Preparation Of Antioxidant Peptides Research Articles

Ultrasound-assisted fermentation for antioxidant peptides preparation from okara: Optimization, stability, and functional analyses

This study investigated the effects of ultrasound-assisted fermentation (UAF) on the preparation of antioxidant peptides (UAFP) from okara and examined their content, chemical structures, and antioxidant activity. After the optimal ultrasonic processing (time, 20 min; frequency, 45 KHz; power, 120 W/L), the peptide content yield reached the maximum of 12.36 ± 0.02 mg/mL, and their DPPH free radical scavenging rate was 65.15 ± 0.32 %. UAF increased the number of globular aggregates with deeper gullies, a looser structure, and higher porosity. The experiments conducted using the oxidative stress injury model of HepG2 cells showed that okara UAFP promoted cell growth and exerted a protective effect. Moreover, ultrasonic treatment remarkably improved the environmental stability (NaCl, glucose, sodium benzoate, temperature, pH, metal ions) and antioxidant activity of UAFP. Concisely, optimal ultrasonic processing can aid the fermentation of agroindustrial by-products to prepare antioxidant peptides, such as natural food antioxidant peptides from soybean waste.

Molecular Docking Revealed the Potential Anti-Oxidative Stress Mechanism of the Walnut Polypeptide on HT22 Cells.

The preparation of novel antioxidant peptides from food raw materials is one of the research focuses, but there are fewer studies on the preparation of antioxidant peptides from walnut meal, a by-product of processing walnuts. This study analyzed the antioxidant properties and protective effects of walnut protein hydrolyzed by alkaline protease and trypsin on the oxidative stress of HT22 cells. The peptides were identified by UPLC-MS/MS, and the anti-oxidative peptides were screened based on virtual computer tools. The potential anti-oxidative stress mechanism of the walnut polypeptide on HT22 cells was explored by molecular docking. The results revealed that walnut protein hydrolysates (WPH) with molecular weights of less than 1 kDa had good antioxidant properties and inhibited oxidative damage of HT22 cells by regulating the levels of reactive oxygen species (ROS) and antioxidant enzyme catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px). Six of the ninety identified new peptides showed good solubility, non-toxicity, and bioactivity. The molecular docking results showed that the six peptides could dock with Keap1 successfully, and EYWNR and FQLPR (single-letter forms of peptide writing) could interact with the binding site of Nrf2 in the Keap1-Kelch structural domain through hydrogen bonds with strong binding forces. The results of this study provided important information on the antioxidant molecular mechanism of the walnut polypeptide and provided a basis for further development of walnut antioxidant polypeptide products.

Preparation of antioxidant peptides from Moringa oleifera leaves and their protection against oxidative damage in HepG2 cells.

Moringa oleifera leaves are a kind of new food raw materials, rich in functional factors, M. oleifera leaves aqueous extract have antioxidant activity and M. oleifera leave protein is an important active ingredient in the aqueous extract. Numerous studies have shown that peptides have strong antioxidant activity. To reveal the antioxidant effects of M. oleifera (MO) leaves peptides, MO leave antioxidant peptides were isolated and prepared to clarify their antioxidant activity. MLPH1 (<1 kDa), MLPH3 (1~3 kDa), MLPH5 (3~5 kDa), and MLPH10 (5~10 kDa) fractions were obtained by the membrane ultrafiltration classification of MO leaves proteolytic hydrolysate (MLPH). MLPH1 was further separated by centrifugal filters, and the fraction separated by <1 kDa (MLPH1-1) was identified and analyzed by LC-MS/MS. The purpose of this study was to investigate the effect of MO leaves antioxidant peptide pretreatment on H2O2-treated HepG2 cells and to refine the antioxidant activity. The results showed that MLPH1 had the strongest antioxidant activity, and three MO leaves antioxidant peptides (LALPVYN, LHIAALVFQ, and FHEEDDAKLF) were obtained. The peptide with the sequence LALPVYN and a molecular weight of 788.44 Da had the strongest antioxidant activity. After 24 h of LALPVYN pretreatment, the cell viability and the CAT, GSH-Px, and SOD enzyme activity were significantly increased, and the MDA, ROS, and apoptosis rates were significantly decreased. These results provide a theoretical basis for further research on the antioxidant mechanism of MO leaves peptides.

