L-Methylfolate (5-MTHF)

L-Methylfolate is supplied commercially as calcium L-5-methyltetrahydrofolate, the calcium salt of the (6S) diastereomer of 5-methyltetrahydrofolic acid. CAS 151533-22-1, molecular formula C20H23CaN7O6 with variable water of crystallisation, anhydrous formula weight 497.52. Thovek offers it as a white to light yellow or beige crystalline powder assaying 95.0-102.0% on the anhydrous and solvent-free basis in line with the FCC and USP-NF monographs, with L-5-methyltetrahydrofolate content of not less than 85.0% on the dried basis, water of 6.0-17.0% by Karl Fischer and calcium of 7.0-8.5% on the dry basis. It is soluble in alkaline solutions, sparingly soluble in water and very slightly soluble to insoluble in most organic solvents. 5-Methyltetrahydrofolate is the predominant circulating form of folate in plasma and the methyl donor in the remethylation of homocysteine to methionine; it enters the folate pool without the reduction steps that oxidised folic acid requires, which is why formulators specify it where a pre-reduced folate is called for rather than synthetic folic acid. The salt is hygroscopic and sensitive to oxygen, light, heat and low pH, so it is handled under nitrogen, blended without heat and protected with moisture barriers or antioxidants in the finished form. Particle size typically runs at not less than 80% through 80 mesh, which suits direct blending; dilutions and microencapsulated grades are used where the dose is a few hundred micrograms, and a glucosamine salt version is available where greater solution stability is required. Each lot is released against a certificate of analysis covering identification, assay, folate content, water, calcium, chromatographic purity and microbiological limits. Heavy metals are controlled to lead not more than 1.0 mg/kg, arsenic not more than 1.5 mg/kg, cadmium not more than 0.5 mg/kg and mercury not more than 1.5 mg/kg. Export files include MSDS, non-GMO, allergen and BSE/TSE statements, with halal and kosher certificates where held. Under the Indian tariff the specific line 29362910 is reserved for folic acid itself, so this reduced folate salt classifies to the residual line 29362990 under subheading 2936.29.