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.     

Contribution of different molecular weight fractions to anticancer effect of sweet potato protein hydrolysates by six proteases on HT‐29 colon cancer cells

The contribution of different molecular weight fractions to anticancer effect of sweet potato protein hydrolysates (SPPH) by six proteases on HT‐29 colon cancer cells was investigated. SPPH prepared by six proteases showed certain antiproliferation effect on HT‐29 cells. Compared with other five proteases, SPPH by Alcalase exhibited the highest antiproliferation effect with the lowest IC₅₀ value of 119.72 μg mL^?1. SPPH by Alcalase was further separated into four fractions (>10, 5–10, 3–5 and <3 kDa), and <3 kDa fractions showed the strongest antiproliferation effect, which was 43.87% at 100 μg mL^?1 (P < 0.05). The <3 kDa fractions could cause G2/M cell cycle arrest with increased p21 expression and induce apoptosis via decreasing Bcl‐2 expression, increasing Bax expression and inducing caspase‐3 activation in HT‐29 cells. In addition, <3 kDa fractions could significantly inhibit cell migration of HT‐29 cells. Thus, SPPH might be potentially used as a natural supplement in functional foods.     

不同品种甘薯汁抗氧化活性的研究

研究了9个品种甘薯汁的酚类物质及其抗氧化活性,旨在为甘薯汁的开发利用提供参考依据。分别采用Folin-酚法、亚硝酸钠法、pH示差法测定了甘薯汁的总酚、总黄酮、总花色苷含量。结果表明,甘薯汁中含有丰富的酚类物质,不同品种甘薯汁的总酚、总黄酮和总花色苷含量存在差异。通过4个体外抗氧化体系（FRAP法、DPPH自由基法、ABTS+自由基法、OH自由基法）评价了甘薯汁的抗氧化能力。结果显示,不同品种甘薯汁所呈现的抗氧化能力不同,酚类物质含量较高的甘薯汁其抗氧化能力较强。从抗氧化能力方面考虑,杭引薯1号、杭引薯3号、浙紫薯1、13号这4个抗氧化能力较强的品种较适合用于果汁加工以及功能性饮品的开发。      

美拉德反应对豌豆蛋白水解物乳化性和抗氧化性的影响

本文考察了美拉德反应对不同商业蛋白酶（碱性蛋白酶、风味蛋白酶和复合蛋白酶）制备的豌豆蛋白水解物的理化性质、乳化性和抗氧化性的影响。豌豆蛋白水解物分别与葡萄糖、麦芽糊精和葡聚糖在pH7.0,60℃保温48h。结果:体系反应48h后游离氨基含量下降;希夫碱含量增加;反应物荧光强度下降。表明,豌豆蛋白水解物与糖发生了共价结合。SDS-PAGE进一步证实了高分子共聚物的生成。美拉德反应显著提高了风味蛋白酶和复合蛋白酶水解物的乳化能力,尤其是复合蛋白酶水解物与葡聚糖的反应产物表现出了极好的乳化活性和乳化稳定性。各美拉德反应产物均具有显著抑制脂质体氧化的能力（p<0.05）。所有糖中,葡聚糖制备的反应物具有最高的乳化活性和抗氧化活性。因此,葡聚糖参与的美拉德反应可作为提高豌豆蛋白水解物乳化性的一种有效方法,并完好保留水解物的抗氧化活性。      

Amino acid,structure and antioxidant properties of Haematococcus pluvialis protein hydrolysates produced by different proteases

The impact of different protease hydrolysis on the amino acid, structure and antioxidant properties of H. pluvialis protein (HP) was investigated. Results showed that the hydrolysate obtained by Alcalase exhibited the highest degree of hydrolysis (20.59%) and peptide yield (92.64%). The essential amino acid, hydrophobic, sulphur and aromatic amino acid contents of enzyme hydrolysates were significantly higher than HP (P < 0.05). FTIR spectra showed that the β-sheet proportion of HP hydrolysates were higher compared with HP, the proportion of random coil structure was lower. The α-helix content of the hydrolysate obtained by Alcalase was the highest, while the turn proportion was the lowest. The Trypsin derived hydrolysate presented the best DPPH and ABTS scavenging ability, and ferric reducing antioxidant power than other HPHs. These results suggested that HP hydrolysates have a great potential as natural functional ingredients in food manufacture.     

