Apple phenolics as inhibitors of the carbonylation pathway during in vitro metal-catalyzed oxidation of myofibrillar proteins

Plant-based antioxidant peptides: impact on oxidative stress and gut microbiota

Plant-based peptides can be obtained from natural and climate-friendly sources. These peptides show various bioactivities including antioxidant activity. Oxidative stress has an impact on the gut microbiota causing inflammation, insulin resistance, osteoporosis, cancer, and several chronic diseases like type 2 diabetes, arthritis, hypertension, and atherosclerosis. Therefore, antioxidant peptides may significantly affect oxidative stress as a potential alternative to conventional medication. The production of antioxidant peptides from plant-based protein sources through conventional and innovative approaches may provide promising strategies to improve gut microbiota. Recent studies in plant-based antioxidant peptides (PBAP) focus on their advanced identification and characterization techniques, structure-activity relationship, improvement of extraction and purification, cellular and molecular mechanisms, specific health applications in preventing and managing conditions with gut microbiota, and commercial applications in nutraceuticals. Short-chain fatty acids and reactive sulfur species are specific gut-derived metabolites that can improve metabolic function by modulating oxidative stress and the immune system. This review highlights the influence of food oxidants on the gut microbiota and PBAP-induced modulation of gut microbiota. Moreover, the production of PBAP and the challenges in their application will be discussed.

Mechanistic Insights into Myofibrillar Protein Oxidation by Fenton Chemistry Regulated by Gallic Acid

Gallic acid (GA, 3,4,5-trihydroxybenzoic acid) is a widely used natural food additive of interest to food chemistry researchers, especially regarding its effects on myofibrillar protein (MP) oxidation. However, existing studies regarding MP oxidation by GA-combined with Fenton reagents are inconsistent, and the detailed mechanisms have not been fully elucidated. This work validated hydroxyl radical (HO·) as the primary oxidant for MP carbonylation; in addition, it revealed three functions of GA in the Fenton oxidation of MP. By coordination with Fe(III), GA reduces Fe(III) to generate Fe(II), which is the critical reagent for HO· generation; meanwhile, the coordination improves the availability and reactivity of Fe(III) under weakly acidic and near-neutral pH, i.e., pH 4-6. Second, the intermediates formed during GA oxidation, including semiquinone and quinone, promoted Fenton reactivity by accelerating Fe catalytic cycling. Finally, GA can scavenge HO· radicals, thus exhibiting a certain degree of antioxidant property. All three functions contribute to MP oxidation as observed in GA-containing meat.

The Effect of B-type Procyanidin on Free Radical and Metal Ion Induced β-Lactoglobulin Glyco-oxidation via Mass Spectrometry and Interaction Analysis

Procyanidin is a group of dietary flavonoids abundant in berry fruits. In this study, the effects and underlying mechanisms of B type procyanidin (PC) on free radical and metal ion (H₂O₂, AAPH and Fe³⁺) induced milk protein β-lactoglobulin (BLG) glyco-oxidation were investigated. The results indicated that PC protected BLG structure changes from cross-link and aggregation induced by free radicals and metal ion. Additionally, it effectively inhibited BLG oxidation by reducing approximately 21%-30% carbonyls and 15%-61% schiff base crosslink formation. Also, PC suppressed BLG glycation by inhibiting 48-70% advanced glycation end-products (AGEs) and reduced the accumulation of intermediate product methylglyoxal (MGO). The corresponding mechanisms were elucidated that PC exhibited great free radical scavenging and metal chelating properties; PC had non-covalent bind with the amino acid residues (preferably lysine and arginine) of BLG and blocked them from glycation; PC interrupted BLG glycation by forming procyanidin-MGO conjugates. Therefore, B type procyanidin was an effective glyco-oxidation inhibitor in milk products.

Potential implications of oxidative modification on dietary protein nutritional value: A review

During food processing and storage, proteins are sensitive to oxidative modification, changing the structural characteristics and functional properties. Recently, the impact of dietary protein oxidation on body health has drawn increasing attention. However, few reviews summarized and highlighted the impact of oxidative modification on the nutritional value of dietary proteins and related mechanisms. Therefore, this review seeks to give an updated discussion of the effects of oxidative modification on the structural characteristics and nutritional value of dietary proteins, and elucidate the interaction with gut microbiota, intestinal tissues, and organs. Additionally, the specific mechanisms related to pathological conditions are also characterized. Dietary protein oxidation during food processing and storage change protein structure, which further influences the in vitro digestion properties of proteins. In vivo research demonstrates that oxidized dietary proteins threaten body health via complicated pathways and affect the intestinal microenvironment via gut microbiota, metabolites, and intestinal morphology. This review highlights the influence of oxidative modification on the nutritional value of dietary proteins based on organs and the intestinal tract, and illustrates the necessity of appropriate experimental design for comprehensively exploring the health consequences of oxidized dietary proteins.

