Sweet potato protein hydrolysates: antioxidant activity and protective effects on oxidative DNA damage

In this study, sweet potato protein (SPP) hydrolysates were prepared by six enzymes (alcalase, proleather FG‐F, AS1.398, neutrase, papain and pepsin). The antioxidant activities and protective effect against oxidative DNA damage of SPP hydrolysates were investigated. Alcalase hydrolysates exhibited the highest hydroxyl radical‐scavenging activity (IC₅₀ 1.74 mg mL^?1) and Fe²⁺‐chelating ability (IC₅₀ 1.54 mg mL^?1) (P < 0.05). Compared with other five hydrolysates, the hydrolysates obtained by alcalase had the most abundant <3‐kDa fractions. In addition, below 3‐kDa fractions of alcalase hydrolysates showed the highest antioxidant activities and protective effects against DNA damage through both scavenging hydroxyl radicals and chelating Fe²⁺, which was probably because of the increase in several antioxidant amino acids, such as His, Met, Cys, Tyr and Phe, as well as the hydrophobic amino acids. The results suggested that enzymatic hydrolysis could be used as an effective technique to produce high value‐added peptides products from SPP.     

Effect of in vitro gastrointestinal digestion on the antioxidant activity of protein hydrolysates prepared from Cape hake by‐products

The antioxidant activity of fish protein hydrolysates may change in the digestive tract during the human gastrointestinal digestion depending on their preparation conditions. Thus, the objective of this study was to assess the antioxidant properties of Cape hake hydrolysates prepared by three different methods (HPH‐A, HPH‐B and HPH‐C) and the effect of their in vitro gastrointestinal digestion on their antioxidant properties. HPH‐A showed the highest reducing power, while HPH‐B and HPH‐C exhibited the highest OH antiradical activity. Fe²⁺‐chelating activity was similar for all hydrolysates, but HPH‐C had a higher Cu²⁺‐chelating activity comparable to that of EDTA. The in vitro gastrointestinal digestion of hydrolysates caused a decrease in the DPPH inhibition, but an increase in scavenging ABTS in all hydrolysates. Copper‐ and iron‐chelating activities increased after digestion of hydrolysates. The results showed that the gastrointestinal digestion of HPHs generally increased their antioxidant properties.     

Evaluation of free radical‐scavenging activities of sweet potato protein and its hydrolysates as affected by single and combination of enzyme systems

To evaluate the free radical‐scavenging activities of sweet potato protein (SPP) and its hydrolysates, single enzymes alone (alcalase, neutrase, protamex) or in combination with flavourzyme were employed. Compared with SPP, free radical‐scavenging activities of the resulting hydrolysates were all significantly increased (P < 0.05). Alcalase (ALC) hydrolysates exhibited the highest superoxide, hydroxyl and 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical‐scavenging activities (P < 0.05), which was 18.71 ± 0.22, 27.13 ± 0.24 and 90.10 ± 0.15% respectively. Compared with SPP hydrolysates by single enzymes, the hydrolysates obtained by combination of enzyme systems exhibited higher degree of hydrolysis, but lower free radicals scavenging activities. In addition, the content of several antioxidant amino acid residues, such as His, Met, Tyr and Phe, in ALC hydrolysates was much higher compared with SPP and other hydrolysates using amino acids composition assay. The results suggested that peptides with free radical‐scavenging activity could be released from entire SPP chain via moderate enzymatic hydrolysis.     

