Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.17.3.2 (xanthine oxidase)
 8,383 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Previously, it has been shown that pteridine derivatives are capable of modulating the action of free radicals and both prooxidant and antioxidant properties have been described. However, the mechanism of manifestation of these properties is still unclear. We studied the radical scavenging properties of 7,8-dihydroneopterin and neopterin using the spin trap 5,5-dimethyl-1-pyrroline-1-oxide (DMPO). It was found that dihydroneopterin acts generally as a radical scavenger. In the presence of dihydroneopterin the ESR signal was reduced by 30 to 90% compared to the control signal. The rate constants for the reactions of 7,8-dihydroneopterin with superoxide (10(3) M(-1) s(-1)) and peroxyl radicals (10(7) M(-1) s(-1)) were determined. Neopterin in contrast showed no reduction of the ESR signal except with superoxide radicals produced by xanthine oxidase. However, this effect was shown to be due to an inhibition of enzyme rather than to radical scavenging. Our results provide a basis for understanding previous observations of radical scavenger activity of 7,8-dihydroneopterin.
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PMID:Spin trapping study of antioxidant properties of neopterin and 7,8-dihydroneopterin. 917 92

The addition of DL-alpha-tocopherol (vitamin E) at the time of UV irradiation only marginally protects cells from UV-induced cytotoxicity. However, a protective effect of alpha-tocopherol emerged when it was added to the cells before UV irradiation, alpha-Tocopherol was progressively and dose-dependently incorporated into the cells. Washout experiments showed that the intracellular concentration of alpha-tocopherol decreased with an approximate half-life of 14-20 hours, due to the release from the cells and dilution by cell proliferation. Pretreatment of the cells with alpha-tocopherol significantly increased the resistancy against the cytotoxic action of UV irradiation and antioxidants such as sodium ascorbate, gallic acid, n-propyl gallate and caffeic acid. ESR spectroscopy showed that alpha-tocopherol enhanced the ascorbyl radical intensity, whereas it reduced caffeic acid radical intensity, without affecting the radical intensity of gallic acid and n-propyl gallate. Both control and treated cell lysates scavenged superoxide anion (generated by xanthine-xanthine oxidase reaction) and hydroxyl radical (generated by Fenton reaction) to a comparable extent. The present study suggests that the protective effect of alpha-tocopherol might be derived from its incorporation into the cell membranes rather than its scavenging activity.
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PMID:Effect of alpha-tocopherol on cytotoxicity induced by UV irradiation and antioxidants. 921 67

The radical modulating activity of 2-methoxy-4-(2-propenyl)phenol (eugenol), 2-t-butyl-4-methoxy-phenol (BHA), and their dimers (bis-eugenol, bis-BHA) was investigated, using ESR spectroscopy. Eugenol produced radicals in alkaline solutions, and enhanced the radical intensity of both sodium-L-ascorbate and sodium 5,6-benzylidene-L-ascorbate. BHA has similar, but slightly lower activity, and their dimers were inactive. Their ability to scavenge the superoxide anion (O2-), generated by hypoxanthine and xanthine oxidase reaction, was in the order of eugenol > bis-eugenol > BHA > bis-BHA. The relative radical intensity among these compounds was paralleled by their cytotoxic activity. The present study demonstrates that eugenol and BHA were very reactive with radicals and their reactivity was considerably reduced by dimerization. The applicability of the dimerized eugenol in dentistry was discussed.
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PMID:Interaction between eugenol-related compounds and radicals. 956 13

The effect of hot water and alkaline extracts of Acer nikoense Maxim. on the radical intensity of sodium ascorbate, superoxide anion (O2-)(produced by hypoxanthine-xanthine oxidase reaction) and hydroxyl radical (-OH)(generated by Fenton reaction) was investigated using ESR spectroscopy. All these extracts produced radical(s) under alkaline conditions and enhanced the radical intensity of sodium ascorbate. Among these fractions, Fr. I showed the highest stimulation effect, which coincided with its higher degradation rate and capacity to enhance the cytotoxic activity of ascorbate. These fractions also dose-dependently reduced the radical intensity of O2- and -OH. The present study demonstrates that Acer nikoense Maxim. extracts potentiate both radical intensity and apoptosis-inducing activity of ascorbate.
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PMID:Radical scavenging activity of Acer nikoense Maxim. extract. 961 28

The radical modulation activity of hot water and NaOH extracts of the thorn apple of Crataegus Cuneata Sieb. et. Zucc. was investigated, using ESR spectroscopy. The radical intensity of sodium ascorbate was slightly reduced at lower concentrations of the extracts, but it was synergistically enhanced at higher concentrations. Higher concentrations of the extracts also synergistically stimulated the cytotoxic action of sodium ascorbate against human oral squamous carcinoma and salivary gland tumor cell lines. All these extracts effectively scavenged superoxide anion and hydroxyl radical, produced by hypoxanthine-xanthine oxidase and Fenton reaction, respectively, and their activity was comparable with that of lignins prepared by the same procedure from other plants. These data further supports the medicinal efficacy of plant extracts.
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PMID:Enhancement of radical intensity and cytotoxic activity of ascorbate by Crataegus cuneata Sieb et. Zucc. extracts. 970 40

