Comparative studies of interaction of β-lactoglobulin with three polyphenols

The lipase inhibitory effect of mulberry leaf phenolic glycosides: The structure-activity relationship and mechanism of action

The present study found for the first time that phenolic glycosides were an important material basis for mulberry leaves to inhibit lipase. The corresponding IC50 for hyperoside, rutin, astragalin and quercetin were 68, 252, 385 and 815 μg/mL respectively. The inhibitory effect was ranked as monoglycosides > phenolic hydroxyl groups > disaccharides on the benzone ring. Hyperoside bound to lipase in competitive inhibition type with one binding site, while the others bound to lipase in a mixed inhibition type by two similar sites. All four compounds altered the microenvironment and secondary conformation of lipase through static quenching. The docking score, stability, and binding energy were consistent with the compound inhibitory activity. The main binding between compounds and lipase amino acid residues were spontaneously though hydrophobic interactions and hydrogen bonding. The strong hydrogen bonds formed with SER-152 inside the lipase pocket, might be important for the strong inhibitory activity of hyperoside.

Effects of ultrasound pretreatment on the structure, IgE binding capacity, functional properties and bioactivity of whey protein hydrolysates via multispectroscopy and peptidomics revealed

Whey protein is an important food ingredient, but it is also considered a major food allergen. The aim of this study was to investigate the effect of ultrasound pretreatment on the structure, IgE binding capacity, functional properties and biological activity of whey protein isolate (WPI) hydrolysates (WPH), including WPI hydrolyzed by a combination of enzymes from Bromelain and ProteAXH (BA-WPI) and WPI hydrolyzed by a combination of enzymes from Papain W-40 and ProteAXH (PA-WPI). The IgE binding capacity of BA-WPI and PA-WPI was reduced to 40.28% and 30.17%, respectively, due to disruption/exposure/shielding of conformational and linear epitopes. The IgE binding capacity of sonicated WPI was increased, but ultrasound pretreatment further reduced the IgE binding capacity of the hydrolysates to 32.89% and 28.04%. This is due to the fact that ultrasound pretreatment leads to conformational changes including increased α-helix and β-sheet structure, exposure of aromatic amino acids, surface hydrophobicity, and increased sulfhydryl content, which increases the accessibility of allergenic epitopes to WPI by the enzyme. Multispectral and LC-MS/MS results further indicated that ultrasound pretreatment altered the conformational and primary structural changes of the hydrolysates. The thermograms showed that ultrasound pretreatment mainly altered the epitope spectra of β-lactoglobulin hydrolysates, while it had less effect on the epitope spectra of α-lactalbumin hydrolysates. Additionally, ultrasound pretreatment significantly improved the foaming properties, antioxidant activity, and α-glucosidase inhibition of the hydrolysates without impairing the solubility and emulsification properties of the hydrolysates. Therefore, ultrasound pretreatment is a feasible method to reduce the allergenicity of WPH and to improve their functional properties and bioactivity. Notably, ultrasonic pretreatment improved the effectiveness and efficiency of WPI hydrolysis, which is a feasible method to produce high-quality protein feedstock in a green, efficient, and economical way.

Integrated spectroscopic and computational analyses unravel the molecular interaction of pesticide azinphos-methyl with bovine beta-lactoglobulin

Organophosphorus are typically hazardous chemicals used in the pharmaceutical, agricultural, and other industries. They pose a serious risk to human life and can be fatal upon direct exposure. Hence, studying the interaction between such compounds with proteins is crucial for environmental, health, and food safety. In this study, we investigated the interaction mechanism between azinphos-methyl (AZM) and β-lactoglobulin (BLG) at pH 7.4 using a combination of biophysical techniques. Intrinsic fluorescence investigations revealed that BLG fluorescence was quenched in the presence of increasing AZM concentrations. The quenching mechanism was identified as static, as evidenced by a decrease in the fluorescence quenching constant (1.25 × 104, 1.18 × 104, and 0.86 × 104 M-1) with an increase in temperatures. Thermodynamic calculations (ΔH > 0; ΔS > 0) affirmed the formation of a complex between AZM and BLG through hydrophobic interactions. The BLG's secondary structure was found to be increased due to AZM interaction. Ultraviolet -visible spectroscopy data showed alterations in BLG conformation in the presence of AZM. Molecular docking highlighted the significant role of hydrophobic interactions involving residues such as Val43, Ile56, Ile71, Val92, Phe105, and Met107 in the binding between BLG and AZM. A docking energy of -6.9 kcal mol-1, and binding affinity of 1.15 × 105 M-1 suggest spontaneous interaction between AZM and BLG with moderate to high affinity. These findings underscore the potential health risks associated with the entry of AZM into the food chain, emphasizing the need for further consideration of its impact on human health.

Biomacromolecular carriers based hydrophobic natural products for potential cancer therapy

Cancer is the second leading cause of death worldwide. It was estimated that 90 % of cancer-related deaths were attributable to the development of multi-drug resistance (MDR) during chemotherapy, which results in ineffective chemotherapy. Hydrophobic natural products plays a pivotal role in the field of cancer therapy, with the potential to reverse MDR in tumor cells, thereby enhancing the efficacy of tumor therapy. However, their targeted delivery is considered a major hurdle in their application. The advent of numerous approaches for encapsulating bioactive ingredients in the nanodelivery systems has improved the stability and targeted delivery of these biomolecules. The manuscript comprehensively analyses the nanodelivery systems of bioactive compounds with potential cancer therapy applications, including liposomes, emulsions, solid lipid nanoparticles (NPs), and polymeric NPs. Then, the advantages and disadvantages of various nanoagents in the treatment of various cancer types are critically discussed. Further, the application of multiple-compbine delivery methods to overcome the limitations of single-delivery have need critically analyzed, which thus could help in the designing nanodrug delivery systems for bioactive compounds in clinical settings. Therefore, the review is timely and important for development of efficient nanodelivery systems involving hydrophobic natural products to improve pharmacokinetic properties for effective cancer treatment.

