化学发光法比较5种抗氧化剂的活性

抗氧化剂是一种重要的食品添加剂,实验发现抗氧化剂对K3Fe(CN)6-鲁米诺化学发光体系产生的化学发光具有强烈的抑制作用,并且抗氧化剂对化学发光强度的抑制程度与其抗氧化活性在一定范围成线性关系.据此,结合流动注射技术建立快速测定抗氧化剂抗氧化活性的新方法。分析对比了维生素C,二丁基羟基甲苯,特丁基对苯二酚,维生素E,柠檬酸等5种抗氧化剂的抗氧化活性。其结果是:抗氧化活性由强到弱的顺序是:特丁基对苯二酚>二丁基羟基甲苯>维生素C>维生素E>柠檬酸。本文还对发光体系受到抑制作用可能的机理进行了探讨。     

羟自由基对支撑磷脂双层膜的破坏及水溶性抗氧化剂保护作用的电化学研究

以支撑磷脂双层膜(supported bilayer lipid membrane, s-BLM)作为生物膜模型, 利用Fenton体系产生羟自由基(hydroxyl free radical, •OH), 采用循环伏安法研究了s-BLM与•OH之间的相互作用. 结果表明: •OH通过与磷脂发生化学反应, 诱发s-BLM上形成孔洞或缺陷, 这种作用对时间、FeSO₄和H₂O₂的浓度具有依赖性, 且不可恢复. 具有还原性基团的抗氧化剂维生素C, 还原型谷胱甘肽和L-半胱氨酸, 通过与•OH发生氧化还原反应, 可抑制•OH与s-BLM的相互作用, 降低•OH对s-BLM结构的破坏程度.     

黄酮类抗氧化剂结构-活性关系的理论解释

用AM 1方法对若干黄酮类抗氧化剂做了计算 .发现 :( 1 )黄酮化合物邻二酚羟基清除自由基的活性强于间二酚羟基 .原因一是前者半醌式自由基与邻位酚羟基形成分子内氢键 ,从而更稳定 ;二是前者半醌式自由基通过共振形成邻苯醌 ,这使其未成对电子密度在邻位氧上有较多分布 ,内能更低 .( 2 )色原酮类黄酮化合物C环的吸电子性质使它对A环酚羟基有钝化作用 ,使其更不活泼 .由于B环受C环影响较小 ,而且大多数黄酮类抗氧化剂B环为邻二酚羟基取代 ,因此实验总结出的B环酚羟基活性高的规律得以解释 .     

钌（Ⅱ）—邻菲咯啉偶合化学发光法测定Fenton反应产生的羟自由基

提出了一种测定Ｆｅｎｔｏｎ反应产生羟自由基的偶合化学发光分析法。羟自由基与苯甲酸发生烃化反应后生成的羟基苯甲酸能增大钌（Ⅱ）邻菲咯啉－Ｃｅ（Ⅳ）化学发光反应的发光强度。用化学发光法测定羟基苯甲酸的含量可间接测定自由基的生成量。拟定的方法,简单,灵敏度高,可用于筛选羟自由基消除剂。     

肉桂中醛、酸类化合物结构与抗菌活性的关系

本文对肉桂醛、酸及其衍生物的抑菌效果进行了测定，对其量子化学参数进行了计算，并对这类化合物抗菌活性和分子化学结构之间的关系进行了相关分析。结果表明，该类化合物抑菌率EFPO、ELUMO和EHOMO的相关系数分别为一0．7814（p＜0．05）、－0．7328（0．05＜ρ＜0．1）和0．6318（ρ＞0．1）。该类化合物的抗菌活性中心原子可能是羰基氧、α-碳、β-碳，由这些原子组成的不饱和羰基共轭体系可能是抗菌剂的活性功能域．     

本征值方法在抗氧化剂定量构效关系研究中的应用

Antioxidants are of great interest because of their involvement in many important biological and industrial processes. It is meaningful to study their structure-antioxidant activity relationship (SAAR) and design novel, efficient and low-toxicity antioxidant. In this paper, Eigen Value Analysis (EVA), a 3-dimensional quantitative structure activity relationship (3-D QSAR) method, was employed to study antioxidant SAAR. Significant relational models were obtained with all the PLS cross-validate qcv^2 values being larger than 0.5, meaning that the models have sound predictive power. Compared with other QSAR methods, EVA possesses several advantages, especially that it does not need alignment. It should be believed that EVA will be an efficient approach to SAAR.     

