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ARS Home » Northeast Area » Boston, Massachusetts » Jean Mayer Human Nutrition Research Center On Aging » Research » Publications at this Location » Publication #201758
Title: Use of the affinity/HPLC method for quantitative estimation of folic acid enriched cereal grain products

Author
item POO-PRIETO, ROSALIA - TUFTS/HNRCA
item HAYTOWITZ, DAVID - NUTRIENT DATA LAB, USDA
item HOLDEN, JOANNE - NUTRIENT DATA LAB, USDA
item ROGERS, GAIL - TUFTS/HNRCA
item CHOUMENKOVITCH, SILLVINA - TUFTS/HNRCA
item Jacques, Paul
item Selhub, Jacob

Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/20/2006
Publication Date: 12/1/2006
Citation: Poo-Prieto, R., Haytowitz, D.B., Holden, J.M., Rogers, G., Choumenkovitch, S.F., Jacques, P.F., Selhub, J. 2006. Use of the affinity/HPLC method for quantitative estimation of folic acid enriched cereal grain products. Journal of Nutrition. 136:3079-3083.

Interpretive Summary: In 1998 the US has mandated a program to fortify the flour and other cereal with the vitamin folic acid. Folic acid is not a natural vitamin and its integration into the body is different than the natural folate which is found in food. Folic acid is more efficiently taken up by the body and it is estimated that one unit of folic acid is equivalent to 1.7 units of natural folate. In this paper we have devised a method to determine the amount of folic acid from fortification. This is important since the measure of daily requirement takes into account the superiority of folic acid vs food folate.

Technical Abstract: In 1998, mandatory fortification of enriched cereal-grain products with folic acid was introduced in the United States 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 a 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 ('-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 nmol/mL and 0.0125 - 0.25 nmol/mL for folic acid and 5-methyltetrahydrofolate, respectively. These ranges were similar to the expected levels in the samples. The coefficient of variation of the peak areas of folic acid and 5-methyltetrahydrofolate for five commercial wheat flour samples extracted and run separately on the same day was 2.0% and 5.7% and run over five 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 (r2= 0.986).