Effects of preheat treatment and syringic acid modification on the structure, functional properties, and stability of black soybean protein isolate

This study investigated preheated (25-100°C) black soybean protein isolate (BSPI) conjugated with syringic acid (SA) (25 and 50 µmol/g protein) under alkaline conditions, focusing on the structure, functional properties, and storage stability. The results revealed that the SA binding equivalent and binding rate on BSPI increased continuously as the preheat temperature increased. Additionally, preheating positively impacted the surface hydrophobicity (H0) of BSPI, with further enhancement observed upon SA binding. Preheating and SA binding altered the secondary and tertiary structure of BSPI, resulting in protein unfolding and increased molecular flexibility. The improvement in BSPI functional properties was closely associated with both preheating temperature and SA binding. Specifically, preheating decreased the solubility of BSPI but enhanced the emulsifying activity index (EAI) and foaming capacity (FC) of BSPI. Conversely, SA binding increased the solubility of BSPI with an accompanying increase in EAI, FC, foaming stability, and antioxidant activity. Notably, the BSPI100-SA50 exhibited the most significant improvement in functional properties, particularly in solubility, emulsifying, and foaming attributes. Moreover, the BSPI-SA conjugates demonstrated good stability of SA during storage, which positively correlated with the preheating temperature. This study proposes a novel BSPI-SA conjugate with enhanced essential functional properties, underscoring the potential of preheated BSPI-SA conjugates to improve SA storage stability. PRACTICAL APPLICATION: Preheated BSPI-SA conjugates can be used as functional ingredients in food or health products. In addition, preheated BSPI shows potential as a candidate for encapsulating and delivering hydrophobic bioactive compounds.

Characterization of ultrasound-assisted covalent binding interaction between β-lactoglobulin and dicaffeoylquinic acid: Great potential for the curcumin delivery

The low bioavailability and poor gastrointestinal instability of curcumin hampers its application in pharmaceutical and food industries. Thus, it is essential to explore efficient carrier (e.g. a combination of polyphenols and proteins) for food systems. In this study, covalent β-lactoglobulin (LG)-dicaffeoylquinic acids (DCQAs) complexes were prepared by combining ultrasound and free radical induction methods. Covalent interactions between LG and DCQAs were confirmed by analyzing reactive groups. Variations in secondary or tertiary structure and potential binding sites of covalent complexes were explored using Fourier transform infrared spectroscopy and circular dichroism. Results showed that the β-sheet content decreased and the unordered content increased significantly (P < 0.05). The embedding rate of curcumin in prepared LG-DCQAs complexes using ultrasound could reach 49 % - 62 %, proving that complexes could embed curcumin effectively. This study highlights the benefit of ultrasound application in fabrication of protein-polyphenol complexes for delivering curcumin.

Effects of Chlorogenic Acid on Lowering IgE-Binding Capacity of Soybean 7S: Comparison between Covalent and Noncovalent Interaction

Allergenicity of soybean 7S protein (7S) troubles many people around the world. However, many processing methods for lowering allergenicity is invalid. Interaction of 7S with phenolic acids, such as chlorogenic acid (CHA), to structurally modify 7S may lower the allergenicity. Hence, the effects of covalent (C-I, periodate oxidation method) and noncovalent interactions (NC-I) of 7S with CHA in different concentrations (0.3, 0.5, and 1.0 mM) on lowering 7S allergenicity were investigated in this study. The results demonstrated that C-I led to higher binding efficiency (C-0.3:28.51 ± 2.13%) than NC-I (N-0.3:22.66 ± 1.75%). The C-I decreased the α-helix content (C-1:21.06%), while the NC-I increased the random coil content (N-1:24.39%). The covalent 7S-CHA complexes of different concentrations had lower IgE binding capacity (C-0.3:37.38 ± 0.61; C-0.5:34.89 ± 0.80; C-1:35.69 ± 0.61%) compared with that of natural 7S (100%), while the noncovalent 7S-CHA complexes showed concentration-dependent inhibition of IgE binding capacity (N-0.3:57.89 ± 1.23; N-0.5:46.91 ± 1.57; N-1:40.79 ± 0.22%). Both interactions produced binding to known linear epitopes. This study provides the theoretical basis for the CHA application in soybean products to lower soybean allergenicity.

Dietary Polyphenols, Plant Metabolites, and Allergic Disorders: A Comprehensive Review

Given the ongoing rise in the occurrence of allergic disorders, alterations in dietary patterns have been proposed as a possible factor contributing to the emergence and progression of these conditions. Currently, there is a significant focus on the development of dietary therapies that utilize natural compounds possessing anti-allergy properties. Dietary polyphenols and plant metabolites have been intensively researched due to their well-documented anti-inflammatory, antioxidant, and immunomodulatory characteristics, making them one of the most prominent natural bioactive chemicals. This study seeks to discuss the in-depth mechanisms by which these molecules may exert anti-allergic effects, namely through their capacity to diminish the allergenicity of proteins, modulate immune responses, and modify the composition of the gut microbiota. However, further investigation is required to fully understand these effects. This paper examines the existing evidence from experimental and clinical studies that supports the idea that different polyphenols, such as catechins, resveratrol, curcumin, quercetin, and others, can reduce allergic inflammation, relieve symptoms of food allergy, asthma, atopic dermatitis, and allergic rhinitis, and prevent the progression of the allergic immune response. In summary, dietary polyphenols and plant metabolites possess significant anti-allergic properties and can be utilized for developing both preventative and therapeutic strategies for targeting allergic conditions. The paper also discusses the constraints in investigating and broad usage of polyphenols, as well as potential avenues for future research.

