Niacin Nicotinamide Nicotinic acid

Nicotinic acid (3-pyridine carboxylic acid or niacin) nicotinamide (nicotinic acid amide), niacinamide, 3-pyridine-carboxylic acid amide Thiamines, hydroxy-ethylthiamine... 

Pharmacology Niacin, vitamin B3, is the common name for nicotinic acid and niacinamide (nicotinamide). Nicotinic acid is present in the body as its active form, nicotinamide (niacinamide). 

Niacm - piTAMINS - NIACINE,NICOTINAMIDEAND NICOTINIC ACID] (Vol 25) - [FEEDS AND FEED ADDITIVES - PET FOODS] (Vol 10) - [FINECHEMICALS - PRODUCTION] (Vol 10) - [FEEDS AND FEED ADDITIVES - RUMINANT FEEDS] (Vol 10) -m dairy substitutes pAIRY SUBSTITUTES] (Vol 7) -m dairy substitutes pAIRY SUBSTITUTES] (Vol 7) -deficiency of piTAMINS - NIACINE,NICOTINAMIDEAND NICOTINIC ACID] (Vol 25) -dietary requirements piTAMINS - NIACINE, NICOTINAMIDE AND NICOTINIC ACID] (Vol 25) -m nuts PUTS] (Vol 17) -m nuts PUTS] (Vol 17)... 

Several of the B vitamins function as coenzymes or as precursors of coenzymes some of these have been mentioned previously. Nicotinamide adenine dinucleotide (NAD) which, in conjunction with the enzyme alcohol dehydrogenase, oxidizes ethanol to ethanal (Section 15-6C), also is the oxidant in the citric acid cycle (Section 20-10B). The precursor to NAD is the B vitamin, niacin or nicotinic acid (Section 23-2). Riboflavin (vitamin B2) is a precursor of flavin adenine nucleotide FAD, a coenzyme in redox processes rather like NAD (Section 15-6C). Another example of a coenzyme is pyri-doxal (vitamin B6), mentioned in connection with the deamination and decarboxylation of amino acids (Section 25-5C). Yet another is coenzyme A (CoASH), which is essential for metabolism and biosynthesis (Sections 18-8F, 20-10B, and 30-5A). 

Humans can convert ingested tryptophan to niacin in vivo (19,93,96). Therefore, the niacin activity of food can be expressed in niacin equivalents, which is the sum of the niacin content (nicotinic acid vitamers + nicotinamide vitamers) plus 1/60 of the tryptophan content (in mg). This section will be restricted to analyses for the niacin vitamers. Tryptophan methodology will not be covered. 

The physiologically active forms of niacin are nicotinic acid, nicotinamide, and their coenzymes (93,96). Niacytin and the niacynogens appear to have limited bioavailability, although more work is needed in this area. The absorption and metabolism of niacin has been reviewed (20,93). 

In the first stage of respiration, a six-carbon glucose molecule is split into a pair of three-carbon molecules. Hydrogen Ions and electrons also are produced in glycolysis. These combine with electron carrier ions called nicotinamide adenine dinucleotide (NAD+) to form NADH. NADH is a coenzyme that is made from vitamin B4, which is also called niacin or nicotinic acid. ATP and NADH serve as temporary storage sites for energy and electrons, respectively, during respiration. Two molecules of ATP are used, and four molecules are produced. ... 

The history of nicotinic acid (niacin) began in 1867, when it was first synthesized by oxidation of nicotine. The name niacin was derived later from the words n/cotinic acid and vitam/n in an effort to avoid confusing nicotinic acid and nicotinamide with nicotine. Although the terms niacin" and nicotinic acid" are today used interchangeably, only the more chemically descriptive term, nicotinic acid," will be used in the following discussions. 

Figure 3.8. Structures of vitamins or vitamin-derived molecules that function in oxidation-reduction reactions. The oxidation of these redox groups in the inner mitochondricil membrane contributes to the electron transport chain that carries electrons from the oxidation of glucose to oxygen and in the process pumps protons from one side to the other of the inner mitochondrial membrane (see Chapter 8 for details). The proton gradient thus formed is used to phosphorylate ADP to form 32 of the 36 ATPs resulting from the oxidation of one glucose molecule to six CO2 and six H2O molecules. A Vitamin B3, also called niacin or nicotinic acid, becomes converted to the amide (nicotinamide) and dressed up with a ribose sugar. Then, in a manner like that of riboflavin in B becomes phosphorylated to form nicotinamide mononucleotide (NMN) or further reacted with the addition of adenosine monophosphate (AMP) to form nicotinamide adenine dinucleotide (NAD). B Vitamin B2, also known as riboflavin, is shown converted to the forms involved in redox reactions such as those of the electron transport chain. (From Biochemistry, Second Edition, D. Voet and J. Voet, Copyright 1995, John Wiley Sons, New York. Reprinted with permission of John Wiley Sons, Inc.)...

