桃叶珊瑚甙的体外抗氧化研究

研究了桃叶珊瑚甙对化学体系中产生的自由基的清除作用以及桃叶珊瑚甙对组织匀浆、线粒体、微粒体氧化损伤的保护作用．以Fenton反应和邻苯三酚自氧化反应产生自由基。分光光度法检测．结果显示，桃叶珊瑚甙有较强的清除自由基作用，对组织细胞及亚细胞膜性结构的氧化损伤有较好的保护作用．     

傣族药皇旧提取物清除活性氧及抗氧化作用研究

利用Fenton反应、光照核黄素产生活性氧自由基·OH、O2,分光光度法研究了傣族药皇旧(旱莲草)提取物体外清除·OH、O2的作用.通过硫代巴比妥分光光度法研究皇旧提取物·OH引起的DNA氧化损伤的保护作用.实验结果表明皇旧提取物能有效清除·OH、O2自由基,对DNA的·OH氧化损伤有显著抑制作用.     

几种天然抗氧化剂对DNA氧化损伤的保护作用

人体在正常情况下是处于氧化．还原平衡状态的，当这种平衡被破坏，如因为体内或外界的原因引起体内自由基浓度升高，将导致生物大分子过氧化如DNA的氧化性损伤，进而引起各种疾病．目前大量的研究表明，人类的多种疾病与自由基有关，如各种炎症、癌症、自身免疫疾病、糖尿病、各种心脑血管疾病、老年性痴呆等．因此，提高抗氧化剂的摄入可能能够降低这类疾病的发生，这就是目前提出的“抗氧化剂治疗”说．合成抗氧化剂如在食品中广泛使用的二丁羟基茴香醚（BHT）和丁羟基茴香醚（BHA）由于其潜在的毒性和致癌作用被人们所排斥．     

用化学发光法研究谷胱甘肽对羟自由基氧化鸟嘌呤的保护作用

利用鸟嘌呤-过氧化氢-钴（Ⅱ）化学发光体系，结合流动注射技术研究了生物活性物质谷胱甘肽（GSH）对羟自由基氧化鸟嘌呤的保护作用．实验结果表明，GSH明显抑制鸟嘌呤的化学发光，且抑制率与GSH浓度成量效关系，达到50％抑制率的GSH浓度为6．5mg／L．该方法为进一步研究DNA的抗氧化损伤机制提供了有效的研究手段．     

4种植物多酚对生物大分子的保护作用

为了研究多酚类化合物对生物大分子氧化损伤的保护作用,采用MDA测定、SDSPAGE、琼脂糖电泳,检测了4种多酚对由自由基引起的脂质过氧化、蛋白质氧化降解、DNA断裂的保护作用.结果表明:槲皮素在抑制脂质过氧化中作用最突出,在保护蛋白质氧化降解中香草醛作用最强;芦丁在保护DNA的氧化性损伤中最有效.说明4种化合物在不同的抗氧化体系中有不同的活性.     

几种植物化学物粗提物体外抗DNA氧化损伤功能的检测

近年来,植物化学物功能开发备受关注,其粗提物有效生理功能快速筛选方法成为制约保健食品开发速度的一个重要因素.以CuSO4-Phen-Vc-H2O2-DNA化学发光体系为基本检测手段,调整检测条件,分别对竹叶提取物、黑加仑提取物、葡萄籽提取物进行了体外抗DNA氧化损伤功能的筛选.结果提示葡萄籽提取物具有良好的抗DNA氧化损伤功能,在5-25mg/L呈现剂量效应关系(r=0.97,P<0.01).竹叶提取物在400mg/L表现为一定的抗DNA氧化损伤功能.但其仅表现为延缓自由基的生成,并不能阻止DNA的氧化损伤,而黑加仑提取物则表现为促进DNA氧化损伤.由此可见CuSO4-Phen-vc-H2-O2-DNA化学发光体系可以作为植物化学物.甚至粗提物抗DNA氧化损伤功能检测的一个快速、经济、有效的方法.葡萄籽提取物可作为良好的保健食品资源,竹叶提取物则需慎重,黑加仑提取物不能作为保健食品资源直接利用.     

