盐酸吡哆辛及其制剂的二阶导数差示脉冲极谱法定量研究

建立盐酸吡哆辛及其制剂的二阶导数差示脉冲极谱定量分析方法。盐酸吡哆辛在0.1mol/L氢氧化钠溶液-0.1moL/L磷酸二氢钾溶液-水(体积比为1.2:8.8:990)的混合溶液中,于-0.140V(vs·Ag/AgCl)处出现一良好的二阶导数差示脉冲极谱峰,盐酸吡哆辛浓度在3.6×10~(-4)～9.6×10~(-4)mol/L范围内与其峰幅值呈显著的线性关系(P<0.01),线性相关系数r=0.9997,检出限为9.0nmol/L。     

Interactions of native and modified cyclodextrins with some B-vitamins

Interactions of native and modified α- and β-cyclodextrins with nicotinic acid, pyridoxine and pyridoxal were studied by isothermal titration calorimetry, solution calorimetry, and ¹H NMR spectroscopy at 298.15 K and pH 6.8. Weak 1:1 complex formation was found only between α-cyclodextrin and nicotinic acid. The stability constant and corresponding thermodynamic parameters of complex formation (Δ_c G, Δ_c H and Δ_c S) were calculated using the calorimetric data. The ¹H NMR data indicate the shallow insertion of the carboxylic group of the nicotinic acid molecule into α-CD cavity. For all other compounds the weak interactions, not accompanied by complex formation, were characterized by the enthalpic virial coefficients calculated on the basis of McMillan-Mayer approach. The obtained thermodynamic parameters were analyzed in the terms of influence of the solutes’ structure on the selectivity of intermolecular host-guest interactions.     

Thermodynamics of the solution equilibria of 3-hydroxypyridine and pyridoxine in water-dioxane mixtures

The thermodynamics of tautomeric and microscopic ionization equilibrium constants of 3-hydroxypyridine and pyridoxine have been determined in waterdioxane mixtures (0–70% weight fraction in dioxane) ranging from 10°C to 50°C. Generally, for both types of processes, the entropic contributions to the Gibbs energy predominate and this tendency increase concomitantly with the dioxane content in the media. The thermodynamic parameters are consistent with the corresponding values obtained from macroscopic ionization processes. An equation for the equilibrium constant K as a function of temperature and a solvent characteristic parameter is proposed to predict the K values throughout the whole range of the temperature and solvent compositions studied.     

吡哆辛的光分析法及应用

吡哆辛(VB6)在碱液中有强的光(λex316nm,λem444nm,寿命1.8s),经紫外光照射后光消失.光照前后光强度差(ΔP)与吡哆辛含量呈线性关系.建立了吡哆辛的低温光分析法,并应用于制剂及一些生物组织中吡哆辛含量分析.     

The uptake of Mn-DPDP by hepatocytes is not mediated by the facilitated transport of pyridoxine

Manganese-dipyridoxal diphosphate (Mn-DPDP) is a liver-selective contrast agent selectively taken up by the hepatocytes. Because of the analogy of structure with pyridoxine (vitamin B₆), it was previously suggested that this compound can be selectively taken up by the facilitated transport of vitamers B₆. To understand the uptake mechanism, an in vivo binding study was performed based on a competition between ⁵⁴Mn-DPDP and pyridoxine on the one hand, and Mn-DPDP and [³H]pyridoxine on the other. We found that the [³H]pyridoxine levels in the liver were not significantly different 5 min after intravenous administration of several doses of Mn-DPDP (5 nmol/kg to 50 μmol/kg): 5.0 ± 0.3% of the injected dose/g tissue. The content of ⁵⁴Mn (administered as ⁵⁴Mn-DPDP) in the liver was not affected by a saturation dose of pyridoxine (1 mmol/kg) and was found to be constant (±10% of the injected dose/g tissue) for 60 min. These experiments showed that the uptake of Mn-DPDP is not mediated by the transporter of pyridoxine.     

盐酸吡哆辛在聚烟酸修饰电极上的电化学行为及测定

采用电聚合方法制备了聚烟酸修饰玻碳电极(PNA/GCE),并利用循环伏安法(CV)和差分脉冲伏安法(DPV)考察了盐酸吡哆辛(VB6)在该修饰电极上的电化学行为。结果表明,VB6在PNA/GCE上的氧化峰电流显著提高,电极反应为扩散控制的一电子两质子反应。利用差分脉冲伏安法对VB6进行测定,线性范围为0.08~400μmol/L,VB6的检出限为0.02μmol/L,测定结果的相对标准偏差为3.1%(n=8),加标回收率为95.8%~103.7%。该方法可用于VB6片中VB6含量的测定。     

