Coenzyme B12 model studies: Equilibrium constants for the pH-dependent axial ligation of benzyl(aquo)cobaloxime by various N- and S-donor ligands

Equilibria of the axial ligation of benzyl(aquo)cobaloximes by imidazole, 1-methyl imidazole, histidine, histamine, glycine, ethyl glycine ester, thiourea and urea have been spectrophotometrically measured in aqueous solutions of ionic strength 1.0M (KCl) at 25°C as a function of pH. The equilibrium constants are in the order CN⁻> 1-methyl imidazole > imidazole > histidine > histamine>glycine>ethyl glycine ester > thiourea > urea. The order of stability of benzyl(ligand)cobaloxime is explained based on the basicity of the ligand, Co(III) →>L dπ- pπback bonding and soft-soft and soft-hard interaction. Imidazole, substituted imidazoles, histidine and histamine form more stable complexes than glycine, ethyl glycine ester in contrast to the basicity of the ligands. Benzyl(ligand)cobaloximes were isolated and characterized by elemental analysis, IR and¹H NMR spectra.     

s-BLM修饰电极对组胺电化学传感行为的研究

The electrochemical biosensor properties of the molecular devices based on solid supported bilayer lipid membranes were investigated. The results showed that the system embedded with antihistaminic agent had strong response for the histamine. The response currents for the histamine will rise following the increasing concentrations of the histamine,as a result of the special opposing effect between histamine and antihistamine. Near the normal physiological condition（pH=7. 5）,a good linearity occurred for the current response against histamine concentration ranging from 3. 0 to 60. 0 μg / L,and the relation coefficient R is 0. 9878. All the experiments mentioned above showed good sensitivity,selectivity and stability. This system can measure the concentration of histamine under -200 mV by voltammetry and be expected to form the electrochemical biosensor with high stability and low detection limit.     

Determination of histamine and histidine by capillary zone electrophoresis with pre-column naphthalene-2,3-dicarboxaldehyde derivatization and fluorescence detection

A rapid and sensitive method was developed for the simultaneous determination of histamine and histidine by capillary zone electrophoresis with lamp-induced fluorescence detection. A fluoregenic derivatization reagent, naphthalene-2,3-dicarboxaldehyde (NDA) was successfully applied to label the histamine and histidine respectively. The derivatization conditions and separation parameters including pH and concentration of electrolyte and sample injection were optimized in detail. The optimal derivatization reaction was performed with 1.0 mM NDA, 20 mM NaCN, and 20 mM borate buffer, pH 9.1 for 15 min. The separation of NDA-tagged histamine and histidine could be achieved in less than 200 s with 40 mM phosphate buffer (pH 5.8) as the running buffer. The detection limits for histamine and histidine were 5.5 x 10(-9) and 3.8 x 10(-9) M, respectively (S/N = 3). The relative standard derivations for migration time and peak height of derivatives were less than 1.5 and 5.0%, respectively. The method was successfully applied to the analysis of histamine and histidine in the P815 mastocytoma cells and the beer samples.     

Unified approach to the sesquiterpenoids,lauranes and cyclolauranes: Total synthesis of (±)-isolaurene

A general approach to the total synthesis of sesquiterpene, isolaurene (1a) and cyclolaurene (2a) is featured from commercially available 3-methyl cyclopenten-2-one. The strategy includes a Stork-Danheiser sequence concomitant with a Ni(II)-catalyzed conjugate addition of methyl group onto 3-aryl 2-methyl cyclopenten-2-one to afford the advanced intermediate 11. A methyllithium addition onto compound 11 with an eventual dehydration completed the total synthesis of isolaurene (1a) in 5 steps (58.3% overall yields).     

Electrophoretic separation strategy for chiral pharmaceuticals using highly-sulfated and neutral cyclodextrins based dual selector systems

The enantiomeric separation of chiral pharmaceuticals was investigated using dual systems with mixtures of cyclodextrin derivatives. The dual cyclodextrin systems, consisting of one highly-sulfated (α-, β-, and γ-HSCD) and one neutral cyclodextrin, i.e. either heptakis (2,3,6-tri-O-methyl)-β-CD (TMCD), heptakis (2,6-di-O-methyl)-β-CD (DMCD) or hydroxypropyl-β-CD (HPCD), are tested on 25 pharmaceutical compounds with different acid-basic properties (16 basics, 8 acids and 1 neutral). The influence on the separation of the type and concentration of neutral CD in highly-sulfated cyclodextrins-based dual selector systems, is investigated. For 11 of 16 basic compounds, a better separation is obtained with the CD mixtures compared to the use of only a highly-sulfated CD. Mixtures with TMCD give better results than those with DMCD and HPCD. Results showed that dual CD systems are useful to achieve and to optimise chiral separations of compounds not (sufficiently) separated with HSCDs alone. For example, ibuprofen was not resolved with α-, β- or γ-HSCD, but could be separated with the mixture 25 mM TMCD and 5% HS-β-CD. Based on the obtained results, a dual CD systems based separation strategy is defined.     