The radical modulation activity of hot water and alkaline extracts from leaf of Ceriops decandra, a mangrove plant, was investigated using ESR spectroscopy. IR and NMR analyses demonstrate that the leaf extracts have a lignin-like polyphenolic structure. All these extracts produced radical(s) under alkaline conditions. The radical intensity of sodium ascorbate was slightly reduced at lower concentrations of the extracts, but it was synergistically enhanced at higher concentrations. All the extracts effectively scavenged superoxide anion, produced by hypoxanthine-xanthine oxidase reaction. Pretreatment of mice with the extracts significantly protected them from the lethal infection by E. coli. Similar activity was found in lignins from pine seed shell of Pinus parviflora Sieb. et Zucc. These data further support the medicinal efficacy of plant extracts.
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PMID:Radical modulation activity of lignins from a mangrove plant, Ceriops decandra (Griff.) Ding Hou. 970 79

The ESR signal of NO bound to hemoglobin was detected during the ischemia-reperfusion of myocardium with low temperature ESR technique, and the synergic effects of NO and oxygen free radicals in the injury of the process were studied with this technique. Oxygen free radicals and NO bound to beta-subunit of hemoglobin (beta-NO complex) could be detected simultaneously in the ischemia-reperfused myocardium. Those signals could not be detected from the normal myocardium even in the presence of L-arginine. However, those signals could be detected and were dose-dependent with L-arginine in the ischemia-reperfused myocardiums and the signal could be suppressed with the inhibitor of NO synthetase, NG-nitro-L-arginine methylester (NAME). Measurement of the activities of lactate dehydrogenase (LDH) and creatine kinase (CK) in the coronary artery effluent of ischemia-reperfused heart showed that L-arginine at lower concentration (< 1 mmol/L) could protect the heart form the ischemia-reperfusion injury but at higher concentration aggravate the injury. Addition of NAME to the reperfusion solution could also protect the myocardium. Addition of xanthine (X)/xanthine oxidase (XO) or Fe2+/H2O2 to the reperfusion solution increased the production of NO and oxygen free radicals and the ischemia-reperfused injury simultaneously. Addition of superoxide dismutase (SOD) and catalase decreased the production of NO and oxygen free radicals and the ischemia-reperfusion injury.
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PMID:Synergic effects of NO and oxygen free radicals in the injury of ischemia-reperfused myocardium--ESR studies on NO free radicals generated from ischemia-reperfused myocardium. 977 52

The radical modulation activity of lignins prepared from the cone of Pinus elliottii var. Elliottii was investigated, using ESR spectroscopy. These lignins produced radical(s) under alkaline conditions, and the radical intensity was increased with increasing pH. Lower concentrations of lignins slightly reduced the radical intensity of sodium ascorbate, whereas higher concentrations of lignins enhanced both the radical intensity and cytotoxic activity of sodium ascorbate. Lignins effectively scavenged superoxide anion, produced by hypoxanthine-xanthine oxidase reaction. Elliottii lignins significantly inhibited the human immunodeficiency virus (HIV)-induced cytopathic effect, in similar fashions to other natural, commercial and synthetic lignins. Pretreatment of mice with lignins significantly protected them from the lethal infection with E. coli. Crude alkaline extracts of Elliottii pine cone displayed similar magnitude of activity with lignins. These data further supports the medicinal efficacy of plant extracts.
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PMID:Radical modulation activity of pine cone extracts of Pinus elliottii var. Elliottii. 1022 67

The scavenging effects of total flavonoids of Lycium barbarum L. (TFL) were studied by using ESR-spin trapping technique and the inhibitory effects on heat output of both polymorphonuclear leukocyte(PMN) respiration burst and L1210 cells were measured by using microcalorimetric technique. TFL (0-217 mg/L) could scavenge O2-. in xanthine/xanthine oxidase (Xan/XO)system, with scavenging rate of 0-51%. TFL(7.5-200 mg/L)could scavenge OH. produced in Fenton reaction and the scavenging rate is between 20% to 72%. Those effects were concentration-dependent. Furthermore, TFL(0.56 g/L)could completely inhibit the heat output from PMA-stimulated PMN and TFL(1.0-5.0 g/L)could inhibit the heat output from L1210 cells.
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PMID:[Scavenging effect of total flavonoids of lycium barbarum L on active oxygen radicals and inhibitory effects on heat output from L1210 cells]. 1068 19

Grape seed extracts were more cytotoxic than grape peel extracts. Methanol and 70% methanol extracts of grape seed selectively killed two human oral tumor cell lines, more efficiently than human gingival fibroblasts. ESR spectroscopy revealed that these extracts produced radicals under alkaline conditions and enhanced the radical intensity of sodium ascorbate at higher concentrations. On the other hand, lower concentration of these extracts slightly reduced the radical intensity of sodium ascorbate, and scavenged superoxide anion, generated by hypoxanthine and xanthine oxidase reaction. These properties of grape seed extracts suggest their possible application for cancer prevention.
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PMID:Selective cytotoxic activity of grape peel and seed extracts against oral tumor cell lines. 1076 90


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