Antioxidant function of tea dregs protein hydrolysates in liposome–meat system and its possible action mechanism

Tea dregs possess abundant proteins, and the objective of this study was to investigate the antioxidant activity of tea dregs protein hydrolysate with limited hydrolysis by protamex and its possible action mechanism. Tea dregs protein was hydrolysed by alcalase, protamex or neutrase. The hydrolysis condition was optimised, and the hydrolysate was characterised for 1,1‐diphenyl‐2‐picryl hydrazyl (DPPH) radical‐scavenging activity, hydroxyl radical‐scavenging activity and antioxidant activity in linoleic acid (LA) system and in chicken products. Tea dregs protein hydrolysate (TDPH) was formulated (0.1%, 0.5%, 1.0%, w/w) into chicken products to determine in situ antioxidant efficacy. Thiobarbituric acid‐reactive substances (TBARS) and peroxide value (POV) formed in chicken products during storage (4 °C, 0–7 days) were analysed. Results showed that the optimum hydrolysis condition was at 50 °C, pH 7.0 for 20 min, and the concentration of tea dregs protein was 1.5%; ratio of protamex to substrate was 6000 U g^?1. The radical‐scavenging ratio of TDPH to 1,1‐diphenyl‐2‐picryl hydrazyl (DPPH) was 90.30% at the concentration of 0.1 mg mL^?1 and that to hydroxyl radical was 65.18% at the concentration of 1.0 mg mL^?1. Moreover, it also showed strong antioxidant activity both in linoleic acid (LA) system and in chicken products. The molecular weight distribution of tea dregs hydrolysates was determined by nanofiltration tubular membrane, and the protein hydrolysates with molecular weight above 8000 Da had more effective antioxidant activity. The radical‐scavenging activities to DPPH and hydroxyl radical were 85.72% at 0.1 mg mL^?1 and 71.52% at 1.0 mg mL^?1, respectively. These findings suggest that the enzymatic hydrolysate of tea dregs protein probably possesses the specific peptides/amino acids which could stabilise or terminate the radicals through donating hydrogen. In addition, the hydrolysate could form a physical barrier around the fat droplets.     

Purification and identification of antioxidant peptides from corn gluten meal

Corn gluten meal was hydrolyzed by alkaline protease and Flavourzyme to obtain the antioxidant peptides. The antioxidant activities of the hydrolysates or peptides were evaluated by free radical scavenging capacity (1,1-diphenyl-2-picrylhydrazyl/2,2-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt/hydroxyl radical/superoxide radical anion), metal ion (Fe²⁺/Cu²⁺) chelating activity and lipid peroxidation inhibitory capacity. The hydrolysates were separated by ultrafiltration, and those with molecular weight <10 kDa exhibited highest antioxidant activity in all relevant assays. The hydrolysates were subsequently purified by gel filtration chromatography, and fraction F3 showed the highest antioxidant activity. Three peptides were identified from fraction F3 using LC–ESI–Q–TOF MS/MS as Leu-Pro-Phe (375.46 Da), Leu-Leu-Pro-Phe (488.64 Da) and Phe-Leu-Pro-Phe (522.64 Da). These peptides exhibited good free radical scavenging activity and lipid peroxidation inhibitory effect. Thus, corn gluten meal may be used as a potential source of antioxidant peptides for food and nutraceutical applications.     

碱性蛋白酶水解时间对玉米谷蛋白理化性质及抗氧化活性的影响

为探究碱性蛋白酶(alcalase)水解对玉米谷蛋白理化性质及抗氧化活性的影响,对不同水解时间获得的玉米谷蛋白水解物的表面疏水性、二硫键含量、热性能、分子质量分布、抗氧化活性等进行了评价。结果表明：碱性蛋白酶水解对玉米谷蛋白的性质有显著影响,分子质量和二硫键含量显著降低(P<0.05),与玉米谷蛋白相比其水解物具有较高的溶解性、起泡性、乳化性和热稳定性。此外,玉米谷蛋白水解产物具有良好的抗氧化性能,当水解时间为150 min时玉米谷蛋白水解物的DPPH自由基清除为(54.46±1.43)%,羟自由基(·OH)清除率为(74.06±1.49)%,Fe²⁺螯合力为(86.69±1.35)%。     

Bioactive properties of enzymatic hydrolysates from abdominal skin gelatin of yellowfin tuna (Thunnus albacares)

