Vitamin B12 in Foods, Food Supplements, and Medicines-A Review of Its Role and Properties with a Focus on Its Stability

Vitamin B₁₂, also known as the anti-pernicious anemia factor, is an essential micronutrient totally dependent on dietary sources that is commonly integrated with food supplements. Four vitamin B₁₂ forms-cyanocobalamin, hydroxocobalamin, 5'-deoxyadenosylcobalamin, and methylcobalamin-are currently used for supplementation and, here, we provide an overview of their biochemical role, bioavailability, and efficacy in different dosage forms. Since the effective quantity of vitamin B₁₂ depends on the stability of the different forms, we further provide a review of their main reactivity and stability under exposure to various environmental factors (e.g., temperature, pH, light) and the presence of some typical interacting compounds (oxidants, reductants, and other water-soluble vitamins). Further, we explore how the manufacturing process and storage affect B₁₂ stability in foods, food supplements, and medicines and provide a summary of the data published to date on the content-related quality of vitamin B₁₂ products on the market. We also provide an overview of the approaches toward their stabilization, including minimization of the destabilizing factors, addition of proper stabilizers, or application of some (innovative) technological processes that could be implemented and contribute to the production of high-quality vitamin B₁₂ products.

Hydroxycobalamin catalyzes the oxidation of diethyldithiocarbamate and increases its cytotoxicity independently of copper ions

It is known that some metals (Cu, Zn, Cd, Au) markedly increase the toxic effect of thiocarbamates. It was shown in the present study that hydroxycobalamin (a form of vitamin B12, HOCbl), which incorporates cobalt, significantly enhances the cytotoxicity of diethyldithiocarbamate (DDC), decreasing its IC50 value in tumor cells three to five times. The addition of HOCbl to aqueous DDC solutions accelerated the reduction of oxygen. No hydrogen peroxide accumulation was observed in DDC + HOCbl solutions; however, catalase slowed down the oxygen reduction rate. Catalase as well as the antioxidants N-acetylcysteine (NAC) and glutathione (GSH) partially inhibited the cytotoxic effect of DDC + HOCbl, whereas ascorbate, pyruvate, and tiron, a scavenger of superoxide anion, had no cytoprotective effect. The administration of HOCbl into DDC solutions (> 1 mM) resulted in the formation of a crystalline precipitate, which was inhibited in the presence of GSH. The data of UV and NMR spectroscopy and HPLC and Mass Spectrometry (LC/MS) indicated that the main products of the reaction of DDC with HOCbl are disulfiram (DSF) and its oxidized forms, sulfones and sulfoxides. The increase in the cytotoxicity of DDC combined with HOCbl occurred both in the presence of Cu2+ in culture medium and in nominally Cu-free solutions, as well as in growth medium containing the copper chelator bathocuproine disulfonate (BCS). The results indicate that HOCbl accelerates the oxidation of DDC with the formation of DSF and its oxidized forms. Presumably, the main cause of the synergistic increase in the toxic effect of DDC + HOCbl is the formation of sulfones and sulfoxides of DSF.

Recovery of Elemental Tellurium Nanoparticles by the Reduction of Tellurium Oxyanions in a Methanogenic Microbial Consortium

This research focuses on the microbial recovery of elemental tellurium (Te(0)) from aqueous streams containing soluble tellurium oxyanions, tellurate (Te(VI)), and tellurite (Te(IV)). An anaerobic mixed microbial culture occurring in methanogenic granular sludge was able to biocatalyze the reduction of both Te oxyanions to produce Te(0) nanoparticles (NPs) in sulfur-free medium. Te(IV) reduction was seven times faster than that of Te(VI), such that Te(IV) did not accumulate to a great extent during Te(VI) reduction. Endogenous substrates in the granular sludge provided the electron equivalents required to reduce Te oxyanions; however, the reduction rates were modestly increased with an exogenous electron donor such as H2. The effect of four redox mediators (anthraquinone-2,6-disulfonate, hydroxocobalamin, riboflavin, and lawsone) was also tested. Riboflavin increased the rate of Te(IV) reduction eleven-fold and also enhanced the fraction Te recovered as extracellular Te(0) NPs from 21% to 64%. Lawsone increased the rate of Te(VI) reduction five-fold, and the fraction of Te recovered as extracellular material increased from 49% to 83%. The redox mediators and electron donors also impacted the morphologies and localization of Te(0) NPs, suggesting that NP production can be tailored for a particular application.