Interactions between phosvitin and aldehydes affect the release of flavor from Russian sturgeon caviar

The release mechanism of flavor during caviar storage was studied by the interaction between phosvitin and four aldehydes. Gas chromatography-mass spectrometry showed that the binding rate of phosvitin with 3-methylbutanal, nonanal, (E,Z)-2,6-nonadienal, and (E)-2-octenal decreased with an increase in the aldehyde concentrations. Among them, (E,Z)-2,6-Nonadienal (0.5 mM) had the highest binding rate (84.47%). The main quenching mechanism of (E,Z)-2,6-nonadienal with phosvitin was static quenching and the binding force comprised spontaneous hydrophobic interactions. An increase in the aldehyde concentrations reduced the α-helix content of phosvitin and led to aggregation of the microstructure of phosvitin. The results of molecular docking showed that tyr residue contributed the most to the binding of phosvitin to aldehydes. This study has elucidated the mechanism of the effect of caviar protein on changes in the caviar flavor during storage and provides effective strategies for regulation of caviar flavor during storage.

Study of four polyphenol-Coregonus peled (C. peled) myofibrillar protein interactions on protein structure and gel properties

The effects of four polyphenols-chlorogenic acid (CA), gallic acid (GA), epicatechin gallate (ECG), and epigallocatechin gallate (EGCG) on the structure, gel properties, and interaction mechanisms of myofibrillar protein (MP) were studied. The changes in MP structure with polyphenols were analyzed using circular dichroism. The ultraviolet and fluorescence spectra and thermodynamic analysis indicated that the type of binding between the four polyphenols with the MP was static quenching of complex formation. GA had a more pronounced effect on improving MP gel properties. Finally, molecular docking determined that the affinity of the protein with the four polyphenols was in the order EGCG > ECG > CA > GA, with the main interaction force being hydrophobic interactions and hydrogen bonding, but hydrogen bonding dominates the interaction between GA and the protein. The findings illuminate the mechanism of MP binding to different polyphenols and facilitate the study of polyphenol-protein properties.

Covalent polyphenols-proteins interactions in food processing: formation mechanisms, quantification methods, bioactive effects, and applications

Proteins and polyphenols are abundant in the daily diet of humans and their interactions influence, among other things, the texture, flavor, and bioaccessibility of food. There are two types of interactions between them: non-covalent interactions and covalent interactions, the latter being irreversible and more powerful. In this review, we systematically summarized advances in the investigation of possible mechanism underlying covalent polyphenols-proteins interaction in food processing, effect of different processing methods on covalent interaction, methods for characterizing covalent complexes, and impacts of covalent interactions on protein structure, function and nutritional value, as well as potential bioavailability of polyphenols. In terms of health promotion of the prepared covalent complexes, health effects such as antioxidant, hypoglycemic, regulation of intestinal microbiota and regulation of allergic reactions have been summarized. Also, the possible applications in food industry, especially as foaming agents, emulsifiers and nanomaterials have also been discussed. In order to offer directions for novel research on their interactions in food systems, nutritional value, and health properties in vivo, we considered the present challenges and future perspectives of the topic.

Reducing the allergenicity of tropomyosin in shrimp by covalent conjugation with quercetin and chlorogenic acid

The study aimed to assay the allergenicity of shrimp tropomyosin (TM) following covalent conjugation with quercetin (QR) and chlorogenic acid (CA). The structure of the TM-polyphenol covalent conjugates was examined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), circular dichroism (CD), fluorescence, differential scanning calorimetry (DSC), and Fourier Transform infrared spectroscopy (FTIR). Potential allergenicity was evaluated using in vitro and in vivo methods. The results showed that QR and CA induced structural changes in TM through aggregation. RBL-2H3 cell results showed that TM-QR and TM-CA covalent conjugates reduced the release of β-hexosaminidase and histamine, respectively. In the mice model, TM-QR and TM-CA covalent conjugates reduced the level of IgE, IgG, IgG1, histamine, and mMCP-1 in sera. Furthermore, the allergenicity was reduced by suppressing Th2-related cytokines (IL-4, IL-5, IL-13) and promoting Th1-related cytokines (IFN-γ). These research findings demonstrate that the covalent binding of TM with QR and CA, modifies the allergenic epitopes of shrimp TM, thereby reducing its potential allergenicity. This approach holds practical applications in the production of low-allergenicity food within the food industry.

Reactivity and mechanism of the reactions of 4-methylbenzoquinone with amino acid residues in β-lactoglobulin: A kinetic and product investigation

Quinones, produced by the oxidation of phenolic compounds, covalently bind to nucleophilic groups on amino acids or proteins. In this study, the reactions of 4-methylbenzoquinone (4MBQ) with β-lactoglobulin (β-LG) and amino acids at neutral pH were investigated. LC-MS analysis revealed that Cys121 was likely the most modified residue in β-LG. Identification of reaction products by LC-MS/MS showed that Michael addition occurred in all reactions with amino acids tested. The formation of Schiff base and a di-adduct was found in His and Trp samples. Apparent second-order rate constants (k2) were determined at 25 °C and pH 7.0 by stopped-flow spectrophotometry. The rate of reactions decreased in the order: β-LG > His > Trp > Arg > Nα-acetyl His > Nα-acetyl Arg > Nα-acetyl Trp. The rate constants correlated with the pKa values of the amino acids, showing that the amount of unprotonated amine is the major factor determining the reactivity.

