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Xanthine

About: Xanthine is a research topic. Over the lifetime, 4046 publications have been published within this topic receiving 129820 citations. The topic is also known as: Xanthine.


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Book ChapterDOI
01 Jan 1940
TL;DR: The hydroxy and amino purines are derived chiefly from the nucleoproteins of the diet, although there is evidence that the organism can synthesize the purine ring from the amino acid histidine.
Abstract: This chapter describes the sources and derivatives of purines and pyrimidines. The biological purines are simple hydroxy, amino, or methyl derivatives of a parent purine ring, which does not occur free in nature. Hydroxy purines, hypoxanthine, and xanthine occur in tissues and tissue fluids of many animals, and uric acid, a trihydroxy purine, is the chief nitrogenous excretory product of birds and snakes, and is invariably present in mammalian urine. Amino purines, represented by adenine and guanine, are components of nucleic acid and the nucleosides. Methyl purines are the characteristic alkaloids of tea, coffee, and cocoa. The hydroxy and amino purines are derived chiefly from the nucleoproteins of the diet, although there is evidence that the organism can synthesize the purine ring from the amino acid histidine. Nucleoproteins are compound proteins, the nonprotein being nucleic acid, which is liberated during alimentary digestion. Nucleic acid is composed of four nucleotide units, each of which is a phosphoric ester of a nucleoside or compound of sugar and a nucleo purine or a pyrimidine.

138 citations

Journal ArticleDOI
TL;DR: The results indicate that the nutritional significance of free dietary adenine versus nucleic acid-boundAdenine in yeast or yeast nucleic Acid is an important consideration in evaluating the suitability of single cell proteins in fish feed formulations.

137 citations

Journal ArticleDOI
TL;DR: The results suggest that, in coffee plants, caffeine is synthesized through three independent methylation steps from xanthosine, in which CaMXMT catalyzes the second step to produce theobromine.

137 citations

Journal ArticleDOI
TL;DR: It is demonstrated that changes in the amount of StUCP can alter the rate of proton conductance of potato mitochondria, and suggests that superoxide and linoleic acid stimulate a proton leak in potatoes mitochondria that is related to the activity of uncoupling protein.

137 citations

Journal ArticleDOI
TL;DR: The tested infusion mainly exhibited a potent scavenging effect on superoxide radicals (although a noncompetitive inhibitory effect on xanthine oxidase was also observed), and acted as a moderate scavenger of hydroxyl radicals and hypochlorous acid.
Abstract: Hypericum androsaemum is a medicinal plant species containing many polyphenolic compounds, namely flavonoids and phenolic acids. Since polyphenolic compounds have high antioxidant potential, the ability of H. androsaemum infusion to act as a scavenger of reactive oxygen species (superoxide radical, hydroxyl radical and hypochlorous acid) was investigated. Superoxide radical was generated by the xanthine/xanthine oxidase and phenazine methosulphate/NADH systems. The infusion-mediated prevention of nitroblue tetrazolium reduction by the superoxide radical was used as the measured endpoint. Hydroxyl radical was generated by the Fe3+-EDTA/ascorbate Fenton system, and assayed by evaluating deoxyribose degradation using the thiobarbituric acid method. Hypochlorous acid scavenging activity was tested by measuring the inhibition of hypochlorous acid-induced 5-thio-2-nitrobenzoic acid oxidation to 5,5′-dithiobis(2-nitrobenzoic acid). The tested infusion mainly exhibited a potent scavenging effect on superoxide radicals (although a noncompetitive inhibitory effect on xanthine oxidase was also observed). The infusion also acted as a moderate scavenger of hydroxyl radicals and hypochlorous acid. A phytochemical study of the infusion was also undertaken, and nine phenolic compounds were identified.

137 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202361
2022108
202157
202060
201961
201869