Characterization of Soybean Protein Isolate-Food Polyphenol Interaction via Virtual Screening and Experimental Studies

Polyphenols in different parts of Moringa oleifera Lam.: Composition, antioxidant and neuroprotective potential

Moringa oleifera Lam. (M. oleifera L.), a widely distributed tropical tree, is well-known for its rich polyphenolic content, which underlies its diverse biological activities. This study employed Q-Exactive Orbitrap/MS and Triple Quadrupole UPLC-MS to systematically analyze the phenolic composition in four parts of M. oleifera L.: leaves, flowers, seeds, and stems. Various polar fractions were obtained using solid-phase extraction, and their antioxidant activities were assessed using DPPH, ABTS, and FRAP assays. Additionally, the neuroprotective potential was evaluated in vitro using a hydrogen peroxide-induced PC-12 cell model. In total, 105 phenolic compounds and 61 other compounds were identified, with 59 compounds being characterized for the first time in M. oleifera L.. The phenolic composition of the leaves, flowers, and stems was primarily composed of flavonols and phenolic acids, while the seeds were predominantly composed of phenolic acids. Polyphenol content was highest in the leaves and stems, and lowest in the seeds. All extracts and fractions demonstrated significant antioxidant and neuroprotective activities, with the strongest effects observed in the leaves and in the ethyl ether and ethyl acetate-eluting fractions from all plant parts. These findings provide a comprehensive understanding of the phenolic profile of different parts of M. oleifera L., highlight novel polyphenolic compounds, and offer insights into their potential therapeutic applications.

Insight into the binding mechanism of rutin and lysozyme: Based on spectroscopy and molecular simulation technology

Lysozyme (LYZ) is an excellent natural food preservative and can also be used as a bioactive carrier loading small molecules to enhance its stability and antioxidant properties. This research explored the intricate mechanism of interaction between LYZ and rutin. Multiple spectroscopic techniques was used first to confirm that rutin caused a fluorescence burst in LYZ. LYZ amino acid microenvironment was altered. The main driving forces driving the formation of the complex between rutin and LYZ were hydrogen bonding and van der Waals forces. In addition, the incorporation of rutin improved the overall stability and oxidation resistance of the complexes. The results of molecular docking and molecular dynamics simulation further show that rutin and LYZ are stably bound by hydrogen bonds and other interactions. The investigation contributed precious information for the development of novel natural preservatives and the design of advanced small molecular carriers.

Sticky Polyelectrolyte Shield for Enhancing Biological Half-Life of Growth Factors

Delivery of secretomes, which includes growth factors, cytokines, and mRNA, is critical in regenerative medicine for cell-to-cell communication. However, the harsh in vivo environment presents significant challenges for secretome delivery. Proteolytic enzymes shorten secretomes' half-lives, and secretomes tend to rapidly diffuse at defect sites. Therefore, a delivery system that ensures prolonged retention and enhanced therapeutic efficacy of secretomes is required. In this study, a Coating Optimized Drug Delivery Enhancement (COD2E) system, a coacervate composed of dopamine functionalized fucoidan and poly-l-lysine, was fabricated for secretome delivery. The dopamine modification significantly enhanced adhesive strength (>7-fold) compared to that of the neat coacervates, which enabled rapid (5 min) and uniform coating ability on collagen sponges. The COD2E system was able to encapsulate fibroblast growth factor (FGF2) and prolong the half-life of FGF2. Notably, its efficacy, demonstrated through a single application of FGF2 encapsulated COD2E on collagen sponge, in a wound model demonstrated a successful tissue repair. The COD2E system is an effective growth factor delivery vehicle since it can protect growth factors, has an antioxidant ability, adheres on various material surfaces, and is hemocompatible.

Breaking barriers: Elevating legume protein functionality in food products through non-thermal technologies

Legume proteins have recently gained significant interest in the food industry for their eco-friendliness and nutritional qualities. Research shows that the replacement of specific animal protein sources with legume proteins presents sustainability and economic benefit. Nonetheless, legume proteins frequently exhibit inferior functional properties and palatability compared to animal proteins. Various non-thermal technologies, including high hydrostatic pressure, ultrasound, cold plasma, pulsed electric field, and dynamic high-pressure microjet, had been investigated to enhance the functional properties of legume proteins without loss of nutritional and sensory properties. Although these technologies show potential, no systematic study has been conducted to summarize and compare their effects on different legume proteins. This review aims to fill this gap by addressing the most promising approaches of non-thermal technologies for the modification of functional properties of legume proteins. New insights are discussed, elaborating the effect of non-thermal technologies on the structural and functional behavior of proteins.

