Free Radical Scavenging and Cellular Antioxidant Properties of Astaxanthin

Astaxanthin is a coloring agent which is used as a feed additive in aquaculture nutrition. Recently, potential health benefits of astaxanthin have been discussed which may be partly related to its free radical scavenging and antioxidant properties. Our electron spin resonance (ESR) and spin trapping data suggest that synthetic astaxanthin is a potent free radical scavenger in terms of diphenylpicryl-hydrazyl (DPPH) and galvinoxyl free radicals. Furthermore, astaxanthin dose-dependently quenched singlet oxygen as determined by photon counting. In addition to free radical scavenging and singlet oxygen quenching properties, astaxanthin induced the antioxidant enzyme paroxoanase-1, enhanced glutathione concentrations and prevented lipid peroxidation in cultured hepatocytes. Present results suggest that, beyond its coloring properties, synthetic astaxanthin exhibits free radical scavenging, singlet oxygen quenching, and antioxidant activities which could probably positively affect animal and human health.     

自由基聚合引发剂研究进展

自由基聚合是大规模生产各种烯类聚合物的有效方法，在工业生产中，约70％以上的烯类聚合物都是通过自由基聚合来实现的。自由基聚合引发体系可归纳为过氧化物类引发剂、偶氮引发剂、二硫化物引发剂、氧化还原引发体系、双官能度及多官能度引发剂和大分子引发剂等。本文着重介绍近年来新发展起来的水溶性偶氰引发剂、双官能度及多官能度引发剂、大分子引发剂以及氧化还原引发剂的最新进展。     

HMX,CL-20和DNTF自由基的光照检测

为研究含能材料热分解过程的瞬间性和安全性,运用电子自旋共振技术(ESR)检测了HMX,CL-20和DNTF的自由基,得到了它们在相同的光照强度和时间间隔中,各体系的电子自旋共振谱图.结果表明,DNTF在没有光照的情况下即会产生自由基,HMX和CL-20光照一定时间后有自由基产生.随着光照时间的延长,自由基逐渐增多,DNTF的自由基信号最强.     

氨基葡萄糖-镝配合物的合成和抗羟自由基活性

用D-氨基葡萄糖盐酸盐与氯化镝反应,制备了氨基葡萄糖-镝配合物. 用元素分析、电导率、红外光谱、紫外光谱、X射线光电子能谱等分析测试手段对配合物进行了表征. 以EDTANa2×Fe(II)-H2O2体系产生羟自由基(×OH)研究氨基葡萄糖与氨基葡萄糖-镝配合物对羟自由基的清除作用. 结果表明,氨基葡萄糖与Dy3+形成了配合物,其中氨基葡萄糖氨基上的N和仲羟基的O及Cl-参与了配位. 该配合物对×OH均具有明显的清除作用,在浓度为2.5 mg/mL时对×OH的清除率达到85%,D-氨基葡萄糖对×OH的清除率达到77%. 各样品对×OH自由基的清除能力均随着质量浓度的增加而上升.     

原子转移自由基聚合的研究进展

概述了原子转移自由基聚合(ATRP)反应的机理、引发剂的组成、催化体系、适用单体、聚合温度、反应介质的近期研究进展;介绍了ATRP作为一种新材料合成技术的产业化前景及其存在的问题。     

7种茶氨酸类似物的合成及清除自由基活性

以L-谷氨酸为起始原料,经邻苯二甲酸酐保护、酰化开环、肼解脱保护等反应合成了7种茶氨酸类似物,结构经EA、IR、1HNMR、13CNMR和MS进行了确认,并测定了其清除DPPH自由基和羟自由基活性。结果表明:2-氨基-5-氧代-5-[(4-羟基苯基)氨基]戊酸清除自由基活性最强,0.002 mol/L时清除DPPH自由基率为90%,0.004 mol/L时清除羟自由基率达95%;2-氨基-5-氧代-5-[(4-氨基苯基)氨基]戊酸次之。由此可见,茶氨酸类似物中5位连有苯基或所连苯基对位有供电子基团时,可提高其清除DPPH自由基和羟自由基活性,且随对位所连基团供电性的提高,清除活性增强。     

自由基聚合表面改性纳米粒子的研究进展

自由基聚合是工业生产高分子产品的重要技术,也是制备聚合物/无机纳米复合材料时对纳米粒子表面改性的重要手段。综述了自由基聚合表面改性纳米粒子的研究进展。分别对普通自由基聚合和活性聚合表面改性纳米粒子机理和分类进行了归纳和总结。     

The Efficacy of Edaravone (Radicut), a Free Radical Scavenger,for Cardiovascular Disease

Edaravone was originally developed as a potent free radical scavenger, and has been widely used to treat acute ischemic stroke in Japan since 2001. Free radicals play an important role in the pathogenesis of a variety of diseases, such as cardiovascular diseases and stroke. Therefore, free radicals may be targets for therapeutic intervention in these diseases. Edaravone shows protective effects on ischemic insults and inflammation in the heart, vessel, and brain in experimental studies. As well as scavenging free radicals, edaravone has anti-apoptotic, anti-necrotic, and anti-cytokine effects in cardiovascular diseases and stroke. Edaravone has preventive effects on myocardial injury following ischemia and reperfusion in patients with acute myocardial infarction. Edaravone may represent a new therapeutic intervention for endothelial dysfunction in the setting of atherosclerosis, heart failure, diabetes, or hypertension, because these diseases result from oxidative stress and/or cytokine-induced apoptosis. This review evaluates the potential of edaravone for treatment of cardiovascular disease, and covers clinical and experimental studies conducted between 1984 and 2013. We propose that edaravone, which scavenges free radicals, may offer a novel option for treatment of cardiovascular diseases. However, additional clinical studies are necessary to verify the efficacy of edaravone.     

