Chemical synthesis of deuterated folate monoglutamate and in vivo assessment of urinary excretion of deuterated folates in man.

the synthesis and in vivo application of stable-isotopically labeled folic acid was investigated to devise methods suitable for studies of folate metabolism in human subjects. Glutamate-labeled tetradeutero-pteroylglutamic acid (d4-folic acid) was prepared by mixed anhydride coupling of N10-trifluoroacetylpteroic acid and dimethyl L-[3,3,4,4-2H4]glutamic acid, saponification in sodium deuteroxide, and chromatographic purification. Retention of the isotopic label was verified by proton NMR and mass spectrometry of the para-aminobenzoylglutamic acid product of C9-N10 bond cleavage. A method was devised for determination of of isotopic enrichment of urinary d4-folates derived from orally administered d4-folic acid using affinity chromatographic purification, chemical cleavage of the C9-N10 bond, HPLC isolation of the p-[2H4]aminobenzoylglutamate product, followed by negative-ion chemical-ionization gas chromatography/mass spectrometry. Data concerning the urinary excretion of d4-folates derived from an oral dose of d4-folic acid in an adult human are presented.