A multi-spectroscopic study on the interaction of food polyphenols with a bioactive gluten peptide: From chemistry to biological implications

Optical weak measurements for protein-polyphenol interactions: A novel detection approach

Protein-polyphenol interactions are crucial in food chemistry, yet current detection methods have limitations. This study innovatively uses optical weak measurement. Key variables like central wavelength shifts were measured in systems with chlorogenic acid, tea polyphenols, and various proteins. A linear relationship between polyphenol concentration and wavelength shift was found, and a new calculation strategy for binding constants and sites was developed, showing consistent trends with fluorescence quenching. The method is label-free and applicable to non-immobilized biomolecules, offering cost-effective and accurate detection. However, it's sensitive to solution fluctuations and complex samples. Future research should optimize the device and detection techniques to improve stability and capture interaction dynamics. This study provides a valuable tool for food chemistry research.

Mechanism of structural and functional changes of matcha bread dough during freezing storage

This study aimed to investigate the effects of freezing duration and matcha concentration on the rheological properties, moisture distribution, and multiscale structure of dough. The results indicated that both freezing and high concentrations of matcha (≥1 %) significantly reduced the stiffness of the dough matrix, restricted its ability to expand during fermentation, and disrupted the structure of gluten protein. Furthermore, freezing induced moisture redistribution within the dough. Specifically, the water content in the 0 % matcha dough decreased by 1.5 %, indicating a weakening of protein-moisture interactions, disruption of disulfide bond conformations, and inhibition of disulfide bond aggregation in gluten proteins, thereby destabilizing the gluten network. Additionally, freezing negatively impacted yeast gas production capability, while matcha addition did not influence yeast activity. Moreover, low concentrations of matcha did not significantly impact the multiscale structure of the dough. This study provided crucial scientific insights for recipe optimization and quality control in bread production.

The Membrane-Targeting Synergistic Antifungal Effects of Walnut-Derived Peptide and Salicylic Acid on Prickly Pear Spoilage Fungus

Fermented walnut (FW) meal exhibits antifungal activity against Penicillium victoriae (the fungus responsible for prickly pear spoilage), which is mainly attributed to the synergistic effect of antimicrobial peptides and salicylic acid (SA). This study aimed to investigate the synergistic mechanism between YVVPW (YW-5, the peptide with the highest antifungal activity) and SA against the cell membrane of P. victoriae. Treatment enhanced prickly pear's rot rate, polyphenol concentration, and superoxide dismutase (SOD) activity by 38.11%, 8.11%, and 48.53%, respectively, while reducing the microbial count by 19.17%. Structural analyses revealed β-sheets as YW-5's predominant structure (41.18%), which increased to 49.0% during SA interaction. Molecular docking demonstrated YW-5's stronger binding to β-(1,3)-glucan synthase and membrane protein amino acids via hydrogen bonds, hydrophobic forces, and π-π conjugate interactions. Spectroscopic analyses demonstrated SA's major role in YW-5 synergy at the interface and polar head region of phospholipids, enhancing lipid chain disorder and the leakage of cell components. Malondialdehyde and SOD levels increased nearly two-fold and six-fold when treated with YW-5/SA, and YW-5 showed a more pronounced effect. Scanning electron and transmission electron microscopy confirmed that SA caused greater damage to spore morphology and cell ultrastructure. These findings support this formulation's functions as an efficient antifungal substance in fruit storage.

The synergistic effects of rice bran rancidity and dephenolization on digestive properties of rice bran protein

Both rice bran (RB) rancidity and dephenolization could affect the structural characteristics and phenolics composition of rice bran protein (RBP), thereby affecting RBP digestibility. The synergistic effects of RB rancidity and dephenolization on RBP digestibility were investigated. Excessive RB rancidity (RB stored for 10 d) and non-dephenolization reduced RBP digestibility, while moderate RB rancidity (RB stored for 1 d) combined with dephenolization improved RBP digestibility to a maximum of 74.19%. Dephenolization reduced the antioxidant capacities of RBP digestive products. The digestibility of non-dephenolized RBP (NDRBP) was significantly (P < 0.05) related with its carbonyl content, surface hydrophobicity, and ζ-potential. The digestibility of dephenolized RBP (DRBP) was significantly related with its β-sheet structure content, surface hydrophobicity, ζ-potential, and average particle size. Overall, moderate RB rancidity combined with dephenolization enhanced RBP digestibility by reducing the non-competitive inhibition of endogenous phenolics on protease and regulating the spatial structural characteristics of RBP.

