Folic acid group

Folic acid scarcely migrates with neutral solvents on inorganic adsorbents (cf. Table 48). Decomposition products and contaminants can be easily and quickly separated by TLC with 10% ammonium hydroxide on silica gel G (hJS/ = 95) [8] or, according to Ishikawa and Katsxji [70], with acetic acid-acetone-methanofibenzene (5 + 5 + 20 + 70) (hBf = 23) or acetic acid-n-butanol-water (10 + 40 + 50) on alumina G. These procedures are suitable especially for identification in drugs and for purity control of the substance. Bakeb et al. [3], in an investigation 

Amounts of 2 and 10 xg of fohc acid and its derivatives can be detected as dark absorption spots in UV light of 254 and 365 nm, respectively (Table 48). Many pteridines display characteristic fluorescence colours in long-wave UV light, so that substances which are close together on the TLC layer may be distinguished [92]. 

A highly specific detection of folic acid in very low concentrations and in the presence of all other vitamins is accomphshed by spraying with permanganate (Rgt. No. 199) [70, 77]. Even 0.02 [xg can be detected through its blue fiuorescence in UV radiation of 365 nm. In this way, quantitative determination appears possible directly on the chromatogram or after elution of the spots we hope to report on this soon. Quantitative determination should likewise be possible with the help of the sensitive spectrofluorometric method [32]. 

Naturally occurring folic acid compounds which have been separated through TLC are usually evaluated bioautographically on the layer [3]. 

Vitamin C compounds can be separated on various layers (cf. Tables 48 and 54) and separated from further degradation products with, e. g., the systems S /Fi and S /Fg (Table 54). Dehydroascorbic acid yields a compact spot with an hi /-value of 70—80 on sihca gel G, using ethanol or methanol the other water-soluble C-forms migrate less and 

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Nutritional studies with Lactobacillus casei and Streptococcus faecalis R resulted in the discovery of new growth factors given the names norite eluate factor and folic acid, respectively. Assay methods using these two organisms were employed in the isolation of folic acid and related compounds from natural extracts. However, a number of previously reported biological responses to natural extracts may now be attributed to the folic acid group. 

Another member of the folic acid group of vitamins, citrovorum factor or folinic acid, is also found in natural materials, both in free and combined form. Citrovorum factor is believed to be a metabolically active form of folic acid and is formed in the body from folic acid. The citrovorum content of foods is largely unknown. 

These two pathways are linked by enzyme systems in which vitamin Bi2 and the folic acid group of vitamins play an important part. These vitamins are known to be concerned in methylation and nucleic acid metabolism. Ungley (1952) postulates another, but possibly related, function, namely, to detoxicate or otherwise eliminate the inhibitor. It should be emphasized, however, that the above is merely a working hypothesis. The toxic or inhibitory factor, if it exists, may not arise from the intestine but in some other way, e.g., as a result of altered metabolism. An alternative, purely nutritional, hypothesis put forward by Nieweg et al. (1954) is discussed on page 185. 

Bussi et al. (1953) and Cox (1953) divided pernicious anemia serum into protein and nonprotein fractions by ultrafiltration. The inhibitor was usually in the ultrafiltrate. Cox (1953) found that the protein fraction, rid of this inhibitor by ultrafiltration, had maturing properties. Microbiological assays showed that this fraction contained not only bound vitamin B12 but bound forms of the folic acid group of substances including citrovorum factor (Cox, Hornsby et al., unpublished). 

This subject is discussed in reviews by E. L. Smith (1951,1954), Welch and Heinle (1951), Vilter and Mueller (1952), Welch and Nichol (1952), and Nieweg et al. (1954). Both vitamin B12 and the folic acid group of substances (which includes citrovorum factor) are concerned in the formation and transfer of one-carbon intermediates and in the synthesis of... 

The folic acid group of vitamins was recognized by various effects on several test organisms. The simplest active member may be considered to be pteroylglutamic acid or folacin. This may be combined with extra molecules of glutamic acid. Experimental production of a deficiency of these factors has not been reported in man, but the anemia of certain diseases of man responds to folacin therapy. These diseases include sprue, megaloblastic anemia of infancy, nutritional macrocytic anemia, and the pernicious anemia of pregnancy. Folic acid is involved in some way with the metabolism of amino acids. 

This water-soluble acid is a growth factor for certain microorganisms and is an antagonist of sulfonamide drugs. It enters into the structure of the folic acid group and is therefore a metabolite, even though it may not be a dietary essential. 

