Effect of non-covalent binding of phenolic derivatives with scallop (Patinopecten yessoensis) gonad protein isolates on protein structure and in vitro digestion characteristics

Insighting the effect of ultrasound-assisted polyphenol non-covalent binding on the functional properties of myofibrillar proteins from golden threadfin (Nemipterus virgatus)

In this study, the effect of ultrasound-assisted non-covalent binding of different polyphenols (tannins, quercetin, and resveratrol) on the structure and functional properties of myofibrillar proteins (MP) from the golden threadfin (Nemipterus virgatus) was investigated. The effect of ultrasound-assisted polyphenol incorporation on the structure and properties of MP was evaluated by multispectral analysis, interfacial properties, emulsification properties and antioxidant properties et al. The results revealed that the protein-polyphenol interaction led to a conformational change in the microenvironment around the hydrophobic amino acid residues, resulting in an increase in the equilibrium of the MP molecules in terms of affinity and hydrophobicity. Ultrasound assisted polyphenols addition also led to a significant decrease of the oil/water interfacial tension (from 21.22 mN/m of MP to 8.66 mN/m of UMP-TA sample) and a significant increase of the EAI (from 21.57 m2/g of MP to 28.79 m2/g of UMP-TA sample) and ES (from 84.76 min of MP to 124.25 min of UMP-TA). In addition, ultrasound-assisted polyphenol incorporation could enhance the antioxidant properties of MP, with the DPPH and ABTS radical scavenging rate of UMP-TA increase of 47.7 % and 55.2 % in comparison with MP, respectively. The results demonstrated that the noncovalent combination with polyphenols under ultrasound-assisted conditions endowed MP with better functional properties, including solubility, emulsification, foaming, and antioxidant properties through structure change. This study can provide innovative theoretical guidance for effectively preparing aquatic protein-polyphenol non-covalent complexes with multiple functions and improving the processing and utilization value of aquatic proteins.

Formation mechanism of quinoa protein hydrolysate-EGCG complexes at different pH conditions and its effect on the protein hydrolysate-lipid co-oxidation in emulsions

This study aimed to investigate the interaction, structure, antioxidant, and emulsification properties of quinoa protein hydrolysate (QPH) complexes formed with (-)-epigallocatechin gallate (EGCG) at pH 3.0 and 7.0. Additionally, the effect of pH conditions and EGCG complexation on protein hydrolysate-lipid co-oxidation in QPH emulsions was explored. The results indicated that QPH primarily interacted with EGCG through hydrophobic interactions and hydrogen bonds. This interaction led to alterations in the secondary structure of QPH, as well as a decrease in surface hydrophobicity and free SH content. Notably, the binding affinity between QPH and EGCG was observed to be higher at pH 7.0 compared to pH 3.0. Consequently, QPH-EGCG complexes exhibited more significant enhancement in antioxidant and emulsification properties at pH 7.0 than pH 3.0. The pH level also influenced the droplet size, ζ-potential, and interfacial composition of emulsions formed by QPH and QPH-EGCG complexes. Compared to QPH stabilized emulsions, QPH-EGCG stabilized emulsions were more capable of mitigating destabilization during storage and displayed fewer lipid oxidation products, carbonyl generation, and sulfhydryl groups and fluorescence loss, which implied better oxidative stability of the emulsions. Furthermore, the QPH-EGCG complexes formed at pH 7.0 exhibited better inhibition of protein hydrolysate-lipid co-oxidation. Overall, these findings provide valuable insights into the potential application of QPH and its complexes with EGCG in food processing systems.

Multi-spectroscopic and molecular docking studies for the pH-dependent interaction of β-lactoglobulin with (-)-epicatechin gallate and/or piceatannol: Influence on antioxidant activity and stability

(-)-Epicatechin gallate (ECG) and piceatannol (PIC) are commonly polyphenols with excellent biological activities. β-Lactoglobulin (BLG) is a food-grade globule protein and its morphologies are sensitive to pH. This study used experimental and computational methods to determine the interaction of single or combined ECG and PIC with BLG at different pHs. The static quenching process was determined through fluorescence and ultraviolet-visible spectroscopy. Compared with ECG, PIC could significantly bind to BLG with higher affinity. Their binding affinity for BLG with different morphologies followed the tendency of monomer > dimer > tetramer. The negative contribution of van der Waals forces, electrostatic interactions, and hydrogen bonds to ΔHo exceeded the positive contribution of hydrophobic interactions in the spontaneous and exothermic process. The reduced binding affinity in the ternary systems demonstrated the competitive binding between ECG and PIC on BLG, and the hinder effect of ECG or PIC was enhanced with increasing pH. Molecular docking studies revealed the same binding sites of ECG and PIC on various conformations of BLG and identical driven forces as thermodynamic results. Tryptophan and tyrosine were the main participators in the BLG + ECG and BLG + PIC systems, respectively. The conformational changes in the binary and ternary systems could be ascertained through synchronous fluorescence, circular dichroism, and dynamic light scattering. Furthermore, the effects of pH and BLG encapsulation on the antioxidant capacity and stability of ECG or PIC were also implemented. ECG or PIC was the most stable in the (BLG + PIC) + ECG system at pH 6.0. This study could clarify the interaction mechanism between ECG/PIC and BLG and elucidate the pH effect on their binding information. The results will provide basic support for their usage in food processing and applications.

