共查询到20条相似文献,搜索用时 250 毫秒
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研究了黄豆分别在东湖陈醋和东湖白醋中长达31d的浸渍过程中可溶性蛋白质、多肽、多酚含量及其抗氧化性的变化。主要研究结果显示,黄豆在醋浸过程中,可溶性蛋白质含量显著降低,其中,白醋浸泡的黄豆中蛋白质含量下降了76.4%,陈醋浸泡的黄豆中蛋白质含量下降了56.7%,多肽含量总体呈增长趋势;陈醋浸豆的多酚含量及总黄酮含量随浸泡时间逐步增大,而白醋浸豆则维持在一个相对稳定的水平;抗氧化活性方面,随着浸泡时间增加,样品相同浓度的多酚提取物羟基自由基清除率下降,而DPPH、ABTS自由基的清除能力呈上升趋势。采用陈醋浸泡黄豆在多酚及总黄酮含量及DPPH自由基清除率方面都优于白醋。 相似文献
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寻找青刺果油组合物来提高产品抗氧化能力及保湿活性。将青刺果油组合物应用于产品中,通过DPPH自由基清除率以及失水率的测定,研究其抗氧化能力及保湿活性。结果表明,在干燥环境下青刺果油组合物样品随时间增加,保湿率逐渐降低,但每个时间段内其保湿率均高于对照样品(青刺果油含量0.11%);与对照样品相比,添加了虾青素、橙皮素的青刺果油样品对DPPH自由基清除能力较强;将虾青素和橙皮素组合后,提取组合物浓度在50%时DPPH自由基清除能力也可达到90%左右。研究初步验证了青刺果油组合物具有较强的自由基清除能力和保湿性能,为拓展青刺资源的综合利用供了初步的应用研究。 相似文献
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《中国生物制品学杂志》2017,(9)
目的测定酵母源金属硫蛋白(metallothionein,MT)-1、MT-2体外抗氧化能力。方法以动物源金属硫蛋白(Zn-MT)为对照,测定酵母源MT对1,1-二苯基-2-苦苯肼自由基(DPPH)、2,2-联氮-二(3-乙基-苯并噻唑-6-磺酸)二铵盐自由基(ABTS~+·)、羟基自由基(OH·)、超氧阴离子自由基(·O_2~-)的清除能力、总还原能力及抑制脂质体过氧化能力大小。结果 3种MT均对自由基有良好的清除能力,在20~100μg/ml范围内,酵母源MT-1、MT-2及Zn-MT随质量浓度的增加,对4种自由基的清除能力均不断增强,且增加趋势几乎一致;3种MT随质量浓度增加,对自由基清除能力的增率趋于平缓。3种MT对ABTS~+·、OH·、·O_2~-的清除能力差异有统计学意义(P0.01),清除能力大小为Zn-MTMT-1MT-2;对DPPH自由基清除能力大小为Zn-MTMT-1MT-2,MT-2与Zn-MT及MT-1之间差异有统计学意义(P0.01)。3种MT总还原能力随质量浓度的增加均不断增强,其中酵母源MT-1与酵母源MT-2及Zn-MT之间的IC_(50)值差异有统计学意义(P0.01),总还原能力大小为Zn-MTMT-1MT-2。3种MT均可有效抑制脂质体过氧化的产生,并随质量浓度的增加对脂质体过氧化的抑制率平缓上升,除酵母源MT-1外,在60~100μg/ml浓度范围内,MT对脂质体过氧化抑制能力的增率小于20~60μg/ml范围,且Zn-MT抑制脂质过氧化的效果优于酵母源MT,其IC_(50)大小为Zn-MTMT-1MT-2,其中酵母源MT-1与酵母源MT-2及Zn-MT之间差异有统计学意义(P0.01)。结论两种酵母源MT对体外自由基均有良好的清除效果及抑制脂质体过氧化的效果,显示出良好的体外抗氧化特性,且其体外抗氧化能力酵母源MT-1MT-2。 相似文献
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天然水溶性自由基清除剂包括酚类、维生素类、糖类、肽类等,其中自由基清除能力最强的是酚类。从新鲜女贞子中提取到的女贞子多酚极易氧化,具有显著的自由基清除作用。采用DPPH法研究了女贞子多酚对自由基的清除效果,并探讨了女贞子多酚浓度、反应时间、反应温度和女贞子采集时间对DPPH清除率的影响,比较了女贞子多酚与3种常用抗氧化剂的DPPH清除能力。结果表明,随着女贞子多酚浓度的增加、反应时间的延长和反应温度的升高,DPPH清除率逐渐升高;在女贞子多酚浓度为0.035 mg·mL~(-1)、反应时间为120 min、反应温度为30℃时,女贞子多酚对DPPH的清除率达100%;女贞子多酚与3种常用抗氧化剂的DPPH清除能力大小为:没食子酸女贞子多酚抗坏血酸还原型谷胱甘肽;不同月份女贞子多酚提取物对自由基的清除能力差异明显,随着采集时间的推迟,DPPH清除率逐渐下降,在9~12月份采集的女贞子多酚提取物中,9月份采集的女贞子多酚提取物的自由基清除能力最强。 相似文献
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过氧亚硝酸根离子(ONOO-)是一氧化氮自由基与超氧阴离子的反应产物,具有强氧化性及强硝化性,能够导致细胞及组织损伤,从而引发疾病。选取3种不同结构的天然食品添加剂桑色素、葛根素、辣椒红作为研究对象,采用荧光光谱法研究了3种天然食品添加剂对ONOO-诱导L-酪氨酸氧化损伤的抑制能力,采用邻苯三酚自氧化法研究了3种天然食品添加剂的抗氧化能力,采用高效液相色谱法研究了3种天然食品添加剂对ONOO-诱导L-酪氨酸硝化损伤的抑制能力。结果表明,随着天然食品添加剂浓度的增加,对L-酪氨酸二聚体的抑制率增大,以抑制率达到50%时的浓度(IC50)判断的抑制能力大小为:辣椒红桑色素葛根素VC,辣椒红的IC50为0.56μmol·L-1;随着天然食品添加剂浓度的增加,对邻苯三酚自氧化抑制率增大,以IC50判断的抑制能力大小为:葛根素桑色素辣椒红VC,葛根素的IC50为0.051mmol·L-1;随着天然食品添加剂浓度的增加,对L-3-硝基酪氨酸的抑制率增大,以IC50判断的抑制能力大小为:葛根素桑色素辣椒红VC,葛根素的IC50为0.00026μmol·L-1。3种食品添加剂抗自由基能力与其分子结构中主要官能团空间结构以及官能团数量密切相关。 相似文献
