Forming nanoconjugates or inducing macroaggregates, curcumin dose effect on myosin assembling revealed by molecular dynamics simulation

Synthesis and characterization of selenium nanoparticles stabilized by Grifola frondosa polysaccharides and gallic acid conjugates

Selenium nanoparticles (SeNPs) are of interest for their versatility and low toxicity, but bare SeNPs are unstable and tend to aggregate and precipitate as black elemental Se, which limits the application of SeNPs. This study evaluated the physicochemical properties, physical stability, antioxidant activities and cytotoxicity of SeNPs stabilized by Grifola frondosa polysaccharides (GFPs) and GFPs-gallic acid conjugates (GFPs-GA). The results showed that the particle size (PZ), polymer index (PDI) and zeta potential (ZP) of the GFPs-SeNPs and GFPs-GA-SeNPs were 58.72 ± 0.53 nm, 0.11, -8.36 ± 0.21 mV and 61.80 ± 0.16 nm, 0.12, -9.37 ± 0.13 mV, respectively. Besides, the GFPs-SeNPs and GFPs-GA-SeNPs remained stable when stored at 4 °C for 70 days in darkness. SeNPs stabilized with GFPs have improved the antioxidant activity and selective toxicity to tumour cells. Interestingly, SeNPs stabilized with GFPs-GA further enhanced these biological activities. This work provided a simple and effective method to construct well-dispersed SeNPs in aqueous systems, demonstrating the important roles of GFPs and GFPs-GA in the size control, dispersion and stabilization of SeNPs. The prepared GFPs-SeNPs and GFPs-GA-SeNPs can serve as good selenium supplements and have potential prospects for antioxidant activity and tumour inhibition.

Polyphenol oxidase mediates (-)-epigallocatechin gallate to inhibit endogenous cathepsin activity in Apostichopus japonicus

Apostichopus japonicus (A. japonicus) has rich nutritional value and is an important economic crop. Due to its rich endogenous enzyme system, fresh A. japonicus is prone to autolysis during market circulation and storage, resulting in economic losses. In order to alleviate this phenomenon, we investigated the effect of polyphenol oxidase (PPO) mediated (-)-epigallocatechin gallate (EGCG) on the activity and structure of endogenous cathepsin series protein (CEP) from A. japonicus. Research on cathepsin activity showed that PPO mediated EGCG could significantly reduce enzyme activity, resulting in a decrease in enzymatic reaction rate. SDS-PAGE and scanning electron microscopy results showed that PPO mediates EGCG could induce CEP aggregation to form protein aggregates. Various spectral results indicated that EGCG caused changes in the structure of CEP. Meanwhile, the conjugates formed by PPO mediated EGCG had lower thermal stability. In conclusion, PPO mediated EGCG was an effective method to inhibit the endogenous enzyme activity.

Stability protection of lutein emulsions by utilizing a functional conjugate of collagen and Lycium barbarum L. leaf flavonoid

Lutein exhibits excellent functional activity making it useful in many fields. Nevertheless, its use is limited by its physical and chemical instability. Here, collagen and Lycium barbarum L. leaf flavonoids (LBLF) were used as emulsifiers, their structures were characterized, the properties of the complexes were evaluated, and their stabilizing effects on lutein emulsions were explored. According to the results, the encapsulation rate of the complex of collagen-LBLF was (68.67 ± 1.43) % and the drug loading was (6.92 ± 0.13) %. Collagen compounded LBLF with a changed structure and morphology, resulting in improved antioxidant capacity, better foaming and emulsification, and reduced hydrophobicity. In addition, the thiobarbituric acid value of collagen-LBLF stabilized lutein emulsion (0.0012 ± 0.00011) mg/kg was significantly lower than that of collagen stabilized lutein emulsion (0.0021 ± 0.00016)  mg/kg (P < 0.05), indicating that the composite stabilized lutein emulsion obtained higher stability. LBLF contributed a high free radical scavenging effect and inhibited lutein degradation during storage. During simulated digestion, collagen-LBLF effectively stabilized the emulsion and protected lutein from destruction, made it release more slowly, and benefited the bio-accessibility of lutein during the next utilization step. Based on the present study, improved storage and digestion stabilities of lutein wereachievedby the utilization of collagen-LBLF complex, which provides a new method for the preparation and application of composite functional emulsifiers.

Research advances of molecular docking and molecular dynamic simulation in recognizing interaction between muscle proteins and exogenous additives

During storage and processing, muscle proteins, e.g. myosin and myoglobin, will inevitably undergo degeneration, which is thus accompanied by quality deterioration of muscle foods. Some exogenous additives have been widely used to interact with muscle proteins to stabilize the quality of muscle foods. Molecular docking and molecular dynamics simulation (MDS) are regarded as promising tools for recognizing dynamic molecular information at atomic level. Molecular docking and MDS can explore chemical bonds, specific binding sites, spatial structure changes, and binding energy between additives and muscle proteins. Development and workflow of molecular docking and MDS are systematically summarized in this review. Roles of molecular simulations are, for the first time, comprehensively discussed in recognizing the interaction details between muscle proteins and exogenous additives aimed for stabilizing color, texture, flavor, and other properties of muscle foods. Finally, research directions of molecular docking and MDS for improving the qualities of muscle foods are discussed.

