电子顺磁共振法(EPR)对银杏叶提取物及其卷烟捕获自由基能力研究（英文）

自由基存在于人体和卷烟烟气中,会引起人体病理反应和氧化损伤,种类和形态多样,如:O_2~(-·),HO~·,R~·,RO~·,ROO~·。电子顺磁共振法(EPR)是检测和定量分析自由基的重要方法之一。银杏叶提取物(EGB)是由黄酮、内酯、原花青素类成分组成的植物药,具有较好清除自由基和抗氧化能力。本文以槲皮素、芦丁、原花青素等化合物为对照,运用EPR法结合自旋捕集技术研究EGB和EGB卷烟对DPPH,HO·,O~(2-·)、烟气气相自由基、烟气粒相自由基的抑制水平。结果表明,EGB能够有效抑制化学/生物系统和卷烟烟气产生的自由基。尽管抑制自由基整体水平比黄酮单体和原花青素弱,但EGB提取方法简单容易得到,可作为天然抗氧化剂和自由基清除剂用于食品和烟草等行业。EPR法灵敏度高,稳定性好,是用于自由基研究的可靠方法。捕集剂DEPMPO捕集O~(2-·)更加高效,PBN捕集烟气气相自由基比DMPO更有优势。该研究讨论了EGB清除自由基的机理,丰富的酚羟基结构是其抗氧化作用的主要原因。     

匀浆提取-气相色谱/质谱联用法测定卷烟主流烟气中的苯并[a]芘

研究了用匀浆提取-气相色谱/质谱联用法测定卷烟主流烟气中苯并[a]芘的方法,卷烟主流烟气样品用剑桥滤片捕集,匀浆法提取滤片上捕集的苯并[a]芘,然后采用气相色谱-质谱联用法进样分析.结果显示该方法检测出的苯并[a]芘含量和国家标准相符合,并具有提取完全、效率高、能耗低的特点.     

甘肃临泽小枣多糖提取及抗氧化性

研究了甘肃临泽小枣的抗氧化活性.采用邻二氮菲-Fe<'2+>-H<,2>O<,2>氧化法、邻苯三酚自氧化法以及卵黄脂蛋白不饱和脂肪酸过氧化体系对小枣多糖抗氧化作用进行了测定.临泽小枣多糖对羟自由基、超氧阴离子自由基均有清除能力,并能抑制卵黄脂蛋白脂质过氧化作用,在相同浓度下,多糖提取液对羟自由基清除能力最强、抑制卵黄脂...     

基于EPR方法的天然产物抗氧化性能研究(英文)

自旋捕捉EPR、用于动物模型的低温EPR以及自旋标记EPR等多种EPR方法已经用于天然产物的抗氧化活性研究中.虽然对于抗氧化剂而言其必备条件之一就是具有体外清除自由基的能力,但是外源性抗氧化剂在生物体内抗氧化剂抗氧化能力评价的方法更有实际意义.通过对超过200种中药和一些传统中药处方的研究,已经建立并详细描述了用于评价天然产物抗氧化能力的EPR筛选方法.通过EPR方法可以获得天然产物在分子水平、细胞水平以及组织水平抗氧化能力的比较全面的评价.     

香蕉皮中总黄酮的体外抗氧化性

以芦丁为对照品,测定了香蕉皮中总黄酮的含量.并采用Fenton反应体系产生羟自由基和邻苯三酚自氧化产生超氧阴离子自由基,研究了香蕉皮总黄酮对两者的清除作用.结果表明,香蕉皮中总黄酮含量为0.946％.香蕉皮黄酮对O2-·和·OH均有较强的清除作用,在一定范围内随着黄酮浓度增大其抗氧化能力也随之增强.     

混酸捕集-原子吸收光谱法测定主流烟气中的铅和镉

研究建立了用盐酸-硝酸混酸捕集主流烟气中铅和镉,并用原子吸收光谱法测定其含量的方法.对主流烟气中铅和镉的捕集条件和捕集液处理条件进行优化,并与常用的剑桥滤片法进行比较,对原子吸收光谱法测定主流烟气中铅和镉含量的回收率、精确度进行了试验,同时选取了5个烤烟型和1个混合型卷烟样品进行检测实验.结果表明:用10％盐酸+5％硝...     

通经草黄酮的体外抗氧化性

探讨通经草黄酮的体外抗氧化活性.采用Fenton反应产生羟基自由基体系、邻苯三酚自氧化体系、过氧化氢的反应体系对蒙药材通经草黄酮的抗氧化活性进行研究.通经草黄酮对羟基自由基、超氧阴离子自由基、过氧化氢具有很强的清除作用,其EC50分别为0.0099、0.0060和0.0190mg/mL,且呈浓度依赖关系.通经草黄酮是一种天然有效的自由基清除剂.     

