Niacin is synthesized from:
The liver can synthesize niacin from the essential amino acid tryptophan, but the synthesis is extremely inefficient; 60 mg of tryptophan are required to make one milligram of niacin. 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.
Phenylalanine
Tryptophan
Tyrosine
Methionine