荧光法研究三种黄酮小分子与溶菌酶的相互作用

用荧光光谱法研究了芹菜素(Quercetin)、木犀草素(Luteocin)、槲皮素(Quercetin)与溶菌酶的相互作用, 对比了C3'—OH和C3—OH取代对黄酮与溶菌酶作用的影响. 结果表明, C3'—OH可大大增强黄酮与溶菌酶之间的作用, C3—OH的取代则导致作用力减弱. 根据3种黄酮的结构参数, 初步分析了C3'—OH和C3—OH取代对黄酮与蛋白相互作用的影响.     

蒲公英黄酮抗氧化活性的构效关系分析

蒲公英作为传统的中药材,具有抗氧化、抗肿瘤、抗菌、抗炎等多种药用价值。黄酮是蒲公英发挥抗氧化作用的重要活性成分。蒲公英黄酮抗氧化性能的实验研究备受关注,然而从分子水平对蒲公英黄酮结构与抗氧化活性之间的内在关系缺乏系统的研究。本文借助于密度泛函理论,针对蒲公英中5种重要的黄酮化合物(槲皮素、芦丁、木犀草素、芹菜素、香叶木素),通过优化结构参数、捕获DPPH自由基的热力学能量分析,NBO电荷分布、半醌自由基的自旋密度分析等方面深入探讨了蒲公英黄酮化合物抗氧化活性的构效关系及内在规律。结果表明：5种蒲公英黄酮化合物抗氧化活性为芦丁>槲皮素>木犀草素>>香叶木素>芹菜素,酚羟基的位置是影响蒲公英黄酮抗氧化活性差异的主要因素。蒲公英黄酮不同位点抗氧化活性的高低与其酚羟基上H原子的电荷分布、黄酮自由基的稳定性成正比关系,自由基单电子的离域程度和分子内氢键的稳定化作用共同决定了B环4’-OH是蒲公英黄酮的关键活性位点。     

不同取代羟基黄酮类化合物与血清白蛋白的相互作用分析

采用荧光光谱法研究了3种具有不同取代羟基的黄酮类化合物芹菜素、染料木素和高良姜素与牛血清白蛋白(BSA)之间的相互作用,测定了3种黄酮化合物与BSA的结合常数和结合位点,并分析了它们对BSA的荧光猝灭过程及其之间的相互作用类型,同时利用同步荧光和紫外吸收光谱探讨了它们对BSA构象的影响.结果表明,3种黄酮类化合物分子中的羟基数目以及位置对各化合物与BSA的作用有重要影响,导致水溶液中这3种黄酮类化合物与BSA发生相互作用的强弱不同,其作用力顺序为芹菜素>高良姜素>染料木素.     

固相萃取/液相色谱一质谱/质谱法测定山银花中5种主要黄酮苷元的含量

该文通过含有盐酸的乙醇溶液回流水解并提取,HLB固相萃取柱净化,液相色谱一质谱/质谱法检测,建立了山银花中槲皮素、木犀草素、山萘酚、芹菜素和黄芩素5种黄酮苷元含量的测定方法.实验以芦丁、木犀草苷、紫云英苷、野漆树苷和黄芩苷5种黄酮苷为代表开展研究,山银花样品经50％的乙醇溶液(含10％浓盐酸)回流2h水解黄酮苷,同时对...     

固相萃取/液相色谱-质谱/质谱法测定山银花中5种主要黄酮苷元的含量

该文通过含有盐酸的乙醇溶液回流水解并提取,HLB固相萃取柱净化,液相色谱-质谱/质谱法检测,建立了山银花中槲皮素、木犀草素、山萘酚、芹菜素和黄芩素5种黄酮苷元含量的测定方法。实验以芦丁、木犀草苷、紫云英苷、野漆树苷和黄芩苷5种黄酮苷为代表开展研究,山银花样品经50%的乙醇溶液(含10%浓盐酸)回流2 h水解黄酮苷,同时对黄酮苷元进行提取,HLB固相萃取柱净化,采用Mightysil RP-18色谱柱分离,液相色谱-质谱/质谱法检测(电喷雾离子源、多反应监测模式、负离子扫描),外标法定量测定水解后的5种黄酮苷元含量。方法的定量下限(S/N=10)为0.005 g/kg(槲皮素),0.01 g/kg(木犀草素和芹菜素)和0.05 g/kg(山萘酚和黄芩素)。在0~1.0 g/kg范围内,5种黄酮苷元的线性相关系数均大于0.995;在山银花样品中对待测物进行3种加标水平的回收实验(加标水平相当于水解后槲皮素和木犀草素含量为:0.10、0.20、0.40 g/kg,山萘酚、芹菜素和黄芩素含量为:0.05、0.10、0.20 g/kg),方法的平均回收率70.4%~104%;相对标准偏差为4.0%~12%。该方法实现了山银花中多种主要黄酮苷元含量的同时测定,且对研究山银花药效及与黄酮类化合物的关系具有重要意义。     

