Which of the soluble vitamin is synthesized in the body?

Not strictly a Vitamin Can be synthesized from Tryptophan Dietary nicotinamide, niacin and tryptophan (an essential amino acid) contribute to the synthesis of the coenzymes- nicotinamide adenine dinucleotide (NAD+) and nicotinamide adenine dinucleotide phosphate (NADP+) Nicotinamide is deaminated in the body to niacin Tryptophan produces quinolinate which then forms nicotinate mononucleotide and, ultimately, NAD+ and NADP+ Sixty milligrams of tryptophan is equivalent to 1 mg of niacin for the synthesis of niacin coenzymes ref Satyanarayana biochemistry 4th ed page 140