A study of multi-ligand beta-lactoglobulin complex formation

Metabolic mechanisms of Dihydromyricetin and strategies for enhancing its bioavailability: A recent review

Dihydromyricetin, a flavonoid primarily found in vine tea, offers a range of health-promoting benefits, making it a promising functional food ingredient for improving nutrition and preventing diseases. However, its limited solubility, unstable physicochemical properties, short half-life, and rapid metabolism contribute to poor bioavailability, which restricts its broader application in food, pharmaceutical, and related industries. To overcome these challenges, extensive research has focused on strategies to enhance the bioavailability of dihydromyricetin. This paper reviews the digestion, absorption, tissue distribution, and metabolic mechanisms of dihydromyricetin in the human body. It examines the key factors influencing its bioavailability and highlights the design and construction of various bio-based delivery systems aimed at improving its bioavailability. Furthermore, the paper explores the potential applications of these delivery systems. The development of such systems can significantly enhance the stability and bioavailability of dihydromyricetin, providing a solid theoretical foundation for advancing its use in food and medicine.

Interactions between polyphenols and polysaccharides/proteins: Mechanisms, effect factors, and physicochemical and functional properties: A review

Polyphenols have attracted much attention in the food industry and nutrition because of their unique biological activities. However, the health benefits of polyphenols are compromised due to their structural instability and sensitivity to the external environment. The interaction between polyphenols and polysaccharides/proteins largely determines the stability and functional characteristics of polyphenols in food processing and storage. Hence, this topic has attracted widespread attention in recent years. This review initially outlines the basic properties of polyphenols and their applications in food. Subsequently, the interaction mechanisms between polyphenols and polysaccharides/proteins are discussed in detail including non-covalent bonding, covalent modification, and conformational changes. These interactions can display profound impacts on the nutritional value, taste, stability, and safety of food. Additionally, this article also systematically reviews the influencing factors (type, concentration, temperature, pH, and other factors) of interaction between polyphenols and proteins/polysaccharides. Finally, this paper also summarizes systematically the effects of the interaction between polyphenols and polysaccharides/proteins on the physicochemical and functional properties of polyphenols/proteins. The findings provide prospects for the application of composite materials in food preservation, functional food development, and nanocarrier development, which can provide theoretical references for the in-depth development of polyphenols in the food industry.

Challenges and Advances in the Encapsulation of Bioactive Ingredients Using Whey Proteins

Functional foods represent an emerging trend in the food industry. Fortifying foods with bioactive ingredients results in health benefits and reduces the risk of disease. Encapsulation techniques protect sensitive ingredients from degradation due to heat, light, moisture and other factors. Among encapsulating materials, milk whey proteins are particularly attractive due to their availability, GRAS status and remarkable ligand-binding ability. Whey protein was once considered a by-product in the dairy industry but is now seen as a promising resource given its natural role as a nutrient carrier. This work reviews the encapsulation systems that employ whey proteins in the food industry. The structural features of β-lactoglobulin (β-LG), the main protein constituent of milk whey, are presented in the context of its ligand-binding properties. Different types of encapsulation systems using whey proteins are discussed, focusing on the recent advances in stable formulations of bioactives using whey protein, alone or in hybrid systems. Whey proteins are a valuable asset capable of binding sensitive bioactive compounds such as vitamins, polyphenols and antioxidants and forming stable complexes that can be formulated as nanoparticles, nanofibrils, emulsions and other micro- and nanostructures. Developing scalable, solid and stable encapsulation systems is identified as a main challenge in the field.

Complexation with Alginate in Pumpkin Leaf Protein Solutions for the Encapsulation of Folic Acid: The Effect of Extraction Protocols

This study aimed to assess pumpkin leaves as a protein source and determine the feasibility of these proteins to form complexes with alginate for the encapsulation of folic acid. Different isolation protocols, two based on isoelectric precipitation (one with thermal pretreatment and the other with alkali pre-extraction) and one based on stepwise precipitation with ammonium sulfate, were compared regarding the yield and structural properties of the obtained leaf protein concentrates (LPC). The highest purity of protein was achieved using the thermal-acid protocol and the salting-out protocol at 40% saturation. RuBisCO protein was detected by SDS-PAGE in all LPCs, except for the fractions obtained through salting-out at saturation level ≥ 60%. Complexation of the LPC solutions (1 mg/mL) and sodium alginate solution (10 mg/mL) was monitored as a function of LPC:alginate ratio (2:1, 5:1, and 10:1) and pH (2-8) by zeta-potential measurements and confirmed by FT-IR analysis. Based on the results, the strongest interaction between LPCs and alginate occurred at a pH between 2.20 and 2.80 and an LPC:alginate ratio of 10:1. Complexation resulted in particle yields of 42-71% and folic acid entrapment of 46-92%. The LPC-folic acid interactions elucidated by computational protein-ligand docking demonstrated the high potential of RuBisCO as a biocarrier material for folic acid. The in vitro release study in the simulated gastrointestinal fluids indicated that complexes would be stable in gastric conditions, while folic acid would be gradually released in the intestinal fluids.

