Insight into the inactivation mechanism of soybean Bowman-Birk trypsin inhibitor (BBTI) induced by epigallocatechin gallate and epigallocatechin: Fluorescence, thermodynamics and docking studies

Advancements in Inactivation of Soybean Trypsin Inhibitors

Soybean Trypsin Inhibitors (STIs) in soy-based foods have negative effects on soybean protein digestion and pancreatic health of humans. The inactivation of STIs is a critical unit operation aimed at enhancing the nutritional properties of soy-based foods during processing. This paper reviews the structure of STIs and soybean proteins, as well as the mechanisms of digestion. Various technologies (physical, chemical, biological) have been used to inactivate STIs. Their parameter settings, operating procedures, advantages, and disadvantages are also described. Mechanisms of inactivation of STIs (Kunitz trypsin inhibitor (KTI) and Bowman-Birk inhibitor (BBI)) conformations under different treatments are clarified. In addition, emerging technologies, e.g., Ohmic Heating, Electron Beam Irradiation, Dielectric-Barrier Discharge, and probiotics, have demonstrated great potential to inactivate STIs. We advise that multiple emerging technologies should combine with other unit operating systems to maximize inactivation efficiency.

Study on the effects of endogenous polyphenols on the structure, physicochemical properties and in vitro digestive characteristics of Euryales Semen starch based on multi-spectroscopies, enzyme kinetics, molecular docking and molecular dynamics simulation

Euryales Semen (ES) is a highly nutritious food with low digestibility, which is closely associated with its endogenous phenolic compounds. In this study, five phenolic compounds (naringenin, isoquercitrin, gallic acid, epicatechin and quercetin) with high concentrations in ES were selected to prepare starch-polyphenol complexes. Subsequently, the effects of endogenous polyphenols on the structure, physicochemical properties and digestion characteristics of ES starch were studied using multiple techniques. The addition of phenolic compounds markedly reduced the in vitro digestibility, swelling power, gelatinization enthalpy, while increased the solubility of ES starch. Fourier-transform infrared spectroscopy and X-ray diffraction analysis showed that phenolic compounds interacted with the starch through non-covalent bonds. Five phenolic compounds inhibited α-amylase activity through a mixed competitive inhibition mechanism, with the inhibition potency ranked as follows: quercetin > epicatechin > gallic acid > isoquercitrin > naringenin. The spectroscopic analysis and molecular dynamics simulations confirmed that five phenolic compounds interacted with the amino acid residues of α-amylase through hydrogen bonding and hydrophobic interactions, caused α-amylase static fluorescence quenching, and altered its conformation and microenvironment. This study provides a better understanding of the interaction mechanisms between ES starch and polyphenols, and supports the development of ES as a food that lowers sugar levels.

Effects of myricetin and its derivatives on nonenzymatic glycation: A mechanism study based on proteomic modification and fluorescence spectroscopy analysis

Myricetin and its derivatives, myricitrin and dihydromyricetin, are flavonoids widely presented in foods and phytomedicine that possess tremendous health potential. In this study, we compared the antiglycation activity of myricetin and its derivatives, then investigated the underlying mechanism using proteomic modification and fluorescence spectroscopy analysis. All three compounds exhibited thorough inhibition on nonenzymatic glycation process, with the inhibitory effects on AGEs reaching 85% at 40 μmol/L. They effectively protected bovine serum albumin (BSA) structure by inhibiting protein oxidation, preventing the conversion from α-helix to β-sheet, and reducing amyloid-like cross-β structure formation. Among the three compounds, myricetin showed a predominant antiglycation activity. Proteomic analysis identified the early glycated sites that were protected by myricetin, including lysine K235, 256, 336, 421, 420, 489, etc. Additionally, fluorescence spectroscopy revealed spontaneous interactions between BSA and myricetin. Overall, myricetin holds promise as an antiglycation agent in both the food and drug industries.

Spectroscopy combined with spatiotemporal multiscale strategy to study the adsorption mechanism of soybean protein isolate with meat flavor compounds (furan): Differences in position and quantity of the methyl

The interaction mechanism between soybean protein isolate (SPI) and furan flavor compounds with different structures is studied using spectroscopy, molecular docking, and MD simulation methods. The order of binding ability between SPI and furan flavor compounds is 2-acetylfuran>furfural>5-methylfurfural. The structural differences (position and quantity of methyl groups) of three furan flavor compounds are key factors leading to the different adsorption abilities of SPI for furan flavor compounds. The findings from spectroscopy analyses suggest that the interaction between SPI and furan flavor compounds involves both static and dynamic quenching mechanisms, with static quenching being the main factor. Molecular docking and MD simulations reveal the atomic-level mechanisms underlying the stable binding for SPI and furan flavor compounds at spatiotemporal multiscale. This study provides a theoretical framework for the production and adjustment of meat essence formula in the production of soybean protein-based meat products.

