十四种化合物的抗氧化活性

本文以抑制硫代巴比妥酸反应物的生成为指标,测定了十四种化合物的抗氧化活性,并估测了其中十一种化合物与-OH反应的动力学常数,发现它们的量效关系为:1.抗氧化活性与浓度成直线相关性,按其抗氧化活性由大到小排列顺序如下:N、N-二乙基硫代氨甲酸钠;4-羟基桂皮酸二乙胺基乙基醋盐酸盐;1-色氨酸;S,2(3-氨基丙基氨基)乙基硫代磷酸;S,2-氨基乙基异硫脲盐酸盐:dl-蛋氨酸;dl-组氨酸;乙醇:烟酰胺;柠檬酸钠;甘氨酸.2.抗坏血酸与1-半胱氨酸低浓度时促氧化,高浓度时抗氧化.3.还原性谷胱甘肽其抗氧化活性与浓度的关系成指数型.     

基于ORAC评价多酚类化合物抗氧化活性

采用氧自由基清除能力(ORAC)方法考察20种多酚类化合物的抗氧化活性。结果表明,该方法具有较优的线性关系(R2=0.997）;检测限(LOD）和定量限(LOQ）为0.5～3.1 μmol·L-1,精密度＜18%,准确度91%～105%。比较20种多酚类化合物抗氧化活性,对羟基苯甲酸类化合物中,鞣花酸和没食子酸具有较强的抗氧化活性;对羟基肉桂酸类以咖啡酸及其衍生物抗氧化活性最高;在类黄酮组分中,黄烷-3-醇表现出优良的抗氧化特性,黄酮醇次之。ORAC可作为评价多酚类化合物抗氧化的简便、高效的标准化检测方法。     

丹参醌化合物结构特征与抗氧化活性

对双氢丹参醌I和丹参醌Ⅱ在油脂中的抗氧化作用及构效关系进行了量子化学研究。结果表明 ,抗氧化剂与油脂中碳中心自由基 (R· )复合成稳定自由基 (AH -R· ) ,可能是丹参醌抑制或阻止油脂氧化酸败的主要途径 ,双氢丹参醌I也可借助释放活泼H(本身转化成稳定自由基A· )有效清除R·。丹参醌分子本身的化学活性和对应的AH -R·与A·的稳定性对此类抗氧化作用有重要影响。AH -R·和A·中自旋集居分布 ,对比较抗氧化剂的相对活性可能是一个有价值的电子结构参数。     

山奈酚抑制蛋白激酶CK2活性

研究体外以及HL-60细胞内山奈酚对蛋白激酶CK2的抑制作用及机制. 通过测定药物作用后转移到CK2底物上的[γ-32P]ATP的32P的放射性活度, 探讨山奈酚对重组人CK2全酶以及细胞内CK2活性的影响; 采用多重RT-PCR检测CK2α、α' 和 β亚基的mRNA表达水平; 通过 Lineweaver-Burk作图法,分析CK2的酶动力学机制.山奈酚能显著抑制重组人CK2活性（IC50 = 1.88 μmol/L）和HL-60细胞内的CK2活性, 对细胞内CK2的作用效果强于阳性对照四溴-2-氮杂苯并咪唑(TBB). 山奈酚作用2h,对CK2各亚基的mRNA表达水平均没有影响. 山奈酚对重组人CK2的酶动力学分析表明, 山奈酚与ATP(Ki = 1.14 μmol/L)及酪蛋白(Ki = 1.03 μmol/L)均呈非竞争性抑制作用. 结果提示, 山奈酚是一种有效的蛋白激酶CK2的抑制剂, 其作用机制可能与其阻碍CK2与ATP以及底物的结合有关.     

藜叶中黄酮类化合物体外抗氧化活性研究

为了探讨藜叶中黄酮类化合物的体外抗氧化活性,采用有机溶剂提取法和色谱柱法对藜叶中化学成分进行提取与分离;以Vc作对照,对分离纯化的芦丁、乙酸乙酯浸膏和正丁醇浸膏进行DPPH·、O2^-·和·OH的清除效果试验。结果表明：三者对DPPH·、O2^-·、·OH均具有清除作用,且与浓度呈量效关系,芦丁对·OH清除效果优于Vc,芦丁具有较强的清除DPPH·能力,其IC50为0．05μg／mL。     

两种测定化合物对真菌菌丝生长抑制活性方法的比较

采用带毒平板法和液体培养法测定两种植物抗菌化合物血根碱和白屈菜红碱对植物病原真菌水稻纹枯病菌（Rhizoctonia solani）、番茄枯萎病菌（Fusarium oxysporium f．sp．lycopersici）和棉花枯萎病菌（F.oxysporium f.sp．vasinfectum）的抑制活性。论文对两种测定方法进行了比较和讨论,结果发现：和带毒平板法相比,采用液体培养法获得的化合物半抑制浓度要低。     

