and hyperglycemia. Patients with metabolic syndrome suffer chronic low inflammation state and oxidative stress both conditions effectively countered by flavanols and their polymers. The mechanism behind the activity of these molecules has been highlighted and correlated with the characteristic features present on their basic flavonoidic skelethon, as well as the efficient doses needed to perform their activity in both in vitro and in vivo studies. The amount of evidence provided in this review offers a starting point for flavanol dietary supplementation as a potential strategy to counteract several metabolic targets associated with metabolic syndrome and suggests a key role of albumin as flavanol-delivery system to the different target of action inside the organism.

High-throughput screening and investigation of the inhibitory mechanism of α-glucosidase inhibitors in teas using an affinity selection-mass spectrometry method

An affinity selection-mass spectrometry method was applied for high-throughput screening of α-glucosidase (AGH) inhibitors from teas. Fourteen out of nineteen screened AGH inhibitor candidates were clustered as galloylated polyphenols (GPs). "AGH-GPs" interaction studies, including enzyme kinetics, fluorescence spectroscopy, circular dichroism, and molecular docking, jointly suggested that GPs noncompetitively inhibit AGH activity by interacting with amino acid residues near the active site of AGH and inducing changes in AGH secondary structure. Representative GPs and white tea extract (WTE) showed comparable AGH inhibition effects in Caco2 cells and postprandial hypoglycemic efficacy in diabetic mice as acarbose. The area under the curve of oral sucrose tolerance test was lower by 8.16%, 6.17%, and 7.37% than control group in 15 mg/kg EGCG, 15 mg/kg strictinin, and 150 mg/kg WTE group, respectively. Our study presents a high-efficiency approach to discover novel AGH inhibitors and elucidates a potential mechanism by which tea decreases diabetes risks.

Studies on the key constituents and the related mechanisms of Clerodendranthus spicatus in the treatment of diabetes based on network pharmacology

ETHNOPHARMACOLOGICAL RELEVANCE

Clerodendranthus spicatus is a traditional Chinese medicine and has been used to treat diabetes and some kidney diseases for a long history.

AIM OF THE STUDY

The research aimed to study the active constituents, the potential targets and the related mechanisms of C. spicatus in the treatment of diabetes through network pharmacology method and verify the antidiabetic activity by molecular biology experiments.

MATERIALS AND METHODS

A comprehensive network pharmacology strategy was used to predict the key active constituents, the key targets and the related mechanisms and pathways of C. spicatus in the treatment of diabetes. The strategy mainly included screening and predicting potential active constituents and targets by network construction, GO (Gene Ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) enrichment analysis. Based on the predicted results, C. spicatus was extracted by ultrasonic method with 50% ethanol and enriched by using macroporous resin. The compounds with potential antidiabetic effects were separated through silica-gel column chromatography and HPLC (high performance liquid chromatography), and then identified by MS (mass spectrum) and NMR (nuclear magnetic resonance). The C. spicatus extract and isolated compounds were tested by in-vitro and cell experiments to verify their antidiabetic activities, including antioxidant activities, inhibition activities on α-glucosidase and α-amylase, the influence on glucose uptake in cell experiments and the Western blot of PI3K and Akt expression levels.

RESULTS

A total of 18 active constituents and 16 key targets of C. spicatus in the treatment of diabetes were screened out through network pharmacology method. Phenolic acids might be the main target compounds for the next research. After extraction, enrichment and separation, the phenolic acids-enriched fraction of C. spicatus and four phenolic acid compounds (helisterculin C, salvianolic acid B, orthosiphoic acid E and ethyl caffeate) were obtained. Among them, salvianolic acid B was isolated from C. spicatus for the first time and orthosiphoic acid E was isolated from natural products for the first time. In experiment verification, the crude extract of C. spicatus, the phenolic acids-enriched fraction and the four compounds all showed antidiabetic potentials. The phenolic acids in C. spicatus had antioxidant activities, inhibitory activities on α-amylase and α-glucosidase and promoted glucose uptake in L6 cells through PI3K/Akt signaling pathway.

CONCLUSIONS

This study showed that C. spicatus had antidiabetic activities with the mechanism of the mode of multi-compounds acting on multi-targets and multi-pathways. The main active phenolic acid compounds were also identified. It provided theoretical basis for further development and utilization of C. spicatus.