Reductive dechlorination of α-, β-, γ-, and δ-hexachlorocyclohexane isomers with hydroxocobalamin, in soil slurry systems

The present study was carried out to test the viability of a method of reductive dehalogenation of α-, β-, γ-, and δ-hexachlorocyclohexane (HCH) in soil slurry systems. The soil slurries were maintained under anaerobic conditions, with titanium(III) citrate as a reducing agent and hydroxocobalamin (vitamin B(12a)) as a catalyzing agent. Experiments were carried out with two soil samples with markedly different characteristics (particularly regarding organic matter content), at a small scale and larger reactor scale. HCH concentration was monitored throughout the 24 h duration of the tests. In the low organic matter soil HCH isomers degraded rapidly, in both the small scale and reactor systems, and undetectable levels (<0.5%) were reached within 5 h. However, complete degradation of HCH isomers was not achieved in soil with high organic matter content, and there were differences between the results obtained in the small scale and reactor systems. In the small scale system, the levels of degradation reached 93, 88, 94, and 91%, for α-, β-, γ-, and δ-HCH, respectively, and the nondegraded HCH was sorbed in the soil. In the reactor system, the reaction stopped after two hours (no more than 65% of any of the isomers was degraded).

Comparison of cobinamide to hydroxocobalamin in reversing cyanide physiologic effects in rabbits using diffuse optical spectroscopy monitoring

Our purpose is to compare cobinamide to hydroxocobalamin in reversing cyanide (CN)-induced physiologic effects in an animal model using diffuse optical spectroscopy (DOS). Cyanide poisoning is a major threat worldwide. Cobinamide is a novel molecule that can bind two molecules of cyanide, has a much higher binding affinity than hydroxocobalamin, and is more water soluble. We investigated the ability of equimolar doses of cobinamide and hydroxocobalamin to reverse the effects of cyanide exposure in an animal model monitored continuously by DOS. Cyanide toxicity was induced in 16 New Zealand white rabbits by intravenous infusion. Animals were divided into three groups: controls (n=5) received saline following cyanide, hydroxocobalamin (N=6) following cyanide, and cobinamide (N=5) following cyanide. Cobinamide caused significantly faster and more complete recovery of oxy- and deoxyhemoglobin concentrations in cyanide-exposed animals than hydroxocobalamin- or saline-treated animals, with a recovery time constant of 13.8+/-7.1 min compared to 75.4+/-25.1 and 76.4+/-42.7 min, for hydroxocobalamin- and saline-treated animals, respectively (p<0.0001). This study indicates that cobinamide more rapidly and completely reverses the physiologic effects of cyanide than equimolar doses of cobalamin at the dose used in this study, and CN effects and response can be followed noninvasively using DOS.

Ultrafast Excited-State Dynamics in Vitamin B12and Related Cob(III)alamins

Femtosecond transient IR and visible absorption spectroscopies have been employed to investigate the excited-state photophysics of vitamin B12 (cyanocobalamin, CNCbl) and the related cob(III)alamins, azidocobalamin (N3Cbl), and aquocobalamin (H2OCbl). Excitation of CNCbl, H2OCbl, or N3Cbl results in rapid formation of a short-lived excited state followed by ground-state recovery on time scales ranging from a few picoseconds to a few tens of picoseconds. The lifetime of the intermediate state is influenced by the sigma-donating ability of the axial ligand, decreasing in the order CNCbl > N3Cbl > H2OCbl, and by the polarity of the solvent, decreasing with increasing solvent polarity. The peak of the excited-state visible absorption spectrum is shifted to ca. 490 nm, and the shape of the spectrum is characteristic of weak axial ligands, similar to those observed for cob(II)alamin, base-off cobalamins, or cobinamides. Transient IR spectra of the upper CN and N3 ligands are red-shifted 20-30 cm(-1) from the ground-state frequencies, consistent with a weakened Co-upper ligand bond. These results suggest that the transient intermediate state can be attributed to a corrin ring pi to Co 3d(z2) ligand to metal charge transfer (LMCT) state. In this state bonds between the cobalt and the axial ligands are weakened and lengthened with respect to the corresponding ground states.

