Alcalase-hydrolyzed oyster (Crassostrea rivularis) meat enhances antioxidant and aphrodisiac activities in normal male mice

Preparation of oyster peptide and Pfaffia glomerata pressed candy and its ameliorative effect on sexual dysfunction in male mice

Oyster peptide (OP) and Pfaffia glomerata extract (PGE) were used as raw materials. The optimal formulation of the pressed candy (PC) was optimized by one-way experiment and D-optimal mixture experiment design, and animal experiment was used to evaluate the effect of PC on male sexual dysfunction. The results showed that PC intervention significantly improved the sexual behavior of male mice with sexual dysfunction, including a significant shortening of the mount latency (ML) and intromission latency, and a significant increase in the mount frequency (MF) and intromission frequency (IF). At the same time, the concentrations of serum testosterone (T) and luteinizing hormone (LH) in mice were restored, and the erectile parameters and pathological changes of penile tissue were improved. Further studies found that PC intervention increased the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) and reduced the content of malondialdehyde (MDA) in testicular tissue. In addition, PC intervention improved testicular tissue morphology. In conclusion, the obtained PC has good taste quality, and the relevant quality indicators are qualified. It has a good ameliorative effect on male sexual dysfunction and may be a potential dietary supplement.

Crassostrea gigas peptide PEP-1 prevents tert-butyl hydroperoxide (t-BHP) induced oxidative stress in HepG2 cells

Exposure to tert-butyl hydroperoxide (t-BHP) leads to cytotoxicity and oxidative stress in various organs and cell types. The bioactive peptides extracted from Oysters exhibit marked antioxidant activity. The impacts of Crassostrea gigas peptides on t-BHP-triggered oxidative stress remain largely unknown. The protective and antioxidant activity of a C.gigas peptide, PEP-1, on t-BHP-treated HepG2 cells, was investigated. PEP-1, this peptide is arginine kinase in oysters. This enzyme functions as a catalyst for the chemical reaction and serves as a phosphate transferase. Since it was the most expressed protein in the adductor muscle of oysters. Our determination showed the lowest level of a toxic concentration of t-BHP (200 µM) and the resting concentration of PEP-1 (0-1000 ng/ml). PEP-1 exerted a protective effect against t-BHP-induced apoptosis by modifying the expression of pro-and anti-apoptotic proteins. PEP-1 administration reduced nitric oxide and ROS levels while restoring levels of antioxidant proteins in t-BHP-induced cells. PEP-1 exhibited the capacity to enhance the translocation of nuclear factor erythroid 2-related factor 2 (Nrf2). Therefore, the C. gigas peptide PEP-1 has demonstrated its ability to protect HepG2 cells against oxidative stress induced by t-BHP.

Oyster Peptide-Zinc Complex Ameliorates Di-(2-ethylhexyl) Phthalate-Induced Testis Injury in Male Mice and Improving Gut Microbiota

Di-(2-ethylhexyl) phthalate (DEHP) is a widely used plasticizer, which can cause damage to male reproductive organs, especially the atrophy of the testis. Meanwhile, DEHP can also lead to a decrease in testicular zinc content, but the role of zinc remains unclear. This study aims to prepare oyster peptide-zinc complex (OPZC) to alleviate DEHP-induced reproductive damage in mice. OPZC was successfully obtained through electron microscopy, X-ray diffraction, and thermogravimetric analysis, with stable structure and high water-solubility. Low dose oyster peptide-zinc complex (OPZCL) significantly reduced the reproductive damage caused by DEHP in mice. Further research had shown that OPZCL restored the content of serum hormones and the activity of oxidative stress kinases to normal, while also normalizing testicular zinc and selenium levels. In addition, it also recovered the disorder of gut microbiota, reduced the proportion of Bacteroides, increased the abundance of Ligilactobacillus, and restored the proportion of Acidobacteriota, Chloroflexi, and Proteobacteria. Therefore, OPZCL can relieve the reproductive damage caused by DEHP in mice by restoring testicular zinc homeostasis and the composition of intestinal microbiota, indicating that OPZCL has a potential protective effect on male reproductive health.