甘草黄酮类化合物对酪氨酸酶单酚酶的抑制

研究了甘草中四种黄酮类化合物甘草甙、异甘草素．葡萄糖芹菜甙、异甘草甙和甘草查耳酮甲对酪氨酸酶单酚酶活性的抑制。结果表明异甘草素-葡萄糖芹菜甙、异甘草甙和甘草查耳酮甲的IC50分别为0．072mM,,0．038mM,0.0258mM,它们都属于竞争性抑制剂,甘草甙没有抑制活性。研究表明,异甘草素．葡萄糖芹菜甙、异甘草甙和甘草查耳酮甲可以作为潜在的美白化妆品添加剂。     

艾纳香中的黄酮类化合物及其抗氧化与α-葡萄糖苷酶抑制活性研究

本文对艾纳香Blumea balsamifera DC.叶中的黄酮类成分及其抗氧化与α-葡萄糖苷酶抑制活性进行了研究。从艾纳香叶中分离得到9个黄酮类化合物,分别鉴定为:4'-甲氧基二氢槲皮素(1),柽柳黄素(2),3,3'-二甲氧基槲皮素(3),7,4'-二甲氧基二氢槲皮素(4),(2α,3β)-二氢鼠李素(5),艾纳香素(6),sterubin(7),enodicytol(8),二氢槲皮素(9)。化合物3、5、8为首次从艾纳香中分离得到。分别用DPPH法和PNPG法筛选化合物的抗氧化活性及α-葡萄糖苷酶抑制活性。结果表明化合物2、5~9表现出强抗氧化活性;化合物1~3、5、9表现有较高的α-葡萄糖苷酶抑制活性。该结果为艾纳香的品质评价和深度开发利用提供了理论依据。     

响应面分析法优化豆粕固态发酵工艺生产大豆抗氧化肽的研究

分别以总抗氧化活性(T-AOC)和多肽含量为评价指标,通过单因素实验分析和Box-Behnken响应面分析法对豆粕固态发酵工艺条件进行优化,得到最佳发酵工艺条件为:接种量9.6%,料水比1∶0.9,发酵温度35℃。豆粕在此条件下发酵48h,其总抗氧化活性与多肽含量分别由发酵前的207.2U/g和21.0mg/g提高到1091.1U/g和347.7mg/g,分别提高了4.3倍和15.6倍,与预测值相比,结果吻合性良好。总抗氧化活性与多肽含量的相关性良好(R2=0.8604),表明得到的多肽为抗氧化肽。     

The oxidative damage of plasmid DNA by ascorbic acid derivatives in vitro: the first research on the relationship between the structure of ascorbic acid and the oxidative damage of plasmid DNA

To study the structure-function relationship of the oxidative-damage effect of ascorbic acid, we have focused on the interaction between plasmid DNA pUC19 and a series of ascorbic acid derivatives modified on different OH groups in the presence of transition metal ions. Some ascorbic acid derivatives can selectively cleave plasmid DNA from Form I to Form II in the presence of low concentration of Cu2+ just like ascorbic acid itself, while other derivatives oxidatively damage plasmid DNA slightly. We found that those derivatives with unattached 2-OH and 3-OH groups retain the ability to cleave the plasmid DNA. The derivatives that have been methylated on 2-OH or 3-OH can only cleave plasmid DNA softly, and those derivatives that have been protected on both 2-OH and 3-OH can hardly exert an oxidative damage on plasmid DNA under the same condition. Form these results, we can draw the conclusion that 2-OH and 3-OH groups of the ascorbic acid molecule contribute most to this biological activity.     

热休克对小白鼠组织中抗氧化酶活性的影响

热休克诱导小白鼠心、肝、肾、肺、脑等组织细胞SOD活性非常显著或显著升高,其中主要诱导CuZn-SOD的生物合成;42℃诱导小白鼠各组织细胞CAT活性极显著下降,正常情况下,脑细胞几乎不存在CAT活性,42℃热休克20min诱导脑CAT活力升高;热休克亦诱导各组织cSH-Px活性变化,心、脑细胞GSH-Px极显著升高,对肺的影响较小。SOD、CAT、GSH-Px协同作用,维持机体正常生理机能。还探讨了热休克应答、热耐受能力的获得与抗氧化酶活性变化存在的对应关系。     

不同南瓜多糖体外清除羟基自由基作用的研究

采用热水浸提法和超声波辅助法提取南瓜粗多糖,用十六烷基三甲基溴化铵(CTAB)络合沉淀得AP1多糖;用邻二氮菲-金属铁离子-H2O2体系检测南瓜多糖对羟基自由基的清除作用。结果表明,南瓜多糖能有效清除羟基自由基,并随着浓度的增加清除作用加强,且热水提取的南瓜多糖对羟基自由基清除作用显著高于超声提取的南瓜多糖。该结果表明南瓜多糖具有抗氧化性,并且热水提取的南瓜多糖的清除羟基自由基最为显著。     

