Binding Of Epigallocatechin-3-gallate Research Articles

Unveiling the Mechanisms of EGCG-p53 Interactions through Molecular Dynamics Simulations.

Green tea consumption is associated with protective and preventive effects against various types of cancer. These effects are attributed to polyphenols, particularly epigallocatechin-3-gallate (EGCG). EGCG acts by directly inhibiting tumor suppressor protein p53. The binding mechanism by which EGCG inhibits p53 activity is associated with residues Trp23-Lys24 and Pro47-Thr55 within the p53 N-terminal domain (NTD). However, the structural and thermodynamic aspects of the interaction between EGCG and p53 are poorly understood. Therefore, based on crystallographic data, we combine docking, molecular dynamics (MD) simulations, and molecular mechanics generalized Born surface area approaches to explore the intricacies of the EGCG-p53 binding mechanism. A triplicate microsecond MD simulation for each system is initially performed to capture diverse p53 NTD conformations. From the start, the most populated cluster of the second run (R2-1) stands out due to a unique opening between Trp23 and Trp53. During MD simulations, this conformation allows EGCG to sustain a high level of stability and affinity while interacting with both regions of interest and deepening the binding pocket. Structural analysis emphasizes the significance of pyrogallol motifs in EGCG binding. Therefore, the conformational shift in this gap is pivotal, enabling EGCG to impede p53 interactions and manifest its anticancer properties. These findings enhance the present comprehension of the anticancer properties of green tea polyphenols and pave the way for future therapeutic developments.

The mechanism of epigallocatechin-3-gallate inhibiting the antigenicity of β-lactoglobulin under pH 6.2, 7.4 and 8.2: Multi-spectroscopy and molecular simulation methods

The antigenicity of β-lactoglobulin (β-LG) can be influenced by pH values and reduced by epigallocatechin-3-gallate (EGCG). However, a detailed mechanism concerning EGCG decreasing the antigenicity of β-LG at different pH levels lacks clarity. Here, we explore the inhibition mechanism of EGCG on the antigenicity of β-LG at pH 6.2, 7.4 and 8.2 using enzyme-linked immunosorbent assay, multi-spectroscopy, mass spectrometry and molecular simulations. The results of Fourier transform infrared spectroscopy (FTIR) and circular dichroism (CD) elucidate that the noncovalent binding of EGCG with β-LG induces variations in the secondary structure and conformations of β-LG. Moreover, EGCG inhibits the antigenicity of β-LG the most at pH 7.4 (98.30 %), followed by pH 6.2 (73.18 %) and pH 8.2 (36.24 %). The inhibitory difference is attributed to the disparity in the number of epitopes involved in the interacting regions of EGCG and β-LG. Our findings suggest that manipulating pH conditions may enhance the effectiveness of antigenic inhibitors, with the potential for further application in the food industry.

Nanocomplex of (−)-epigallocatechin-3-gallate and glycated ovalbumin based on natural deep eutectic solvents: Binding analysis and functional improvement

Natural deep eutectic solvents (NADES) are considered an efficient reaction medium for the production of glycated proteins. By optimizing the Maillard reaction conditions through response surface analysis, a glycation product (GOVA) of ovalbumin (OVA) with high grafting degree (92.2%) was prepared in choline chloride/glucose NADES. The binding information of (−)-epigallocatechin-3-gallate (EGCG) to OVA/GOVA was acquired by fluorescence spectroscopy and molecular docking. The interaction strength of GOVA + EGCG was higher than that of OVA + EGCG. Hydrogen bonding and van der Waals forces were the major driving forces in the binding process. Glycation and EGCG binding reduced the surface hydrophobicity, α-helix content and digestibility of OVA. Compared with OVA, the particle sizes of GOVA and GOVA + EGCG were increased by 54.8% and 87.7%, respectively. In addition, glycation increased the emulsifying activity index and foaming capacity of OVA by 32.6% and 20.0%, respectively, which was further increased in the presence of EGCG. The encapsulation of OVA, especially GOVA, improved the antioxidant activity, stability and bioaccessibility of EGCG. The results suggest that the glycated proteins based on NADES may provide an effective alternative for the protection and transport of bioactive ingredients in the food industries.