Potential of nutraceuticals in celiac disease

Celiac Disease (CD) is the most common hereditarily-based food intolerance worldwide and a chronic inflammatory condition. The current standard treatment for CD involves strict observance and compliance with a gluten-free diet (GFD). However, maintaining a complete GFD poses challenges, necessitating the exploration of alternative therapeutic approaches. Nutraceuticals, bioactive products bridging nutrition and pharmaceuticals, have emerged as potential candidates to regulate pathways associated with CD and offer therapeutic benefits. Despite extensive research on nutraceuticals in various diseases, their role in CD has been relatively overlooked. This review proposes comprehensively assessing the potential of different nutraceuticals, including phytochemicals, fatty acids, vitamins, minerals, plant-based enzymes, and dietary amino acids, in managing CD. Nutraceuticals exhibit the ability to modulate crucial CD pathways, such as regulating gluten fragment accessibility and digestion, intestinal barrier function, downregulation of tissue transglutaminase (TG2), intestinal epithelial morphology, regulating innate and adaptive immune responses, inflammation, oxidative stress, and gut microbiota composition. However, further investigation is necessary to fully elucidate the underlying cellular and molecular mechanisms behind the therapeutic and prophylactic effects of nutraceuticals for CD. Emphasizing such research would contribute to future developments in CD therapies and interventions.

Encapsulation of zingerone by self-assembling peptides derived from fish viscera: Characterization, interaction and effects on colon epithelial cells

The purpose of the present work was to encapsulate zingerone (a bioactive compound from ginger) by self-assembling peptides derived from fish viscera. The encapsulation conditions were investigated and the structure of fish peptides-zingerone complex was characterized. The interaction between zingerone and fish peptides was investigated using fluorescence spectroscopy. Further research was performed on the in vitro release of zingerone and fish peptide-zingerone as well as their antiproliferative effects on colon epithelial Caco-2 cells. The results demonstrated that zingerone can be successfully encapsulated by self-assembling peptides derived from fish viscera with high encapsulation efficiency and loading capacity. Furthermore, transmission electron microscope and confocal laser scanning microscope observations revealed the successful encapsulation of zingerone by fish viscera peptides. In addition, in vitro release and antiproliferative activity against Caco-2 cells can be significantly increased by encapsulating zingerone via peptide self-assembly. The current study advances knowledge of encapsulation of bioactive compounds through peptide self-assembly.

Isolation, identification, and synergistic mechanism of a novel antimicrobial peptide and phenolic compound from fermented walnut meal and their application in Rosa roxbughii Tratt spoilage fungus

This study aimed to identify an antimicrobial peptide and phenolic compound combination derived from fermented walnut meal against Penicillium. victoriae, a fungus responsible for Rosa. roxbughii Tratt spoilage, and ultimately investigate their synergistic mechanism. YVVPW and salicylic acid (SA) had the highest antifungal activity among identified 4 antimicrobial peptides, including FGGDSTHP, ALGGGY, YVVPW, and PLLRW, and 15 phenolic compounds, respectively. Molecular docking verified that YVVPW bound to regulatory subunit via hydrogen-bond, hydrophobic, and π-π conjugate interactions. YVVPW and SA exhibited synergistic effects with average minimal inhibitory concentration decreasing by 85.44 ± 8.04%. Fluorescence spectroscopy demonstrated quenching of intrinsic Trp and Tyr fluorescence by interaction. FTIR and molecular docking results revealed formation of 3 hydrogen bonds via OH, CO, NH, and CH bonds in YVVPW + SA, with π-π stacking occurring between the benzene ring and five-membered ring. These reinforce potential application of this combination as an effective fungistatic combination in fruit preservation.