基于径向基神经网络和遗传算法的槽内式选择性超声电合成甲基苯甲醛

以混合二甲苯为原料, Mn(Ⅲ)为氧化剂, 硫酸溶液为电解质, 采用槽内式超声电合成甲基苯甲醛. 探讨了选择性电合成甲基苯甲醛的可能性, 通过径向基(RBF)神经网络和遗传算法(GA)对选择性电合成甲基苯甲醛3种异构体的比例、 电流效率与混合二甲苯的用量、 硫酸浓度和电流强度的关系建立预测模型, 并运用GA确定模型中RBF神经网络的目标均方误差(Goal)和径向基函数的分布(Spread). 然后根据预测模型, 使用GA对电合成条件进行优化, 分别获得了电合成产物中对位甲基苯甲醛占优、 邻位和对位甲基苯甲醛占优以及电流效率最高时的电合成条件. 当采用上述条件进行实验时, 模型给出的预测结果分别为: 对位甲基苯甲醛占优的质量分数可达90.01%, 邻位和对位甲基苯甲醛占优的质量分数为80.38%, 电流效率达到最高时的邻位、 间位和对位甲基苯甲醛的质量分数分别为16.80%, 8.43%和74.77%; 而与之相对应的实际实验结果分别为90.10%和79.91%, 以及17.20%, 8.49%和74.31%, 二者之间的最大相对误差小于±2.24%, 表明所建立模型的预测值与实测值基本吻合.     

Kinetics of copolymerization and degradation of poly[acrylonitrile-co-(amino ethyl-2-methyl propenoate)]

Amino ethyl-2-methyl propenoate was firstly used to successfully copolymerize with acrylonitrile in a H₂O/dimethylsulfoxide (DMSO) mixture between 50 °C and 70 °C under N₂ atmosphere. This was achieved by using azobisisobutyronitrile as the initiator. Kinetics of copolymerization of acrylonitrile with amino ethyl-2-methyl propenoate was investigated. The kinetic equation of copolymerization was obtained and the apparent activation energy of degradation of poly[acrylonitrile-co-(amino ethyl-2-methyl propenoate)] was determined. Increasing DMSO concentration in the solvent mixture leads to a rapid increase in the degradation apparent activation energy. The apparent activation energy decreases quickly with an increase in the comononer amino ethyl-2-methyl propenoate concentration, and such a change becomes less prominent as the molar ratio of amino ethyl-2-methyl propenoate/acrylonitrile goes beyond 2/100. The apparent activation energy also increases along with the copolymerization temperature. The resultant fibers prepared from poly[acrylonitrile-co-(amino ethyl-2-methyl propenoate)] were obtained with the fineness at 1.03 dtex and the tenacity at 6.18cN dtex⁻¹.     

Enantiomeric purity of (+/-) -methyl jasmonate in fresh leaf samples and commercial fragrances

The enantiomeric purity of (+/-) -methyl jasmonate in fresh leaf material of Jasminum from different species and Rosmarinus officinalis was examined by solid-phase microextraction-GC-MS (SPME-GC-MS). For comparison with these natural products, commercial jasmine and rosemary fragrances were also studied. The extraction conditions were selected as a result of testing different values of temperature (40, 50, and 60 degrees C) and time (2, 15, 30, and 40 min). The results obtained in this work revealed a range of enantiomeric excesses for (+/-) -methyl jasmonate varying from 13 to 95% depending on the Jasminum specie considered. In contrast, (-) -methyl jasmonate always occurred as a pure enantiomer in all R. officinalis samples studied. This implies those Jasminum species in which the enantiomeric purity of (-) -methyl jasmonate is high enough and any R. officinalis sample might be used as natural sources of pure (-) -methyl jasmonate. Concerning the commercial fragrances, those of jasmine showed enantiomeric composition of (-) -methyl jasmonate ranging from 1 to 15% whereas those of rosemary exhibited practically the pure (-) -methyl jasmonate. This fact suggests the addition and nonaddition of the racemic mixture of methyl jasmonate to the commercial jasmine and rosemary samples, respectively.     