Structural modification of poppy-pollen protein as a natural antioxidant, emulsifier and carrier in spray-drying of O/W-emulsion: Physicochemical and oxidative stabilization

This study was aimed to investigate the efficiency of poppy-pollen (PP) protein and peptides as carrier for spray-drying encapsulation of grape-seed oil (GSO). The composition of amino acids, functional properties and bioactivity (scavenging of DPPH, ABTS, OH, and nitric-oxide radicals, reducing power, total antioxidant, TBARS levels in O/W-emulsion, and chelation of Fe2+ and Cu2+ ions) of PP-protein were affected by the enzymolysis time. Partial enzymolysis (30 min) led to improved solubility, protein surface activity and increased physical stability of GSO/W emulsion (relative to creaming, aggregation and flocculation) during storage. Also, spray-dried emulsions with this type of carrier (H-30) had the highest production yield (~67 %), solubility (~92 %), flowability, encapsulation efficiency (~96 %), reconstitution ability (least size and EE changes), physical and oxidative stability. The evaluation of the chemical structures (FTIR) indicated the formation of hydrogen bonds between the cis-alkene groups of fatty acids and the hydroxyl groups of the amide A and B regions, as well as the trapping of oil in the carrier matrix. SEM images illustrated the effect of native protein carriers (particles with smooth, dents, and hollow surfaces with surface pores), partially (wrinkled and reservoir-type), and strongly (irregular structures, sticky and amorphous agglomerates) hydrolyzed peptides on the morphology of oily-particles. The results of this research indicate the usability of partially hydrolyzed poppy-pollen protein as a source of natural antioxidant, emulsifier, and carrier in the production, stabilization, and encapsulation of oxidation-sensitive bioactive components and emulsions.

Influence of the Degree of Hydrolysis on Functional Properties and Antioxidant Activity of Enzymatic Soybean Protein Hydrolysates

Soybean protein hydrolysates were prepared using two proteolytic enzymes (Alcalase and Protamex) and the degree of hydrolysis (DH) and their functional and antioxidant properties were evaluated. The highest DH value was 20%, with a yield of 19.77% and protein content of 51.64%. The total amino acid content was more than 41% for all protein hydrolysates. The protein hydrolysates from Protamex at pH 2.0 had excellent solubility, emulsifying activity, and foaming capacity, at 83.83%, 95.03 m²/g, and 93.84%, respectively. The water-holding capacity was 4.52 g/g for Alcalase, and the oil-holding capacity was 4.91 g/g for Protamex. The antioxidant activity (62.07%), as measured by the samples' reaction with DPPH (2,2-diphenyl-1-picrylhydrazyl) and the reducing power (0.27) were the strongest for Protamex. An ABTS activity rate of 70.21% was recorded for Alcalase. These findings indicated a strong potential for the utilization of soybean protein hydrolysates to improve the functional properties and antioxidant activity of soybeans as well as their nutritional values.

Extraction and Characterization of Protein Concentrates from Limpets (Patella vulgata) and Peptide Release Following Gastrointestinal Digestion

This study investigated the characterization of proteins from the Irish limpet (Patella vulgata) and assessed the in vitro biological activities of hydrolysates obtained following gastrointestinal digestion (INFOGEST) of a limpet protein concentrate (LPC). The physicochemical properties and the digestibility of the LPC were investigated, along with the angiotensin-converting enzyme (ACE) inhibition and antioxidant activities of the LPC-digested samples. All the digested samples examined outperformed the LPC in terms of activity. Peptides were identified using LC-MS/MS after digestion. A total of 38 and 19 peptides were identified in LPC-G and LPC-GI, respectively, using a database search and a de novo approach. Most of the identified peptides had hydrophobic amino acids, which may contribute to their antioxidant and ACE inhibitory activities. The findings of this study showed that LPC has high nutritional quality with good digestibility and could serve as a potential source of antioxidative and ACE inhibitory peptides following gastrointestinal digestion.

