QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Wei, M.-M. Articles by Gregory, J. F. Search for Related Content PubMed PubMed Citation Articles by Wei, M.-M. Articles by Gregory, J. F., III

Bioavailability for Humans of Deuterium-Labeled Monoglutamyl and Polyglutamyl Folates Is Affected by Selected Foods^1,2,3,

Food Science and Human Nutrition Department, University of Florida, Gainesville, FL 32611-0370

Dietary folate exists mainly as polyglutamyl forms that require deconjugation by Zn-dependent pteroylpolyglutamate hydrolase prior to intestinal absorption. Because deconjugation by pteroylpolyglutamate hydrolase is an essential step in the absorption of dietary polyglutamyl folates, factors influencing the deconjugation process may affect folate bioavailability. This study was conducted to evaluate in vivo the bioavailability of [²H₄]folic acid (d₄-PteGlu₁) and [²H₂]-pteroylhexaglutamate (d₂-PteGlu₆) administered in solution in water or citrate buffer or added to selected foods using a single-dose, dual-label protocol. In each of six trials, healthy men (n = 7) were given a single oral dose of d₂-PteGlu₆ and d₄-PteGlu₁ (677 nmol of each form) blended into orange juice, tomatoes, lima beans, 52 mmol/L citrate (pH 4.1), or water as the control. Urine was collected for 48 h and the isotopic labeling of urinary folates used as criteria of the relative bioavailability of administered PteGlu₁ and PteGlu₆. Urinary excretion of d₄-folates and d₂-folates derived from the respective oral doses did not differ from the control in any treatment within the statistical power of this protocol. High relative bioavailability of the polyglutamyl folate was reflected by ratios of urinary d₂/d₄ folates of 1.0 for control, tomato, lima bean and citrate buffer trials, whereas the ratio of urinary d₂/d₄ folates when subjects consumed orange juice was 33% less than the control ratio (P < 0.05). These findings suggest that the bioavailability of polyglutamyl folates in orange juice would be partially incomplete. However, this would be compensated by the high total folate concentration of orange juice. The relation of these findings to endogenous dietary folates requires further investigation.

KEY WORDS: • folate • pteroylpolyglutamate hydrolase • bioavailability • humans • stable isotopes

¹ Presented in abstract form at Experimental Biology 95, April 1995, Atlanta, GA [Gregory, J. F., Wei, M. M., Bailey, L. B. & Toth, J. P. (1995) Bioavailability of deuterated folates added to foods. FASEB J. 9: A154 (abs.)].

² Supported by U.S. Department of Agriculture NRICGP grant # 91-37200-6305. This paper is Florida Agricultural Experiment Station Journal Series No. R-05132.

³ The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 USC section 1734 solely to indicate this fact.

⁴ To whom correspondence should be addressed.

Manuscript received 29 April 1996. Revision accepted 23 August 1996.

This article has been cited by other articles:

				A. Melse-Boonstra, P. Verhoef, C. E West, J. A van Rhijn, R. B van Breemen, J. J. Lasaroms, S. D Garbis, M. B Katan, and F. J Kok A dual-isotope-labeling method of studying the bioavailability of hexaglutamyl folic acid relative to that of monoglutamyl folic acid in humans by using multiple orally administered low doses. Am. J. Clinical Nutrition, November 1, 2006; 84(5): 1128 - 1133. [Abstract] [Full Text] [PDF]

				D. J McKillop, H. McNulty, J. M Scott, J. M McPartlin, J. Strain, I. Bradbury, J. Girvan, L. Hoey, R. McCreedy, J. Alexander, et al. The rate of intestinal absorption of natural food folates is not related to the extent of folate conjugation Am. J. Clinical Nutrition, July 1, 2006; 84(1): 167 - 173. [Abstract] [Full Text] [PDF]

				A. Melse-Boonstra, C. E West, M. B Katan, F. J Kok, and P. Verhoef Bioavailability of heptaglutamyl relative to monoglutamyl folic acid in healthy adults Am. J. Clinical Nutrition, March 1, 2004; 79(3): 424 - 429. [Abstract] [Full Text] [PDF]

				G. Basset, E. P. Quinlivan, M. J. Ziemak, R. Diaz de la Garza, M. Fischer, S. Schiffmann, A. Bacher, J. F. Gregory III, and A. D. Hanson Folate synthesis in plants: The first step of the pterin branch is mediated by a unique bimodular GTP cyclohydrolase I PNAS, September 17, 2002; 99(19): 12489 - 12494. [Abstract] [Full Text] [PDF]