Brönsted酸性离子液体催化芳香醛和2-甲基喹啉反应合成1,3-二(2-喹啉基)丙烷化合物

以Brönsted酸性离子液体1-乙基-3-丁基咪唑对甲苯磺酸盐为催化剂, 将芳香醛和2-甲基喹啉类化合物在无溶剂或甲苯中于120 ℃反应48 h, 制备了一系列的1,3-二(2-喹啉基)丙烷化合物, 产率56%~92%, 产物结构经核磁共振波谱和高分辨质谱确证. 该方法具有简便易行、 产率较高等特点.     

Kinetics and mechanism of chlorination of toluene and some substituted toluenes by chloramine-T

The kinetics of chlorination of toluene, o-methyl toluene, p-methyl toluene, m-methyl toluene, and m-chlorotoluene by chloramine-T(CAT) in aqueous acetic acid in the presence of HClO₄ have been studied. The reaction is first order with respect to [CAT] as well as [H⁺]. The order with respect to the substrate is unity in the case of toluene and m-chlorotoluene, fractional in the case of o-methyl toluene and p-methyl toluene, and zero order in the case of m-methyl toluene. Nuclear halogenation has been observed with m-methyl toluene, while nuclear and side-chain halogenation for p-methyl toluene and o-methyl toluene, and sidechain halogenation for toluene and m-chlorotoluene are the pathways. An increase in the proportion of acetic acid accelerates the rate. Added acetate ions inhibit the reaction, and added p-toluene sulfonamide causes a pronounced retardation. A mechanism involving AcO⁺HCl as the important electrophile is discussed.     

THE PHOTOTOXIC EFFECT OF BENOXAPROFEN AND ITS ANALOGS ON HUMAN ERYTHROCYTES AND RAT PERITONEAL MAST CELLS

Abstract— Benoxaprofen [2-(4-chlorophenyl)-α-methyl-5-benzoxazoleacetic acid] is a phototoxic non-steroidal anti-inflammatory agent. Irradiation of human erythrocytes in the presence of benoxaprofen (8 μ M ) and oxygen resulted in rapid cell lysis which began after 10 min and was complete within 30 min. While photohemolysis was also observed under anerobic conditions, its onset was delayed for more than 20 min and it took nearly 100 min for complete lysis to occur. Photohemolysis was also delayed by butylated hydroxyanisole but was unaffected by reduced glutathione. 1,4-diazabicyclo[2.2.2]octane, D₂O. β-carotene, or superoxide dismutase. The main photoproduct of benoxaprofen, 2-(4-chlorophenyl)-5-ethylbenzoxazole, was almost as effective in causing photohemolysis as benoxaprofen itself. In the presence of UV irradiation, benoxaprofen (10 (μ M ) caused the degranulation of rat peritoneal mast cells and the release of histamine. The release of mast cell histamine may provide a reasonable explanation for the urticarial response to benoxaprofen and irradiation seen in human subjects.     

Profiling and characterisation by liquid chromatography/multi-stage mass spectrometry of the chlorogenic acids in Gardeniae Fructus

The chlorogenic acids of Gardeniae Fructus used traditionally as a Chinese herbal medicine (zhizi) have been investigated qualitatively by liquid chromatography/multi-stage mass spectrometry (LC/MS(4)). Twenty-nine chlorogenic acids were detected and twenty-five characterised to regioisomer level on the basis of their fragmentation, twenty-four for the first time from this source. Assignment to the level of individual regioisomers was possible for three caffeoylquinic acids, three dicaffeoylquinic acids, three sinapoylquinic acids, four caffeoyl-sinapoylquinic acids, two feruloyl-sinapoylquinic acids, one p-coumaroyl-sinapoylquinic acid, three (3-hydroxy, 3-methyl)glutaroylquinic acids, two (3-hydroxy, 3-methyl)glutaroyl-feruloylquinic acids, one (3-hydroxy, 3-methyl)glutaroyl-dicaffeoylquinic acid, and one (3-hydroxy, 3-methyl)glutaroyl-caffeoyl-feruloylquinic acid. Six (3-hydroxy, 3-methyl)glutaroyl-caffeoylquinic acids were detected and two were tentatively assigned as 3-caffeoyl-4-(3-hydroxy, 3-methyl)glutaroylquinic acid and 3-caffeoyl-5-(3-hydroxy, 3-methyl)glutaroylquinic acid. The (3-hydroxy, 3-methyl)glutaroyl residue modifies the mass spectral fragmentation behavior and elution sequence compared with the chlorogenic acids that contain only a cinnamic acid residue(s). Fourteen of these twenty-nine chlorogenic acids have not previously been reported from any source.     