Electronic structure and bonding in hydroxocobalamin

The electronic structure of hydroxocobalamin (OHCbl) has been calculated by a density functional method, using the orthogonalized linear combination of the atomic orbitals method (OLCAO). The X-ray crystal structure has been determined from synchrotron X-ray diffraction data and the geometry determined was used in the calculations. Comparison with the recently reported electronic structures of cyanocobalamin (CNCbl), methylcobalamin (MeCbl) and adenosylcobalamin (AdoCbl) shows that Mulliken charges (Q*) and bond orders (BO) vary only on the axial fragment.

Determination of vitamin B12 using the enzyme glycerol dehydrase

Glycerol dehydrase is an enzyme that catalyzes dehydration of glycerol into beta-propionaldehyde. It requires 5'-deoxyadenosylcobalamin, one of the forms of vitamin B12, as a coenzyme. The enzyme is inactivated in vitro by all forms of vitamin B12 stoichiometrically. The objective of this study was to determine vitamin B12 content by utilizing the inactivation of the enzyme by vitamin B12. After various examinations, an excellent standard curve was obtained up to 1 pmol vitamin B12 using 14 mU of the enzyme per tube. Glycerol dehydrase does not respond to vitamin B12 if it is bound to haptocorrin, a vitamin B12-binding protein. This necessitates a procedure for extraction of vitamin B12 from samples before assay. The enzyme was less inactivated by 5'-deoxyadenosylcobalamin than any other form of vitamin B12. However, this did not matter because all forms of vitamin B12 were converted into cyanocobalamin during the extraction procedure cited above, which was performed in a buffer containing potassium cyanide.

Reductive dechlorination of alpha-, beta-, delta-, and gamma-hexachlorocyclohexane isomers by hydroxocobalamin in the presence of either dithiothreitol or titanium(III) citrate as reducing agents

The effect of the reducing potential on the reductive dehalogenation of the different HCH (hexachlorocyclohexane) isomers has not yet been studied. In the present study, the potential for dehalogenation of (alpha-, beta-, delta-, and gamma-HCH isomers by the dithiothreitol (DTT) and titanium(III) citrate (reducing potential at pH 7, -0.33 and -0.48 V, respectively), with and without the addition of hydroxocobalamin was investigated. In the presence of DTT without catalyst, there was no disappearance of any of the HCH isomers studied after 1 h of treatment. However, disappearance of the gamma- and alpha-HCH isomers was observed during the same time period when titanium(III) citrate was used as the reductant in the absence of catalyst (62.9 and 16.6% disappearance, respectively). Addition of the hydroxocobalamin to the DTT system favored mainly the disappearance of gamma- and alpha-HCH (92.9 and 30.8% disappearance after 1 h, respectively); disappearance of delta-HCH and beta-HCH was small (11.9%) or negligible, respectively. Addition of the hydroxocobalamin to the titanium(III) citrate system favored the degradation of all HCH isomers under study: beta- and alpha-HCH completely disappeared to undetectable levels (<0.1%) after 1 and 2 min, respectively; degradation of delta-HCH and beta-HCH was slower than that of the other two isomers, although they had almost completely disappeared (99.9 and 99.6% disappearance, respectively) after 10 and 60 min, respectively. The order of disappearance, gamma-HCH > alpha-HCH > delta-HCH > beta-HCH, coincided with a decreasing order of the axially positioned Cl atoms of these isomers (considering their thermodynamically most stable configuration). This study is the first description of the rapid degradation of delta- and beta-HCH under abiotic conditions, and the results demonstrate the effect of the reducing potential on the reductive dehalogenation of HCH isomers.

