This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
[{'content': 'First product of purine metabolism \nSelect and explain. \nA. Uric acid, B. Xanthine, C. P-alanine, D. CO2', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Humans catabolize purines to uric acid. But, first purines are catabolized to xanthine, which is fuher catabolized to purine.', 'role': 'assistant'}]