铜(Ⅱ)、钴(Ⅱ)Schiff碱配合物的光热性质及其对超氧离子的催化歧化作用

用5-硝基水杨醛与乙二胺缩合,制备了Schiff碱配体.将其与过渡金属Cu(Ⅱ)和Co(Ⅱ)在80℃水浴中搅拌回流1 h,分别形成草绿色和朱红色沉淀,合成出了2种新型的Schiff碱配合物.采用元素分析、红外光谱、紫外光谱、差热热重、荧光光谱、摩尔电导率等分析手段,对配合物进行了表征测试.结果表明,该配合物组成、结构确定,热稳定性强,荧光光谱数据证明配体和配合物都具有荧光性质.用蛋氨酸光照法测定了配体和配合物的生物活性,配体生物活性较低,但形成配合物后活性大增,说明配合物对超氧离子自由基有很强的抑制作用.     

不对称姜黄素类似物的合成及其清除自由基的研究

姜黄素类化合物中,非对称结构的单去甲氧基姜黄素具有一些特殊的生物活性.通过碱法合成2-单取代苯亚甲基环戊酮中间体,再用酸催化合成了10不对称的单羰基姜黄素类似物,多酚羟基的类似物可以不通过羟基保护直接合成,其中,除A1外其它9个为新化合物,并测试了所合成类似物对DPPH自由基的清除能力.结果表明类似物的酚羟基对自由基清...     

含羟基取代基的Schiff碱捕获自由基性能

研究了8个含羟基取代基的Schiff碱捕获自由基——ABTS .和DPPH——的性能。结果发现,Schiff碱捕获自由基的性能首先与分子中所含有的羟基的个数有关,随着羟基数目的增多,Schiff碱捕获自由基的能力增强。大的共轭体系以及羟基处于N原子邻位可增强该Schiff碱捕获ABTS .的性能;但对于捕获DPPH来说,只有同时将大的共轭体系与处于N原子邻位的羟基结合在同一分子中,才能表现出较强的捕获DPPH的性能。由此可见,DPPH对于检测Schiff碱中羟基捕获自由基的性能是一种更为专一的试剂。     

壳聚糖固定化亚铁Schiff碱配合物的研究

利用具有多种生物医用活性的高分子壳聚糖的轴向配位作用合成了壳聚糖-N-亚水杨基氨基酸Schiff碱亚铁配合物,采用IR光谱、元素分析、荧光光谱、紫外-可见吸收光谱和热分析等分析手段对配体及高分子配合物进行了表征,推测了其结构.以核黄素光化学氧化-羟胺-偶氮比色法研究了该化合物对超氧离子自由基的清除能力.结果表明,壳聚糖固定化的N-亚水杨基氨基酸Schiff碱亚铁配合物对超氧离子自由基的清除能力有所降低,但仍具有较强的抑制作用.     

槲皮万寿菊素金属配合物的合成、抗氧化活性及与DNA结合的研究

合成了槲皮万寿菊素铜(Ⅱ)、锌(Ⅱ)铁(Ⅲ)三种配合物,采用红外、紫外光谱及元素分析等方法分析了其配位情况,研究了配合物清除DPPH自由基、超氧阴离子自由基和羟基自由基的活性,并运用紫外光谱滴定实验,研究了配体及配合物与ct-DNA的相互作用.结果表明,配合物较配体具有更强的清除DPPH自由基、超氧阴离子自由基和羟基自...     

抗癌药物的电化学研究Ⅰ.一种Fe(Ⅲ)Schiff碱配合物的基本电化学性质及其与DNA的相互作用

研究了一种自合成的Schiff碱配合物的电化学行为及其与氧和DNA的相互作用.发现此种Schiff碱配合物能与氧发生相互作用而具有吸氧功能,并对氧的电还原有催化作用,同时还发现dsDNA能与此种Schiff碱配合物发生较强的相互作用,特别是Fe(Ⅱ)Schiff碱配合物更易与dsDNA结合.     