The Role of Gluten in Food Products and Dietary Restriction: Exploring the Potential for Restoring Immune Tolerance

Wheat is extensively utilized in various processed foods due to unique proteins forming from the gluten network. The gluten network in food undergoes morphological and molecular structural changes during food processing, affecting the final quality and digestibility of the food. The present review introduces the formation of the gluten network and the role of gluten in the key steps of the production of several typical food products such as bread, pasta, and beer. Also, it summarizes the factors that affect the digestibility of gluten, considering that different processing conditions probably affect its structure and properties, contributing to an in-depth understanding of the digestion of gluten by the human body under various circumstances. Nevertheless, consumption of gluten protein may lead to the development of celiac disease (CD). The best way is theoretically proposed to prevent and treat CD by the inducement of oral tolerance, an immune non-response system formed by the interaction of oral food antigens with the intestinal immune system. This review proposes the restoration of oral tolerance in CD patients through adjunctive dietary therapy via gluten-encapsulated/modified dietary polyphenols. It will reduce the dietary restriction of gluten and help patients achieve a comprehensive dietary intake by better understanding the interactions between gluten and food-derived active products like polyphenols.

Interaction mechanism of carotenoids and polyphenols in mango peels

In this study, carotenoids and polyphenols were demonstrated to be the major active substances in the crude pigment extracts (CPE) of mango peels, accounting for 0.26 mg/g and 0.15 mg/g, respectively. The interactions between carotenoids and polyphenols in CPE was observed, as evidenced by that polyphenols significantly improved the antioxidant activity and storage stability of carotenoids in the CPE. Meanwhile, scanning electron microscopy showed that polyphenols are tightly bound to carotenoids. To further elucidate the interaction mechanism, the monomers of carotenoids and polyphenols were identified by HPLC and LC-MS analysis. Lutein (203.85 μg/g), β-carotene (41.40 μg/g), zeaxanthin (4.20 μg/g) and α-carotene (1.50 μg/g) were authenticated as the primary monomers of carotenoids. Polyphenols were mainly consisted of gallic acid (95.10 μg/g), quercetin-3-β-glucoside (29.10 μg/g), catechin (11.85 μg/g) and quercetin (11.55 μg/g). The interaction indexes between carotenoid and polyphenol monomer of CPE were calculated. The result indicated that lutein and gallic acid showed the greatest synergistic effect on the scavenging of DPPH and ABTS radical, suggesting the interaction between carotenoids and polyphenols in CPE was mainly caused by lutein and gallic acid. Molecular dynamics simulations and thermodynamic parameters analysis demonstrated that hydrogen bonding, electrostatic interactions, and van der Waals forces played dominant roles in the interaction between lutein and gallic acid, which was confirmed by Raman and X-ray diffraction. These results provided a new perspective on the interaction mechanism between carotenoids and polyphenols, which offered a novel strategy for the enhancement of the activities and stability of bioactive substances.

Structure relationship of non-covalent interactions between lotus seedpod oligomeric procyanidins and glycated casein hydrolysate during digestion

Procyanidin-amino acid interactions during transmembrane transport cause changes in the structural and physical properties of peptides, which limits further absorption of oligopeptide-advanced glycation end products (AGEs). In this study, glycated casein hydrolysates (GCSHs) were employed to investigate the structure and interaction mechanism of GCSH with lotus seedpod oligomeric procyanidin (LSOPC) complexes in an intestinal environment. LSOPC can interact with GCSH under certain conditions to form hydrogen bonds and hydrophobic interactions to form GCSH-LSOPC complexes. Results showed that procyanidin further leads to the transformation of a GCSH secondary structure and the increase of surface hydrophobicity (H0). The strongest non-covalent interaction between GCSH and (-)-epigallocatechin gallate (EGCG) was due to the polyhydroxy structure of EGCG. Binding site analysis showed that EGCG binds to the internal cavity of P1 to maintain the relative stability of the binding conformation. The antioxidant capacity of GCSH was remarkably elevated by GCSH-LSOPC. This study will provide a new reference for the accurate control of oligopeptide-AGEs absorption by LSOPC in vivo.

