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Jägerstad M, Jastrebova J. Occurrence, stability, and determination of formyl folates in foods. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2013; 61:9758-9768. [PMID: 24033320 DOI: 10.1021/jf4028427] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The B-vitamin folate has specific tasks as a one-carbon (C1) group supplier in the building and repair of DNA and RNA as well as in the methylation of homocysteine to methionine. Folate occurs in all living cells as a dynamic pool of several interconvertible forms carrying different C1 groups. Along the food chain, this dynamic pool of folates constantly changes due to either enzymatic or chemical interconversions during food processing and storage. These interconversions make it difficult to determine individual folate forms in foods. The formyl folates, the second most predominant forms of food folates, after 5-methyltetrahydrofolate, are particularly prone to interconvert at low pH. Today, this knowledge is often neglected, leading to risks for analytical underestimation of formyl folates. The purpose of the review is to explore the stability and interconversions of formyl folates in foods as well as to analyze the pitfalls in the determination of formyl folates.
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Affiliation(s)
- Margaretha Jägerstad
- Department of Food Science, Uppsala BioCenter, Swedish University of Agricultural Sciences (SLU) , P.O. Box 7051, SE-750 07 Uppsala, Sweden
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Effects of industrial processing on folate content in green vegetables. Food Chem 2013; 139:815-24. [PMID: 23561177 DOI: 10.1016/j.foodchem.2013.01.067] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2012] [Revised: 12/11/2012] [Accepted: 01/24/2013] [Indexed: 11/22/2022]
Abstract
Folates are described to be sensitive to different physical parameters such as heat, light, pH and leaching. Most studies on folates degradation during processing or cooking treatments were carried out on model solutions or vegetables only with thermal treatments. Our aim was to identify which steps were involved in folates loss in industrial processing chains, and which mechanisms were underlying these losses. For this, the folates contents were monitored along an industrial canning chain of green beans and along an industrial freezing chain of spinach. Folates contents decreased significantly by 25% during the washing step for spinach in the freezing process, and by 30% in the green beans canning process after sterilisation, with 20% of the initial amount being transferred into the covering liquid. The main mechanism involved in folate loss during both canning green beans and freezing spinach was leaching. Limiting the contact between vegetables and water or using steaming seems to be an adequate measure to limit folates losses during processing.
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Wang C, Riedl KM, Somerville J, Balasubramaniam VM, Schwartz SJ. Influence of high-pressure processing on the profile of polyglutamyl 5-methyltetrahydrofolate in selected vegetables. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2011; 59:8709-8717. [PMID: 21770413 PMCID: PMC3850051 DOI: 10.1021/jf201120n] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
In plants, folate occurs predominantly as 5-methyltetrahydrofolate (5MTHF) polyglutamyl forms. Differences in stability and bioavailability of food folate compared to synthetic folic acid have been attributed to the presence of the polyglutamyl chain. High-pressure processing (HPP) was tested for whether it might shorten polyglutamyl chains of 5MTHF species in fresh vegetables by enabling action of native γ-glutamylhydrolase (GGH). A validated ultrahigh-performance reversed-phase liquid chromatography-tandem mass spectrometry method using stable isotope as internal standard was applied for characterizing 5MTHF polyglutamyl profiles. HPP conditions included 300, 450, and 600 MPa at 30 °C for 0 or 5 min, and vegetables were vacuum-packed before treatment. Investigated vegetables included cauliflower (Brassica oleracea), baby carrots (Daucus carota), and carrot greens (D. carota). HPP treatment caused conversion of polyglutamyl 5MTHF species to short-chain and monoglutamyl forms. Maximal conversion of polyglutamyl folate to monoglutamyl folate occurred at the highest pressure/time combination investigated, 600 MPa/30 °C/5 min. Under this condition, cauliflower monoglutamyl folate increased nearly 4-fold, diglutamyl folate 32-fold, and triglutamyl folate 8-fold; carrot monoglutamyl increased 23-fold and diglutamyl 32-fold; and carrot greens monoglutamyl increased 2.5-fold and the diglutamyl form 19-fold. Although some folate degradation was observed at certain intermediate HPP conditions, total 5MTHF folate was largely preserved at 600 MPa/5 min. Thus, HPP of raw vegetables is a feasible strategy for enhancing vegetable monoglutamate 5MTHF.