基于邻香草醛缩2-氨基-4-硝基苯酚的Schiff碱有机锡配合物的合成、晶体结构及生物活性

邻香草醛缩2-氨基4-硝基苯酚(H₂L)分别与二丁基氧化锡、二苄基二氯化锡反应, 合成了二丁基锡Schiff碱配合物(1)和单苄基Schiff碱配合物(2)。配合物经元素分析、¹H NMR、¹³C NMR、IR、UV-Vis表征, 并用X-射线单晶衍射测定了分子结构。研究了配体H₂L及配合物1、2对癌细胞Hela、MCF7、HepG2、Colo205、NCI-H460的抑制活性, 结果表明配合物1对这5种癌细胞的抑制效果优于现有抗癌药物卡铂, 可作为抗癌药物的候选化合物。在Tris缓冲溶液中, 以EB做为荧光探针, 用荧光光谱法研究了配体H₂L及配合物2与鲱鱼精DNA的相互作用, 结果表明配合物与DNA作用主要是由于Schiff碱配体协同效应所致。     

基于邻香草醛缩2-氨基-4-硝基苯酚的Schiff碱有机锡配合物的合成、晶体结构及生物活性

邻香草醛缩2-氨基4-硝基苯酚(H₂L)分别与二丁基氧化锡、二苄基二氯化锡反应, 合成了二丁基锡Schiff碱配合物(1)和单苄基Schiff碱配合物(2)。配合物经元素分析、¹H NMR、¹³C NMR、IR、UV-Vis表征, 并用X-射线单晶衍射测定了分子结构。研究了配体H₂L及配合物1、2对癌细胞Hela、MCF7、HepG2、Colo205、NCI-H460的抑制活性, 结果表明配合物1对这5种癌细胞的抑制效果优于现有抗癌药物卡铂, 可作为抗癌药物的候选化合物。在Tris缓冲溶液中, 以EB做为荧光探针, 用荧光光谱法研究了配体H₂L及配合物2与鲱鱼精DNA的相互作用, 结果表明配合物与DNA作用主要是由于Schiff碱配体协同效应所致。     

Scchiff碱N-氧化吡啶-2-甲醛缩氨基脲及其铜配合物的合成、晶体结构及谱学性质的研究

合成了Schiff碱N-氧化吡啶-2-甲醛缩氨基脲(PNOS)及其配合物[Cu(PNOS)(NO3)2],并用单晶X射线衍射法测定了配体和配合物结构.PNOS晶体中通过传统氢键形成双层二维网状结构,再由非传统氢键自组装成三维网状结构.配合物[Cu(PNOS)(NO3)2]中的铜为六配位,畸变八面体结构,Schiff碱(PNOS)通过N-氧化吡啶N-O的O原子,亚胺基C=N的N原子,及羰基C=O的O原子与铜配位;一个硝基以单齿配体形式与铜配位,另一个则以双齿配体形式配位.配合物分子通过经典氢键相互作用,形成单层二维网状结构,再通过非经典氢键作用,自组装成双层二维网状结构.     

新癌药物的电化学研究1: 一种Fe(III) Schiff碱配合物的基本电化学性质及其与DNA的相互作用

研究了一种自合成的Schiff碱配合物的电化学行为及其与氧和DNA的相互作用。发现此种Schiff碱配合物能与氧发生相互作用而具有吸氧功能, 并对氧的电还原有催化作用, 同时还发现dsDNA能与此种Schiff碱配合物发生较强的相互作用, 特别是Fe(II)Schiff碱配合物更易与dsDNA结合。     

Study binding of Al-curcumin complex to ds-DNA, monitoring by multispectroscopic and voltammetric techniques

In this work a complex of Al3+ with curcumin ([Al(curcumin) (EtOH)2](NO3)2) was synthesized and characterized by UV-vis, FT-IR, elemental analysis and spectrophotometric titration techniques. The mole ratio plot revealed a 1:1 complex between Al3+ and curcumin in solution. For binding studies of this complex to calf thymus-DNA various methods such as: UV-vis, fluorescence, circular dichroism (CD), FT-IR spectroscopy and cyclic voltammetry were used. The intrinsic binding constant of ACC with DNA at 25°C was calculated by UV-vis and cyclic voltammetry as 2.1×10(4) and 2.6×10(4), respectively. The thermodynamic studies showed that the reaction is enthalpy and entropy favored. The CD results showed that only the Δ-ACC interacts with DNA and the Δ-ACC form has not any tendency to interact with DNA, also the pure curcumin has not any stereoselective interaction with CT-DNA. Fluorimetric studies showed that fluorescence enhancement was initiated by a static process in the ground state. The cyclic voltammetry showed that ACC interact with DNA with a binding site size of 2. From the FT-IR we concluded that the Δ-ACC interacts with DNA via partial electrostatic and minor groove binding. In comparison with previous works it was concluded that curcumin significantly reduced the affinity of Al3+ to the DNA.     