荭草素和异荭草素抗氧化活性及对肝癌细胞增殖的影响

采用荭草素和异荭草素标准品，通过测定两者对DPPH·、ABTS+·、H2O2、·OH自由基的清除率，脂质过氧化，Cu2+/H2O2诱导的牛血清蛋白-BSA-和DNA氧化损伤及BSA蛋白羰基化的抑制作用来评价二者的抗氧化活性，另外用MTT法评价了二者对人肝癌-HepG2-细胞生长的影响. 结果表明，荭草素和异荭草素均可清除自由基，抑制脂质过氧化、BSA和DNA氧化损伤和BSA羰基化，且一定浓度范围内异荭草素的抗氧化活性强于荭草素；另外荭草素和异荭草素可显著抑制HepG2细胞增殖，并呈浓度和时间依赖性，且异荭草素的抑制率高于荭草素，说明异荭草素是优于荭草素的有抗癌功效的天然抗氧化剂.     

山刺玫果实清除羟自由基及抗DNA损伤作用的实验研究

目的研究山刺玫果实乙醚提取物、水提取物、乙酸乙酯提取物及原汁清除羟自由基(@OH)及保护DNA氧化损伤的作用.方法采用现代生物化学发光分析技术,以CuSO4-VitC-H2O2-酵母菌发光体系测定山刺玫提取物对@OH的清除作用.结果山刺玫原汁和乙酸乙酯提取物对@OH具有清除作用,并能保护DNA的氧化损伤,作用强度与浓度之间存在正比关系.结论山刺玫原汁、乙酸乙酯提取物具有清除@OH及抗DNA损伤的作用.     

抗氧化剂的体外化学发光分析

ＤＮＡ 氧化损伤可导致多种类型疾病的产生, 并可能与细胞的衰老过程直接相关． 体内自由基代谢和清除失衡将致使ＤＮＡ氧化损伤增加, ＤＮＡ 修复能力下降． 内源和外源性的抗氧化剂可清除过多的自由基, 使ＤＮＡ免受损伤． 抗氧化作用是一个很复杂的反应, 药物抗氧化能力的大小取决于其夺氢反应、还原作用及生成自由基的稳定性等诸因素． 本文采用Ｐｈｅｎ － Ｃｕ － ＶＣ－ Ｈ２Ｏ２ － ＤＮＡ体外化学发光体系, 研究了多种抗氧化剂对ＤＮＡ 损伤的保护作用, 并对其药物结构与抗氧化能力进行了分析．     

维生素C和维生素E的联合抗氧化活性研究

维生素C和维生素E具有多种生理活性,也是抗氧化剂,二者联合作用的生化机理研究鲜见报道.本文采用铁氰化钾法、甲基紫法、邻苯三酚自氧化法和DMPD法,检测了维生素C和维生素E单独及联合作用后的还原力、对DMPD·+自由基、羟自由基和超氧阴离子的清除能力;采用SDS-PAGE法和SCGE法检测了二者对蛋白质和细胞DNA氧化损伤的保护作用.结果表明,维生素C和维生素E在各个体系中具有较强的作用,并呈浓度依赖性.维生素C在还原能力、清除自由基能力方面比维生素E强,二者的联合作用大多强于单独作用,表现出一定的协同增效作用.同时,维生素C和维生素E在AAPH引起的蛋白质氧化损伤中也有很好的保护作用,二者联合后作用效果更明显,但在对细胞DNA的氧化损伤中未见协同保护作用.     