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Wang C, Riedl KM, Schwartz SJ. A liquid chromatography-tandem mass spectrometric method for quantitative determination of native 5-methyltetrahydrofolate and its polyglutamyl derivatives in raw vegetables. J Chromatogr B Analyt Technol Biomed Life Sci 2010; 878:2949-58. [PMID: 20888309 DOI: 10.1016/j.jchromb.2010.08.043] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2009] [Revised: 08/19/2010] [Accepted: 08/30/2010] [Indexed: 11/26/2022]
Abstract
Folate deficiency is a prevalent phenomenon worldwide especially in underprivileged countries. Polyglutamyl 5-methyltetrahydrofolate (5MTHF) species are the naturally occurring principle folate in store-bought vegetables. Here we report a simple and complete extraction method for the determination of native polyglutamyl 5-methyltetrahydrofolate in vegetables using high performance liquid chromatography with tandem mass spectrometric detection (HPLC-MS/MS). Coarsely chopped samples (18 different vegetables) were steamed to inactivate glutamylase enzymes and liberate folate from binding proteins and extracted in a reducing buffer with (13)C(5) 5MTHF stable isotope added as internal standard. The polyglutamyl 5-methyltetrahydrofolate species were separated in 9 min on a C(18) column using a reversed phase system. HPLC eluate was interfaced with a triple quadrupole mass spectrometer operated in electrospray positive mode. The respective pseudomolecular cation of each polyglutamyl 5-methyltetrahydrofolate species was selected for fragmentation to a common daughter ion for detection. We quantitated polyglutamyl 5-methyltetrahydrofolate in store-bought vegetables from families Brassicaceae, Asteraceae and Amaranthaceae (including mustard greens, romaine lettuce and Swiss chard) of which most have not been quantitated previously. Most vegetables from Asteraceae and those from Amaranthaceae contained similar amounts of monoglutamyl 5MTHF and polyglutamyl 5MTHF while Brassicaceae were dominated by polyglutamyls and endive species (Asteraceae) contained mainly monoglutamyl 5MTHF. The precision of the method for the various polyglutamyl 5-methyltetrahydrofolate forms was 1-9% RSD, recovery 84-91%, limit of detection 64-658 fmol and limit of quantitation 193-1994 fmol. Herein we describe a rapid, sensitive and selective HPLC-MS/MS technique to quantitate polyglutamyl 5-methyltetrahydrofolate species. This method may be suitable for analyzing the polyglutamyl 5-methyltetrahydrofolate profile of inherent folates in a wide range of leafy green vegetables.
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Affiliation(s)
- Chao Wang
- Department of Food Science & Technology and Interdisciplinary Graduate Program in Nutrition, The Ohio State University, 2015 Fyffe Ct, Columbus, OH 43210, USA
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Rychlik M, Englert K, Kapfer S, Kirchhoff E. Folate contents of legumes determined by optimized enzyme treatment and stable isotope dilution assays. J Food Compost Anal 2007. [DOI: 10.1016/j.jfca.2006.10.006] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Influence of feeding different vegetables on plasma levels of carotenoids, folate and vitamin C. Effect of disruption of the vegetable matrix. Br J Nutr 2007. [DOI: 10.1017/s0007114599001385] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Carotenoids, folate and vitamin C may contribute to the observed beneficial effects of increased vegetable intake. Currently, knowledge on the bioavailability of these compounds from vegetables is limited. We compared the efficacy of different vegetables, at the same level of intake (i.e. 300 g/d), in increasing plasma levels of carotenoids, folate and vitamin C and we investigated if disruption of the vegetable matrix would enhance the bioavailability of these micronutrients. In an incomplete block design, sixty-nine volunteers consumed a control meal without vegetables and three out of four vegetable meals (i.e. broccoli, green peas, whole leaf spinach, chopped spinach; containing between 1·7 and 24·6 mg β-carotene, 3·8 and 26 mg lutein, 0·22 and 0·60 mg folate and 26 and 93 mg vitamin C) or a meal supplemented with synthetic β-carotene (33·3 mg). Meals were consumed for 4 d and fasting blood samples were taken at the end of each period. Consumption of the spinach-supplemented meal did not affect plasma levels of β-carotene, although the β-carotene content was 10-fold those of broccoli and green peas, which induced significant increases in plasma β-carotene levels (28 (95 % CI 6·4, 55) % and 26 (95 % CI 2·6, 54) % respectively). The β-carotene-supplemented meal increased plasma concentrations of β-carotene effectively (517 (95 % CI 409, 648) %). All vegetable meals increased the plasma concentrations of lutein and vitamin C significantly. Broccoli and green peas were, when expressed per mg carotenoid consumed, also more effective sources of lutein than spinach. A significant increase in plasma folate concentration was found only after consumption of the spinach-supplemented meal, which provided the highest level of folate. Disruption of the spinach matrix increased the plasma responses to both lutein (14 (95 % CI 3·7, 25) %) and folate (10 (95 % CI 2·2, 18) %), whereas it did not affect the response to β-carotene. We conclude that the bioavailabilities of β-carotene and lutein vary substantially among different vegetables and that the bioavailabilities of lutein and folate from spinach can be improved by disruption of the vegetable matrix.
