Nicotinic acid anion

Fig. 3 Electropherogram of five water-soluble vitamines thiamine (cationic), nicotinamide (nonionic), biotin (anionic), ascorbic acid (anionic), and nicotinic acid (anionic) in 20 mM phosphate run buffer at pH 8.0.

Surface-enhanced Raman spectroscopy was intensively used to study organic additives on silver, copper, and gold." An example is an investigation of the orientation of nicotinic acid on silver. The Raman spectra were measured at different pH values. This is shown in Figure 7.29a. Preferential adsorption of the nicotinic acid anion was observed. The dissociation reactions are shown in Figure 7.29b. 

Another measurement was made as a function of the potential (Figure 7.30). The final conclusion is that the nicotinic acid anion was adsorbed flat on the surface for pH < 9 and was in an upright position for pH > 9. The nicotinic acid anion was bound to the silver surface by the nitrogen atom (Figure 7.31). ... 

Attempts to isolate GTF from brewer s yeast have resulted in production of very active concentrates, but the substance is too labile to be obtained in the soHd state (136). However, it has been shown that GTF is a Cr(III) complex containing two coordinated nicotinate radicals and other amino acid anions (146). Active preparations containing similar complexes have been synthesi2ed (147). Chromium deficiency may also lead to atherosclerosis and peripheral neuropathy. 

Preparation of the first of these antiinflammatory prodrugs starts with the displacement of halogen on bromophthal ide 2 by the anion of the nicotinic acid derivative 1. Reaction of the intermediate 3 with aniline 4 leads to formation of talniflumate (5). ... 

Recently, Prasad et al. cloned a mammalian Na+-dependent multivitamin transporter (SMVT) from rat placenta [305], This transporter is very highly expressed in intestine and transports pantothenate, biotin, and lipoate [305, 306]. Additionally, it has been suggested that there are other specific transport systems for more water-soluble vitamins. Takanaga et al. [307] demonstrated that nicotinic acid is absorbed by two independent active transport mechanisms from small intestine one is a proton cotransporter and the other an anion antiporter. These nicotinic acid related transporters are capable of taking up monocarboxylic acid-like drugs such as valproic acid, salicylic acid, and penicillins [5], Also, more water-soluble transporters were discovered as Huang and Swann [308] reported the possible occurrence of high-affinity riboflavin transporter(s) on the microvillous membrane. 

Takanaga, H., et al. Nicotinic acid transport mediated by pH-dependent anion antiporter and proton cotransporter in rabbit intestinal brush-border membrane. J. Pharm. Pharmacol. 1996, 48, 1073-1077. 

The B-group vitamin, nicotinic acid (259), was irradiated with low-intensity light at 254 nm. In aqueous solution without buffer, the bi-aryl (260) was obtained, presumably via decarboxylation to give the pyridyl anion which would attack position 6 of nicotinic acid. In aqueous acid, the substrate was photo-hydroxylated to give 2-hydroxynicotinic acid (40%). Clearly, only the cationic form was sufficiently activated for position 2 to be attacked by the solvent. Nicotinamide under the same conditions was also converted to the 2-hydroxy derivative, but the reaction was slower [161]. 

The laboratory must be informed when the therapeutic regimens include drugs specifically administered to change the blood level of a biochemical constituent. Cholestyramine resin, a nonabsorbable anion exchange resin administered orally to patients with hyperlipoproteinemia produced a 24% decline in serum cholesterol levels in 14 patients with essential hypercholesterolemia. In these patients the mean cholesterol fell from 414 98 mg/100 ml to 176 21 mg/100 ml (FI). Pectin added to the diet caused a 5% decrease in serum cholesterol values (K4), as did an oral hydrophobic colloid (G4). Levels fell in one case from 220 mg/ 100 ml to 160 mg/100 ml (G4). Nicotinic acid, neomycin, and p-chloro-phenoxyisobutyrate have all been used to reduce serum cholesterol (G7). 