Non-Celiac Gluten Sensitivity and Protective Role of Dietary Polyphenols

Pathogenetically characterized by the absence of celiac disease and wheat allergy, non-celiac gluten sensitivity (NCGS) is a clinical entity triggered by the consumption of gluten-containing foods that relieved by a gluten-free diet. Since it is very difficult to maintain a complete gluten-free diet, there is a high interest in discovering alternative strategies aimed at reducing gluten concentration or mitigating its toxic effects. Plant-based dietary models are usually rich in bioactive compounds, such as polyphenols, recognized to prevent, delay, or even reverse chronic diseases, including intestinal disorders. However, research on the role of polyphenols in mitigating the toxicity of gluten-containing foods is currently limited. We address the metabolic fate of dietary polyphenols, both as free and bound macromolecule-linked forms, with particular reference to the gastrointestinal compartment, where the concentration of polyphenols can reach high levels. We analyze the potential targets of polyphenols including the gluten peptide bioavailability, the dysfunction of the intestinal epithelial barrier, intestinal immune response, oxidative stress and inflammation, and dysbiosis. Overall, this review provides an updated overview of the effects of polyphenols as possible dietary strategies to counteract the toxic effects of gluten, potentially resulting in the improved quality of life of patients with gluten-related disorders.

New-Level Insights into the Effects of Grape Seed Polyphenols on the Intestinal Processing and Transport of a Celiac Disease Immunodominant Peptide

The effect of three dietary tannins (procyanidin B3, B6, and T2) on the bioavailability of the 32-mer gliadin-derived immunogenic peptide was evaluated. An enterocyte-like Caco-2 cell line was used to mimic the epithelial transport of the 32-mer peptide, which was modeled by kinetic parameters with a mass spectrometry approach. The hydrolysis pattern on the enterocytes was analyzed, and the released peptides were quantified during the assay. The transport flux was dose-dependent. Along with procyanidin T2 and B6, procyanidin B3 promoted a significant inhibition mainly at the 100 μM peptide concentration. The hydrolysis efficiency was affected by procyanidins, while the cleavage pattern was suggested to be promoted by brush-border membranes at the apical compartment. The ability of procyanidins to molecularly bind to immunogenic peptides able to induce an adaptive response arose as a mechanism able to modulate their bioavailability, bioaccesibility, and further T CD4+ cell activation and expansion in a celiac disease (CD) model.

Effect of Scomberomorus niphonius peptide on the characteristics of resveratrol

Resveratrol has a variety of physiological activities, but its bioavailability in the body is low. In this study, the interaction between the peptide SH, prepared from Scomberomorus niphonius, and resveratrol was judged by fluorescence spectroscopy. Then, SHa1 was obtained by the purification of SH, and its effect on the characteristics of resveratrol was studied. SHa1 interacted with resveratrol at 37 °C for 30 min to obtain the complex SHa1-R, which then showed an obviously stronger inhibition on B16 cells than resveratrol using the MTT assay after in vitro gastrointestinal digestion. The solubility and digestive stability of SHa1-R were higher than that of free resveratrol. The intestinal absorption rate of SHa1-R was also increased compared with resveratrol according to the non-inverted rat intestinal sac model. The structure of SHa1 was analyzed by UPLC, auto amino acid analysis, and UPLC-MS/MS. The molecular weight of SHa1 was mainly concentrated under 1000 Da, and it was rich in glutamic acid, aspartic acid, lysine, and leucine. Eighteen possible peptides were identified from SHa1. The results suggested that the peptide SHa-1 may help to increase the bioavailability of resveratrol by increasing the solubility, digestive stability and intestinal absorption of resveratrol, thereby promoting its inhibitory effect on B16 cells.