Structural Characterization of the Staphylococcus aureus Targeting Lectin Peptides from Garlic (Allium sativum L) by Liquid Nitrogen Grinding Coupled with the Proteomic and Antimicrobial Mechanism Analysis

Garlic has long been used as an antimicrobial spice and herbal remedy. The aim of this study was to isolate the antimicrobial agent in garlic water extract against Staphylococcus aureus (S. aureus) and investigate its antimicrobial mechanism. By an activity-guided separation, garlic lectin-derived peptides (GLDPs) with main molecular weight of around 12 kDa were extracted by liquid nitrogen grinding and identified with high bactericidal activity toward S. aureus, and the MIC was determined as 24.38 μg/mL. In-gel digestion-based proteomic analysis indicated that the peptide sequences were highly identical to the B strain of garlic protein lectin II. Structure analysis suggested that the secondary structure was strongly affected by lyophilization and thus resulted in the inactivation of GLDPs (P < 0.05). Mechanism study revealed that treatment of GLDPs resulted in cell membrane depolarization in a dose-dependent manner, and the disruptions of the cell wall and membrane integrities were observed under electric microscopies. GLDPs could successfully dock with cell wall component lipoteichoic acid (LTA) via van der Waals and conventional bonds in molecular docking analysis. These results suggested that GLDPs were responsible for the S. aureus targeting activity and might be promising candidates for antibiotic development against bacterial infection.

Screening of α-Glucosidase Inhibitors in Cichorium glandulosum Boiss. et Huet Extracts and Study of Interaction Mechanisms

Cichorium glandulosum Boiss. et Huet (CGB) extract has an α-glucosidase inhibitory effect (IC50 = 59.34 ± 0.07 μg/mL, positive control drug acarbose IC50 = 126.1 ± 0.02 μg/mL), but the precise enzyme inhibitors implicated in this process are not known. The screening of α-glucosidase inhibitors in CGB extracts was conducted by bioaffinity ultrafiltration, and six potential inhibitors (quercetin, lactucin, 3-O-methylquercetin, hyperoside, lactucopicrin, and isochlorogenic acid B) were screened as the precise inhibitors. The binding rate calculations and evaluation of enzyme inhibitory effects showed that lactucin and lactucopicrin exhibited the greatest inhibitory activities. Next, the inhibiting effects of the active components of CGB, lactucin and lactucopicrin, on α-glucosidase and their mechanisms were investigated through α-glucosidase activity assay, enzyme kinetics, multispectral analysis, and molecular docking simulation. The findings demonstrated that lactucin (IC50 = 52.76 ± 0.21 μM) and lactucopicrin (IC50 = 17.71 ± 0.64 μM) exhibited more inhibitory effects on α-glucosidase in comparison to acarbose (positive drug, IC50 = 195.2 ± 0.30 μM). Enzyme kinetic research revealed that lactucin inhibits α-glucosidase through a noncompetitive inhibition mechanism, while lactucopicrin inhibits it through a competitive inhibition mechanism. The fluorescence results suggested that lactucin and lactucopicrin effectively reduce the fluorescence of α-glucosidase by creating lactucin-α-glucosidase and lactucopicrin-α-glucosidase complexes through static quenching. Furthermore, the circular dichroism (CD) and Fourier transform infrared spectroscopy (FT-IR) analyses revealed that the interaction between lactucin or lactucopicrin and α-glucosidase resulted in a modification of the α-glucosidase's conformation. The findings from molecular docking and molecular dynamics simulations offer further confirmation that lactucopicrin has a robust binding affinity for certain residues located within the active cavity of α-glucosidase. Furthermore, it has a greater affinity for α-glucosidase compared to lactucin. The results validate the suppressive impact of lactucin and lactucopicrin on α-glucosidase and elucidate their underlying processes. Additionally, they serve as a foundation for the structural alteration of sesquiterpene derived from CGB, with the intention of using it for the management of diabetic mellitus.

Characterization of PKCα-rutin interactions and their application as a treatment strategy for pulmonary arterial hypertension by inhibiting ferroptosis

As a common plant-derived dietary flavonoid, rutin receives widespread attention because of its good antioxidant bioactivities. Protein kinase Cα (PKCα) is a serine/threonine kinase that is involved in uncountable cellular processes, among which ferroptosis, a novel form of cell death, is triggered by lipid peroxidation and has been reported to be associated with pulmonary arterial hypertension (PAH). But it is still not well appreciated how rutin inhibits ferroptosis in PAH and what function PKCα has in this process. In this study, we first observed whether rutin could prevent PAH by attenuating ferroptosis with a PAH animal model and pulmonary artery smooth muscle cells (PASMCs) under hypoxia. Mitochondrial metabolomics and network pharmacology were employed to clarify the metabolic alterations and screen target proteins, and the results showed that PKCα was a vital node in rutin regulating mitochondrial metabolism related to ferroptosis in PAH. Based on molecular docking and multispectral analysis, we found that rutin could directly interact with PKCα through hydrogen bonds, which could induce static quenching, and then influence the secondary structure of PKCα. In conclusion, these findings mainly point to a novel mechanism that rutin protects PAH rats by modifying the structure and altering the activity of PKCα, and thus suppressing ferroptosis. This work reveals that the interaction behaviors between small molecules and bio-macromolecules are a critical factor to develop natural biological active ingredients and gives an insight into the potential applications of flavonoids in health and disease.