竹叶提取物的抗氧化活性研究

一般认为黄酮是竹叶提取物中抗氧化作用的有效成分,黄酮含量越高,抗氧化能力越强[1-3]。本实验对不同溶媒竹叶提取物的抗氧化能力做了比较研究,发现抗氧化作用与黄酮含量并不完全成正比关系;并通过进一步的定性实验,证明黄酮并不是竹叶提取物中的唯一的抗氧化有效成分,还有其它     

Cy5-Fe2+-H2O2光度法测定天然抗氧化剂的抗氧化活性

在缓冲溶液中,Fenton体系产生的羟基自由基能迅速与五甲川菁染料(Cy5)作用使其褪色,在647 nm处测定体系吸光度的变化,可间接测定羟基自由基的生成量。抗氧化剂的加入可部分消除溶液中的羟基自由基,从而使溶液的吸光度下降程度减弱。据此建立了一种测定抗氧化剂对羟基自由基清除率的新方法。利用所建立的方法测试了抗氧化剂2,6-二叔丁基对甲基苯酚以及几种天然抗氧化剂的抗氧化活性,得到了满意的结果。该方法操作简便、稳定性好,可以作为一种简便的筛选抗氧化剂的方法。     

抗氧化剂的毛细管电泳-间接化学发光联用在线评价方法研究

根据碱性条件下羟自由基与luminol反应会产生化学发光而抗氧化剂能够清除羟自由基从而抑制发光的原理, 结合毛细管电泳技术, 建立了一种针对多组分共存体系中抗氧化组分的在线评价的新方法. 对这种毛细管电泳-间接化学发光检测技术, 优化化学发光的各种条件, 考察了抗氧化剂硫脲和麻黄碱的抗氧化活性, 采用曲线拟合求出它们对羟自由基的半数清除浓度(IC₅₀), 得出抗氧化活性大小为麻黄碱＞硫脲, 这与荧光分光光度法的结果一致. 该方法初步应用于评价中药槐米提取物化学组分的抗氧化活性.     

两种槲皮素-Zn配合物的抗氧化活性及其结构的量子化学研究

按照不同比例合成了两种槲皮素-Zn配合物, 采用邻苯三酚自氧化法测定了其抗氧化活性, 然后对其结构在HF/LanL2DZ基组水平上进行了量子化学计算, 讨论了它们的几何构型、电荷分布、原子轨道对前沿分子轨道贡献、分子轨道能量及振动频率. 实验和理论分析都表明, 两种槲皮素-Zn配合物都具有较高的结构稳定性和不同程度的催化超氧阴离子的抗氧化活性.     

Quantum Chemical Study on Reaction of Acetaldehyde with Hydroxyl Radical

The reaction of acetaldehyde with hydroxyl radical was studied by means of quantum chemical methods. The geometries for all the stationary points on the potential energy surfaces were optimized fully, respectively, at the G3MP2, G3, and MP2/6-311 G(d,p) levels. Single-point energies of all the species were calculated at the QCISD/6-311 G(d,p) level. The mechanism of the reaction studied was confirmed. The predicted product is acetyl radical that is in agreement with the experiment.     