The degradation of nicotinic acid by Clostridium barkeri involves the cleavage of the intermediate 2,3-dimethylmalate 132 from which propionic and pyruvic acids are formed by a specific lyase (EC 4.1.3.32). In the reverse direction, the enzyme must have the unusual capacity to deprotonate propionic acid at the a-carbon instead of the carboxylic acid function, or next to an anionic car-boxylate. Purified dimethylmalic acid aldolase has been used to catalyze the stereospecific addition of 133 to the oxoacid acceptor, yielding the (2R,3S) configurated dimethylmalic acid 132 at the multi-gram scale [381]. The substrate tolerance of this enzyme has not yet been determined. 

Drugs used in treatment statins fibric acid derivatives anion-exchange resins nicotinic acid and derivatives... 

Familial or polygenic hypercholesterolaemia is treated by dietary modification and a statin an anion-exchange resin and/or a fibrate and/or nicotinic acid may be added. 

Fig. 3-66. Separation of monovalent anions using nicotinic acid as the eluent. — Separator column Wescan 269-031 eluent 0.01 moI/L nicotinic acid flow rate 2.7 mL/min detection direct conductivity injection volume 100 pL solute concentrations 20 ppm azide, 10 ppm formate and fluoride, 20 ppm orthophosphate, 10 ppm nitrite and chloride, 15 ppm bromate (taken from [70]).

The chromatogram shown in Fig. 3-66, obtained using nicotinic acid as the eluent, serves as an example of the variety of organic adds that can be used as eluents. Nicotinic acid is most suitable for the separation of monovalent anions. In contrast to other monocarboxylic adds, it is characterized by a good water solubility and a low equivalent conductance. In addition, its propensity to adsorb at the stationary phase is very low, which mostly prevents the formation of the usual system peak. However, divalent anions are strongly retained under these chromatographic conditions. For their fast separation, eluents based on salicylic add or trimesic add are more suitable. 

Although only monovalent anions are included in Table 6.8, similar effects are observed with some divalent anions. Salicylic acid will elute sulfate in 5.2 min and thiosulfate in 7.3 min under the conditions in Table 6.7. However, the weaker eluents such as succinic or nicotinic acid require an excessive amount of time to elute divalent anions. 

Table 6.9 lists the relative retention time of the chloride sample anion with the acid eluents chosen for this study. The adjusted retention time of chloride decreases as the retention time for the eluent anion increases and it also decreases as the amount of ionization of the eluent increases. The most satisfactory separations were obtained with either nicotinic acid or succinic acid as the eluent acid. 

Anions of CH-acidic compounds add to pyridinium ions mainly at C-4. Substituents already present on pyridine can bring about interesting reaction sequences. This is exemplified by the formation of the 2,7-naphthyridine derivative 53 from the quaternary salt of the nicotinic acid amide 52 and malonic... 

The order of their effectiveness as photosensitizers for the oxidation of glycyltryptophan in aqueous solution is nicotinic acid > nicotinamide > nicotine-hydroxymethylamide these reactions seems to involve the superoxide radical anion. 

Several new isocyanide complexes of chromium(m) have been prepared by the electrochemical reduction of heavy-metal adducts of chromium(iii) aquocyano-complexes, and characterized by their visible spectra. The chromium 2p- and 3s-orbital ionization potentials in K3[Cr(NCS)6] have been reported, and the lattice parameters for this anion in the salt with diaquotris-(nicotinic acid)holmium(iii) determined. " The absorption spectra of the... 

Nicotinic acid and nicotinamide These are sometimes known by the generic term niacin. Their importance is in combination with tryptophan, as the coenzyme forms nicotinamide adenine dinucleotide (NAD + ) and nicotinamide adenine dinucleotide phosphate (NADP). HPLC is too insensitive to measure endogenous plasma levels, but the urinary metabolites N-methyl-2-pyridone-5-carboxylamide and N -methylnicotinamide can be measured to assess niacin status. Preliminary cleanup of urine by anion-exchange resins is followed by reversed-phase HPLC with UV detection. 

Chromatographic retention times of a number of anions were compared, with 6.0 mM nicotinic acid and 2.0 mM phthalate (pH 6) as the eluents. In many cases, the length of the spacer arm had very little effect on the relative retention times (relative to Cl ). However, the selected data in Table 3.4 show that the relative retention times of bromide, nitrate, chlorate and iodide decreased, while that of sulfate increased slightly. 

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