筛选和评价天然抗氧化剂的方法-DPPH法

从植物中筛选和提取天然抗氧化剂是食品科学研究的热点,用于筛选抗氧化剂、评价抗氧化活性的方法也随之增多。DPPH法是普遍采用的方法之一,此法使用稳定的自由基DPPH筛选抗氧化剂、评价抗氧化效果。本文对DPPH法的原理、操作过程、表示测定结果的方法及该法的特点及应用进行了概括,并对影响测定结果的因素进行了探讨。     

自由基氧化法处理乳化油废水实验研究

乳化油废水危害巨大,文章研究二氧化铅电极处理乳化油废水的最佳pH和处理时间等,以及在此基础上进行处理实际废水的初步研究。     

活性自由基聚合的新进展--原子转移自由基聚合

活性自由基聚合是目前高分子科学中最为活跃的研究领域之一，原子转移自由基聚合(ATRP)反应是实现活性聚合的一种颇为有效的途径．也是高分子化学领域的最新研究进展之一。ATRP的独特之处在于使用了卤代烷作引发剂，并用过渡金属催化剂或退化转移的方式，有效地抑制了自由基双基终止的反应。ATRP可以同时适用于非极性和极性单体，可以制备多种结构形式的、结构清晰的高分子化合物。可实现众多单体的活性／可控自由基聚合。介绍了ATRP的研究进展，包括ATRP反应的特点、聚合反应机理、应用、研究现状及前景展望。     

龙眼果皮不同方法提取物对自由基的清除作用

用超声波、微波、冷凝回流及常温浸泡4种方法,用φ(C2H5OH)=95%的乙醇提取龙眼果皮,分别得到超声波提取物(UE)、微波提取物(ME)、热提物(RE)和浸提物(DE)。然后采用二苯代苦味酰肼自由基(DPPH)法对不同质量浓度的各提取物进行了自由基清除实验。结果表明,龙眼果皮乙醇提取物对自由基有很强的清除作用,清除能力远远优于3,5-二叔丁基-4-羟基甲苯(BHT);不同的提取方法所得提取物对自由基的清除作用有显著差别,其中以ME的效果最佳,当其质量浓度为1.2 mg/mL时,最大清除率高达83.11%。     

Free Radical Polymerization of Acrylonitrile Using Potassium Peroxy Disulphate Initiator and a Phase Transfer Catalyst

Free radical polymerization of acrylonitrile with the di-site phase transfer catalyst 1,4-bis(tetramethylhexyl)ethylenediammonium bromide (TMHEDAB) was investigated using the water-soluble initiator PDS (potassium peroxydisulphate) and water-insoluble solvent ethylacetate in an aqueous-organic biphase system at 60±1°C under nitrogen atmosphere at fixed pH and ionic strength. Rp increased with the increase in concentration of the monomer, initiator and catalyst. The order of R_p, with respect to monomer and catalyst concentration was found to be unity and with respect to initiator was found to be 0.5. A suitable mechanism has been proposed and its significance was discussed. The polymers obtained were characterized by spectral studies such as FTIR, ¹H-NMR, XRD, DSC, and TGA.     

Molecular and Free Radical Products of Reactions of Nitrogen Dioxide with Polyvinylpyrrolidone

Abstract

The mechanism of reactions of nitrogen dioxide with polyvinylpyrrolidone at 295–363 K has been considered. The nature of the molecular and free radical products of reactions has been studied by UV and ESR spectroscopy. The main molecular products are nitrites and nitrozoamides. The formation of stable acylalkylnitroxyl and iminoxyl radicals was registered. The influence of the structural-physical modification of the polymer at filling by aerosil has been established on kinetics of the formation of radicals.     

新型自由基聚合引发剂在聚合物多元醇合成中的应用研究进展

详细介绍了新型自由基聚合引发剂偶氮二异丁酸二甲酯(AIBME)和过氧化-2-乙基己酸叔戊酯的性质、合成及其在聚合物多元醇(POP)生产中的应用情况.简要介绍了1-叔戊基偶氮-1-氰基环己烷、1,1′-偶氮双(1-氰基环己烷)、过氧化新戊酸叔戊酯和过氧化二碳酸二十四酯等引发剂在POP合成中的应用情况.这些新型引发剂虽然售价高于偶氮二异丁腈(AIBN),但总使用效果优于AIBN,因而是引发剂的发展方向.     