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Stea TH, Johansson M, Jägerstad M, Frølich W. Retention of folates in cooked, stored and reheated peas, broccoli and potatoes for use in modern large-scale service systems. Food Chem 2007. [DOI: 10.1016/j.foodchem.2006.03.009] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Freisleben A, Schieberle P, Rychlik M. Specific and sensitive quantification of folate vitamers in foods by stable isotope dilution assays using high-performance liquid chromatography-tandem mass spectrometry. Anal Bioanal Chem 2003; 376:149-56. [PMID: 12698226 DOI: 10.1007/s00216-003-1844-y] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2002] [Revised: 01/24/2003] [Accepted: 01/24/2003] [Indexed: 10/20/2022]
Abstract
Stable isotope dilution assays were developed for the quantification of the folate vitamers 5-methyltetrahydrofolate, 5-formyltetrahydrofolate, tetrahydrofolate, 10-formylfolate and pteroylglutamic acid in food samples by using deuterated isotopomers as internal standards. Vitamers and their labeled analogues were analyzed simultaneously by HPLC/MS/MS using selected reaction monitoring, which allowed a higher specificity than other methods published previously. Sample preparation involved treatment by protease in sequence with alpha-amylase and rat serum deconjugase, followed by anion exchange chromatography. The detection limits for 5-methyltetrahydrofolate, 5-formyltetrahydrofolate, tetrahydrofolate, 10-formylfolate and pteroylglutamic acid were found to be 0.5, 1.2, 1.5, 0.6 and 2.6 microg/100 g fresh weight, respectively. Using the new method, folate contents were determined in meat, cereals, and vegetables. Data were in good agreement with literature data, except results for broccoli, which were much lower than reported in previous studies.
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Affiliation(s)
- Achim Freisleben
- Institut für Lebensmittelchemie, Technischen Universität München, Lichtenbergstrasse 4, 85748 Garching, Germany
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Folate determination in Swedish berries by radioprotein-binding assay (RPBA) and high performance liquid chromatography (HPLC). Eur Food Res Technol 2003. [DOI: 10.1007/s00217-002-0656-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Konings EJ, Roomans HH, Dorant E, Goldbohm RA, Saris WH, van den Brandt PA. Folate intake of the Dutch population according to newly established liquid chromatography data for foods. Am J Clin Nutr 2001; 73:765-76. [PMID: 11273852 DOI: 10.1093/ajcn/73.4.765] [Citation(s) in RCA: 189] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
BACKGROUND Determining folate intake is difficult because existing folate data in food-composition tables are scarce and unreliable. OBJECTIVE The purposes of this study were first to analyze 125 of the most important foods that contribute to folate intake in the Netherlands and second to estimate the folate intake of a representative sample of the population. DESIGN We analyzed the folate content of foods by using a newly developed HPLC trienzyme method combined with an affinity chromatography cleanup step. These results were then used to estimate the folate intake of persons aged 1-92 y who participated in the second Dutch National Food Consumption Survey (DNFCS) in 1992 (n = 6218). RESULTS For 35 important folate-containing foods, the mean relative folate contents measured by HPLC were 66%, 80%, and 77% of values for comparable foods included in the British food-composition table; the Ministry of Agriculture, Fisheries and Food table; and the US Department of Agriculture database, respectively. P values for comparison of relative values with 100% were 0.001, 0.171, and 0.144, respectively. The mean dietary folate intake of the DNFCS participants was 182 +/- 119 microg/d. Intake of supplement users (n = 86) was 344 microg/d, with 147 microg/d from supplements. On the basis of these findings, 42% of men and 54% of women do not meet current Dutch recommendations of 60 microg/d for children and 200 microg/d for adults. CONCLUSIONS Total folate quantities in foods, analyzed by HPLC, are approximately 25% lower than amounts listed in recent food-composition tables estimated by use of the microbiological method. On the basis of these new data, approximately 50% of a representative Dutch population sample does not meet the current recommendations for folate intake.