体外培养人角膜内皮细胞的UVB损伤及抗坏血酸的抗氧化保护作用研究

以非转染人角膜内皮(HCE)细胞系为体外实验模型系统研究了UVB氧化损伤、Asc抗氧化保护及其分子机理。体外培养的HCE细胞经UVB和/或Asc处理后,利用MTT和光镜对细胞的活力和形态进行了检测,利用8-羟基脱氧鸟苷免疫荧光染色对DNA的氧化损伤进行了检测,并利用二氢乙啶染色对胞内活性氧(ROS)的水平进行了检测。结果显示,100~800 mj/cm²的UVB辐射能剂量和时间依赖性地损伤HCE细胞的活力;200 mj/cm² UVB(自然太阳光中的平均辐射剂量)能引起HCE细胞发生皱缩,并显著增加细胞的DNA氧化损伤程度及胞内ROS水平;而1 mmol/L Asc不仅能显著增强HCE细胞的活力、促进细胞分裂,而且还能显著降低200 mj/cm² UVB所引起的DNA氧化损伤及胞内ROS水平。综上所述,UVB通过诱导ROS的产生进而引起DNA氧化损伤,对HCE细胞具有显著的氧化损伤作用;而Asc能够通过降低UVB诱导的ROS水平进而保护DNA免受氧化损伤,对HCE细胞的UVB损伤具有一定的抗氧化保护作用。本文研究结果对于利用Asc等抗氧化保护剂保护HCE细胞免受UVB氧化损伤具有一定的理论指导价值。     

Human and bacterial oxidative demethylases repair alkylation damage in both RNA and DNA

Repair of DNA damage is essential for maintaining genome integrity, and repair deficiencies in mammals are associated with cancer, neurological disease and developmental defects. Alkylation damage in DNA is repaired by at least three different mechanisms, including damage reversal by oxidative demethylation of 1-methyladenine and 3-methylcytosine by Escherichia coli AlkB. By contrast, little is known about consequences and cellular handling of alkylation damage to RNA. Here we show that two human AlkB homologues, hABH2 and hABH3, also are oxidative DNA demethylases and that AlkB and hABH3, but not hABH2, also repair RNA. Whereas AlkB and hABH3 prefer single-stranded nucleic acids, hABH2 acts more efficiently on double-stranded DNA. In addition, AlkB and hABH3 expressed in E. coli reactivate methylated RNA bacteriophage MS2 in vivo, illustrating the biological relevance of this repair activity and establishing RNA repair as a potentially important defence mechanism in living cells. The different catalytic properties and the different subnuclear localization patterns shown by the human homologues indicate that hABH2 and hABH3 have distinct roles in the cellular response to alkylation damage.     

活性氧对生物大分子的氧化性损伤

活性氧在生物大分子如ＤＮＡ、蛋白质等氧化性损伤中起着非常重要的作用,本综述了活性氧的产生和氧化作用以及活性氧与一些病理过程的关系,对深入探讨生物大分子损伤的生物化及有关病理学机理具有一定的理论和应用意义。     

Inducible repair of oxidative DNA damage in Escherichia coli

Hydrogen peroxide is lethal to many cell types, including the bacterium Escherichia coli. Peroxides yield transient radical species that can damage DNA and cause mutations. Such partially reduced oxygen species are occasionally released during cellular respiration and are generated by lethal and mutagenic ionizing radiation. Because cells live in an environment where the threat of oxidative DNA damage is continual, cellular mechanisms may have evolved to avoid and repair this damage. Enzymes are known which evidently perform these functions. We report here that resistance to hydrogen peroxide toxicity can be induced in E. coli, that this novel induction is specific and occurs, in part, at the level of DNA repair.     

OGG1 initiates age-dependent CAG trinucleotide expansion in somatic cells

Although oxidative damage has long been associated with ageing and neurological disease, mechanistic connections of oxidation to these phenotypes have remained elusive. Here we show that the age-dependent somatic mutation associated with Huntington's disease occurs in the process of removing oxidized base lesions, and is remarkably dependent on a single base excision repair enzyme, 7,8-dihydro-8-oxoguanine-DNA glycosylase (OGG1). Both in vivo and in vitro results support a 'toxic oxidation' model in which OGG1 initiates an escalating oxidation-excision cycle that leads to progressive age-dependent expansion. Age-dependent CAG expansion provides a direct molecular link between oxidative damage and toxicity in post-mitotic neurons through a DNA damage response, and error-prone repair of single-strand breaks.     