Transport proteins and their differential roles in the accumulation of phenanthrene in wheat

The study focuses on the uptake, accumulation, and translocation of polycyclic aromatic hydrocarbons (PAHs) in cereals, specifically exploring the role of peroxidase (UniProt accession: A0A3B5XXD0, abbreviation: PX1) and unidentified protein (UniProt accession: A0A3B6LUC6, abbreviation: UP1) in phenanthrene solubilization within wheat xylem sap. This research aims to clarify the interactions between these proteins and phenanthrene. Employing both in vitro and in vivo analyses, we evaluated the solubilization capabilities of recombinant transport proteins for phenanthrene and examined the relationship between protein expression and phenanthrene concentration. UP1 displayed greater transport efficiency, while PX1 excelled at lower concentrations. Elevated PX1 levels contributed to phenanthrene degradation, marginally diminishing its transport. Spectral analyses and molecular dynamics simulations validated the formation of stable protein-phenanthrene complexes. The study offers crucial insights into PAH-related health risks in crops by elucidating the mechanisms of PAH accumulation facilitated by transport proteins.

Construction of the Gal-NH2/mulberry leaf polysaccharides-lysozyme/luteolin nanoparticles and the amelioration effects on lipid accumulation

Luteolin is a kind of natural flavonoid with great potential for lipid accumulation intervention. However, the poor water solubility and non-targeted release greatly diminish its efficiency. In this study, 4-aminophenyl β-D-galactopyranoside (Gal-NH2)/mulberry leaf polysaccharides- lysozyme/luteolin nanoparticles (Gal-MPL/Lut) were fabricated via amide reaction, self-assembly process and electrostatic interaction. The nanoparticles could hepatic-target of Lut and enhance action on liver tissue by specific recognition of asialoglycoprotein receptor (ASGPR). Physicochemical characterization of the nanoparticles showed a spherical shape with a uniform particle size distribution (77.8 ± 2.6 nm) with a polydispersity index (PDI) of 0.22 ± 0.06. Subsequently, in HepG2 cells model, administration with hepatic-targeted Gal-MPL/Lut nanoparticles promoted the cellular uptake of Lut, and regulated lipid metabolism manifested by remarkably inhibiting total cholesterol (TC) and triglyceride (TG) expression levels through the modulation of PI3K/SIRT-1/FAS/CEBP-α signaling pathway. This study provides a promising strategy for a highly hepatic-targeted therapy to ameliorate lipid accumulation using natural medicines facilitated by nano-technology.

Polyphenol-fortified extruded sweet potato starch vermicelli: Slow-releasing polyphenols is the main factor that reduces the starch digestibility

To investigate the digestive behavior of extruded starch-polyphenols system, extruded sweet potato starch vermicelli (ESPSV) was used as a model. The multi-scale structure, starch digestibility, polyphenol release, digestive enzyme activity during digestion and their correlation of ESPSV supplemented with matcha (MT), green tea extract (GTE), tea polyphenols (TP) and epigallocatechin gallate (EGCG) (at 1% polyphenol level) were discussed. Results showed that tea products in whatever form could retard starch digestion, with EGCG working best. The predicted glycemic index (pGI) of ESPSV was decreased from 82.50 to 65.46 after adding EGCG. Starch formed larger molecular aggregates with tea products under extrusion, showing a "B + V" type pattern. The order of V-type crystals content was EGCG + ESPSV (1.41) > TP + ESPSV (1.50) > GTE + ESPSV (1.88) > MT + ESPSV (2.62) > ESPSV (3.20). Under external pressure, EGCG, as tea monomer, was more likely to enter the spiral cavity of amylose and form V-type inclusion complex. Notably, polyphenols released during digestion could still reduce digestive enzyme activity, with a 15.53% decrease in EGCG + ESPSV compared to ESPSV. This was verified by correlation analysis, where RDS content (0.961, p < 0.01) and pGI (0.966, p < 0.01) were highly significantly correlated with the enzyme activity. Furthermore, tea products did not break or even enhance the quality of ESPSV as the final product.