Effect of Microwave Pretreatment on the Antioxidant Activity and Stability of Enzymatic Products from Milk Protein.

The effects of microwave pretreatment on the antioxidant activity and stability of enzymatic products from milk protein (MP) were studied. The peptide content, molecular weight distribution, and amino acid composition of MP hydrolysate were also measured to explain the change of antioxidant activity under microwave pretreatment. The results showed that microwave pretreatment increased the degree of hydrolysis of MP with the power of 400 W for the highest value. The DPPH scavenging activity and the total antioxidant capacity of MP pretreated by microwave with a power of 300 W presented the highest effect and increased by 53.97% and 16.52%, respectively, compared to those of control. In addition, the results of thermal stability and in vitro digestion of MP hydrolysate showed that the MP hydrolysate pretreated by microwave exerted excellent antioxidative stability, especially for the microwave power of 300 W. After pretreated with microwave, the peptide content increased as the rise of power and it reached the peak at the power of 400 W. The molecular weight of MP hydrolysate pretreated by microwave with the power of 300 W showed more percentage of peptides between 200 Da and 500 Da. The result of amino acid composition showed that total amino acid (TAA) content of MP hydrolysate pretreated by microwave with power of 400 W showed the highest value, which increased by 7.58% compared to the control. The ratio of total hydrophobic amino acids to the TAA of MP hydrolysate showed the most increased amplitude with the microwave power of 300 W. The antioxidant activity of MP hydrolysate was related to the peptide content, and it was also relevant to the amino acid category and content. In conclusion, microwave pretreatment is an effective method for the preparation of antioxidant peptides and an increase in antioxidant stability.

Preparation of antioxidant peptides from hairtail surimi using hydrolysis and evaluation of its antioxidant stability

In this study, antioxidant peptides were prepared from hairtail surimi by hydrolysis. Response surface methodology coupled with a Box-Behnken design was applied to optimize hydrolysis conditions. The optimum conditions were determined as: 12.1 h incubation time, 44.74 °C incubation temperature and enzyme concentration 1858.85 U/g. The amino acid compositions analysis showed most abundant amino acid in hairtail surimi antioxidant peptides (HAP) was Glutamic acid followed by Aspartic acid and Lysine. In addition, the fraction of HAP with a molecular weight less than 3 kDa showed the strongest antioxidant activity among the 4 fractions obtained by ultrafiltration. Furthermore, HAP showed good stability in mild acidic, alkaline, or salt solutions, in in vitro digestive juice, and upon heating. In conclusion, hairtail surimi might be a good source to produce antioxidant peptides, which can be used as a natural antioxidant in food industry.

Antioxidant Assessment of Schizochytrium Meal Protein Enzymatic Hydrolysate and Its Potential Application

ABSTRACTSchizochytrium meal protein (SMP) extracted from Schizochytrium meal was hydrolyzed by flavourzyme. Response surface methodology (RSM) was used to optimize the extraction conditions for the protein extraction yield from Schizochytrium meal. 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity (DRSA) was used to evaluate the antioxidant activity of hydrolysates. The orthogonal test was used to investigate the effects of three independent variables, namely protease dosage, hydrolysis time, and pH. The optimum conditions obtained were as follows: protease dosage of 7%, hydrolysis time of 1.5 h, pH of 6, under which, DRSA at the concentration of 2 mg/mL was 89.38%. Aspartic and glutamic acid constituted approximately 26.32% of the total amino acids, and glutamic acid was the most abundant amino acid of Schizochytrium meal protein hydrolysate (SMPH) by amino acid composition analysis, which may have contributed to the scavenging activity of SMPH. Moreover, SMPH was made into chewable tablets with suitable formula and high humidity stability. These findings indicate that Schizochytrium meal can be reused as a raw material for preparation of antioxidant peptides.