Application of Molecular Simulation Methods in Food Science: Status and Prospects

Molecular simulation methods, such as molecular docking, molecular dynamic (MD) simulation, and quantum chemical (QC) calculation, have become popular as characterization and/or virtual screening tools because they can visually display interaction details that in vitro experiments can not capture and quickly screen bioactive compounds from large databases with millions of molecules. Currently, interdisciplinary research has expanded molecular simulation technology from computer aided drug design (CADD) to food science. More food scientists are supporting their hypotheses/results with this technology. To understand better the use of molecular simulation methods, it is necessary to systematically summarize the latest applications and usage trends of molecular simulation methods in the research field of food science. However, this type of review article is rare. To bridge this gap, we have comprehensively summarized the principle, combination usage, and application of molecular simulation methods in food science. We also analyzed the limitations and future trends and offered valuable strategies with the latest technologies to help food scientists use molecular simulation methods.

Phenolic-protein interactions: insight from in-silico analyses – a review

Phenolic compounds are ubiquitous plant secondary metabolites that possess various biological activities and are known to interact with proteins, altering their structure and properties. Therefore, interactions between these compounds and proteins has gained increasing attention due to their potential benefits to human health and for exploitation by the food industry. Phenolic compounds and proteins can form complexes via covalent linkages and/or non-covalent interactions through hydrophobic, electrostatic, van der Waals forces and hydrogen bonding. This review describes possible mechanisms of phenol-protein complex formation, their physiological action and activities that are important in the food industry, and possible outcomes in the terms of molecular docking and simulation analysis. The conformational changes of the protein upon binding with polyphenols can lead to the folding or unfolding of the protein molecules, forming insoluble or soluble complexes. The concentration of polyphenols, their molecular weight and structure, ions/cofactors and conditions of the system determine the precipitation or solubilization of the complex, affecting their nutritional and functional properties as well as their bioactivities. In this regard, molecular docking and simulation studies of phenolic-protein interactions allows comprehensive virtual screening of competitive/non-competitive and site-specific/non-specific conjugation of phenolics with different protein targets and facilitates understanding the observed effects. The docking analysis of flavonoids with enzymes and milk proteins has indicated their potential application in producing nutraceuticals and functional foods. Thus, combining molecular docking and simulation studies with experimental techniques is vital for better understanding the reactions that take place during digestion to engineer and manufacture novel food ingredients with desirable pharmacological properties and as potential food additives.

Graphical Abstract

Improving Regulation of Polymeric Proanthocyanidins and Tea Polyphenols against Postprandial Hyperglycemia via Acid-Catalyzed Transformation

A novel protocol was established to synthesize novel α-glucosidase inhibitors (prodelphinidin B gallates) from proanthocyanidins from Chinese bayberry leaves (BLPs) and epigallocatechin gallate (EGCG) via acid-catalyzed transformation, which had improved regulation against postprandial hyperglycemia. Their structural-activity relationship was clarified by enzymatic kinetics, multispectroscopic method, molecular docking analysis, and sucrose loading test. ProDB MG and DG were noncompetitive inhibitors of α-glucosidase with IC₅₀ values of 7.82 and 7.52 μg/mL, respectively. They bound with α-glucosidase spontaneously through van der Waals force and hydrogen bonding interaction, inducing the change of spatial conformation and secondary structure of α-glucosidase. Molecular docking studies suggested that proDB MG and DG attached to another one nonactive pocket with strong affinity. ProDB DG exerted significant improvement of postprandial hyperglycemia in a dose-dependent manner. Hence, proDB MG and DG, potential antidiabetic compounds, alleviate postprandial hyperglycemia by inhibiting α-glucosidase.

