Thermal degradation of B-group vitamins: B1, B2 and B6

The thermal behaviour of vitamins B₁, B₂ and B₆ under non-isothermal conditions and dynamic air atmosphere was studied. According to our study, it was determined that the most stable compound is vitamin B₂. A kinetic analysis of the thermodegradation process using four different data processing methods (Friedman, Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose and modified NPK) was performed. The NPK was the only method that made it possible to evaluate the contribution to the reaction rate of the temperature and conversion, respectively. The results obtained from kinetic analysis were corroborated with the molecular architecture of the studied compounds.     

2'-hydroxypyridoxol, a biosynthetic precursor of vitamins B(6) and B(1) in yeast

In separate experiments cultures of the yeast Saccharomyces cerevisiae ATTC 7752 were grown in the presence of [5',5'-2H2]- or of [2',2',5',5'-2H4]-3-hydroxy-2,4,5-tri(hydroxymethyl)pyridine (i.e., 2'-hydroxypyridoxol). The 2H NMR spectra of the samples of pyridoxamine dihydrochloride and of thiamin chloride hydrochloride that were isolated from the two experiments showed the presence of deuterium at the corresponding sites. Entry of deuterium from the specifically 2H-labeled samples of 2'-hydroxypyridoxol into the predicted sites of pyridoxamine and of the pyrimidine unit of thiamin provides the first unequivocal evidence that, in yeast, 2'-hydroxypyridoxol is an intermediate on the route from a C5-sugar into vitamin B6, and adds to the evidence that pyridoxol serves as a precursor of the pyrimidine unit of thiamin, supplying the C5N unit, C-2',2,N-1,C-6,5,5' as an intact unit.     

Functionalization of polyesters with multiple B vitamins

A method to covalently attach combinations of six different B vitamins provided an avenue to new functional thermosets without multi‐step coupling reactions. The melt polymerization strategy required no organic solvent and facilitated covalent attachment of OH (B₁, B₂, B₅, B₆) or COOH (B₇, B₉) groups on B vitamins via Fischer esterification. Characterization of model reactions with LC/MS, FTIR, and GPC confirmed covalent attachment. Based on control experiments, B vitamins demonstrated unexpected thermal stability and appreciable solubility in the melt polymerization. This approach was demonstrated with citric acid and diglycerol, but has wide‐ranging potential for other polar monomers with negative octanol–water partition coefficients (LogP). © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3308–3316     

反相高效液相色谱法分离测定复合维生素片剂中VB1,VB2,VB6和烟酰胺

采用NovaPak C18色谱柱(30 cm×3.9 mm,粒径10 μm),以(V(水)V(甲醇)V(冰乙酸)m(庚烷磺酸钠)=730 mL270 mL5 mL400 mg)为流动相,检测波长为280 nm,分离测定了复合维生素片剂中的VB1,VB2,VB6和烟酰胺,实验回收率分别为100.5%,96.8%,98.1%,102.0%,相对标准偏差RSD分别为0.8%,0.4%,0.5%,1.2%(n=5),检出限分别为39,4.2,4.7,10 ng.本法已用于复合维生素片剂中VB1,VB2,VB6和烟酰胺的分离和测定.     

Acrylonitrile-butadiene-styrene (ABS) composite electrode for the simultaneous determination of vitamins B2 and B6 in pharmaceutical samples

Journal of Solid State Electrochemistry - A lab-made affordable composite electrode based on acrylonitrile-butadiene-styrene (ABS) and graphite was developed and applied for the simultaneous...     

Electrochemical methods for determining group B vitamins

Electrochemical methods for the determination of group B vitamins reported in the last 25 years and the most important chemical and analytical parameters of potentiometry and voltammetry methods for these vitamins in pharmaceutical items, foods, and biological objects are reviewed. Sensor systems, first of all biosensors, seem to be the most efficient; further progress should be anticipated in this area. Possibility of the automation of analysis by coupling of sensors with flow-injection analysis also offers promise.     