辛夷再造烟叶对卷烟烟气成分的影响

为研究辛夷再造烟叶对卷烟烟气成分的影响,采用对比分析方法,先用吸烟机捕集卷烟烟气,收集主流烟气的总粒相物,再用超声波萃取方法对收集烟气粒相物的剑桥滤片进行萃取,分析烟气中的常规成分(烟碱、焦油、水分),最后用气相色谱-质谱法(GC-MS)定性、定量分析烟气化学成分.结果表明,与空白样对比,辛夷再造烟叶卷烟对总粒相物、烟碱、焦油量影响不明显;对卷烟致香成分的增加起到有利作用,其中增加的主要致香成分中糠醛在各添加比例中的增加量达到40％左右、柠檬烯在各添加比例中的增加量达到50％左右、丁香酚在4‰辛夷再造烟叶卷烟中的增加量达到66.30％,巨豆三烯酮在2‰辛夷再造烟叶卷烟中的增加量达到93.30％,肉豆蔻酸在4‰辛夷再造烟叶卷烟中的增加量达到186.67％,金合欢醇在4‰辛夷再造烟叶卷烟中的增加量甚至达到241.81％.     

车前草中多酚的抗氧化活性

采用福林-酚法测定车前草60％乙醇提取物和不同极性部位的总多酚含量,应用DPPH法、ABTS法和邻苯三酚法,研究上述提取物对自由基的清除能力.车前草正丁醇相的总多酚的含量最高,正丁醇相对DPPH自由基和ABTS自由基显示了较强的清除能力,其各相的抗氧化活性大小与总多酚的含量高低顺序一致;而乙酸乙酯相对O2-·的清除能力最强.实验结果表明,车前草60％乙醇提取物及其不同极性部位都具有抗氧化作用,其活性部位为正丁醇相和乙酸乙酯相.     

新疆一枝蒿黄酮提取物抗氧化活性分析

采用超声波辅助提取法提取了一枝蒿中黄酮类化合物,采用邻二氮菲-Fe²⁺氧化法、DPPH·法和普鲁士蓝法3种常用的体外抗氧化活性评价方法,对一枝蒿黄酮提取物的抗氧化能力进行全面的比较分析。结果表明,一枝蒿黄酮提取物的羟基自由基的清除率高达73.47%;DPPH·自由基的清除率比羟基自由基高16.93%,普鲁士蓝法测定总抗氧化结果为0.125。     

ESR study on scavenging effect of nicotine on free radicals

Smokers have less risk to catch degenerative diseases such as Alzheimer’s disease and Parkinson’s disease that are both correlated with enhanced oxidative stress. The scavenging effect of nicotine on free radicals was investigated by electron spin resonance techniques. It was found that the scavenging effect of nicotine on hydroxyl radicals and superoxide free radicals was higher than that of vitamin C. It was also found that nicotine could scavenge free radicals in gas-phase cigarette smoke. The data indicate that nicotine may be a potential antioxidant.     

EPR study of the toxicological effects of gas-phase cigarette smoke and the protective effects of grape seed extract on the mitochondrial membrane

Electron paramagnetic resonance spin trapping and spin labeling techniques were used to study the effects of grape seed extract on the biophysical propertiers of the mitochondrial membrane exposed to gas-phase cigarette smoke. The spin trapping results indicated that grape seed extract can effectively scavenge free radicals in cigarette smoke and the lipid free radicals generated from the lipid peroxidation of mitochondrial membrane caused by gas-phase cigarette smoke. The spin labeling results showed that grape seed extract can protect the mitochondrial membrane from the toxicological damage caused by gas-phase cigarette smoke.     

Effects of resveratrol and its analogs on scavenging hydroxyl radicals: Evaluation by EPR spin trapping method

Resveratrol (3,4′,5-trihydroxy-trans-stilbene) and six analogs, polyhydroxystilbenes, were synthesized. Their effects on scavenging hydroxyl radicals were studied by electron paramagnetic resonance (EPR) spin trapping method. The EPR signal intensity of the spin adduct of hydroxyl radical to 5,5-dimethyl-1-pyrroline N-oxide was detected and used as a standard for the evaluation of the effect of the seven compounds on scavenging hydroxyl radicals. While all seven compounds exhibited hydroxyl radical-scavenging activity, some of them proved to be more effective than resveratrol in this model. Another stable but low-intensity spin adduct was also observed by EPR. A possible assignment is proposed.     

ESR Study on Scavenging Effect of Squalene on Free Radicals in Mainstream Cigarette Smoke

Radicals in mainstream cigarette smoke (MCS) have been proposed to contribute to the harm caused by cigarette smoking. In the present study, we used natural antioxidant, squalene, to treat cigarette filters and tobacco for scavenging gas- and particulate-phase free radicals in MCS. The scavenging activities of cigarette filter and tobacco containing squalene against gas and particulate-phase free radicals were detected and quantified using spin-trapping or directly electron spin resonance spectroscopy method. The results revealed that squalene could significantly scavenge gas- and particulate-phase free radicals in MCS in a dose-dependent manner. The radical-scavenging activity of cigarette filter treatment was higher than that of tobacco treatment, irrespective of either gas-phase free radicals, or particulate-phase free radicals in MCS. Among them, 3 mg squalene/filter treatment showed that the highest scavenging effects against gas- and particulate-phase free radicals were 35.9 and 35.4%, respectively. The use of squalene as potential scavenger for reducing free radicals in cigarette smoke is discussed.     