Pharmacological Properties of Polyphenols: Bioavailability, Mechanisms of Action, and Biological Effects in In Vitro Studies, Animal Models, and Humans

Drugs are bioactive compounds originally discovered from chemical structures present in both the plant and animal kingdoms. These have the ability to interact with molecules found in our body, blocking them, activating them, or increasing or decreasing their levels. Their actions have allowed us to cure diseases and improve our state of health, which has led us to increase the longevity of our species. Among the molecules with pharmacological activity produced by plants are the polyphenols. These, due to their molecular structure, as drugs, also have the ability to interact with molecules in our body, presenting various pharmacological properties. In addition, these compounds are found in multiple foods in our diet. In this review, we focused on discussing the bioavailability of these compounds when we ingested them through diet and the specific mechanisms of action of polyphenols, focusing on studies carried out in vitro, in animals and in humans over the last five years. Knowing which foods have these pharmacological activities could allow us to prevent and aid as concomitant treatment against various pathologies.

Barks of Three Wild Pyrus Taxa: Phenolic Constituents, Antioxidant Activity, and in Vitro and in Silico Investigations of α-Amylase and α-Glucosidase Inhibition

Dry MeOH extracts of the twig barks of Pyrus communis subsp. pyraster, P. spinosa and their hybrid P.×jordanovii nothosubsp. velenovskyi, collected in wild in Serbia, were analyzed. By LC/MS, the contents of arbutin (99.9-131.0 mg/g), chlorogenic acid (2.2-6.3 mg/g), catechin (1.0-5.3 mg/g) and total dimeric and trimeric procyanidins (42.2-61.3 mg/g), including procyanidin B2 (8.9-17.2 mg/g), were determined. Colorimetrically, high contents of total phenolics (436.2-533.4 mg GAE/g) and tannins (339.4-425.7 mg GAE/g), as well as strong total antioxidant activities (FRAP values 4.5-5.9 mmol Fe²⁺ /g), and DPPH (SC₅₀ =6.6-7.1 μg/ml) and hydroxyl radical (SC₅₀ =447.1-727.7 μg/ml) scavenging abilities were revealed. In vitro, all extracts exhibited notable inhibition of α-amylase (IC₅₀ =310.8-617.7 μg/ml) and particularly strong inhibition of α-glucosidase (IC₅₀ =2.1-3.7 μg/ml). Molecular docking predicted that among identified compounds procyanidin B2 is the best inhibitor of these carbohydrate-digesting enzymes. Obtained results showed that the barks of investigated Pyrus hybrid and its parent taxa have similar composition and bioactivity.

First morphological-level insights into the efficiency of green tea catechins and grape seed procyanidins on a transgenic mouse model of celiac disease enteropathy

Alternative or complementary treatments to a gluten-free diet are urgently needed for Celiac Disease. By exploiting the health-promoting properties of polyphenols on a transgenic mouse model of Celiac Disease enteropathy, this study provides the first in vivo evidence regarding the ability of 1 mg day-1 doses of green tea catechins and grape seed procyanidins to ameliorate some of the most characteristic histological changes of gliadin-treated DQ8 mice, including villus flattening, crypt hyperplasia, and infiltration of intraepithelial lymphocytes. Mechanistically, polyphenols were found to increase the intestinal nucleophilic tone of DQ8 mice by orchestrating an adaptive antioxidant response characterized by enhanced GSR enzyme activity and GSH content. Taken together, this work constitutes a highly relevant breakthrough as it provides the fundamental basis concerning the significance of natural polyphenols to be used in, for instance, the development of innovative functional foods aimed at CD individuals.

Unravelling the effects of procyanidin on gliadin digestion and immunogenicity

The effect of procyanidin dimer B3, a common food tannin, on the digestion of gliadin proteins was investigated by monitoring the changes in the immunogenic peptides produced during in vitro digestion and immunoreactivity. Interaction studies between procyanidin dimer B3, gluten proteins and/or digestive enzymes were performed by SDS-PAGE. The effect of procyanidin B3 on the enzymatic activity of trypsin, chymotrypsin and pancreatin was evaluated. The differences in the number and nature of immunogenic peptides released during digestion were identified by mass spectrometry. Briefly, the enzymatic activity of gastrointestinal enzymes was only slightly affected but a significant decrease in the immunological properties of the peptides produced during digestion was observed. Overall, although further studies are needed, the interaction between polyphenols and gluten proteins clearly influences gluten protein digestion and immunogenicity, thus suggesting that the consumption of dietary polyphenols can significantly affect the degree of celiac disease downstream immune reactions.