Effects of apple polyphenols and hydroxypropyl-β-cyclodextrin inclusion complexes on the oxidation of myofibrillar proteins and microstructures in lamb during frozen storage

This study aimed to evaluate the effect of inclusion complexes (ICs) on the oxidative stability of myofibrillar proteins (MPs) and microstructures in lamb during frozen storage. The inclusion process between apple polyphenols (APs) and hydroxypropyl-β-cyclodextrin (HP-β-CD) was verified using Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, and the antioxidant activity of APs. Results showed that the sensitivity of MPs to oxidation improved after 40 weeks. The ICs (0.2-1.6 mg/mL) significantly reduced the carbonyl content, particle size aggregation, protein degradation, fluorescence quenching effect, and decreased the α-helix contents loss of MPs. Additionally, the changes in protein oxidation showed a correlation with the microstructure of muscles, and the addition of 1.6 mg/mL IC remarkably improved the structure of muscle tissues while that of 3.2 mg/mL IC was detrimental to the structural properties. Overall, the exertion of antioxidant activity significantly influenced the cryoprotective effect of ICs on frozen lamb meat.

Critical overview of the use of plant antioxidants in the meat industry: Opportunities, innovative applications and future perspectives

The number of articles devoted to study the effect of "natural antioxidants" on meat systems has remarkably increased in the last 10 years. Yet, a critical review of literature reveals recurrent flaws in regards to the rationale of the application, the experimental design, the characterisation of the plant sources, the discussion of the molecular mechanisms and of the potential benefits. The selection of the appropriate source of these antioxidants and the identification of their bioactive constituents, are essential to understand their mode of action and set effective and safe doses. The methodological approach should also be planned with care as the recorded effects and main conclusions largely depend on the accuracy and specificity of the methods. This article aims to critically review the recent advances in the application of plant antioxidants in meat and meat products and briefly covers current trends of innovative application and future trends.

Allysine and α-Aminoadipic Acid as Markers of the Glyco-Oxidative Damage to Human Serum Albumin under Pathological Glucose Concentrations

Understanding the molecular basis of the disease is of the utmost scientific interest as it contributes to the development of targeted strategies of prevention, diagnosis, and therapy. Protein carbonylation is a typical feature of glyco-oxidative stress and takes place in health disorders such as diabetes. Allysine as well as its oxidation product, the α-amino adipic acid (α-AA) have been found to be markers of diabetes risk whereas little is known about the chemistry involved in its formation under hyperglycemic conditions. To provide insight into this issue, human serum albumin was incubated in the presence of FeCl3 (25 μM) and increasing glucose concentrations for 32 h at 37 °C. These concentrations were selected to simulate (i) physiological fasting plasma concentration (4 mM), (ii) pathological pre-diabetes fasting plasma concentration (8 mM), and pathological diabetes fasting plasma concentration (12 mM) of glucose. While both allysine and α-AA were found to increase with increasing glucose concentrations, the carboxylic acid was only detected at pathological glucose concentrations and appeared to be a more reliable indicator of glyco-oxidative stress. The underlying chemical mechanisms of lysine glycation as well as of the depletion of tryptophan and formation of fluorescent and colored advanced glycation products are discussed.

Influence of epicatechin on oxidation-induced physicochemical and digestibility changes in porcine myofibrillar proteins during refrigerated storage

BACKGROUND

The influence of epicatechin (EC) on the physicochemical properties and digestibility changes of porcine myofibrillar protein (MP) under oxidative stress during refrigerated storage was investigated.

RESULTS

The incubation of MP suspensions (20 mg mL^-1 in piperazine-N,N'-bis(2-ethanesulfonic acid) buffer, with 0.6 mol L^-1 sodium chloride, pH 6.25) at 4 °C for 24 h under an iron-catalyzed hydroxyl radical generating system (Fenton reaction) promoted the formation of thiobarbituric acid reactive substances and protein carbonyls, which was attenuated by EC (5, 50, and 100 μmol g^-1 protein). Reduced protein sulfhydryl content, tryptophan fluorescence, protein solubility, as well as increased surface hydrophobicity were found by the co-incubation of EC. Analysis by scanning electron microscopy revealed increased protein aggregation and fragments in oxidized MP, which were further enhanced by the addition of EC. However, the protein digestibility of MP was not affected.

CONCLUSION

EC was demonstrated to be effective in alleviating lipid oxidation and protein carbonylation in MP under oxidative stress. Additionally, the physicochemical and digestibility changes accompanying the incorporation of EC was complicated due to the possible phenol-protein interactions. An in-depth understanding of protein physicochemical and digestibility changes will be helpful in the application of polyphenolic compounds as antioxidants in low-temperature-processed muscle foods. © 2020 Society of Chemical Industry.