Enhanced alleviation of insulin resistance via the IRS-1/Akt/FOXO1 pathway by combining quercetin and EGCG and involving miR-27a-3p and miR-96-5p

Quercetin and EGCG exhibit anti-diabetic and anti-obesity activities, however, their interactive effects in anti-diabetic/anti-obesity actions and underlying mechanisms remain unclear. This study aimed to fill these knowledge gaps. Quercetin, EGCG or their combination attenuated insulin resistance and decreased hepatic gluconeogenesis in high-fat-high-fructose diet (HFFD)-fed C57BL/6 mice and in palmitic acid (PA)-treated HepG2 cells. In mice, supplementation with quercetin (0.05%w/w), EGCG (0.05%w/w) and their combination (quercetin 0.05%+EGCG 0.05%w/w) reduced weight gain and fasting blood glucose and improved serum biochemical parameters. Compare with quercetin/EGCG alone, the quercetin-EGCG combination reduced gluconeogenesis to a greater extent via IRS-1/Akt/FOXO1-mediated down-regulation of downstream PEPCK and G-6-pase. In HepG2 cells, the quercetin (5 μM)-EGCG (5 μM) co-treatment exerted greater suppression on PA-induced changes in glucose and glycogen contents and hexokinase and G-6-pase activities than quercetin/EGCG alone (each 10 μM). The quercetin-EGCG co-treatment reduced glucose production through targeting FOXO1 and inhibiting the transcription of gluconeogenic enzymes. MiR-27a-3p and miR-96-5p regulated directly FOXO1 expression and function, and co-inhibition of miR-27a-3p and miR-96-5p weakened greatly the protective effect of quercetin-EGCG combination. This is the first report on the contributions of miR-27a-3p and miR-96-5p to the synergistic and protective effect of the quercetin-EGCG co-treatment against PA-induced insulin resistance through inhibiting FOXO1 expression.

α-glucosidase inhibitors from Syzygium polyanthum (Wight) Walp leaves as revealed by metabolomics and in silico approaches

ETHNOPHARMACOLOGICAL RELEVANCE

Syzygium polyanthum (Wight) Walp leaves are traditionally used to cure diabetes in many regions of Indonesia. Traditional use involves boiling the leaves until the water is reduced to half volume, and then the decoction is taken 1-2 times daily. Despite several studies reporting the antidiabetic activity of this plant, bioactive compounds have not been well identified.

AIM OF THE STUDY

Indonesia is one of the countries with the highest diabetes cases, particularly type 2 diabetes mellitus (T2DM). Few people have access to modern medicinal treatment; thus, the role of antidiabetic traditional medicine has become increasingly important. This research aimed to identify α-glucosidase inhibitors from S. polyathum leaves using a metabolomics approach. When the active compounds of S. polyathum are properly identified, the quality of the herb can be more easily controlled.

MATERIALS AND METHODS

The dried leaves of S. polyanthum were extracted by a comprehensive extraction method using a solvent combination of n-hexane, acetone, and water in a gradient, resulting in a total of 42 fractions. All fractions were subjected to an in vitro α-glucosidase inhibition test and chemical profile analysis using Nuclear Magnetic Resonance (NMR) and high performance liquid chromatography (HPLC). Orthogonal projection least square (OPLS) analysis was used to correlate the two data to identify NMR signals, and HPLC chromatogram peaks correlated to the activity. 2D NMR and ultra-high-performance liquid chromatography coupled to high-resolution mass spectrometry (UHPLC-HRMS) analyses were also used to give more precise compound identification. The activity of the identified active compounds was confirmed by an in silico technique.

RESULTS AND DISCUSSION

The results of the α-glucosidase activity test showed that the most active fractions were obtained from solvents with medium polarity: Fractions 9 and 10 (F9 and F10), obtained from gradient acetone-water 4:1 and 3:2, respectively. The IC50 values of F9 and F10 were 24.8 and 31.8 μg/mL, respectively. NMR data showed that F9 had more intense and diverse signals in the aromatic region than F10. OPLS analysis results showed that some typical flavonoid signals abundant in F9 positively correlated with α-glucosidase activity. 2D NMR and UHPLC-HRMS analysis of F9 led to the conclusion that these signals could be attributed to myricetin-3-O-rhamnoside (myricitrin) and epigallocatechin-3-gallate (EGCG). In silico analysis confirmed these results, as myricitrin and EGCG had binding energies resembling acarbose as a positive control (-8.47, -8.19, and -10.13, respectively).

CONCLUSIONS

NMR and HPLC-metabolomics successfully identified myricitrin and EGCG as α-glucosidase inhibitors from S. polyanthum leaves, and docking analysis validated their inhibitory activity. The results of this study justified the traditional use of S. polyanthum as an antidiabetes herbal.