Effect of Medium Chain Triglycerides on the Digestion and Quality Characteristics of Tea Polyphenols-Fortified Cooked Rice

Nowadays, medium chain triglycerides (MCT) with special health benefits have been increasingly applied for fortifying food products. Therefore, the present work aimed to investigate the effects of MCT on traditional tea polyphenols-fortified cooked rice (TP-FCR). It was visualized by DSC, CLSM, XRD, FT-IR, and Raman spectroscopy. The higher content of starch-MCT complexes with an increase in the relative crystallinity and the generation of short-range ordered structures contributed to a more ordered and compact molecular arrangement, which can hinder the action of digestive enzymes on starch. SEM demonstrated that MCT transformed the microstructure of TP-FCR into a denser and firmer character, making it an essential component hindering the accessibility of digestive enzymes to starch granules and slowing the release of tea polyphenols in TP-FCR to attenuate starch digestion. Consequently, the addition of MCT reduced the polyphenol-regulated starch digestibility from 74.28% in cooked white rice to 64.43% in TP-FCR, and further down to 50.82%. Besides, MCT also reduced the adhesiveness and improved the whiteness of TP-FCR. The findings suggested that MCT incorporation could be a potential strategy in cooked rice production to achieve high sensory quality and low glycemic cooked rice.

Soybean genetics, genomics, and breeding for improving nutritional value and reducing antinutritional traits in food and feed

Soybean [Glycine max (L.) Merr.] is a globally important crop due to its valuable seed composition, versatile feed, food, and industrial end-uses, and consistent genetic gain. Successful genetic gain in soybean has led to widespread adaptation and increased value for producers, processors, and consumers. Specific focus on the nutritional quality of soybean seed composition for food and feed has further elucidated genetic knowledge and bolstered breeding progress. Seed components are historical and current targets for soybean breeders seeking to improve nutritional quality of soybean. This article reviews genetic and genomic foundations for improvement of nutritionally important traits, such as protein and amino acids, oil and fatty acids, carbohydrates, and specific food-grade considerations; discusses the application of advanced breeding technology such as CRISPR/Cas9 in creating seed composition variations; and provides future directions and breeding recommendations regarding soybean seed composition traits.

An Updated Review of Soy-Derived Beverages: Nutrition, Processing, and Bioactivity

The global market for plant-based drinks is experiencing rapid growth driven by consumer demand for more sustainable diets, including vegetarian and vegan options. Soy beverages in particular are gaining popularity among individuals with lactose intolerance and milk protein allergies. They are considered an excellent source of high-quality protein, vitamin B, unsaturated fatty acids, and beneficial phytochemicals such as phytosterols, soy lecithins, and isoflavones. This review presents a comprehensive market survey of fifty-two soy beverages available in Spain and other European countries. The predominant category among those evaluated was calcium and vitamin-fortified drinks, accounting for 60% of the market. This reflects the need to address the nutritional gap compared to cow's milk and meet essential dietary requirements. The review covers the technological aspects of industrial soy milk production, including both traditional methods and innovative processing techniques. Additionally, it analyzes multiple studies and meta-analyses, presenting compelling evidence for the positive effects of soy beverages on various aspects of health. The review specifically examines the contributions of different components found in soy beverages, such as isoflavones, proteins, fiber, and oligosaccharides. Moreover, it explores controversial aspects of soy consumption, including its potential implications for growth, puberty, fertility, feminization, and the thyroid gland.

Exploration of the inhibitory mechanisms of trans-polydatin/resveratrol on α-glucosidase by multi-spectroscopic analysis, in silico docking and molecular dynamics simulation

Plant-derived phenolics as natural α-glucosidase (α-GLU) inhibitors have attached great attention in the treatment of type-II diabetes mellitus currently. In this study, trans-polydatin and its aglycone resveratrol were found to show a notable inhibitory activity on α-GLU in a mixed-type manner with IC₅₀ values of 18.07 and 16.73 μg/mL, respectively, which were further stronger than anti-diabetic drug acrabose (IC₅₀ = 179.86 μg/mL). Multi-spectroscopic analysis results indicated that polydatin/resveratrol bound to α-GLU with one affinity binding site which was mainly driven by hydrogen bonds and van der Waals forces, and this binding process resulted in conformational alteration of α-GLU. In silico docking study showed that polydatin/resveratrol can well interact with the surrounding amino acid residues in the active cavity of α-GLU. Molecular dynamics simulation further clarified the structure and characterization of α-GLU-polydatin/resveratrol complexes. This study might supply a theoretical basis for the designing of novel functional foods with polydatin/resveratrol.

Mechanistic studies of polyphenols reducing the trypsin inhibitory activity of ovomucoid: Structure, conformation, and interactions

Ovomucoid (OVM) is a critical anti-nutritional factor in egg, which may reduce nutrient utilization. In this study, the effects of polyphenols on the trypsin inhibitory activity (TIA) of OVM were investigated by exploring the structural changes and interaction mechanisms. The results found that TIA decreased to 62.34% and 90.41% as epigallocatechin gallate (EGCG) and gallic acid (GA) were added individually. EGCG and GA interacted with OVM via static quenching and hydrophobic interaction. They induced a transition of OVM conformation from disorder to order. Infrared and fluorescence quenching analysis showed that the interaction between EGCG or GA and OVM was spontaneous, and hydrophobic interaction was the predominant force. The mechanism suggested that polyphenols affect the protein conformation by spontaneously binding to OVM in hydrophobic interactions, and lowering the TIA through reduced hydrophobicity. In summary, EGCG may be a promising OVM trypsin activity inactivator, which could also guarantee safety of egg products.