Hybridising plasma functionalized water and ultrasound pretreatment for enzymatic protein hydrolysis of Larimichthys polyactis: Parametric screening and optimization

Hybridising plasma functionalized water and ultrasound pretreatment for the enzymatic hydrolysis (HPUEH) of Larimichthys polyactis was evaluated by adopting Plackett-Burman design for parametric screening of six key variables, and Box-Behnken design for optimizing three most significant variables including plasma generating voltage (P_V), ultrasound treatment time (U_T), and enzyme concentration (E_C). The models developed for predicting the degree of hydrolysis (DoH), protein recovery (PVY), and soluble protein content (SPC) were sufficiently fitted to the experimental data (R² ≥ 0.966) with non-significant lack of fit and used for determining the optimum conditions as P_V of 70 V, U_T of 15 min, and E_C of 1.787%, with predictive values of 27.74%, 85.62%, and 3.28 mg/mL for DoH, PVY, and SPC, respectively. HPUEH presented hydrolysates with smaller peptide sizes and molecular weights, enhanced DoH, PVY, SPC, amino acids and antioxidant activity, but reduced emulsifying and foaming properties when compared with conventional enzymatic hydrolysis.

Hepatoprotective Effect of Oyster Peptide on Alcohol-Induced Liver Disease in Mice

Alcohol-induced liver disease (ALD) has become one of the major global health problems, and the aim of this study was to investigate the characterization of the structure as well as the hepatoprotective effect and mechanism of oyster peptide (OP, MW < 3500 Da) on ALD in a mouse model. The results demonstrate that ethanol administration could increase the activities of aspartate aminotransferase (AST), alanine transaminase (ALT), γ-Glutamyl transferase (GGT), reactive oxygen species (ROS), malondialdehyde (MDA), and triglycerides (TG), as well as increase the interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor (TNF-α) levels (p < 0.01), and reduce the activity of superoxide dismutase (SOD) and the concentration of glutathione (GSH). Those changes were significantly reversed by the application of different doses of OP. Furthermore, the mRNA expressions of nuclear factor elythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), and quinone oxidoreductase1 (NQO1) were significantly up-regulated in OP groups, and the mRNA expressions of nuclear factor kappa-light chain enhancer of B cells (NF-κB), TNF-α, and IL-6 were markedly reduced in OP groups compared to that of the model group. Thus, OP had a significant protective effect on ALD through the enhancement of the in vivo antioxidant ability and the inhibition of the inflammatory response as possible mechanisms of action, which therefore suggests that OP might be useful as a natural source to protect the liver from alcohol damage.

A Review of Bioactive Compounds in Oyster Shell and Tissues

Oysters are saltwater bivalves with high nutritional and medicinal value that are consumed widely around the world. As well as being highly nutritious, oysters are a low-calorie, low-cholesterol source of protein and an exceptional source of zinc, which strengthens the immune system; and a rich source of bioactive compounds, which comprise various biological activities. The present review summarizes the biological applications and bioactive compounds from oyster shells, whole tissue, gill tissue, and mantle tissue. The various biological compounds present in an oyster shell, and their chemical constituents, have applications in the food, pharmaceutical, and medical industries. Bioactive peptides and proteins obtained from the whole, mantle, and gill tissues of oysters exhibit antioxidant, antimicrobial, antihypertensive, anticancer, antifatigue, anticoagulant, and anti-wrinkle effects, as well as enhance osteoblast differentiation. This review clearly shows that oysters have great potential for functional food production and that various compounds therein can have pharmaceutical applications.

Exploration of bioactive peptides from various origin as promising nutraceutical treasures: In vitro, in silico and in vivo studies

The current health scenarios describe growing public health problems, such as diabetes, hypertension and cancer. Therefore, researchers focused on studying these health issues are interested in exploring bioactive compounds from different food sources. Among them, bioactive peptides have garnered huge scientific interest because of their multifunctional biological activities such as antioxidative, antimicrobial, antihypertensive, anticancer, antidiabetic, immunomodulatory effect. They can be used as food and pharmaceutical ingredients with a great potential against disease targets. This review covers methods of production in general for several peptides obtained from various food sources including seed, milk and meat, and described their biological activities. Particular focus was given to bioinformatic tools to advance quantification, detection and characterize each peptide sequence obtained from different protein sources with predicted biological activity. Besides, various in vivo studies have been discussed to provide a better understanding of their physiological functions, which altogether could provide valuable information for their commercialization in future foods.