Gelatin (90.6 ± 0.1%) was optimally prepared by response surface methodology from yellowfin tuna (Thunnus albacares, YT) abdominal skin. To investigate bioactive properties of enzymatic hydrolysates from the abdominal skin gelatin (ASG), ASG was hydrolysed with alcalase, protamex, neutrase and flavourzyme as affected by hydrolysis time. Antioxidant, nitrite scavenging and angiotensin‐I converting enzyme (ACE) inhibitory activities of the hydrolysates were determined. Antioxidant activities of the hydrolysates were found through linoleic acid peroxidation inhibitory effects. Alcalase‐derived hydrolysates (AHs) were more effective than others in metal ions chelating, superoxide anion scavenging and hydroxyl radical scavenging activities (P < 0.05). AHs showed significantly stronger nitrite scavenging activities (44.4–60.7%) than others (P < 0.05). Fraction A from AH showed strong ACE inhibitory activity (IC₅₀ of 0.75 mg mL^?1). These results suggest that YT ASG and its enzymatic hydrolysates could be functional food and/or pharmaceutical ingredients with potent antioxidant, anticarcinogenic and antihypertensive benefits.     

Biochemical properties and antioxidant activity of myofibrillar protein hydrolysates obtained from patin (Pangasius sutchi)

Antioxidant activities of myofibrillar protein hydrolysates (MPH) prepared from patin (Pangasius sutchi) using papain and Alcalase^® 2.4 L with different degrees of hydrolysis (DH) were investigated. With a DH of 65.83%, the hydrolysate prepared with papain exhibited the maximum of 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical‐scavenging activity (71.14%) with a reducing power of 0.310. At a concentration of 1 mg mL^?1, the papain‐MPH exhibited a Trolox equivalent antioxidant capacity (TEAC) of 70.50 ± 1.22 μmol g^?1 protein. With a DH of 83.6%, the Alcalase‐MPH had the highest metal‐chelating activity. Low molecular weight peptides showed higher antioxidant activities than high molecular weight peptides. Both papain‐MPH and Alcalase‐MPH contained high amounts of the essential amino acids (48.71% and 48.10%, respectively) with glutamic acid, aspartic acid and lysine as the dominant amino acids. These results suggest that the protein hydrolysates derived from patin may be used as an antioxidative ingredient in both functional food and nutraceutical applications.     

米糠贮藏时间对米糠可溶性膳食纤维抗氧化性质的影响

以新鲜米糠为原料贮藏0、1、3、5、10 d得到不同酸败程度的米糠,稳定化和脱脂后制备米糠可溶性膳食纤维,研究米糠贮藏时间对米糠可溶性膳食纤维抗氧化性质的影响。结果表明:随着新鲜米糠贮藏时间的延长,米糠可溶性膳食纤维的还原能力、金属离子螯合能力和清除ABTS~+·、DPPH·、·OH、O_2~-·能力均先上升后下降;米糠可溶性膳食纤维还原能力、金属离子螯合能力和清除ABTS~+·、DPPH·、·OH在新鲜米糠贮藏5 d时达到最大值,分别为0.943(OD_(700))、35.16%、32.28%、73.51%和13.83%,米糠可溶性膳食纤维清除O_2~-·能力在新鲜米糠贮藏1 d达到最大值,为60.58%。     

Production of bioactive proteins and peptides from the diatom Nitzschia laevis and comparison of their in vitro antioxidant activities with those from Spirulina platensis and Chlorella vulgaris

This research focuses on green production of bioactive proteins and hydrolysates from Nitzschia. A comparison of antioxidant activities was established between protein extracts and hydrolysates from Nitzschia and two other well‐known microalgae, chlorella and spirulina. Protein hydrolysates from these microalgae were produced using Alcalase^®, Flavourzyme^® and Trypsin. The hydrolysis process enhanced the antioxidant activities in general, especially those obtained using Alcalase^®. Nitzschia showed the highest (P < 0.05) total phenolic content/reducing capacity (2.4 ± 0.02 mg GAE/100 g) after 90 min of hydrolysis with Alcalase^®. The ABTS [2,2′‐Azino‐bis(3‐ethylbenzothiazoline‐6‐sulphonic acid)] radical scavenging activity (66.77 ± 0.00%) was highest (P < 0.05) after 120 min of hydrolysis, but DPPH (2,2‐Diphenyl‐1‐picrylhydrazyl radical) was low (29.59 ± 0.02%). A correlation between ABTS activity and total phenolic contents was the highest (P < 0.05) for protein hydrolysates from all three organisms using Alcalase^®, but superoxide anion radical scavenging activity was intermediate for Nitzschia. Therefore, Nitzschia protein hydrolysates have the potential to be used as antioxidants.     

