Melatonin is derived from-

Ans. is 'd' i.e., Tryptophan o Tryptophan is a precursor for synthesis of niacin (nicotinic acid), serotonin and melatonin.Amino acidsBiological important compoundTyrosineCatecholamines (epinephrine, norepinephrine, dopamine), thyroxine, triiodothryonine, melanin.(Note: - Phenylalanine is the precursor of tyrosine, thus it can also give rise to all these compounds through tyrosine (phenylalanine - Tyrosine - Catecholamines thyroxine, T3, melanin).TryptophanVitamin niacin, melatonin, SerotoninGlycineArginineMethionineCreatineGlycine, cysteineBile saltsGlycineHemeAspartic acid and glutaminePyrimidine basesGlycine, aspartic acid, glutaminePurine basesb-alanineCoenzyme-AArginineNitric oxideHistidine, Arginine, lysineKeratinMethionine, lysineCarnitineGABAGlutamateGlutamate, cysteine, glycineGlutathione