Folic acid, complexes

Liang, L. Subirade, M. P-Lactoglobulin/folic acid complexes Formation, characterization, and biological implication. J. Phys. Chem. B 2010,114 (19), 6707-6712. 

The folic acid complex functions in the formation of labile methyl groups and also in the synthesis of serine from formate. 

Folic acid is a member of the vitamin B complex found in green plants, fresh fruit, yeast, and liver. Folic acid takes its name from folium, Latin for leaf. Pterin compounds are named from the Greek word for wing because these substances were first identified in insect wings. Two pterins are familiar to any child who has seen (and chased) the common yellow sulfur butterfly and its white counterpart, the cabbage butterfly. Xanthopterin and leu-... 

The folate antagonists, pyrimethamine and sulfadiazine, inhibit the parasite s DHFR/TS synthase enzyme complex and the DHPS, respectively (Fig. 4) (see antimalarial drugs). To avoid deficiency of folic acid in patients treated with antifolate antagonists, folinic acid supplementation is recommended to reduce bone-marrow suppression. 

Para-amino benzoic acid (PABA) is considered to be in the B-complex vitamin family. The human body can make it from folic acid, since PABA forms the middle part of that vitamin ... 

The water-soluble vitamins comprise the B complex and vitamin C and function as enzyme cofactors. Fofic acid acts as a carrier of one-carbon units. Deficiency of a single vitamin of the B complex is rare, since poor diets are most often associated with multiple deficiency states. Nevertheless, specific syndromes are characteristic of deficiencies of individual vitamins, eg, beriberi (thiamin) cheilosis, glossitis, seborrhea (riboflavin) pellagra (niacin) peripheral neuritis (pyridoxine) megaloblastic anemia, methyhnalonic aciduria, and pernicious anemia (vitamin Bjj) and megaloblastic anemia (folic acid). Vitamin C deficiency leads to scurvy. 

Water-soluble vitamins removed by hemodialysis (HD) contribute to malnutrition and vitamin deficiency syndromes. Patients receiving HD often require replacement of water-soluble vitamins to prevent adverse effects. The vitamins that may require replacement are ascorbic acid, thiamine, biotin, folic acid, riboflavin, and pyridoxine. Patients receiving HD should receive a multivitamin B complex with vitamin C supplement, but should not take supplements that include fat-soluble vitamins, such as vitamins A, E, or K, which can accumulate in patients with renal failure. 

The water-soluble vitamins generally function as cofactors for metabolism enzymes such as those involved in the production of energy from carbohydrates and fats. Their members consist of vitamin C and vitamin B complex which include thiamine, riboflavin (vitamin B2), nicotinic acid, pyridoxine, pantothenic acid, folic acid, cobalamin (vitamin B12), inositol, and biotin. A number of recent publications have demonstrated that vitamin carriers can transport various types of water-soluble vitamins, but the carrier-mediated systems seem negligible for the membrane transport of fat-soluble vitamins such as vitamin A, D, E, and K. 

Yao Z, Li C, Shi G (2008) Optically active supramolecular complexes of water-soluble achiral polythiophenes and folic acid spectroscopic studies and sensing applications. Langmuir 24 12829-12835... 

Folic acid is a complex molecule centrally involved in the metabolism of one-carbon molecular fragments the methyl, hydroxymethyl, and formyl groups. 

Folic acid is a vitamin, as we developed in chapter 15. It is a complex molecule that serves as an essential precursor for coenzymes involved in the metabolism of one-carbon units. For example, folic acid-derived coenzymes are critically involved in the biosynthesis of thymidine for nucleic acid synthesis and methionine for protein biosynthesis. The synthesis of both demands donation of a methyl group and they come from folic acid-derived coenzymes. 

In contrast to humans, bacteria have the biochemical ability to synthesize folic acid from simpler molecules. Here we have a clear biochemical difference between human beings and infectious organisms that we can exploit to our benefit. The reaction catalyzed by an enzyme known as dihydropteroate synthetase, in which a complex heterocycle is linked to p-aminobenzoic acid, is key. Now recognize the structural similarity between sulfanilamide, or other sulfonamides, and p-aminobenzoic acid ... 

Compared with other vitamins, the chemical structures of both folic acid and B12 are complex. They are prosthetic groups for the enzymes that catalyse the transfer of the methyl group (-CH3) between compounds (one-carbon metabolism). The -CH3 group is chemically unreactive, so that the chemistry for the transfers is difficult, requiring complex structures for catalysis. 

