Relative bioavailability of deuterium-labeled monoglutamyl and hexaglutamyl folates in human subjects.
The bioavailability of orally administered mono- and polyglutamyl folates was examined in humans by using stable-isotope methods. [3',5'-2H2]Folic acid (d2-FA) and [3',5'-2H2]pteroylhexaglutamate (d2-PteGlu6) were prepared for oral administration and (glu-2H4)folic acid (d4-FA) was prepared for intravenous (iv) injection. In two trials, adult males (n = 7) on a folate saturation regimen (2 mg/d) were given a single 677-nmol oral dose of either d2-FA or d2-PteGlu6 in apple juice along with an iv injection of 502 nmol d4-FA as a control. Urine was collected for 48 h and the isotope labeling of urinary folates determined by mass spectrometry. The excretion ratio of urinary folates (% of d2-folate dose/% of d4-folate dose) resulting from oral d2-FA and iv d4-FA was 1.45 +/- 0.10 (mean +/- SEM) whereas the ratio for oral d2-PteGlu6 and iv d4-FA was 0.67 +/- 0.04. These results indicate that the d2-PteGlu6 is available to humans as a source of folate although its bioavailability is substantially less than that of d2-FA under these conditions.
Gregory
J F
JF
Food Science and Human Nutrition Department, College of Medicine, University of Florida, Gainesville 32611-0163.
Bhandari
S D
SD
Bailey
L B
LB
Toth
J P
JP
Baumgartner
T G
TG
Cerda
J J
JJ
D000284:Administration, Oral; D000328:Adult; D001682:Biological Availability; D003903:Deuterium; D005492:Folic Acid / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000652:urine; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D007275:Injections, Intravenous; D008297:Male; D011624:Pteroylpolyglutamic Acids / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000652:urine; D012044:Regression Analysis
D011624:Pteroylpolyglutamic Acids; D005492:Folic Acid; D003903:Deuterium