In 1998, the United States introduced mandatory fortification of enriched cereal-grain products with folic acid to reduce the incidence of neural tube defects. As a consequence, substantial amounts of folic acid, the synthetic form of folate, were added to the American diet, and the ability to assess folic acid intake took on greater importance. The purpose of the current study was to separate and quantify folic acid and 5-methyltetrahydrofolate, the most prominent naturally occurring folate in fortified foods, with a reliable and robust method. Folates were heat-extracted from food samples. A trienzyme treatment (alpha-amylase, rat plasma conjugase, and protease) was applied to the extracts followed by purification by affinity chromatography. Folic acid and 5-methyltetrahydrofolate were separated and quantified by reversed-phase HPLC with fluorescence and UV detection. A gradient elution with phosphate buffer and acetonitrile was used to separate the different forms of folates. The method gave a linear response in a range of 0.1-3 mumol/L and 0.0125-0.25 mumol/L for folic acid and 5-methyltetrahydrofolate, respectively. These ranges were similar to the expected levels in the samples. The CV of the peak areas of folic acid and 5-methyltetrahydrofolate for 5 commercial wheat flour samples extracted and run separately on the same day was 2.0 and 5.7% and, run over 5 consecutive days, was 7.2 and 7.3%, respectively. Total folate values in 45 samples of fortified food measured by HPLC and by the traditional microbiological assay demonstrated a high correlation (r(2) = 0.986).
Objectives: This study reports the influence of colorectal neoplasia on methylation intermediates and folate concentrations in human colonic mucosa, as well as systemic measures of folate status, to examine biomarkers and possible mechanisms of folaterelated carcinogenesis. Subjects: A total of 47 patients were selected from those previously diagnosed with adenocarcinoma of the colorectum undergoing surgery. For each individual, we obtained a biopsy of the adenocarcinoma and a biopsy of normal appearing mucosa, to perform an intra-individual comparison. Results: The 'methylation' ratio (S-adenosylmethionine/S-adenosylhomocysteine (SAH)) was lower in pathological tissue vs normal mucosa (P ¼ 0.08), mainly due to a much higher SAH concentration (Po0.005). Colonic folate concentration was significantly diminished in malignant tissue (Po0.0001). Plasma homocysteine concentration was within the normal to high range, and folate and vitamin B12 plasma concentrations were within the low to normal range as compared with normative values. Conclusion: Our results contribute to the hypothesis that altered DNA methylation and methyl metabolism is associated with colorectal neoplasia.
J. Inst. Brew. 117(2), 188-194, 2011Folates and derivatives usually occur as polyglutamates, in different oxidized forms and substitutions in nature. The multiplicity of forms and the generally low content in food makes quantitative analysis of folate a difficult task. A method that uses affinity chromatography followed by ion-pair high performance liquid chromatography was adapted to the analysis of folate distribution in Spanish beers, with simultaneous information on the pteridine ring structure and the glutamate residues. On average, total folate concentration (as sum of individual vitamers expressed in folic acid) in the analyzed beers was 2.0 µg/100 mL. For all the beers, folates were present as monoglutamates and the analysis showed a total absence of polyglutamyl folates. The distribution of the monoglutamyl folate derivatives analyzed in Spanish beers was: 10-formyltetrahydrofolate (41.7% of total folate), tetrahydrofolate (26.5%), 5-methyltetrahydrofolate (17.2%) and folic acid (14.6%). This study provides new information regarding the distribution of naturally occurring folates in beer and contributes to the assessment of folate bioavailability in this beverage.
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