Antioxidant activities and functional properties of grass carp (Ctenopharyngodon idellus) protein hydrolysates

BACKGROUND: Grass carp, with an annual production exceeding 4 × 10⁶ t in China in 2009, has not been developed into a high‐value product. In this study the antioxidant activities and functional properties of grass carp protein hydrolysates prepared with Alcalase 2.4L (HA) and papain (HP) were investigated. The hydrolysate with strongest radical‐scavenging activity and reducing power was assessed further for changes in its antioxidant activity during simulated gastrointestinal digestion. RESULTS: As the degree of hydrolysis (DH) increased, the metal‐chelating activity of both HA and HP increased while their reducing power and 1,1‐diphenyl‐2‐picrylhydrazyl radical (DPPH^?)‐scavenging activity decreased (P < 0.05). At the same DH, HP possessed higher DPPH^?‐scavenging activity and reducing power than HA (P < 0.05). The metal‐chelating activity of HP with 10% DH was significantly increased after in vitro gastrointestinal metabolism (P < 0.05). Regarding their functional properties, all hydrolysates were more than 81% soluble over a wide range of pH (3–8). At the same DH, HP showed higher emulsion activity index but lower solubility and foaming capacity than HA. CONCLUSION: Grass carp protein hydrolysates showed high solubility over a wide pH range and could be used as natural antioxidants in food systems. Copyright © 2011 Society of Chemical Industry     

Antioxidant activity of predigested protein obtained from a range of farmed edible insects

This study investigated the antioxidant activities of peptides obtained by in vitro gastrointestinal digestion of edible insects. The antioxidant potential of edible insects' hydrolysates was determined as the free radical‐scavenging activity, ion chelating activity and reducing power. The highest antiradical activity against DPPH^˙, whose IC₅₀ value is the lowest, was noted for Amphiacusta annulipes (19.1 μg/mL) and that against ABTS^˙+ was the highest for Zophobas morio (4.6 μg/mL). The peptides obtained from A. annulipes also showed the highest Fe²⁺ chelation ability (58.82%) and reducing power (0.652). The highest ability to chelate Cu²⁺ was noted for Locusta migratoria (86.05%). The locust was characterised by the highest concentration of peptides before digestion and after digestion (3.13 and 5.88 mg/mL, respectively), and the DH was 36.29%.     

Antioxidant peptides obtained from goose egg white proteins by enzymatic hydrolysis

In this study, antioxidant peptides from goose egg white proteins produced using various enzymes were purified and characterised. Two peptides were named as p14 and p16, showing the highest scavenging activity of 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical and the highest metal ion chelating activity, respectively. The sequences of p14 and p16 were identified to be STMMEERRMKVY (1560.72 Da) and DVFRELRVQ (1161.62 Da), respectively. The sequence of p14 has a similarity of 75% to ovalbumin from Meleagris gallopavo and the sequence of p16 has a similarity of 67% to ovalbumin from Taeniopygia guttata. IC₅₀ values of p14 and p16 were determined, and results showed that DPPH radical scavenging activity was 81.6 and 205.5 μm , 2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulphonicacid)(ABTS) radical scavenging was 88.4 and 153.8 μm , hydroxyl radical scavenging was 85.5 and 116.3 μm and metal ion chelating was 170.6 and 117.9 μm , respectively. The two identified peptides from goose egg white hydrolysates act as potent natural antioxidant agents.     

