线性扫描伏安法测定苏木中苏木精

应用线性扫描伏安法研究了苏木精在玻碳电极上的电化学行为。在pH 5.0的B-R缓冲溶液中,苏木精在0.28 V(vs.SCE)处产生一个灵敏的氧化峰,苏木精浓度在2.24×10-6～1.05×10-4mol.L-1范围内与其线性扫描氧化峰电流呈线性关系,检出限(3S/N)为7.4×10-7mol.L-1。用标准加入法测得方法的回收率在95.2%～104.0%之间。方法用于苏木提取液中苏木精的测定,此法测定结果与高效液相色谱法测定值之间的相对偏差在-3.6%～3.2%之间。     

吸光光度法测定苏木中总酚含量

采用吸光光度法,以苏木精为对照品分析测定了苏木中总酚含量。结果表明,总酚含量在0～16.0μg·ml-1范围内呈良好的线性关系,回归方程为C=10.2569A-0.07901,相关系数为0.9999,检出限为0.17μg·ml-1,加标回收率为95.88%～102.71%,RSD为2.73%。为进一步开发利用苏木的药用价值提供了有效的测试手段。     

聚苏木精修饰玻碳电极测定酪氨酸

通过在玻碳电极上电聚合聚苏木精的方法制备了聚苏木精修饰电极,研究了酪氨酸在修饰电极上的电化学行为。在0.1 mol/L磷酸盐缓冲溶液(pH3.0)中,富集电位为-0.3 V,富集时间为180 s,氧化峰电流与酪氨酸的浓度在5.0×10-6～1.0×10-4mol/L的范围内呈良好的线性关系,检出限为3.0×10-7mo...     

高效逆流色谱法制备苏木中的氧化巴西木素

氧化巴西木素是苏木的主要化学成分之一,具有广泛的药理活性且常作为染色剂应用于各行各业。采用传统柱色谱法进行分离,不仅会造成色谱柱材料的污染,也会造成活性成分的损失。故采用高效逆流色谱(HPCCC)对苏木中的活性化合物氧化巴西木素进行分离纯化。苏木乙醇提取物经乙酸乙酯萃取后直接进行高效逆流色谱分离。首先利用基于薄层色谱的常用溶剂体系估算法和摇瓶法结合高效逆流色谱分析模式进行溶剂体系筛选。结果表明,最佳溶剂体系为氯仿-甲醇-水(4∶3∶2, v/v/v)。高效逆流色谱以反相模式为洗脱模式,主机转速为1600 r/min,流速为10 mL/min,分离温度为25 ℃,检测波长为285 nm,在氯仿-甲醇-水(4∶3∶2, v/v/v)溶剂体系下,从500 mg苏木乙酸乙酯萃取物中一次性分离制备得到15.2 mg纯度为95.6%的氧化巴西木素及一微量成分caesappanin C。采用高效逆流色谱分离制备氧化巴西木素,可避免苏木中的活性成分氧化巴西木素对色谱柱中的固体填充材料染色和难以洗脱等问题,并缩短分离纯化工作时间,提高工作效率。故可将高效逆流色谱应用到苏木中其他色素化合物或其他染料植物的分离制备工艺研究中。     

高效液相色谱法同时测定苏木中的巴西苏木素和原苏木素B

建立了同时测定苏木中巴西苏木素和原苏木素B的高效液相色谱检测方法。采用Agela Venusil XBP-C18(4.6 mm×150 mm,5μm)色谱柱,以甲醇-0.2%甲酸溶液为流动相,梯度洗脱,流速1.0 mL/min,测定温度为35℃,检测波长285 nm。巴西苏木素和原苏木素B的质量浓度均在0.005～1.0 mg/mL时与色谱峰面积之间线性关系良好,相关系数都为0.9999;回收率范围分别为96.7%～101.4%和99.4%～103.0%,相对标准偏差(RSD)为2.0%和1.3%。该法可以用于苏木药材的鉴定。     

钼(Ⅵ)--氧化苏木色精-抗坏血酸--氯化钠体系的显色行为与天然水和尿中钼的简便测定

钼(Ⅵ)-氧化的苏木色精二元体系及钼(Ⅵ)-氧化的苏木色精-抗坏血酸三元体系的酸性水溶液,经沸水浴加热一定时间,出现很灵敏的显色反应,它们用于测钼的表观摩尔吸光系数分别为2.5×10~6和2.14×10~7。本文继续研究钼(Ⅵ)-氧化的苏木色精-抗坏血酸-氯化钠四元体系的显色行为,分光光度测定钼的条件,以及应用于天然水和尿中痕量钼的不分离简便测定。     

