(6r,s)5,6,7,8tetrahydrofolic acid (hydrochloride)

Tetrahydrofolic acid trihydrochloride (L-5,6,7,8-Tetrahydrofolic acid trihydrochloride) is a biologically active vitamin B9 derivative, a receptor for free formaldehyde, and an effective suicide substrate for mushroom tyrosinase, inhibiting indole ethylamine methylation by methyl-tetrahydrofolate.

Tetrahydrofolic acid (5,6,7,8-tetrahydrofolic acid) is a vitamin B9 derivative that is a common one-carbon donor in organisms and is involved in growth and metabolism.

(6S)-Tetrahydrofolic acid has 1000 times greater activity in promoting the binding of fluorodeoxyuridine monophosphate with thymidylate synthase compared to the (6R) form and exhibits 600 times higher activity as a growth factor for brewer's yeast (P. cerevisiae). It also has low affinity and high dissociation rates from folate-binding proteins.