Nicotinamide/ja: Difference between revisions

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== Side effects ==

Niacinamide has minimal side effects. At very high doses above 3g/ day acute [[liver toxicity]] has been documented in at least one case. Normal doses are safe during [[pregnancy]].

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== Chemistry ==

The structure of nicotinamide consists of a [[pyridine]] ring to which a [[primary amide]] group is attached in the [[arene substitution pattern|''meta'']] position. It is an [[amide]] of [[nicotinic acid]]. As an [[aromatic compound]], it undergoes [[electrophilic aromatic substitution|electrophilic substitution]] reactions and transformations of its two [[functional group]]s. Examples of these reactions reported in ''[[Organic Syntheses]]'' include the preparation of [[2-chloronicotinonitrile]] by a two-step process via the [[N-oxide|''N''-oxide]],

from [[nicotinonitrile]] by reaction with [[phosphorus pentoxide]], and from [[3-aminopyridine]] by reaction with a solution of [[sodium hypobromite]], prepared ''in situ'' from [[bromine]] and [[sodium hydroxide]].

[[File:Nicotinamide highlighted in NAD+.svg|thumb|right|NAD⁺, the oxidized form of [[nicotinamide adenine dinucleotide|NADH]], contains the nicotinamide [[moiety (chemistry)|moiety]] (highlighted in red)]]

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===Industrial production===

The hydrolysis of [[nicotinonitrile]] is catalysed by the enzyme [[nitrile hydratase]] from ''[[Rhodococcus rhodochrous]]'' J1, producing 3500 tons per annum of nicotinamide for use in animal feed. The enzyme allows for a more selective synthesis as further hydrolysis of the amide to [[nicotinic acid]] is avoided. Nicotinamide can also be made from nicotinic acid. According to ''[[Ullmann's Encyclopedia of Industrial Chemistry]]'', worldwide 31,000 tons of nicotinamide were sold in 2014.

=== Biochemistry ===

[[File:NAD+ Oxidation and Reduction.png|thumb|upright=1.3|The active Nicotinamide group on the molecule NAD⁺ undergoes oxidation in many metabolic pathways.]]

Nicotinamide, as a part of the cofactor [[nicotinamide adenine dinucleotide]] (NADH / NAD⁺) is crucial to life. In cells, nicotinamide is incorporated into NAD⁺ and [[nicotinamide adenine dinucleotide phosphate]] (NADP⁺). NAD⁺ and NADP⁺ are [[Cofactor (biochemistry)|cofactor]]s in a wide variety of enzymatic [[redox|oxidation-reduction]] reactions, most notably [[glycolysis]], the [[citric acid cycle]], and the [[electron transport chain]]. If humans ingest nicotinamide, it will likely undergo a series of reactions that transform it into NAD, which can then undergo a transformation to form NADP⁺. This method of creation of NAD⁺ is called a [[Salvage Pathway|salvage pathway]]. However, the human body can produce NAD⁺ from the amino acid [[tryptophan]] and niacin without our ingestion of nicotinamide.

NAD⁺ acts as an electron carrier that mediates the interconversion of energy between nutrients and the cell's energy currency, [[adenosine triphosphate]] (ATP). In oxidation-reduction reactions, the active part of the cofactor is the nicotinamide. In NAD⁺, the nitrogen in the aromatic nicotinamide ring is covalently bonded to adenine dinucleotide. The formal charge on the nitrogen is stabilized by the shared electrons of the other carbon atoms in the aromatic ring. When a hydride atom is added onto NAD⁺ to form NADH, the molecule loses its aromaticity, and therefore a good amount of stability. This higher energy product later releases its energy with the release of a hydride, and in the case of the electron transport chain, it assists in forming [[adenosine triphosphate]].

When one mole of NADH is oxidized, 158.2{{nbsp}}kJ of energy will be released.

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=== Biological role ===

Nicotinamide occurs as a component of a variety of biological systems, including within the [[vitamin B]] family and specifically the [[vitamin B3 complex|vitamin B₃ complex]]. It is also a critically important part of the structures of [[nicotinamide adenine dinucleotide|NADH and NAD⁺]], where the ''N''-substituted aromatic ring in the oxidised NAD⁺ form undergoes reduction with hydride attack to form NADH. The [[Nicotinamide adenine dinucleotide phosphate|NADPH/NADP⁺]] structures have the same ring, and are involved in similar biochemical reactions.

Nicotinamide can be methylated in the liver to biologically active [[1-Methylnicotinamide]] when there are sufficient methyl donors.

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== Food sources ==

Niacinamide occurs in trace amounts mainly in meat, fish, nuts, and mushrooms, as well as to a lesser extent in some vegetables. It is commonly added to cereals and other foods. Many multivitamins contain 20–30{{nbsp}}mg of vitamin B₃ and it is also available in higher doses.