In vivo characterization of the absorption and biotransformation of pteroylmonoglutamic acid in man: a model for future studies

Biochemical Medicine and Metabolic Biology
Mark D LucockR Hartley

Abstract

HPLC-EC has been used to measure the appearance of 5-CH3-H4 folic acid in human plasma following oral administration of folic acid. The process was found to be saturable in accordance with Michaelis-Menten kinetics. The apparent Km for this enzyme system indicates that low doses of oral folic acid are rapidly converted into 5-CH3-H4 folic acid, an observation consistent with the needs of intestinal absorption of essential trace nutrients. The appearance of L. casei active folate in plasma was not rate-limited and showed a biphasic relationship to dose. Preparative HPLC combined with L. casei bioassay demonstrated that most of the L. casei active folate appearing in plasma following a 20,000-micrograms dose of folic acid was due to the unmodified vitamin, only 5.6% being due to 5-CH3-H4 folic acid and with no detectable contribution from 5-CHO-H4 folic acid. The absorption characteristics of the system seem consistent between and within subject(s). No relationship could be demonstrated between predose levels of plasma 5-CH3-H4 folic acid and total folate in erythrocytes, which reflect the status of transport and storage forms of the vitamin, respectively.

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Citations

May 1, 1993·The British Journal of Nutrition·C BowerD J Nicol
Oct 10, 2001·The British Journal of Nutrition·P J MoynihanA J Adamson
Dec 25, 2003·The Proceedings of the Nutrition Society·Paul M FinglasJack R Dainty
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Jan 24, 2004·BMJ : British Medical Journal·Mark Lucock
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Jun 27, 2006·Lancet·María Luisa Martínez-Frías
May 10, 2017·Proceedings of the National Academy of Sciences of the United States of America·Mark LucockEmma Beckett
Sep 6, 2005·Human & Experimental Toxicology·M B Forrester
Jan 13, 2015·Preventive Nutrition and Food Science·Jeong-Hwa ChoiMark Lucock
Mar 2, 2005·Nature Reviews. Genetics·Mark Lucock, Zoë Yates
Oct 21, 2006·Current Opinion in Clinical Nutrition and Metabolic Care·Mark D Lucock
Sep 4, 2009·Current Opinion in Clinical Nutrition and Metabolic Care·Mark Lucock, Zoe Yates
Jul 26, 2005·The International Journal of Psycho-analysis·Jacó ZaslavskyCláudio Laks Eizirik
Oct 10, 2015·The Journal of Nutrition·Lynn B BaileyDaniel J Raiten

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