Mechanistic studies on the interaction of reduced cobalamin (vitamin B12r) with nitroprusside

The electron-transfer reaction between reduced cobalamin (Cbl(II)) and sodium pentacyanonitrosylferrate(II) (sodium nitroprusside, NP), as well as the subsequent processes following the electron-transfer step, were investigated by spectroscopic (UV-vis, (1)H NMR, EPR), electrochemical (CV, DPV) and kinetic (stopped-flow) techniques. In an effort to clarify the complex reaction pattern observed at physiological pH, systematic spectroscopic and kinetic studies were undertaken as a function of pH (1.8-9) and NP concentration (0.0001 - 0.09 M). The kinetics of the electron-transfer reaction was studied under pseudo-first-order conditions with respect to NP. The reaction occurs in two parallel paths of different order, viz. pseudo-first and pseudo-second order with respect to the NP concentration, respectively. The contribution of each path depends on pH and the [NP]/[Cbl(II)] ratio. At low pH and total NP concentration (pH < 3, [NP]/[Cbl(II)] approximately 1), the cyano-bridged successor complex [Cbl(III)-(mu-NC)-Fe(I)(CN)(3)(NO(+))](-) (1(s)()) is the final reaction product formed in an inner-sphere electron transfer reaction that is coupled to the release of cyanide from coordinated nitroprusside. At higher pH, subsequent reactions were observed which involve the attack of cyanide released in the electron transfer step on the initially formed cyano-bridged species, and lead to the formation of Cbl(III)CN and [Fe(I)(CN)(4)(NO(+))](2)(-). The strong dependence of the rate and mechanism of the subsequent reactions on pH is attributed to the large variation in the effective nucleophilicity of the cyanide ligand in the studied pH range. An alternative electron-transfer pathway observed in the presence of excess NP involves the reaction of the precursor complex [Cbl(II)-(mu-NC)-Fe(II)(CN)(4)(NO(+))](2)(-) (1(p)()) with NP to give [Cbl(III)-(mu-NC)-Fe(II)(CN)(4)(NO(+))](-) (2) and reduced nitroprusside, [Fe(CN)(5)NO](3)(-), as the initial reaction products. Analysis of the kinetic data allowed elucidation of the rate constants for the inner- and outer-sphere electron-transfer pathways. The main factors which influence the kinetics and thermodynamics of the observed electron-transfer steps are discussed on the basis of the spectroscopic, kinetic and electrochemical results. A general picture of the reaction pathways that occur on a short (s) and long (min to h) time scale as a function of pH and relative reactant concentrations is derived from the experimental data. In addition, the release of NO resulting from the one-electron reduction of NP by Cbl(II) was monitored with the use of a sensitive NO electrode. The results obtained in the present study are discussed in reference to the possible influence of cobalamin on the pharmacological action of nitroprusside.

Electrochemical and spectral studies of the reactions of aquocobalamin with nitric oxide and nitrite ion

Electrochemistry and Raman spectroscopy have shown that aquocob(III)alamin (Cbl(III)) can be reduced by nitric oxide (NO) to form Cbl(II) on an electrode surface. The Cbl(II) formed in this way can bind NO to form nitrosyl-cobalamin, Cbl(II)-NO, which is reduced to form Cbl(I) at about -1.0 V vs a KCl saturated Ag/AgCl reference electrode. In addition, nitrite was found to bind both Cbl(III) and Cbl(II) and a binding constant of 3.5 x 10(2) M(-1) was measured for (NO(2)-Cbl(II))(1-). UV-vis spectrophotometry and mass spectroscopy were used to show that Cbl(I) reduces NO to form Cbl(II)-NO and N(2)O and N(2), and this reaction is involved in the cyclic voltammetry of cobalamin in the presence of excess NO where a catalytic reduction of NO occurs involving the cycling of Cbl(II)-NO/Cbl(I). This redox couple is also involved in the electrochemical catalytic reduction of nitrite. These results can be used to explain a number of physiological effects involving NO interaction in biological systems with added cobalamin or with cobalamin in the methionine synthase enzyme.

