Cyanocobalamin stability

The name vitamin B12 indicates a group of cobalt-containing corrinoids, also described as cobala-mins. Hydroxycobalamin (HOCbl), adenosylcobalamin (AdoCbl), and methylcobalamin (MeCbl) are the natural occurring forms. Instead, cyanocobalamin (Figure 19.20) is the commercially available form used for supplements and food fortification, thanks to its greater relative stability. Occasionally, sulfitocobalmin can occur in processed foods. Vitamin B,2 functions as a coenzyme and it is linked to human growth, cell development, and is involved in metabolism of certain amino acids. Vitamin B12 is present mainly in meat and diary foods, therefore a deficiency can occur in... 

The Bj2 vitamers consist of a group of organometallic compounds that have a common cor-rinoid structure and vary in the substituent bound to the central cobalt atom (Fig. 7) (167,168). The principal naturally occurring Bl2 vitamers are hydroxocobalamin (HOCbl), methylcobal-amin (MeCbl), and adenosylcobalamin (AdoCbl). Cyanocobalamin (CNCbl) is the form commonly used for clinical, pharmaceutical, and food fortification purposes, due to its greater relative stability. 

Many vitamins are quite stable under normal processing conditions and present little or no stability problems in finished pharmaceutical products. These include biotin, niacin, niacinamide, pyridoxine, riboflavin, and a-tocopheryl acetate. Others that can present problems are ascorbic acid, calciferol, calcium pantothenate, cyanocobalamin, fola-cin, and retinyl esters. Overages above label claim are customarily added to vitamin formulations as a means of maintaining the claimed level of each vitamin for the expected shelf life of the products. The percent overage for a particular vitamin such as L-ascorbic acid will vary... 

Further active substances, in addition to cyanocobalamin, that can be stabilized povidone, are shown in Table 112. 

Vitamin Bu in solution (in concentrations of 20 iig. per milliliter or greater), if suitably stabilized and stored in a cool place in the dark, shows no detectable deterioration after six months. On the other hand, concentrates containing vitamin B12, such as liver extract, deteriorate considerably with time. Some preparations of Bu contain a mixture of cyanocobalamin and hydroxocobalamin (Baxter et al., 1953), but since the latter is hemopoietically active, this is probably not serious. Other observations on the stability of vitamin Bu are reviewed by E. L. Smith (1954). 

Cyanocobalamin (Formula 6.17) was isolated in 1948 from Lactobacillus lactis. Due to its stability and availability, it is the form in which the vitamin is used most often. In fact, cyanocobalamin is formed as an artifact in the processing of biological materials. Cobalamins occur naturally as adenosylcobalamin and methylcobalamin, which instead of the cyano group contain a 5 -deoxyadenosyl residue and a methyl group respectively. 

Owing to the desirability of converting the more labile forms of vitamin Bi2 to cyanocobalamin by cyanide treatment, it has been common to extract Bi2 from crude materials with KCN solutions. Skeggs, Driscoll, Chamey, and Wright (39) found the most effective treatment with cyanide to be extraction with 0.01% KCN (10 mg. of KCN for 10 y.g. of vitamin B12 activity) at 60 C. for 30 minutes. Higher temperatures are necessary to release bound forms of vitamin B12. Vitamin Bu has a maximum of stability at pH 4-5 an acetate buffer pH 4.6 is recommended when higher temperatures are used. 

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