Enhancement of non-covalent interaction between soy protein isolate and quercetin by sodium alginate

Effects of sodium alginate (SA) on the non-covalent interaction between soybean protein isolate (SPI) and quercetin (Que) were investigated by multispectral technology, molecular docking and dynamics simulation technology. Structural alterations of the binary complexes were observed after SA addition, characterized by a red shift of maximum fluorescence emission wavelength. The introduction of 0.1% (w/v) SA led to a reduction of 12.3% in the α-helix and β-sheet structures, accompanied by 12.6% increase in the β-turn and random coil conformations. The binding of SA to SPI provided electrostatic interactions and facilitated the subsequent binding of SPI to Que. Molecular docking confirmed that hydrophobic interactions and electrostatic interactions were also the main driving force. Molecular dynamics simulation emphasized that the ternary complexes with SA exhibited greater stability compared to the binary ones. The foaming and emulsifying properties of SPI-Que complexes were enhanced by 33.76% and 68.28%, respectively, due to the addition of SA.

Dairy and nondairy proteins as nano-architecture structures for delivering phenolic compounds: Unraveling their molecular interactions to maximize health benefits

Phenolic compounds are recognized for their benefits against degenerative diseases. Clinical and nutritional applications are limited by their low solubility, stability, and bioavailability, compromising their efficacy. Natural macromolecules, such as lipids, polysaccharides, and proteins, employed as delivery systems can efficiently overcome these limitations. In this sense, proteins are attractive due to their biocompatibility and dynamic structure properties, functional adaptability and self-assembly capabilities, offering stability, efficient encapsulation, and controlled release. This review explores the potential use of dairy proteins, caseins, and whey proteins, and, alternatively, nondairy proteins, gelatin, human serum albumin, maize zein, and soybean proteins, in building wall materials for the delivery of phenolic compounds. To optimize performance, aspects, such as protein-phenolic affinity and complex stability/activity, should be considered when designing particle nano-architecture. Molecular interactions between protein-phenolic compound complexes are, thus, further discussed, as well as the effects of temperature and pH and strategies to stabilize and preserve nano-architecture and retain phenolic compound activity. All proteins harbor one or more putative binding sites, shared or not, depending on the phenolic compound. Preservation techniques are still a case-to-case study, as no behavior patterns among different complexes are noted. Safety aspects necessary for the marketing of nanoproducts, such as characterization, toxicity assessments, and post-market monitoring as defined by the European Food Safety Authority and the Food and Drug Administration, are discussed, evidencing the need for a unified regulation. This review broadens our understanding and opens new opportunities for the development of novel protein-based nanocarriers to obtain more effective and stable products, enhancing phenolic compound delivery and health benefits.

Effect of Mono- and Polysaccharide on the Structure and Property of Soy Protein Isolate during Maillard Reaction

As a protein extracted from soybeans, soy protein isolate (SPI) may undergo the Maillard reaction (MR) with co-existing saccharides during the processing of soy-containing foods, potentially altering its structural and functional properties. This work aimed to investigate the effect of mono- and polysaccharides on the structure and functional properties of SPI during MR. The study found that compared to oat β-glucan, the reaction rate between SPI and D-galactose was faster, leading to a higher degree of glycosylation in the SPI-galactose conjugate. D-galactose and oat β-glucan showed different influences on the secondary structure of SPI and the microenvironment of its hydrophobic amino acids. These structural variations subsequently impact a variety of the properties of the SPI conjugates. The SPI-galactose conjugate exhibited superior solubility, surface hydrophobicity, and viscosity. Meanwhile, the SPI-galactose conjugate possessed better emulsifying stability, capability to produce foam, and stability of foam than the SPI-β-glucan conjugate. Interestingly, the SPI-β-glucan conjugate, despite its lower viscosity, showed stronger hypoglycemic activity, potentially due to the inherent activity of oat β-glucan. The SPI-galactose conjugate exhibited superior antioxidant properties due to its higher content of hydroxyl groups on its molecules. These results showed that the type of saccharides had significant influences on the SPI during MR.

Anthocyanins: Potential phytochemical candidates for the amelioration of non-alcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is described by too much hepatic fat deposition causing steatosis, which further develops into nonalcoholic steatohepatitis (NASH), defined by necroinflammation and fibrosis, progressing further to hepatic cirrhosis, hepatocellular carcinoma, and liver failure. NAFLD is linked to different aspects of the metabolic syndrome like obesity, insulin resistance, hypertension, and dyslipidemia, and its pathogenesis involves several elements including diet, obesity, disruption of lipid homeostasis, and a high buildup of triglycerides and other lipids in liver cells. It is therefore linked to an increase in the susceptibility to developing diabetes mellitus and cardiovascular diseases. Several interventions exist regarding its management, but the availability of natural sources through diet will be a benefit in dealing with the disorder due to the immensely growing dependence of the population worldwide on natural sources owing to their ability to treat the root cause of the disease. Anthocyanins (ACNs) are naturally occurring polyphenolic pigments that exist in the form of glycosides, which are the glucosides of anthocyanidins and are produced from flavonoids via the phenyl propanoid pathway. To understand their mode of action in NAFLD and their therapeutic potential, the literature on in vitro, in vivo, and clinical trials on naturally occurring ACN-rich sources was exhaustively reviewed. It was concluded that ACNs show their potential in the treatment of NAFLD through their antioxidant properties and their efficacy to control lipid metabolism, glucose homeostasis, transcription factors, and inflammation. This led to the conclusion that ACNs possess efficacy in the amelioration of NAFLD and the various features associated with it. However, additional clinical trials are required to justify the potential of ACNs in NAFLD.

