Of cyanocobalamin

The lUPAC-IUB Commission on Biochemical Nomenclature (13) recommends that the term vitamin B 2 be used as the genetic descriptor for aU. cottiaoids exhibiting quaUtatively the biological activity of cyanocobalamin. However, because of its commercial importance, cyaaocobalamin is used iaterchangeably with vitamin B 2 heteia. 

FIGURE 18.28 The structure of cyanocobalamin (top) and simplified structures showing several coenzyme forms of vitamin Bi2- The Co—C bond of 5 -deoxyadenosylcobalamin is predominantly covalent (note the short bond length of 0.205 nm) but with some ionic character. Note that the convention of writing the cobalt atom as Co" " attributes the electrons of the Co—C and Co—N bonds to carbon and nitrogen, respectively. 

Cobalt is present in animals in vitamin B12 (cyanocobalamine) and thus is essential for humans (Thunus and Lejeune 1994). The determination of Co has little significance for the diagnosis of deficiency of cyanocobalamine. Instead, cyanocobalamine itself must be determined in serum. The determination of methyl malonic acid in urine seems more reliable (McCann et al. 1996). 

The reduction of cyanocobalamin gives three possible oxidation states for the cobalt atom (Fig. 2). Electron spin resonance studies with Bi2-r reveals that this molecule is the only paramagnetic species giving a spectrum expected for a tetragonal low spin Co(II) complex. Controlled potential reduction of cyanocobalamin to Bi2-r proves that this reduction involves one electron, and further reduction of Bi2-r to B12-S requires a second single electron (16—19). At one time B12-S was considered to be a hydride of Co(III), but controlled potential coulometry experiments provided evidence against a stable hydride species (16). However, these experimental data do not exclude the possibility of a stable Co(III) hydride as the functional species in enzyme catalyzed oxidation reduction reactions. 

The usual oral dose of cyanocobalamin Co 60 capsules is equivalent of 0.5 to 1 pX i. Express this dose range in terms of megabecquerels. 

What is the best evidence cited that the anemia is due to a primary deficiency of cyanocobalamin (Bjj) ... 

Optimal therapy consists in parenteral administration of cyanocobalamin or hydroxycobalamin (Vitamin Lullmann, Color Atlas of Pharmacology... 

Cyanocobalamin and the derivative hydroxo-cobalamin, given IM or deep subcutaneously, are indicated for treating vitamin B12 deficiency. Only in strict vegetarians oral preparations may be effective. Oral preparations with added intrinsic factor mostly are not reliably in patients with pernicious anemia. More than half the dose of cyanocobalamin injected is excreted in the urine within 48 hours and the therapeutic advantages of doses higher than 100 pg are questionable because of this rapid eiimination. As... 

Cyanocobalamin, the form of vitamin B12 isolated initially, contains cyanide attached to cobalt. It occurs only in minor amounts, if at all, in nature but is generated through the addition of cyanide during the isolation. Hydroxocobalamin (vitamin B12a) containing OH in place of CN"does occur in nature. However, the predominant forms of the vitamin are the coenzymes in which an alkyl group replaces the CN of cyanocobalamin. 

CC Jansen, JP de Kleijn. The assay of cyanocobalamin in pharmaceutical preparations by solid-phase extraction and HPLC. J Chromatogr Sci 28 42-45, 1990. 

In pernicious anemia, vitamin B12 should be given as intramuscular injection or high-dose oral supplements. Intramuscular injections of 100 to 1000 pg of cyanocobalamin for 5 d and 100 to 1000 pg of cyanocobalamin each month thereafter is a sufficient protocol for treating pernicious anemia (see Baik and Russell, 1999). 

N of hydrochloric acid. In this elution, 8 ml of colored eluate was collected. This portion of the eluate was found to contain 295 ig of cyanocobalamin and 9 mg of total solids. 

H. Iwase, Ultramicro determination of cyanocobalamin in elemented diet by solid-phase extraction and HPLC with visible detection, J. Chromatogr., 590 359 (1992). 

The vitamin is stable in aqueous solution at room temperature. It may be heated to 120°C with little loss of activity provided the pH is kept between 4 and 6. However, it breaks down rapidly when exposed to a pH below 2 or above 9. Crystals of cyanocobalamin are dark red, needle-like, and contain about 12% water. 

Succinyl and 5 -0-succinyl derivatives of cyanocobalamin were not inhibitory for diol dehydrase even when enzyme was prein-... 

The authors are grateful to Merck and Co., Inc., Rahway, NJ, for a generous gift of cyanocobalamin. 

Moore FH, O Connor BH, Willis BTM, Hodgkin DC (1984) X-ray and neutron diffraction studies of the crystal and molecular structure of the predominant monocarboxylic acid obtained by mild acid hydrolysis of cyanocobalamin. Part III. Neutron diffraction studies of wet crystals. Proc Ind Acad Soc (Chem Sci) 93 235-260... 

Garcfa-Arieta, A., Torrado-Santiago, S., Goya, L., and Torrado, J. J. (2001), Spray-dried powders as nasal absorption enhancers of cyanocobalamin, Biol. Pharm. Bull., 24, 1411-1416. 

Although cyanocobalamin was the first form in which vitamin B12 was isolated, it is not an important naturally occurring vitamer, but rather an artifact caused by the presence of cyanide in the charcoal used in the extraction procedure. It is more stable to light than the other vitamers, and is commonly used in pharmaceutical preparations. Photolysis of cyanocobalamin in solution leads to the formation of aquocobalamin or hydroxocobalamin, depending on pH. 

Small amounts of cyanocobalamin are found in the bloodstream (about 2% of total plasma vitamin B12) apparendy as part of the metabolism of cyanide derived from food (and tobacco smoke), but not in erythrocytes or tissues. If it is not converted to aquo- or hydroxocobalamin, cyanocobalamin may have antivitamin action and has been implicated in the neurological damage associated with chronic cyanide intoxication seen in parts ofwest Africa, where the dietary staple, cassava, is rich in cyanogenic glycosides. 

Vitamin B]2, cyanocobalamin, is essential for human nutrition. It is concentrated in animal tissue but not in higher plants. Although nutritional requirements for the vitamin are quite low, people who abstain completely from animal products may develop a deficiency anemia. Cyanocobalamin is the form used in vitamin supplements. It contains 4.34% cobalt by mass. Calculate the molar mass of cyanocobalamin, assuming that there is one atom of cobalt in every molecule of cyanocobalamin. 

Deficiency of cyanocobalamin, or vitamin B12, can result in reduced visual acuity secondary to optic nerve dysfunction. Causes range from malabsorption to alcohol abuse.Treatment is with oral (1,000 to 2,000 meg daily)... 

First figure refers to the dry, the second to the wet form of cyanocobalamin. 

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