Hypocholesterolaemic and antioxidant activities of chickpea (Cicer arietinum L.) protein hydrolysates

BACKGROUND: Some dietary proteins possess biological properties which make them potential ingredients of functional or health‐promoting foods. Many of these properties are attributed to bioactive peptides that can be released by controlled hydrolysis using exogenous proteases. The aim of this work was to test the improvement of hypocholesterolaemic and antioxidant activities of chickpea protein isolate by means of hydrolysis with alcalase and flavourzyme. RESULTS: All hydrolysates tested exhibited better hypocholesterolaemic activity when compared with chickpea protein isolate. The highest cholesterol micellar solubility inhibition (50%) was found after 60 min of treatment with alcalase followed by 30 min of hydrolysis with flavourzyme. To test antioxidant activity of chickpea proteins three methods were used: β‐carotene bleaching method, reducing power and 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) radical‐scavenging effect since antioxidant activity of protein hydrolysates may not be attributed to a single mechanism. Chickpea hydrolysates showed better antioxidant activity in all assays, especially reducing power and DPPH scavenging effect than chickpea protein isolate. CONCLUSION: The results of this study showed the good potential of chickpea protein hydrolysates as bioactive ingredients. The highest bioactive properties could be obtained by selecting the type of proteases and the hydrolysis time. Copyright © 2012 Society of Chemical Industry     

醋蛋水解物的类蛋白反应及对抗氧化活性的影响

先利用胃蛋白酶水解醋蛋液,再添加胃蛋白酶和氨基酸对其进行类蛋白反应,研究反应条件对类蛋白产率的影响和产物抗氧化活性的变化。结果表明,优化类蛋白反应条件为:氨基酸选用色氨酸、色氨酸添加量为1mol/mol水解物游离氨基、底物浓度40%(质量分数)、反应温度65℃、pH6.0、反应时间6h。通过类蛋白反应,醋蛋水解物的抗氧化活性得到很大改善。聚丙烯酰胺凝胶电泳结果表明,反应前后醋蛋水解物的组成发生变化,有较大分子质量的肽生成。     

紫甘薯花色苷对高脂膳食氧化损伤仓鼠的保护作用机制

实验研究紫甘花色苷对高脂膳食诱导氧化损伤仓鼠的保护作用机制。40只仓鼠随机分为对照组,0.2%、0.4%、0.8%紫甘薯花色苷组(n=10),测定血清、脑及肝脏中总SOD、GSH-PX、CAT酶活力及氧化产物MDA含量,荧光定量PCR(RT-PCR)法检测肝脏中抗氧化酶基因的表达水平。血清及脑中氧化产物MDA含量紫甘薯花色苷组较对照组显著减少(P0.05),紫甘薯花色苷组血清中GSH-PX、CAT肝脏中总SOD酶活力及较对照组显著升高(P0.05);RT-PCR结果显示,紫甘薯花色苷显著上调仓鼠肝脏中Cu ZnSOD、GSH-PX酶m RNA的表达(P0.05),0.2%、0.8%组血红素加氧酶1(HO-1)基因的表达水平较对照组显著升高(P0.05)。紫甘薯花色苷对仓鼠氧化损伤有保护作用,其机制可能上调抗氧化酶的表达水平,从而增加抗氧化酶活力实现的。     

萌芽黑豆中蛋白质组分分子量分布及其抗氧化活性研究

本文目的是研究萌芽黑豆中不同蛋白质组分的分子量分布,以及各组分的抗氧化活性。采用碱提酸沉法获得萌芽黑豆中的蛋白质,通过硫酸铵盐析法逐级分离各蛋白质组分,SDS-PAGE法测定各蛋白质组分分子量分布,并从清除自由基和抗人皮肤成纤维细胞氧化损伤两个方面研究了各蛋白质组分的抗氧化活性。萌芽黑豆中蛋白质组分可以集中分离为三个部分,其分子量分布为140.0¹66.0、45.0⁷2.0、17.0²3.0ku;清除自由基和抗人皮肤成纤维细胞氧化损伤的实验结果均表明分子量在17.0²3.0ku的蛋白质组分具有最优的抗氧化活性,说明低分子量的萌芽黑豆蛋白质具有更强的抗氧化活性。      

Fish protein hydrolysates: Proximate composition,amino acid composition,antioxidant activities and applications: A review

The fish processing industry produces more than 60% by-products as waste, which includes skin, head, viscera, trimmings, liver, frames, bones, and roes. These by-product wastes contain good amount of protein rich material that are normally processed into low market-value products, such as animal feed, fish meal and fertilizer. In view of utilizing these fish industry wastes, and for increasing the value to several underutilised fish species, protein hydrolysates from fish proteins are being prepared by several researchers all over the world. Fish protein hydrolysates are breakdown products of enzymatic conversion of fish proteins into smaller peptides, which normally contain 2–20 amino acids. In recent years, fish protein hydrolysates have attracted much attention of food biotechnologists due to the availability of large quantities of raw material for the process, and presence of high protein content with good amino acid balance and bioactive peptides (antioxidant, antihypertensive, immunomodulatory and antimicrobial peptides).     

