5-Methyltetrahydrofolate Content of Cereal-Based Processed Foods

TLDR: In this article, an optimized method to measure 5-MeTHF in foods was developed and used to measure it in selected processed and ready-to-eat (RTE) foods.

Abstract: Folates are important for human nutrition and health. While certain foods have a significant amount of naturally occurring folate (predominantly 5-Methyltetrahydrofolate, 5-MeTHF), other foods may be fortified with synthetic folic acid. 5-MeTHF and folic acid have comparable physiological activity, however, intake of 5-MeTHF may have advantages over intake of folic acid in terms of reducing the potential for masking of vitamin B 12 deficiency and interaction with drugs that inhibit dihydrofolate reductase. Hence, an optimized method to measure 5-MeTHF in foods was developed and used to measure it in selected processed and ready-to-eat (RTE) foods. The optimized method of extraction, purification and chromatographic separation yielded good recovery of 5-MeTHF (107.1%) in samples. A tripleenzyme digestion procedure accomplished de-proteinization, starch-degradation, and deconjugation of the folate analytes. A Solid Phase Extraction (SPE) device was used to purify sample extracts in a strong anion exchange mode. An isocratic High Performance Liquid Chromatography (HPLC) procedure employing fluorimetric detection was effective in separating and quantifying 5-MeTHF within a 30-minute run-time. The chromatograms of food samples showed well-resolved 5-MeTHF peaks after 19 to 21 minutes retention time. Average 5-MeTHF content of selected food samples ranged from 3 to 32 µg/100g. 5-MeTHF content of cheeses ranged between 5 to 9 µg/100g, while it was 32 µg/100g for milk powder. Frozen vegetables contained 20-31µg/100g of 5-MeTHF. RTE cereals or cereal products contained 4 to 11 µg/100g of 5-MeTHF; with cereal containing the bran having higher amount than their bran-free counterparts. The optimized method can be used to quantify naturally occurring 5-MeTHF in different food matrices; and allow consumers to differentiate between the naturally occurring folate forms and added folic acid in food.