Evidence of the CH···O HydrogenBonding in Imidazolium-Based Ionic Liquids from Far-Infrared Spectroscopy Measurements and DFT Calculations

Knowledge of all the intermolecular forces occurring in ionic liquids (ILs) is essential to master their properties. Aiming at investigating the weaker hydrogen bonding in aprotic liquids, the present work combined computational study and far-infrared spectroscopy on four imidazolium-based ILs with different anions. The DFT calculations of the ionic couples, using the ωB97X-D functional and considering both the empirical dispersion corrections and the presence of a polar solvent, show that, for all samples, the lowest energy configurations of the ion pair present H atoms, directly bound to C atoms of the cation and close to O atoms of the anion, capable of creating moderate to weak hydrogen bonding with anions. For the liquids containing anions of higher bonding ability, the absorption curves generated from the calculated vibrational frequencies and intensities show absorption bands between 100 and 125 cm⁻¹ corresponding to the stretching of the hydrogen bond. These indications are in complete agreement with the presently reported temperature dependence of the far-infrared spectrum, where the stretching modes of the hydrogen bonding are detected only for samples presenting a moderate interaction and become particularly prominent at low temperatures. Moreover, from the analysis of the infrared spectra, the occurrence of various phase transitions as a function of temperature was detected, and the difference in the average energy between the H-bonded and the dispersion-governed molecular configurations was evaluated.     

Inhibition of Baculoviral Disease by Plant-Mediated Peroxidase Activity and Free Radical Generation

The susceptibility of noctuid larvae to baculoviral infection is markedly affected by phytochemicals ingested during the acquisition of viral inoculum on foliage. We hypothesized that a major process causing phytochemical inhibition of viral disease is phenolic oxidation by phenolases, particularly peroxidase (POD), which subsequently generates free radicals. To test this hypothesis, we manipulated the chemical interactions in foliage of cotton, tomato, and lettuce by application of antioxidants, prooxidants, enriched extracts of phenolases, and/or phenolic substrates. Larvae of Heliothis virescens or Helicoverpa zea that received viral inoculum on treated foliage were less likely to die from viral infection the higher the POD activity of this foliage. Furthermore, the higher the POD activity, the more free radicals were generated in crushed foliage, and the more free radicals generated, the lower the incidence of viral disease. We present a series of reactions hypothesized to lead to inhibition of viral disease by free radicals, the generation of which is mediated, at least in part, by POD. Phenolic redox cycling catalyzed by POD involving clastogenesis (generation of H₂O₂) appeared to be a critical driver of phytochemical reactions leading to free radical generation and inhibition of baculoviral disease in their noctuid hosts. We also report application of an assay for the detection of free radicals by using methemoglobin as a new modification of this method for detecting radicals in plant foliage in the immediate aftermath of an oxidative burst.     

Melatonin and Structurally-Related Compounds Protect Synaptosomal Membranes from Free Radical Damage

Since biological membranes are composed of lipids and proteins we tested the in vitro antioxidant properties of several indoleamines from the tryptophan metabolic pathway in the pineal gland against oxidative damage to lipids and proteins of synaptosomes isolated from the rat brain. Free radicals were generated by incubation with 0.1 mM FeCl₃, and 0.1 mM ascorbic acid. Levels of malondialdehyde (MDA) plus 4-hydroxyalkenal (4-HDA), and carbonyl content in the proteins were measured as indices of oxidative damage to lipids and proteins, respectively. Pinoline was the most powerful antioxidant evaluated, with melatonin, N-acetylserotonin, 5-hydroxytryptophan, 5-methoxytryptamine, 5-methoxytryptophol, and tryptoline also acting as antioxidants.     

离子液体中丙烯腈三元共聚的研究

采用离子液体1-丁基-3-甲基咪唑四氟硼酸盐([BMIM]BF4)为溶剂,进行了丙烯腈(AN)、丙烯酸甲酯(MA)、衣康酸(ITA)的自由基三元共聚反应的研究。讨论了总单体浓度、引发剂含量、聚合时间、MA含量、ITA含量对共聚物相对分子质量和转化率的影响。结果表明:以离子液体[BMIM]BF4为溶剂,AN、MA和ITA可发生三元共聚,聚合物相对分子质量可达10万以上;且MA的含量可以很低直至为0,对聚合物相对分子质量影响不大;以离子液体为溶剂的共聚物的化学结构与以NaSCN水溶液为溶剂的聚合物的结构相似。     

活性自由基聚合法合成偶氮聚合物研究进展

偶氮聚合物具有光致顺反异构和光学各向异性,其在光电信息技术领域具有重要的潜在应用前景.利用活性自由基聚合的方法可以在温和的条件下合成得到特定结构与预定相对分子质量的偶氮聚合物.综述了该技术领域的最新研究进展,并对近年来出现的聚合体系与方法,包括氮氧稳定自由基聚合(NMP)、原子转移自由基聚合(ATRP)、可逆加成一断裂链转移(RAFT)聚合等,作了简要的评述.