The Role of Meat Protein in Generation of Oxidative Stress and Pathophysiology of Metabolic Syndromes

Various processing methods have a great impact on the physiochemical and nutritional properties of meat that are of health concern. Hence, the postmortem processing of meat by different methods is likely to intensify the potential effects on protein oxidation. The influence of meat protein oxidation on the modulation of the systemic redox status and underlying mechanism is well known. However, the effects of processed meat proteins isolated from different sources on gut microbiota, oxidative stress biomarkers, and metabolomic markers associated with metabolic syndromes are of growing interest. The application of advanced methodological approaches based on OMICS, and mass spectrometric technologies has enabled to better understand the molecular basis of the effect of processed meat oxidation on human health and the aging process. Animal studies indicate the involvement of dietary proteins isolated from different sources on health disorders, which emphasizes the impact of processed meat protein on the richness of bacterial taxa such as (Mucispirillum, Oscillibacter), accompanied by increased expression of lipogenic genes. This review explores the most recent evidences on meat processing techniques, meat protein oxidation, underlying mechanisms, and their potential effects on nutritional value, gut microbiota composition and possible implications on human health.

Influence of sodium tripolyphosphate coupled with (−)-epigallocatechin on the in vitro digestibility and emulsion gel properties of myofibrillar protein under oxidative stress

This work demonstrates the effects of STP coupled with EGC on the formation of the MP emulsion gel under oxidative stress.

Collapse of the endogenous antioxidant enzymes in post-mortem broiler thigh muscles triggers oxidative stress and impairs water-holding capacity

This study was conducted to investigate the effect of the collapse of the endogenous antioxidant enzymes, namely, catalase (CAT), glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) in post-mortem (PM) chicken thigh muscles on the extent of lipid and protein oxidation and the functionality of the muscle in terms of water-holding. To fulfil this objective, the samples were divided into two treatments: one group of muscles (n = 8) was subjected to delay cooling (DC) (at ~ 37 °C for 200 min PM) and then stored at 4 °C for 24 h. The second group (n = 8) was subjected to a normal cooling (NC): samples were immediately chilled at 4 °C for 24 h. DC samples presented a decrease in 16% of CAT, 25% GSH-Px and 20% SOD activity in relation to NC. Consistently, an increase of 36% of total carbonyl, 15% of Schiff bases and 27% of TBA-RS and 14% of tryptophan depletion was observed in DC samples, as compared to NC. The results suggested that DC challenged muscles to struggle against oxidative reactions, consuming endogenous antioxidant defenses and causing protein and lipid oxidation which in turn affect the quality and safety of chicken meat. These results emphasize the role of PM oxidative stress on chicken quality and safety. Antioxidant strategies like fast cooling may be combined with others (dietary antioxidants) to preserve chicken quality against oxidative stress.

Practical use of natural antioxidants in meat products in the U.S.: A review

Historically, meat and poultry processors in the U.S. have relied on the use of synthetic antioxidants like butylated hydroxyanisole, butylated hydroxytoluene, tert-butylhydroquinone, and propyl gallate, as well as tocopherols to prevent lipid and protein oxidation. There is a trend towards utilizing natural antioxidants as replacements for synthetic ones. Some processors are already using multi-functional ingredients, such as rosemary and oregano, approved for use as spices and natural flavors to curb oxidation. Yet, there are still other ingredients that have not been applied in this fashion. Spices and natural flavors can often be incorporated in products that have defined statements of identity or composition. Further, these ingredients allow the processor to transition to a clean label without compromising the shelf life and quality of the products. Spices and natural flavors may have higher minimum effective concentrations than their synthetic counterparts, but they will offer increased consumer acceptability, decreased potential health risks, and can often achieve the same degree of oxidation prevention.

Unrestricted Mass Spectrometric Data Analysis for Identification, Localization, and Quantification of Oxidative Protein Modifications

Oxidation generates multiple diverse post-translational modifications resulting in changes in protein structure and function associated with a wide range of diseases. Of these modifications, carbonylations have often been used as hallmarks of oxidative damage. However, accumulating evidence supports the hypothesis that other oxidation products may be quantitatively more important under physiological conditions. To address this issue, we have developed a holistic mass spectrometry-based approach for the simultaneous identification, localization, and quantification of a broad range of oxidative modifications based on so-called "dependent peptides". The strategy involves unrestricted database searches with rigorous filtering focusing on oxidative modifications. The approach was applied to bovine serum albumin and human serum proteins subjected to metal ion-catalyzed oxidation, resulting in the identification of a wide range of different oxidative modifications. The most common modification in the oxidized samples is hydroxylation, but carbonylation, decarboxylation, and dihydroxylation are also abundant, while carbonylation showed the largest increase in abundance relative to nonoxidized samples. Site-specific localization of modified residues reveals several "oxidation hotspots" showing high levels of modification occupancy, including specific histidine, tryptophan, methionine, glutamate, and aspartate residues. The majority of the modifications, however, occur at low occupancy levels on a diversity of side chains.