一步法制备含W介孔碳材料及其氧化脱硫性能研究

以钨酸钠为钨源,以乙二胺四乙酸二钠为碳源经过高温煅烧制备了含W的介孔碳材料,采用XRD、SEM、FT-IR、BET对含钨的介孔碳材料进行表征。结果表明,煅烧后介孔碳材料的表面形成了粒状含有结晶水的氧化钨(WO_3·H_2O)。相比于纯的介孔碳材料,含钨介孔碳材料的总比表面积减小。以含W介孔碳材料为催化剂,H_2O_2作为氧化剂,1-丁基-3-甲基咪唑氟硼酸盐([BMIM][BF_4])离子液体作为萃取剂,组成萃取-催化氧化脱硫体系(ECODS)并研究其对模拟油中二苯并噻吩脱除效果。考察了氧化钨负载量、反应温度、H_2O_2加入量、催化剂用量、离子液体用量以及不同类型硫化物对二苯并噻吩脱除的影响。在最佳反应条件下,催化剂对二苯并噻吩(DBT)、4,6-二甲基二苯并噻吩(4,6-DMDBT)、苯并噻吩(BT)、噻吩(TH)和真实汽油的脱除率分别达到98.6%、65.6%、61.2%、57.8%和64.3%。催化剂回收利用五次之后脱硫率略有降低,仍高达95.2%。     

Total syntheses of (-)-methyl atis-16-en-19-oate, (-)-methyl kaur-16-en-19-oate, and (-)-methyl trachyloban-19-oate by a combination of palladium-catalyzed cycloalkenylation and homoallyl-homoallyl radical rearrangement

Asymmetric total syntheses of (-)-methyl atis-16-en-19-oate (1c), (-)-methyl kaur-16-en-19-oate (2c), and (-)-methyl trachyloban-19-oate (3c) have been achieved by employing a hybrid strategy of palladium-catalyzed cycloalkenylation and homoallyl-homoallyl radical rearrangement. The common synthetic intermediate 5 was prepared from 2-allylcyclohexanone (4) with 98% ee using d'Angelo's asymmetric Michael addition. A series of functional group modifications in 5 via palladium-catalyzed cycloalkenylation led to (+)-14, which had already been prepared by us as racemate. (-)-Methyl atis-16-ene-19-oate (1c) was generated via homoallyl-homoallyl radical rearrangement. On the other hand, Wolff-Kishner reduction of 18 followed by esterification yielded (-)-methyl kaur-16-en-19-oate (2c) together with (-)-methyl trachyloban-19-oate (3c).     

Sensitive and rapid simultaneous quantitation of leucovorin and its major active metabolite 5-methyl-tetrahydrofolate in human plasma using a liquid chromatography coupled with triple quadruple mass spectrometry

Bioanalysis of an endogenous compound such as leucovorin is never an easy task on a liquid chromatography tandem mass spectrometer (LC–MSMS). Unless it is necessary, regulatory guidance discourages working with surrogate matrices for calibration curve standard preparation. Herein, a selective and sensitive liquid chromatography–tandem mass spectrometry method for simultaneous determination of leucovorin and 5-methyl tetrahydrofolic acid in human plasma was developed and validated. Stable labeled internal standards, i.e. leucovorin D₄ and 5- methyl tetrahydrofolic acid ¹³C₅, were used as internal standards to track and compensate the parent compounds during processing and extraction from plasma. The method involves a rapid solid-phase extraction from plasma followed by reverse-phase gradient chromatography and mass spectrometry detection with a total run time of 5 min. The method was developed and validated from 5 to 2,202 ng/ml for leucovorin and from 5 to 1,300 ng/ml for 5-methyl tetrahydrofolic acid. The mean recoveries for leucovorin and 5-methyl tetrahydrofolic acid were 100.4 and 100.9% respectively. The validated method enabled the simultaneous analysis of leucovorin and 5-methyl tetrahydrofolic acid in samples from clinical pharmacokinetic studies of leucovorin. The peak concentrations of leucovorin and 5-methyl tetrahydrofolic acid were 651–883 and 518–635 ng/ml, respectively, in fasted and fed conditions. The terminal half-life values for leucovorin and 5-methyl tetrahydrofolic acid were 9.3–10.5 and 9.2–17.6 h, respectively.     