Casein phosphopeptide interferes the interactions between ferritin and ion irons

Ferritin, a vital protein required to store iron in a cage-like structure, is critical for maintaining iron balance. Ferritin can be attacked by free radicals during iron reduction and release, thereby leading to oxidative damage. Whether other biomacromolecules such as casein phosphopeptides (CPP) could influence the ferritin's function in iron oxidation and release and affect the ferritin stability remains unclear. This study aims to investigate the effect of CPP on the ferritin‑iron ion interaction, thereby focusing on role of CPP on ferritin stability. Results showed that CPP weakened the iron oxidation activity of ferritin but promoted iron release. Moreover, CPP could effectively chelate iron, capture hydroxyl radicals, and reduce the degradation of ferritin. This study highlights the role of CPP in the ferritin‑iron relationship, and lays a foundation for understanding the interaction between ferritin, peptides, and metal ions.

Preparation and functional properties of rice bran globulin-chitooligosaccharide-quercetin-resveratrol covalent complex

BACKGROUND

As the major protein (approximately 36%) in rice bran, globulin exhibits excellent foaming and emulsifying properties, endowing its useful application as a foaming and emulsifying agent in the food industry. However, the low water solubility restricts its commercial potential in industrial applications. The present study aimed to improve this protein's processing and functional properties.

RESULTS

A novel covalent complex was fabricated by a combination of the Maillard reaction and alkaline oxidation using rice bran globulin (RBG), chitooligosaccharide (C), quercetin (Que) and resveratrol (Res). The Maillard reaction improved the solubility, emulsifying and foaming properties of RBG. The resultant glycosylated protein was covalently bonded with quercetin and resveratrol to form a (RBG-C)-Que-Res complex. (RBG-C)-Que-Res exhibited higher thermal stability and antioxidant ability than the native protein, binary globulin-chitooligosaccharide or ternary globulin-chitooligosaccharide-polyphenol (only containing quercetin or resveratrol) conjugates. (RBG-C)-Que-Res exerted better cytoprotection against the generation of malondialdehyde and reactive oxygen species in HepG2 cells, which was associated with increased activities of antioxidative enzymes superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) through upregulated genes SOD1, CAT, GPX1 (i.e. gene for glutathione peroxidase-1), GCLM (i.e. gene for glutamate cysteine ligase modifier subunit), SLC1A11 (i.e. gene for solute carrier family 7, member 11) and SRXN1 (i.e. gene for sulfiredoxin-1). The anti-apoptotic effect of (RBG-C)-Que-Res was confirmed by the downregulation of caspase-3 and p53 and the upregulation of B-cell lymphoma-2 gene expression.

CONCLUSION

The present study highlights the potential of (RBG-C)-Que-Res conjugates as functional ingredients in healthy foods. © 2024 Society of Chemical Industry.

In Silico Investigations on the Synergistic Binding Mechanism of Functional Compounds with Beta-Lactoglobulin

Piceatannol (PIC) and epigallocatechin gallate (EGCG) are polyphenolic compounds with applications in the treatment of various diseases such as cancer, but their stability is poor. β-lactoglobulin (β-LG) is a natural carrier that provides a protective effect to small molecule compounds and thus improves their stability. To elucidate the mechanism of action of EGCG, PIC, and palmitate (PLM) in binding to β-LG individually and jointly, this study applied molecular docking and molecular dynamics simulations combined with in-depth analyses including noncovalent interaction (NCI) and binding free energy to investigate the binding characteristics between β-LG and compounds of PIC, EGCG, and PLM. Simulations on the binary complexes of β-LG + PIC, β-LG + EGCG, and β-LG + PLM and ternary complexes of (β-LG + PLM) + PIC, (β-LG + PLM) + EGCG, β-LG + PIC) + EGCG, and (β-LG + EGCG) + PIC were performed for comparison and characterizing the interactions between binding compounds. The results demonstrated that the co-bound PIC and EGCG showed non-beneficial effects on each other. However, the centrally located PLM was revealed to be able to adjust the binding conformation of PIC, which led to the increase in binding affinity with β-LG, thus showing a synergistic effect on the co-bound PIC. The current study of β-LG co-encapsulated PLM and PIC provides a theoretical basis and research suggestions for improving the stability of polyphenols.