Effects of conjugated interactions between Perilla seed meal proteins and different polyphenols on the structural and functional properties of proteins

The study aims to perform alkali-induced covalent modification of perilla seed meal protein (PSMP) using different polyphenols: gallic acid (GA), protocatechuic acid (PCA), caffeic acid (CA), apigenin (API) and luteolin (LU). Covalent binding between different polyphenols and PSMP was found to occur, with PSMP-LU showing the highest binding rate of 90.89 ± 1.37 mg/g; the fluorescence spectrum of PSMP-CA showed a maximum blue shift of Δ13.4 nm; the solubility increased from 69.626 ± 1.39 % to 83.102 ± 0.98 %. In order to better understand how these covalent conjugates, stabilize -carotene in emulsions, they were utilized as emulsifiers in an emulsion delivery method. The work further reveals the formation of PSMP-polyphenol conjugates and develops a novel emulsification system to deliver readily decomposable functional factors, providing a potential scenario for the application of PSMP and bioactive conjugates.

Dietary Polyphenols-Natural Bioactive Compounds with Potential for Preventing and Treating Some Allergic Conditions

In light of the constantly increasing prevalence of allergic diseases, changes in dietary patterns have been suggested as a plausible environmental explanation for the development and progression of these diseases. Nowadays, much attention has been paid to the development of dietary interventions using natural substances with anti-allergy activities. In this respect, dietary polyphenols have been studied extensively as one of the most prominent natural bioactive compounds with well-documented anti-inflammatory, antioxidant, and immunomodulatory properties. This review aims to discuss the mechanisms underlying the potential anti-allergic actions of polyphenols related to their ability to reduce protein allergenicity, regulate immune response, and gut microbiome modification; however, these issues need to be elucidated in detail. This paper reviews the current evidence from experimental and clinical studies confirming that various polyphenols such as quercetin, curcumin, resveratrol, catechins, and many others could attenuate allergic inflammation, alleviate the symptoms of food allergy, asthma, and allergic rhinitis, and prevent the development of allergic immune response. Conclusively, dietary polyphenols are endowed with great anti-allergic potential and therefore could be used either for preventive approaches or therapeutic interventions in relation to allergic diseases. Limitations in studying and widespread use of polyphenols as well as future research directions are also discussed.

Glutamine and lysine as common residues from epitopes on α-lactalbumin and β-lactoglobulin from cow milk identified by phage display technology

Cow milk is an important source of food protein for children; however, it could lead to allergy, especially for infants. α-Lactalbumin (α-LA) and β-lactoglobulin (β-LG) from whey protein make up a relatively high proportion of milk proteins and have received widespread attention as major allergens in milk. However, few studies have identified the epitopes of both proteins simultaneously. In this study, ImmunoCAP and indirect ELISA were first used for detection of sIgE to screen sera from allergic patients with high binding capacity for α-LA and β-LG. Subsequently, the mimotopes was biopanned by phage display technology and bioinformatics and 17 mimic peptide sequences were obtained. Aligned with the sequences of α-LA or β-LG, we identified one linear epitope on α-LA at AA 11-26 and 5 linear epitopes on β-LG at AA 9-29, AA 45-57, AA 77-80, AA 98-101, and AA 121-135, respectively. Meanwhile, the 8 conformational epitopes and their distributions of α-LA and β-LG were located using the Pepitope Server. Finally, glutamine and lysine were determined as common AA residues for the conformational epitopes both on α-LA and β-LG. Moreover, we found the addition of mouse anti-human IgE during the biopanning process did not significantly affect the identification of the epitopes.

Liver transcriptomic and proteomic analyses provide new insight into the pathogenesis of liver fibrosis in mice

BACKGROUND

Liver fibrosis (LF) is a kind of progressive liver injury reaction. The goal of this study was to achieve a more detailed understanding of the molecular changes in response to CCl4-induced LF through the identification of a differentially expressed liver transcriptomic and proteomic.

RESULTS

A total of 1224 differentially expressed genes (DEGs) and 302 differentially expressed proteins (DEPs) were significantly identified at the transcriptomic and proteomic level, respectively, and 69 genes (hereafter "cor-DEGs-DEPs" genes) were detected at both levels. Pathway enrichment analysis showed that these cor-DEGs-DEPs genes were significantly enriched in 133 pathways. Importantly, among the cor-DEGs-DEPs genes, Gstm1, Gstm3, Ephx1 and Gstp1 were shown to be associated with metabolic pathways, and confirmed by RT-qPCR and parallel reaction monitoring (PRM) verification.

CONCLUSIONS

Through the combined analysis of transcriptomic and proteomic data, this study provides valuable insights into the potential mechanism of the pathogenesis of LF, and lays a theoretical foundation for the further development of targeted therapy for LF.

The structural and functional properties of soybean protein-polyglutamic acid complex effected the stability of W/O/W emulsion encapsulated Nattokinase

Nattokinase (NK) derived from food is a sustainable thrombolytic agent. In this study, to protect vulnerable biological activity of NK, the targeted modified W/O/W emulsions were fabricated from complexes of soybean isolate protein (SPI) and polyglutamic acid (PGA). The results showed that the SPI-PGA complex formed a tighter internal structure through non-covalent bonds. The secondary structure, α-helix and β-sheet content of the 1:3 (v/v) ratio complex of SPI to PGA increased by 6.14% and 8.62%, respectively. The emulsification and stability of the complexes were improved by refining structural properties as against SPI. The W/O/W emulsions coated by complexes formed the stronger network structure with higher encapsulation efficiency, better interfacial features, and better storage stability. Moreover, the highest bioavailability was achieved by W/O/W emulsions coated with 1:3 ratio complex at 80.69%. This study provided a new strategy towards tailoring ideal emulsion vehicles and expanded the NK application in food formulations.