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.

Shedding light on the interaction of ovalbumin and resveratrol: structure, digestibility, transport, and allergenicity assessment of OVA-RES complexes

BACKGROUND

The interaction between food allergens and plant polyphenols has become a safe and effective management strategy to prevent food allergies. Ovalbumin (OVA) is the most abundant allergen in egg whites. Resveratrol (RES) is a plant polyphenol that is abundant in red grapes, berries, and peanuts, and has an anti-allergic effect on allergy-related immune cells. However, there is little information about the effect of RES on the allergenicity of OVA. In this study, the effect of RES on the allergenicity of OVA was investigated.

RESULTS

Molecular docking and spectroscopic studies indicated that the addition of RES changed the structure of OVA. The digestion and transfer rate of OVA-RES were effectively improved with an in vitro gastrointestinal digestion model and Caco-2 cell model, especially when the molar ratio of OVA-RES was 1:20. Meanwhile, the KU812 cell degranulation assay proved that the potential allergenicity was remarkably decreased while the molar ratios of OVA-RES were increased to 1:20. Furthermore, hydrogen bonds and van der Waals forces were the dominating forces to stabilize the OVA-RES complexes.

CONCLUSION

All the findings demonstrated that the potential allergenicity of OVA was reduced when interacting with RES, and RES can be a potential food material for preparing a hypoallergenic protein, especially for egg allergy. © 2023 Society of Chemical Industry.

Non-covalent interaction between hemp seed globulin and two hemp seed phenolic compounds: Mechanism and effects on protein structure, bioactivity, and in vitro simulated digestion

This study focused on elucidating the non-covalent interactions between hemp seed globulin (GLB) and two hemp seed phenolic compounds, Cannabisin A (CA) and Cannabisin B (CB), and to explore these interactions on the protein's structure, conformation, and functionality. Fluorescence quenching and thermodynamic analysis revealed that static quenching governed non-covalent interaction processes, with hydrogen bonds and van der Waals forces functioning as major forces. This was further substantiated by molecular docking studies. The binding affinity order was CA > CB, indicating that the specific phenolic compound had a notable impact on the binding affinity. Furthermore, when complexed with CA, Tyr and Trp residues were exposed to a more hydrophilic environment than when complexed with CB. It was noted that the complexation with either CA or CB consistently affects GLB's secondary structure, particle size, and ζ-potential. GLB treated with the phenolic compounds exhibited enhanced ABTS and DPPH scavenging activities and improved digestibility compared to untreated GLB. Furthermore, the non-covalent interactions significantly increased CA's water solubility, highlighting GLB as a promising natural carrier for hydrophobic bioactive components. These findings hold potential implications for enhancing hemp seed protein applications within the food industry by positively influencing its functional properties and bioactivity.

The improved bioavailability of zein/soybean protein isolate by puerarin in vitro

As the largest emitter of greenhouse gases, the livestock and poultry industry is facing the challenge of increasing production to meet global demand while reducing environmental impacts. Improving feed digestibility by optimizing feed structure (e.g., exogenous additive) is one of the green breeding measures to alleviate carbon pressure. In this study, the interaction mechanism and in vitro digestibility properties of puerarin (PUE) with feed proteins (zein and soy protein isolate (SPI)) to form Zein-PUE and SPI-PUE complexes were investigated mainly by multispectral and molecular docking techniques. Results indicated that the addition of PUE improved the physicochemical properties of proteins (e.g., solubility and disulfide bond contents). Then, the spectral results showed that the binding processes were spontaneous, and the protein structure tended to loose and disordered after binding, and more hydrophobic residues were exposed to the hydrophilic microenvironment. Moreover, on the basis of molecular docking revealed that PUE bound to zein by hydrogen bond, electrostatic and hydrophobic interactions, while with SPI by hydrogen bond and hydrophobic interaction. Finally, in vitro digestion experiments demonstrated that the bioavailability of Zein-PUE and SPI-PUE complexes increased by 1.15 % and 2.11 %, respectively. Overall, PUE is a promising feed additive beneficial for enhancing protein digestibility and bioavailability.

