1. Tetrahydrofolic acid (Coenzyme F) .

2. The Coenzyme tetrahydrofolic acid is derived in humans from the B-complex vitamin folic acid

3. Also, a process for tetrahydropteridine N5-formylation for the preparation of, for example, N5-formyl-(6S)-tetrahydrofolic acid.

4. As demonstrated with the model system of cultured human lymphoblasts the cytostatic effect of amethopterine (Methotrexate®) can be overcome by methyl-tetrahydrofolic acid.

5. The results indicate that 5-formyl-tetrahydrofolic acid given in the tested form has nearly the same bioavailability (ratio: 1.02) as folic acid (pteroylmonoglutamic acid) in aqueous solution.