Exploring the Interactions of Soybean 7S Globulin with Gallic Acid, Chlorogenic Acid and (-)-Epigallocatechin Gallate.

In this study, the noncovalent interaction mechanisms between soybean 7S globulin and three polyphenols (gallic acid (GA), chlorogenic acid (CA) and (-)-epigallocatechin gallate (EGCG)) were explored and compared using various techniques. Fluorescence experiments showed that GA and EGCG had strong static quenching effects on 7S fluorescence, and that of CA was the result of multiple mechanisms. The interactions caused changes to the secondary and tertiary structure of 7S, and the surface hydrophobicity was decreased. Thermodynamic experiments showed that the combinations of polyphenols with 7S were exothermic processes. Hydrogen bonds and van der Waals forces were the primary driving forces promoting the binding of EGCG and CA to 7S. The combination of GA was mainly affected by electrostatic interaction. The results showed that the structure and molecular weight of polyphenols play an important role in their interactions. This work is helpful for developing products containing polyphenols and soybean protein.

Remodeling the structure of soy protein fibrils to hydrogels for co-encapsulation of (−)-epigallocatechin gallate (EGCG) and curcumin: Role of EGCG

Curcumin (Cur) and (−)-Epigallocatechin gallate (EGCG) have synergistic bioactivity in several terms, but their polar differences and environmental sensitivity make co-utilization challenging. Soy protein fibrils (UF) have sparked broad attention as outstanding carriers for bioactive substances. In this study, EGCG was applied to remodel the structure of Cur-loaded UF complex (UFC) to form novel UF-based hydrogels co-encapsulated Cur and EGCG (UFCE). The fluorescence spectroscopy, ITC, and FTIR analysis demonstrated that EGCG absorbed and deposited on the surface of UFC through hydrophobic and electrostatic interactions. The binding of EGCG led to the formation of UFCE, which constructed a stable and uniform gel network during heat treatment. UFCE gels formed with varying EGCG/protein concentration ([E]/[F]) ratios showed different structural properties with different encapsulation effects. At 2.5% protein concentration, UFCE gels formed at [E]/[F] ratio of 0.08 (UFCE0.08) exhibited better gelling properties. The encapsulation efficiency of Cur and EGCG in UFCE0.08 gel was up to 97.71% and 91.02%, respectively. Moreover, UFCE0.08 gel exhibited significantly enhanced stability of Cur (95.27%) and EGCG (70.27%) than that of free Cur (53.13%) and free EGCG (13.32%) after thermal treatment at 85 °C for 120 min. UFCE0.08 gel was also effective in improving the UV light stability of Cur (88.70%) and EGCG (72.96%). Furthermore, the binding of EGCG had pronouncedly boosted the anticancer activity of Cur in the UFCE0.08 gel against Caco-2 cells. This study provides new perspectives into the fibril-polyphenol hydrogel systems for the co-encapsulation of EGCG and Cur, which has substantial potential for health-promoting applications.

Effects of epigallocatechin gallate, caffeine, and their combination on fat accumulation in high-glucose diet-fed Caenorhabditis elegans.

Epigallocatechin gallate (EGCG) and caffeine are inevitable to be ingested together in the process of drinking green tea. This study used Caenorhabditis elegans as an organism model to examine whether the binding of EGCG and caffeine could influence the fat-reduction effect. The results revealed that EGCG significantly reduced the Nile Red fluorescence intensity and the triglyceride/protein ratio of the C. elegans obesity model by 14.7% and 16.5%, respectively, while the effect of caffeine was not significant. Moreover, the degree of reduction in fluorescence intensity and triglyceride/protein ratio by EGCG+caffeine was comparable to that of EGCG. In the exploration of underlying mechanism, we found that EGCG and EGCG+caffeine treatments had no influence on food intake and energy expenditure of C. elegans. Their fat-reduction effects were dependent on the regulation of lipogenesis, as shown by the decreased expression of the sbp-1, fat-7, and daf-16 genes.