Application of the Plackett-Burman design to determine the main factors affecting the anti-oxidative activity of goat's milk casein hydrolyzed by Alcalase and papain.

Antioxidant peptides can scavenge excessive free radicals produced by the metabolism, main- tain a free radical balance and prevent aging and disease. Therefore, finding natural resources with strong antioxidant activity has become a new focus for research. Single-factor experiments were used to investigate the effects of various factors (hydrolysis temperature, pH, substrate concentration, enzyme to substrate ratio (E/S), ratio of compound protease (EAlcalase/Epapain) and time on the preparation of antioxidant peptides by compound protease (Alcalase and papain) hydrolysis of goat&rsquo;s milk casein. Then, a Plackett-Burman design was used to determine the sig- nificant factors for the preparation of antioxidant peptides by hydrolysis of goat&rsquo;s milk casein with compound protease. The results of the single-factor experiments indicated that the highest anti-oxidative activity of pep- tides would be obtained at a hydrolysis temperature of 55&deg;C, a pH of 7.5, a substrate concentration of 3.0%, an E/S of 4.0%, a ratio of compound protease of 1/3 and a hydrolysis time of 180 min. The main factors affecting the activity of anti-oxidative peptides hydrolyzed from goat&rsquo;s milk casein with compound protease were determined by Plackett-Burman design and the results showed that temperature, E/S ratio and the ratio of compound protease had significant influences on the production of antioxidant peptides. This could provide a basis and reference for further optimization.

Effects of high‐intensity ultrasound pretreatment with different levels of power output on the antioxidant properties of alcalase hydrolyzates from Quinoa (Chenopodium quinoa Willd.) protein isolate

Background and objectivesThe effects of ultrasound pretreatment with different levels of power output (200, 400, and 600 W) on hydrolysis degree of Quinoa protein isolate (QPI) and antioxidant activity of QPI hydrolyzate were studied. The secondary structure, surface hydrophobicity, intrinsic fluorescence, and scanning electron microscopy (SEM) of QPI treated by ultrasound were measured. The untreated QPI and high‐temperature treatment (90°C for 30 min) were used as control.FindingsThe results showed that ultrasound pretreatment at 400 W significantly improved the hydrolysis degree of QPI and antioxidant activity of QPI hydrolyzate. The changes in secondary structure, surface hydrophobicity, and intrinsic fluorescence indicated the unfolding of QPI after ultrasound. The SEM results showed that ultrasound treatment resulted in the deformation of QPI.ConclusionsThe improvement in degree of hydrolysis might be related to the changes in structure induced by ultrasound treatment, which supported more groups for the process of enzymatic hydrolysis.Significance and noveltyThe power output selection of ultrasound pretreatment is essential for improvement of accessibility of QPI to the alcalase and preparation of antioxidant peptides.

Preparation of Antioxidant Peptides from Salmon Byproducts with Bacterial Extracellular Proteases.

Bacterial extracellular proteases from six strains of marine bacteria and seven strains of terrestrial bacteria were prepared through fermentation. Proteases were analyzed through substrate immersing zymography and used to hydrolyze the collagen and muscle proteins from a salmon skin byproduct, respectively. Collagen could be degraded much more easily than muscle protein, but it commonly showed weaker antioxidant capability. The hydrolysate of muscle proteins was prepared with crude enzymes from Pseudoalteromonas sp. SQN1 displayed the strongest activity of antioxidant in DPPH and hydroxyl radical scavenging assays (74.06% ± 1.14% and 69.71% ± 1.97%), but did not perform well in Fe2+ chelating assay. The antioxidant fractions were purified through ultrafiltration, cation exchange chromatography, and size exclusion chromatography gradually, and the final purified fraction U2-S2-I displayed strong activity of antioxidant in DPPH, hydroxyl radical scavenging assays (IC50 = 0.263 ± 0.018 mg/mL and 0.512 ± 0.055 mg/mL), and oxygen radical absorption capability assay (1.960 ± 0.381 mmol·TE/g). The final purified fraction U2-S2-I possessed the capability to protect plasmid DNA against the damage of hydroxyl radical and its effect was similar to that of the original hydrolysis product. It indicated that U2-S2-I might be the major active fraction of the hydrolysate. This study proved that bacterial extracellular proteases could be utilized in hydrolysis of a salmon byproduct. Compared with collagen, muscle proteins was an ideal material used as an enzymatic substrate to prepare antioxidant peptides.