涂膜结合冷藏对鲜切甘薯抗氧化性的影响

为了保持鲜切甘薯的色泽及抗氧化性,延长其货架期,研究黄原胶、壳聚糖、海藻酸钠及羧甲基纤维素钠涂膜处理对鲜切甘薯贮藏期间色泽及抗氧化性的影响。结果表明,随贮藏时间延长,对照组的褐变程度不断加重,多酚含量和抗氧化活性明显降低;涂膜处理能明显降低褐变程度,防止贮藏后期酚类物质的氧化,从而减缓鲜切甘薯的整体抗氧化能力的下降程度。      

Angiotensin-I converting enzyme inhibitory and antioxidant activities of egg protein hydrolysates produced with gastrointestinal and nongastrointestinal enzymes

Egg is a well-known rich source of bioactive peptides. In this study, egg protein (egg white and egg yolk proteins) hydrolysates were produced with gastrointestinal enzymes (pepsin and pancreatin) or nongastrointestinal enzymes (thermolysin and alcalase), and fractionated by ultrafiltration and cation exchange chromatography. Angiotensin-I converting enzyme (ACE) inhibitory and antioxidant activities, amino acid composition and molecular weight distribution were studied, and the physicochemical properties were related with the bioactivities. Our results showed that egg protein hydrolysates produced with non-GI enzymes (thermolysin and alcalase) showed significantly higher ACE inhibitory activity, whereas similar or even lower antioxidative activities, than those of hydrolysates produced with GI enzymes. ACE-inhibitory activity significantly correlated with the amino acid composition, especially the proportion of positively charged amino acid, whereas antioxidant activities correlated with the proportion of low molecular weight peptides under 500 Da. Understanding the relationship between the bioactivities and physicochemical properties of the hydrolysates/fractions is important to facilitate the development technologies for preparing fractions with improved bioactivities.     

芡实多糖的提取、抗氧化活性及对质粒DNA氧化损伤防护作用的研究

采用纤维素酶超声辅助法提取芡实多糖,由正交实验获得芡实多糖的最佳提取条件,并探究其体外抗氧化活性及对H2O2光解反应诱导质粒p BR322 DNA损伤的保护作用。结果表明芡实多糖的最佳提取条件为:料液比1∶20(g/m L)、p H3、纤维素酶用量为原料质量的2.0%、超声时间5min、提取时间3h、提取温度40℃,多糖得率为17.04%。芡实多糖清除DPPH·、羟基自由基的能力较好,IC50分别为1.78、6.96mg/m L,清除过氧化氢、超氧阴离子自由基的能力较弱,浓度为10mg/m L时,清除率分别为48.00%、20.32%。芡实多糖对抑制DNA损伤具有显著作用,在多糖水溶液质量浓度为0.08mg/m L时,具有最佳保护作用;在质量浓度大于1.0mg/m L时,对质粒DNA没有保护作用,甚至促进了DNA的损伤。综上所述,芡实多糖具有抗氧化及抑制DNA氧化损伤的能力。      

不同品种紫甘薯体外抗氧化活性的比较

用ABTS、DPPH和铁离子还原能力对4种紫甘薯花色苷的抗氧化活性进行测定,并与葡萄皮、紫米花色苷以及天然抗氧化剂BHT进行比较。结果表明:紫甘薯花色苷对DPPH.、ABTS+.和铁离子还原能力的EC50值分别在40.00～51.78μg/mL、22.82～26.04μg/mL和47.26～59.60μg/mL,而葡萄皮花色苷和紫米花色苷对DPPH.、ABTS+.和铁离子还原能力的EC50值分别为68.24μg/mL和138.32μg/mL、27.36μg/mL和68.39μg/mL、70.29μg/mL和169.49μg/mL,BHT对DPPH.、ABTS+.和铁离子还原能力的EC50值为39.48μg/mL、29.00μg/mL和82.59μg/mL。由各物质的EC50值可以得出,紫甘薯花色苷比葡萄皮和紫米花色苷有较高的自由基清除能力和铁离子还原能力。     