Molecular mechanisms underlying the epigallocatechin-3-gallate-mediated inhibition of oral squamous cell carcinogenesis

ObjectivesTo reveal the mechanisms underlying the epigallocatechin-3-gallate (EGCG)-mediated inhibition of carcinogenesis and the related regulatory signaling pathways. DesignThe effect of EGCG on the proliferation of OSCC cells was examined. SuperPred, ChEMBL, Swiss TargetPrediction, DisGeNET, GeneCards, and National Center for Biotechnology Information databases were used to predict the EGCG target genes and oral leukoplakia (OL)-related, oral submucosal fibrosis (OSF)-related, and OSCC-related genes. The binding of EGCG to the target proteins was simulated using AutoDock and PyMOL. The Cancer Genome Atlas (TCGA) dataset was subjected to consensus clustering analysis to predict the downstream molecules associated with these targets, as well as their potential functions and pathways. ResultsEGCG significantly inhibited OSCC cell proliferation (p < 0.001). By comparing EGCG target genes with genes linked to oral potentially malignant disorder (OPMD) and OSCC, a total of eleven potential EGCG target genes were identified. Furthermore, EGCG has the capacity to bind to eleven proteins. Based on consensus clustering and enrichment analysis, it is suggested that EGCG may hinder the progression of cancer by altering the cell cycle and invasive properties in precancerous lesions of the oral cavity. Some possible strategies for modifying the cell cycle and invasive properties may include EGCG-mediated suppression of specific genes and proteins, which are associated with cancer development. ConclusionsThis study investigated the molecular mechanisms and signaling pathways associated with the EGCG-induced suppression of OSCC. The identification of specific pharmacological targets of EGCG during carcinogenesis is crucial for the development of innovative combination therapies involving EGCG.

Pulsed electric field improves the EGCG binding ability of pea protein isolate unraveled by multi-spectroscopy and computer simulation

Understanding molecular mechanisms during protein modification is critical for expanding the application of plant proteins. This study investigated the conformational change and molecular mechanism of pea protein isolate (PPI) under pulsed electric field (PEF)-assisted (-)-Epigallocatechin-Gallate (EGCG) modification. The flexibility of PPI was significantly enhanced after PEF treatment (10 kV/cm) with decrease (23.25 %) in α-helix and increase (117.25 %) in random coil. The binding constant and sites of PEF-treated PPI with EGCG were increased by 2.35 times and 10.00 % (308 K), respectively. Molecular docking verified that PEF-treated PPI had more binding sites with EGCG (from 4 to 10). The number of amino acid residues involved in hydrophobic interactions in PEF-treated PPI-EGCG increased from 5 to 13. PEF-treated PPI-EGCG showed a significantly increased antioxidant activity compared to non-PEF-treated group. This work revealed the molecular level of PEF-assisted EGCG modification of PPI, which will be significant for the application of PPI in food industry.

Inhibitive and Destructive Mechanisms of Chronic Traumatic Encephalopathy-Related R3-R4 Tau Peptide Chains and Protofibril by Epigallocatechin Gallate: Evidence from Molecular Dynamics Simulation.

Chronic traumatic encephalopathy (CTE), a unique tauopathy, is pathologically associated with the aggregation of hyperphosphorylated tau protein into fibrillar aggregates. Inhibiting tau aggregation and disaggregating tau protofibril might be promising strategies to prevent or delay the development of CTE. Newly resolved tau fibril structures from deceased CTE patients' brains show that the R3-R4 fragment of tau forms the core of the fibrils and the structures are distinct from other tauopathies. An in vitro experiment finds that epigallocatechin gallate (EGCG) can effectively inhibit human full-length tau aggregation and disaggregate preformed fibrils. However, its inhibitive and destructive effects on the CTE-related R3-R4 tau and the underlying molecular mechanisms remain elusive. In this study, we performed extensive all-atom molecular dynamics simulations on the CTE-related R3-R4 tau dimer/protofibril with and without EGCG. The results reveal that EGCG could reduce the β-sheet structure content of the dimer, induce the dimer to form loosely packed conformations, and impede the interchain interactions, thus inhibiting the further aggregation of the two peptide chains. Besides, EGCG could reduce the structural stability, decrease the β-sheet structure content, reduce the structural compactness, and weaken local residue-residue contacts of the protofibril, hence making the protofibril disaggregated. We also identified the dominant binding sites and pivotal interactions. EGCG preferentially binds with hydrophobic, aromatic, and positively/negatively charged residues of the dimer, while it tends to bind with polar, hydrophobic, aromatic, and positively charged residues of the protofibril. Hydrophobic, hydrogen-bonding, π-π stacking, and cation-π interactions synergistically drive the binding of EGCG on both the dimer and the protofibril, but anion-π interaction only exists in the interaction of EGCG with the dimer. Our work unravels EGCG's inhibitive and destructive effects on the CTE-related R3-R4 tau dimer/protofibril and the underlying molecular mechanisms, which provides useful implications for the design of drugs to prevent or delay the progression of CTE.