Insights on preparation, structure and activities of Gracilaria lemaneiformis polysaccharide

Gracilaria lemaneiformis is a kind of edible economic red algae, which is rich in polysaccharide, phycobiliprotein, pigments, minerals and other nutrients and functional components. Polysaccharide is one of the main active components of Gracilaria lemaneiformis, which has been reported to present various physiological bioactivities, including regulation of glycolipid metabolism, immune, anti-tumor, anti-inflammatory and other biological activities. This paper aims to provide a brief summary of extraction, purification, structural characteristics, and physiological activities of Gracilaria lemaneiformis polysaccharide (GLP). This article is able to provide theoretical basis for the future research and exploitation of GLP, and improve its potential development to promote the healthy and sustainable processing and high value utilization industry of Gracilaria lemaneiformis.

Dietary Flavonoids and Insulin Signaling in Diabetes and Obesity

Type 2 diabetes (T2D) and obesity are relevant worldwide chronic diseases. A common complication in both pathologies is the dysregulation of the insulin-signaling pathway that is crucial to maintain an accurate glucose homeostasis. Flavonoids are naturally occurring phenolic compounds abundant in fruits, vegetables and seeds. Rising evidence supports a role for the flavonoids against T2D and obesity, and at present, these compounds are considered as important potential chemopreventive agents. This review summarizes in vitro and in vivo studies providing data related to the effects of flavonoids and flavonoid-rich foods on the modulation of the insulin route during T2D and obesity. Notably, few human studies have evaluated the regulatory effect of these phenolic compounds at molecular level on the insulin pathway. In this context, it is also important to note that the mechanism of action for the flavonoids is not fully characterized and that a proper dosage to obtain a beneficial effect on health has not been defined yet. Further investigations will contribute to solve all these critical challenges and will enable the use of flavonoids to prevent, delay or support the treatment of T2D and obesity.

Sweet potato (Ipomoea batatas L.) leaf polyphenols ameliorate hyperglycemia in type 2 diabetes mellitus mice

The hypoglycemic effects and potential mechanism of sweet potato leaf polyphenols (SPLP) on type 2 diabetes mellitus (T2DM) were investigated. Results showed that oral administration of SPLP to mice could alleviate body weight loss, decrease fasting blood glucose levels (by 64.78%) and improve oral glucose tolerance compared with those of untreated diabetic mice. Furthermore, increased fasting serum insulin levels (by 100.11%), ameliorated insulin resistance and improved hepatic glycogen (by 126.78%) and muscle glycogen (increased by 135.85%) were observed in the SPLP treatment group. SPLP also could reverse dyslipidemia, as indicated by decreased total cholesterol, triglycerides, low density lipoprotein-cholesterol and promoted high density lipoprotein-cholesterol. Histopathological analysis revealed that SPLP could relieve liver inflammation and maintain the islet structure to inhibit β-cell apoptosis. A quantitative real-time polymerase chain reaction confirmed that SPLP could up-regulate the phosphatidylinositol 3-kinase/protein kinase B/glycogen synthase kinase-3β signaling pathway to improve glucose metabolism and up-regulate the phosphatidylinositol 3-kinase/protein kinase B/glucose transporter 4 signaling pathway in the skeletal muscle to enhance glucose transport. This study provides useful information to support the application of SPLP as a natural product for the treatment of T2DM.

Diabetes and Cancer: Metabolic Association, Therapeutic Challenges, and the Role of Natural Products

Cancer is considered the second leading cause of death worldwide and in 2018 it was responsible for approximately 9.6 million deaths. Globally, about one in six deaths are caused by cancer. A strong correlation was found between diabetes mellitus and carcinogenesis with the most evident correlation was with type 2 diabetes mellitus (T2DM). Research has proven that elevated blood glucose levels take part in cell proliferation and cancer cell progression. However, limited studies were conducted to evaluate the efficiency of conventional therapies in diabetic cancer patients. In this review, the correlation between cancer and diabetes will be discussed and the mechanisms by which the two diseases interact with each other, as well as the therapeutics challenges in treating patients with diabetes and cancer with possible solutions to overcome these challenges. Natural products targeting both diseases were discussed with detailed mechanisms of action. This review will provide a solid base for researchers and physicians to test natural products as adjuvant alternative therapies to treat cancer in diabetic patients.

