三种多酚对羟自由基氧化花生球蛋白的影响

为探究3种多酚对羟自由基氧化花生球蛋白的干预作用,通过建立羟自由基氧化体系,采用不同浓度梯度的儿茶素、绿原酸、杨梅素进行干预,分析花生球蛋白的羰基、游离氨基、浊度、紫外可见、荧光光谱及二级结构等变化规律。结果表明,不同浓度的3种多酚对羟自由基氧化花生球蛋白均有一定的抑制作用,其中13.33μmol/g的儿茶素可使羟自由基氧化花生球蛋白的羰基含量下降22.55%,内源荧光最大波长发生红移,66.67μmol/g的儿茶素使游离氨基上升32.08%,二级结构中无规则卷曲含量下降;杨梅素可使花生球蛋白浊度降低68.63%;绿原酸使蛋白的α-螺旋含量和最大紫外吸光值上升。综上,3种多酚的干预可减少或缓解羟自由基对花生球蛋白的氧化损伤,进而影响其结构和性质,其中儿茶素的氧化抑制效果最好。该研究可为花生蛋白的氧化研究和进一步加工利用提供科学依据。     

多酚对过氧自由基氧化花生球蛋白的干预效应北大核心CSCD

为了对花生蛋白的加工贮藏提供参考,探究了多酚对过氧自由基氧化花生球蛋白的影响。通过2,2′-偶氮二异丁基脒二盐酸盐建立花生球蛋白氧化体系,采用不同浓度的阿魏酸、绿原酸、儿茶素对氧化体系进行干预,分析多酚对氧化花生球蛋白羰基、游离氨基、巯基、溶解度、浊度和内源荧光光谱的影响,并对各指标进行了相关性分析。结果表明:不同浓度的3种多酚干预后,花生球蛋白的羰基含量不同程度地降低,游离氨基、巯基含量上升,最大内源荧光波长发生红移,浊度增大,溶解度总体变化较小;相关性热图分析说明蛋白质的功能性与其氧化程度相关。综上,适量的多酚可抑制过氧自由基对花生球蛋白的氧化,且3种多酚对氧化体系的干预效果不同,其中绿原酸抑制花生球蛋白氧化的能力最好。     

羟自由基氧化对花生球蛋白结构和功能性质的影响

为深入研究自由基氧化对花生球蛋白的影响,建立由铁/过氧化氢/抗坏血酸组成的羟自由基氧化体系,通过控制过氧化氢浓度对花生球蛋白进行不同程度的氧化处理,考察羟自由基氧化对花生球蛋白结构和性质的影响。研究表明,随着过氧化氢浓度的增大,花生球蛋白的羰基含量、浊度、起泡稳定性呈上升的趋势;游离巯基、总巯基、溶解度和表面疏水性呈现明显下降的趋势;乳化性、乳化稳定性和起泡性呈先上升后下降的趋势;紫外扫描图谱表明,氧化导致花生球蛋白的紫外吸收峰强度明显减弱,最大波长发生轻微蓝移;差示扫描量热法结果显示,羟自由基修饰后的花生球蛋白的放热峰依次为74、72、70、75、70、72、73℃,与对照组(72℃)相比无明显变化;圆二色谱分析表明,随着过氧化氢浓度的增加,花生球蛋白的二级结构发生改变,其α-螺旋结构明显减少,无规则卷曲结构明显增加。结果表明,羟自由基氧化对花生球蛋白的性质和结构有较大影响,可通过适度氧化对花生球蛋白结构和功能性质进行调控,获得具较好乳化性和起泡性的花生球蛋白。     

