Vitamin B12

Written by J.A Dobado | Last Updated on April 22, 2024

What is vitamin B12?

Vitamin B12 is a group of vitamers, where the most common form is the compound cyanocobalamin. The human organism can convert cyanocobalamin into any active vitamin B12 compound.

The IUPAC systematic name for cyanocobalamin is cobalt(3+);[(2R,3S,4R,5S)-5-(5,6-dimethylbenzimidazol-1-yl)-4-hydroxy-2-(hydroxymethyl)oxolan-3-yl] [(2R)-1-[3-[(1R,2R,3R,4Z,7S,9Z,12S,13S,14Z,17S,18S,19R)-2,13,18-tris(2-amino-2-oxoethyl)-7,12,17-tris(3-amino-3-oxopropyl)-3,5,8,8,13,15,18,19-octamethyl-2,7,12,17-tetrahydro-1H-corrin-21-id-3-yl]propanoylamino]propan-2-yl] phosphate;cyanide

Chemical structure

Cyanocobalamin has a complex structure, with a central macrocycle core called corrin. It is formed by the asymmetric union of four pyrrole rings, where the four nitrogen atoms are oriented towards the central cobalt ion (Co3+). The corrin ring is similar to the porphyrin ring (of the heme group, chlorophyll and cytochromes). However, it differs from these in its asymmetry in the bonds between the pyrrole groups. In addition, cobalt in this compound has six valences, four of which form a covalent bond with the nitrogen atoms of the pyrrole rings. The fifth coordination valence is always attached to a nitrogen heterocycle (5,6-dimethylbenzimidazole) almost perpendicular to the nucleus. Finally, the sixth valence binds to different functional groups and gives rise to the different derivatives of vitamin B12 (cobalamin). In the specific case of cyanocobalamin, the binding group is cyano (-CN). Other compounds found are: hydroxycobalamin (-OH), methylcobalamin (-Me), adenosylcobalamin (Ado-), adenosylcobalamin (-OH), methylcobalamin (-Me) and adenosylcobalamin (Ado-).

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3D Structure


Vitamin B12 is a key component in: cell formation and longevity, proper digestion, protein synthesis, food absorption and metabolism of fats and carbohydrates. Also, it helps maintain fertility and, along with the other B vitamins, helps produce neurotransmitters.
This last function makes cyanocobalamin useful in the prevention and treatment of depression and other mood disorders.
Vitamin B12 aids in the formation of red blood cells, maintenance of the central nervous system, and helps the body use folic acid.

Food sources

Milk and dairy products, eggs, meat (including poultry), liver, oysters, shellfish and other animal products.

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