Gliadin Sequestration as a Novel Therapy for Celiac Disease: A Prospective Application for Polyphenols

Celiac disease is an autoimmune disorder characterized by a heightened immune response to gluten proteins in the diet, leading to gastrointestinal symptoms and mucosal damage localized to the small intestine. Despite its prevalence, the only treatment currently available for celiac disease is complete avoidance of gluten proteins in the diet. Ongoing clinical trials have focused on targeting the immune response or gluten proteins through methods such as immunosuppression, enhanced protein degradation and protein sequestration. Recent studies suggest that polyphenols may elicit protective effects within the celiac disease milieu by disrupting the enzymatic hydrolysis of gluten proteins, sequestering gluten proteins from recognition by critical receptors in pathogenesis and exerting anti-inflammatory effects on the system as a whole. This review highlights mechanisms by which polyphenols can protect against celiac disease, takes a critical look at recent works and outlines future applications for this potential treatment method.

Combined in silico and in vitro studies to identify novel antidiabetic flavonoids targeting glycogen phosphorylase

Novel pharmacological strategies for the treatment of diabetic patients are now focusing on inhibiting glycogenolysis steps. In this regard, glycogen phosphorylase (GP) is a validated target for the discovery of innovative antihyperglycemic molecules. Natural products, and in particular flavonoids, have been reported as potent inhibitors of GP at the cellular level. Herein, free-energy calculations and microscale thermophoresis approaches were performed to get an in-depth assessment of the binding affinities and elucidate intermolecular interactions of several flavonoids at the inhibitor site of GP. To our knowledge, this is the first study indicating genistein, 8-prenylgenistein, apigenin, 8-prenylapigenin, 8-prenylnaringenin, galangin and valoneic acid dilactone as natural molecules with high inhibitory potency toward GP. We identified: i) the residues Phe285, Tyr613, Glu382 and/or Arg770 as the most relevant for the binding of the best flavonoids to the inhibitor site of GP, and ii) the 5-OH, 7-OH, 8-prenyl substitutions in ring A and the 4'-OH insertion in ring B to favor flavonoid binding at this site. Our results are invaluable to plan further structural modifications through organic synthesis approaches and develop more effective pharmaceuticals for Type 2 Diabetes treatment, and serve as the starting point for the exploration of food products for therapeutic usage, as well as for the development of novel bio-functional food and dietary supplements/herbal medicines.

Review of Structural Features and Binding Capacity of Polyphenols to Gluten Proteins and Peptides In Vitro: Relevance to Celiac Disease

Polyphenols have been extensively studied due to their beneficial effects on human health, particularly for the prevention and treatment of diseases related to oxidative stress. Nevertheless, they are also known to have an anti-nutritional effect in relation to protein metabolism. This effect is a consequence of its binding to digestive enzymes and/or protein substrates. Dietary gluten is the main trigger of celiac disease, a common immune-based disease of the small intestine and for which the only treatment available is the adherence to a gluten-free diet. Recent studies have addressed the use of dietary polyphenols to interact with gluten proteins and avoid its downstream deleterious effects, taking the advantage of the anti-nutritive nature of polyphenols by protein sequestering. Flavonoids, coumarins and tannins have shown the ability to form insoluble complexes with gluten proteins. One of the most promising molecules has been epigallocatechin-3-gallate, which through its binding to gliadins, was able to reduce gliadins digestibility and its ability to stimulate monolayer permeability and transepithelial transport of immunodominant peptides in cell models. This review focuses on the structural features and binding capacity of polyphenols to gluten proteins and peptides, and the prospects of developing an adjuvant therapy in celiac disease.