[Interference of hydroxocobalamine treatment on commun biochemical determinations]

Hydroxocobalamin, antidote of the cyanide poisoning, is a red and water soluble pigment, which colors biological mediums. The interferences caused by this molecule are studied for plasma pools overloaded with hydroxocobalamin for concentrations from 0 to 1,125 mg.L-1. The results of 16 biochemical parameters on Vitros 750 XRC (Ortho-clinical Diagnostics) and of 23 biochemical parameters on Cobas Integra 700 (Roche Diagnostics) are examined. With this analytical system, unconjugated and conjugated bilirubin, creatinin, and CK results are changed as soon as plasma concentration of hydroxocobalamin reachs 124 mg.L-1. For the Vitros 750 XRC, ASAT, iron, creatinin, phosphorus are more sensitive to this interference. But, other results are changed for the two analytical systems for superior hydroxocobalamin concentrations.

Three-dimensional structure of ATP:corrinoid adenosyltransferase from Salmonella typhimurium in its free state, complexed with MgATP, or complexed with hydroxycobalamin and MgATP

In Salmonella typhimurium, formation of the cobalt-carbon bond in the biosynthetic pathway for adenosylcobalamin is catalyzed by the product of the cobA gene which encodes a protein of 196 amino acid residues. This enzyme is an ATP:co(I)rrinoid adenosyltransferase which transfers an adenosyl moiety from MgATP to a broad range of co(I)rrinoid substrates that are believed to include cobinamide, its precursor cobyric acid and probably others as yet unidentified, and hydroxocobalamin. Three X-ray structures of CobA are reported here: its substrate-free form, a complex of CobA with MgATP, and a ternary complex of CobA with MgATP and hydroxycobalamin to 2.1, 1.8, and 2.1 A resolution, respectively. These structures show that the enzyme is a homodimer. In the apo structure, the polypeptide chain extends from Arg(28) to Lys(181) and consists of an alpha/beta structure built from a six-stranded parallel beta-sheet with strand order 324516. The topology of this fold is very similar to that seen in RecA protein, helicase domain, F(1)ATPase, and adenosylcobinamide kinase/adenosylcobinamide guanylyltransferase where a P-loop is located at the end of the first strand. Strikingly, the nucleotide in the MgATP.CobA complex binds to the P-loop of CobA in the opposite orientation compared to all the other nucleotide hydrolases. That is, the gamma-phosphate binds at the location normally occupied by the alpha-phosphate. The unusual orientation of the nucleotide arises because this enzyme transfers an adenosyl group rather than the gamma-phosphate. In the ternary complex, the binding site for hydroxycobalamin is located in a shallow bowl-shaped depression at the C-terminal end of the beta-sheet of one subunit; however, the active site is capped by the N-terminal helix from the symmetry-related subunit that now extends from Gln(7) to Ala(24). The lower ligand of cobalamin is well-ordered and interacts mostly with the N-terminal helix of the symmetry-related subunit. Interestingly, there are few interactions between the protein and the polar side chains of the corrin ring which accounts for the broad specificity of this enzyme. The corrin ring is oriented such that the cobalt atom is located approximately 6.1 A from C5' of the ribose and is beyond the range of nucleophilic attack. This suggests that a conformational change occurs in the ternary complex when Co(III) is reduced to Co(I).