Carbamoylation Applied for Structure Determination of Cellulose Derivatives

Carbamoylation of cellulose esters (CE) and investigation of the mixed derivatives obtained with NMR spectroscopy represents a useful analytical tool for the determination of the degree of substitution (DS) and analysis of the distribution of substituents on the level of the anhydroglucose unit (AGU). Especially the carbethoxymethylcarbamoylation and the ethylcarbamoylation of CE combined with ¹H NMR spectroscopy are efficient and inexpensive ways to gain information on the over-all DS and partial DS values in position 2, 3, and 6 of the AGU. Complete subsequent phenylcarbamoylation can be achieved even for CE with bulky substituents, e.g., adamantanecarboxylic acid esters. In addition to NMR experiments the carbamoylated CE were studied by HPLC after complete chain degradation. Carbethoxymethylcarbamoylation has turned out to be the most useful tool for this path. Chromatograms comparable to carboxymethylated cellulose (CMC) were obtained, which can be exploited to calculate the mole fractions of the basic building units (un-, mono-, di- and tri-substituted glucoses) of the polymer. Comparison with statistic calculations gave a first hint on the distribution of substituents along the polymer chain. For a commercial cellulose diacetate a statistic pattern of substitution was determined.     

高精度定量毛细管电泳法同时测定复合维生素B片中B1、B2、B6、烟酰胺及泛酸钙

建立了高精度定量毛细管电泳法同时测定复合维生素B片中维生素B₁、B₂、B₆、烟酰胺和泛酸钙的方法。样品经乙腈-水（20∶80，v/v）超声提取后，采用全自动高精度定量毛细管电泳仪，以高精度进样阀定量进样，以40 mmol/L硼砂-硼酸缓冲液（pH 9.0）为背景电解质溶液，以工作电压为-10 kV电泳分离。维生素B₁、B₂、B₆、烟酰胺的检测波长为280 nm，然后切换至检测波长210 nm检测泛酸钙。结果表明，各组分之间均得到良好分离，峰面积日内重复性（RSD）为1.3%~1.9%，显著优于普通毛细管电泳。维生素B₁、B₂、B₆、烟酰胺及泛酸钙的浓度在各自线性范围内的相关系数（r）为0.9968~0.9998，检出限2.5~36.0 mg/L，平均回收率为94.1%~98.9%。该法准确可靠，可用于实际复合维生素B片中维生素B₁、B₂、B₆、烟酰胺和泛酸钙含量的同时测定。     

Liquid-liquid distribution of B group vitamins in polyethylene glycol-based systems

General regularities of the liquid-liquid distribution of B₁, B₂, B₆, and B₁₂ vitamins in aqueous polyethylene glycol (PEG-2000, PEG-5000) solution-aqueous salt solution systems are studied. The influence of the salting-out agent, the concentration of the polymer, and its molecular weight on the distribution coefficients and recovery factors of the vitamins are considered. Equations relating the distribution coefficients (log D) to the polymer concentration are derived.     

A 13C n.m.r. study of the B6 vitamins and of their aldimine derivatives

The vitamins, pyridoxine, pyridoxal, pyridoxamine, pyridoxal-5′-phosphate and pyridoxamine-5′-phosphate, have been studied in aqueous solution over a pH range of 2–12 by ¹³C nuclear magnetic resonance spectroscopy. Resonance assignments are made primarily by the spin–spin coupling constants of carbons with protons and with phosphorus. The proton–carbon coupling constants show a marked conformational dependence in the hemiacetal form of pyridoxal. Furthermore, the H-6? C-5 coupling constant in the vitamins is much smaller than the corresponding constant in pyridine. This may be due either to an effect of the C-5 substituent in vitamins or to a different electronic configuration of the zwitterionic hydroxypyridine ring. The addition of manganese to a solution of pyridoxal phosphate causes line broadenings consistent with the interaction of the metal ion with this vitamin at the formyl and phenolic oxygens. The chemical shifts of the aromatic carbons of pyridoxine have been calculated, as a function of pH, by summing shielding parameters which were estimated empirically from pyridine derivatives. The calculated shifts agree well with the experimental data for C-3, C-5 and C-6, less well for C-2, and poorly for C-4. The deviation from additivity for C-4 indicates a preferred orientation for the 4-hydroxymethyl substituent caused by internal hydrogen bonding between the substituents at C-3 and C-4. Evidence is presented for the existence of the free aldehyde form of pyridoxal at alkaline pH. Aldimine complexes of pyridoxal and pyridoxal phosphate with amines and amino acids have also been studied. Characteristic chemical shift changes caused by both pyridinium and aldimine nitrogen deprotonations are seen. Additionally, the chemical shifts of carbons of the pyridine ring are dependent upon the structure of the imine, especially when the aldimine nitrogen is protonated. We conclude that this dependency is due to steric effects in an aldimine complex which is constrained by internal hydrogen bonding. We also discuss the merits of carbons 3 and 4 as possible sites of cofactor labeling for enzymatic studies.     

