Folinic Acid (Calcium Folinate)

Folinic acid is 5-formyl-5,6,7,8-tetrahydrofolic acid, a reduced folate that already carries the tetrahydro ring and a formyl group at N5, so it enters the one-carbon folate pool without the dihydrofolate reductase step that pteroylglutamic acid requires. The free acid (CAS 58-05-9, C20H23N7O7, MW 473.44) is too unstable for bulk trade, so the article actually shipped is the calcium salt, calcium folinate, CAS 1492-18-8, molecular formula C20H21CaN7O7·xH2O with a molecular weight of 511.50 on the anhydrous basis. The European Pharmacopoeia sets the assay at 97.0 to 102.0 per cent on the anhydrous substance, calcium at 7.54 to 8.14 per cent, water at not more than 17.0 per cent (commercial material sits close to the pentahydrate) and specific optical rotation at +14.4 to +18.0 degrees. On the molecular weights, 10.8 mg of anhydrous calcium folinate supplies 10 mg of folinic acid, which is the conversion to use when writing a label or a blend sheet. Stereochemistry is the single most important commercial variable and it is where buyers get caught. Standard calcium folinate is a diastereomeric pair: the glutamate centre is fixed as L, but the C6 centre of the pteridine ring is racemic, so half the material is the (6R) diastereomer. Only the (6S) form is metabolically usable. If a specification calls for the single active isomer, that is a different article - calcium levofolinate, CAS 80433-71-2 - which is priced and documented separately and should not be substituted with the racemic salt. Physically the material is a white to light yellow amorphous or crystalline powder, sparingly soluble in water and practically insoluble in ethanol and acetone. It is hygroscopic and both light and oxygen sensitive, so it is packed under nitrogen in light-resistant containers with desiccant, and drums are best opened in a controlled-humidity area. Regulatory position needs checking before you order, because it differs sharply by market. In the European Union the folate sources permitted in food supplements under Annex II of Directive 2002/46/EC are pteroylmonoglutamic acid, calcium-L-methylfolate and (6S)-5-methyltetrahydrofolic acid glucosamine salt - calcium folinate is not on that list. In the United States the same substance is the approved drug leucovorin calcium, which raises the drug-exclusion question for dietary supplement use. Outside supplements the material is used as a pharmacopoeial API, as a folate source in cell culture media, and as an analytical reference. Thovek ships from India against Ph. Eur./BP or USP specification with a batch certificate of analysis covering HPLC assay, water by Karl Fischer, related substances, residual solvents and heavy metals, plus MSDS, allergen and vegan declarations and a non-GMO statement.