珠芽蓼黄酮类化合物清除DPPH·的作用

以六盘水市本地野生的珠芽蓼为原料,利用70%乙醇作为提取介质提取黄酮类化合物,并以抗坏血酸(VC)和维生素E(VE)为对照物,采用DPPH法研究珠芽蓼黄酮提取物对二苯代苦味肼基自由基(DPPH.)的清除作用。结果表明:珠芽蓼黄酮对DPPH.有较强的清除作用,在其质量浓度为368.94μg/mL时,其清除效果最好,清除率达88.96%,显著高于相同浓度下的VC和VE的清除率。珠芽蓼黄酮提取物是一种有前途的抗氧化剂。     

七种天然黄酮类化合物对超氧阴离子自由基的清除活性

用单扫描示波极谱法研究了从东紫苏和黑沙蒿中分离出的七种黄酮类化合物对超氧阴离子自由基的清除作用.结果表明:七种黄酮类化合物清除O 2的作用强弱与它们所含酚羟基数目多少有关,羟基数目越多,对O 2清除的效果越好.C2-C3双键对黄酮类化合物清除O 2的活性也有贡献;糖苷因空间位阻效应而导致黄酮类化合物抗氧化能力下降.     

天然黄酮类化合物清除羟基自由基的活性研究

采用分光光度法测定了黑沙蒿中黄酮类化合物清除羟基自由基的能力,以IC50值作为评价指标,初步探讨了黄酮类化合物清除羟基自由基的活性与结构之间的关系,为开发利用黑沙蒿提供了科学依据.     

分光光度法测定二氢黄酮化合物对超氧阴离子自由基的清除作用

采用分光光度法测定了来源于几种药用植物的天然二氢黄酮类化合物清除超氧阴离子自由基(O-2·)的能力,探讨了二氢黄酮类化合物清除O-2·的活性与结构之间的关系,以期为开发利用天然抗氧化剂提供科学依据.     

二苯碳酰二肼分光光度法测定废水的化学需氧量

用二苯碳酰二肼分光光度法测定水样消解反应后剩余的六价铬,通过空白消解溶液中六价铬的质量与样品消解溶液中六价铬的质量之差,可以计算出水样的COD值。本方法操作简单、抗干扰性强,检出限为20 mg/L,适用于COD小于1 000 mg/L的水样测定。     

石墨烯修饰电极对维生素B12的电化学响应及其分析应用

应用石墨烯修饰的玻碳电极结合循环伏安法研究了维生素B12在该电极上的电化学行为;用差示脉冲溶出伏安法考察了石墨烯修饰量、缓冲溶液种类、pH、富集电位及富集时间对响应电流的影响。在最佳实验条件下,响应电流与维生素B12的浓度在1.6×10-7~9.5×10-6mol/L范围内有良好的线性相关,检出限为5.9×10-8mol/L。方法可用于药物和人尿样品中维生素B12的检测。     

4种黄酮小分子对DPPH自由基的清除作用及构效关系研究

通过紫外可见光谱测定了4种黄酮小分子芦丁、牡荆素、山奈素、金丝桃苷对DPPH自由基的清除率、稳定性及半抑制浓度(IC50),并以常用的天然抗氧化剂抗坏血酸作为对照,考察了其抗氧化效果,探讨了黄酮类化合物的抗氧化性与结构的关系。结果表明：不同的抗氧化剂清除DPPH自由基达到平衡的时间不同,芦丁所需时间最长。4种黄酮小分子及抗坏血酸均对DPPH自由基有清除效果,并存在一定的量效关系。对DPPH自由基的清除能力从大到小依次为金丝桃苷、抗坏血酸、芦丁、山奈素、牡荆素。结构分析表明,B环邻二酚羟基是黄酮类化合物抗氧化所必需的基团,其羟甲基化及A环羟基糖苷化不利于黄酮类化合物的抗氧化活性。而C环3-OH的糖苷化对抗氧化活性有利,且单糖苷优于双糖苷。     