Four New Gallate Derivatives from Wine-Processed Corni Fructus and Their Anti-Inflammatory Activities

Four new gallate derivatives—ornusgallate A, ent-cornusgallate A, cornusgallate B and C (1a, 1b, 2, 3)—were isolated from the wine-processed fruit of Cornus officinalis. Among them, 1a and 1b are new natural compounds with novel skeletons. Their chemical structures were elucidated by comprehensive spectroscopy methods including NMR, IR, HRESIMS, UV, ECD spectra and single-crystal X-ray diffraction analysis. The in vitro anti-inflammatory activities of all compounds were assayed in RAW 264.7 cells by assessing LPS-induced NO production. As the result, all compounds exhibited anti-inflammatory activities at attested concentrations. Among the tested compounds, compound 2 exhibited the strongest anti- inflammatory activity.

The impact of ellagic acid on some apoptotic gene expressions: a new perspective for the regulation of pancreatic Nrf-2/NF-κB and Akt/VEGF signaling in CCl4-induced pancreas damage in rats

OBJECTIVE

The aim of this study was to evaluate the potential effect of ellagic acid (EA) in the treatment of pancreatic injury. EA has been found to have strong anti-inflammatory, antioxidative, and anticancer properties. The effects of EA on pancreati˜c star cell (PSC) activation and cell functions have been evaluated and it has been shown that it inhibits the activation of basic cell functions and PSCs and^. it has antidiabetic activity through its effect on β-pancreas cells.

MATERIALS AND METHODS

In this work, 36 Wistar albino rats (n = 36, 8 weeks old) were used. Rats were divided to 4 groups and 9 rats were each group. Groups: Group 1: control group; Group 2: EA group; Group 3: carbon tetrachloride (CCl₄) group; Group 4: EA + CCl₄ group. Animals were decapitated after 8 weeks and their pancreas tissue samples were taken and researched. In pancreas tissue, NF-κB, TNF-α, Nrf-2, VEGF, Bcl-2, caspase-3, and Akt proteins expression ratios were analyzed by western blotting method, CAT activity and GSH levels were determined by spectrophotometer and ROS production was detected by MDA.

RESULTS

In our results, the Nrf-2 and caspase-3 protein expressions, catalase activities and GSH levels increased, TNF-α, NF-κB, Bcl-2, VEGF, and Akt protein expressions and MDA levels reduced in EA + CCl₄ group comparable to the CCl₄ group.

CONCLUSIONS

These findings reveal that EA decreases pancreas tissue injury in rats and that EA may also be used as a drug against pancreas tissue injury in the future.

Antioxidant and α-Glucosidase Inhibitory Activities Guided Isolation and Identification of Components from Mango Seed Kernel

In the present study, petroleum ether, dichloromethane, ethyl acetate, and n-butanol fractions of mango seed kernel exhibited different degrees of antioxidant and α-glucosidase inhibitory activity. Thus, quantitative and qualitative analysis of the petroleum ether fraction was conducted by GC-MS. Among identified components, four unsaturated fatty acids had never been reported in natural products before, together with 19 known components. In addition, 17 compounds were isolated and elucidated from other active fractions. Compounds 2, 9, 15, and 17 were isolated for the first time from Mangifera genus. Compounds 1 and 2 exhibited prominent DPPH radical scavenging and α-glucosidase inhibitory effects. In order to further explore their mechanism of α-glucosidase inhibition, their enzyme kinetics and in silico modeling experiments were performed. The results indicated that 1 inhibited α-glucosidase in a noncompetitive manner, whereas 2 acted in a competitive manner. In molecular docking, the stability of binding was enhanced by π-π T-shaped, π-alkyl, π-π stacked, hydrogen bond, and electrostatic interactions. Thus, compounds 1 and 2 were determined to be new potent antioxidant and α-glucosidase inhibitors for preventing food oxidation and enhancing hypoglycemic activity.