Theoretical study of the reaction of vitamin B6 with 1O2

Singlet oxygen is known to cause oxidative stress in cells, leading to severe damage (e.g., lipid peroxidation, membrane degradation, mutagenic alterations to DNA, protein misfunctionality). Recently, pyridoxine has been discovered to be capable of quenching singlet oxygen, however, the mechanism of this reaction remains essentially unknown. In this work, we have investigated four sets of reactions: 1) 1,3-addition to a double bond connected to a hydrogen-carrying group, resulting in the formation of allylic hydroperoxides; 2) [pi2+pi2] 1,2-cycloaddition to an isolated double bond, resulting in the formation of 1,2-peroxides; 3) 1,4-cycloaddition to a system containing at least two conjugated double bonds, resulting in the formation of the so-called 1,4-peroxides; 4) 1,4-addition to phenols and naphthols with the formation of hydroperoxide ketones. Thermodynamically, reaction 4 and the 6(9), 3(8), and 5(8) cases of reaction 1 are the most exergonic ones, with energies ranging from -16 to -18 kcal mol(-1). Furthermore, reaction 4 shows the lowest barrier through the reaction path, and is predicted to be the preferred mechanism for the pyridoxine + singlet-oxygen reaction, which is in agreement with previous experimental results.     

Exploiting ion-pair formation for the enhancement of electroanalytical determination of pyridoxine (B6) onto polyurethane-graphite electrodes

The present study reports some aspects of ion-pair formation between pyridoxine and dodecyl sulphate under suitable conditions of pH, and its application with analytical purposes. Electrochemical behavior of the analite onto a graphite-polyurethane electrode was assessed by both cyclic and square-wave voltammetries under different conditions (pH from 1.2 to 13.0, with and without surfactant), aiming to study its mechanisms and to define best parameters for such determination exploiting the association of electroanalytical variables and ion-pair formation; besides these, electrochemical impedance spectroscopy was also applied to evaluate ion-pair formation and its influence on interfacial fenomena. Best conditions were reach by square-wave voltammetry in pH 4.2 acetate buffer sweeping from + 0.7 to + 1.2 V (vs. Ag|AgCl_sat) in pulses of 50 mV amplitude and 10 mV step, in a frequency of 10 Hz. The concentration of sodium dodecyl sulphate was optimized being the optimal value a constant submicelar concentration of 3 mmol L^-1. Under such conditions a linear dynamic range from 2 to 18 μmol L^-1 was observed, providing faster, more selective and sensitive system. Interference studies were also carried out showing no relevant influence of thiamine, riboflavine and nicotinamide over the analysis of pyridoxine. The system was successfully applied to commercial parenteral samples containing thiamine and pyridoxine as purchased, without further treatment.     

Simultaneous Potentiometric Determination of Thiamine and Pyridoxine in Multivitamins Using a Single Cyclodextrin-Based Thiamine-Selective Electrode

Abstract

In this work, a PVC tubular ion-selective electrode without internal reference [composed of 6.35% (w/w) of β-cyclodextrin as ionophore, 1.59% (w/w) of potassium tetrakis (p-chlorophenyl) borate as lipophilic additive, and 63.5% (w/w) of 2-fluorophenyl-2-nitrophenyl ether as mediator solvent] was used to accomplish the simultaneous determination of thiamine and pyridoxine in multivitamin products. The electrode responds selectively to thiamine but presents high initial diffusion potential contribution from pyridoxine. This fact was exploited under flow conditions for the quantitative assessment of both species. A multitask flow system was optimized to dilute appropriately real samples and prepare in-line the set of calibrating solutions. The potentiometric signal was modeled by partial least squares regression, enabling the prediction of the content of each vitamin in the range of 1 × 10^?3 to 1 × 10^?4 mol L^?1. Absolute errors of prediction inferior to 0.06 × 10^?4 mol L^?1 and 0.16 × 10^?4 mol L^?1 for pyridoxine and thiamine respectively were obtained when compared with the chromatographic method.     

Synthesis and nonlinear optical properties of pyridoxine-based stilbazole derivatives and their azo-analogs

The syntheses of a series of novel derivatives of stilbazole and their azo-analogs bearing the phenylalkenyl and phenyldiazenyl substituents at position 6 of the pyridoxine ring are reported. The observed cis/trans regioselectivity in the Wittig reaction between triphenylbenzylphosphonium chloride and carbonyl derivatives of pyridoxine ketal is discussed with respect to transition state intermediates, nature of base used in the reaction, and resonance transformations in the pyridoxine system. The azo-derivatives are obtained by azocoupling of the diazonium salts of sulfanilic or 4-aminophenyl-1,3-disulfonic acids with the corresponding pyridoxine acetals. Nine compounds from the obtained experimental series are capable of emitting second harmonic generation light, although with a reduced efficiency as compared to well known KH₂PO₄ or LiIO₃ perovskite crystals, but with excellent beam resistance under laser irradiation, which makes them potential starting points for the development of novel nonlinear optical materials.