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针对不同温度热提质褐煤新鲜样及其自然环境中储存一定时间后的预氧化样,利用订制的自燃测定实验装置测得各样品的自燃倾向性差异,采用X-band电子自旋共振波谱仪进行自由基动态原位分析,研究预氧化对热提质褐煤自燃特性的影响。结果表明,热提质温度升高,新鲜样的自燃倾向性降低。但随着储存时间延长,105~500℃热提质褐煤发生预氧化,自燃倾向性不同程度地增加,400℃热提质后的预氧化样与原煤一样易自燃。在自燃氧化过程中,与新鲜样不同,预氧化样的吸氧量增加,自由基浓度也增加。预氧化不仅使热提质褐煤自由基增加;且在自燃的加速氧化阶段后期,不断产生自由基,维持氧化自热升温。而400℃热提质褐煤新鲜样在自燃氧化初期消耗大量小分子自由基,损失达80%,因不能持续产生活性自由基难以维持自燃氧化反应进行。 相似文献
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茶多酚的超滤分离及其在化妆品中的应用 总被引:1,自引:0,他引:1
优化了超滤分离竹叶提取液中茶多酚(TP)的工艺条件,并进行了茶多酚在化妆品中应用的功能评价。通过正交试验得到超滤分离的最优工艺为:操作温度35℃,压力0.10 MPa,原料液质量浓度为0.21 mg.mL-1,pH=7。所得产品经生物活性试验研究表明,茶多酚对酪氨酸酶活性有明显的抑制作用和较强的清除DPPH自由基、羟自由基和超氧阴离子的能力,美白乳液中添加w(TP)=1.5%就能明显降低皮肤内黑色素含量。茶多酚可作为化妆品中的天然添加剂。 相似文献
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Mauro Maccarrone Gerrit A. Veldink Johannes F. G. Vliegenthart Alessandro Finazzi Agrò 《Lipids》1995,30(1):51-54
The aim of this investigation was to determine whether chain-breaking antioxidants able to prevent lipid peroxidation can
inhibit lipoxygenase-1 (EC 1.13.11.12). Therefore, the effects of ascorbic acid, 6-palmitoylascorbic acid and trolox on the
enzyme activity were analyzed by means of Lineweaver-Burk double reciprocal plots and Yoshino's graphical method. The effect
of these compounds on the formation of free radicals during lipoxygenase-1 reaction was investigated as well, by monitoring
the enzymic formation of oxodienes. We present evidence that the chain-breaking antioxidants ascorbic acid, 6-palmitoylascorbic
acid and trolox inhibit soybean lipoxygenase-1 in the micromolar concentration range (Ki 27, 3 and 18 μM, respectively). The
inhibition is competitive, complete and reversible. All three compounds trap the free radicals formed during the lipoxygenase-catalyzed
reaction, which might substantially contribute to their inhibitory ability. These findings can have physiological significance
in the light of the lipoxygenase involvement in biomembrane remodelling. 相似文献
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分别采用不同质量比的1010和168复合抗氧剂、硬脂酸钙制备出一系列煤基PP S1003,通过不同温度下氧化诱导期(OIT)测试、多次挤出熔体流动速率测试、黄色指数YI测试等对S1003中的热氧稳定性、加工稳定性进行了分析研究。结果表明,随着主辅协同抗氧剂体系当中1010含量的提升,抗氧剂所稳定S1003体系相同温度下的OIT值逐渐增加,体现出优异的氧自由基捕获能力;配方3、配方4经多次挤出测的熔体流动速率增大趋势较为平缓,说明有效抑制了S1003的热氧化降解;多次挤出黄色指数的分布趋势表明,抗氧剂168含量的增加提升了S1003的抗色变性能,总之适宜配比的复合抗氧剂改善了S1003的抗氧化性能,这对于复合抗氧剂配方比例的优选、延长煤基PP材料的使用寿命具有重要意义。 相似文献
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超声强化O_3氧化能力的机理探讨 总被引:1,自引:0,他引:1
O3是一种氧化性很强的强氧化剂,具有良好的杀菌消毒和氧化降解污染物的能力,但固运行费用高而限制了其在水处理中的广泛应用。研究发现,超声可以通过超声粉碎作用,增加单位时间内O3的浓度;超声空化效应产生高能条件,促使O3空化泡中的O3直接快速的分解,产生自由基;超声空化效应促使O3分解产生氧化性强的H2O2。 相似文献
