Topic
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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39 citations
TL;DR: This study provides a rational basis for the use of C. aurantium dried immature fruits against hyperuricemia and identifies hesperetin as more potent inhibitory activity against xanthine oxidase.
Abstract: Xanthine oxidase is a key enzyme which can catalyze hypoxanthine and xanthine to uric acid causing hyperuricemia in humans. Xanthine oxidase inhibitory activities of 24 organic extracts of four species belonging to Citrus genus of the family Rutaceae were assayed in vitro. Since the ethyl acetate extract of C. aurantium dried immature fruits showed the highest xanthine oxidase inhibitory activity, chemical evidence for the potent inhibitory activity was clarified on the basis of structure identification of the active constituents. Five flavanones and two polymethoxyflavones were isolated and evaluated for inhibitory activity against xanthine oxidase in vitro. Of the compounds, hesperetin showed more potent inhibitory activity with an IC50 value of 16.48 μM. For the first time, this study provides a rational basis for the use of C. aurantium dried immature fruits against hyperuricemia.
39 citations
TL;DR: Methyluric acids were formed from the oxidation of theobromine, paraxanthine and 7-methylxanthine, although no bacterialgrowth was observed on these compounds, indicating that this might be due to a widesubstrate specificity of xanthine oxidase.
Abstract: Caffeine catabolism and a xanthine oxidase involved in the alkaloid breakdown werestudied in Pseudomonas putida L, a strain displaying high ability to grow on this substrate.Cells cultured with unlabelled caffeine and 14 C labeled caffeine and xanthine showed thatthis alkaloid was broken-down via theobromine/paraxanthine -> 7-methylxanthine ->xanthine -> uric acid -> allantoin -> allantoic acid. Methyluric acids were formed fromthe oxidation of theobromine, paraxanthine and 7-methylxanthine, although no bacterialgrowth was observed on these compounds, indicating that this might be due to a widesubstrate specificity of xanthine oxidase. This was confirmed by activity staining in PAGEwhere activity was observed with theophylline and 3-methylxanthine, which are notinvolved in the alkaloid breakdown. A single band of activity was detected without additionof NAD + , showing an oxidase form of the enzyme. The enzyme optimum temperatureand pH were 30 o C and 7.0, respectively. The determined K
39 citations
TL;DR: In this article, the conditions required for hydroxyl radical generation during the oxidation of xanthine by xan- thine oxidase were evaluated, and it was shown that the presence of adventitious iron was a contributing factor.
39 citations
TL;DR: Repair of DNA lesions induced by oxygen radicals, generated by xanthine/xanthine oxidase (X/XO), was studied in human peripheral blood lymphocytes and in PHA-stimulated proliferating lymphocytes from 4 healthy subjects to support the view that there are differences between the DNA damage due to oxygen radicals and that due to ionizing radiation.
Abstract: Repair of DNA lesions induced by oxygen radicals, generated by xanthine/xanthine oxidase (X/XO), was studied in human peripheral blood lymphocytes and in PHA-stimulated proliferating lymphocytes from 4 healthy subjects. The lesions included DNA-strand breaks (SSB) and other lesions that are converted to SSB under alkaline conditions. The frequencies of SSB were estimated by fluorometric analysis of DNA unwinding. Maximum production of SSB occurred within 10 min of incubation with X/XO at 22°C; with 0.5 mM or higher concentrations of xanthine; and with 0.1–0.5 units/ml of xanthine oxidase. Proliferating lymphocytes repaired X/XO-induced SSB about 4 times more rapidly than lymphocytes. Lymphocytes repaired X/XO-induced SSB more slowly than SSB caused by γ-radiation. These findings are consistent with the evidence that a number of DNA-repair enzymes have greater activity in proliferating cells than in resting cells. These findings also support the view that there are differences between the DNA damage due to oxygen radicals and that due to ionizing radiation.
39 citations