Serum albumin acted as an effective carrier to improve the stability of bioactive flavonoid

The health-improving functions of bioactive flavonoids in vitro and in vivo are often limited by their low stability, which could be counteracted by the application of proteins as carriers of flavonoids. Clarification of the mechanism of protein-ligand interaction is crucial for the encapsulation of bioactive components. Herein, common plasma proteins [i.e., bovine serum albumin (BSA), human serum albumin (HSA), human immunoglobulin G (IgG) and fibrinogen (FG)] were compared for their binding characteristics to quercetin, the main component of flavonoids in human diet, in the absence and presence of free Cu2+ (an accelerator for flavonoids' instability) using multi-spectroscopic and computational methods. As a flexible open structure of proteins, both BSA and HSA were found to be the most promising carriers for quercetin and Cu2+ with an affinity on the order of 104 M-1. HSA-diligand complex (i.e., HSA-quercetin-Cu2+) was successfully generated when both quercetin and Cu2+ were added to the HSA solution. The stability and free radical scavenging activity of bioactive quercetin during incubation was promoted in the HSA-diligand complex relative to quercetin-Cu2+ complex. Quercetin/Cu2+ system could induce the formation of reactive oxygen species such as hydrogen peroxide (H2O2) and hydroxide radical (·OH), which were significantly suppressed upon HSA binding. Consistently, the cytotoxicity of the quercetin/Cu2+ system to endothelial cells was reduced in the HSA-diligand complex. These results demonstrate the possibility of developing serum albumin-based carriers for the protection of bioactive flavonoids in their nutritional application.

Plant-Based Protein-Phenolic Interactions: Effect on different matrices and in vitro gastrointestinal digestion

This review summarizes the literature on the interaction between plant-based proteins and phenolics. The structure of the phenolic compound, the plant source of proteins, matrix properties (pH, temperature), and interaction mechanism (covalent and non-covalent) change the secondary structure, ζ-potential, surface hydrophobicity, and thermal stability of proteins as well as their functional properties including solubility, foaming, and emulsifying properties. Studies indicated that the foaming and emulsifying properties may be affected either positively or negatively according to the type and concentration of the phenolic compound. Protein digestibility, on the other hand, differs depending on (1) the phenolic concentration, (2) whether the food matrix is ​​solid or liquid, and (3) the state of the food-whether it is heat-treated or prepared as a mixture without heat treatment in the presence of phenolics. This review comprehensively covers the effects of protein-phenolic interactions on the structure and properties of proteins, including functional properties and digestibility both in model systems and real food matrix.

Characterization of polyphenols compounds extracted from stressed apple peel and their interaction with β-lactoglobulin

This paper proposes to apply a postharvest environmental stress to red apples, Malus domestica, variety Red Delicious in order to increase the polyphenols compounds (PP) content in their peels. The possibility of enhancing extractable PP provides a useful alternative for the use of discarded crops in the food industry. A great increase in PP was observed in response to light damage produced by the environmental stress applied in this work. Flavonols > anthocyanins > flavanols > dihydrochalcones > phenolic acids is the order in PP content. The interaction of the extracted PP from unstressed and stressed apple peels with beta-lactoglobulin (β-LG) was characterized. A PP/β-LG complex which was formed with one single binding site in the protein was determined. The interaction was spontaneous and enthalpy driven. PP extracted from unstressed samples had greater affinity for the protein than PP extracted from stressed samples, possibly due to the polar characteristic of anthocyanins. The results of this last study could provide a better understanding of the interaction between PP and β-LG to incorporate them into functional foods.

A comprehensive review of protein-based carriers with simple structures for the co-encapsulation of bioactive agents

The rational design and fabrication of edible codelivery carriers are important to develop functional foods fortified with a plurality of bioactive agents, which may produce synergistic effects in increasing bioactivity and functionality to target specific health benefits. Food proteins possess considerable functional attributes that make them suitable for the delivery of a single bioactive agent in a wide range of platforms. Among the different types of protein-based carriers, protein-ligand nanocomplexes, micro/nanoparticles, and oil-in-water (O/W) emulsions have increasingly attracted attention in the codelivery of multiple bioactive agents, due to the simple and convenient preparation procedure, high stability, matrix compatibility, and dosage flexibility. However, the successful codelivery of bioactive agents with diverse physicochemical properties by using these simple-structure carriers is a daunting task. In this review, some effective strategies such as combined functional properties of proteins, self-assembly, composite, layer-by-layer, and interfacial engineering are introduced to redesign the carrier structure and explore the encapsulation of multiple bioactive agents. It then highlights success stories and challenges in the co-encapsulation of multiple bioactive agents within protein-based carriers with a simple structure. The partition, protection, and release of bioactive agents in these protein-based codelivery carriers are considered and discussed. Finally, safety and application as well as challenges of co-encapsulated bioactive agents in the food industry are also discussed. This work provides a state-of-the-art overview of protein-based particles and O/W emulsions in co-encapsulating bioactive agents, which is essential for the design and development of novel functional foods containing multiple bioactive agents.