酵母菌对 Cr(Ⅵ )的生物吸附作用的二苯卡巴肼光度法研究

对二苯卡巴肼显色－光度法研究了啤酒酵母对Cr(Ⅵ）吸附作用。当pH=2时吸附效果最好,振荡30min吸附基本可平衡。常见离子Na^ 、Ca^2 、Mg^2 、CI^-等吸附影响不大。在一定浓度范围酵母菌对Cr(Ⅵ）吸附符合Freundlich和Langmuir等温吸附模型。随酵母菌和Cr(Ⅵ）接触时间的增加,Cr(Ⅵ）被还原为Cr(Ⅲ）。     

微乳液对铬(Ⅵ)-二苯卡巴肼显色体系的增敏作用

通过正交设计的方法,研究了十二烷基硫酸钠(SDS)-正丁醇-正庚烷-水四组分组成的微乳液对铬(Ⅵ)-二苯卡巴肼(DPC)显色体系的影响,得到最佳增敏条件.结果表明:与水(ε=4.06×10 4L·mol-1·cm-1)及相同含水量的SDS胶束(ε=3.97×10 4L·mol-1·cm-1)相比,SDS微乳液对铬(Ⅵ)-DPC显色体系有较好的增敏作用,表观摩尔吸光率ε=8.07×10 4L·mol-1·cm-1,测定灵敏度显著增加.方法用于面漆中铬(Ⅵ)的测定,测得平均回收率为97.2%.     

“永固紫”染料和四氯苯醌中多氯代二苯并二/呋喃的分析

 采用浓硫酸对5种不同来源的四氯苯醌和“永固紫”染料样品进行溶解分散,用甲苯提取和 多层色谱柱纯化,利用同位素稀释法及高分辨气相色谱/质谱 (HRGC/HRMS)联用技术,测定 了其中的多氯代二苯并二/呋喃(PCDD/F)的质量比。结果表明“永固紫”染料及其原料中P CDD/F的质量比异常高,八氯代二苯并二/呋喃(OCDD/F)已达到μg/g级甚至100 μg/g级,七氯代二苯并二/呋喃(HpCDD/F)和六氯代二苯并二/呋喃(HxCDD/F)质量比也达到 ng/g级。所有样 品的毒性当量浓度(TEQ)均已超过10 pg/g的危险水平,是纺织品中PCDD/F的一类重要污染源 。并进一步探讨了PCDD/F的来源。     

Radical Scavenging Activity of Antioxidants by Cyclic Voltammetry

This work investigates the reactivity of individual antioxidants with the free radicals generated by 2,2′-azobis(isobutironitrile) (AIBN). The consumption of antioxidants was followed by cyclic voltammetry. The fitting of such decay with a kinetic model yielded the rate constant of radical formation and the rate constant of radical inhibition exerted by each antioxidant. The antioxidant efficiency was defined as the ratio between and . The following ranking of antioxidants was obtained: α-tocopherol≫catechin≫retinyl acetate≫hydroxytyrosol≫oleuropein≫caffeic acid. Overall, the approach shows the utility of cyclic voltammetry to investigate the kinetic rates at which antioxidants react with radicals.     

含吗啉基片段的水杨醛席夫碱类化合物的合成及其淬灭1,1-二苯基-2-三硝基苯肼自由基性能

通过3-氟-4-吗啉基苯胺和取代水杨醛缩合反应,合成了14个含吗啉基片段水杨醛席夫碱类化合物(Ⅰa-Ⅰn)。通过核磁共振波谱仪(NMR)、傅里叶变换红外光谱仪(FTIR)、液相色谱-质谱联用仪(LC-MS)和元素分析等技术手段研究了产物的结构和淬灭1,1-二苯基-2-三硝基苯肼(DPPH)自由基的活性。 结果表明,在0.02~0.10 g/L,所有化合物均表现出一定的淬灭DPPH自由基活性。 其中,化合物Ⅰd和Ⅰf表现出较为优异的性能,化合物Ⅰd的活性在30%~55%,化合物Ⅰf的活性则大于50%。 随着化合物Ⅰd、Ⅰh、Ⅰj和Ⅰn质量浓度的增大,其淬灭DPPH自由基的活性均呈现增强趋势。     