The effect of lactic acid bacteria fermentation on the antioxidant activity of wheat gluten pancreatin hydrolysates

The antioxidant activities of the fermented wheat gluten hydrolysates with different fermentation times were investigated to elucidate the impact of lactic acid bacteria (LAB) fermentation on the wheat gluten hydrolysates. Prior to LAB fermentation, wheat gluten was deamidated by hydrochloric acid and then hydrolysed by pancreatin to 12 and 24 h, respectively. Results showed that LAB fermentation had significant impacts on the enzymatic efficiency and antioxidant activities of wheat gluten. The degree of hydrolysis and protein recovery of hydrolysates gradually increased and then reached maximum values, respectively, when fermenting with LAB for 36 h. The hydrolysis degree and protein recovery of fermented pancreatin 24‐h hydrolysates were larger than that of the fermented pancreatin 12‐h hydrolysates during the whole fermentation. The antioxidant activity analysis revealed a marked increase and improvement in the scavenging activities of 1,1‐Diphenyl‐2‐picrylhydrazyl·radicals, hydroxyl radicals and oxygen radical absorbance capacity, while the scavenging activities of ABTS⁺ radical decreased as the fermentation time extended. The antioxidant activities of pancreatin 24‐h hydrolysates were higher than that of the pancreatin 12‐h hydrolysates during the whole LAB fermentation.     

风味蛋白酶水解制备豌豆蛋白抗氧化酶解产物工艺条件优化

采用风味蛋白酶水解豌豆蛋白,对制备豌豆蛋白酶解产物清除DPPH.清除率进行研究;通过单因素实验和响应面回归分析,得到制备酶水解产物最佳酶解工艺条件:酶解温度48.8℃、酶解时间3.1 h、pH 5.5、加酶量4.0%、底物浓度6.0%,在此条件下,风味蛋白酶酶解产物对DPPH.清除率为60.10%。     

鸭肉蛋白源抗氧化肽的酶法制备工艺

以1,1-二苯基-2-三硝基苯肼（1,1-diphenyl-2-picrylhydrazyl,DPPH）自由基清除率为指标,采用响应曲面法（response surface methodology,RSM）优化胃蛋白酶制备鸭肉抗氧化肽的最佳酶解工艺条件。结果表明：以底物质量浓度、酶与底物质量比和酶解时间为自变量,以DPPH自由基清除率为响应值,得到的回归方程拟合度高（R2=0.995 7,R2Adj=0.992 7）。其中酶与底物质量比对DPPH自由基清除率的影响最大,其次是酶解时间,底物质量浓度的影响最小。胃蛋白酶的最优酶解工艺条件为底物质量浓度10.89 g/100 mL、酶与底物质量比0.013%、酶解时间3.54 h,此时DPPH自由基清除率的理论值可达84.23%,通过优化验证实验测得,在最优酶解条件下,DPPH自由基清除率的实际值为（83.57±0.20）%。     

Antioxidant activities of the fractionated protein hydrolysates from heat stable defatted rice bran

The hydrolysates from heat stable rice bran (HSDRB) treated by Alcalase 2.4L and Protease 500G were desalted and fractionated by hydrophobicity using a nonpolar, styrene divinylbenzene resin and macroporous adsorption resin DA201‐C. The antioxidant activities of HSDRB hydrolysates (HSDRBH) eluted by 25%, 50%, 75% and 100% ethanol were investigated using 2, 2‐di (4‐tertoctylphenyl)‐1‐picrylhydrazyl free radical‐scavenging activity assay, reducing power assay, ferrous ion‐chelating activity assay and lipid peroxidation inhibition assay. The HSDRBH‐75 had the highest reducing power assay and inhibition ratio of linoleic acid autoxidation, which might be associated with reduced molecular weight, amino acid composition and hydrophobicity. The highest metal‐chelating activity of four different fractions (at the concentration of 4 mg mL^?1) had a positive correlation (r = 0.768, P = 0.116) with the total content of basic amino acid (Lys, Arg, and His) and a negative correlation (r = ?0.886, P = 0.057) with the range of molecular weight (Mw < 1000 Da). The HSDRBH‐75 had the highest antioxidant activities in many assays, which suggests that it may become a good natural antioxidant as a food additive.     

