Vitamin B12 (Methylcobalamin)

Methylcobalamin, listed in the Japanese Pharmacopoeia as mecobalamin, is the coenzyme form of vitamin B12 in which a methyl group occupies the upper axial position on the cobalt atom in place of the cyanide ligand of cyanocobalamin (CAS 13422-55-4, C63H91CoN13O14P, Mr 1344.4). It is manufactured by reductive methylation of fermentation-derived cobalamin and isolated as dark red crystals containing approximately 4.4% elemental cobalt calculated from the molecular formula. Biochemically it is the cofactor of methionine synthase, the enzyme that transfers a methyl group to homocysteine in one-carbon metabolism, and formulators specify it where a pre-methylated cobalamin source is wanted in place of a form that the body must first convert. Thovek supplies methylcobalamin against the USP Methylcobalamin monograph, which sets the assay at not less than 98.0% and not more than 102.0% calculated on the anhydrous basis, and against Japanese Pharmacopoeia mecobalamin requirements for buyers working to that standard. Compared with cyanocobalamin the material is markedly more hygroscopic and is readily decomposed by light, so it is milled, sampled, filled and shipped under subdued amber light with a nitrogen headspace, and finished dosage forms normally require opaque or amber packaging. Since the vitamin is dosed in micrograms, it is most often taken as a standardised 0.1% or 1.0% trituration on mannitol or dicalcium phosphate, which gives a free-flowing powder suited to sublingual tablets and lozenges, methylated B-complex blends, vegan and plant-based supplements, effervescent sachets and gummy bases. Pure crystalline material is available for pharmaceutical and analytical use. Every lot is released against identity by HPLC and UV absorption, assay by HPLC, related substances, loss on drying of not more than 12.0%, residual solvents including acetone, elemental impurities to ICH Q3D and USP <232>, and full microbiological limits. Certificate of analysis, safety data sheet, and allergen, GMO and BSE/TSE statements accompany each shipment, with halal, kosher and GMP documentation on request. Material is despatched in light-tight, nitrogen-flushed packing on ISPM-15 heat-treated pallets with complete Indian export documentation.