Photophysical studies on binding of curcumin to bovine serum albumins

The excited-state photophysical properties of curcumin in the presence of bovine serum albumin (BSA) have been studied. The absorption and fluorescence changes in curcumin on binding to BSA have been followed at varying concentrations of either curcumin or BSA to determine the binding constant, which has been found to be approximately 10(4) to 10(5) M(-1). Stopped-flow kinetics studies suggested at least two distinct kinetic steps for the binding of curcumin to BSA. The photophysical properties of the singlet-excited state of the curcumin-BSA complex have also been studied. Whereas the absorption spectrum of curcumin is redshifted, the fluorescence spectrum of curcumin was blueshifted in the presence of BSA. The fluorescence quantum yield of curcumin on complexing with BSA was approximately 0.05. Steady-state fluorescence anisotropy studies showed a significant increase in the anisotropy value of 0.37 in BSA-bound curcumin. The fluorescence decay of the curcumin-BSA complex followed a biexponential decay with fluorescence lifetimes of 413 ps (33%) and 120 ps (67%). On the basis of these complementary results, it has been concluded that curcumin shows very high binding to BSA, probably at the hydrophobic cavities inside the protein.     

Circular dichroism spectroscopic studies reveal pH dependent binding of curcumin in the minor groove of natural and synthetic nucleic acids

For the first time, an interaction between the non-toxic, cancer chemopreventive agent curcumin and both natural and synthetic DNA duplexes has been demonstrated by using circular dichroism (CD) and absorption spectroscopy techniques. Upon addition of curcumin to calf thymus DNA, poly(dG-dC).poly(dG-dC) and poly(dA-dT).poly(dA-dT) solutions, an intense positive induced CD band centered around 460-470 nm was observed depending on the actual pH and Na+ ion concentration of the medium; no CD signal was obtained, however, with single stranded poly(dC). Interaction of curcumin with calf thymus DNA was observed already at pH 6.5 in contrast with poly(dG-dC).poly(dG-dC) which induces no extrinsic Cotton effect above a pH value of 5. The protonated, Hoogsteen base-paired structure of poly(dG-dC).poly(dG-dC) is necessary for curcumin binding while the alternating AT-rich polymer formed complexes with curcumin only at certain Na+ concentrations. Evaluation of the spectral data and molecular modeling calculations suggested that curcumin, this dietary polyphenolic compound binds in the minor groove of the double helix. The mechanism of the induced CD activity, the effects of the pH and Na+ ions on the ligand binding and conformation of the double helix are discussed in detail. As well as being an essentially new phenolic minor groove binder agent curcumin is also a promising molecular probe to study biologically important, pH and cation induced conformational polymorphisms of nucleic acids.     

姜黄素与DNA相互作用的电化学性质

采用循环伏安法和差示脉冲伏安法,研究了姜黄素在DNA修饰玻碳电极上与DNA的相互作用.结果表明,姜黄素与DNA之间发生嵌插作用,形成了两种化合物DNA-2curcumin和DNA-curcumin,两者的表观结合常数分别为2.34×10^5L/mol和1.48 L/mol.     

Adsorptive transfer voltammetry applied to the study of chromium-induced DNA damage in the presence of curcumin

The interaction between double-stranded (ds) calf-thymus DNA and chromium in the presence of curcumin (CC) was studied by differential pulse adsorptive transfer voltammetry using carbon paste electrode (CPE). Curcumin–Cr complex generated changes in calf thymus DNA. The mechanism for DNA cleavage by curcumin–Cr complex appears to involve both the hydroxyl radical as well as singlet oxygen. The characteristic peak of dsDNA, due to the oxidation of guanine residues, drastically decreased. The increased DNA damage by curcumin–Cr complex was observed in the presence of various concentrations of chromium(VI).     

Fluorometric sensing of DNA using curcumin encapsulated in nanoparticle-assembled microcapsules prepared from poly(diallylammonium chloride-co-sulfur dioxide)

We report on the synthesis of microcapsules (MCs) containing self-assembled nanoparticles formed from poly[diallylammonium chloride-co-(sulfur dioxide)] in the presence of citrate and silica sol nanoparticles. The MCs are spherical, and SEM and optical microscopy reveal them to have micrometer size. The fluorescent probe curcumin was encapsulated in the MCs and found to be located in the shell. The fluorescence of curcumin in the MCs is altered depending on their microenvironment. Effects of pH and ammonia on the fluorescence of curcumin in the MCs also were studied. The brightness of the probe in the MCs increases on addition of DNA. The effect was used to determine DNA from fish sperm by fluorometry. The association constant (K) is 4?000 mL.g^?1, and the number of binding sites is ~1.0.