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The ESR spectra of microcrystalline cellulose and purified cotton cellulose reacted with ceric ammonium nitrate in nitric acid were determined. The effects of the concentration of ceric ion, atmosphere, temperature, and graft copolymerization with acrylonitrile on the rates of formation and decay of radicals in the cellulose molecule were determined under both static and dynamic conditions. Under static conditions, after the desired conditions of reaction, the samples were frozen at –100 or –160°C., and then the concentration of free radicals was determined. Under dynamic conditions ceric ion solution was continuously flowed through the celluloses while these determinations were being made at 25°C. In the presence of oxygen the rate of decay of free radicals was decreased. On initiation of copolymerization reactions with acrylonitrile, there was an increase in radical concentration, then a decrease. Apparently, during graft copolymerization the radical site initially on the cellulose molecule was retained on the end of the growing polymer chain. Then additional ceric ion coordinated with the hydroxyl groups of the cellulose, leading to the formation of additional radical sites. An Arrhenius interpretation of the effect of temperature on the formation of these additional radical sites gave apparent activation energies for radical formation on cotton cellulose as 34 kcal./mole and on microcrystalline cellulose as 29 kcal./mole. 相似文献
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To determine the effects and relative importance of process variables in coal liquefaction, a uniquely designed and fabricated high-pressure/high-temperature electron spin resonance (e.s.r.) apparatus is used to monitor the in-situ formation and behaviour of free radicals, which are generally assumed to be the key factor. It is concluded that the temperature is the most significant single process variable that affects free radical formation; for Powhatan No. 5 coal there is a 9-fold increase in going from 400 to 460 °C. At 460 °C the other process variables tested can affect significantly the free radicals significantly, but at 400 °C these variables have essentially no effect on free radicals formation. The next most significant effect is due to the combination of solvent nature and residence time. Tetralin and the SRC-II heavy distillate quench the free radicals from Powhatan No. 5 to the same extent with one significant difference. In tetralin the maximum concentration is observed shortly after the slurry achieves its highest temperature, whereas in the SRC-II heavy distillate experiments the concentration is still increasing, at 460 °C, even after 1 h of reaction. The heating time, pressures and types of gas used affect the free radical concentration to a much smaller extent. The conversions obtained in the in-situ e.s.r. experiments using SRC-II heavy distillate as the solvent are somewhat lower than those obtained with tetralin as the solvent. The corresponding oil yields with tetralin are considerably higher than with SRC-II heavy distillate. 相似文献