Marine Products As a Promising Resource of Bioactive Peptides: Update of Extraction Strategies and Their Physiological Regulatory Effects

Marine products are a rich source of nutritional components and play important roles in promoting human health. Fish, mollusks, shellfish, as well as seaweeds are the major components of marine products with high-quality proteins. During the last several decades, bioactive peptides from marine products have gained much attention due to their diverse biological properties including antioxidant, antihypertensive, antimicrobial, antidiabetic, immunoregulation, and antifatigue. The structural characteristics of marine bioactive peptides largely determine the differences in signaling pathways that can be involved, which is also an internal mechanism to exert various physiological regulatory activities. In addition, the marine bioactive peptides may be used as ingredients in food or nutritional supplements with the function of treating or alleviating chronic diseases. This review presents an update of marine bioactive peptides with the highlights on the novel producing technologies, the physiological effects, as well as their regulation mechanisms. Challenges and problems are also discussed in this review to provide some potential directions for future research.

Optimization of Enzymatic Hydrolysis of Perilla Meal Protein for Hydrolysate with High Hydrolysis Degree and Antioxidant Activity

Botanical oils are staple consumer goods globally, but as a by-product of oil crops, meal is of low utilization value and prone to causing environmental problems. The development of proteins in meal into bioactive peptides, such as Perilla peptide, through biotechnology can not only solve environmental problems, but also create more valuable nutritional additives. In the present work, the hydrolysis process of Perilla meal protein suitable for industrial application was optimized with the response surface methodology (RSM) on the basis of single-factor experiments. Alcalase was firstly selected as the best-performing among four proteases. Then, based on Alcalase, the optimal hydrolysis conditions were as follows: enzyme concentration of 7%, hydrolysis temperature of 61.4 °C, liquid-solid ratio of 22.33:1 (mL/g) and hydrolysis time of 4 h. Under these conditions, the degree of hydrolysis (DH) of Perilla meal protein was 26.23 ± 0.83% and the DPPH scavenging capacity of hydrolysate was 94.15 ± 1.12%. The soluble peptide or protein concentration of Perilla meal protein hydrolysate rose up to 5.24 ± 0.05 mg/mL, the ideal yield of which was estimated to be 17.9%. SDS-PAGE indicated that a large proportion of new bands in hydrolysate with small molecular weights appeared, which was different from the original Perilla meal protein. The present data contributed to further, more specific research on the separation, purification and identification of antioxidant peptide from the hydrolysate of Perilla meal protein. The results showed that the hydrolysis of Perilla meal protein could yield peptides with high antioxidant activity and potential applications as natural antioxidants in the food industry.

Food-Derived High Arginine Peptides Promote Spermatogenesis Recovery in Busulfan Treated Mice

Food-derived peptides with high arginine content have important applications in medicine and food industries, but their potential application in the treatment of oligoasthenospermia remains elusive. Here, we report that high-arginine peptides, such as Oyster peptides and Perilla purple peptides were able to promote spermatogenesis recovery in busulfan-treated mice. We found that both Opp and Ppp could increase sperm concentration and motility after busulfan-induced testicular damage in mice. Further research revealed that Opp and Ppp might promote spermatogonia proliferation, which improved blood-testis barrier recovery between Sertoli cells. Taken together, these high-arginine peptides might be used as a medication or therapeutic component of a diet prescription to improve the fertility of some oligoasthenospermia patients.

In vitro Antioxidant, Cytotoxic and Antidiabetic Activities of Protein Hydrolysates Prepared from Chinese Pond Turtle (Chinemys reevesii)

Research background

Cardiovascular diseases and diabetes are the biggest causes of death globally. Bioactive peptides derived from many food proteins using enzymatic proteolysis and food processing have a positive impact on the prevention of these diseases. The bioactivity of Chinese pond turtle muscle proteins and their enzymatic hydrolysates has not received much attention, thus this study aims to investigate their antioxidant, antidiabetic and cytotoxic activities.

Experimental approach

Chinese pond turtle muscles were hydrolysed using four proteolytic enzymes (Alcalase, Flavourzyme, trypsin and bromelain) and the degrees of hydrolysis were measured. High-performance liquid chromatography (HPLC) was conducted to explore the amino acid profiles and molecular mass distribution of the hydrolysates. The antioxidant activities were evaluated using various in vitro tests, including 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), hydroxyl radical scavenging activity, reducing capacity, chelating Fe²⁺ and lipid peroxide inhibition activity. Antidiabetic activity was evaluated using α-amylase inhibition and α-glucosidase inhibition assays. Besides, cytotoxic effect of hydrolysates on human colon cancer (HT-29) cells was assessed.

