The following metabolite is a derivative of tryptophan-

Ans. is 'a' i.e., Melatonin Amino acidsBiological important compoundTyrosineCatecholamines (epinephrineQ, norepinephrineQ, dopamineQ), thyroxineQ, triiodothryonine, melanin Q.(Note: - Phenylalanine is the precursor of tyrosine, thus it can also give rise to all these compounds through tyrosine (phenylalanine - TyrosineQ - CatecholaminesQ, thyroxineQ, T3, melaninQ).TryptophanVitamin niacinQ, melatoninQ, SerotoninQGlycineQ,ArginineQ,methionineQCreatineQGlycine, cysteineBile saltsGlycineHeme.Aspartic acid andglutaminePyrimidine basesGlycineQ,aspartic acid,glutaminePurine basesQb-alanineCoenzyme-AArginineNitric oxideQGlutamateGama-amino butyric acid (GABA)