高效液相色谱-质谱-二苯基三硝基苯肼在线筛选与鉴别茶叶中抗氧化活性成分

将基于在线高效液相色谱-二苯基三硝基苯肼(HPLC-DPPH)快速筛选自由基清除剂的方法与电喷雾飞行时间质谱(ESI-TOF/MS)结合,建立了茶叶粗提物中抗氧化活性成分在线筛选与鉴别的方法.本方法是在HPLC色谱柱分离后进行分流,一路进入ESI-TOF/MS用于各化合物的快速鉴别,另一路流出液与稳定的自由基DPPH混合,实现在线筛选自由基清除剂的作用.本方法用于茶水中抗氧化成分的快速筛选与鉴别,筛选出11个具有明显DPPH自由基清除作用的化合物,通过ESI-TOF/MS在线分析获得的质谱信息,结合相关文献和数据库,实现了各化合物的快速鉴别.11个化合物分别为茶氨酸、Theogallin、没食子儿茶素、茶碱、色氨酸、表没食子儿茶素、表没食子儿茶素没食子酸酯、表儿茶酚、没食子酸酯、没食子儿茶素没食子酸酯及儿茶素没食子酸酯.本方法效率高、稳定性好,是复杂天然产物中抗氧化剂快速筛选与鉴别的有力工具.     

Fe3O4 Nanorods-RGO-ionic Liquid Nanocomposite Based Electrochemical Sensor for Aflatoxin B1 in Ground Paprika

A novel and sensitive method for the determination of aflatoxin B1 (AFA−B1) in ground paprika using a methyltrioctylammonium chloride ionic liquid (IL), iron oxide nanorods (Fe₃O₄ nanorods) and reduced graphene oxide (RGO) fabricated glassy carbon electrode (GCE) was developed. The synthesized nanoparticles, nanocomposites and modified electrode surfaces were characterized by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), thermogravimetric analysis (TGA/DSC) and x-ray diffraction (XRD) analyses. Moreover, the electrochemical performance of the developed sensor was determined by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The obtained results demonstrate that the sensitivity of AFA−B1 is significantly enhanced on RGO-Fe₃O₄ nanorods-IL-GCE in comparison with bare GCE, RGO-GCE and RGO-Fe₃O₄ nanorods-GCE. The redox peak currents of AFA−B1 exhibited good linear relationship with its concentration in the range from 0.02 to 0.33 ng mL⁻¹ with detection limit of (LOD) 0.03 ng mL⁻¹ and limit of quantification (LOQ) 0.36 ng mL⁻¹ respectively (S/N=3). In addition, the fabricated electrode showed good stability and reproducibility. The proposed technique was effectively applied to identify the AFA−B1 in real ground paprika samples with acceptable results.     

Determination of the Free Radical Scavenging Activity of Lycium Extracts

Lycium species growing in Turkey have not so far been studied sufficiently. For this reason, non-polar and polar extracts obtained from the fruits of Lycium barbarum L. and L. Ruthenicum Murray (Solanaceae) were assessed both in vitro for their potential as free radical scavenger crude extracts and their phenolic composition. Fruits of Lycium species were sequentially extracted with petroleum ether, ethyl acetate, methanol, n-butanol, and water in a Soxhlet extractor. All the extracts were assessed for the scavenging of the nitrogen-centered free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH^.) by in vitro method. Furthermore, the composition of each extract was investigated both in terms of its Folin-Ciocalteau reactive components and its qualitative content. The phenolic compounds within the extracts were determined as benzoic acid and hydroxycinnamic acid derivatives, flavonoids, and anthocyanins according to their retention time and UV spectral data by HPLC-DAD system.     