吐温表面活性剂囊泡对姜黄素的包载作用

本文研究了烷基链不饱和度对吐温表面活性剂囊泡包载姜黄素的影响。相比吐温-80囊泡,吐温-60囊泡的包载使姜黄素表现出更大的紫外吸收和荧光发射强度、缔合常数和DPPH自由基清除能力。核磁共振氢谱结果表明姜黄素缔合于吐温-60囊泡双分子层中的亲水头基附近,而且姜黄素的酚羟基与吐温-60的酯基产生氢键作用。在吐温-80囊泡中,双键会使吐温-80烷基链产生弯曲或折叠,导致双分子层排列更加松散、极性更高。因此,姜黄素除了与吐温-80的酯基产生氢键作用外,还能与吐温-80烷基链尾部和中部的亚甲基发生作用。     

Multitargeting by curcumin as revealed by molecular interaction studies

Curcumin (diferuloylmethane), the active ingredient in turmeric (Curcuma longa), is a highly pleiotropic molecule with anti-inflammatory, anti-oxidant, chemopreventive, chemosensitization, and radiosensitization activities. The pleiotropic activities attributed to curcumin come from its complex molecular structure and chemistry, as well as its ability to influence multiple signaling molecules. Curcumin has been shown to bind by multiple forces directly to numerous signaling molecules, such as inflammatory molecules, cell survival proteins, protein kinases, protein reductases, histone acetyltransferase, histone deacetylase, glyoxalase I, xanthine oxidase, proteasome, HIV1 integrase, HIV1 protease, sarco (endo) plasmic reticulum Ca(2+) ATPase, DNA methyltransferases 1, FtsZ protofilaments, carrier proteins, and metal ions. Curcumin can also bind directly to DNA and RNA. Owing to its β-diketone moiety, curcumin undergoes keto-enol tautomerism that has been reported as a favorable state for direct binding. The functional groups on curcumin found suitable for interaction with other macromolecules include the α, β-unsaturated β-diketone moiety, carbonyl and enolic groups of the β-diketone moiety, methoxy and phenolic hydroxyl groups, and the phenyl rings. Various biophysical tools have been used to monitor direct interaction of curcumin with other proteins, including absorption, fluorescence, Fourier transform infrared (FTIR) and circular dichroism (CD) spectroscopy, surface plasmon resonance, competitive ligand binding, Forster type fluorescence resonance energy transfer (FRET), radiolabeling, site-directed mutagenesis, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), immunoprecipitation, phage display biopanning, electron microscopy, 1-anilino-8-naphthalene-sulfonate (ANS) displacement, and co-localization. Molecular docking, the most commonly employed computational tool for calculating binding affinities and predicting binding sites, has also been used to further characterize curcumin's binding sites. Furthermore, the ability of curcumin to bind directly to carrier proteins improves its solubility and bioavailability. In this review, we focus on how curcumin directly targets signaling molecules, as well as the different forces that bind the curcumin-protein complex and how this interaction affects the biological properties of proteins. We will also discuss various analogues of curcumin designed to bind selective targets with increased affinity.     

Ferric reducing, antiradical and beta-carotene bleaching activities of nicotinic acid and picolinic acid bioconjugates of curcumin

Although curcumin displays several beneficial properties, its medicinal use is limited by its low bioavailability. In the present study we report the antioxidant potentials of two bioconjugates of curcumin with nicotinic acid and picolinic acid: di-O-nicotinoyl curcumin [1,7-bis (4-O nicotinoyl-3-methoxyphenyl)-1,6-heptadiene-3, 5-dione] and di-O-picolinoyl curcumin [1,7-bis (4-O-picolinoyl-3-methoxyphenyl)-1,6-heptadiene-3, 5-dione], in terms of ferric reducing, radical scavenging and beta-carotene bleaching abilities, and comparing the observed activity with that of curcumin. Results demonstrate that both the bioconjugates possess higher antioxidant potentials as evidenced by enhanced ferric reducing, radical scavenging and beta-carotene bleaching abilities, in comparison with curcumin. On the basis of our results we conclude that these bioconjugates of curcumin may be better than curcumin for medicinal and pharmacological applications.     

荧光探针法研究铜离子-姜黄素体系中1O2的反应机理及在O2·-存在下1O2的测定

以1,3-二苯基异苯并呋喃(1,3-Diphenylisobenzofuran, DPBF)为荧光探针, 研究了姜黄素(Curcumin, CUR)在铜离子催化下产生的单线态氧(1O2), 其反应机理为姜黄素与溶液中的氧分子快速作用产生O2·-和H2O2等活性氧物种, 同时Cu2+与姜黄素形成复合物, 再与H2O2形成过氧化物过渡态, 过氧化物进一步与H2O2发生类Haber-Weiss反应生成1O2, 且只有Cu2+和Cu+离子可催化姜黄素并产生1O2. 1O2在1.37×10-8～3.66×10-7 mol/L浓度范围内与荧光强度下降值ΔIF有良好的线性关系, 检出限为4.12×10-9 mol/L.