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Affiliation(s)
- E J Konings
- Inspectorate for Health Protection and Veterinary Public Health, 's-Hertogenbosch, Netherlands.
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Thorand B, Kohlmeier L, Simonsen N, Croghan C, Thamm M. Intake of fruits, vegetables, folic acid and related nutrients and risk of breast cancer in postmenopausal women. Public Health Nutr 1998; 1:147-56. [PMID: 10933412 DOI: 10.1079/phn19980024] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
OBJECTIVE To determine the role of fruit and vegetable consumption and dietary intake of folic acid and related nutrients such as methionine, cysteine and alcohol in the aetiology of breast cancer. DESIGN Population based case-control study. SETTING Part of the European Community Multicentre Study on Antioxidants, Myocardial Infarction, and Cancer of the Breast (EURAMIC) in Berlin, Germany. SUBJECTS As part of the EURAMIC study, dietary intake data were collected in 43 postmenopausal women diagnosed with breast cancer between 1991 and 1992 in Berlin, Germany, and compared to 106 population-based controls. RESULTS Odds ratios (ORs) adjusted for major risk factors of breast cancer but not for total energy intake showed a non-significant inverse association between a high intake of vegetables (OR=0.76, 95% CI=0.48-1.20) and fruits (OR=0.74, 95% CI=0.48-1.15) and breast cancer. Once results were adjusted for total energy intake the associations became much weaker (vegetables: R=0.86, 95% CI=0.51-1.46; fruits: OR=0.82, 95% CI=0.51-1.32). For all nutrients, the effect of energy adjustment was more profound and the inverse associations disappeared when results were adjusted for energy intake (total folate-not energy adjusted: OR = 0.79, 95% CI=0.51-1.21; energy adjusted: OR=1.14, 95% CI=0.73-1.79; folate equivalents-not energy adjusted: OR=0.81, 95% CI=0.53-1.23; energy adjusted: OR=1.16, 95% CI=0.78-1.74; methionine-not energy adjusted: OR=0.60, 95% CI=0.35-1.03; energy adjusted: OR=1.29, 95% CI=0.76-2.19; cysteine-not energy adjusted: OR=0.52, 95% CI=0.29-0.94; energy adjusted: OR=1.22, 95% CI=0.75-1.97). Alcohol intake was inversely associated with breast cancer in a non-significant way, possibly due to the relatively low alcohol intake of the study population. CONCLUSIONS The results of this study do not provide firm evidence that a high intake of fruits and vegetables, folic acid, methionine or cysteine reduces the risk of getting breast cancer.
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Affiliation(s)
- B Thorand
- Department of Epidemiology, School of Public Health, University of North Carolina at Chapel Hill, 27599-7400, USA
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Vahteristo L, Lehikoinen K, Ollilainen V, Varo P. Application of an HPLC assay for the determination of folate derivatives in some vegetables, fruits and berries consumed in Finland. Food Chem 1997. [DOI: 10.1016/s0308-8146(96)00318-4] [Citation(s) in RCA: 95] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Müller H. [Intake of folic acid in the total daily diet--effect of food preparation on its folic acid content]. ZEITSCHRIFT FUR LEBENSMITTEL-UNTERSUCHUNG UND -FORSCHUNG 1995; 200:209-12. [PMID: 7785346 DOI: 10.1007/bf01190496] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The folic acid content of total daily diet was determined by means of high-performance liquid chromatography (HPLC). The contents of tetrahydrofolic acid (THF), 5-methyl-THF and 5-formyl-THF were differentiated. The mean of the folic acid content of the total daily diet samples determined analytically was 205 +/- 60 micrograms and the mean of the individual ingredients of the samples was 401 +/- 78 micrograms, which implies that about 50% of folic acid is destroyed by common household food preparation methods. If the contents of pteroylglutamic acid (PteGlu) and 10-formyl-PteGlu (which cannot be determined analytically) are added, it can be assumed that the folic acid content with only be reduced by about 40%. THF and 5-methyl-THF proved to be less stable than 5-formyl-THF. The monoglutamate portion of the total folat content was higher in the total diet samples than in the individual foodstuffs as a consequence of the action of the enzyme "deconjugase" which is released when the matrix of food-stuffs is destroyed.