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为了研究全氟己酮对航空煤油燃烧的抑制作用,将杯式燃烧器的燃烧方式由液面燃烧改为灯芯燃烧,解决了气体灭火剂灭火性能测试中较高闪点燃料难以点燃的问题。通过实验可知,随着空气中全氟己酮浓度的增加,航空煤油的燃烧经历了火焰先缓慢增高再迅速降低的过程,可见全氟己酮在不同浓度下对燃烧的作用存在由促进到抑制的转变。为深入探索这一转变的原因,基于化学动力学构建了1403个组分、7496个反应组成的全氟己酮抑制RP-3航空煤油燃烧机理并进行了验证。通过化学动力学分析可知全氟己酮在低温下对燃烧的抑制比在高温下的效果更好,全氟己酮在低浓度时温度升高导致抑制作用减弱主要是源于温度升高后,促进燃烧的反应提速幅度远大于其他反应;全氟己酮降低RP-3航煤燃烧温度的途径之一是通过热分解等吸热反应来实现的;随着全氟己酮浓度的增大,反应路径发生变化,使得H、O和OH自由基的生成量减少、消耗量大量增多,宏观上体现出全氟己酮作为燃料的促进燃烧的作用减弱、作为灭火剂抑制燃烧的作用增强。研究结果可为利用全氟己酮防控航空煤油火灾提供理论指导,为研制新型灭火剂提供参考。 相似文献
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Recycling of lignocellulosics filled polypropylene composites. I. Analysis of thermal properties,morphology, and amount of free radicals 下载免费PDF全文
Dominik Paukszta Ewa Markiewicz Adam Ostrowski Beata Doczekalska Magdalena Brzyska Marek Szostak Sławomir Borysiak 《应用聚合物科学杂志》2015,132(12)
Composites of isotactic polypropylene filled with comminuted rapeseed straw are studied. Improvement in interfacial adhesion is achieved by chemical modification of the lignocellulose filler. Composites were subjected to recycling by extrusion. The effect of multiple recycling of the composites on the process of nucleation and crystallization of polypropylene matrix, surface topography, and free radical generation was checked. On the basis of differential scanning calorimetry data, a significant influence of the recycling on nucleation activity of the lignocellulose filler was evidenced. A relation between the filler particle size and multiple recycling was established by observations under a polarization microscope, while scanning electron microscope analyses confirmed the positive effect of chemical modification of rapeseed straw on the interfacial adhesion. The composite structure changes forced by multiple recycling are discussed in the context of free radical generation. Concentration of free radicals in the rapeseed straw samples and composites was measured by the electron paramagnetic resonance spectroscopy to show that it was higher in the systems subjected to multiple recycling. Interestingly, the composites after multiple recycling showing elevated concentration of free radicals are also characterized by higher nucleation activity. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41693. 相似文献