Effects of epigallocatechin-3-gallate on the structural hierarchy of the gluten network in dough

This study examined the effects of epigallocatechin-3-gallate (EGCG) concentration on the structural hierarchy of the gluten network in dough. At micro scale, 1.0% or higher EGCG destroyed the continuity of the gluten network, which was proved by the increase of lacunarity and almost doubling at 2.0% EGCG. At nano-scale, the increase of EGCG concentration significantly (p < 0.05) raised the proportion of the bulk water and lowered the bound water, and significantly reduced the amount of glutenin macromolecule in the dough. At atomic scale, EGCG (≥0.8%) reduced covalent bonds (mainly disulfide bonds in gluten) to dis-aggregate gluten network, but significantly increased the hydrogen bonds, ionic bonds, and hydrophobic interactions to aggregate. In non-covalent bonds, the hydrophobic interaction has positively linearly correlation with the amount of EGCG, indicating that it is the main driving force for EGCG binding gluten, thereby the burial of tryptophan in the tertiary structure of gluten happened. However, at the molecular level, EGCG increased the ratio of aggregate and β-turns, and decreased α-helix in the secondary structure as well as disulfide bridge g-g-g conformation, but not significantly raised in general β-sheet. These unstable secondary structure and disulfide bridge conformation suggested gluten disaggregation caused by EGCG disruption of disulfide bonds outweighed gluten aggregation it promoted through non-covalent bonds, resulting in a loose aggregation morphology of gluten and a discontinuous gluten network.

The interaction mechanism and the functionality of yeast protein with hydrophilic and hydrophobic bioactive molecules

Yeast protein is a kind of yeast-source high-quality complete protein. The coexistence of bioactive molecules with yeast protein may influence its physicochemical property. This study discussed the interaction mechanism of yeast protein with two bioactive molecules, the hydrophobic curcumin and the hydrophilic epigallocatechin gallate (EGCG). Results indicated that curcumin and EGCG could interact with yeast protein with different binding stoichiometric numbers (0.8109 ± 0.0695 and 2.7248 ± 0.2422) and binding constants ((3.8152 ± 0.0078) × 104 and (1.1875 ± 0.0440) × 105), respectively. Both EGCG and curcumin decreased the α-helix content while increased the β-sheet proportion, and co-binding remarkably reduced the α-helix proportion relative to the single ligand binding. The co-binding of these two compounds decreased the association extent of the yeast protein, which in turn reduced the diameter of yeast protein-EGCG-curcumin complex. The binding of EGCG with yeast protein improved the thermal stability of curcumin. Moreover, the co-binding improved the emulsification stability of yeast protein, and curcumin exhibited a more remarkable effect in improving the foamability. This work provides a theoretical basis for clarifying the interaction mechanisms of hydrophobic/hydrophilic molecules with yeast protein, and extends the potential applications of the novel fungus protein sources for food function enhancement and bioactive molecule stabilization.

How oxidized EGCG remodels α-synuclein fibrils into non-toxic aggregates: insights from computational simulations.