The evidence that (- )-shikimic acid plays a central role in aromatic biosynthesis was obtained by Davis with a variety of nutritionally deficient mutants of Escherichia coli. In one group of mutants with a multiple requirement for L-tyrosine, L-phenylalanine, L-tryptophan and p-aminobenzoic acid and a partial requirement for p-hydroxybenzoic acid, (—)-shikimic acid substituted for all the aromatic compounds. The quintuple requirement for aromatic compounds which these mutants displayed arises from the fact that, besides furnishing a metabolic route to the three aromatic a-amino acids, the shikimate pathway also provides in micro-organisms a means of synthesis of other essential metabolites, and in particular, the various isoprenoid quinones involved in electron transport and the folic acid group of co-enzymes. The biosynthesis of both of these groups of compounds is discussed below. In addition the biosynthesis of a range of structurally diverse metabolites, which are derived from intermediates and occasionally end-products of the pathway, is outlined. These metabolites are restricted to certain types of organism and their function, if any, is in the majority of cases obscure. 

In a double-blind, placebo-controlled, randomised clinical trial, the efficacy and safety of folic acid and vitamin Bi2 supplementation in reducing the incidence of diarrhoea and acute lower respiratory infections was evaluated in 1000 North Indian children aged 6-30 months [10 -]. Children in the folic acid groups were observed to have more episodes of diarrhoea compared with those in the placebo group. The investigators concluded that the safety of folic acid supplementation in young children warrants further research. 

One of the first compounds in the folic acid group to be isolated from a fermentation product was rhizopterin, 10-formylpteroic acid (16, 17). 

Fraenkel, G., Blewett, M., and Coles, M., BT, a new vitamin of the B-group and its relation to the folic acid group, and other anti-anemia factors. Nature, 161, 981-983, 1948. 

FIGURE 18.35 Formation of THF from folic acid by the dihydrofolate reductase reaction. The R group on these folate molecules symbolizes the one to seven (or more) glutamate units that folates characteristically contain. All of these glutamates are bound in y-carboxyl amide linkages (as in the folic acid structure shown in the box A Deeper Look Folic Acid, Pterins, and Insect VFingis). The one-carbon units carried by THF are bound at N, or at or as a single carbon attached to both... 

Methyl-tetrahydro folic acid is furthermore, together with vitamin B12 and B6, required to regenerate homocysteine (see Vitamin B12, Fig. 1). Homocysteine results when methionine is used as a substrate for methyl group transfer. During the last few years, homocysteine has been acknowledged as an independent risk factor in atherosclerosis etiology. Folic acid supplementation can help reduce elevated homocysteine plasma levels and is therefore supposed to reduce the risk of atherosclerosis as well [2]. 

NAD and NADP and FMN and FAD, respectively. Pantothenic acid is a component of the acyl group carrier coenzyme A. As its pyrophosphate, thiamin participates in decarboxylation of a-keto acids and folic acid and cobamide coenzymes function in one-carbon metabolism. 

A relatively large number of agents have been utilized to treat this intractable disorder folinic acid (5-formyl-tetrahydrofolic acid), folic acid, methyltetrahydrofolic acid, betaine, methionine, pyridoxine, cobalamin and carnitine. Betaine, which provides methyl groups to the beta i ne ho mocystei ne methyltransferase reaction, is a safe treatment that lowers blood homocysteine and increases methionine. 

In living systems, folinic acid can be synthesized ultimately from folic acid by reduction to tetrahydrofolic acid followed by addition of a 1-carbon fragment to the molecule (N5.N1°-methylenetetrahydrofolate, V). After a 2-step oxidation, the formyl group resides either at the N5 or N10 position or as an equilibrium mixture. The essential reactions are summarized below 32... 

There is, moreover, the field of hypervitaminoses, which has been explored for the fat-soluble vitamins, but hardly touched in the water-soluble vitamins. The production of combined system disease by folic acid therapy of pernicious anemia belongs to this group, but many more instances wait to be recognized. The indiscriminate use of polyvitamin preparations by poorly informed clinicians is bound to mask such states and to delay their discovery. Also, the use of flushing doses of vitamins in diagnostic tests may cause acute hypervitaminoses. 

Group-transfer reactions often involve vitamins3, which humans need to have in then-diet, since we are incapable of realizing their synthesis. These include nicotinamide (derived from the vitamin nicotinic acid) and riboflavin (vitamin B2) derivatives, required for electron transfer reactions, biotin for the transfer of C02, pantothenate for acyl group transfer, thiamine (vitamin as thiamine pyrophosphate) for transfer of aldehyde groups and folic acid (as tetrahydrofolate) for exchange of one-carbon fragments. Lipoic acid (not a vitamin) is both an acyl and an electron carrier. In addition, vitamins such as pyridoxine (vitamin B6, as pyridoxal phosphate), vitamin B12 and vitamin C (ascorbic acid) participate as cofactors in an important number of metabolic reactions. 

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