Structural change study of pepsin in the presence of spermidine trihydrochloride: Insights from spectroscopic to molecular dynamics methods

Spermidine is an aliphatic polyamine that directs a set of biological processes. This work aimed to use UV-Vis spectroscopy, fluorescence spectroscopy, thermal stability, kinetic methods, docking, and molecular dynamic simulations to examine the influence of spermidine trihydrochloride (SP) on the structure and function of pepsin. The results of the fluorescence emission spectra indicated that spermidine could quench pepsin's intrinsic emission in a static quenching process, resulting in the formation of the pepsin-spermidine complex. The results discovered that spermidine had a strong affinity to the pepsin structure because of its high binding constant. The obtained results from spectroscopy and molecular dynamic approaches showed the binding interaction between spermidine and pepsin, induced micro-environmental modifications around tryptophan residues that caused a change in the tertiary and secondary structure of the enzyme. FTIR analysis showed hypochromic effects in the spectra of amide I and II and redistribution of the helical structure. Moreover, the molecular dynamic (MD) and docking studies confirmed the experimental data. Both experimental and molecular dynamics simulation results clarified that electrostatic bond interactions were dominant forces.

Study on the Interaction Mechanism of Methoxy Polyethylene Glycol Maleimide with Sweet Potato β-Amylase

In this study, sweet potato β-amylase (SPA) was modified by methoxy polyethylene glycol maleimide (molecular weight 5000, Mal-mPEG5000) to obtain the Mal-mPEG5000-SPA modified β-amylase and the interaction mechanism between SPA and Mal-mPEG5000 was investigated. the changes in the functional groups of different amide bands and modifications in the secondary structure of enzyme protein were analyzed using infrared spectroscopy and circular dichroism spectroscopy. The addition of Mal-mPEG5000 transformed the random curl in the SPA secondary structure into a helix structure, forming a folded structure. The Mal-mPEG5000 improved the thermal stability of SPA and protected the structure of the protein from breaking by the surrounding. The thermodynamic analysis further implied that the intermolecular forces between SPA and Mal-mPEG5000 were hydrophobic interactions and hydrogen bonds due to the positive values of ΔHθ and ΔSθ. Furthermore, the calorie titration data showed that the binding stoichiometry for the complexation of Mal-mPEG5000 to SPA was 1.26, and the binding constant was 1.256 × 107 mol/L. The binding reaction resulted from negative enthalpy, indicating that the interaction of SPA and Mal-mPEG5000 was induced by the van der Waals force and hydrogen bonding. The UV results showed the formation of non-luminescent material during the interaction, the Fluorescence results confirmed that the mechanism between SPA and Mal-mPEG5000 was static quenching. According to the fluorescence quenching measurement, the binding constant (KA) values were 4.65 × 104 L·mol-1 (298K), 5.56 × 104 L·mol-1 (308K), and 6.91 × 104 L·mol-1 (318K), respectively.

Effect of Catechin on Yolk Immunoglobulin Structure and Properties: A Polyphenol-Protein Interaction Approach

The preparation of the interaction between polyphenols and protein is of great significance for increasing added value and promoting the application of egg yolk immunoglobulin (IgY). This study systematically investigated the effect of catechin on yolk immunoglobulin structural characteristics and functional properties. The binding conditions, force types, molecular conformation, and residual microenvironment of the interaction between catechin and IgY were analyzed by molecular docking technology, UV-vis absorption and fluorescence spectroscopy studies. The results showed that the main binding forces in the complex were hydrogen bonding and van der Waals forces. After the interaction, fluorescence quenching occurred and the maximum emission wavelength was redshifted. The results showed that the microenvironment around IgY increased polarity, increased hydrophilicity and decreased hydrophobicity, and the structure of the peptide chain changed. The bacteriostatic thermal stability of the compound against Escherichia coli and Staphylococcus aureus was lower than that of catechin IgY. The bacteriostatic acid and base stability were higher than that of catechin and IgY. The antioxidant activity was catechin, complex, and IgY, in descending order. The antioxidant activity of catechin and complex was significantly higher than that of IgY. At the same concentration, the apparent viscosity of the three samples was complex, IgY and catechin, in descending order. G' was greater than G" indicating that elastic properties dominate in G". The G' and G" values of the complex were higher than those of the other groups. Rheological results indicated that the complex may have high physical stability. This study provides theoretical support for broadening the application field of IgY and suggest its properties change in the machining process. It also provides new ideas for the development of functional foods from poultry eggs.