过氧自由基氧化对花生球蛋白结构及聚集行为的影响

采用不同浓度的2,2′-盐酸脒基丙烷[2,2′-azobis（2-amidinopropane）,AAPH]有氧热分解产生的过氧自由基氧化花生球蛋白,研究AAPH 氧化对花生球蛋白分子结构及聚集行为的影响。结果显示：随着AAPH 浓度的增加,花生球蛋白表示浊度的吸光度由0.20±0.01 增加至0.44±0.01,平均粒径从（153.94±3.31）nm 增加到（196.80±3.06）nm,而游离巯基含量从（14.62±0.08）μmol/g 下降到（7.77±0.25）μmol/g,Zeta 电位绝对值从（24.17±0.06）mV 下降到（15.93±0.05）mV。对荧光最大发射波长的研究表明,在AAPH 浓度为0～1 mmol/L 时,内源荧光最大荧光峰位红移,在AAPH 浓度为5～15 mmol/L 时,内源荧光最大荧光峰位蓝移。过氧自由基氧化导致花生球蛋白α-螺旋结构含量下降,β-折叠和无规则卷曲含量上升,呈现出α-螺旋向β-折叠和无规则卷曲转化的趋势。扫描电镜观察结果显示,花生球蛋白经过氧自由基氧化后,蛋白由聚集紧实逐渐变得发散,浓度从10 mmol/L 升高到15 mmol/L 时,花生球蛋白表面形态变疏松,孔隙显著增大。因此,AAPH 适度氧化可以通过改变花生球蛋白的结构影响其聚集行为,特别是浓度为5～10 mmol/L 时有利于花生球蛋白的聚集。     

花生球蛋白和伴花生球蛋白在酸性条件下亚基结构的变化规律

本文通过Zeta电位、内源荧光光谱、粒度、SDS-PAGE凝胶电泳及溶解性,探讨花生球蛋白和伴花生球蛋白在酸性条件下亚基结构的变化规律。电泳分析表明,花生球蛋白40.5、37.5、35.5和27 ku亚基在常温p H 2.0~3.0的条件下被酸解,产生32.86±0.10ku的新亚基,同时22和15 ku这两条亚基增多;当p H2.0时,花生球蛋白的亚基酸解受静电屏蔽抑制。当p H为1.0~3.0,伴花生球蛋白Ⅱ61 ku亚基被酸解产生36.95±0.50、25.14±1.86、18.98±0.78和17.37±1.17 ku这四个条带。进一步研究表明,花生球蛋白和伴花生球蛋白在酸性条件下结构伸展,粒径增大,在p H 2.0-3.0时的Zeta电位及溶解度较高。在p H 2.0~3.0内,花生球蛋白荧光扫描最大发射波长相对中性条件下发生红移,红移幅度大于伴球蛋白,说明伴球蛋白展开程度较球蛋白小。伴花生球蛋白的酸解及结构变化程度都小于球蛋白,说明伴花生球蛋白亚基对酸的敏感性低于球蛋白。     

花生红衣中多酚的研究进展

多酚作为一种生物活性成分,对它的分离提取、结构和功能的研究由来已久。文中对花生红农多酚的测定方法、提取、分离纯化,以及抗氧化和抑菌活性等做了论述。     

花生球蛋白和伴球蛋白的功能特性及构象研究

本文对花生球蛋白与伴球蛋白的结构和功能特性进行了分析和比较。结果表明,花生球蛋白在等电点附近(pH4.5～6.0)比伴球蛋白具有更高的溶解性,而在偏离等电点时其溶解性低于伴球蛋白,伴球蛋白的乳化活性指数(70～180 m2/g)和起泡能力(36～57%)显著高于花生球蛋白的乳化活性指数(60～130 m2/g)和起泡能力(19～33%)(P<0.05),伴球蛋白所形成热凝胶的弹性模量值(G’)约为花生球蛋白的5倍。花生球蛋白的变性温度Td(104.84℃)及焓变值ΔH(13.78 J/g)显著高于伴球蛋白的变性温度(89.47℃)与焓变值(8.11J/g)(P<0.05);花生球蛋白分子表面的巯基(SH)较少,大部分巯基包裹于球蛋白分子内部,而伴球蛋白中大部分巯基暴露于分子的表面。荧光光谱分析表明,伴球蛋白比花生球蛋白具有更疏松的三级结构和更高的界面活性。     

3种多酚干预过氧自由基诱导核桃蛋白氧化的研究

为研究没食子酸、儿茶素、杨梅素对核桃蛋白氧化稳定性的影响,以2,2-偶氮二异丁基脒二盐酸盐(2,2’-Azobis[2-Methylpropionamidine]dihydrochloride,AAPH)为引发剂,建立过氧自由基氧化核桃蛋白的模拟体系,分析经3种多酚干预后其羰基、巯基、内源荧光、表面疏水性、溶解度等指标的变化规律。结果表明,经过氧自由基氧化后,核桃蛋白的羰基、巯基含量和表面疏水性显著增大,荧光强度和溶解度显著下降(P<0.05)。而经3种多酚干预后,核桃蛋白的羰基含量和表面疏水性相比氧化组显著降低,最大降幅分别为72.2%和58.0%;巯基含量和溶解度相比氧化模型组显著增加,最大增幅分别为2.1倍和53.0%;此外,核桃蛋白的荧光强度显著上升(P<0.05)。相关性热图和主成分分析进一步说明多酚干预可在一定程度降低核桃蛋白的氧化程度,且3种多酚干预对核桃蛋白的氧化指标存在显著区别。总体上,儿茶素对过氧自由基氧化核桃蛋白的抑制效果最好,可为核桃制品的合理储藏和加工提供一定参考。     