Encapsulation of Folic Acid and α-Tocopherol in Lysozyme Particles and Their Bioaccessibility in the Presence of DNA

Protein particles have been reported as the potential carriers for the co-encapsulation of bioactive components. In this study, lysozyme, a basic protein, was used to simultaneously encapsulate folic acid and α-tocopherol at pH 4.0. The encapsulation efficiency and loading capacity of folic acid or α-tocopherol increased with its respective concentration. Folic acid had no influence on the encapsulation of α-tocopherol. However, the encapsulation of folic acid was improved by α-tocopherol below 40 μg/mL but reduced by α-tocopherol at higher concentrations. The encapsulation by lysozyme shielded folic acid, α-tocopherol, or both partially from the attack of 2,2'-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS) radical cation. No masking effect of lysozyme encapsulation on α-tocopherol was found in DPPH antioxidant activity assay. Furthermore, the DNA coating was used to improve the dispersion of lysozyme with folic acid and α-tocopherol. The lysozyme/DNA particles with folic acid and α-tocopherol showed a homogenous size distribution of 180-220 nm with ζ-potential values between -33 and -36 mV. The release and bioaccessibility of folic acid in lysozyme/DNA with α-tocopherol were similar to that of folic acid alone, while the release of α-tocopherol was delayed and its bioaccessibility was improved by encapsulation in lysozyme/DNA with folic acid. The data gathered here would provide guidance for the use of lysozyme-based co-encapsulating carriers in the development of functional foods.

Study on the binding behavior and functional properties of soybean protein isolate and β-carotene

This study focused on the non-covalent interaction between soybean protein isolate (SPI) and β-carotene (BC). The conformational changes of SPI with β-carotene in varying proportions (BC/SPI: 2%, 4%, 6%, 8%, and 10%) were investigated by multi-spectroscopy and molecular docking. Results showed that the quenching mode is static quenching and binding affinity increased with temperature. The stoichiometry was 1:1, indicating there was only one binding site in SPI. The binding was based on entropy and primarily driven by hydrophobic interactions and its binding constant was in the order of 104 L⋅mol–1. The addition of the β-carotene affected the secondary structure of SPI resulting in an increase in α-Helix and a decrease in random coil and β-turn content, indicating protein aggregated and hydrophobic interactions occurred. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) verified that no new larger molecular weight substance was formed and no covalent interaction existed. Molecular docking corroborated that electrostatic and hydrophobic interactions were both involved in the formation of complexes, where hydrophobic interaction was the dominant one. Moreover, β-carotene improved 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, foaming capacity, and emulsifying stability of SPI. These findings provide useful information about the interaction mechanism of SPI and β-carotene, which contributes to the further development and application of SPI products rich in β-carotene in the food industry.

Diagnosis and Rationale for Action against Cow's Milk Allergy (DRACMA) Guidelines update - III - Cow's milk allergens and mechanisms triggering immune activation

Background

The immunopathogenesis of cow's milk protein allergy (CMPA) is based on different mechanisms related to immune recognition of protein epitopes, which are affected by industrial processing.

Purpose

The purpose of this WAO DRACMA paper is to: (i) give a comprehensive overview of milk protein allergens, (ii) to review their immunogenicity and allergenicity in the context of industrial processing, and (iii) to review the milk-related immune mechanisms triggering IgE-mediated immediate type hypersensitivity reactions, mixed reactions and non-IgE mediated hypersensitivities.

Results

The main cow’s milk allergens – α-lactalbumin, β-lactoglobulin, serum albumin, caseins, bovine serum albumins, and others – may determine allergic reactions through a range of mechanisms. All marketed milk and milk products have undergone industrial processing that involves heating, filtration, and defatting. Milk processing results in structural changes of immunomodulatory proteins, leads to a loss of lipophilic compounds in the matrix, and hence to a higher allergenicity of industrially processed milk products. Thereby, the tolerogenic capacity of raw farm milk, associated with the whey proteins α-lactalbumin and β-lactoglobulin and their lipophilic ligands, is lost.

Conclusion

The spectrum of immunopathogenic mechanisms underlying cow's milk allergy (CMA) is wide. Unprocessed, fresh cow's milk, like human breast milk, contains various tolerogenic factors that are impaired by industrial processing. Further studies focusing on the immunological consequences of milk processing are warranted to understand on a molecular basis to what extent processing procedures make single milk compounds into allergens.

