丁基罗丹明B-Fe2+-H2O2体系荧光法测定茶叶的抗氧化活性

丁基罗丹明B本身能产生特征荧光,其激发波长和发射波长分别为560 nm和582 nm。在酸性介质中,Fe^2＋-H2O2体系产生的羟自由基可以迅速氧化丁基罗丹明B使其荧光猝灭,而茶叶的水提取物可以部分清除溶液中的羟自由基,从而使其荧光猝灭程度减弱。据此建立了一种测定茶叶抗氧化性的新方法。     

荧光素钠-Mn2+-H2O2体系荧光法测定常见水果的抗氧化活性

荧光素钠本身能产生特征荧光,其激发波长和发射波长分别为491nm和512nm。在碱性介质中,Mn^2 -H2O2体系产生的羟自由基可以迅速氧化荧光素钠使荧光猝灭,而水果提取物可以部分清除溶液中的羟自由基,从而使其荧光猝灭程度减弱。据此建立了一种测定水果抗氧化性的新方法。测试了9种常见水果的抗氧化活性,其中桃、橙子、香瓜、香蕉、西红柿的抗氧化性较强。     

罗丹明B-Feton体系荧光法测定中草药抗氧化活性

酸性介质中,罗丹明B能产生特征荧光,Feton体系产生的羟自由基能迅速氧化罗丹明B使其荧光猝灭,而许多中草药提取物可部分清除溶液中的羟自由基使其荧光猝灭程度降低,据此建立了一种测定中草药抗氧化性的新方法。应用所建立的方法测定了几种常见中草药(黄芩、金莲花、甘草、沙棘)的抗氧化活性。     

罗丹明6G-锰(Ⅱ)-过氧化体系荧光法测定常见油性种子的抗氧化活性

碱性介质中罗丹明6G能产生特征荧光,其最大激发波长和发射波长分别为350 nm和550 nm;Mn2+-H2O2体系在碱性介质中产生的羟自由基可以迅速氧化罗丹明6G使其荧光猝灭,而油性种子的浸提物可以清除羟自由基,从而使溶液的荧光猝灭程度降低,据此建立了测定油性种子抗氧化性的新方法.实验观察到抗氧化剂维生素C和硫脲等在低浓度范围内对羟自由基的清除率与用量呈上升关系,而在大浓度下反而下降.讨论了样品的水、醋酸、乙醇溶剂浸提物对羟自由基的清除效率.用水、醋酸作提取剂,分别测试了7种常见油性种子的抗氧化活性.     

罗丹明6G-锰（Ⅱ）-过氧化氢体系荧光法测定常见油性种子的抗氧化活性

碱性介质中罗丹明6G能产生特征荧光，其最大激发波长和发射波长分别为350nm和550nm；Mn^2 -H2O2体系在碱性介质中产生的羟自由基可以迅速氧化罗丹明6G使其荧光猝灭，而油性种子的浸提物可以清除羟自由基，从而使溶液的荧光猝灭程度降低，据此建立了测定油性种子抗氧化性的新方法。实验观察到：抗氧化剂维生素C和硫脲等在低浓度范围内对羟自由基的清除率与用量呈上升关系，而在大浓度下反而下降。讨论了样品的水、醋酸、乙醇溶剂浸提物对羟自由基的清除效率。用水、醋酸作提取剂，分别测试了7种常见油性种子的抗氧化活性。     

罗丹明6G-Fenton体系荧光法测定中草药抗氧化活性

罗丹明6G本身能产生特征荧光,而Fenton体系产生的羟自由基能迅速氧化罗丹明6G使其荧光猝灭,当加入抗氧化剂时可清除羟自由基,导致体系荧光猝灭程度降低,据此建立了筛选抗氧剂的荧光分析新体系。应用所建立的方法测定了红藤、连翘、山楂、黄柏和玉米须5种常见中草药提取物的抗氧化活性。结果表明,红藤、连翘、山楂、黄柏和玉米须的提取物具有较强的抗氧化活性。     

氧氟沙星-Fenton体系荧光法测定和评价中草药抗氧化活性北大核心CSCD

研究利用荧光法测定和评价中草药抗氧化活性。氧氟沙星(Ofloxacin,OFL)能产生强荧光,在酸性环境中,Fenton反应产生的羟基自由基(·OH)能氧化OFL使其荧光猝灭,加入抗氧化剂或含有抗氧化成分的中草药可清除·OH使与OFL反应的·OH量减少,导致OFL荧光猝灭程度减弱。OFL荧光猝灭程度与加入抗氧化剂量或中草药中抗氧化成分的量呈定量关系,据此建立了一种测定和评价中草药抗氧化活性的新方法。应用该法测定和评价了7种常见中草药抗氧化活性,其中夏枯草、连翘和黄连的抗氧化活性较强。该方法操作简单,体系稳定,可用于中草药抗氧化活性测定和评价。     

罗丹明6G荧光猝灭法测定痕量肝素

在pH 8.0的缓冲体系中,肝素使得罗丹明6G的荧光发生明显猝灭,罗丹明6G的荧光猝灭程度在一定范围内与肝素的浓度成正比,据此建立了荧光猝灭法测定痕量肝素的方法,并对体系的荧光猝灭机理进行了讨论。体系的激发波长为482 nm,发射波长为560 nm,线性范围为0.05~3.0 mg/L,检出限为6.1μg/L。方法已应用于肝素钠注射液中肝素含量的测定。     

罗丹明B显色检测Fenton反应产生的羟自由基

提出Fe2 H2O2 罗丹明B分析新体系并用于羟自由基的检测。方法用Fenton反应产生羟自由基,加入显色剂罗丹明B,羟自由基使罗丹明B的颜色发生变化,通过紫外 可见分光光度计测其ΔA值的变化,可间接测定羟自由基产生的量。通过测定条件的研究,探讨了最佳实验条件。该方法稳定,可作为一种简便的筛选抗氧化剂的方法。     