苹果多酚对多酚氧化酶氧化特性的影响

本文以富士苹果中含量较多的绿原酸、儿茶素、表儿茶素和根皮苷为苹果多酚氧化酶（PPO）作用底物,以磷酸盐缓冲液为苹果汁酶促褐变模拟体系,通过连续测定酶促褐变模拟体系吸光度A420值的变化趋势,研究不同苹果多酚底物对PPO酶促催化特性的影响,并确定多酚氧化酶对该4种底物较适作用条件。结果表明,苹果多酚底物对PPO反应特性影响较大;PPO酶促氧化绿原酸、儿茶素、表儿茶素和根皮苷4种多酚底物适宜的pH分别为5.0、4.0、4.5、4.5;适宜的温度分别为55、70、60、50 ℃;PPO作用适宜的底物浓度分别为5、0.5、2、10 mM;适当提高酶活可促进酶促褐变反应,且该4种底物对多酚氧化酶的亲和力大小为：儿茶素>表儿茶素>绿原酸>根皮苷。该研究为苹果汁褐变控制提供理论依据。     

花生红衣多酚的研究进展

花生红衣中含有丰富的活性物质,具有很高的营养和利用价值,但在我国作为花生产业副产品的红衣利用率并不高。近年来,其生物活性日益受到人们关注。多酚物质是花生红衣中一种天然大分子化合物,根据对近年来国内外相关资料文献的统计分析,从提取、纯化和生物活性等方面对其研究现状作了介绍,并展望了其应用前景。     

Evaluation of a numerical method to predict the polyphenols content in monovarietal olive oils

Three monovarietal virgin olive oils obtained from olives grown under biological agricultural system, in Portugal, with different ripening stages, were studied in what concerns the parameters usually related with oxidation status (total polyphenols, tocopherols, chlorophylls and carotenoids, peroxide values, oxidative stability, specific extinction coefficients K₂₃₂ and K₂₇₀ and titratable acidity). A total of 18 samples were analyzed: seven from Cv. Cobrançosa (maturation indices 1–7), five from Cv. Madural (maturation indices 3–7) and six from Cv. Verdeal Transmontana (maturation indices 1–6). Oxidative stability and polyphenols profile presented high correlation coefficients. Given this high correlation, a numerical method was developed and evaluated to predict total polyphenols contents in olive oil. The method is based on the kinetic equation of the oxidation process in the presence of antioxidants and on Rancimat profiles. Total polyphenols contents obtained with this method were similar to those obtained by the Folin-Ciocalteau method.     

Browning development in white wines: dependence on compositional parameters and impact on antioxidant characteristics

Browning is a serious problem in relation to white wine quality and mostly affects the sensory attributes, whereas its impact on the dietary value of wines has never been investigated. Browning, however, is well known to be associated with polyphenol oxidation, and therefore it may be accompanied by changes in the antioxidant capacity. On the basis of this consideration, experimental white wines vinified and stored under identical conditions were subjected to accelerated browning, and efforts were made to distinguish compositional parameters that might be related to the extent of browning development. Further, the consequences of browning on the reducing power and antiradical activity were assessed. It was shown that none of the parameters examined (titratable acidity, pH, total SO₂, total polyphenols and total flavanols) play an important role in browning onset, but SO₂ appeared to exert a statistically significant influence (r²=0.6394, P<0.05) on the percentage change in the antiradical activity. Evidence also suggested that browning development might be prominently associated with decreases in both antiradical activity (r²=0.7891, P<0.01) and reducing power (r²=0.6925, P<0.05).     