Picomolar quantitation of free sulfite in foods by means of [57Co]hydroxocobalamin and radiometric chromatography of [57Co]sulfitocobalamin. Method, applications and significance of coexisting sulfides

The concentration dependent reaction of sulfite with 57Co-labeled hydroxocobalamin (OH57CoCbl) to produce a sulfitocobalamin (SO(3)57CoCbl) adduct served as a quantification strategy for foodborne sulfite residues freely extracted into pH 5.2, 0.05 M acetate buffer. SO(3)57CoCbl was then resolved using SP-Sephadex C-25 gel chromatography and its radiometric detection allowed calculation of a standard logit plot from which unknown sulfite concentrations could be determined. The sulfite detection range was 6.0 nM-0.3 pM with respective relative standard deviations of 4.4-29.4% for 50-microl samples. Individual incidences of foodborne sulfite intolerances provoked by L-cysteine or sulfite additive use in bakery products, which remained undetected using conventional sulfite analytical methods, underscored the quantitative value of the method. The analytical significance and occurrences of detectable sulfides coexisting with foodborne sulfite residues was also addressed.

In situ X-ray absorption spectroelectrochemical study of hydroxocobalamin

An in situ X-ray absorption spectroscopy (XAS) spectroelectrochemical study of aquocobalamin (system B12a-B12r-B12s) has been carried out in aqueous solutions buffered at different pH values. To the best of our knowledge, this is the first structural study of aquocobalamin at room temperature under controlled oxidation conditions. Most of the previous work was in fact performed using frozen samples chemically treated to produce the species. The spectroelectrochemical approach offers several advantages: (1) the reduction products may be studied without poisoning the system with chemical reductive reagents and (2) any possible variation of the oxidation state owing to the electrons produced by the incident beam is avoided as the electrode, under potentiostatic control, acts as a scavenger. The spectroelectrochemical approach, together with more careful data analysis, has led to an improved interpretation of the XAS data. These conditions were not met in previous works where the oxidation state was not controlled and multiple scattering contributions were not taken into account. The general shape of the XAS spectra of the different species is not greatly affected by pH. A signature for the base-off square-planar coordination has been evidenced for the Co(II) compound at basic pH. A new signature for Co(I), indicating square-planar coordination, has been identified on the experimental spectra and simulated in theoretical X-ray absorption near-edge structure (XANES) studies. The flexibility of the electrochemical approach, that permits to unambiguously establish the formal oxidation state, has led to very reliable values for energy shift and peak intensity variations. The experimental XANES and extended X-ray absorption fine structure (EXAFS) spectra with a very good signal-to-noise ratio have been processed using the GNXAS package that takes into account multiple scattering contributions. EXAFS and XANES independent analysis result in the same structural model. The reduction from Co(III) to Co(II) produces the most significant structural changes: the cobalt coordination number decreases from six to five, and the edge position shifts by 2.4 +/- 0.3 eV. In addition, the XANES spectra are strongly modified. The reduction from Co(II) to Co(I) produces mainly electronic effects with no apparent change of the coordination number. A discussion of the limits and potentialities of EXAFS in this type of study has also been included.

Interactions between hydroxocobalamin and nitric oxide (NO): evidence for a redox reaction between NO and reduced cobalamin and reversible NO binding to oxidized cobalamin

Interactions of nitric oxide (NO) with various cobalamin species have been examined, apparently for the first time, with both absorption and electron paramagnetic resonance spectroscopy. Only slight shifts in the absorption spectrum of hydroxocobalamin, B12a [Cb(III)], were produced by NO, but dramatic changes in the spectrum of B12r [Cb(III)] were found on addition of NO. The addition of NO shifted the spectrum of Cb(II) to one very similar to that of Cb(III), indicating the oxidation of Cb(II). The addition of NO to Cb(III) resulted in a novel, weak and previously undescribed electron paramagnetic resonance signal. Although it has not been fully characterized, this appears to represent a reversible complex in which NO is liganded to the Cb(III). When NO was added to Cb(II), its strong electron paramagnetic resonance spectrum was replaced by that of this novel species, consistent with oxidation of Cb(II) by NO and then binding of additional NO by the resulting Cb(III). Porcine, aortic endothelial cells were able to partially reduce Cb(III), and release to the supernatant a previously characterized superoxide cobalt(III) complex, but some Cb(II) remained with the cell fraction. These reactions of Cb species could play a role in altering intracellular and intratissue levels of NO.