The misfolding and aggregation of the presynaptic protein α-synuclein (α-syn) is a pathological hallmark of Parkinson's disease (PD). Targeting α-syn has emerged as a promising therapeutic strategy for PD. Emerging in vitro evidence supports a dual action of epigallocatechin-3-gallate (EGCG) against amyloid neurotoxicity. EGCG can halt the formation of toxic aggregates by redirecting the amyloid fibril aggregation pathway toward non-toxic aggregates and remodeling the existing toxic fibrils into non-toxic aggregates. Moreover, EGCG oxidation can enhance fibril's remodeling by forming Schiff bases, leading to crosslinking of the fibril. However, this covalent modification is not required for amyloid remodeling, and establishing non-specific hydrophobic interactions with sidechains seems to be the main driver of amyloid remodeling by EGCG. Thioflavin (ThT) is a gold standard probe to detect amyloid fibrils in vitro, and oxidized EGCG competes with ThT for amyloid fibrils' binding sites. In this work, we performed docking and molecular dynamics (MD) simulations to gain insights into the intermolecular interactions of oxidized EGCG and ThT with a mature α-syn fibril. We find that oxidized EGCG moves within lysine-rich sites within the hydrophobic core of the α-syn fibril, forming aromatic and hydrogen-bonding (H-bond) interactions with different residues during the whole MD simulation time. In contrast, ThT, which does not remodel amyloid fibrils, was docked to the same sites but only via aromatic interactions. Our findings suggest that non-covalent interactions play a role in oxidized EGCG binding into the hydrophobic core, including H-bond and aromatic interactions with some residues in the amyloid remodeling processes. These interactions would ultimately lead to a disturbance of structural features as determinants for stabilizing this fibril into a compact and pathogenic Greek key topology.

(-)-Epigallocatechin Gallate is a Noncompetitive Inhibitor of NAD Kinase.

Nicotinamide adenine dinucleotide kinase (NADK) controls the intracellular NADPH content and provides reducing power for the synthesis of macromolecules and anti-ROS. Moreover, NADK is considered to be a synthetic lethal gene for KRAS mutations. To discover NADK-targeted probes, a high-throughput screening assay was established and optimized with a Z factor of 0.71. The natural product (-)-epigallocatechin gallate (EGCG) was found to be a noncompetitive inhibitor of NADK with K i = 3.28 ± 0.32 μΜ. The direct binding of EGCG to NADK was determined by several biophysical methods, including NMR spectroscopy, surface plasmon resonance (SPR) assay, and hydrogen-deuterium exchange mass spectrometry (HDX-MS). The SPR assay showed a K d of 1.78 ± 1.15 μΜ. The HDX-MS experiment showed that EGCG was bound at the non-substrate-binding sites of NADK. Besides, binding mode prediction and derivative activity analysis revealed a potential structure-activity relationship between EGCG and NADK. Furthermore, EGCG can specifically inhibit the proliferation of KRAS-mutated lung cancer cell lines without affecting KRAS wild-type lung cancer cell lines.

Epigallocatechin-3-gallate mediated self-assemble behavior and gelling properties of the ovalbumin with heating treatment

Ovalbumin (OVA), is the most abundant protein in the egg white. In the present study, the effects of Epigallocatechin-3-gallate (EGCG) on the self-assembly behavior and gelling properties of OVA with different heating time were investigated. Electrophoresis, surface hydrophobicity, Fourier transform infrared (FTIR) spectroscopy and molecular docking analysis indicated that hydrophobic force and hydrogen bond were the predominant interactions between EGCG and OVA. The binding of EGCG to OVA suppressed the formation of fibrils as evidenced by the results of Thioflavin T (ThT) intensity and atomic force microscopy (AFM) analysis. When heated for 15–30 min, EGCG addition, especially at 2.5 μM/g, resulted in a decrease of ThT fluorescence intensity and hydrophobicity of OVA samples, and a formation of dense linear aggregates. However, the OVA solution did not form a gel. In a longer heating time of 45 min, 5 μM/g EGCG induced a significant decrease in ThT fluorescence intensity and hydrophobicity of OVA samples, and a transition from the dense linear aggregates to the dense spherical clusters. Therefore, the OVA samples realized the transition from the solution state to the gel state with a higher storage modulus (G′). When the heating time was extended to 60 min, all the OVA samples formed gel and reached the highest G′ at 5 μM/g EGCG. These results suggested that the suitable hydrophobic interactions and hydrogen bonds between EGCG and the OVA improved gel quality. Polyphenol binding provided a new way to regulate the assembly behavior and gelling properties of OVA. • EGCG bound with OVA mainly through hydrophobic interactions and hydrogen bonds. • EGCG mediated self-assemble behavior and gelling properties of the OVA. • The binding of EGCG suppressed the heat-induced fibrils of the OVA. • EGCG (5 μM/g) changed the topology of the OVA aggregates heated for 45–60 min. • EGCG (5 μM/g) drove the formation of the OVA gel heated for 45–60 min.