苏木素与DNA相互作用的光谱研究

以吖啶橙(AO)作探针研究了苏木素(HE)与DNA的相互作用. 吸收光谱和荧光光谱研究表明, 苏木素与DNA发生作用生成了复合物. 其结合比n_HE∶n_DNA＝3∶1, 22 ℃时苏木素与DNA的结合常数K＝5.96×10⁴ L/mol. 同时研究了酸度、盐效应和温度等对苏木素与DNA相互作用的影响以及它们之间的作用方式, 确定了苏木素与鲱鱼精DNA之间为混合作用方式.     

鲱鱼精DNA的电化学氧化及与组蛋白的相互作用

应用循环伏安法、微分脉冲伏安法和荧光光谱法研究了鲱鱼精DNA的电化学氧化及其与组蛋白的相互作用.结果发现,在0.20~1.25 V电位区间内,DNA在酸性溶液中呈现一个明显的不可逆氧化峰,在中性及碱性溶液中呈现两个不可逆氧化峰.氧化峰电位随溶液pH值增大而负移,变化幅度为-57 mV.pH-1.氧化峰电流与DNA浓度(0.45~8.20 mmol.L-1)成线性关系.DNA能与组蛋白结合,导致氧化电位正移,氧化电流减小,并减弱钌配合物指示剂和DNA相互作用的荧光强度以及减少DNA的氧化损伤.     

青霉素酶-氧化苏木精修饰Au/ZnO/石墨烯基青霉素电化学传感器的研制

采用均匀沉淀法合成ZnO纳米颗粒( ZnO NPs),以ZnO NPs为种子,制备水溶性Au/ZnO异质结构。将Au/ZnO异质结构附着于离子液体功能化石墨烯( GN)复合膜上,形成一种新颖的负载型石墨烯复合材料(Au/ZnO/GN)。所构建的青霉素酶-氧化苏木精修饰Au/ZnO/GN(PH-AZG)传感器在PBS水溶液(pH=7.0)中对青霉素钠检测线性范围为2.5×10-14~3.3×10-6 mol/L,检出限达到1.5×10-14 mol/L (S/N≥3)。在相同条件下制备5根PH-AZG电极,其响应电流的相对标准偏差(RSD)小于3.2%。同时,在实际牛奶制品中,本方法的检测线性范围为5×10-14~5×10-7 mol/L,加标回收率为99.7%~101.4%,RSD 为2.3%~3.5%(n=5)。结果表明,本方法对实际牛奶制品中低浓度青霉素钠的检测具有可行性。     

光泽精在肾上腺素自氧化体系中的电化学研究

光泽精与在肾上腺素自氧化体系中（ｐＨ＝１０．２０）产生的超氧阴离子自由基反应,其氧化产物在 －１．１６ Ｖ（ｖｓ．ＳＥＣ）和－１．６０Ｖ（ｖｓ． ＳＥＣ）处有两个还原峰,其中－１．１６ Ｖ处的还原峰是光泽精被氧化的中 间产物的双电子还原峰,－１．６０Ｖ处的还原峰是最终产物 Ｎ－甲基吖啶酮（ＮＭＡ）的双电子还原峰。形成 反应中间体和 ＮＭＡ的反应是一级反应,其反应速度常数分别为 ２．０７× １０－４ｓ－１和 ２．２３ × １０－５ｓ－１。     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

Synthesis of pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles by Curtius reaction in Morita-Baylis-Hillman derivatives

Synthesis of substituted pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles from the Morita-Baylis-Hillman derivatives of acrylates via saponification followed by Curtius reaction is described.     

正丁胺对激光染料荧光谱影响的研究

用正丁胺作为碳源,采用射频辉光放电制备碳膜,选用激光染料R6G和聚乙二醇混合液作为蒸气源,采用单源热蒸发,在蒸发室与染料同时沉积得到混合膜,用拉曼光谱和红外光谱分析了碳膜的结构和键合方式,分析表明:碳膜中存在胺基团和氢原子.混合膜的荧光谱测量结果表明,认为正丁胺对染料荧光谱的影响是因为胺基和氢原子的存在.     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.