The structure of cobalamin is more complex than that of folic acid (Figure 15.2 and 15.3). At its heart is a porphyrin ring containing the metal ion cobalt at its centre. In catalytic reactions the cobalt ion forms a bond with the one-carbon group, which is then transferred from one compound to another. Vitamin B12 is the prosthetic group of only two enzymes, methylmalonyl-CoAmutase and methionine synthase. The latter enzyme is particularly important, as it is essential for the synthesis of nucleotides which indicates the importance of vitamin B12 in maintenance of good health. 

Competitive inhibitors bind to specific groups in the enzyme active site to form an enzyme-inhibitor complex. The inhibitor and substrate compete for the same site, so that the substrate is prevented from binding. This is usually because the substrate and inhibitor share considerable stmctural similarity. Catalysis is diminished because a lower proportion of molecules have a bound substrate. Inhibition can be relieved by increasing the concentration of substrate. Some simple examples are shown below. Thus, sulfanilamide is an inhibitor of the enzyme that incorporates j9-aminobenzoic acid into folic acid, and has antibacterial properties by restricting folic acid biosynthesis in the bacterium (see Box 11.13). Some phenylethylamine derivatives, e.g. phenelzine, provide useful antidepressant drags by inhibiting the enzyme monoamine oxidase. The cA-isomer maleic acid is a powerful inhibitor of the enzyme that utilizes the trans-isomer fumaric acid in the Krebs cycle. 

Riboflavin, folic acid and lumiflavin each bind one Ru(bpy)2 unit. The MLCT spectra of the complexes are pH dependent, and an a-iminocarbonyl chelating mode for each ligand is proposed. Coordination results in a lowering of the values ( 9 to 5) of the N(3)-H protons." ... 

Water-soluble vitamins in formulations have been determined by use of ion-pair chromatography. The vitamins include several B vitamins as well as niacin, folic acid, and ascorbic acid (565). Vitamins D and Da were rapidly separated on reverse phase columns (247) as are vitamins A, D, and E in multivitamin tablets (564). Addition of silver ions to the mobile phase has been shown to increase the flexibility inherent in RPC by complexing with the unsaturated bonds and thereby decreasing the retention factor. This effect is also observed with other unsaturated drug molecules including steroids (247). Vitamin A and related compounds have... 

Linear dependence of log k on the number of molecule units in homologs is observed to hold for a variety of substances, such as for oli-goalanines (20J) and oligo-y-glutamates of folic acid 204) depicted in Figs. 40 and 41, respectively. The analysis of such plots is complex because ol the pulai functions present in the molecules. Moreover, the effect of ionization must be considered. 

Thiamine, riboflavin, nicotinamide, pyridoxine, and folic acid can be determined together by using DAD, but pantothenic acid and biotin do not have adequate sensitivity for UV detection in complex matrices. 

The reduction mechanism of Cd(II)-fer rone complexes accumulated on static mercury electrode was studied using square wave voltammetry (SWV) [92]. The electrochemical behavior of Cd(II) complexes with cysteine and folic acid was investigated. Folic acid forms adducts... 

The Falin-Ciocalteu reagent (FCR) is a complex formed in a reaction between sodium tungstate and sodium molybdenate in hydrochloric add and phosphoric acid, which turns yellow after lithium sulphate is added. The reagent reads in an alkaline environment with reducing compounds. Such a reaction gives a blue chromophore which is observed by colorimetry. The Folin-Ciocalteu method is highly sensitive - both to phenolic and non-phenolic compounds, e.g. proteins, vitamin C, vitamin Bj, folic acid, Cu(I). The method is applied most frequently to determine the total content of phenolic compounds [34,35]. If that is the case, a sample for determination should be prepared in a proper manner to minimise the effect of non-phenolic... 

Vitamins and Minerals. Milk is a rich source of vitamins and other organic substances that stimulate microbial growth. Niacin, biotin, and pantothenic acid are required for growth by lactic streptococci (Reiter and Oram 1962). Thus the presence of an ample quantity of B-complex vitamins makes milk an excellent growth medium for these and other lactic acid bacteria. Milk is also a good source of orotic acid, a metabolic precursor of the pyrimidines required for nucleic acid synthesis. Fermentation can either increase or decrease the vitamin content of milk products (Deeth and Tamime 1981 Reddy et al. 1976). The folic acid and vitamin Bi2 content of cultured milk depends on the species and strain of culture used and the incubation conditions (Rao et al. 1984). When mixed cultures are used, excretion of B-complex vita-... 

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