Results and conclusions

The amino acid composition of the hydrolysates revealed higher mass fractions of glutamic, aspartic, lysine, hydroxyproline and hydrophobic amino acids. Significantly highest inhibition of lipid peroxidation was achieved when hydrolysate obtained with Alcalase was used. Protein hydrolysate produced with Flavourzyme had the highest radical scavenging activity measured by DPPH (68.32%), ABTS (74.12%) and FRAP (A_{700 nm}=0.300) assays, α-glucosidase (61.80%) inhibition and cytotoxic effect (82.26%) on HT-29 cell line at 550 µg/mL. Hydrolysates obtained with trypsin and bromelain had significantly highest (p<0.05) hydroxyl radical scavenging (92.70%) and Fe²⁺ metal chelating (63.29%) activities, respectively. The highest α-amylase (76.89%) inhibition was recorded when using hydrolysates obtained with bromelain and Flavourzyme.

Novelty and scientific contribution

Enzymatic hydrolysates of Chinese pond turtle muscle protein had high antioxidant, cytotoxic and antidiabetic activities. The findings of this study indicated that the bioactive hydrolysates or peptides from Chinese pond turtle muscle protein can be potential ingredients in pharmaceuticals and functional food formulations.

No time to die: An in-depth analysis of James Bond's exposure to infectious agents

Global travelers, whether tourists or secret agents, are exposed to a smörgåsbord of infectious agents. We hypothesized that agents pre-occupied with espionage and counterterrorism may, at their peril, fail to correctly prioritize travel medicine. To examine our hypothesis, we examined adherence to international travel advice during the 86 international journeys that James Bond was observed to undertake in feature films spanning 1962-2021. Scrutinizing these missions involved ∼3113 min of evening hours per author that could easily have been spent on more pressing societal issues. We uncovered above-average sexual activity, often without sufficient time for an exchange of sexual history, with a remarkably high mortality among Bond's sexual partners (27.1; 95% confidence interval 16.4-40.3). Given how inopportune a bout of diarrhea would be in the midst of world-saving action, it is striking that Bond is seen washing his hands on only two occasions, despite numerous exposures to foodborne pathogens. We hypothesize that his foolhardy courage, sometimes purposefully eliciting life-threatening situations, might even be a consequence of Toxoplasmosis. Bond's approach to vector-borne diseases and neglected tropical diseases is erratic, sometimes following travel advice to the letter, but more often dwelling on the side of complete ignorance. Given the limited time Bond receives to prepare for missions, we urgently ask his employer MI6 to take its responsibility seriously. We only live once.

Antioxidant Mechanisms of the Oligopeptides (FWKVV and FMPLH) from Muscle Hydrolysate of Miiuy Croaker against Oxidative Damage of HUVECs

In this work, the antioxidant mechanisms of bioactive oligopeptides (FWKVV and FMPLH) from protein hydrolysate of miiuy croaker muscle against H₂O₂-damaged human umbilical vein endothelial cells (HUVECs) were researched systemically. The finding demonstrated that the HUVEC viability treated with ten antioxidant peptides (M1 to M10) at 100.0 μM for 24 h was not significantly affected compared with that of the normal group (P < 0.05). Furthermore, FWKVV and FMPLH at 100.0 μM could very significantly enhance the viabilities (75.89 ± 1.79% and 70.03 ± 4.37%) of oxidative-damaged HUVECs by H₂O₂ compared with those of the model group (51.66 ± 2.48%) (P < 0.001). The results indicated that FWKVV and FMPLH played their protective functions through increasing the levels of antioxidant enzymes including superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) and decreasing the levels of reactive oxygen species (ROS), malondialdehyde (MDA), and nitric oxide (NO) in oxidative-damaged HUVECs in a dose-dependent manner. In addition, the comet assay revealed that FWKVV and FMPLH could dose-dependently protect deoxyribonucleic acid (DNA) from oxidative damage in the HUVEC model. These results suggested that antioxidant pentapeptides (FWKVV and FMPLH) could serve as potential antioxidant additives applied in the food products, pharmaceuticals, and health supplements.