Influence of rose anthocyanin extracts on physicochemical properties and in vitro digestibility of whey protein isolate sol/gel: Based on different pHs and protein concentrations

Protein-polyphenol interactions can improve the physicochemical properties of proteins. The objective of this study was to investigate the influence of rose anthocyanin extracts (RAEs) on the physicochemical properties and digestibility of whey protein isolate (WPI) sol/gel at different pHs and protein concentrations. Hydrophobicity interaction and ionic bonding were the main forces for the formation of acidic WPI and WPI-RAEs sol/gel. When pH was higher than 2.4, sol/gel became unstable, which may be related to hydrophobicity, ζ-potential value, total sulfhydryl and free sulfhydryl content changes. In addition, RAEs had positive effects on the color and water distribution of all WPI sol/gel. Moreover, RAEs improved the viscoelasticity of WPI sol/gel with protein content ≥ 12 % (w/v) at pH 2.4. More importantly, the addition of RAEs could reduce the digestibility of WPI sol/gel. We hope our works can provide promising strategies for developing WPI-RAEs foods.

Investigation of the interaction behavior between quercetin and pepsin by spectroscopy and MD simulation methods

The ability of a therapeutic compound to bind to proteins is critical for characterizing its therapeutic impacts. We have selected quercetin (Qu), a most common flavonoid found in plants and vegetables among therapeutic molecules that are known to have anti-inflammatory, antioxidant, anti-genotoxic, and anti-cancer effects. The current study aimed to see how quercetin interacts with pepsin in an aqueous environment under physiological conditions. Absorbance and emission spectroscopy, circular dichroism (CD), and kinetic methods, as well as molecular dynamic (MD) simulation and docking, were applied to study the effects of Qu on the structure, dynamics, and kinetics of pepsin. Stern-Volmer (K_sv) constants were computed for the pepsin-quercetin complex at three temperatures, showing that Qu reduces enzyme emission spectra using a static quenching. With Qu binding, the V_max and the k_cat/K_m values decreased. UV-vis absorption spectra, fluorescence emission spectroscopy, and CD result indicated that Qu binding to pepsin leads to microenvironmental changes around the enzyme, which can alter the enzyme's secondary structure. Therefore, quercetin caused alterations in the function and structure of pepsin. Thermodynamic parameters, MD binding, and docking simulation analysis showed that non-covalent reactions, including the hydrophobic forces, played a key role in the interaction of Qu with pepsin. The findings conclude of spectroscopic experiments were supported by molecular dynamics simulations and molecular docking results.

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

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

Graphical Abstract

Metabolomics insights into the potential of encapsulated essential oils as multifunctional food additives

Growing consumer concern about foodborne disease outbreaks and health risks associated with chemical additives has propelled the usage of essential oils (EOs) as novel food additives, but are limited by instability. In this regard, a series of EOs nano/micro-capsules have been widely used to enhance their stability and improve food quality. However, classical food quality assessment methods are insufficient to fully characterize the effects of encapsulated EOs on food properties, including physical, biochemical, organoleptic, and microbial changes. Recently, the rapid development of high-throughput sequencing is accelerating the application of metabolomics in food safety and quality analysis. This review seeks to present the most recent achievements in the application of non-targeted metabolomics to identify and quantify the overall metabolite profile associated with food quality, which can guide the development of emerging food preservation technologies. The scientific findings confirm that metabolomics opens up exciting prospects for biomarker screening in food preservation and contributes to an in-depth understanding of the mechanisms of action (MoA) of EOs. Future research should focus on constructing food quality assessment criteria based on multi-omics technologies, which will drive the standardization and commercialization of EOs for food industry applications.

Current Research on the Extraction, Functional Properties, Interaction with Polyphenols, and Application Evaluation in Delivery Systems of Aquatic-Based Proteins

Globally, aquatic processing industries pay great attention to the production of aquatic proteins for the fulfillment of the nutritive requirements of human beings. Aquatic protein can replace terrestrial animal protein due to its high protein content, complete amino acids, unique flavor, high quality and nutritional value, and requirements of religious preferences. Due to the superior functional properties, an aquatic protein based delivery system has been proposed as a novel candidate for improving the absorption and bioavailability of bioactive substances, which might have potential applications in the food industry. This review outlines the extraction techniques for and functional properties of aquatic proteins, summarizes the potential modification technologies for interaction with polyphenols, and focuses on the application of aquatic-derived protein in delivery systems as well as their interaction with the gastrointestinal tract (GIT). The extraction techniques for aquatic proteins include water, salt, alkali/acid, enzyme, organic solvent, and ultrasound-assisted extraction. The quality and functionality of the aquatic proteins could be improved after modification with polyphenols via covalent or noncovalent interactions. Furthermore, some aquatic protein based delivery systems, such as emulsions, gels, films, and microcapsules, have been reported to enhance the absorption and bioavailability of bioactive substances by in vitro GIT, cell, and in vivo animal models. By promoting comprehensive understanding, this review is expected to provide a real-time reference for developing functional foods and potential food delivery systems based on aquatic-derived proteins.