辛弗林与橙皮苷等多酚联用抑制食品体系中丙烯醛的协同效用研究

目的 生物碱和黄酮单用以及多元联用对丙烯醛(acrolein,ACR)的抑制效果。方法 利用Chou-Talalay方法,采用高效液相色谱检测辛弗林(synephrine,SYN)、橙皮苷(hesperidin, HES)单用及二元联用(半抑制浓度(half maximal inhibitory concentration,IC₅₀)恒定比例,沃柑中实际比例)对ACR的抑制活性,在此基础上与姜黄素(curcumin, CUR)、槲皮素(quercetin,QUE)、山奈酚(kaempferol,KAE)三元联用的抑制活性,采用CompuSyn软件对联用效果进行分析计算(CI<1,协同作用),并采用高效液相色谱-串联质谱测定HES、SYN、CUR联用对ACR的捕获路径,分析其协同机制。最后从模型延展至食品体系,利用富含SYN和HES的柑橘和富含CUR的姜黄应用于烤鸭翅,验证多种物质叠加对ACR的抑制效果。结果 SYN与HES按照IC₅₀恒定比例或沃柑中实际比例二元联用均具有协同抑制ACR的作用,且HES,SYN与CUR/QUE/KAE按照IC₅₀恒定比例三元复配也对ACR的抑制具有协同增效性;相比于单用,联用时SYN、HES、CUR与ACR的加合物均有所提升,阐明协同机制为互相促进捕获更多的ACR形成加合物,从而协同抑制ACR。在烤鸭翅体系中,同时添加54.21 g/kg沃柑果肉和3.334 g/kg姜黄对ACR的抑制率为57.22%。结论 SYN与HES、CUR等多酚联用对ACR的捕获具有协同增效性,协同机制为互相促进捕获更多的ACR形成加合物,且富含SYN和HES的沃柑和富含CUR的姜黄对烤鸭翅体系中生成的ACR能够达到较好的抑制效果。     

Lack of toxicological effect through mutagenicity test of polyphenol extracts from peanut shells

The toxicological effect of polyphenols extracted from peanut shells was investigated in animal models. The safety data were needed to proceed with further clinical trials. The oral LD₅₀ of peanut shells polyphenols was determined to be higher than 15,000 mg/kg body weight. We also carried out a sperm abnormality test, a chromosomal aberration test and a micronucleus test in rats. The peanut shell polyphenols did not cause any abnormalities in the system. Furthermore, the administration of peanut shell polyphenols did not significantly alter changes in body weight or clinical signs. These results strongly indicated that peanut shell polyphenols did not induce mutagenicity. The results of this study suggested a lack of toxicological effect and supported the further use of polyphenol-rich extracts from peanut shells as a potential natural antioxidant.     

Copper(II)-mediated biomimetic oxidation of quercetin: generation of a naturally occurring oxidation product and evaluation of its in vitro antioxidant properties

Quercetin was oxidized with CuSO₄ in aqueous acetonitrile, a reaction that has been previously shown to generate products that were detected in polyphenol oxidase and peroxidase-catalysed oxidation of quercetin. The major oxidation product was isolated and characterized by means of ¹H-NMR and LC-MS, as 2-(3,4-dihydroxybenzoyl)-2,4,6-trihydroxybenzofuran-3(2H)-one. This compound is a natural polyphenol reported to occur in the outer dry layers of onion bulbs. Its in vitro antioxidant properties were evaluated in comparison with the parent molecule and other natural polyphenols, employing three representative tests and the alterations in the activity observed were discussed on the basis of structure–activity relationships.     

Evaluation of cardiovascular protective effect of different apple varieties – Correlation of response with composition

Epidemiological evidence supports the concept that diets rich in fruits and vegetables promote health and attenuate or delay the onset of cardiovascular disease (CVD). In particular, a reduced risk of CVD has been associated with apple consumption, probably due to the cholesterol-lowering effect of the main bioactive compounds, namely fibre and polyphenols.     

THE INTRINSIC INFLUENCE OF CATECHINS AND PROCYANIDINS ON BEER HAZE FORMATION

Different concentrations of catechins and procyanidins were added to an all-malt Pilsner beer brewed from proanthocyanidin-free malt (ant 13·13 × Rupal) and tannin-free hop extract in order to evaluate their intrinsic role in beer haze formation, i.e. in the absence of malt and/or hop flavanoids. The molar tanning capacities of flavanoids depend upon their degree of polymerisation. Procyanidin B6 was much more haze active than procyanidin B3. Both immediate haze and formation of haze after 150 days of storage at room temperature was in general linearily related to the added concentration of phenolics.     

高效液相色谱测定黄酮类物质研究进展

对高效液相色谱定量测定不同种类黄酮的操作方法和样品前处理作一简要综述。