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Affiliation(s)
- H Müller
- Institut für Ernährungsphysiologie, Bundesforschungsanstalt für Ernährung, Karlsruhe, Germany
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Wigertz K, Jägerstad M. Comparison of a HPLC and radioprotein-binding assay for the determination of folates in milk and blood samples. Food Chem 1995. [DOI: 10.1016/0308-8146(95)00055-n] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Pfeiffer C, Diehl JF, Schwack W. [Dietary folates--a timely review. Stability, physiological significance, bioavailability, analytical determination methods, effect of food handling]. ZEITSCHRIFT FUR ERNAHRUNGSWISSENSCHAFT 1994; 33:85-119. [PMID: 8079510 DOI: 10.1007/bf01622223] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Because of the unequal and, in some instances, low stability of different folate vitamers against extreme conditions the analytical determination of folate and the estimation of folate losses in food processing and preparation cause considerable difficulties. HPLC allows determination of the native folate derivative patterns. As the bioavailability of folates is influenced by a variety of factors and different methods were employed for assessing bioavailability there is a considerable inconsistency in the results of these studies. Folates labeled with radioactive or stable isotopes provide new approaches to metabolic and bioavailability studies.
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Affiliation(s)
- C Pfeiffer
- Institut für Ernährungsphysiologie, Bundesforschungsanstalt für Ernährung, Karlsruhe
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Müller H. [Determination of the folic acid content of grain, cereal products, baked goods and legumes using high-performance liquid chromatography (HPLC)]. ZEITSCHRIFT FUR LEBENSMITTEL-UNTERSUCHUNG UND -FORSCHUNG 1993; 197:573-7. [PMID: 8303952 DOI: 10.1007/bf01192859] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The folic acid content of grain, cereal products (including beer), bakery products and legumes was determined by means of high-performance liquid chromatography (HPLC). Free folate (monoglutamate forms) and total folate (monoglutamate + polyglutamate forms) were differentiated. Of the grain analysed, rye, with a mean value of 143 micrograms/100 g, contained more total folate than wheat (mean = 91 micrograms/100 g). The total folate content of bakery products ranged from 14 micrograms/100 g (whole grain rye bread) to 88 micrograms/100 g (crispbread). Beer had a very low total folate content (mean = 3 micrograms/100 ml). The mean of the free folate portion was 76.5% in grain and cereal products and 65.6% in bakery products. Of the legumes analysed, beans (mean = 128 micrograms/100 g) had the highest content of total folate, followed by lentils (103 micrograms/100 g) and peas (57 micrograms/100 g). The mean value of the free folate portion in legumes (73.1%) was comparable with the values of grain, cereal products and bakery products. In addition to tetrahydrofolic acid (THF), 5-methyl-THF and 5-formyl-THF, pteroylglutamic acid (PteGlu) and 10-formyl-PteGlu were determined in all products (except beer). Their proportion (PteGlu + 10-formyl-PteGlu) of the total folate content ranged from 23.5% to 44.4%.
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Affiliation(s)
- H Müller
- Institut für Ernährungsphysiologie der Bundesforschungsanstalt für Ernährung, Karlsruhe, Deutschland
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Müller H. [The determination of the folic acid content of foods of animal origin using high performance liquid chromatography (HPLC)]. ZEITSCHRIFT FUR LEBENSMITTEL-UNTERSUCHUNG UND -FORSCHUNG 1993; 196:518-21. [PMID: 8328216 DOI: 10.1007/bf01201330] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The folic acid content of food of animal origin was determined by means of high-performance liquid chromatography (HPLC). Free folate (monoglutamate forms) and total folate (monoglutamate + polyglutamate forms) were differentiated. Liver (bovine 963, hog 136 micrograms/100 g) and kidney (bovine 410, hog 93 micrograms/100 g) contained the highest content of total folate, followed by egg (67 micrograms/100 g), soft cheese (44-62 micrograms/100 g), milk and other dairy products (3-28 micrograms/100 g). Chicken, fish, beef and pork contained only a low content of total folate (1-12 micrograms/100 g). The free folate portion ranged from 14.7 to 100% (mean 69.2%). The main folate derivatives tetrahydrofolic acid (THF), 5-methyl-THF and 5-formyl-THF showed the following distribution. In milk and milk products the mean was 70% for 5-formyl-THF, 20% for 5-methyl-THF and 10% for THF; in the other products the three derivatives were distributed about equally but the range of variation was high.
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Affiliation(s)
- H Müller
- Institut für Ernährungsphysiologie, Bundesforschungsanstalt für Ernährung, Karlsruhe, Germany
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