The affinity of histamine to serum albumin: Capillary electrophoresis-frontal analysis and in-silico molecular docking approaches

Histamine is a biogenic amine found in various body tissues and responsible for many critical vital activities. It is also responsible for allergic reactions in the body. Ingestion of foods containing high amounts of histamine can cause fatal allergic reactions. Albumin in plasma controls drugs and free concentrations of bioactive constituents taken to the body with food. Hence, this study aimed to characterise the interactions of histamine with bovine serum albumin. Capillary electrophoresis in the frontal analysis mode was employed in this study as a practical approach for assessing histamine-bovine serum albumin affinity. The plateau-shaped free histamine peak was well separated from the bovine serum albumin (BSA)-histamine complex peak. The free histamine concentration was obtained by following the height of the free histamine peak. Whereas the bound histamine concentrations were obtained by calculating the difference between the height of total and free histamine peaks. Histamine bound to BSA at one independent site with a K_b value of 2.50 × 10³ L/mol. Moreover, an in-silico molecular docking method was performed, and it was revealed that the binding site of histamine was located closer to Lysine-131 in subdomain IIA of bovine serum albumin.     

Electrochemical determination of histamine derivatized with o-phthalaldehyde and 2-mercaptoethanol

High-performance liquid chromatography coupled with electrochemical detection was used to determine histamine following precolumn derivatization with o-phthalaldehyde (OPA) and 2-mercaptoethanol. The isoindole derivative which is obtained as reaction product was electrochemically active at a moderate potential (peak potential +0.4 V). Direct oxidation of histamine required a much higher potential (peak potential +1.05 V) and was of no practical use. No electrochemical signal was observed for the reaction product of histamine with OPA. Changing the pH of the mobile phase had little effect on the electrochemical response of the isoindole derivative of histamine, which was well separated from analogous derivatives of methylated histamines, mono- and polyamines and amino acids by isocratic elution from a reversed-phase column. An example of a practical application of the method to the estimation of histamine in rat brain is presented.     

Energetic analyses of chair and boat conformations of maleimide substituted cyclohexane derivatives

An analysis of the conformational preferences of two maleimide substituted cyclohexane derivatives proposed as scaffolds for HIV-1 fusion inhibitors is presented. Hybrid Low Mode-Monte Carlo (1:1) conformational searches using seven different force fields were performed in combination with the GBSA(water) solvent model. Low energy structures identified in this way were subjected to geometry optimization on the B3LYP/6-31G** surface. Solvent effects were included in the quantum calculation using the self-consistent reaction field model for water. Quantum results indicate that the 1,3,5-maleimide functionalized 1,3,5-methyl cyclohexane is more stable in the boat conformation, whereas 1,3,5-maleimide functionalized cyclohexane adopts the expected chair conformation with equatorial arms. None of the force fields studied was able to predict the unexpected preference for the boat conformation of 1,3,5-maleimide functionalized 1,3,5-methyl cyclohexane. Comparison of low energy and experimental structures was also performed.     

Flow-through chemiluminescence sensor using immobilized histamine oxidase from Arthrobacter crystallopoietes KAIT-B-007 and peroxidase for selective determination of histamine.

A flow sensor with immobilized oxidases is proposed for the determination of histamine in fish meat. Chemiluminometric measurement of histamine was based on the luminol reaction with hydrogen peroxide produced by immobilized histamine oxidase (EC 1.4.3.-.) and peroxidase (EC 1.11.1.7.) within a flow cell. Histamine oxidase was found in cells of Arthrobacter crystallopoietes KAIT-B-007 isolated from soil. The oxidase and peroxidase were coimmobilized covalently on tresylated hydrophilic vinyl polymer beads and packed into transparent PTFE; the tubing was used as the flow cell. One assay for histamine was done at intervals of 2 min without carryover. The calibration curve for histamine was linear from 0.1 microM to 50 microM. The response was reproducible within 1.25% of the relative standard deviation for 115-replicate injections of 50 microM histamine. The sensor system was applied to the determination of histamine in fish meat extracts.     

Transformation of steroidal cyclohexadienyl anion without fragmentation: Unexpected synthesis of methylenesteroid

In contrast with androsta-1,4-diene-3α/β, 17β-diol, its 3-O-methyl ether is transformed upon C(3)-deprotonation into the corresponding 3-methylene steroid with migration of theO-methyl group on the steroid skeleton (by the scheme of Wittig rearrangement) rather than eliminating the 19-methyl group. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1393–1395, July, 1999.