Oxidative demethylation by Escherichia coli AlkB directly reverts DNA base damage

Methylating agents generate cytotoxic and mutagenic DNA damage. Cells use 3-methyladenine-DNA glycosylases to excise some methylated bases from DNA, and suicidal O(6)-methylguanine-DNA methyltransferases to transfer alkyl groups from other lesions onto a cysteine residue. Here we report that the highly conserved AlkB protein repairs DNA alkylation damage by means of an unprecedented mechanism. AlkB has no detectable nuclease, DNA glycosylase or methyltransferase activity; however, Escherichia coli alkB mutants are defective in processing methylation damage generated in single-stranded DNA. Theoretical protein fold recognition had suggested that AlkB resembles the Fe(ii)- and alpha-ketoglutarate-dependent dioxygenases, which use iron-oxo intermediates to oxidize chemically inert compounds. We show here that purified AlkB repairs the cytotoxic lesions 1-methyladenine and 3-methylcytosine in single- and double-stranded DNA in a reaction that is dependent on oxygen, alpha-ketoglutarate and Fe(ii). The AlkB enzyme couples oxidative decarboxylation of alpha-ketoglutarate to the hydroxylation of these methylated bases in DNA, resulting in direct reversion to the unmodified base and the release of formaldehyde.     

Oxidative stress on plasmid DNA induced by inhalable particles in the urban atmosphere

Plasmid DNA assay is a newly-developed in vitro method to investigate bioreactivity of particles. In this paper, this method was used to study the bioreactivity of PM10 (particulate matter with aerodynamic diameter of less than 10 μm) and PM2.5 (particulate matter with aerodynamic diameter of less than 2.5 μm). Samples and dust storm particles were collected in 2001 in an urban area, a satellite city and a clean air area in Beijing. A big difference was found for oxidative DNA stress induced by different particulate matter (PM) samples, with the TM50 (particle mass causing 50% damage to DNA) values varying by a factor over 10. This was closely dependent on the sizes of particles as well as the variation in relative proportion of mineral matter. PM2.5 samples generally impose larger oxidative stress on plasmid DNA than PM10 samples. Airborne particles collected during dust storm episodes, usually with a higher proportion of mineral matter, have a much lower oxidative capacity than those collected during non-dust storm episodes. PM samples and their water-soluble fractions usually have similar bioreactivities, demonstrating that oxidative capacity of Beijing airborne particles is mainly sourced from their water-soluble fractions.     

葡萄籽粗多糖的体内外抗氧化作用

为了研究葡萄籽粗多糖(crude polysaccharides from grape seeds,GSCPs)体外抗氧化作用及对秀丽隐杆线虫的体内抗氧化作用,采用水提醇沉法提取GSCPs,检测GSCPs对1,1-二苯基-2-三硝基苯肼(1,1-diphenyl-2-picrylhydrazyl,DPPH)自由基和羟自由基的清除作用及对DNA氧化损伤的抑制作用;建立RAW 264.7巨噬细胞氧化损伤模型,在细胞水平探讨GSCPs的抗氧化能力;同时利用秀丽隐杆线虫研究GSCPs的体内抗氧化功能。体外实验结果表明:GSCPs可有效清除自由基,抑制DNA的氧化损伤,质量浓度为0.4mg/mL的GSCPs对DPPH自由基的清除率达84%,对羟自由基清除率为89%;GSCPs可以下调H₂O₂诱导的RAW 264.7巨噬细胞活性氧(reactive oxygen species,ROS)水平,正向调节细胞内超氧化物歧化酶(superoxide dismutase,SOD)和谷胱甘肽过氧化物酶(glutathione peroxidase,GSH-Px)活性,质量浓度为0.2mg/mL的GSCPs处理组可使细胞内SOD活性从H₂O₂处理组的81.1%升至96.3%,GSH-Px活性从H₂O₂处理组的92.1%升至99.6%。此外,GSCPs可延长秀丽隐杆线虫寿命,提高其对抗急性氧化应激的能力,有效清除秀丽隐杆线虫体内的ROS。质量浓度为0.8mg/mL GSCPs处理组秀丽隐杆线虫的平均寿命较对照组延长27.67%,将急性氧化应激的秀丽隐杆线虫平均存活时间延长33.58%,秀丽隐杆线虫体内ROS生成量较对照组可降低56.33%。因此,葡萄籽粗多糖在体内外均表现出良好的抗氧化性,可用于抗氧化功能产品的开发。