Nicotinamide Niacin

Pyridine-3-carboxamide (nicotinamide, niacin), mp 130°C, is commercially produced by ammoxi-dation of 3-picoline, followed by partial hydrolysis of the intermediate 3-cyanopyridine ... 

Rosenkrantz (1957) has published a review of the spectra of vitamins, hormones, and coenzymes in the solid state. Among the spectra of vitamins were those of vitamin A and its acetate, vitamin D2, a-tocopherol, menadione (the common substitute for vitamin K), thiamine hydrochloride, nicotinamide, niacin, riboflavin. 

Nicotinamide Niacin Pellagra NADandNADP Hydrogen carrier Can be synthesized from... 

Niacin, also formerly known as PP factor (Pellagra Preventive factor) or vitamin PP is a common name for nicotinic acid (pyridine-3-carboxyHc acid, 5-63) and its amide nicotinamide (niacin amide, also formerly known as vitamin Bj, 5-64). Both compounds have the same biological activity. 

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). 

U.S. manufacturers of niacin and niacinamide include Nepera, Inc. and Reilly Industries, Inc. U.S. suppliers include BASF Corporation, Hoffmann-La Roche Inc., and Rhc ne-Poulenc. Western European producers and suppHers include Degussa, Rhc ne-Poulenc, BASF, Hoffmann-La Roche, and Lon2a (71). In 1995, the prices for niacin and nicotinamide were 9.75/kg and 9.25/kg, respectively (72,73). 

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. Figure 2 Structure of the coenzymes NAD+ (nicotinamide-adenine dinucleotid) and NADP+ (nicotinamide-adenine dinucleotid phosphate). 

These dehydrogenases use nicotinamide adenine dinucleotide (NAD ) or nicotinamide adenine dinucleotide phosphate (NADP )—or both—and are formed in the body from the vitamin niacin (Chapter 45). The coenzymes are reduced by the specific substrate of the dehydrogenase and reoxidized by a suitable electron acceptor (Figure 11-4). They may freely and reversibly dissociate from their respective apoenzymes. 

Four of the B vitamins are essential in the citric acid cycle and therefore in energy-yielding metabolism (1) riboflavin, in the form of flavin adenine dinucleotide (FAD), a cofactor in the a-ketoglutarate dehydrogenase complex and in succinate dehydrogenase (2) niacin, in the form of nicotinamide adenine dinucleotide (NAD),... 

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. 

Figure 45-11. Niacin (nicotinic acid and nicotinamide) and nicotinamide adenine dinucieotide (NAD). Shows the site of phosphoryiation in NADP.

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