固定化离子液体吸附黄酮类化合物性能研究

研究了吸附时间、固液比、样品浓度、上样流速对N-甲基咪唑键合硅胶固定化离子液体(SilprMim)吸附黄酮类化合物性能的影响.结果表明,受试化合物在30 min内均达到吸附平衡;吸附效率随固液比增大而增加,随样品浓度增大而降低;吸附等温线与拟合的Langmuir模型吻合良好.SilprMim对染料木素、木犀草素及槲皮素的饱和吸附量分别为47.7, 52.5和63.2 mg/g,上样流速在0.5～1.5 mL/min范围内吸附效率达90%以上;甲醇洗脱染料木素、木犀草素及槲皮素的解吸率分别为86.1%, 83.3%和84.6%;解吸顺序为:染料木素、木犀草素、槲皮素.SilprMim对3种受试黄酮类化合物具有较强吸附和分离能力,有望应用于黄酮类天然产物的分离纯化.     

Ce(VI)与6种天然黄酮化合物的氧化还原体系及其应用

选取结构相近的6种天然黄酮化合物：槲皮素(Quercetin)、山奈酚(Kaempferol)、木犀草素(Luteolin)、柚皮素(Naringenin)、黄芩素（Baicalein）和芹菜素（Apigenin）,利用紫外可见分光光度法,结合微量滴定手段,追踪并记录了6种黄酮化合物与Ce(Ⅳ)形成的氧化还原体系的紫外吸收信号,根据化合物对Ce(Ⅳ)响应差异,探讨了不同位置酚羟基对化合物抗氧化活性的贡献及作用机制。 结果表明,色原酮C环上3-OH首先与Ce(Ⅳ)作用,发生质子解离而氧化,其氧化产物在294 nm产生较强的吸收峰,3′,4′邻位-OH有利于在氧化剂Ce(Ⅳ)存在时4′羟基解离形成分子内氢键,紫外吸收光谱带Ⅱ的双峰会明显分离。 其它位置的酚羟基也会对Ce(Ⅳ)产生响应,且C环上的羟基比A环上的更灵敏。 同时,低浓度的黄酮会引起Ce(Ⅳ)的吸光度明显降低,由此得出6种化合物抗氧化能力顺序为Quercetin＞aempferol＞Luteolin＞Apigenin＞Baicalein＞Naringenin,与化合物的紫外吸收光谱响应灵敏度一致。     

大豆素和染料木素的光氧化自由基反应动力学

具有共轭电子结构和多酚羟基官能团的类黄酮是天然抗氧化剂,其活性位点及其自由基稳定性是影响抗氧化效能的重要因素. 我们通过时间分辨光谱并结合量化计算对比研究了大豆素和染料木素两种异黄酮的脱质子形式由光氧化引发的自由基反应动力学. 结果表明,光氧化大豆素的酚氧阴离子先产生不稳定的中间态自由基,随后通过分子内电子转移反应生成相对稳定的自由基;异黄酮染料木素的酚氧阴离子光氧化后直接生成自旋密度在整个分子骨架上离域的稳定自由基;染料木素的5位羟基起到增强4’位酚羟基抗氧化活性的作用. 这些结果解释了染料木素远高于大豆素的抗氧化活性.     

高效液相色谱法测定丰城鸡血藤中四种黄酮类化合物

用HPLC法测定了丰城鸡血藤中的大豆黄素、染料木黄酮、异甘草素、美皂异黄酮含量。鸡血藤中黄酮用80%乙醇溶液(含盐酸10%)提取水解。采用Symm etry C18柱,以0.1%磷酸-乙腈为流动相,梯度洗脱,流速0.8 mL.m in-1,紫外双波长检测:λ1=260 nm(大豆黄素、染料木黄酮、美皂异黄酮)和λ2=370 nm(异甘草素)。大豆黄素、染料木黄酮、异甘草素、美皂异黄酮线性范围分别为2.08~208 mg.L-1(r=0.999 9)、0.96~96 mg.L-1(r=0.999 9)、1.12~44.8 mg.L-1(r=0.999 9)、1.16~116 mg.L-1(r=0.999 9),回收率在92%~103%之间,RSD(n=4)为0.75%~4.69%。实验结果表明该法快速、简便、准确可靠。     

MSPE-HPLC法测定甘青青兰中5种黄酮化合物

建立了磁固相萃取-高效液相色谱法(MSPE-HPLC)同时测定甘青青兰中5种黄酮化合物的方法。优化了甘青青兰中木犀草素苷、香叶木素-7-O-葡萄糖苷、木犀草素、芹菜素和金合欢素等5种黄酮化合物的磁固相萃取条件,并同时测定其含量。结果表明,甘青青兰中这5种黄酮化合物的线性范围分别在1. 0～15,0. 8～12,1. 6～24,1. 2～18,0. 6～9. 0μg/mL之间,相关系数r≥0. 9992,平均回收率在96. 4%～107. 9%之间。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.