红薯叶黄酮类化合物提取及其抗氧化作用研究

采用不同方法提取红薯叶中黄酮类化合物,比较不同提取方法提取率及提取物中黄酮类化合物含量,从而确定最佳提取方法;结果表明,用体积分数为60%乙醇提取法是较为理想方法。同时采用烘箱贮存法测定红薯叶黄酮类化合物在猪油中抗氧化活性,实验结果表明,红薯叶黄酮类化合物具有明显抗氧化效果,且抗氧化活性随加入量增加而增强,其抗氧化效果强于抗坏血酸和柠檬酸。     

Effects of ultrasound-assisted enzymatic hydrolysis and monosaccharides on structural,antioxidant and flavour characteristics of Maillard reaction products from sweet potato protein hydrolysates

Effects of ultrasound (US)-assisted enzymatic hydrolysis and different monosaccharides (arabinose; xylose, XY; galactose and glucose) on peptide structure, antioxidant activities and flavour characteristics of Maillard reaction products (MRP) from sweet potato protein hydrolysates were investigated. US markedly enhanced the MR progress, and USXY showed the lowest pH value of 5.04, the highest browning intensity and fluorescence intensity (P < 0.05). FTIR results revealed significant peptide structure changes in USXY, USAR and USGA compared to other samples. USXY exhibited the highest Oxygen radical absorbance capacity (ORAC) value of 109.15 µg TE/mL, followed by USGA and USAR (94.07 and 93.41 µg TE/mL), respectively (P < 0.05). USXY and USAR showed different aroma features as compared to other MRP (P < 0.05). In addition, US enhanced umami, sweetness and sourness attributes and reduced bitterness of all MRP. USXY exhibited the highest umami intensity score (7.4), followed by USGA (7.3) and USAR (7.2), respectively. Partial least square regression analysis showed that the stronger umami taste was strongly correlated to aldehydes, thiophenes, MW 1000–3000 and 500–1000 Da peptides. Thus, US-assisted enzymatic hydrolysis and MR with xylose (XY) could be a promising way to produce natural flavouring with improved antioxidant activity.     

Combined effects of high-pressure and enzymatic treatments on the hydrolysis of chickpea protein isolates and antioxidant activity of the hydrolysates

A chickpea protein isolate (CPI) was pretreated before hydrolysis under a pressure that varied between 100 and 600MPa. The hydrolysis rate increased significantly with pressure above 300MPa. At 40min, the DH of the control was 15.3%, while the DH of the CPI treated at 300MPa was 18.5%, which reached 23.74% post treatment at 400MPa. The pretreatment of CPI above 300MPa enhanced the superoxide anion capturing rate of enzymatic hydrolysis. Pretreatment at 400MPa significantly reduced the hydrolysis time with the release of antioxidant peptides. While hydrolysis by Alcalase during treatment at high pressure (100-300MPa) significantly increased the degree of hydrolysis (DH), its maximum value peaked after hydrolysis at 200MPa for 30min. In addition, hydrolysates obtained at high pressure (100-300MPa) had a higher superoxide anion capturing rate. High-pressure treatment at 200MPa for 20min resulted in products with high antioxidative activity. The molecular-weight (MW) determination of the enzymatic hydrolysates indicated that hydrolysis at high pressure could significantly increase the amount of low-molecular-weight peptides.     

黄蜀葵花黄酮抗氧化性及对DNA氧化损伤的保护作用

采用石油醚、乙酸乙酯和正丁醇对黄蜀葵花乙醇提取物进行分级萃取,得到石油醚相、乙酸乙酯相、正丁醇相和水相4个不同极性成分。采用DPPH·清除、·OH清除和H_2O_2清除试验考察了其抗氧化活性,研究了正丁醇相对·OH和H_2O_2诱导DNA氧化损伤的保护作用,并利用HPLC—MS对正丁醇中黄酮类物质进行了鉴定。结果表明:黄蜀葵花黄酮主要富集于乙酸乙酯相和正丁醇相;乙酸乙酯相对DPPH·的清除能力最好,IC_(50)值为0.038 6 mg/mL,而正丁醇相对·OH和H_2O_2的清除能力较好,IC_(50)值分别为0.225 0,0.575 7mg/mL;正丁醇相对·OH和H_2O_2诱导的DNA氧化损伤都有保护作用;正丁醇相中含有11种黄酮类化合物。