This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Proteins and Amino Acids, Subject name: Biochemistry
All are tryptophan derivatives except- 
Select and explain. 
A. Melanin, B. Serotonin, C. Melatonin, D. Niacin
A: Melanin
Answer: A: Melanin 
Explanation: Ans. is 'a' i.e., MelaninAmino 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, SerotoninGlycine, Arginine, methionineCreatineGlycine, cysteineBile saltsGlycineHemeAspartic acid and glutaminePyrimidine basesGlycine, aspartic acid, glutaminePurine basesb-alanineCoenzyme-AArginineNitric oxideHistidine, Arginine, lysineKeratinMethionine, lysineCarnitineGABAGlutamateGlutamate, cysteine, glycineGlutathione