Different Forms Of Vitamin B6 Research Articles

Simultaneous determination of vitamin B6 and catechins in dietary supplements by ZIC-HILIC chromatography and their antioxidant interactions

Hydrophilic interaction liquid chromatography coupled to mass spectrometry was employed for simultaneous determination of vitamin B6 and catechins in dietary supplements. The obtained results clearly shows the potential of the application of alcohol eluent (instead mainly used acetonitrile) as a component of an with zwitterionic stationary phase. The limits of detection on ZIC-HILIC column were 0.01 mg/L for catechins and vitamins B (only for pyridoxal phosphate was 0.10 mg/L). The investigations between green tea extract (GTE) and vitamin B were also evaluated using isobolographic analysis as well as the interaction indexes. Antioxidant activities of single components and their mixtures were determined by DPPH assay. It was found that the mixtures of GTE and vitamin B acted synergistically. In comparison to GTE alone, faster DPPH radical bleaching of the mixtures was observed in the presence of different forms of vitamin B6 (pyridoxine, pyridoxal, or pyridoxal phosphate), particularly for pyridoxal.

The vitamin B6 paradox: Supplementation with high concentrations of pyridoxine leads to decreased vitamin B6 function

Vitamin B6 is a water-soluble vitamin that functions as a coenzyme in many reactions involved in amino acid, carbohydrates and lipid metabolism. Since 2014, >50 cases of sensory neuronal pain due to vitamin B6 supplementation were reported. Up to now, the mechanism of this toxicity is enigmatic and the contribution of the various B6 vitamers to this toxicity is largely unknown.In the present study, the neurotoxicity of the different forms of vitamin B6 is tested on SHSY5Y and CaCo-2 cells. Cells were exposed to pyridoxine, pyridoxamine, pyridoxal, pyridoxal-5-phosphate or pyridoxamine-5-phosphate for 24h, after which cell viability was measured using the MTT assay. The expression of Bax and caspase-8 was tested after the 24h exposure. The effect of the vitamers on two pyridoxal-5-phosphate dependent enzymes was also tested.Pyridoxine induced cell death in a concentration-dependent way in SHSY5Y cells. The other vitamers did not affect cell viability. Pyridoxine significantly increased the expression of Bax and caspase-8. Moreover, both pyridoxal-5-phosphate dependent enzymes were inhibited by pyridoxine.In conclusion, the present study indicates that the neuropathy observed after taking a relatively high dose of vitamin B6 supplements is due to pyridoxine. The inactive form pyridoxine competitively inhibits the active pyridoxal-5′-phosphate. Consequently, symptoms of vitamin B6 supplementation are similar to those of vitamin B6 deficiency.

Pyridoxamine is a substrate of the energy-coupling factor transporter HmpT

Energy-coupling factor (ECF) transporters belong to a novel family of proteins that forms a subset within the ATP-binding cassette (ABC) transporter family. These proteins are responsible for the uptake of micronutrients in bacteria. ECF transporters are composed of four proteins: the A- and A′-components, the T-component and the S-component. One of the ECF transporters, named HmpT, was crystallized in the apo form with all four components. It is currently unknown whether HmpT serves as a transporter for hydroxymethyl pyrimidine or the different forms of vitamin B6 (pyridoxine, pyridoxal or pyridoxamine). Using a combination of molecular dynamics (MD) simulations and mass spectrometry, we have identified pyridoxamine to be the preferred substrate of HmpT. Mass spectra show that the mass of the substrate from the HmpT–substrate complex matches that of pyridoxamine. MD simulations likewise indicate that pyridoxamine interacts most strongly with most of the conserved residues of the S-component (Glu 41, His 84 and Gln 43) compared with the other vitamin B6 forms. Furthermore, the simulations have implied that loops 1 and 5 of the S-component can participate in the gating action for HmpT.