Potential uses of milk proteins as encapsulation walls for bioactive compounds: A review

Milk proteins have received much awareness due to their bioactivity. However, their encapsulation functions have not attracted enough attention. Milk proteins as encapsulation walls can increase the bioavailability of bioactive compounds. As the benefits of bioactive compounds are critically determined by bioavailability, the effect of interactions between milk proteins and active substances is a critical topic. In the present review, we summarize the effects of milk proteins as encapsulation walls on the bioavailability of active substances with a special focus. The methods and mechanisms of interactions between milk proteins and active substances are also discussed. The evidence collected in the present review suggests that when active substances are encapsulated by milk proteins, the bioavailability of active substances can be significantly affected. This review also provides valuable guidelines for the use of milk protein-based microcarriers.

Study on the Interaction Mechanism Between Soybean Protein Isolates and Lemon Flavor: Isomerization and Degradation of Citral

By headspace solid-phase microextraction/gas chromatography-mass spectrometry, the effects of 1% (w/v) alcohol denatured soybean protein isolates (L-SPI), native soybean protein isolates (N-SPI), as well as the thermal denaturation of soybean protein isolates (H-SPI) on low concentration (24 μmol/L) of citral was studied in aqueous. The results shows that the SPI could catalyze citral isomerization and yield methyl heptenone and acetaldehyde by inverse aldol condensation degradation. 3-Hydroxycitronelloal was formed as an intermediate in this reaction. The catalytic efficiency of the L-SPI was higher than that of N-SPI, whereas the catalytic efficiency of H-SPI was the lowest. Additionally, it shows that the catalytic efficiency increased as the pH increased. The catalytic efficiency of 7S (Soybean β-Conglycinin) was greater than that of 11S (Soy bean Proglycinin).

Antioxidant activity, stability, in vitro digestion and cytotoxicity of two dietary polyphenols co-loaded by β-lactoglobulin

The combination of multiple dietary polyphenols may have synergistic beneficial effects. And the beneficial effects can be further improved by the encapsulation of proteins. The interactions of procyanidin B2 (PB2) and/or dihydromyricetin (DMY) with β-lactoglobulin (β-LG) were investigated using multi-spectroscopic techniques and molecular docking. The structural change of β-LG in the presence of PB2 and/or DMY was demonstrated by dynamic light scattering, Fourier transform infrared spectroscopy and circular dichroism spectroscopy. Response surface analysis was used to optimize the synergistic antioxidant activity between PB2 and DMY. Besides, the antioxidant activity, stability, in vitro digestion and cytotoxicity of PB2 and DMY in the binary and ternary systems were investigated. These studies will elucidate the interaction mechanism of PB2 and/or DMY with β-LG. The research results can provide theoretical support for the development of functional foods and beverages with synergistic activity, improved stability and bioaccessibility, thereby promoting human health and preventing diseases.

Bovine Serum Albumin as a Potential Carrier for the Protection of Bioactive Quercetin and Inhibition of Cu(II) Toxicity

Considering the protective ability of proteins and the potential toxicity of free Cu(II), it was proposed herein that the co-presence of protein could play an important role in suppressing the toxicity of free Cu(II) to the stability of bioactive quercetin if a flavonoid-protein-Cu(II) complex could be formed. In this study, the interaction between quercetin (a major flavonoid in the human diet) and bovine serum albumin (BSA) was investigated in the absence and presence of free Cu(II). The results demonstrated that both quercetin and free Cu(II) had a strong ability to quench the intrinsic fluorescence of BSA through a static procedure (i.e., formation of a BSA-monoligand complex). Site marker competitive experiments illustrated that the binding of both quercetin and Cu(II) to BSA mainly took place in subdomain IIA. The quenching process of free Cu(II) with BSA was easily affected by quercetin, and the increased binding capacity possibly resulted from the generation of a ternary quercetin-BSA-Cu(II) complex. The stability and free radical scavenging activity of bioactive quercetin during incubation was promoted in the BSA-diligand complex relative to a quercetin-Cu(II) complex. A quercetin-Cu(II) system could generate reactive oxygen species such as hydrogen peroxide (H₂O₂) and hydroxyl radicals (^•OH), which were significantly inhibited upon BSA binding. Consistently, the cytotoxicity of the quercetin-Cu(II) system to endothelial cells was decreased in the BSA-diligand complex, where the co-presence of BSA played an important role. These results suggest the possibility and advantage of developing albumin-based carriers for the protection of bioactive components and suppression of Cu(II) toxicity in their biomedical and nutritional applications.

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.

