xanthine noun. ['zanƟʌɪn] Also xanthin [-ɪn]. See also prec. M19.
[from XANTHIC + -INE⁵.]
Biochemistry. A crystalline purine, C₅H₄N₄O₂, found in blood and urine and in some plants, which is an intermediate in the breakdown of nucleic acids to uric acid and is the parent compound of caffeine and related alkaloids. Also, any of several substituted derivatives of this.

Comb.:
xanthine oxidase an enzyme containing molybdenum which catalyses the oxidation of hypoxanthine to xanthine and of xanthine to uric acid.

■ xanthi'nuria noun (Medicine) the presence of abnormally large amounts of xanthine in the urine L19.

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