Waste-to-energy: Cellulase induced waste activated sludge and paper waste co-fermentation for efficient volatile fatty acids production and underlying mechanisms

This study mainly investigated the feasibility of utilizing cellulase to enhance waste activated sludge (WAS) and paper waste (PW) co-fermentation for the generation of volatile fatty acids (VFAs). The introduction of cellulase effectively enhanced the co-fermentation efficiency, and the maximum VFAs generation reached 3014 mg COD/L with 60 mg cellulase/g TSS while it was 1512 mg COD/L in the control reactor. The presence of cellulase evidently improved the concentration of soluble bioavailable substrates (e.g., carbohydrates and proteins) via inducing the EPS disintegration and PW disruption. More importantly, the functional anaerobes (i.e., Macellibacteroides and Bacteroides) and the microbial activities (i.e., ATP, key acid-forming enzymes, and genetic expressions) that related with the VFAs biosynthesis were enriched and enhanced due to the stimulation of cellulase, contributing to the ultimate VFAs promotion. This study provided a novel strategy to recover valuable products from waste biomass with constructive mechanistic exploration.

The fabrication of novel zein and resveratrol covalent conjugates: Enhanced thermal stability, emulsifying and antioxidant properties

Novel zein and resveratrol conjugates were fabricated by alkaline and free radical grafting reactions. The grafting efficiency and total phenolic content of alkaline treated conjugates were slightly higher than those of free radical grafting. Compared to native and alkaline treated zein, the sulfhydryl contents of conjugates were obviously decreased, confirming that nucleophilic addition of resveratrol to sulfhydryl group of zein formed stable CS covalent bonds. The conformation changes of zein modified by resveratrol were revealed by fourier transform infrared spectroscopy and fluorescence spectroscopy. Moreover, covalent modification changed isoelectric point of zein from 6.5 to 5.4 (alkaline) or 5.6 (free radical grafting), and broadening the pH application range of zein. It was worth mentioning that the conjugates showed much higher thermal stability, antioxidant activity, and emulsify activity than those of native zein. This study provides an effective way for the design of novel delivery systems to encapsulate bioactive substances.

Cardioprotective effect of icariin against myocardial fibrosis and its molecular mechanism in diabetic cardiomyopathy based on network pharmacology: Role of ICA in DCM

BACKGROUND

Diabetic cardiomyopathy (DCM) is one of the most severe symptoms of diabetes. It continues to be a major clinical problem, but our knowledge of its molecular mechanisms and effective treatments are limited. Traditional Chinese medicine has been shown to be a pool of novel drugs for diabetes.

PURPOSE

Herein, we aim to define the molecular mechanism of icariin (ICA), an extract from a traditional Chinese medicine herb, in protecting cardiac structures and restoring cardiac functions of in a rat model of type 2 diabetes mellitus (T2DM).

STUDY DESIGN AND METHODS

Candidate genes related to T2DM were identified through bioinformatics screening and their interactions were constructed by molecule docking technique, followed by pathway enrichment analyses of their cellular functions. A T2DM rat model was then established to evaluate the effects of ICA on cardiac structures, myocardial fibrosis, and cellular Ca²⁺ inflow, as reflected by HE and Masson staining, qRT-PCR and Western blot determination of related genes, and measurement of the L-type Ca²⁺ current.

RESULTS

Four potential target genes (Jun, p65, NOS3, and PDE5A) were identified. ICA ameliorated the structural damage and myocardial fibrosis in T2DM rats. Intracellular Ca2+ hyperactivities and dysfunction in myocardium of T2DM rats were also repressed by ICA treatment. Furthermore, ICA-induced inhibition of Jun and p65 ameliorated the irregular collagen metabolism and myocardial fibrosis. NOS3, PDE5A and the related sGC-cGMP-PKG signaling pathway mediated the ICA-induced improvement of intracellular Ca²⁺ inflow.

CONCLUSION

In conclusion, these results demonstrate the regulatory roles of potential target genes in DCM and suggest ICA as an effective treatment of DCM by targeting these genes specifically.