Production and purification of antioxidant peptides from flatfish skin protein hydrolysates

Antioxidant peptides of flatfish skin protein hydrolyzed by four enzymes(Papain, Pepsin, Trypsin and Neutrase, respectively)were investigated. The Trypsin hydrolysate obtained by hydrolysis exhibited the highest 1,1-dipheny-l-2-picrylhydrazyl(DPPH)radical scavenging activity(DRSA)compared with other hydrolysates. Response surface method ology(RSM), based on Box-Behnken design, was used to study the influence of hydrolysis conditions on the DRSA. The optimal hydrolysis conditions were as follows: pH 7.38, temperature 48.2°C and enzyme/substrate(E/S)ratio 2 840 U/g. Under these conditions, the maximum DRSA was(22.85 ± 0.57)%,. The experimental values agreed with the value (23.09%,)predicted by the model within a 95%, confidence interval. By using gel filtration chromatography and reversed-phase high performance liquid chromatography(RP-HPLC), antioxidant peptide(D2-P)was isolated from flatfish skin protein hydrolysates(FSPH)and could exhibit a(54.28 ± 1.37)%, scavenging activity on DPPH radical at the concentration of 5 mg/mL. This is the first report of a scientific basis for the preparation of antioxidant peptides from flatfish skin. The results suggested that the antioxidant peptides can be exploited into functional foods or used as a novel source of nutraceuticals.

Preparation of Antioxidative Peptides from Spanish Mackerel (Scomberomorus niphonius) Processing Byproducts by Enzymatic Hydrolysis

Preparation of Antioxidative Peptides from Spanish Mackerel (Scomberomorus niphonius) Processing Byproducts by Enzymatic Hydrolysis

Antioxidant activity and physicochemical properties of 1 ku fraction by ultrafiltration of bigeye tuna (Thunnus obesus) head protein hydrolysate

To produce bioactive peptides from the by-products of fish processing,bigeye tuna(Thunnus obesus) head was hydrolyzed by alcalase,and the tuna head protein hydrolysate(THPH) was fractionated through ultrafiltration membranes with a range of molecular weight cutoffs(MWCO) of 8,5,3 and 1 ku,respectively,to yield the fraction THPH-1 with MW distribution1 ku.The antioxidant activities of THPH-1were evaluated using reducing power,free radical scavenging and aged model mice induced by D-galactose.The physicochemical properties of THPH-1 were analysed also.THPH-1 showed evident radical scavenging activity in a dose-dependent manner with the IC50 values for hydroxyl radical,superoxide radical and 1,1-diphenyl-2-pycrylhydrazyl(DPPH) radical being 1.38,0.73 and 0.93 mg/mL respectively.The reducing power of THPH-1 was 0.763 at 12.5 mg /mL.The activities of superoxide dismutase(SOD) of liver and the activities of glutathione peroxidase(GSH-PX) of liver and serum in aged model mice were significantly increased(P0.05) compared with that of the normal control group mice after 42 days administrated orally at a dose of 30 mg/kg THPH-1,and the content of malondialdehyde(MDA) of serum in aged model mice was significantly decreased(P0.01).The physicochemical properties showed that THPH-1contained 96.40% of protein(on dry basis),0.11% of fat and 4.86% of ash.The total hydrophobic amino acids content of THPH-1was 35.8% of the total amino acids content.The molecular weight distribution of the higher activity fractions of THPH-1were located at 1 802-2 519 u and 422-922 u.These results indicate that THPH-1from tuna head hydrolysate would be very fairly helpful in the preparation of antioxidative peptides and a beneficial ingredient for functional food.