| 释义 |
xanthine Chem.|ˈzænθaɪn|
Also -in.
[ad. F. xanthine, f. Gr. ξανθός yellow: see -ine5.]
1. a. A substance (C5H4N4O2) allied to uric acid, found in various organs and secretions of the animal body; originally called xanthic oxide (see xanthic 1 a), from its forming a lemon-yellow compound with nitric acid.
1857G. Bird Urin. Deposits (ed. 5) 46 This interesting body..bears so close a resemblance to xanthine or uric oxide, that Scherer has named it hypoxanthine. 1862H. Bence Jones in Jrnl. Chem. Soc. XV. 78 (heading) On a Deposit of Crystallized Xanthin in Human Urine. 1880J. W. Legg Bile 582 The liver contained..leucin, tyrosin, and xanthin. 1887A. M. Brown Anim. Alkaloids 78 Xanthine may be extracted from muscular tissue in the same way as the sarkine.
attrib. and Comb.1868Watts Dict. Chem. V. 1050 Xanthine..was discovered by Marcet in a urinary calculus weighing only 8 grains. Liebig and Wöhler afterwards found it in a larger calculus weighing between 18 and 20 grammes; these are the only known examples of xanthine calculi. 1873C. H. Ralfe Phys. Chem. 93 Dr. Bence Jones has recorded an interesting case of xanthin gravel occurring in a lad aged nine and a half years. 1883Science 23 Feb. 75/1 By heating xanthine-silver [= the silver-compound of xanthine] with methyl iodide, a methyl group was introduced. 1897Trans. Amer. Pediatric Soc. IX. 123 Convulsive seizures,..produced by the action of the poisonous xanthin bodies on the nerve centres. 1907Sat. Rev. 16 Mar. 338/1 So called food reformers..bandy about their catchwords—flesh-forming,..xanthin-forming and the like.
b. Any of several substituted derivatives of xanthine.
1956I. Finar Org. Chem. II. xvi. 613 Three important methylated xanthines that occur naturally are caffeine, theobromine and theophylline. 1974M. C. Gerald Pharmacol. xv. 280 The xanthines..have proved to be valuable drugs for the treatment of such respiratory diseases as asthma, bronchitis, and emphysema.
2. xanthine oxidase, an enzyme catalysing the oxidation of hypoxanthine to xanthine and of xanthine to uric acid.
1905Jrnl. Chem. Soc. LXXXVIII. ii. 271 The presence of oxygen is necessary to obtain in liver extract uric acid from the purine bases it contains, or that are added to it. The uric acid found comes almost exclusively from xanthine, and is due to a ferment, xanthine-oxydase. 1983Oxf. Textbk. Med. I. ix. 79/1 Not all patients with xanthine stones have xanthine oxidase deficiency.
Hence ˈxanthinine, ‖ xanthiˈnuria (see quots.).
1868Watts Dict. Chem. V. 1051 Xanthinine. C4H3N3O2... A base produced..by heating thionurate of ammonium to 200°... On boiling the resulting mass with water, the xanthinine remains as a yellow powder. 1890Billings Nat. Med. Dict., Xanthinuria, passage of xanthin in the urine. |