ines ▁( R NA ▁and ▁DNA ) ▁and ▁m eth ion ine . ▁The ▁un - m eth yl ated ▁form , ▁fol ic ▁acid ▁( v it amin ▁B 9 ), ▁is ▁a ▁synth etic ▁form ▁of ▁fol ate , ▁and ▁must ▁under go ▁en zym atic ▁reduction ▁by ▁di h ydro fol ate ▁re duct ase ▁( D H FR ) ▁to ▁become ▁bi olog ically ▁active . ▁ ▁It ▁is ▁synth es ized ▁in ▁the ▁absor pt ive ▁cells ▁of ▁the ▁small ▁int est ine ▁from ▁poly gl ut am yl ated ▁di et ary ▁fol ate . ▁It ▁is ▁a ▁m eth yl ated ▁derivative ▁of ▁t et rah ydro fol ate . ▁Lev ome fol ic ▁acid ▁is ▁generated ▁by ▁M TH FR ▁from ▁ 5 , 1 0 - m eth y len et et rah ydro fol ate ▁( M TH F ) ▁and ▁used ▁to ▁rec ycle ▁hom oc yst e ine ▁back ▁to ▁m eth ion ine ▁by ▁m eth ion ine ▁synth ase ▁( MS ). ▁ ▁L - m eth yl fol ate ▁is ▁water - sol ub le ▁and ▁primarily ▁ex cret ed ▁via ▁the ▁kid ne ys . ▁In ▁a ▁study ▁of ▁ 2 1 ▁subjects ▁with ▁coron ary ▁ar tery ▁disease , ▁peak ▁pl asma ▁levels ▁were ▁reached ▁in ▁one ▁to ▁three ▁hours ▁following ▁or al ▁or ▁parent eral ▁administration . ▁Pe ak ▁concentr ations ▁were ▁found ▁to ▁be ▁more ▁than ▁seven ▁times ▁higher ▁than ▁fol ic ▁acid ▁(