卷烟烟气中活性自由基的自旋捕获ESR研究

卷烟烟气中的瞬态自由基对人体健康是相当有害的，而检测活性自由基最常用的方法是自旋捕获方法. 本研究中使用高效新型捕捉剂DEPMPO能够直接在水相中捕捉到烷基自由基与羟基自由基，并未发现烷氧自由基加合物. 考虑到DEPMPO对活性自由基的捕捉能力和加合物ESR谱图解析特征性都优于PBN与DMPO，且在有机溶剂中溶解较多的氧分子. 因此认为以往文献中所捕获的烷氧自由基来源于烷基自由基氧化后的次级自由基产物.     

Antioxidant Activities of Some New Chromonyl-2,4-Thiazolidinediones and Chromonyl-2,4-Imidazolidinediones Having Chromone Cores

The antioxidant properties of 11 new synthesized chromonyl-2,4-thiazolidinediones and chromonyl-2,4-imidazolidinediones (CBs) were investigated. The antioxidant activities and mechanisms of the CBs interaction with reactive oxygen species (ROS) were clarified using various in vitro antioxidant assay methods including superoxide anion radical ( $ \mathrm{O}\overline{{}_2^{\bullet }} $ ), hydroxyl radical (HO^?), 1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH^?) scavenging activity and the iron (II)-ferrozine complex formation. The potassium superoxide/18-crown-6 ether dissolved in dimethylsulfoxide (DMSO) was applied as a source of superoxide anion radical. Hydroxyl radicals were produced in the Fenton-like reaction Fe(II)+H₂O₂. Chemiluminescence, spectrophotometry, and electron paramagnetic resonance (EPR) spectroscopy using 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) as spin trap were applied as the measurement techniques. The CBs examined that exhibited good free radical scavenging activity also showed strong total antioxidant power capacity. Possible mechanisms of antioxidation are proposed to explain the differences in the experimental results between the chromone derivatives with imidazolidine-2,4-dione ring and those with thiazolidine-2,4-dione ring. In conclusion, some of the new CBs are promising to be applied as inhibitors of free radicals.     

Free-radical scavenging and mechanism study of flavonoids extracted from the radix ofScutellaria baicalensis Georgi

Free-radical scavenging activities of baicalein, baicalin, wogonin and wogonoside, the four major flavonoids in a traditional Chinese herb medicine, the radix ofScutellaria baicalensis Georgi, were examined by electron paramagnetic resonance (EPR). The results showed that baicalein and baicalin scavenged hydroxyl radical, superoxide anion, 2,2-diphenyl-1-picrylhydrazyl radical and alkyl radical in a dose-dependent manner, while wogonin and wogonoside showed subtle or no effect on these radicals. Baicalein was the most effective free-radical scavenger among the four tested compounds. When 10 mmol/l tested flavonoids dissolved in alkaline solution, only baicalein and baicalin form stable free radicals which can be detected by EPR technique, it was found that the signal came from theiro-di-hydroxyl structure in ring A. To our knowledge, it was the first time demonstrated that flavonoids witho-di-hydroxyl structure in ring A could also form stable semiquinone free radicals. These results demonstrated that flavonoids in radix ofScutellaria baicalensis witho-di-hydroxyl group in ring A such as baicalein and baicalin are good free-radical scavengers and might contribute to some of their pharmaceutical effects.     

葡萄籽中多酚类物质对氧自由基清除作用的ESR研究

用ESR自旋捕集技术研究了从葡萄籽分离的单体、二聚体和三聚体等多酚类物质对羟基自由基和超氧阴离子的精除作用,并与化学发光法的测定结果进行了比较,得到了较一致的结果,证明葡萄籽中多酚类物质对氧自由基的确有较好的清除作用,这很可能是喝少量葡萄酒有利于身体健康的原因.     

香菇中总黄酮含量的测定及抗氧化活性研究

采用浓度为70%的乙醇提取香菇中的总黄酮物质,分光光度法测定香菇中的总黄酮含量,研究了香菇中黄酮类化合物对超氧自由基、羟基自由基的清除作用,结果表明：香菇中总黄酮提取率为0.738%,香菇中黄酮类化合物对清除自由基有一定的作用,且黄酮类化合物的添加量在试验范围内与其抗氧化性呈正相关。     

蒙药材冷蒿中黄酮类化合物的测定及体外抗氧化性研究

采用分光光度法测定了冷蒿中黄酮类化合物的含量,通过Fenton反应测定了冷蒿黄酮类化合物提取液清除羟基自由基的能力。结果表明,冷蒿中黄酮类化合物含量为42.3mg/g,样品回收率为92.0%—99.6%。黄酮类化合物提取液对羟基自由基清除作用随黄酮类化合物含量的增高而增加。