Formation of Niacin
Niacin is pyridine 3-carboxylic acid. Nicotinamide or niacinamide is the amide of nicotinic acid.
It derives its name from nicotine, from which it can be prepared by oxidation.
In tissues, it is present as nicotinamide which is the physiologically active form.
Nicotinamide, the active component in NAD+ and NADP+.
Niacin is synthesised in the body from tryptophan, an essential amino acid. Administration of tryptophan or proteins rich in tryptophan is followed by increased excretion of niacin metabolites. Diets deficient in tryptophan produce a deficiency of niacin in the body.
The following scheme has been proposed by Hayaishi and others for the conversion of tryptophan into niacin in liver.