Polyoxygenated seco-cyclohexenes derivatives from flower and leaf extracts of Desmos cochinchinensis and their α-glucosidase inhibitory activity

Phytochemical investigations from the flower and leaf extracts of D. cochinchinensis resulted in the isolation and structural elucidation of five new polyoxygenated seco-cyclohexene derivatives, desmoscochinchinenes A-E (1–5), together with 11 known compounds (6–16). The structures on the new compounds were elucidated from their spectroscopic data, including UV, IR, NMR, and HRESITOFMS. Some of the isolated compounds were evaluated for their α-glucosidase inhibitory activities. Chrysin (9), pinocembrin 7-O-benzoate (12), and (−)-(5R)-desmoscochinoxepinone B (16) inhibited α-glucosidase better than the standard control (acarbose, IC₅₀ = 83.5 μM) with IC₅₀ values of 5.7, 33.8, 53.3 μM, respectively.

Maltoheptaoside hydrolysis with chromatographic detection and starch hydrolysis with reducing sugar analysis: Comparison of assays allows assessment of the roles of direct α-amylase inhibition and starch complexation

The aim was to determine inhibition of human α-amylase activity by (poly)phenols using maltoheptaoside as substrate with direct chromatographic product quantification, compared to hydrolysis of amylose and amylopectin estimated using 3,5-dinitrosalicylic acid. Acarbose exhibited similar IC₅₀ values (50% inhibition) with maltoheptaoside, amylopectin or amylose as substrates (2.37 ± 0.11, 3.71 ± 0.12 and 2.08 ± 0.01 µM respectively). Epigallocatechin gallate, quercetagetin and punicalagin were weaker inhibitors of hydrolysis of maltoheptaoside (<50% inhibition) than amylose (IC₅₀: epigallocatechin gallate = 20.41 ± 0.25 µM, quercetagetin = 30.15 ± 2.05 µM) or amylopectin. Interference using 3,5-dinitrosalicylic acid was in the order punicalagin > epigallocatechin gallate > quercetagetin, with minimal interference using maltoheptaoside as substrate. The main inhibition mechanism of epigallocatechin gallate and punicalagin was through complexation with starch, especially amylose, whereas only quercetagetin additionally binds to the α-amylase active site. Interference is minimised using maltoheptaoside as substrate with product detection by chromatography, potentially allowing assessment of direct enzyme inhibition by almost any compound.

Lipid rafts as potential mechanistic targets underlying the pleiotropic actions of polyphenols

Polyphenols have attracted a lot of global attention due to their diverse biological actions against cancer, obesity, and cardiovascular diseases. Although extensive research has been carried out to elucidate the mechanisms of pleiotropic actions of polyphenols, this remains unclear. Lipid rafts are distinct nanodomains enriched in cholesterol and sphingolipids, present in the inner and outer leaflets of cell membranes, forming functional platforms for the regulation of cellular processes and diseases. Recent studies focusing on the interaction between polyphenols and cellular lipid rafts shed new light on the pleiotropic actions of polyphenols. Polyphenols are postulated to interact with lipid rafts in two ways: first, they interfere with the structural integrity of lipid rafts, by disrupting their structure and clustering of the ordered domains; second, they modulate the downstream signaling pathways mediated by lipid rafts, by binding to receptor proteins associated with lipid rafts, such as the 67 kDa laminin receptor (67LR), epidermal growth factor receptor (EGFR), and others. This study aims to elaborate the mechanism of interaction between polyphenols and lipid rafts, and describe pleiotropic preventive effects of polyphenols.

Spirosteroids and α-glucosidase inhibitory norlignans from Asparagus racemosus Willd. roots

Three undescribed spirosteroids, asparacemosones A-C, an undescribed spiro-21-norsteroid, asparacemosone D, along with seven known compounds were isolated from Thai herbal plant Asparagus racemosus Willd. roots. Their structures were elucidated by spectroscopic analysis including NMR, UV, IR and mass spectrometry. The absolute configurations of asparacemosones A, B, and D were determined by single crystal X-ray diffraction using CuKα radiation. Among the isolated compounds, the norlignan nyasol and three acetylenic norlignans demonstrated potent α-glucosidase inhibition, with IC₅₀ values ranging from 0.003 to 0.004 μM which is 5 × 10⁴ fold more potent than the standard acarbose.