Bioactive peptides from foods: production, function, and application

Bioactive peptides are a class of peptides with special physiological functions and have potential applications in human health and disease prevention. Bioactive peptides have gained much research attention because they affect the cardiovascular, endocrine, immune, and nervous systems. Recent research has reported that bioactive peptides are of great value for physiological function regulation, including antioxidation, anti-hypertension, antithrombosis, antibacterial properties, anti-cancer, anti-inflammation, anti-diabetic, anti-obesity, cholesterol-lowering, immunoregulation, mineral binding and opioid activities. The production of food-derived bioactive peptides is mainly through the hydrolysis of digestive enzymes and proteolytic enzymes or microbial fermentation. The purpose of this review is to introduce the production, function, application, challenges, and prospects of food-derived bioactive peptides.

Impact of air-frying on the plasmalogens deterioration and oxidation in oyster revealed by mild acid hydrolysis and HILIC-MS-based lipidomics analysis

Oyster is rich in plasmalogens that are ether phospholipids with biological functions to human body. Air-frying is a popular technique for preparing delicious oyster but makes the plasmalogens vulnerable to oxidation. In this study, the effect of air-frying processing on plasmalogens oxidation was studied by lipidomic approach. Plasmalogens were always mixed with normal phospholipids, thus the lipid extract was treated with mild acid hydrolysis to rapidly degrade plasmalogens owing to the acid lability of vinyl ether linkage at sn-1 position. After hydrophilic interaction chromatography MS/MS analysis, there were three plasmalogen classes, plasmanylcholine, plasmanylethanolamine, and plasmanylinositol, completely separated, and each plasmalogen molecular species was identified and quantified. It indicated that the content of plasmalogens underwent an obvious decrease during the air-frying process. To weaken such effect, the influence of air-frying temperature was further inspected by multivariate statistical analyses. The main variables, including the ions of m/z 756.4927, 784.5486, 828.5812, etc., were revealed by unsupervised principle component analysis, supervised orthogonal partial least-square analysis, and variable importance in projection plot. As a conclusion, air-frying has health benefits in reducing fat content but destructive to plasmalogens, thus interventions are recommended to prevent the degradation of plasmalogens.

Roles of Dietary Bioactive Peptides in Redox Balance and Metabolic Disorders

Bioactive peptides (BPs) are fragments of 2-15 amino acid residues with biological properties. Dietary BPs derived from milk, egg, fish, soybean, corn, rice, quinoa, wheat, oat, potato, common bean, spirulina, and mussel are reported to possess beneficial effects on redox balance and metabolic disorders (obesity, diabetes, hypertension, and inflammatory bowel diseases (IBD)). Peptide length, sequence, and composition significantly affected the bioactive properties of dietary BPs. Numerous studies have demonstrated that various dietary protein-derived BPs exhibited biological activities through the modulation of various molecular mechanisms and signaling pathways, including Kelch-like ECH-associated protein 1/nuclear factor erythroid 2-related factor 2/antioxidant response element in oxidative stress; peroxisome proliferator-activated-γ, CCAAT/enhancer-binding protein-α, and sterol regulatory element binding protein 1 in obesity; insulin receptor substrate-1/phosphatidylinositol 3-kinase/protein kinase B and AMP-activated protein kinase in diabetes; angiotensin-converting enzyme inhibition in hypertension; and mitogen-activated protein kinase and nuclear factor-kappa B in IBD. This review focuses on the action of molecular mechanisms of dietary BPs and provides novel insights in the maintenance of redox balance and metabolic diseases of human.

Structural characterization and functional properties of CNPP, a byproduct formed during CPP preparation

Casein nonphosphopeptide (CNPP), a byproduct formed during the preparation of casein phosphopeptide (CPP), is often discarded on a large scale. Although our previous studies have demonstrated the ameliorative effect of CNPP on muscle wasting disorders, its structure-function mechanism is still unclear. Therefore, considering the great influence of structural characteristics on function, this study aims to explain the potential mechanism by characterizing the physicochemical and functional properties of CNPP. The results of structural characterization indicated that CNPP was of low molecular weight and composed of the complete range of amino acids; it was particularly rich in leucine. Compared with casein, CNPP had a lower molecular size and total/free sulfhydryl content (reduced 2.44 and 2.02 µmol/g in CNPP, respectively). Additionally, Fourier transform infrared spectroscopic analysis revealed that enzymatic hydrolysis caused protein unfolding, and the content of β-turns and random coils reached 50.20% and 10.67%, respectively. Fluorescence-dependent detection of CNPP indicated a reduction of spectral intensity and the occurrence of a red shift. The changes in the structure of CNPP significantly affected its functional characteristics. CNPP has better solubility, foaming, and digestion properties than those of casein and whey protein. Specifically, the foam stability and emulsification properties decreased in the order of casein > CNPP > whey protein. The present study can provide a substantial basis for future application of CNPP as a functional ingredient against sarcopenia.