Spray dried acerola (Malpighia emarginata DC) juice particles to produce phytochemical-rich starch-based edible films

This study aimed to produce spray dried acerola juice microparticles with different protein carriers to be incorporated into edible starch films. The microparticles were evaluated for solids recovery, polyphenol retention, solubility, hygroscopicity, particle size distribution, X-ray diffraction, phytochemical compounds and antioxidant activity. Acerola microparticles produced with WPI/hydrolysed collagen carriers (AWC) with higher solids recovery (53.5 ± 0.34% w/w), polyphenol retention (74.4 ± 0.44% w/w), high solubility in water (85.2 ± 0.4% w/w), total polyphenol content (128.45 ± 2.44 mg GAE/g) and good storage stability were selected to produce starch-based films by casting. As a result, cassava films with water vapour permeability of 0.29 ± 0.07 g mm/m2 h KPa, polyphenol content of 10.15 ± 0.22 mg GAE/g film and DPPH radical scavenging activity of 6.57 ± 0.13 μM TE/g film, with greater migration of polyphenol to water (6.30 ± 0.52 mg GAE/g film) were obtained. Our results show that the incorporation of phytochemical-rich fruit microparticles is a promising strategy to create biodegradable edible films.

Tartary buckwheat protein-phenol conjugate prepared by alkaline-based environment: Identification of covalent binding sites of phenols and alterations in protein structural and functional characteristics

Tartary buckwheat protein-rutin/quercetin covalent complex was synthesized in alkaline oxygen-containing environment, and its binding sites, conformational changes and functional properties were evaluated by multispectral technique and proteomics. The determination of total sulfhydryl and free amino groups showed that rutin/quercetin can form a covalent complex with BPI and could significantly reduce the group content. Ultraviolet-visible spectrum analysis showed that protein could form new characteristic peaks after binding with rutin/quercetin. Circular dichroism spectrum analysis showed that rutin and quercetin caused similar changes in the secondary structure of proteins, both promoting β-sheet to α-helix, β-ture and random coil transformation. The fluorescence spectrometry results showed that the combination of phenols can cause the fluorescence quenching, and the combination of rutin was stronger than the quercetin. Proteomics showed that there were multiple covalent binding sites between phenols and protein. Rutin had a high affinity for arginine, and quercetin and cysteine had high affinity. Meanwhile, the combination of rutin/quercetin and protein had reduced the surface hydrophobic ability of the protein, and improved the foaming, stability and antioxidant properties of the protein. This study expounded the mechanism of the combination of BPI and rutin/quercetin, and analysed the differences of the combination of protein and phenols in different structures. The findings can provide a theoretical basis for the development of complexes in the area of food.

Comparative study of dietary phenols with Tartary buckwheat protein (2S/13S): impact on structure, binding sites and functionality of protein

BACKGROUND

This research was to investigate the interaction mechanism between 2S albumin and 13S globulin (2S and 13S, the most important storage proteins in Tartary buckwheat seeds) and three phenols (rutin, quercetin and myricetin) regarding the structural and antioxidant properties of their complexes.

RESULTS

There are differences in the binding affinity of phenols for 2S and 13S. Rutin had a higher binding affinity for 2S, myricetin had a higher binding affinity for 13S, and 13S exhibited a higher affinity toward phenols than did 2S. Binding with phenols significantly changed the secondary and tertiary structures of 2S and 13S, decreased the surface hydrophobic value and enhanced the antioxidant capacity. Molecular docking and isothermal titration calorimetry showed that the binding processes were spontaneous and that there were hydrogen bonds, hydrophobic bonds and van der Waals force interactions between phenols and proteins.

CONCLUSION

These findings could provide meaningful guidance for the further application of buckwheat protein complex. © 2023 Society of Chemical Industry.