恒波长同步荧光猝灭法测定饮用水中微量溴酸根

在HCl介质中,Δλ=20nm,溴酸根对罗丹明123的恒波长同步荧光有猝灭作用,且猝灭程度与溴酸根的含量呈线性关系,据此建立了恒波长同步荧光猝灭测定饮用水中的微量测定溴酸根的新方法。该方法的线性范围为0～200μg/L,检出限为3.0ng/mL。该方法可用于化学试剂和各种饮用水中溴酸盐含量的测定。     

Syntheses of 2-hydroperoxy-and 2-hydroxy-2H-imidazoles

Oxidation of fully substituted imidazoles 1 by singlet oxygen gives in good yield fully substituted 2-hydroperoxy-2H-imidazoles 2 . Reduction of 2 by triphenylphosphine leads to 2-hydroxy-2H-irnidazoles 3 . Limitations of the methods are reported.     

Crystal Structures of [Bu2Sn(O2PPh2)2], [Ph2Sn(O2PPh2)2], and [PhClSn(O2PPh2)OMe]2. Raman Spectra of [Ph2Sn(O2PPh2)2] and [PhClSn(O2PPh2)OMe]2

[(n‐Bu)₂Sn(O₂PPh₂)₂] ( 1 ), and [Ph₂Sn(O₂PPh₂)₂] ( 2 ) have been synthesized by the reactions of R₂SnCl₂ (R=n‐Bu, Ph) with HO₂PPh₂ in Methanol. From the reaction of Ph₂SnCl₂ with diphenylphosphinic acid a third product [PhClSn(O₂PPh₂)OMe]₂ ( 3 ) could be isolated. X‐ray diffraction studies show 1 to crystallize in the monoclinic space group P2₁/c with a = 1303.7(1) pm, b = 2286.9(2) pm, c = 1063.1(1) pm, β = 94.383(6)°, and Z = 4. 2 crystallizes triclinic in the space group , the cell parameters being a = 1293.2(2) pm, b = 1478.5(4) pm, c = 1507.2(3) pm, α = 98.86(3)°, β = 109.63(2)°, γ = 114.88(2)°, and Z = 2. Both compounds form arrays of eight‐membered rings (SnOPO)₂ linked at the tin atoms to form chains of infinite length. The dimer 3 consists of a like ring, in which the tin atoms are bridged by methoxo groups. It crystallizes triclinic in space group with a = 946.4(1) pm, b = 963.7(1) pm, c = 1174.2(1) pm, α = 82.495(6)°, β = 66.451(6)°, γ = 74.922(6)°, and Z = 1 for the dimer. The Raman spectra of 2 and 3 are given and discussed.     

Electrochemical study of (NEt4)2Cl2FeS2MoS2 and (NEt4)2Cl2FeS2MoS2FeCl2

Summary The ability of [MoS₄]^2–, anions to be used as ligands for transition metal ions has been widely demonstrated, especially with Fe²⁺. The present study has been restricted to linear complexes such as (NEt₄)₂ [Cl₂FeS₂MoS₂] and (NEt₄)₂[Cl₂FeS₂MoS₂FeCl₂]. Their electrochemical properties are described: upon electrochemical reduction, these compounds yield MoS₂, as a black precipitate, and an iron complex in solution, assumed to be [SFeCl₂]^2–. The electrochemical reduction goes through two electron transfers, coupled with the breakdown of the molecular skeleton: a DISPl and an ECE mechanism. Depending on the solvent, the following equilibrium may be observed: [Cl₄Fe₂MoS₄]^2–[Cl₂FeMoS₄]^2–+FeCl₂. The equilibrium constant, K_D, was evaluated by differential pulse polarography. K_D is tightly related to the donor number of the solvent.     

Photocycloaddition of 2-Cyanocycloalk-2-Enones to 2, 3-Dimethylbut-2-Ene

Irradiation of 5,5-dimethyl-6-oxocyclohex- l-ene- l-carbonitrile ( 1 ) in the presence of 2,3-dimethylbut-2-ene afforded 3,3,4,4,7,7-hexamethyl-3,4,4a,5,6,7-hexahydroindeno[1,7-c,d]-],2-oxazole (3) in nearly quantitative yield. In contrast, 4,4-dimethyl-5-oxo-cyclopent-l-ene-l-carbonitrile ( 2 ) under the same conditions reacted not to a tricyclic isoxazole but to a 2:1 mixture of 3,3,6,6,7,7-hexamethyl-2-oxo-bicyclo[3.2.0]heptane-l-carbonitrile ( 4 ) and trans-3,3-dimethyl-2-oxo-5-(2,3-dimethylbut-3-en-2-yl)cyclopentane-l-carbonitrile ( 5 ), respectively.     

Thermal decomposition of Me3SnO2PCl2, Me2Sn(O2PCl2)2 and Ph3SnO2PCl2

TG and DTA studies on Me₃SnO₂PCl₂, Me₂Sn(O₂PCl₂)₂ and Ph₃SnO₂PCl₂ were carried out under dynamic argon atmosphere. The results show that the decomposition proceeds in different stages leading to the formation of Sn₃(PO₄)₂ as a stable product. This compound was characterized by IR spectroscopy. Decomposition schemes involving reductive elimination reactions were proposed.     

Efficient C2 functionalisation of 2H-2-imidazolines

Alkylation and oxidation of 2H-2-imidazolines, followed by regioselective deprotection, thionation and microwave-assisted Liebeskind-Srogl reaction, efficiently led to 2-aryl-2-imidazolines as new analogues of p53-hdm2 interaction inhibitors (Nutlins).