What is a complex nitrogenous substance related to urea and uric acid, produced as a white powder; -- so called because it forms yellow salts, and because its solution forms a blue fluorescence like quinine called?

xanthinine — A complex nitrogenous substance related to urea and uric acid, produced as a white powder; -- so called because it forms yellow salts, and because its solution forms a blue fluorescence like quinine. (Webster's 1913.)

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