Virtual Screening of Soybean Protein Isolate-Binding Phytochemicals and Interaction Characterization

Soybean protein isolate (SPI) and small molecule interactions have drawn more and more attention regarding their benefits for both parts, while research on large-scale investigations and comparisons of different compounds is absent. In this study, a high throughput virtual screening was applied on a phytochemical database with 1130 compounds to pinpoint the potential SPI binder. Pentagalloylglucose, narcissoside, poliumoside, isoginkgetin, and avicurin were selected as the top-five ranking molecules for further validation. Fluorescence quenching assays illustrated that isoginkgetin has a significantly higher apparent binding constant (Ka) of (0.060 ± 0.020) × 106 L·mol-1, followed by avicularin ((0.058 ± 0.010) × 106 L·mol-1), pentagalloylglucose ((0.049 ± 0.010) × 106 L·mol-1), narcissoside ((0.0013 ± 0.0004) × 106 L·mol-1), and poliumoside ((0.0012 ± 0.0006) × 106 L·mol-1). Interface characterization by MD simulation showed that protein residues E172, H173, G202, and V204 are highly involved in hydrogen bonding with the two carbonyl oxygens of isoginketin, which could be the crucial events in SPI binding. Van der Waals force was identified as the major driven force for isoginketin binding. Our study explored SPI-phytochemical interaction through multiple strategies, revealing the molecular binding details of isoginkgetin as a novel SPI binder, which has important implications for the utilization of the SPI-phytochemical complex in food applications.

Structural changes and molecular mechanism study on the inhibitory activity of epigallocatechin against α-glucosidase and α-amylase

In this study, the inhibition and mechanism of epigallocatechin (EGC) on two key glycoside hydrolases (α-glucosidase, α-amylase) were explored from the molecular structure level. The chemical structure of EGC was characterized by X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, and proton nuclear magnetic resonance spectroscopy. EGC's inhibition on these enzymes was colorimetrically determined. The effects of EGC on the chemical structure and spatial configuration of the enzymes were explored via FTIR spectroscopy, fluorescence spectroscopy, and molecular docking techniques. The results showed that EGC exhibited the inhibition of α-glucosidase and α-amylase in a non-competitive manner, showing a continuous upward trend as EGC's concentration increased. There was a fluorescence quenching effect of EGC on α-glucosidase and α-amylase. Molecular docking confirmed that EGC can bind to amino acid residues in the enzyme through intermolecular hydrogen bonds and hydrophobic interactions, resulting in the changed chemical structure and spatial conformation of the enzymes. This decreased enzyme activity. This result suggested that EGC has the potential to inhibit two key glycoside hydrolases, and it would be beneficial to incorporate EGC into functional foods for diabetics.

Changes on the conformational and functional properties of soybean protein isolate induced by quercetin

The conformational changes and functional properties of SPI induced by quercetin was investigated via fourier transform infrared (FTIR) spectroscopy, fluorescence spectroscopy, circular dichroism (CD) spectroscopy and molecular docking. A decrease in the fluorescence intensity and a blue shift in the maximum wavelength were observed due to the binding process with fluorescent residues. The analysis of Stern-Volmer equation showed that the fluorescence quenching induced by quercetin took the form of static quenching, and the binding stoichiometry between SPI and quercetin was 1:1. The values of ΔH and ΔS were both positive illustrating that hydrophobic interaction was the primary binding force between quercetin and SPI. Results of FTIR and CD indicated that the binding with quercetin changed the secondary structure of SPI, resulting in a partially unfolded and more flexible structure. SDS-PAGE confirmed there was no covalent interaction between the two constituents. Molecular docking demonstrated that there were stable configurations and high matching degrees in both 11S and 7S proteins with quercetin via hydrogen bonds and hydrophobic interactions. Meanwhile, modification by quercetin enhanced the foaming and emulsifying capacities of SPI. These findings might provide theory reference for elucidation the mechanism of polyphenols-proteins interaction and development of related food additive products in future.

Different interactions driving the binding of soy proteins (7S/11S) and flavonoids (quercetin/rutin): Alterations in the conformational and functional properties of soy proteins

The purpose of this research was to comparatively investigate the interactions between bioactive flavonoids (quercetin and rutin) and two predominant soy proteins (β-conglycinin and glycinin), and the structural and functional properties of their complexes. The binding affinities of quercetin/rutin toward 7S/11S were structure-dependent, in that rutin had a higher binding affinity than that of quercetin, and 11S exhibited higher affinity toward quercetin/rutin than that of 7S. The interactions in the 7S/11S-quercetin complexes were driven by van der Waals forces and hydrogen-bonding interactions, whereas the 7S/11S-rutin complexes exhibited hydrophobic interactions. Binding to quercetin or rutin altered the secondary structures (decrease in the α-helix and random coil contents and increase in the β-sheet content), decreased the surface hydrophobicity and thermal stability, and enhanced the antioxidant capacity of 7S and 11S. These findings provide valuable information that can facilitate the design of custom-tailored protein-flavonoid macromolecules.