ascorbic-acid and nitecapone

The antioxidant properties of nitecapone, a catechol derivative and an inhibitor of catechol-O-methyltransferase, were reported recently. In the present study, the influence of nitecapone on isolated rat heart ischemia-reperfusion injury was investigated to elucidate its cardioprotective role. Nitecapone, administered in the perfusion buffer from the beginning of the pre-ischemic phase, significantly improved recovery of cardiac mechanical function, suppressed enzyme leakage in the coronary effluent, and minimized loss of ascorbate, compared with the control group. In rats fed a diet containing 4% ascorbate, myocardial ascorbate content in ascorbate-fed rats after ischemia-reperfusion was higher than that in control rats fed a normal diet without ischemia. However, supplemented rats did not show any beneficial effects on cardiac mechanical recovery or enzyme leakage, suggesting that maintenance of tissue ascorbate level is not the cause, but the result of the protective effects of nitecapone against cardiac ischemia-reperfusion injury. The iron-chelating effect of nitecapone was also tested. It was confirmed, using electron spin resonance, that 50 microM nitecapone chelates the same concentration of iron released from the heart into the coronary effluent. Hence, the iron-chelating ability of nitecapone may be responsible, at least in part, for its cardioprotective effects in ischemia-reperfusion injury.

Topics: Animals; Antioxidants; Ascorbic Acid; Catechol O-Methyltransferase Inhibitors; Catechols; Drug Interactions; Enzyme Inhibitors; Free Radical Scavengers; Iron Chelating Agents; Male; Myocardial Ischemia; Myocardial Reperfusion Injury; Pentanones; Rats; Rats, Sprague-Dawley

The effect of nitecapone (3[(3,4-dihydroxy-5-nitrophenyl) methylene]-2,4-pentanedione) on lipid peroxidation in guinea pig liver microsomes was assessed with the thiobarbituric acid assay. Nitecapone inhibited dose-dependently hydroxyl and peroxyl radical induced lipid peroxidation with IC50-values of 11.1 microM and 16.2 microM, respectively. Nitecapone was an effective antioxidant in native microsomes, where it potentiated glutathione-dependent protection against oxidative stress. Nitecapone provided dose-dependent reduction in lipid peroxidation lasting up to three hours in the presence of glutathione. The long-lasting effect was lost, when the microsomes were boiled. These data suggest that nitecapone is an effective scavenger of oxygen derived free radicals, and that its antioxidant properties are potentiated by glutathione.

Topics: Animals; Antioxidants; Ascorbic Acid; Catechols; Drug Synergism; Ferrous Compounds; Free Radical Scavengers; Glutathione; Guinea Pigs; Kinetics; Lipid Peroxidation; Male; Microsomes, Liver; Pentanones; Thiobarbituric Acid Reactive Substances; Time Factors

We studied in vitro the ability of nitecapone, 3-[(3,4-dihydroxy-5-nitrophenyl)methylene]-2,4-pentanedione, a novel water-soluble compound with antioxidative properties, to inhibit the LDL oxidation promoted by copper ions, the aqueous free radical generator 2,2'-azobis(2-amidinopropane) hydrochloride (AAPH), and mouse peritoneal macrophages. In these three oxidation systems, the extent of LDL oxidation was determined by measuring the formation of conjugated dienes, the formation of thiobarbituric acid-reactive substances, the change in the electrophoretic mobility of LDL, and the uptake of LDL by macrophages. When LDL oxidation was promoted by copper ions, the reaction was found to be inhibited by nitecapone added in a three- to five-molar excess of the concentration of copper ions. The mechanism by which nitecapone exerted its antioxidative effect in copper-mediated LDL oxidation depended on binding and redox inactivation of the copper ions. Moreover, nitecapone released LDL-bound copper ions and so rendered the LDL particles more resistant to oxidation. In contrast to a water-soluble alpha-tocopherol analogue that was rapidly consumed during the oxidative process, nitecapone retained its inhibitory effect for at least 2 days. Using immobilized metal ion affinity chromatography, we showed that nitecapone binds both copper and iron ions, whereas its affinity for zinc ions is low. Nitecapone also inhibited LDL oxidation in the free radical-mediated oxidation system (AAPH). In this system, nitecapone showed synergistic antioxidative action with ascorbic acid. Finally, nitecapone inhibited macrophage-mediated LDL oxidation. Accordingly, nitecapone appears to have a unique antioxidative profile in that it both selectively chelates pro-oxidative transition metals and scavenges free radicals.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Amidines; Animals; Antioxidants; Ascorbic Acid; Catechols; Copper; Female; Free Radicals; Humans; Iron; Lipid Peroxidation; Lipoproteins, LDL; Macrophages, Peritoneal; Mice; Oxidation-Reduction; Pentanones; Thiobarbituric Acid Reactive Substances

Nitecapone [3-(3,4-dihydroxy-5-nitrophenyl)methylene-2,4-pentanedione] [OR-462] is a catechol-O-methyltransferase inhibitor with gastroprotective properties. Recently, its antioxidant properties have been discovered: It scavenges peroxyl radicals (ROO.) and thus spares glutathione. Further examination of the properties of nitecapone demonstrated a remarkable ability of this compound to act as an antioxidant: (1) to scavenge ROO. in solution with a stoichiometry factor of 2; (2) to scavenge ROO. in membranes; (3) to inhibit lipid peroxidation; (4) to act as a competitive inhibitor for xanthine oxidase with Ki of 8.8 microM; (5) to scavenge O2- with a second order kinetic rate constant of 1.0 x 10(4) M-1 s-1; and (6) to scavenge HO.. Nitecapone also interacts with oxidation product of ascorbate to participate in recycling of vitamin E. Thus, nitecapone potentially is an effective therapeutic antioxidant, and the use of this compound in a combination with other antioxidants may be beneficial.

Topics: Animals; Antioxidants; Ascorbic Acid; Azo Compounds; Catechol O-Methyltransferase Inhibitors; Catechols; Cattle; Electron Spin Resonance Spectroscopy; Kinetics; Lipid Peroxidation; Luminescent Measurements; Microsomes; Milk; Myocardium; Nitriles; Pentanones; Rats; Spectrometry, Fluorescence; Spectrophotometry; Superoxides; Thiobarbituric Acid Reactive Substances; Xanthine Oxidase