Modification of the Structural and Functional Characteristics of Mung Bean Globin Polyphenol Complexes: Exploration under Heat Treatment Conditions

During the storage and processing of mung beans, proteins and polyphenols are highly susceptible to interactions with each other. Using globulin extracted from mung beans as the raw material, the study combined it with ferulic acid (FA; phenolic acid) and vitexin (flavonoid). Physical and chemical indicators were combined with spectroscopy and kinetic methods, relying on SPSS and peak fit data to statistically analyze the conformational and antioxidant activity changes of mung bean globulin and two polyphenol complexes before and after heat treatment and clarify the differences and the interaction mechanism between globulin and the two polyphenols. The results showed that, with the increase in polyphenol concentration, the antioxidant activity of the two compounds increased significantly. In addition, the antioxidant activity of the mung bean globulin-FA complex was stronger. However, after heat treatment, the antioxidant activity of the two compounds decreased significantly. The interaction mechanism of the mung bean globulin-FA/vitexin complex was static quenching, and heat treatment accelerated the occurrence of the quenching phenomenon. Mung bean globulin and two polyphenols were combined through a hydrophobic interaction. However, after heat treatment, the binding mode with vitexin changed to an electrostatic interaction. The infrared characteristic absorption peaks of the two compounds shifted to different degrees, and new peaks appeared in the areas of 827 cm^-1, 1332 cm^-1, and 812 cm^-1. Following the interaction between mung bean globulin and FA/vitexin, the particle size decreased, the absolute value of zeta potential increased, and the surface hydrophobicity decreased. After heat treatment, the particle size and zeta potential of the two composites decreased significantly, and the surface hydrophobicity and stability increased significantly. The antioxidation and thermal stability of the mung bean globulin-FA were better than those of the mung bean globulin-vitexin complex. This study aimed to provide a theoretical reference for the protein-polyphenol interaction mechanism and a theoretical basis for the research and development of mung bean functional foods.

Calorimetric, volumetric and structural studies of the interaction between chlorogenic acid and dipalmitoylphosphatidylcholine bilayers

Chlorogenic acid (CGA) is the main component of coffee and an antioxidant. CGA has been reported to bear various good health effects. At the same time, it has been found that the addition of CGA induces an undesirable deformation of red blood cells. This fact suggests that CGA may bind to the proteins or/and membrane lipids of red blood cells. This study aimed to examine how CGA binds the bilayers of phosphatidylcholine (PC), one of red blood cells' primary lipids. To this end, we investigated the effect of CGA on the phase behavior and the structure of dipalmitoyl-PC (DPPC) bilayers in the form of multi-lamellar vesicles. Calorimetry and dilatometry measurements showed that the DPPC chain melting transition cooperativity decreases as increasing CGA concentrations. In addition, X-ray diffraction results showed that the lamellar repeat periodicity becomes disordered, and the periodicity disappears completely at high CGA concentrations. Together with these findings, it can be inferred that the CGA molecules do not penetrate inside the DPPC bilayers but bind to their surface in a negatively charged form.

Effects of hydroxylation at C3' on the B ring and diglycosylation at C3 on the C ring on flavonols inhibition of α-glucosidase activity

The structure-activity relationship and inhibitory mechanism of flavonols on α-glucosidase were studied by inhibition kinetics, multispectral study, and molecular docking. The flavonols of rutin, quercetin and kaempferol effectively inhibit the activity of α-glucosidase, among which quercetin and rutin showed the strongest and weakest inhibitory abilities, respectively. The inhibitory ability of flavonols was enhanced by hydroxylation at C3' of B ring, while it was weakened by diglycosylation at C3 of C ring. Remarkably, the quenching affinity and inhibitory ability of flavonols were inconsistent, which was different from the conclusions reported by some previous studies. This may be ascribed to the hydroxyl groups of C3' of B ring and C3 of C ring. Furthermore, three flavonols were spontaneously bound to α-glucosidase through hydrophobic interactions and hydrogen bonding, which caused the structure and hydrophobic microenvironment of α-glucosidase to change, resulting in significant inhibition of α-glucosidase by flavonols.

Effect of ferulic acid covalent conjugation on the functional properties and antigenicity of β-lactoglobulin

Binding to phenolics can improve the functional properties of proteins. Changes in structure, functional properties, and antigenicity of β-lactoglobulin (β-LG) after covalent conjugation with ferulic acid (FA) at different mass ratios were reported here. The results of SDS-PAGE and gel exclusion chromatography confirmed that covalent complexes were formed. When the mass ratio of β-LG and FA was 10:6, the binding content of FA was the highest. Fluorescence spectroscopy, UV-visible absorption spectrometry, and FTIR analysis showed that the structure of the complexes was more stretched compared to native β-LG. The addition of FA significantly improved the emulsifying property of β-LG. When the mass ratio was 10:6, the radical scavenging activities of DPPH and ABTS reached 65.06% and 88.22%, respectively, and the antigenicity of β-LG reduced by about 35%. This study provides novel β-LG-FA complexes in food systems to reduce the antigenicity of β-LG and improve functional properties.

Interactions of soy protein isolate with common and waxy corn starches and their effects on acid-induced cold gelation properties of complexes

Soy protein isolate (SPI) was mixed with different concentrations of common starch (CS) and waxy starch (WS) from corn. The interactions of SPI with CS or WS and their effects on the acid-induced cold gelation properties of complexes were investigated. Compared with WS, SPI could bind to CS more strongly and formed a tighter SPI-CS non-covalent complex, which resulted in the increased β-sheet and a more ordered secondary structure. The gel strength, water holding capacity (WHC), viscoelasticity, hydrophobic interactions and thermal stability of SPI-CS complex gels were enhanced as increasing CS concentration, and the complex with 2% of CS had the best gelation properties. Although adding WS reduced the gel strength, rheological properties and hydrophobic interactions of SPI-WS complex gels, it improved the WHC and thermal stability of the complex gels. Therefore, CS had a broader effect on improving acid-induced cold gelation properties of SPI than WS.