Intracellular ethanol-mediated oxidation and apoptosis in HepG2/CYP2E1 cells impaired by two active peptides from seahorse (Hippocampus kuda bleeler) protein hydrolysates via the Nrf2/HO-1 and akt pathways

Seahorse (Hippocampus kuda Bleeler) are representative marine species in aquaculture, with special value of medicine and food. In this study, the protective effects of two peptides from seahorse hydrolysates (SHP-1 and SHP-2) against ethanol-mediated oxidative stress in HepG2/CYP2E1 cells were investigated. Firstly, SHP-1 and SHP-2 presented no cytotoxicity. Compared with the ethanol-treated groups, SHP-1 and SHP-2 increased cell viability in a concentration-dependent manner. Secondly, SHP-1 and SHP-2 markedly reduced intracellular reactive oxygen species (ROS) generation, gamma-glutamyltranspeptidase (GGT) activity, and tumor necrosis factor-α (TNF-α) levels and remarkably enhanced superoxide dismutase (SOD) and glutathione (GSH) activities. SHP-1 and SHP-2 also down-regulated the expressions of GGT, bax, c-caspase-8/-9/-3, p-Akt, p-IκB-α, p-p65, p-ERK, and p-p38 but up-regulated SOD, GSH, NF-E2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), and bcl-2 levels, as revealed by Western blot analysis. Moreover, SHP-1 and SHP-2 increased the mitochondrial membrane potential (MMP), reduced DNA damage, and suppressed the nuclear translocation of p65. These results suggest that two peptides from seahorse hydrolysates can be considered a potential functional biomaterial and further improve the use value of seahorse in aquaculture.

Encapsulation of oyster protein hydrolysates in nanoliposomes: Vesicle characteristics, storage stability, in vitro release, and gastrointestinal digestion

In this study, oyster protein hydrolysates (OPH) were obtained from oyster meat by hydrolysis using animal complex proteases and then encapsulated in nanoliposomes. The physicochemical properties, stability, and digestive characteristics of OPH-loaded nanoliposomes were evaluated. The average size and zeta potential ranged from 95.64 to 102.39 nm and from -47.36 to -36.43 mV, respectively. Liposomes containing 4 mg/mL OPH had the highest encapsulation efficiency (74.53%). Fourier transform infrared spectroscopy analysis showed that effective ionic complexation and hydrogen bonding existed between phospholipid and peptides. The liposomes exhibited the highest stability when stored at 4 °C. Liposomal encapsulation may protect the antioxidant peptides in OPH during storage and simulated digestion. The nanoliposomes were not hydrolyzed and the structural integrity was maintained in gastric digestion, but exhibited lower stability in the intestinal phase. A prolonged release of OPH from nanoliposomes was also observed as compared with free OPH. Liposome containing protein hydrolysates may be used as a formula in functional foods. PRACTICAL APPLICATION: This study provides some useful information on the application of oyster protein hydrolysates or peptides in functional foods. The incorporation into liposomes may protect the hydrolysates against harsh conditions during storage and digestion, and also prolong the release time.

Use of Alcalase in the production of bioactive peptides: A review

This review aims to cover the uses of the commercially available protease Alcalase in the production of biologically active peptides since 2010. Immobilization of Alcalase has also been reviewed, as immobilization of the enzyme may improve the final reaction design enabling the use of more drastic conditions and the reuse of the biocatalyst. That way, this review presents the production, via Alcalase hydrolysis of different proteins, of peptides with antioxidant, angiotensin I-converting enzyme inhibitory, metal binding, antidiabetic, anti-inflammatory and antimicrobial activities (among other bioactivities) and peptides that improve the functional, sensory and nutritional properties of foods. Alcalase has proved to be among the most efficient proteases for this goal, using different protein sources, being especially interesting the use of the protein residues from food industry as feedstock, as this also solves nature pollution problems. Very interestingly, the bioactivities of the protein hydrolysates further improved when Alcalase is used in a combined way with other proteases both in a sequential way or in a simultaneous hydrolysis (something that could be related to the concept of combi-enzymes), as the combination of proteases with different selectivities and specificities enable the production of a larger amount of peptides and of a smaller size.