Study on the interaction mechanism between luteoloside and xanthine oxidase by multi-spectroscopic and molecular docking methods

Gout is an inflammatory joint disease caused by urate crystal deposition, which is associated with hyperuricemia. Gout will take place when the uric acid accumulates. Xanthine oxidase (XO) is a crucial enzyme in the formation of uric acid. Inhibiting XO is one of the means to ameliorate gout. Luteoloside is a kind of natural flavonoid, which has an excellent prospect for relieving gout. But there are few reports on the interaction mechanism between luteoloside and XO currently. In this study, the interaction mechanism between luteoloside and XO was explored using spectroscopy and molecular docking. The fluorescence spectroscopy results indicated that luteoloside could make the intrinsic fluorescence of XO quenched, and the binding constant between luteoloside and XO was (1.85 ± 0.22) × 10³  L mol^-1 at 298 K. The synchronous fluorescence spectroscopy results showed that the absorption peaks of Tyr and Trp shifted blue, and the hydrophobicity of the microenvironment increased. Moreover, CD spectra showed that α-helix of XO decreased, β-sheet and β-turn increased after adding luteoloside. The results of molecular docking analysis showed that XO could combine with luteoloside through hydrogen bonds and hydrophobic force. The results indicated that luteoloside could remarkably interact with XO. Insights into the interaction mechanism provide a necessary basis for the search for low-toxic natural products as targets of XO. HIGHLIGHTS: Luteoloside and xanthine oxidase was a strong binding mode and had only one binding site. Luteoloside could cause α-helix reduced, β-sheet and β-turn increased, and change the secondary structure of XO. The binding between luteoloside and xanthine oxidase was a spontaneous process. The main binding force was hydrophobic force between luteoloside and xanthine oxidase.

Green tea polyphenols bind to soy proteins and decrease the activity of soybean trypsin inhibitors (STIs) in heated soymilk

The interaction between epigallocatechin gallate (EGCG) and soy proteins at room temperature (25 °C) and after heating at 100 and 121 °C, and their effects on the inactivation of soybean trypsin inhibitors (STIs) in soymilk were investigated. The results of the nitroblue tetrazolium (NBT) staining assay showed that soy proteins can covalently bind to EGCG. The α/α' and A subunits in heated soymilk preferred to bind to EGCG because of their soluble state. More thiols were trapped when EGCG was added before thermal processing, and the free amino groups were depleted more with EGCG addition after heating. Circular dichroism and fluorescence spectroscopy showed that EGCG addition before or after heating induced different secondary and tertiary structural changes for soy proteins. The exposed aromatic amino acids preferred to react with EGCG before protein aggregation in the heating process. The random coil of soymilk proteins increased more when EGCG was added in soymilk after heating, resulting in more disordered structures in protein conformation. The binding between EGCG and soy proteins promoted protein aggregation, which was confirmed by the particle size distribution and gel electrophoresis. The trypsin and chymotrypsin inhibitory activity (TIA and CIA) in soymilk significantly reduced to 693 U mL-1 and 613 U mL-1, respectively, under the conditions of 2 mM EGCG addition after 100 °C heating for 10 min (p < 0.05). Consequently, the influence of EGCG on STI inactivation in soymilk only worked when EGCG was added after heating.

Spheroidization of ultrasonic degraded corn silk polysaccharide to enhance bioactivity by the anti-solvent precipitation method

BACKGROUND

Corn silk is a very important by-product of corn production with medicinal value. Corn silk polysaccharide (CSP) is the main active ingredient. In the present study, ultrasound and spheroidization by anti-solvent were applied to improve the biological activity of CSP.

RESULTS

The results showed that ultrasonic degradation improved the α-glucosidase inhibitory activity of CSP by changing its physicochemical characteristics. As the anti-solvent ratio increased, the particle size of the nanoparticles (NPs) from the spheroidization of ultrasonic-degraded corn silk polysaccharide (UCSP) gradually increased, and NP-1 exhibited the highest inhibitory effect of α-glucosidase. Isothermal titration calorimetry (ITC) results indicated that the enhanced activity might be due to more α-glucosidase binding sites with NP-1 compared with no spheroidization. Western blotting results showed that NP-1 could improve the 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl) amino]-2-deoxy-d-glucose (2-NBDG) uptake in the L6 cells by regulating the phosphatidylinositol 3-kinase (PI3K)/Akt signal pathway and the translocation of glucose transporter 4 (GLUT4). NP-1 also exhibited excellent stability in different environments.

CONCLUSION

The study revealed that ultrasonic treatment and spheroidization processing showed potential applications for improving the biological activity of polysaccharides. © 2021 Society of Chemical Industry.

Effect of Fe (III), Zn (II), and Cr (III) complexation on the physicochemical properties and bioactivities of corn silk polysaccharide

In this paper, Fe (III), Zn (II), and Cr (III) were used to complex with corn silk polysaccharide (CSP) by classical methods and CSP-Fe, CSP-Zn, and CSP-Cr were successfully synthesized, respectively. The physicochemical properties and structural features were characterized by chemical composition analysis, inductive coupled plasma-mass spectrometry (ICP-MS), ultraviolet-visible (UV-Vis) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, fourier transform infrared (FT-IR) spectroscopy, circular dichroism (CD) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC), respectively. The antioxidant activities and inhibitory effects on α-glucosidase of CSP, CSP-Fe, CSP-Zn, and CSP-Cr were compared. The results showed that the Fe (III), Zn (II), and Cr (III) chelation could change the morphology, conformation, thermostability, and biological activities of CSP. CSP-Zn exhibited higher antioxidant activities and inhibition effects on α-glucosidase than CSP, which suggested that it could be considered as a potential candidate for developing an ingredient of functional foods for antidiabetics.