7313、7321系列农药的构效关系研究

对7313、7321系列农药利用MOPAC程序包PM3方法进行量子化学计算,讨论了它们的活性部位及构效关系,发现形成6员稠合环结构有利于分子产生药效,N(7)、S(9)、N(11)、C(12)等原子分别与受体的自由基相作用,是该类农药产生共同生物活性的化学基础。     

肉桂酸及其衍生物对活性氧H2O2清除作用

活性氧分子在生物内所引起的脂质过氧化可造成组织和细胞的损伤。因此,从天然产物中寻找抗活性氧的物质已引起国内外广泛重视。本文采用化学发光分析法,利用H2O2-CTMAB-鲁米诺发光体系,研究了中草药有效成分咖啡酸、氯原酸、连翘酯甙、阿魏酸、对．羟基香豆酸、间-羟基香豆酸、肉桂酸抗活性氧H2O2的作用。并与公认的抗活性氧物质抗坏血酸(Vc)进行了比较。     

The Influence of some Chain-Breaking Antioxidants on Thermal-Oxidative Decomposition of Linolenic Acid

Thermoxidation of linolenic acid inhibited by addition of 2,6-di-t-butyl-4-methylphenol and 2,4,6-trimethylphenol at various concentrations was investigated. The measurements were carried out under non-isothermal conditions in an atmosphere of oxygen. DSC curves permitted the determination of onset point and maximum points of the peaks. The influence of inhibitor concentration on temperature of the start of oxidation was noticed. However, no significant changes in temperatures of the maximum heat flow was observed. Measurements and calculations described in this report prove that the assessment of the antioxidant activity of chain-breaking inhibitors can be performed only from the onset temperatures. Calculations of the activation energy of inhibited linolenic acid thermoxidation were performed in order to elucidate the antioxidant activity of the phenolic compounds. This revised version was published online in August 2006 with corrections to the Cover Date.     

DFT Study on the Antioxidant Activity of a Modeled p-Terphenyl Derivative

Relationships between the structure characteristics of natural p-terphenyl com- pounds isolated from three edible mushrooms (Thelephora ganbajun, Thelephora aeronautical, and Boletopsis grisea) indigenous to China and their mechanism of antioxidant activity were studied. Geometry structures of terphenyl molecule and four corresponding radicals, bond dissociation energy (BDE), frontier orbitals (HOMO and LUMO) and single electron density were calculated using DFT methods (B3LYP/6-311G**). The computational results which are consistent with the experimental data well show that terphenyl molecule scavenges DPPH radical by hydrogen abstract mechanism and the high antioxidant activity depends on the substitution position of hydroxyls. Two active 7-, 8-hydroxyls facilitate the hydrogen abstraction due to the intramolecular hydrogen bond and the resonance effect makes 4-hydroxyl radical more stable.     

Interaction of phenolic antioxidants and hydroxyl radicals

Based on pulse radiolysis of aqueous solutions of four phenolic antioxidants including green tea polyphenols, quercetin, caffeic acid and sinapic acid the rate constants for reactions of OH and the antioxidants were determined. And green tea polyphenols and quercetin are the strongest antioxidants.     

N-亚硝基化合物结构-致癌活性的相关性研究

Ｎ－亚硝基化合物结构－致癌活性的相关性研究许禄,姚瑜元（中国科学院长春应用化学研究所应用谱学开放实验室,长春,１３００２２）关键词Ｎ－亚硝基化合物,半经验量化方法,构效关系目前已发现的Ｎ－亚硝基化合物约３００种中多数具有致癌活性。化学家和生物学家对该...     

Theoretical study of mechanism and kinetics for the addition of hydroxyl radical to phenol

The reaction mechanism and kinetics for the addition of hydroxyl radical(OH) to phenol have been investigated using the hybrid density functional(B3LYP) method with the 6-311++G(2dp,2df) basis set and the complete basis set(CBS) method using APNO basis sets,respectively.The equilibrium geometries,energies,and thermodynamics properties of all the stationary points along the addition reaction pathway are calculated.The rate constants and the branching ratios of each channel are evaluated using classical transition state theory(TST) in the temperature range of 210 to 360 K,to simulate temperatures in all parts of the troposphere.The ortho addition pathway is dominant and accounts for 99.8% 96.7% of the overall adduct products from 210 to 360 K.The calculated rate constants are in good agreement with existing experimental values.The addition reaction is irreversible.