Co-encapsulation of (-)-epigallocatechin-3-gallate and piceatannol/oxyresveratrol in β-lactoglobulin: effect of ligand-protein binding on the antioxidant activity, stability, solubility and cytotoxicity

The co-encapsulation of multiple bioactive components in a carrier may produce synergistic effects and improve health benefits. In this study, the interactions of β-lactoglobulin (β-LG) with epigallocatechin-3-gallate (EGCG) and/or piceatannol (PIC)/oxyresveratrol (OXY) were investigated by multispectroscopic techniques, isothermal titration calorimetry, and molecular docking. The static quenching mechanism of β-LG by EGCG, PIC and OXY was confirmed by fluorescence spectroscopy and UV-vis absorption difference spectroscopy. The binding sites of these three polyphenols in β-LG were identified by site marking fluorescence experiments and molecular docking. The thermodynamic parameters of the β-LG + EGCG/PIC/OXY binary complex and β-LG + EGCG + PIC/OXY ternary complex were obtained from fluorescence data and used to analyze the main driving force for complex formation. The exothermic binding process was further confirmed by isothermal titration calorimetry. The α-helical content, particle size and morphology of free and ligand-bound β-LG were determined by circular dichroism spectroscopy, dynamic light scattering and transmission electron microscopy, respectively. The effect of EGCG, PIC and OXY on the conformation of β-LG was studied by Fourier transform infrared spectroscopy. In addition, the maximum synergistic antioxidant activity between EGCG and PIC/OXY was obtained by response surface analysis. The effects of β-LG in the binary and ternary systems on the antioxidant activity, stability, solubility and cytotoxicity of the polyphenols were also studied. Finally, the different cytotoxicities of the complexes and nanoparticles of the binary and ternary systems were compared. The results of this study are expected to provide a theoretical basis for the development of β-LG-based carriers co-encapsulating a variety of bioactive components.

Internal cavity amplification of shell-like ferritin regulated with the change of the secondary and tertiary structure induced by PEF technology

In this study, the effect of pulsed electric field (PEF) on apparent morphology and molecular structure of shell-like ferritin obtained from horse spleen was determined by circular dichroic (CD), fluorescence spectroscopy, Raman spectroscopy, cold field emission scanning electron microscopy (CF-SEM) and transmission electron microscopy (TEM), and verified by molecule dynamics (MD) simulation. After PEF treatment, the α-helix content of the samples reached a minimum value at 10 kV/cm, which indicated that the ferritin structure has been partially unfolded. However, the α-helix content peaked again after resting for 2 h at 25 ± 1 °C. This indicated that the PEF-treated ferritin tended to restore its original spherical morphology probably owing to the reversible assembly characteristic of ferritin. In addition, microstructure analysis revealed that ferritin particles aggregated after PEF treatment. Therefore, PEF treatment could induce the "exposure" of hydrophobic amino acids and conversion of disulfide bond configuration, and consequently, regulate the internal cavity stability of ferritin. The research will be beneficial to expand the application of PEF treatment in the modification of protein structure, and provide a theoretical basis for the application of ferritin as a carrier of bioactive molecules in food.

Generation of a Bovine Serum Albumin-Diligand Complex for the Protection of Bioactive Quercetin and Suppression of Heme Toxicity

As an abundant protein in milk and blood serum, bovine serum albumin (BSA) contains various sites to bind a lot of bioactive components, generating BSA-monoligand complex. Demonstration of the interaction between BSA and bioactive components (such as heme, flavonoids) is important to develop effective carrier for the protection of bioactive ligands and to reduce cytotoxicity of heme. Herein, the bindings of BSA to quercetin and/or heme were investigated by multispectroscopic and molecular docking methods. The fluorescence of protein was significantly quenched by both quercetin and heme in a static mode (i.e., generation of BSA-ligand complex). Although quercetin had lower affinity to protein than heme, the interactions of both compounds with protein did locate in site I (i.e., subdomain IIA). BSA-diligand complex was successfully generated after the coaddition of quercetin and heme. The cytotoxicity of free heme to endothelial cells was reduced in the BSA-diligand complex relative to that of heme or BSA-monoligand complex, while the stability of bioactive quercetin was promoted in the complex relative to free flavonoid. The complex provided a better inhibition on the cytotoxicity of heme than BSA-monoligand complex, in which the copresence of quercetin played a vital role.

Characterization, spectroscopic and crystallographic analyses of β-lactoglobulin and docosahexaenoic acid nanocomplexes

In this work, we investigated the interaction of docosahexaenoic acid (DHA) with β-lactoglobulin (β-Lg) using spectroscopic and crystallographic methods. The fluorescence results showed that DHA formed complexes with β-Lg with a binding constant of 4.13 × 10⁴ M^-1. The secondary structure of β-Lg was not significantly (p > 0.05) changed after binding with DHA. Dynamic light scattering showed the particle size of β-Lg-DHA complexes was about 5 nm, the same as that of β-Lg alone. The turbidity of DHA in aqueous solution decreased after binding with β-Lg. The crystallographic results showed that DHA was bound at one site in the calyx of β-Lg and that the aliphatic chain was hidden inside the hydrophobic β-barrel while the carboxyl group was located at the calyx entrance. These findings indicate that β-Lg can act as an effective nanocarrier for DHA.

