Serum folates in man.

Abstract

SUMMARY In an aseptic microbiological assay of folate compounds and their breakdown compounds, using Lactobacillus casei, Streptococcus faecalis, and Pediococcus cerevisiae, 4a-hydroxy-5-methyl-4,5,6,7-tetrahydrofolate and 5-methyl-5,8-dihydrofolate were inactive under all conditions to all three organisms and 5-methyl-5,6-dihydrofolate was inactive unless ascorbate was present in the incubation medium, and then only to L. casei. 5-Methyltetrahydrofolate was active only for L. casei, and activity in purified samples to S. faecalis was due to trace amounts of folic acid. Analysis of S. faecalis values in the serum in normal subjects and in patients with various disorders showed that levels of 10-formyltetrahydrofolate are raised in coeliac disease, leukaemia, rheumatoid arthritis, and schizophrenia.5-Methyltetrahydrofolate is readily absorbed by normal human subjects and by patients with pernicious anaemia but poorly absorbed by patients with coeliac disease or leukaemia. 5-Methyl-5,6-dihydrofolate was quickly absorbed by normal human subjects, being reflected by a considerably raised level of 5-methyltetrahydrofolate in serum when sodium bicarbonate was given by mouth before the 5-methyl-5,6-dihydrofolate. These higher levels were comparable to those in patients with pernicious anaemia after oral administration of 5-methyl-5,6-dihydrofolate. Oral 5-methyl-5,8-dihydrofolate and 4a-hydroxy-5-methyl-tetrahydrofolate did not appear as microbiologically active folates in the serum.The findings of this study suggest that the availability for biological utilisation of the major dietary folate compounds will depend on the amount of gastric acidity and of ascorbate in the intestinal chyme. Many may be unavailable for metabolic utilization in the body.

Folic acid complexes with human and bovine serum albumins

“…The best folate sources in foods are green leafy vegetables, sprouts, fruits, liver, and kidney. It is known that plasma folates are associated with low affinity binding proteins (Herbert, Larrabee, & Buchanan, 1962;Thien et al, 1977). Folic acid is known to be sensitive to UV-radiation (Jamil, Ataullah, & Ahmed, 2003;Off et al, 2005).…”

L-ascorbic acid improves the serum folate response to an oral dose of [6S]-5-methyltetrahydrofolic acid in healthy men

“…[6S]-5-CH 3 H 4 PteGlu, however, exhibits a significant instability toward oxygen and low pH, resulting in oxidation to 5-methyldihydrofolate (5-CH 3 H 2 PteGlu) (Donaldson and Keresztesy, 1962), that is absorbed in the gut but does not appear to enter the folate metabolic pool (Thien et al, 1977). In addition, 5-CH 3 H 2 PteGlu is rapidly degraded in the acid-peptic gastric environment, resulting in significant losses of folate during digestion (Lucock et al, 1995;Seyoum and Selhub, 1998).…”

“…In addition, 5-CH 3 H 2 PteGlu is rapidly degraded in the acid-peptic gastric environment, resulting in significant losses of folate during digestion (Lucock et al, 1995;Seyoum and Selhub, 1998). Since antioxidants such as L-ascorbic acid (L-AA) convert 5-CH 3 H 2 PteGlu into 5-CH 3 H 4 PteGlu (Donaldson and Keresztesy, 1962;Lucock et al, 1995) and protect [6S]-5-CH 3 H 4 PteGlu against oxidative degradation (Oey et al, 2006), it has been stated that normal endogenous gastric L-AA concentrations, as secreted in the gastric lumen, might be a critical factor in optimizing the bioavailability of natural folate (Thien et al, 1977;Lucock et al, 1995). However, in vivo evidence regarding the influence of L-AA on natural folate bioavailability is limited to long-term studies in which L-AA supplementation has indirectly been related to an enhancement of blood folate indices in elderly (Bates et al, 1980;Kyllastinen et al, 1990).…”

Effect of Folate Supplementation on Inflammatory Markers in Individuals Susceptible to Depression: A Systematic Review

“…17 Due to humans not being able to synthesize folate, it must be obtained from dietary sources, such as leafy green vegetables, with the main forms in food being 5-methyltetrahydrofolate (5-MTHF) and formyltetrahydrofolate. 18 The main structural differences between natural and synthetic forms of folate are the oxidation state, the number of conjugated glutamic acid moieties and the type of one-carbon substituents at the N5 and N10 positions. 17 Dietary folate is predominantly 5-MTHF, which is the biologically active form of the vitamin but may also exist as formyltetrahydrofolate or in the oxidized form 5-methyl-5,6-dihydrofolate.…”