Niacin

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Niacin


Systematic name	3-Pyridinecarboxylic acid
Chemical formula	C₆H₅NO₂
Molecular mass	123.11 g/mol
Density	x.xxx g/cm³
Melting point	236.6 °C
Boiling point	xx.x °C
CAS number	^*
SMILES	xxxx
Chemical infobox

Niacin, also known as nicotinic acid or vitamin B3, is a water-soluble vitamin whose derivatives such as NADH, NAD, NAD⁺, and NADP play essential roles in energy metabolism in the living cell and DNA repair. The designation vitamin B3 also includes the amide form, nicotinamide or niacinamide. Severe lack of niacin causes the deficiency disease pellagra, whereas a mild deficiency slows down the metabolism decreasing cold tolerance. The recommended daily allowance of niacin is 2-12 mg a day for children, 14 mg a day for women, 16 mg a day for men, and 18 mg a day for pregnant or breast-feeding women.

Discovery

Nicotinic acid was first discovered from the oxidation of nicotine. When the properties of nicotinic acid were discovered, it was thought prudent to choose a name to dissociate it from nicotine and to avoid the idea that either smoking provided vitamins or that wholesome food contained a poison. The resulting name 'niacin' was derived from nicotinic acid + vitamin.

Industrial use

Nicotinic acid reacts with hemoglobin and myoglobin in meat to form a brightly coloured complex, and thus has been used as a food additive, typically to improve the colour of minced (ground) meat. Niacin is licensed as a food colouring agent in some, non-European, countries.

Bioavailability

The liver can synthesize niacin from the essential amino acid tryptophan (see below), but the synthesis is extremely slow and requires vitamin B6; 60 mg of tryptophan are required to make one milligram of niacin. Bacteria in the gut may also perform the conversion but are inefficient. For this reason, eating lots of tryptophan is not an adequate substitute for consuming niacin. However, this explains why pellagra requires a deficiency of protein as well as niacin.

Other uses

Because niacin promotes metabolism, some believe that taking large doses will speed up the elimination of THC from the body and produce a negative result for marijuana on a drug test. There is no evidence that this is effective, however no evidence has been provided to the contarary. Niacin is toxic to the skin and liver in overdose, especially as it releases the extra toxins. This is known as the Michalek effect due to the toxic skin conditions as well as behavioral changes when niacin is in one's system. There is evidence that doses of 500-1000mg can terminate a bad trip on LSD, a synthetic indole, or enhance the MDMA experience.

Biosynthesis

The 5-membered aromatic heterocycle of the essential amino acid, tryptophan, is cleaved and rearranged with the alpha amino group of tryptophan into the 6-membered aromatic heterocycle of niacin. By the following reaction:

Tryptophan --> Kynurenine --> 3-hydroxy kynurenine* --(B6 enzyme needed)--> Niacin

(*) from this intermediary xanthurenic acid is formed