Oral Delivery of β-Lactoglobulin-Nanosphere-Encapsulated Resveratrol Alleviates Inflammation in Winnie Mice with Spontaneous Ulcerative Colitis

Resveratrol (RES) is a nutraceutical with promising anti-inflammatory properties for the treatment of inflammatory bowel diseases (IBD). However, the clinical effectiveness of resveratrol as an oral anti-inflammatory agent is hindered by its extremely poor solubility and poor stability. In this study, we encapsulated resveratrol in β-lactoglobulin (BLG) nanospheres and systematically analyzed their formulation parameters in vitro followed by a thorough in vivo anti-inflammatory testing in a highly specialized spontaneous murine UC model (Winnie mice model). Complexation of resveratrol with BLG increased the aqueous solubility of resveratrol by ≈1.7 times with 10% w/w loading. Additionally, the in vitro dissolution of resveratrol from the particles was found to be higher compared to resveratrol alone, resulting in >90% resveratrol dissolution in ∼8 h. The anti-inflammatory activity of resveratrol was examined for the first time in Winnie mice, a mouse model that closely represents the clinical signs of IBD. At a 50 mg/kg oral dose for 2 weeks, BLG-RES significantly improved both % body weight and disease activity index (DAI), compared to free resveratrol in Winnie mice. Importantly, histological evaluations revealed a similar trend with striking improvement in the pathology of the colon via an increase in goblet cell numbers and recovery of colonic epithelium. BLG-RES significantly increased the expression level of cytokine interleukin-10 (Il10), which confirms the reduction in inflammation potentially because of the increased dissolution and stability of resveratrol by complexation with BLG. This comprehensive study demonstrates the effectiveness of biocompatible nanomaterials such as BLG in oral delivery of poorly soluble anti-inflammatory molecules such as resveratrol in the treatment of IBD.

Coencapsulation and Stability Evaluation of Hydrophilic and Hydrophobic Bioactive Compounds in a Cagelike Phytoferritin

Enrichment of multiple bioactive components with different characters into one food substrate simultaneously is a challenge. In this study, the hydrophilic epigallocatechin gallate (EGCG) and the hydrophobic quercetin were simultaneously enriched in the cavity of phytoferritin from red bean seed deprived of iron (apoRBF), a cagelike protein. The interactions of apoRBF with EGCG and quercetin were evaluated by UV/visible absorption, fluorescence, and circular dichroism technologies. By combination of the reversible assembly and urea induced approaches, both EGCG and quercetin were successfully coencapsulated in apoRBF to fabricate four kinds of apoRBF-EGCG-quercetin nanocomplexes FEQ (FEQ1, FEQ2, FEQ3, and FEQ4) with good solubility in aqueous solution. All FEQ samples maintained the typically spherical morphology of ferritin cage with a diameter around 12 nm. Among the four FEQ samples, the FEQ1 prepared by involving a pH 2.0/6.7 transition scheme was more effective in encapsulating EGCG and quercetin molecules than that by the urea induced method. Furthermore, all FEQs facilitated the stability of EGCG and quercetin molecules relative to free ones, and simultaneous coencapsulation of EGCG and quercetin could significantly improve the quercetin stability as compared with that of the free one and quercetin-loaded ferritin (p < 0.05), respectively. This work provides a new scheme to design and fabricate the ferritin based carrier for encapsulation of multiple bioactive components, and it is beneficial for the intensification of multifunction in one food substrate.

Mechanism for Inhibition of Folic Acid Photodecomposition by Various Antioxidants

Folic acid, a synthetic form of folate, is a water-soluble vitamin that is essential during periods of rapid cell division and growth. However, it decomposes upon ultraviolet irradiation to form inactive photoproducts. In this study, the protective effect and mechanisms of antioxidants, including cinnamic acids, flavonoids, catechol and its derivatives, stilbenes, p-benzoquinone and its derivatives, isoprenoids, curcumin, oleic acid, and linoleic acid, against folic acid photodecomposition were investigated by using fluorescence and absorbance spectroscopy, high-performance liquid chromatography, and antioxidant assay. It was found that antioxidants could inhibit or delay the folic acid decomposition in varying degrees, among which caffeic acid was the most effective. The increase in its remarkable antioxidant efficiency and absorbance in the UVA region during irradiation contributed to its effective protection. This finding could be useful for the protection of photolabile components in food and other uses.