Hemp seed protein and chlorogenic acid complex: Effect of ultrasound modification on its structure and functional properties

In this study, the effects of ultrasound and chlorogenic acid (CA) on the structural and functional properties of hemp seed protein (HSP) was investigated. Compared with natural HSP, the UV-vis spectra intensity of ultrasound-treated HSP (UHSP) and UHSP-CA increased, the fluorescence spectra intensity decreased with a red shift in the maximum intensity peak. The results showed that ultrasound modification and complexation with CA unfolded the structure of HSP exposing its internal groups. Fluorescence quenching analysis showed that the best binding between UHSP and CA (binding constant 2.94 × 10² L/mol) was achieved at 450 W for 15 min of ultrasound treatment. In addition, the same ultrasound conditions minimized the particle size and surface roughness of UHSP and UHSP-CA. The solubility of UHSP and UHSP-CA increased by 23.3 and 38.7 %, the emulsifying activity index increased by 16.9 and 16.2 %, and the emulsion stability index increased by 20.9 and 20.8 %, respectively. These results indicated that appropriate ultrasound treatment and complexation with CA can significantly modify the structural and functional properties of HSP, improving its application value in the food field.

Interaction between Chinese quince fruit proanthocyanidins and bovine serum albumin: Antioxidant activity, thermal stability and heterocyclic amine inhibition

Heterocyclic amines (HCAs) are carcinogenic and mutagenic substances produced in fried meat. Adding natural antioxidants (e.g., proanthocyanidins (PAs)) is a common method to reduce HCAs; however, the interaction between the PAs and protein can affect the inhibitory efficacy of PAs on the formation of HCAs. In this study, two PAs (F1 and F2) with different degrees of polymerization (DP) were extracted from Chinese quince fruits. These were combined with bovine serum albumin (BSA). The thermal stability, antioxidant capacity and HCAs inhibition of all four (F1, F2, F1-BSA, F2-BSA) were compared. The results showed that F1 and F2 interact with BSA to form complexes. Circular dichroism spectra indicate that complexes had fewer α-helices and more β-sheets, β-turns and random coils than BSA. Molecular docking studies indicated that hydrogen bonds and hydrophobic interactions are the forces holding the complexes together. The thermal stabilities of F1 and, particularly, F2 were stronger than those of F1-BSA and F2-BSA. Interestingly, F1-BSA and F2-BSA showed increased antioxidant activity with increasing temperature. F1-BSA's and F2-BSA's HCAs inhibition was stronger than F1 and F2, reaching 72.06 % and 76.3 %, respectively, for norharman. This suggests that PAs can be used as natural antioxidants for reducing the HCAs in fried foods.

Construction of benzyl isothiocyanate-loaded fish skin gelatin-luteolin compound emulsion delivery system, and its digestion and absorption characteristics

BACKGROUND

Fish skin gelatin (FSG) and luteolin (LUT) were used as composite emulsifiers, and benzyl isothiocyanate (BITC) was used as a model of nutrient delivery to construct a stable emulsion. The storage stability of the FSG-LUT emulsion and its effect on BITC release were investigated both in vitro and ex vivo.

RESULTS

LUT can quench FSG fluorophores statically and form a stable complex through hydrogen bonding and hydrophobic interactions. The FSG-LUT emulsion storage stability and embedding rate were higher than those of the FSG emulsion. The FSG-LUT emulsion microstructure was resistant to oral and gastric digestion, and the BITC retention rate and bioaccessibility were much higher than those of the FSG emulsion. Lastly, the ex vivo everted gut sac of rat intestine study demonstrated that BITC showed the highest absorption in the ileum, and the FSG-LUT emulsion absorbed BITC and sustained a controlled release in a specific position.

CONCLUSION

LUT could form stable complexes with FSG, which improved the stability and bioavailability of BITC in the FSG-LUT emulsion delivery system, and promoted further intestinal BITC absorption. © 2022 Society of Chemical Industry.

Microencapsulation of tomato seed oil using phlorotannins-adducted pea protein isolate-chitosan and pea protein isolate-chitosan complex coacervates

Pea protein isolates (PPI)/phlorotannins (PT)/chitosan (CS) ternary complex and PPI/CS binary complex were synthesized to prepare tomato seed oil (TSO) microcapsules. The concentration of PT was determined to be 0.025% (w/w) based on the solubility, emulsification, and UV-visible spectrum of PPI-PT complex. Subsequently, the optimal pHs associated with the formation of PPI/CS and PPI-PT/CS complex coacervates were determined to be pH 6.6 and 6.1, while the optimal ratios were 9:1 and 6:1, respectively. The coacervate microcapsules were successfully produced by freeze-dried method and those formulated with PPI-PT/CS displayed significantly lower surface oil content (14.57 ± 0.22%), higher encapsulation efficiency (70.54 ± 0.13%), lower particle size (5.97 ± 0.16 μm), and PDI (0.25 ± 0.02) than PPI/CS. The microcapsules were characterized by scanning electron microscopy and Fourier Transform infrared spectroscopy. Furthermore, the encapsulated TSO exhibited enhanced thermal and oxidative stability than that of free oil, along with microcapsules fabricated with PPI-PT/CS ternary complex showed better protection than that of free PT. Overall, PPI-PT/CS complex as an effective wall material in delivery system presented great potential.

Mechanistic understanding of the effect of zein–chlorogenic acid interaction on the properties of electrospun nanofiber films

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The quenching of zein by chlorogenic acid is mainly static quenching.

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Hydrogen bonding and electrostatic interaction are main driving forces.

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The tensile strength of zein film with 2.0% chlorogenic acid increased by 132.44%.

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The addition of chlorogenic acid to zein films has potential as an active packaging.