Effects of B vitamins on the radiation-induced transformations of hydroxyl-containing organic compounds

In this work, the interaction of B vitamins with α-hydroxyl-containing carbon-centered radicals formed upon the irradiation of deaerated aqueous solutions of ethanol, ethylene glycol, α-methylglycoside, maltose, and α-glycerophosphate at pH 7 was studied by means of continuous radiolysis. Within the framework of the density functional theory, the homolytic bond dissociation enthalpies (BDEs) of -C-H, -O-H, and -N-H bonds and H-atom addition enthalpies (HAEs) at the -C=O and -C=N groups of the test compounds were calculated. The set of the experimental and theoretically calculated data suggests that vitamin B₂, nicotinamide and pyridoxal phosphate effectively oxidize α-hydroxyl-containing carbon-centered radicals, whereas vitamins B₁ and B₆ reduce these radicals to prevent their recombination and fragmentation reactions.     

Regularities in the extraction of B group vitamins with synthetic water-soluble polymers

Common regularities in the extraction of vitamins B₁, B₂, B₆, and B₁₂ from aqueous solutions of polymers (poly-N-vinylpyrrolidone, poly-N-vinylcaprolactam, and polyacrylamide) are studied. The effect of the polymer’s concentration and its structure on the distribution coefficients and the degree of extraction of the vitamins is established. Effective systems for extracting B group vitamins from water-salt solutions are developed as a result of screening stable two-phase systems based on water-soluble polymers.     

Roles of vitamins B5, B8, B9, B12 and molybdenum cofactor at cellular and organismal levels

Many efforts have been made in recent decades to understand how coenzymes, including vitamins, are synthesised in organisms. In the present review, we describe the most recent findings about the biological roles of five coenzymes: folate (vitamin B9), pantothenate (vitamin B5), cobalamin (vitamin B12), biotin (vitamin B8) and molybdenum cofactor (Moco). In the first part, we will emphasise their biological functions, including the specific roles found in some organisms. In the second part we will present some nutritional aspects and potential strategies to enhance the cofactor contents in organisms of interest.     

Acylation and Carbamoylation of 2-Hydrazinothiazole Derivatives. Identification of Isomeric Structures

Acylation and carbamoylation of 2-(arylmethylidenehydrazino)- and 2-(aroylhydrazino)thiazoles was performed, and structure of the products was established.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 4, 2005, pp. 594–600.Original Russian Text Copyright © 2005 by Denisova, Bakulev, Dehaen, Toppet, Van Meervelt, Kodess.     

Flow-injection determination of water-soluble vitamins B1, B2, and B6 from the electrocatalytic response of a graphite electrode modified with a ruthenium(III) hexacyanoruthenate(II) film

The electrochemical behavior of water-soluble vitamins B₁, B₂, and B₆ at an unmodified graphite electrode and a graphite electrode modified with an inorganic film of ruthenium(III) hexacyanoruthenate(II) was studied. The electrocatalytic activity of the metal complex in the oxidation of vitamins was found. Ru(IV) species act as a catalyst. Conditions for recording voltammograms and hydrodynamic conditions for detecting the maximum catalytic current in flow-injection analysis (FIA) were selected. Procedures for the amperometric detection of thiamine, riboflavin, and pyridoxine were proposed.     

Hydroxymethylation and Carbamoylation of Di-And Tetramethylpyridines Using Radical Substitution (Minisci) Reactions

Reaction of hydroxymethyl radicals with N-methoxy 2,4- and 2,6-dimethylpyridinium salts gave 2,4,6-substituted hydroxymethylpyridines. Similar reactions with 2,3,5,6-tetramethylpyridine and derivatives failed, however 4-substitution could be achieved using a carbamoyl radical.