Spectrophotometric Determination of Some Pharmaceutical Compounds Using 2,2-Diphenyl-1-picrylhydrazyl

Abstract

A spectrophotometric method for the determination of some pharmaceutical amides, hydrazides and thiols is described. The method is based on the reaction of the studied drugs with 2,2-diphenyl-1-picryl hydrazyl (DPPH). The latter is employed to abstract a hydrogen atom from the drugs thereby promoting a process of radical coupling. This results in a reduction of the violet colour of DPPH with the formation of the yellow coloured 2,2-diphenyl-1-picrylhydrazine (DPPH₂). This fading in colour of DPPH reagent depends on the concentration of the drug being determined. Beer's law is obeyed in the ranges of 1–5 μg/ml (for isocarboxazid and gliclazide), 0.25–2.5 μg/ml (for isoniazid), 0.5–5 μg/ml (for iproniazid), 1–7 μg/ml (for tolazamide), 2–15 μg/ml (for captopril) and 1–6 μg/ml (for sulphathiourea). The validity of the method was tested by analysing the studied drugs in pure form as well as in tablets. Results of analyses were compared statistically with the official or reported methods.     

Determination of Antioxidants by DPPH Radical Scavenging Activity and Quantitative Phytochemical Analysis of Ficus religiosa

The use of F. religiosa might be beneficial in inflammatory illnesses and can be used for a variety of health conditions. In this article, we studied the identification of antioxidants using (DPPH) 2,2-Diphenyl-1-picrylhydrazylradical scavenging activity in Ficus religiosa, as F. religiosa is an important herbal plant, and every part of it has various medicinal properties such as antibacterial properties that can be used by the researchers in the development and design of various new drugs. The 2,2-Diphenyl-1-picrylhydrazyl (DPPH) is a popular, quick, easy, and affordable approach for the measurement of antioxidant properties that includes the use of the free radicals used for assessing the potential of substances to serve as hydrogen providers or free-radical scavengers (FRS). The technique of DPPH testing is associated with the elimination of DPPH, which would be a stabilized free radical. The free-radical DPPH interacts with an odd electron to yield a strong absorbance at 517 nm, i.e., a purple hue. An FRS antioxidant, for example, reacts to DPPH to form DPPHH, which has a lower absorbance than DPPH because of the lower amount of hydrogen. It is radical in comparison to the DPPH-H form, because it causes decolorization, or a yellow hue, as the number of electrons absorbed increases. Decolorization affects the lowering capacity significantly. As soon as the DPPH solutions are combined with the hydrogen atom source, the lower state of diphenylpicrylhydrazine is formed, shedding its violet color. To explain the processes behind the DPPH tests, as well as their applicability to Ficus religiosa (F. religiosa) in the manufacture of metal oxide nanoparticles, in particular MgO, and their influence on antioxidants, a specimen from the test was chosen for further study. According to our findings, F. religiosa has antioxidant qualities and may be useful in the treatment of disorders caused by free radicals.     

电化学测定谷胱甘肽方法的研究

采用循环伏安扫描的方法, 促进谷胱甘肽与邻苯醌亲核加成产物在玻碳电极表面的生成和富集. 在此后的差分脉冲分析中, 邻苯醌的还原峰与谷胱甘肽-邻苯醌加合物的还原峰完全分开, 实现了谷胱甘肽的单独测定. 研究了溶液pH值, 邻苯二酚浓度及循环伏安扫描条件对谷胱甘肽测定的影响. 在优化的条件下, 测定谷胱甘肽的检测限为0.05 µmol/L, 线性范围是0.1 µmol/L～1.7 µmol/L, 同时抗坏血酸, 甘氨酸, L-酪氨酸, L-赖氨酸和半胱氨酸对测定没有干扰. 此电化学测定谷胱甘肽方法选择性好、灵敏度高.