Enhancement of the permeability and activities of epigallocatechin gallate by quaternary ammonium chitosan/fucoidan nanoparticles

Epigallocatechin gallate (EGCG) has many biological functions; however, the use of EGCG in biomedical and food industries was limited due to its poor oral absorption and high susceptibility to degradation. In this study, a mucoadhesive quaternary chitosan was synthesized and combined with fucoidan (FD) (or depolymerized lower molecular weight fucoidan, LMWF) to prepare EGCG-loaded nanoparticles, which extended EGCG release over 300 min and enhanced the transepithelial permeation of EGCG using Caco-2 cells as a model for intestinal absorption. The nanoparticls protected EGCG against degradation in phosphate buffer (pH 6.8) and the remaining EGCG was 1.7-folds higher than the control (EGCG alone). The additive effects of EGCG combined with FD or LMWF in the nanoparticles increased the DPPH radical scavenging activity and the enzyme inhibitory activity against α-amylase (2.82-4.92 fold increase) and α-glucosidase (1.35-1.67 fold increase), while quaternary chitosan helped to enhance the antibacterial effect of EGCG.

Nutraceutical profiling of surimi gel containing β-glucan stabilized virgin coconut oil with and without antioxidants after simulated gastro-intestinal digestion

Surimi gels containing β-glucan stabilized virgin coconut oil (VCO) were subjected to simulated gastrointestinal digestion and the resulting digest was analyzed for nutraceutical properties. β-glucan stabilized VCO nanoemulsion (βG-V-N) remarkably improved antioxidant activities of the surimi digest. When epigallocatechin gallate (EGCG) was added in nanoemulsion, the surimi digest showed the highest antioxidant activities. Antidiabetic activity of the digest was also improved by the addition of βG-V-N comprising EGCG. Nevertheless, the addition of βG-V-N lowered ACE inhibitory activity of surimi digest. The surimi digest from the gel added with βG-V-N possessed an inhibitory effect on five cancer cell lines including HEK (Human embryonic kidney 293 cells), MCF-7 (breast cancer cell line), U87 (human glioma), HeLa (human cervical cancer), and IMR-32 (human neuroblastoma), regardless of EGCG or α-tocopherol incorporated. This study demonstrated that surimi gel supplemented with βG-V-N in the presence of EGCG exhibited nutraceutical potential and could be used as a functional food.

Cultivated Fruit Body of Phellinus baumii: A Potentially Sustainable Antidiabetic Resource

Previous studies have been reported that the fruit body of wild Phellinus baumii alleviates diabetes, and antioxidants are beneficial to diabetes by protecting the β-cell from damage due to oxidative stress. Large-scale cultivation of P. baumii fruit body has been successful in the past decade. This paper aimed to investigate whether the fruit body of the cultivated P. baumii has the same analogical effects as the wild. The cultivated P. baumii fruit body was extracted by 80% of ethanol extracts, and different fractions were obtained with the successive use of petroleum ether, ethyl acetate (EtOAc), n-butanol (n-BuOH), and water, which yielded 15.98 ± 1.56, 1.74 ± 0.34, 3.31 ± 0.41, 4.12 ± 0.37, and 1.38 ± 0.26% extract recovery, respectively. Results show that the EtOAc fraction exhibits the highest inhibitory effect on α-glucosidase activity (IC50 = 49.05 ± 3.14 μg mL-1), which is an order of magnitude higher than the positive control (acarbose, IC50 = 645.73 ± 7.86 μg mL-1). It was mainly composed of phenolic compounds with a purity of 79.45% and characterized by liquid chromatography-mass spectrometry as osmudacetone, hispidin, davallialactone, 2,5-bis(4,7-dihydroxy-8-methyl-2-oxo-2H-chromen-3-yl)cyclohexa-2,5-diene-1,4-dione, hypholomin B, and inoscavin A. Furthermore, the EtOAc fraction increased the glucose consumption of insulin-resistant HepG2 cells at a concentration range of 25-100 μg mL-1. The EtOAc fraction also demonstrated antioxidant activities by scavenging 1,1-diphenyl-2-picrylhydrazyl, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)diammonium salt, and hydroxyl radicals. In conclusion, the EtOAc fraction of the cultivated P. baumii fruit body exerted effective antidiabetic effects, possibly due to the high content of selective phenolic compounds. Hence, the cultivated fruit body of P. baumii can be a sustainable resource for treating diabetes, and our work also shed some light on its future utilization.

