(6S)-tetrahydrofolate 29347-89-5 5,6,7,8-tetrahydrofolate 5,6,7,8-tetrahydrofolic acid FH4 H4F H4PteGlu H4PteGlu1 THF folate-H4 tetra-H-folate tetrahydrafolate tetrahydrofolate tetrahydrofolic acid tetrahydropteroyl mono-L-glutamate tetrahydropteroylglutamate th-folate