Vitamin E functions by association with a novel binding site on the 67 kDa laminin receptor activating diacylglycerol kinase

It is generally recognized that the main function of α-tocopherol (αToc), which is the most active form of vitamin E, is its antioxidant effect, while non-antioxidant effects have also been reported. We previously found that αToc ameliorates diabetic nephropathy via diacylglycerol kinase alpha (DGKα) activation in vivo, and the activation was not related to the antioxidant effect. However, the underlying mechanism of how αToc activates DGKα have been enigmatic. We report that the membrane-bound 67 kDa laminin receptor (67LR), which has previously been shown to serve as a receptor for epigallocatechin gallate (EGCG), also contains a novel binding site for vitamin E, and its association with Vitamin E mediates DGKα activation by αToc. We employed hydrogen-deuterium exchange mass spectrometry (HDX/MS) and molecular dynamics (MD) simulations to identify the specific binding site of αToc on the 67LR and discovered the conformation of the specific hydrophobic pocket that accommodates αToc. Also, HDX/MS and MD simulations demonstrated the detailed binding of EGCG to a water-exposed hydrophilic site on 67LR, while in contrast αToc binds to a distinct hydrophobic site. We demonstrated that 67LR triggers an important signaling pathway mediating non-antioxidant effects of αToc, such as DGKα activation. This is the first evidence demonstrating a membrane receptor for αToc and one of the underlying mechanisms of a non-antioxidant function for αToc.

Interaction of Pyrogallol-Containing Polyphenols with Mucin Reinforces Intestinal Mucus Barrier Properties.

High consumption of polyphenol-rich green tea, coffee, fruits, and vegetables is associated with a low risk of human chronic diseases. Recent studies highlight the relevance of polyphenol-mediated gut microbiota modulation and its impact on mucus barrier. Herein, we study the direct interaction of epicatechin (EC), epigallocatechin gallate (EGCG), and tannic acid (TA) with intestinal mucin by isothermal titration calorimetry and multiple particle tracking and the impact on mucus barrier using ex vivo mucus and Caco-2/HT29-MTX cocultures. Results show that pyrogallol-containing polyphenols EGCG and TA exhibit strong binding to intestinal mucin and reinforce mucus barrier, whereas EC does not. ECGG and TA also mitigate gliadin-mediated cytotoxicity and inflammation. The chemical binding of EGCG and TA to the nucleophilic thiol groups of mucins shows their roles as cross-linkers of mucin networks. These results bring a novel understanding of the health benefits of polyphenols and provide support for the consumption of pyrogallol-containing beverages like green tea as a potential dietary therapy for gluten-related disorders.

Action mechanisms of two key xanthine oxidase inhibitors in tea polyphenols and their combined effect with allopurinol.

Tea polyphenols have been reported to have the effect of lowering uric acid. However, there are few studies on the inhibitory effects and molecular mechanisms of specific catechins on the urate-metabolizing enzyme xanthine oxidase (XO). In this research, multiple spectroscopic methods and computer simulations were used to determine the inhibitory ability and mechanisms of epigallocatechin gallate (EGCG) and gallocatechin gallate (GCG) on XO. Herein, EGCG and GCG reversibly inhibited XO activity in a mixed manner, with IC50 values of 40.50 ± 0.32 and 33.60 ± 0.53 μmol L-1 , and also decreased the superoxide anion radical (O2 - ) of the catalytic system by reducing the XO molecule and inhibiting the formation of uric acid. The combination of EGCG or GCG with allopurinol showed synergistic inhibition on XO. The binding of EGCG or GCG to XO with moderate affinity formed a stable complex by hydrogen bonds and van der Waals forces. The presence of EGCG and GCG made the structure of XO more stable and compact. The two inhibitors bound to the vicinity of flavin adenine dinucleotide (FAD) in XO, hindering the entry of substrate; thus the activity of XO was suppressed. Both EGCG and GCG are excellent natural XO inhibitors, and inhibited the activity of XO by occupying the channel of the substrate to enter the active center and interfering with the dual substrate reaction catalyzed by XO. These findings provide a scientific basis for the application of catechins in dietary supplements and medicines with lowering uric acid effects. © 2022 Society of Chemical Industry.

