46F-16 |
Quantitation of 5-methyltetrahydrofolate in fresh fruits and vegetables |
K. M. WUNDERLICH1, K. M. Phillips1, D. M. Ruggio1, G. Beecher2, and R. Doherty2. (1) Department of Biochemistry, Virginia Polytechnic Institute and State University, 304 Engel Hall, Blacksburg, VA 24061, (2) Food Composition Laboratory, USDA Beltsville Agricultural Reseach Center, Bldg-161, 10300 Baltimore Avenue, Beltsville, MD 20705 5-methyltetrahydrofolate (5MTHF) is the predominant folate vitamer in fresh fruits and vegetables. Existing data for folate in foods is based on microbiological assay which may not accurately reflect actual folate content. New HPLC methods allow chemically definitive determination of folate in foods. However HPLC folate data are not well represented in U.S. food composition databases. The goal of this study was to quantify 5MTHF in a wide range of U.S. fresh fruits and vegetables sampled nationwide for the USDA National Food and Nutrient Analysis Program. Folate was extracted from homogenized fresh-frozen produce after treatment with protease, a-amylase, and rat plasma conjugase, purified by anion-exchange solid-phase extraction, then quantified by reverse-phase HPLC with fluorescence and diode-array detection. The method was validated by analysis of available reference materials, including BCR 485 (freeze dried mixed vegetables) and BCR 121 (wholemeal flour). Quality control samples were run with each analytical batch to monitor inter-assay precision. 5MTHF content varied widely among different types of produce, ranging from <2 µg/100g in bananas and green leaf lettuce to 45-50 µg/100g, respectively, in canned spinach and raw broccoli. The relative standard deviation for replicate analyses was generally <5% within an assay and <15% between assays for samples with >20 µg/100g 5MTHF, and the practical limit of quantitation was ~7 µg/100g. These results suggest that HPLC methodology can be succesfully applied for the quantitation of 5MTHF in a wide variety of fresh produce matices. Further development and validation of the method is required for definitive quantitation of other folate vitamers.
Session 46F, Nutrition
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