Characterization of enzymes involved in the interconversions of different forms of vitamin B6 in tobacco leaves

There are six different vitamin B(6) (VB(6)) forms, pyridoxal (PL), pyridoxamine (PM), pyridoxine (PN), pyridoxal 5'-phosphate (PLP), pyridoxamine 5'-phosphate (PMP) and pyridoxine 5'-phosphate (PNP). PLP is a coenzyme required by more than 100 cellular enzymes. In spite of the importance of this vitamin, the understanding of VB(6) metabolic conversion in plants is limited. In this study, we developed a sensitive and reliable method to assay VB(6)-metabolizing enzyme activities by monitoring their products visually using high-performance liquid chromatography. With this method, the reactions catalyzed by PL/PM/PN kinase, PMP/PNP oxidase, PM-pyruvate aminotransferase, PL reductase and PLP phosphatase were all nicely detected using crude protein extracts of tobacco leaves. Under optimal invitro conditions, specific activities of those enzymes were 0.15±0.03, 0.10±0.03, 0.08±0.02, 0.64±0.13 and 23.08±1.98nmol product/min/mg protein, respectively. This is the first report on the conversion between PM and PL catalyzed by PM-pyruvate aminotransferase in plants. Furthermore, the PL reductase activity was found to be heat inducible. Our study sheds light on the VB(6) metabolism taking place in plants.

Spectroscopic studies on the inclusion interaction of p-sulfonatocalix[6]arene with vitamin B6

The formation of the inclusion complex of p-sulfonatocalix[6]arene (SCX6) with different forms of vitamin B6 (VB6) was studied by using fluorescence spectroscopy. VB6 can exist in one of three forms (the acidic form, neutral zwitterionic form and basic form) depending on pH. The fluorescence intensities of acidic and basic forms of VB6 remarkably decreased in presence of SCX6. SCX6 preferred to form 1:1 inclusion complexes with acidic and basic forms of VB6 but hardly form inclusion complex with neutral zwitterionic form. According to the nonlinear curve fitting method, the inclusion constant (K) for the formation of inclusion complexes of acidic and basic forms of VB6 with SCX6 were evaluated to be 1.4 × 104 and 9 × 103 L/mol, respectively. The binding affinity of SCX6 towards acidic form is attributed to hydrogen bonds and hydrophobic interaction, furthermore, additional electrostatic interaction also plays a crucial role. The possible inclusion mode was given by 1H NMR technique.

EFFECT OF BLANCHING, EDTA AND NaHSO3 ON COLOR AND VITAMIN B6 RETENTION IN CANNED GARBANZO BEANS

ABSTRACTTHE EFFECT of blanching, EDTA and NaHSO3 treatments on color and vitamin B6 retention in canned garbanzo beans (Cicer arietinum) was investigated. Saccharomyces carlsbergensis (ATCC 9080) and Kloeckera apiculata (UCD FS & T 72–62) were used as comparative organisms for the microbiological assay. Water blanching resulted in approximately 10–15% loss of total vitamin B6 while steam blanching resulted in only 5–8% loss. The dry garbanzo beans contained 5.5 μg vitamin B6/g when S. carlsbergensis was used as the test organism and 5.8 μg/g when K. apiculata was used. Blanching had no significant effect on the color of the canned beans. Vitamin B6 retention in the canned product was affected by the use of NaHSO3 in the soaking water as a bleaching agent. Samples soaked in water containing 1600 ppm NaHSO3 contained 3.4 ± 0.1 μg vitamin B6/g on the dry basis while the control samples contained 3.9 ± 0.2 μg/g. The NaHSO3 soaking improved the color of the canned beans significantly. Incorporating 300 ppm of ethylenediaminetetraacetic acid (EDTA) in the canning brine for color improvement did not significantly affect the vitamin B6 content of the canned product. But, it did improve the color of the canned beans. Use of K. apiculata as the test organism resulted in slightly but consistently higher total vitamin B6 assays in all samples than those using S. carlsbergensis. This could be due to the difference in the response of the two organisms toward the different forms of vitamin B6. K. apiculata responds nearly equally to pyridoxine, pyridoxal and pyridoxamine, while S. carlsbergensis responds nearly the same to pyridoxine and pyridoxal, but to a lesser degree to pyridoxamine.