Proteolysis characteristics of sarcoplasmic, myofibrillar, and stromal proteins separated from grass carp and antioxidant properties of their hydrolysates

Proteolysis of grass carp sarcoplasmic, myofibrillar, and stromal proteins by 5 commercial proteases were studied. Sarcoplasmic and myofibrillar protein could be well hydrolyzed by Alcalase 2.4 L to reach high protein recoveries (PR) (71.86±2.46 and 80.77±3.05%, respectively), while the maximum PR for stromal protein was only 42.83±2.84%. However, stromal hydrolysates, containing mostly 6–10 kDa fraction, exhibited higher ·OH scavenging activities due to its high content of antioxidant-assisting amino acids. Alcalase 2.4 L and pancreatin 6.0, which produced hydrolysates with relative high degree of hydrolysis (DH), were used for further hydrolysis of whole grass carp protein with the assistance of response surface methodology (RSM). The results showed that serine proteases (Alcalase 2.4 L and pancreatin 6.0) could produce sarcoplasmic, myofibrillar, or stromal hydrolysates with relatively high PR, DH, and strong ·OH scavenging activity, which may be used to prepare antioxidant hydrolysates from grass carp.     

Evaluation of antioxidant activity of muscle and skin protein hydrolysates from giant kingfish,Caranx ignobilis (Forsskål, 1775)

To assess the antioxidant properties of fish protein hydrolysate from giant kingfish Caranx ignobilis (Forsskål, 1775), muscle and skin were obtained using various proteases (papain, pepsin, trypsin and α‐chymotrypsin), respectively. Antioxidant activities of the resulting hydrolysates were evaluated using 2, 2‐diphenyl‐1‐picrylhydrazyl radical scavenging activity, reducing power and metal chelating activity. Among the hydrolysates, peptic of muscle (37 ± 1.0; 0.290 ± 0.012; 63.30 ± 0.57) and tryptic of skin (36.2 ± 1.0; 0.190 ± 0.110; 63 ± 0.57) hydrolysates, which had the highest free radical scavenging activity, was subjected to purification using Sephadex G‐25. The fractionated hydrolysates were superior to the original hydrolysates in the antioxidative activity tested. The active fractions (MF2 and SF2) effectively inhibited lipid peroxidation in linoleic acid emulsion system, and the activity was compared with α‐tocopherol. The amino acid profile of MF2 and SF2 showed a high level of essential amino acids, and the most abundant amino acids were in the order His (12.01% and 7.08%), Phe (7.05% and 6.18%) and Lys (6.76% and 4.74%). Conclusively, C. ignobilis muscle and skin hydrolysates could be a promising rich source of natural antioxidants.     

ANTIOXIDATIVE ACTIVITY OF PROTEIN HYDROLYSATE FROM ROUND SCAD MUSCLE USING ALCALASE AND FLAVOURZYME

Antioxidative activity of hydrolysates from round scad (Decapterus maruadsi) muscle with degrees of hydrolysis (DH ) of 20, 40 and 60%, prepared using Alcalase (HA) or Flavourzyme (HF), was determined. At the same DH, HF exhibited a higher 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical scavenging activity and reducing power, but a lower Fe²⁺ chelating ability than HA. HF from isopropanol‐defatted muscle with 60% DH was extracted using different solvents, and hexane (E1), dichloromethane (E2), ethyl acetate (E3) and residual (R) fractions were obtained. Among all fractions, E2 and E3 exhibited the highest DPPH radical scavenging activity and reducing power. HF with 60% DH and E2 at 1,000 ppm exhibited antioxidant activity in linoleic oxidation and lecithin liposome systems, and the results were comparable to butylated hydroxytoluene (BHT) at 100 ppm. Therefore, type of proteinase, DH and defatting process prior to hydrolysis exerted an influence on the antioxidative activity of hydrolysates.