The interaction mechanism between zein and chlorogenic acid (CA) and the effect of interaction on the performance of coaxial nanofiber films were investigated. The interactions between zein and CA were characterized by multiple spectroscopic methods. Ultraviolet spectrum analysis revealed the formation of a zein–CA complex. Fluorescence analysis pointed out that the quenching of zein by CA was static. FTIR and thermodynamic analyses showed that hydrogen bonds and electrostatic interactions dominated the interaction between zein and CA. Zein-based nanofiber films were successfully prepared by coaxial electrospinning. The interaction between zein and CA enhanced the mechanical properties but reduced the thermal stability of nanofiber films. The presence of CA endowed nanofiber films with antioxidant and antibacterial properties. This research provides significant insight into the effect of protein–polyphenol interactions on the properties of electrospun nanofiber films, which can be applied in the field of active packaging to improve food safety.

Effect of wheat bran dietary fiber on structural properties and hydrolysis behavior of gluten after synergistic fermentation of Lactobacillus plantarum and Saccharomyces cerevisiae

The effect of synergistic fermentation of Lactobacillus plantarum and Saccharomyces cerevisiae on the structural properties and aggregation behavior of gluten containing different wheat bran dietary fiber (WBDF) levels (0, 3, 6, 9, and 12%) was investigated. The results showed that WBDF addition affected the aggregation behavior of gluten at the molecular level, while WBDF significantly induced depolymerization behaviors in large aggregated gluten proteins (Molecular weight > 130 kDa) under reducing conditions (p < 0.05). In terms of secondary structure, WBDF significantly reduced glutamine side chain levels and reduced antiparallel β-sheet structures from 28.57 to 24.53% (p < 0.05). In addition, WBDF thermal properties and its water holding capacity were the main factors causing changes in thermal properties in the overall gluten system. This study provides new data for the improved production of sourdough whole grain and/or high fiber flour products.

Effects of ultrasonic pretreatment of soybean protein isolate on the binding efficiency, structural changes, and bioavailability of a protein-luteolin nanodelivery system

The combination of protein and flavonoids can ameliorate the problems of poor solubility and stability of flavonoids in utilization. In this study, soybean protein isolate pretreated by ultrasonication was selected as the embedding wall material, which was combined with luteolin to form a soybean protein isolate-luteolin nanodelivery system. The complexation effect and structural changes of soybean protein isolate (SPI) and ultrasonic pretreatment (100 W, 200 W, 300 W, 400 W and 500 W) of soybean protein isolate with luteolin (LUT) were compared, as well as the changes in digestion characteristics and antioxidant activity in vitro. The results showed that proper ultrasonic pretreatment increased the encapsulation efficacy, loading amount and solubility to 89.72%, 2.51 μg/mg and 90.56%. Appropriate ultrasonic pretreatment could make the particle size and the absolute value of ζ-potential of SPI-LUT nanodelivery system decrease and increase respectively. The FTIR and fluorescence results show that appropriate ultrasonic pretreatment could reduce α-helix, β-sheet and random coil, increase β-turn, and enhance fluorescence quenching. The thermodynamic evaluation results indicate that the ΔG < 0, ΔH > 0 and ΔS > 0, so the interaction of LUT with the protein was spontaneous and mostly governed by hydrophobic interactions. The XRD results show that the LUT was amorphous and completely wrapped by SPI. The DSC results showed that ultrasonic pretreatment could improve the thermal stability of SPI-LUT nanodelivery system to 112.66 ± 1.69 °C. Digestion and antioxidant analysis showed that appropriate ultrasonic pretreatment increased the LUT release rate and DPPH clearance rate of SPI-LUT nanodelivery system to 89.40 % and 55.63 % respectively. This study is a preliminary source for the construction of an SPI nanodelivery system with ultrasound pretreatment and the deep processing and utilization of fat-soluble active substances.

Study on the mechanism of non-covalent interaction between rose anthocyanin extracts and whey protein isolate under different pH conditions

The non-covalent interaction between anthocyanin and dietary protein had an impact on their physicochemical property. The purpose of this study was to study the non-covalent interaction mechanism between rose anthocyanin extract (RAEs) and whey protein isolate (WPI), and further compare the interaction mechanism with pure anthocyanin (PC) and WPI. At pH 3.0 and pH 7.0, RAEs and WPI had non-covalent interactions in the two systems with two types of unequal and mutually influencing binding sites, and the interaction forces were both hydrogen bonds and van der Waals forces. Interestingly, PC and WPI also had non-covalent interactions in both systems, the number of which binding sites was about one type, and the forces were hydrogen bonds and van der Waals forces. In addition, a variety of spectral combination techniques indicated that RAEs and PC caused similar changes in the secondary structure of WPI.

Impact of non-covalent bound polyphenols on conformational, functional properties and in vitro digestibility of pea protein

This study investigated the effects of the non-covalent interaction of pea protein isolate (PPI) with epigallocatechin-3-gallate (EGCG), chlorogenic acid (CA) and resveratrol (RES) on the structural and functional properties of proteins. The conformational changes of the protein structure with EGCG, CA and RES were analyzed using fourier transform infrared spectroscopy. Polyphenols strongly quenched the intrinsic fluorescence of PPI mainly through static quenching. The main interaction force was hydrogen bonding and van der Waals forces for PPI-EGCG, the main interaction force of PPI-CA complex was electrostatic interaction, while RES and PPI were bound by hydrophobic interaction. Free sulfhydryl groups and surface hydrophobicity significantly decreased in PPI after binding with phenolic compounds. The presence of EGCG, CA and RES enhanced the emulsification, foaming and in vitro digestibility of PPI. These results illustrate the potential applications of PPI-polyphenol complexes in food formulations.