The Pharmacological Activity of Camellia sinensis (‎L.‎) ‎Kuntze‎ on Metabolic and Endocrine Disorders: A Systematic Review

Tea made from Camellia sinensis leaves is one of the most consumed beverages worldwide. This systematic review aims to update Camellia sinensis pharmacological activity on metabolic and endocrine disorders. Inclusion criteria were preclinical and clinical studies of tea extracts and isolated compounds on osteoporosis, hypertension, diabetes, metabolic syndrome, hypercholesterolemia, and obesity written in English between 2014 and 2019 and published in Pubmed, Science Direct, and Scopus. From a total of 1384 studies, 80 reports met inclusion criteria. Most papers were published in 2015 (29.3%) and 2017 (20.6%), conducted in China (28.75%), US (12.5%), and South Korea (10%) and carried out with extracts (67.5%, especially green tea) and isolated compounds (41.25%, especially epigallocatechin gallate). Most pharmacological studies were in vitro and in vivo studies focused on diabetes and obesity. Clinical trials, although they have demonstrated promising results, are very limited. Future research should be aimed at providing more clinical evidence on less studied pathologies such as osteoporosis, hypertension, and metabolic syndrome. Given the close relationship among all endocrine disorders, it would be of interest to find a standard dose of tea or their bioactive constituents that would be beneficial for all of them.

Analysis of inhibitory interaction between epigallocatechin gallate and alpha-glucosidase: A spectroscopy and molecular simulation study

Alpha-glucosidase is one of the main enzymes responsible for digesting starch. Inhibiting its activity is therefore being targeted as a strategy for tackling diabetes. Certain food components have the potential to act as natural α-glucosidase (SCG) inhibitors, such as the polyphenols found in tea. In this study, epigallocatechin gallate (EGCG) was shown to strongly inhibit SCG activity (IC₅₀ value = 3.7 × 10^-5 M). Multi-spectroscopic binding molecular simulations indicated that EGCG spontaneously bound to SCG through a combination of hydrogen bonding and hydrophobic interactions. The hypothesis was supported by the results from intrinsic fluorescence quenching, conformational change, surface hydrophobicity decrease, and molecular docking analysis of the SCG after binding. Molecular docking provided powerful visual insights into the nature of the molecular interactions involved. This research provides important new information about the interaction mechanism of EGCG and SCG, which may be beneficial to the development of functional foods to prevent diabetes.

Exploring the structure–activity relationship and interaction mechanism of flavonoids and α-glucosidase based on experimental analysis and molecular docking studies

An integrated method was explored to investigate the structure–activity relationship and interaction mechanism between a library of natural flavonoids and α-glucosidase.

Preparation of theasinensin A and theasinensin B and exploration of their inhibitory mechanism on α-glucosidase

Theasinensin A (TSA) and theasinensin B (TSB), dimers of tea catechins produced during the processing of oolong tea and black tea, had superior inhibitory effects on α-glucosidase.

Utilizing the Combination of Binding Kinetics and Micro-Pharmacokinetics Link in Vitro α-Glucosidase Inhibition to in Vivo Target Occupancy

Many compounds with good inhibitory activity (i.e., high affinity) within in vitro experiments failed in vivo studies due to a lack of efficacy from limited target occupancy (TO) in the drug discovery process. Recently, it was found that rate constants of the formation and dissociation of the binary drug-target complex, rather than affinity, often govern in vivo efficacy. Therefore, the binding kinetics (BK) properties of compound-target interaction are emerging as a pivotal parameter. However, it is obvious that BK rate constants of the compound against target would not be directly linked to the in vivo TO unless the compound concentration in the target vicinity at any time point (TPK) can be evaluated. Here, we developed a novel simulation model to quantitate the dynamic change of target engagement over time in rat with a combined use of BK and TPK features of Epicatechin gallate (ECG) and epigallocatechin gallate (EGCG) on the basis of α-glucosidase (AGH). Analysis of the results displayed that the percent of maximum AGH occupancies by the ECG were varied significantly from 48.9 to 95.3% and by the EGCG slightly from 96 to 99.8%; that the time course of above 70% engagement by ECG spanned a range from 0 to 0.64 h and by EGCG a range of 1.5 to 8.9 h in four different intestinal segments of the rat. It was clearly analyzed how each parameter in the simulation model effected on the in vivo the AGH engagement by ECG and EGCG. Our results provide a novel approach for assessing the potential inhibitory activity of the compounds against AGH.