The beneficial effect of oyster peptides and oyster powder on cyclophosphamide-induced reproductive impairment in male rats: A comparative study

This study aimed to evaluate the effect of oyster peptides and oyster powder on the procreative capacity of rats displaying reproductive dysfunction induced by cyclophosphamide (CTX). The amino acid composition and relative molecular mass of the oyster peptides and oyster powder were detected using an automatic amino acid analyzer and high-performance liquid chromatography (HPLC). After 5 d of exposure to CTX and six weeks of oyster peptide and oyster powder treatment, the biochemical serum indexes of the rats, the expression of related genes and proteins in the testes, as well as the antioxidant status and pathological state of the testes and kidneys were examined. The results showed that oyster peptides could effectively improve the biochemical blood indexes of rats, and increase the level of androgen in the blood, while improving the pathological state and oxidative stress state of the kidneys and testes, therefore, exhibiting a beneficial effect on reproductive injury. PRACTICAL APPLICATIONS: This study examined the activity of oyster peptides and their ability to enhance the procreative capacity of rats with reproductive dysfunction induced by CTX while analyzing the amino acid composition and relative molecular mass of the oyster peptides. The results of this experiment provided a preliminary theoretical basis for the development of new functional foods using oyster peptides.

Frationation of hydrolysate from corn germ protein by ultrafiltration: In vitro antidiabetic and antioxidant activity

In the present work, defatted corn germ was hydrolyzed by three proteases and further separated by sequential ultrafiltration with different molecular weight cutoff (100, 10, 2 kDa). Corn germ protein hydrolysate (CGPH) and their fractions were investigated for antioxidant activity, α-glucosidase, α-amylase, and DPP-IV inhibitory activity. The degree of hydrolysis (DH) after 2 hr was 17.5%, 11.14%, and 2.05% for alcalase, trypsin, and flavourzyme, respectively. Trypsin hydrolysate showed the highest DPPH and ABTS+ radical scavenging and Fe2+ chelating activity, but a lower α-glucosidase inhibitory activity. F1 fraction (<2 kDa) exhibited highest radical scavenging and α-glucosidase inhibitory activity. While F2 fraction (2-10 kDa) showed the higher Fe2+ chelating and α-amylase inhibitory activity, F1 fraction of flavourzyme showed the highest α-glucosidase inhibitory and F2 fraction of alcalase and flavourzyme exhibited highest α-amylase inhibitory activity. Hydrolysate and F1 fraction of alcalase and F2 fraction of trypsin showed the highest DPP-IV inhibitory activity. RP-HPLC results showed that trypsin hydrolysate had higher levels of high-hydrophobic peptides. The amino acid composition of the F1 fractions showed high levels of hydrophobic amino acids. Thus, CGPHs may be used as a potential source of antioxidant and antidiabetic peptides in food industry and pharmaceutical application.

The purification and identification of immunoregulatory peptides from oyster (Crassostrea hongkongensis) enzymatic hydrolysate

Oysters, favored as a delicious seafood by people worldwide, contain various nutritional components, especially proteins. In this work, the immunoregulatory peptides were isolated and purified from oyster enzymatic hydrolysate by utilizing anion exchange chromatography and RP-HPLC, and were identified via LC-MS/MS. A proliferation assay, a phagocytosis assay, and TNF-α production, NO production and IL-6 production assays were used to examine the immunoregulatory effects of the two identified peptides. The results indicate that the peptides, DNSIAMESMK (P1) and LLQLGSGR (P2), increased the proliferation rate of macrophages, TNF-α and NO production, IL-6 production, and the phagocytosis ability, but to different degrees; P2, with more hydrophobic amino acids, was more potent than P1. This suggested that these peptides might be potential candidates for developing immunoregulatory functional foods and nutraceuticals.