Effect of Capsaicin and Dihydrocapsaicin in Capsicum on Myofibrillar Protein in Duck Meat

Spice and its extracts have gained widespread utilization as natural and eco-friendly additives, imparting enhancements in flavor, color, and antioxidative attributes to meat-based products. This work aims to study the effect mechanism of capsaicin (CA) and dihydrocapsaicin (DI) in capsicum (chili pepper) on the structure and function of myofibrillar proteins (MPs) in duck meat during thermal treatment. The results showed that at a CA-DI to MP ratio of 1:500 (g/g) following a 12 min heat treatment, the carbonyl content of MPs in duck meat decreased by 48.30%, and the sulfhydryl content increased by 53.42%. When the concentration was 1:500 (CA-DI, g/g) after 24 min of heat treatment, the •OH and DPPH radical scavenging rates were highest at 59.5% and 94.0%, respectively. And the initial denaturation temperature of MPs was the highest at 96.62 °C, and the thermal absorption was lowest at 200.24 J g-1. At the parameter, the smallest particle size and size distribution range of MP were 190 nm (9.51%). Furthermore, the interplay between CA-DI and MPs contributed to a reduction in the protein particle size and intrinsic fluorescence. In summary, the combination of CA-DI and MPs played a crucial role in inducing protein unfolding and disintegration.

Fabrication of glycated yeast cell protein via Maillard reaction for delivery of curcumin: improved environmental stability, antioxidant activity, and bioaccessibility

BACKGROUND

The application of curcumin (CUR) in the food industry is limited by its instability, hydrophobicity and low bioavailability. Yeast cell protein (YCP) is a by-product of spent brewer's yeast, which has the potential to deliver bioactive substances. However, the environmental stresses such as pH, salt and heat treatment has restricted its application in the food industry. Maillard reaction as a non-enzymatic browning reaction can improve protein stability under environmental stress.

RESULTS

The CUR was successfully encapsulated into the hydrophobic core of YCP/glycated YCP (GYCP) and enhanced by hydrogen bonding, resulting in static fluorescence quenching of YCP/GYCP. The average diameter and dispersibility of GYPC-CUR nanocomplex were significantly improved after glucose glycation (121.40 nm versus 139.70 nm). Moreover, the encapsulation capacity of CUR was not influenced by glucose glycation. The oxidative stability and bioaccessibility of CUR in nanocomplexes were increased compared with free CUR, especially complexed with GYCP conjugates.

CONCLUSION

Steric hindrance provided by glucose conjugation improved the enviriomental stability, oxidative activity and bioaccessibility of CUR in nanocomplexes. Thus, glucose-glycated YCP has potential application as a delivery carrier for hydrophobic compounds in functional foods. © 2022 Society of Chemical Industry.

Geotrichum candidum arthrospore cell wall particles as a novel carrier for curcumin encapsulation

We report for the first time that curcumin is successfully encapsulated into a new natural pre-formed carrier, which was derived from arthrospore cell wall particles (APs) of probiotic Geotrichum candidum LG-8 and mainly composed of beta-1,4-glucan. Vacuum infusion process was used for efficient encapsulation of curcumin. The results showed that the encapsulation efficiency and yield of APs were 36.5 ± 0.9 % and 730.6 ± 26.5 μg/g (wet basis), respectively. Compared with the other probiotic carriers such as Saccharomyces cerevisiae, it could more effectively maintain the antioxidant property and storage capacity of curcumin under high temperature conditions. Simulated digestion was conducted to study in vitro release of curcumin encapsulated in APs, and showed a maximum bioaccessibility of 65.6 ± 3.8 %. In view of low-cost culture method, simple encapsulation process and high encapsulation capacity, G. candidum arthrospores as new natural encapsulation carriers have potential superiority in the practical application in food industry.

Hydrophobic bonds-dominated key off-odors/silver carp myofibrillar protein interactions, and their binding characteristics at cold storage and oral temperatures

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Off-odors binding to MP via hydrophobic forces is a spontaneous process.

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Nonanal had the strongest binding ability to MP among the three off-odors.

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MD method provided a structural basis for the fluorescence spectroscopic analysis.

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Three off-odors, especially nonanal, could change the conformation of MP.

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Compared with others, nonanal formed more binding sites to Trp residues in Myosin1.

This study revealed the interaction mechanism between silver carp myofibrillar protein (MP) and key off-odors by combining fluorescence spectroscopy with molecular dynamics (MD) simulation. Spectroscopic results exhibited a dynamic quenching mechanism between MP and off-odors. Thermodynamic analysis indicated that the MP/off-odors interaction was spontaneous (ΔG° < 0) and dominated by hydrophobic interactions (ΔH° > 0, ΔS° > 0). Meanwhile, the binding affinity was in the order of nonanal (n = 1.38) > hexanal (n = 0.89) > 1-octen-3-ol (n = 0.65), which was further verified by the MD results. Among off-odors, nonanal had the highest binding energy with myosin (8105.66 kJ/mol) and formed more hydrophobic binding sites to Trp residues in myosin head (e.g., Trp820 and Trp822), thereby changing myosin conformations via both physical and chemical interactions. Additionally, higher binding energies of myosin/off-odors were observed at oral temperature (37 °C) than at cold storage temperature (4 °C), implying that less off-odors were released at 37 °C.