The Potential Utilization of High-Fiber Agricultural By-Products as Monogastric Animal Feed and Feed Additives: A Review

With the increase in world food demand, the output of agricultural by-products has also increased. Agricultural by-products not only contain more than 50% dietary fiber but are also rich in functional metabolites such as polyphenol (including flavonoids), that can promote animal health. The utilization of dietary fibers is closely related to their types and characteristics. Contrary to the traditional cognition that dietary fiber reduces animal growth, it can promote animal growth and maintain intestinal health, and even improve meat quality when added in moderate amounts. In addition, pre-fermenting fiber with probiotics or enzymes in a controlled environment can increase dietary fiber availability. Although the use of fiber has a positive effect on animal health, it is still necessary to pay attention to mycotoxin contamination. In summary, this report collates the fiber characteristics of agricultural by-products and their effects on animal health and evaluates the utilization value of agricultural by-products.

Regulating inhibitory activity of potato I-type proteinase inhibitor from buckwheat by rutin and quercetin

This study aims to investigate the effects of two flavonoids, rutin and quercetin, on inhibitory activity of recombinant buckwheat trypsin inhibitor (rBTI). We found that rutin and quercetin could quench the florescence of rBTI through the static quenching process. We also observed that upon binding to rutin or quercetin, rBTI underwent conformational changes. The results also suggested that rutin and quercetin bind to two different sites on rBTI through different interactions: rutin binds to rBTI through van der Waals forces and hydrogen bonds, whereas quercetin binds through hydrophobic interactions. Rutin and quercetin also markedly deactivated the trypsin inhibitory activity (TIA) of rBTI, while quercetin exhibited higher inactivation effect on rBTI than rutin due to its structure. Finally, the molecular docking revealed the molecular binding between the flavonoids and rBTI. These findings can be useful for the understanding of how flavonoid affects the inhibitory of rBTI.

Role of epigallocatechin gallate in collagen hydrogels modification based on physicochemical characterization and molecular docking

Collagen Type I derived from fish is mainly limited by its poor physicochemical properties for further applications. In this study, we developed epigallocatechin gallate (EGCG) cross-linked collagen hydrogels (EC hydrogels) to realize physicochemical improvements, basing on the interaction mechanism between collagen and EGCG. The integrity of collagen framework with slight secondary structure change in the presence of EGCG was confirmed. The stronger stability of collagen fibrils was proved by slower swelling ratio, declined enzymatic degradation, improved thermal analysis and mechanical test due to EGCG modification. To illustrate the potential mechanism between collagen and EGCG, molecular docking was used to identify both covalent (CN bond, between lysine of collagen and C₂-ring B of EGCG) and non-covalent bonds (hydrogen bond and hydrophobic interaction) within in EC hydrogel. Taken together, this work would offer some insights into the further study about the interaction between EGCG and collagen.

Formononetin/methyl-β-cyclodextrin inclusion complex incorporated into electrospun polyvinyl-alcohol nanofibers: Enhanced water solubility and oral fast-dissolving property

Improving solubility and administration route of isoflavone formononetin (FMN) are critical factors to improve its bioavailability in the oral cavity. This study fabricated fast-dissolving nanofibers containing FMN/methyl-β-cyclodextrin (FMN/Me-β-CD) inclusion complex. The solubility of FMN could be increased by approximately 50 times at 20 mM aqueous Me-β-CD. Interactions and thermodynamic parameters of the host-guest inclusion complex were studied by a fluorescence quenching method. The structure and mechanisms of the complex were further studied by molecular docking and molecular dynamics. Finally, polyvinyl-alcohol (PVA) nanofibrous webs containing the FMN/Me-β-CD inclusion complex were fabricated by electrospinning. The dissolution test demonstrated that the FMN/Me-β-CD/PVA nanofibers can be dissolved in artificial saliva within approximately 2 s. This study shows the potential of Me-β-CD inclusion and electrospinning to improve solubility and administration route of isoflavones.

Proteins from leguminous plants: from structure, property to the function in encapsulation/binding and delivery of bioactive compounds

Leguminous proteins are important nutritional components in leguminous plants, and they have different structures and functions depending on their sources. Due to their specific structures and physicochemical properties, leguminous proteins have received much attention in food and nutritional applications, and they can be applied as various carriers for binding/encapsulation and delivery of food bioactive compounds. In this review, we systematically summarize the different structures and functional properties of several leguminous proteins which can be classified as ferritin, trypsin inhibitor, β-conglycinin, glycinin, and various leguminous proteins isolates. Moreover, we review the development of leguminous proteins as carriers of food bioactive compounds, and emphasize the functions of leguminous protein-based binding/encapsulation and delivery in overcoming the low bioavailability, instability and low absorption efficiency of food bioactive compounds. The limitations and challenges of the utilization of leguminous proteins as carriers of food bioactive compounds are also discussed. Possible approaches to resolve the limitations of applying leguminous proteins such as instability of proteins and poor absorption of bioactive compounds are recommended.