Properties of β-Lactoglobulin Aggregates and Gels as Affected by Ternary Emulsifier Mixtures of Tween 20, Lecithin, and Sucrose Palmitate

The influence of sucrose palmitate, Tween 20, and lecithin on the properties of heat-induced aggregates and cold-set gels of β-lactoglobulin was studied based on an experimental mixture design with a fixed total emulsifier concentration. Emulsifiers were added to the protein solution before heating. Aggregate size and absolute values of ζ potential increased with the addition of emulsifiers, among which lecithin had the most pronounced effect. The water retention of the aggregates correlated positively with the aggregate size. Gels had reduced fracture stress and strains with increasing sucrose palmitate and decreasing Tween 20 contents. The fracture properties correlated with the ζ potentials of the aggregates, and larger aggregates led to gels with higher water-holding capacities. The emulsifiers hence influenced the gel properties indirectly via the aggregate properties. The impact of emulsifiers on food structures should therefore be considered when a food product is designed.

β-Lactoglobulin as a potential carrier for bioactive molecules

In this study, the interaction and binding behavior of anesthetic tetracaine (TET) with bovine β-lactoglobulin (LGB) isoform A and a mixture of isoforms A and B were investigated under varying environmental conditions (pH, ionic strength, concentration, LGB-TET complex molar ratio). A wide range of analytical techniques (dynamic light scattering (DLS), electrophoretic mobility, UV-Vis spectroscopy, circular dichroism (CD), quartz crystal microbalance (QCM-D) were used to analyze the physicochemical properties of the complexes in bulk solution and on the surface of gold. The experiments revealed that TET, which is amphiphilic, could bind with LGB not only in the β-barrel but also onto the surface. The zeta potential of the LGB becomes more positively charged upon interaction with TET due to electrostatic interaction of the amino group present in the TET structure. Changes in the zeta potential values are mostly visible above pH 6 for all tested systems. CD spectra show that interaction with the ligand does not change the secondary structure of the protein. The physicochemical properties of LGB-TET complex were examined in an adsorbed state on a gold surface using the QCM-D method. Additionally, molecular docking was used to evaluate the most likely binding site for TET with LGB.

Characterization of Bovine Serum Albumin and (-)-Epigallocatechin Gallate/3,4- O-Dicaffeoylquinic Acid/Tannic Acid Layer by Layer Assembled Microcapsule for Protecting Immunoglobulin G in Stomach Digestion and Release in Small Intestinal Tract

The protein-polyphenol layer by layer (LbL) assembled polymer composite microcapsule is a considerable delivery system that can be used to improve the bioactive stability and effectiveness of natural compounds in various applications. In the present study, three kinds of polyphenols were loaded in the sequence of (-)-epigallocatechin gallate (EGCG), 3,4- O-dicaffeoylquinic acid (3,4-diCQA), and tannin acid (TA) to prepare a BSA-polyphenol LbL membrane. The composition of IgG-(BSA-EGCG/3,4-diCQA/TA) _n microcapsules and their stability and releasing ability in the gastrointestinal tract were evaluated. In addition, by binding of these three kinds of polyphenols to BSA, the thermal denaturation temperature and ordered secondary structure of the BSA-polyphenol microcapsules were increased, and the time of scavenging activity on 2,2'-azinobis(3-ethylbenzothiazolin-6-sulfonic acid) free radicals was significantly prolonged. These findings suggest that (BSA-EGCG/3,4-diCQA/TA) _n microcapsules can not only protect IgG in food processing and stomach digestion but also release it in the small intestinal tract for bioactive delivery.

Generation of a Diligand Complex of Bovine Serum Albumin with Quercetin and Carbon Nanotubes for the Protection of Bioactive Quercetin and Reduction of Cytotoxicity

The interactions between proteins and bioactive ligands (such as flavonoids and nanomaterials) are vital to the design of effective protein carriers for the protection of bioactive molecules and reduction of the cytotoxicity of nanotubes. Bovine serum albumin (BSA) can bind various bioactive components and subsequently form protein-ligand complexes. Herein, the binding of BSA to quercetin and single-walled carbon nanotubes (SWCNTs) was investigated by using experimental and molecular-docking methods. The fluorescence intensity of BSA was decreased by both quercetin and SWCNTs in static quenching mode (i.e., compound formation), which was authenticated by Stern-Volmer calculations. Although quercetin showed a higher affinity for BSA than SWCNTs, the binding of both components to BSA was located in site I (subdomain IIA). BSA-diligand complexes were successfully generated when SWCNTs and quercetin, in that sequence, were added. The cytotoxicity of SWCNTs and the formation of reactive oxygen species in endothelial cells were decreased with the BSA-diligand complexes relative to those of SWCNTs or BSA-SWCNT corona, whereas the stability problems of quercetin were ameliorated in the BSA-diligand complex relative to in the free flavonoid. The BSA-diligand complex showed a better inhibitive effect on the cytotoxicity of SWCNTs than the BSA-SWCNT complex, and thus the coexistence of quercetin played a crucial role. These data demonstrate the advantages and possibility of designing BSA carriers for the protection of bioactive ligands and reduction of the cytotoxicity of nanotubes in functional-food and biomedical applications.