Metabolic Interconversions of Different Forms of Vitamin B6

Tritium-labeled pyridoxamine, pyridoxal 5′-phosphate, and pyridoxine 5′-phosphate were prepared and administered intravenously to mice, and the distribution of isotope in liver and carcass between pyridoxine, pyridoxine 5′-phosphate, pyridoxal, pyridoxal 5′-phosphate, pyridoxamine and pyridoxamine 5′-phosphate was determined at different times after administration. The vitamin B6 forms were extracted from the tissues by perchloric acid and separated by ion exchange chromatography. The results strongly suggest that phosphorylation is the first step in the conversion of pyridoxamine as well as of pyridoxine to the active coenzyme form of the vitamin. After an initial period of equilibration, pyridoxal 5′-phosphate and pyridoxamine 5′-phosphate accounted for more than 90% of recovered isotope in liver and for 80 to 90% of recovered isotope in carcass. The ratio between these compounds was about 2:1 in both liver and carcass. About 10% of the total isotope in carcass appeared as pyridoxal. The available experimental data obtained after administration of different forms of vitamin B6 were found to fit a kinetic metabolic model which assumes an equilibration between pyridoxal 5′-phosphate and pyridoxamine 5′-phosphate but essentially unidirectional reactions in other metabolic conversions.

Metabolism of tritium- and 14C-labeled pyridoxine in the rat.

Studies on the metabolism of different forms of vitamin B6 in vivo require the use of labeled compounds with high specific radioactivity. Tritium-labeled pyridoxine has therefore been used in several studies. Since tritium is lost in the metabolic conversion of pyridoxine, we have now determined the distribution of tritium in [3H8] pyridoxine prepared by exposure of pyridoxine to tritium gas and compared the metabolism of [3H8] pyridoxine in rats with that of [4,5 – 14C2] pyridoxine. Oxidation of [3H8, 4, 5 – 14C2] pyridoxine with potassium permanganate to 4-pyridoxic acid and to 5-hydroxy-6-methylcinchomeronic acid showed that 22% of the tritium was located in the 4-hydroxymethyl group and 21% in the 5-hydroxymethyl group. The isotope-retention curves of tritium and carbon 14 after administration of [3H8, 4, 5 – 14C2]pyridoxine to rats had approximately the same kinetic parameters, indicating that [3H8] pyridoxine may be used to calculate fractional turnover rates of vitamin B6. Two methods for the calcu...

‘Mass spectrometry of vitamin B6: Different forms of the vitamin, its metabolites, antimetabolites, and analogs’

AbstractThe mass spectra of the different forms of vitamin B6, some metabolites and antimetabolites, and some analogs are reported. The free bases are suitable for study, but the 5‐phosphates are not sufficiently volatile. The hydrochloride salts dissociate thermally in the inlet system into the free base and HCl and give the spectrum of the free base with the spectrum of HCL superimposed on it. The compounds studied are: pyridoxol, pyridoxamine and pyridoxal, which are different forms of vitamin B6; 4‐pyridoxic acid and its lactone, 5‐pyridoxic acid lactone, isopyridoxal, 5‐formyl‐3‐hydroxy‐2‐methylpyridine‐4‐carboxylic acid, and 3‐hydroxy‐2‐methylpyridine‐4,5‐dicarboxylic acid, which are vitamin B6 metabolites; α4‐and α5‐deoxypyridoxol, 3‐deoxypyridoxol, and 4‐ and 5‐ norpyridoxol, which are antimetabolites and analogs of vitamin B6.

Availability of Amino Acids to Microorganisms: IV. Comparison of Hydrolysates of Lactalbumin, Oatmeal and Peanut Butter with Simulated Amino Acid Mixtures by Growth Response of Microorganisms

A method described previously was used to compare hydrolysates of oatmeal, peanut butter and lactalbumin with their simulated mixtures of amino acids. Different growth responses of Leuconostoc mesenteroides P-60 were obtained with the hydrolysates of oatmeal and peanut butter and their simulated amino acid counterparts. The same growth responses were obtained with a hydrolysate of lactalbumin, a pure protein, and its amino acid counterpart. These results indicated that the oatmeal and peanut butter hydrolysates contained growth factors other than amino acids. To obtain equal growth with an amino acid mixture and an oatmeal hydrolysate, additional pyridoxal or pyridoxamine was required; to obtain equal growth with an amino acid mixture and a peanut butter hydrolysate, additional niacin was required. The effect of different forms of vitamin B6 and niacin on growth response at constant nitrogen levels and the difficulty of evaluating amino acid patterns by the growth response of L. mesenteroides P-60 are discussed.