Advances in dietary proteins binding with co-existed anthocyanins in foods: Driving forces, structure-affinity relationship, and functional and nutritional properties

Anthocyanins, which are the labile flavonoid pigments widely distributed in many fruits, vegetables, cereal grains, and flowers, are receiving intensive interest for their potential health benefits. Proteins are important food components from abundant sources and present high binding affinity for small dietary compounds, e.g., anthocyanins. Protein-anthocyanin interactions might occur during food processing, ingestion, digestion, and bioutilization, leading to significant changes in the structure and properties of proteins and anthocyanins. Current knowledge of protein-anthocyanin interactions and their contributions to functions and bioactivities of anthocyanin-containing foods were reviewed. Binding characterization of dietary protein-anthocyanins complexes is outlined. Advances in understanding the structure-affinity relationship of dietary protein-anthocyanin interaction are critically discussed. The associated properties of protein-anthocyanin complexes are considered in an evaluation of functional and nutritional values.

The non-covalent interactions between whey protein and various food functional ingredients

In daily diet, Whey protein (WP) is often coexisted with various Food functional ingredients (FFI) such as proteins, polyphenols, polysaccharides and vitamins, which inevitably affect or interact with each other. Generally speaking, they may be interact by two different mechanisms: non-covalent and covalent interactions, of which the former is more common. We reviewed the non-covalent interactions between WP and various FFI, explained the effect of each WP-FFI interaction, and provided possible applications of WP-FFI complex in the food industry. The biological activity, physical and chemical stability of FFI, and the structure and functionalities of WP were enhanced through the non-covalent interactions. The development of non-covalent interactions between WP and FFI provides opportunities for the design of new ingredients and biopolymer complex, which can be applied in different fields. Future research will further focus on the influence of external or environmental factors in the food system and processing methods on interactions.

A review on polyphenols and their potential application to reduce food allergenicity

This review summarized recent studies about the effects of polyphenols on the allergenicity of allergenic proteins, involving epigallocatechin gallate (EGCG), caffeic acid, chlorogenic acid, proanthocyanidins, quercetin, ferulic acid and rosmarinic acid, etc. Besides, the mechanism of polyphenols for reducing allergenicity was discussed and concluded. It was found that polyphenols could noncovalently (mainly hydrophobic interactions and hydrogen bonding) and covalently (mainly alkaline, free-radical grafting, and enzymatic method) react with allergens to induce the structural changes, resulting in the masking or/and destruction of epitopes and the reduction of allergenicity. Oral administration in murine models showed that the allergic reaction might be suppressed by regulating immune cell function, changing the levels of cytokines, suppressing of MAPK, NF-κb and allergens-presentation pathway and improving intestine function, etc. The outcome of reduced allergenicity and suppressed allergic reaction was affected by many factors such as polyphenol types, polyphenol concentration, allergen types, pH, oral timing and dosage. Moreover, the physicochemical and functional properties of allergenic proteins were improved after treatment with polyphenols. Therefore, polyphenols have the potential to produce hypoallergenic food. Further studies should focus on active concentrations and bioavailability of polyphenols, confirming optimal intake and hypoallergenic of polyphenols based on clinical trials.

A UCMPs@MIL-100 based thermo-sensitive molecularly imprinted fluorescence sensor for effective detection of β-lactoglobulin allergen in milk products

In this study, a thermo-sensitive molecularly imprinted fluorescence sensor was developed for the specific detection of β-Lactoglobulin (β-LG) allergen in milk products. The metal–organic frameworks (MIL-100) with a high specific surface area was coated on the surface of upconversion micro-particles (UCMPs). As the core, an imprinted polymer layer allowing for swelling and shrinking with response to temperature was prepared, which exhibited high adsorption and mass transfer capabilities for β-LG allergen. The fluorescence intensity of UCMPs@MIL-100@MIP decreased linearly with the concentration of β-LG in the range of 0.1–0.8 mg mL⁻¹, and the limit of detection was 0.043 mg mL⁻¹. The imprinting factor reached 3.415, which indicated that excellent specificity of the UCMPs@MIL-100@MIP for β-LG allergen. In the analysis of β-LG allergen in actual milk samples, the proposed UCMPs@MIL-100@MIP fluorescence sensor produced reliable and accurate results (recovery: 86.0–98.4%, RSD: 2.8–6.8%), closely related to the results of standard HPLC method (correlation coefficient: 0.9949), indicating that its feasibility in the detection of β-LG allergen.

Effects of Baicalein and Chrysin on the Structure and Functional Properties of β-Lactoglobulin

Two flavonoids with similar structures, baicalein (Bai) and chrysin (Chr), were selected to investigate the interactions with β-lactoglobulin (BLG) and the influences on the structure and functional properties of BLG by multispectral methods combined with molecular docking and dynamic (MD) simulation techniques. The results of fluorescence quenching suggested that both Bai and Chr interacted with BLG to form complexes with the binding constant of the magnitude of 10⁵ L·mol⁻¹. The binding affinity between BLG and Bai was stronger than that of Chr due to more hydrogen bond formation in Bai–BLG binding. The existence of Bai or Chr induced a looser conformation of BLG, but Chr had a greater effect on the secondary structure of BLG. The surface hydrophobicity and free sulfhydryl group content of BLG lessened due to the presence of the two flavonoids. Molecular docking was performed at the binding site of Bai or Chr located in the surface of BLG, and hydrophobic interaction and hydrogen bond actuated the formation of the Bai/Chr–BLG complex. Molecular dynamics simulation verified that the combination of Chr and BLG decreased the stability of BLG, while Bai had little effect on it. Moreover, the foaming properties of BLG got better in the presence of the two flavonoids compounds and Bai improved its emulsification stability of the protein, but Chr had the opposite effect. This work provides a new idea for the development of novel dietary supplements using functional proteins as flavonoid delivery vectors.

Non-covalent interaction between pea protein isolate and catechin: effects on protein structure and functional properties

The aim of this study was to investigate the effects of non-covalent interaction between pea protein isolate (PPI) and different concentrations (0.05–0.25%, w/v) of catechin (CT) on the structural and functional characteristics of protein.