球孢白僵菌不同菌株清除自由基活性评价

选择不同来源的12株球孢白僵菌,分别测定菌丝体2种溶剂提取物在不同抗氧化模型中的抗氧化作用。结果表明,不同溶剂提取物对二苯基苦味酰基苯肼自由基(DPPH)和羟自由基(.OH)均有清除作用,但是清除自由基的活性不同,乙酸乙酯提取物对.OH的清除作用最为显著,活性较高,最高清除率达到71.54%。甲醇提取物活性均较低,30 min时甲醇提取物对DPPH和.OH清除率最高分别为36%和38.96%,12株白僵菌间的清除自由基活性有较大的差异。     

脱氧核糖核酸对机体内超氧化物岐化酶和过氧化物酶活性影响初步研究

超氧化物岐化酶（SOD）和过氧化物酶（POD）是机体内重要的抗氧化酶系之一,其作用在于消除体内的自由基,防止自由基对细胞结构的损伤。它们的活性随增龄而下降,因此自由基不断损伤细胞结构,累积最终导致细胞衰亡和动物机体衰老,老龄小鼠服用DNA一段时间后,其体内SOD和POD的活性均显著提高,因而其衰老速度可能得到一定程度的延缓。     

Biochemical Analyses of the Antioxidative Activity and Chemical Ingredients in Eight Different Allium Alien Monosomic Addition Lines

We measured the antioxidant contents and antioxidative activities in eight Allium fistulosum–shallot monosomic addition lines (MAL; FF+1A–FF+8A). The high antioxidative activity lines (FF+2A and FF+6A) showed high polyphenol accumulation. These additional chromosomes (2A and 6A) would therefore have anonymous genes related to the upregulation of polyphenol production, the antioxidative activities consequently being increased in these MALs.     

Enhancement of the Tolerance to Oxidative Stress in Cucumber (Cucumis sativus L.) Seedlings by UV-B Irradiation: Possible Involvement of Phenolic Compounds and Antioxidative Enzymes

Cucumis sativus L.) seedlings were irradiated or not irradiated with UV-B for several days in environment-controlled growth chambers. The first leaves irradiated with UV-B were retarded in growth but simultaneously acquired a remarkably high tolerance to oxidative stress, as induced by paraquat treatment, compared with the non-irradiated leaves. This enhanced tolerance was observed within 1d after the start of UV-B irradiation and was maintained during the 12 d period of UV-B treatment. The effects of UV-B on several antioxidative enzymes were examined, and activities of superoxide dismutase, ascorbate peroxidase and guaiacol peroxidase, but not of glutathione reductase, were found to be enhanced. However, activation of these enzymes occurred only from 6 d after the start of irradiation. In contrast, accumulation of phenolic compounds was observed within 1d after the start of UV-B irradiation. HPLC analysis of phenolic compounds showed the distinct enhancement of a substance, which may have antioxidative properties in cucumber seedlings irradiated with UV-B. On the basis of these results, we conclude that not only antioxidative enzymes but also other factors in cucumber seedlings irradiated with UV-B, such as phenolic compounds, may participate in the enhanced tolerance to oxidative stress. Received 10 June 2000/ Accepted in revised form 1 July 2000     

Isoform-selective Genetic Inhibition of Constitutive Cytosolic Hsp70 Activity Promotes Client Tau Degradation Using an Altered Co-chaperone Complement

The constitutively expressed heat shock protein 70 kDa (Hsc70) is a major chaperone protein responsible for maintaining proteostasis, yet how its structure translates into functional decisions regarding client fate is still unclear. We previously showed that Hsc70 preserved aberrant Tau, but it remained unknown if selective inhibition of the activity of this Hsp70 isoform could facilitate Tau clearance. Using single point mutations in the nucleotide binding domain, we assessed the effect of several mutations on the functions of human Hsc70. Biochemical characterization revealed that one mutation abolished both Hsc70 ATPase and refolding activities. This variant resembled the ADP-bound conformer at all times yet remained able to interact with cofactors, nucleotides, and substrates appropriately, resembling a dominant negative Hsc70 (DN-Hsc70). We then assessed the effects of this DN-Hsc70 on its client Tau. DN-Hsc70 potently facilitated Tau clearance via the proteasome in cells and brain tissue, in contrast to wild type Hsc70 that stabilized Tau. Thus, DN-Hsc70 mimics the action of small molecule pan Hsp70 inhibitors with regard to Tau metabolism. This shift in Hsc70 function by a single point mutation was the result of a change in the chaperome associated with Hsc70 such that DN-Hsc70 associated more with Hsp90 and DnaJ proteins, whereas wild type Hsc70 was more associated with other Hsp70 isoforms. Thus, isoform-selective targeting of Hsc70 could be a viable therapeutic strategy for tauopathies and possibly lead to new insights in chaperone complex biology.