Enzymic catalyzing affinity to substrate affects inhibitor-enzyme binding interactions: Inhibition behaviors of EGCG against starch digestion by individual and co-existing α-amylase and amyloglucosidase

The inhibition of (-)-epigallocatechin-gallate (EGCG) against starch digestion by α-amylase (AA), amyloglucosidase (AMG) and co-existing enzymes (AA/AMG) were comparatively studied. EGCG inhibited AA only at slowly-digestible-starch (SDS) phase. This resulted from high catalytic efficiency of AA for rapidly-digestible-starch (RDS), counteracting the inhibition at this phase. EGCG inhibited AMG and AA/AMG during whole process. At RDS phase, the catalytic velocity of AMG was always higher than AA/AMG because of an antagonistic effect of two enzymes. However, at SDS phase with EGCG, the catalytic velocity of AA/AMG was higher than AMG. This is because binding of EGCG with both enzymes caused more unbound AMG that generated more glucose in co-existing AA/AMG than AMG. Although EGCG-AA binding affinity was higher than EGCG-AMG, competitive inhibition of EGCG against AA was weaker than AMG, indicating relatively higher binding/catalyzing affinity of AA to starch significantly weakened EGCG-AA binding due to competitive relationship between starch and EGCG.

Competitive binding of synergistic antioxidant chlorogenic acid and (−)-epigallocatechin gallate with lysozyme: Insights from multispectroscopic characterization, molecular docking and activity evaluation

The individual and combined binding of two active polyphenols, (−)-epigallocatechin gallate (EGCG) and chlorogenic acid (CGA), to lysozyme was studied at the molecular level by multispectroscopic techniques and molecular docking. The thermodynamic parameters obtained from fluorescence data indicated that the main driving force for the binding of CGA to lysozyme was electrostatic interaction while the binding of EGCG was mainly driven by hydrogen bonding and van der Waals’ forces. The results of circular dichroism spectroscopy and dynamic light scattering showed that the α-helical content and particle size of lysozyme decreased and increased, respectively, in the presence of EGCG and/or CGA. The competitive binding of EGCG and CGA to lysozyme was confirmed by molecular docking. The binding of EGCG and/or CGA inhibited the activity of lysozyme. The combination of EGCG and CGA had synergistic antioxidant activity and cytotoxicity to HeLa cells. Response surface methodology was used to analyze the maximum synergistic antioxidant activity between EGCG and CGA. The lysozyme + EGCG/CGA interaction weakened and enhanced the antioxidant activity and cytotoxicity of EGCG/CGA, respectively. These results would provide ideas for the combined application of EGCG and CGA in the fields of functional foods and pharmaceuticals.

Explore the interaction mechanism between zein and EGCG using multi-spectroscopy and molecular dynamics simulation methods

Zein as a kind of carrier material has attracted extensive interest, while the interaction mechanism between zein and nutrients is still elusive. In this work, the binding mechanism of zein with epigallocatechin-3-gallate (EGCG) was investigated via multi-spectroscopy and molecular dynamics (MD) simulation. The quenching of zein by EGCG is mainly static quenching, and the secondary structure of zein is slightly changed after the binding of EGCG to zein. The formation of Zein-EGCG complexes was confirmed by ultraviolet–visible (UV–Vis) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). Molecular dynamics (MD) simulation clarified that the EGCG prefers to bind to the pocket of zein formed by residues Y171, Q174, L176 and L205. Electrostatic and van der Waals interactions played a dominant role for the binding of EGCG to zein, which was consistent with the results by fourier transform infrared spectroscopy (FTIR) and thermodynamic analysis. This study provides new insights into the interaction mechanism between zein and EGCG, which is very important to develop plant protein as tea polyphenol delivery system.