Targeted inactivation of soybean proteinase inhibitors using zinc

In this study the potential targeted use of zinc to inactivate proteinase inhibitors (PI) has been investigated as an alternative to the widely applied heat treatment used industrially for inactivation of PI. Zinc was utilized for the reduction of disulfide bonds leading to the structural changes in proteins, thus affecting the decreased affinity between PI and proteinases. The protein disulfide bond reduction mechanism was studied using a newly developed micellar electrokinetic capillary chromatography (MECC) with the glutathione redox reaction with dithiothreitol (DTT) as model system. This model proved efficient in monitoring the reduction of disulfide bonds in the Kunitz trypsin inhibitor (KTI) and Bowman-Birk inhibitor (BBI). The use of zinc as a reductant resulted in a significant reduction of trypsin inhibitor activity (TIA) of 72% for KTI and 85% for BBI, highlighting zinc as a promising potential agent to reduce the activity of PI as an alternative to heat treatment.

Bowman-Birk Inhibitors: Insights into Family of Multifunctional Proteins and Peptides with Potential Therapeutical Applications

Bowman-Birk inhibitors (BBIs) are found primarily in seeds of legumes and in cereal grains. These canonical inhibitors share a highly conserved nine-amino acids binding loop motif CTP1SXPPXC (where P1 is the inhibitory active site, while X stands for various amino acids). They are natural controllers of plants' endogenous proteases, but they are also inhibitors of exogenous proteases present in microbials and insects. They are considered as plants' protective agents, as their elevated levels are observed during injury, presence of pathogens, or abiotic stress, i.a. Similar properties are observed for peptides isolated from amphibians' skin containing 11-amino acids disulfide-bridged loop CWTP1SXPPXPC. They are classified as Bowman-Birk like trypsin inhibitors (BBLTIs). These inhibitors are resistant to proteolysis and not toxic, and they are reported to be beneficial in the treatment of various pathological states. In this review, we summarize up-to-date research results regarding BBIs' and BBLTIs' inhibitory activity, immunomodulatory and anti-inflammatory activity, antimicrobial and insecticidal strength, as well as chemopreventive properties.

Characterization, antioxidant activities, and inhibition on α-glucosidase activity of corn silk polysaccharides obtained by different extraction methods

The polysaccharides (CSPw, CSPc, CSPa, and CSPu) were prepared by hot water extraction, acid-assisted extraction, alkaline-assisted extraction, and ultrasound-assisted extraction from corn silk, respectively. High performance gel permeation chromatography (HPGPC), fourier-transform infrared (FT-IR) spectroscopy, and scanning electron microscopy (SEM) results indicated that the extraction methods had an obvious impact on the molecular weight, structure, and morphology of the CSPs. Among the four polysaccharides, CSPu showed the highest inhibitory α-glucosidase activity, which might be related to its smaller molecular weight. Furthermore, kinetics analyses revealed that CSPu had significant inhibition of α-glucosidase in a non-reversible and competitive manner. Fluorescence quenching analysis illustrated that the interaction mechanism of CSPu and α-glucosidase was claimed as a static quenching mechanism. Isothermal titration calorimetry (ITC) analysis showed that the main driving forces for the interaction of CSPu with α-glucosidase was hydrogen bonding and the binding interactions of them occurred spontaneously.

Comparison of physicochemical properties of recombinant buckwheat trypsin inhibitor (rBTI) and soybean trypsin inhibitor (SBTI)

The inhibitory activities of buckwheat trypsin inhibitor (rBTI) towards trypsin were compared with soybean trypsin inhibitor (SBTI) in terms of their sensitivities to temperature, pH, salt ions and organic solvents. Both rBTI and SBTI were stable over a broad pH range of 2.0-12.0. rBTI exhibited higher thermal stability than SBTI. The inhibitory activity of rBTI was decreased by Zinc ions (Zn2+), KSCN, vitamin C and urea, while that of SBTI remained unchanged. However, H2O2, Mg2+ and Cu2+ ions had no significant effects on the inhibitory activities of rBTI and SBTI. Acetonitrile enhanced the inhibitory activity of rBTI, but had no effect on SBTI, while dimethylacetamide (DMAC) increased the inhibitory effect of both rBTI and SBTI. On the contrary, the inhibitory activities of rBTI and SBTI were reduced by isopropyl alcohol and methanol. The inhibition constants Ki of rBTI and SBTI were calculated to be 7.41 × 10-9 M and 6.52 × 10-9 M, respectively.