Vitamin B3 Vitamin B3 (niacin) has different physiologically active forms, nicotinic acid, nicotinamide, and their coenzymes, which are very stable at ambient temperature. Usually acid or alkaline hydrolysis are used to convert nicotinamide to nicotinic acid for quantitation of both vitamers as nicotinic acid the first treatment (acid) is used to quantitate biologically available niacin, while alkaline hydrolysis provides an estimate of the total niacin content. Nicotinic acid has been analyzed using ion exchange or RP chromatography with amino columns. Detection is performed with UV absorbance at 254 nm. 

Rgure 8 Niacin (A) nicotinic acid, (B) nicotinamide, (C) nicotinamide adenine dinucleotidephosphate. 

Two compounds, nicotinic acid and nicotinamide, have the biological activity of niacin. When nicotinic acid was discovered to be a curative and preventive factor for pellagra, it was already known as a chemical compound, and was therefore never assigned a number among the B vitamins. The name niacin was coined in the USA when it was decided to enrich maize meal with the vitamin to prevent pellagra - it was considered that the name nicotinic acid was not desirable because of the similarity to nicotine. In USA, the term niacin is commonly used to mean specifically nicotinic acid, and nicotinamide is known as niacinamide elsewhere niacin is used as a generic descriptor for both vitamers. Figure 2.16 shows the structures of nicotinic acid, niacin and the nicotinamide nucleotide coenzymes, NAD and NADE... 

Niacin refers to a group of compoimds also known as vitamin B3, presenting similar biological activity, including nicotinamide, nicotinic acid, as well as other pyridine nucleotide structures. In the body, these compounds act as cofactors in oxidation—reduction reactions. To determine the total vitamin B3 content, either an acid or alkaline hydrolysis is necessary. The separation is normally performed by RPLC with fluorescence (322 nm ex., 380 nm em.) or UV detection (254 nm). 

Persons suffering from severe forms of the disease may be given either nicotinamide (a derivative of niacin) or nicotinic acid in oral doses as high as 100 mg every 4 hours. Such high doses of nicotinic acid often cause flushing, which does not result when similar doses of nicotinamide are given. 

Niacin includes two vitamers, nicotinic acid and nicotinamide. Nicotinic acid is pyridine 3-carboxylic acid. It is slightly soluble in water and alcohol and easily soluble in alkalis, but is insoluble in both acetone and diethyl-ether. Nicotinamide is the active form, which functions as a constiment of two coenzymes nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP). In animal tissues, the reduced stages of these coenzymes have been found as the principal forms of niacin. Nicotinamide is very soluble in water, easily soluble in alcohol, soluble in glycerol, and slightly soluble in ether. 

Vitamin B3. See Vitamins, Niacin, Nicotinamide, and Nicotinic acid. 

Niacin, nicotinamide, and nicotinic acid. Pantothenic acid,... 

Both nicotinic acid and nicotinamide have been assayed by chemical and biological methods. Owing to the fact that niacin is found in many different forms in nature, it is important to indicate the specific analyte in question. For example, if biological assay procedures are used, it is necessary to indicate whether the analysis is to determine the quantity of nicotinic acid or if niacin activity is the desired result of the analysis. If nicotinic acid is desired, then a method specific for nicotinic acid should be used. If quantitation of niacin activity is the desired outcome, then all compounds (bound and unbound) which behave like niacin will assay biologically for this substance (1). 

Niacin (nicotinic acid) Nicotinamide adenine dinncleotide (NAD )... 

Niacin (Fig. 1) is a collective name for all vitamers having the biological activity associated with nicotinamide (= pyridine-3-carboxamide), including nicotinic acid (= pyridine-3-carboxylic acid) and a variety of pyridine nucleotide structures. 

Most foods of animal origin contain nicotinamide in the coenzyme form (high bioavialability). Liver and meat are particularly rich in highly bioavailable niacin. Most of the niacin in plants, however, occurs as nicotinic acid in overall lower concentrations and with a lower bioavailability. The major portion of niacin in cereals is found in the outer layer and its bioavailability is as low as 30% because it is bound to protein (niacytin). If the diet contains a surplus of L-tryptophan (Ttp), e.g., more than is necessary for protein synthesis, the liver can synthesize NAD from Trp. Niacin requirements are therefore declared as niacin equivalents (1 NE = 1 mg niacin = 60 mg Trp). 

Niacin. Figure 1 Structure of nicotinic acid and nicotinamide. 

Niacin Nicotinic acid, nicotinamide Coenzyme in oxidation and reduction reactions, functional part of NAD and NADP Pellagra—photosensitive dermatitis, depressive psychosis... 

Niacin was discovered as a nutrient during studies of pellagra. It is not strictly a vitamin since it can be synthesized in the body from the essential amino acid tryptophan. Two compounds, nicotinic acid and nicotinamide, have the biologic activity of niacin its metabolic function is as the nicotinamide ring of the coenzymes NAD and NADP in oxidation-reduction reactions (Figure 45-11). About 60 mg of tryptophan is equivalent to 1 mg of dietary niacin. The niacin content of foods is expressed as mg niacin equivalents = mg preformed niacin + 1/60 X mg tryptophan. Because most of the niacin in cereals is biologically unavailable, this is discounted. 

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