This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Biochemistry
[{'content': 'Melatonin is derived from \nSelect and explain. \nA. Tyrosine, B. Tryptophan, C. Glutathione, D. None', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Tryptophan is first hydroxylated by tryptophan Hydroxylase 5-hydroxytryptophan is decarboxylated to serotoninSerotonin is acetylated Fuher methylated with the help of S adenosylmethionine (SAM)Ref: DM Vasudevan, 7th edition, page no: 241, fig 18.10', 'role': 'assistant'}]