Superoxide anion radical generation inhibition

Japanese scientists believe that the anti-oketsu effects of rhubarb are brought about by the inhibition of the production of nitric oxide, inhibition of platelet aggregation, antiallergic effects, and its antiinflammatory properties. Matsuda et al. (2001) studied and reported that the methanolic extracts from five kinds of rhubarb were found to show scavenging activity for l,l-diphenyl-2-picrylhy-drazyl (DPPH) radical and superoxide anion radical (02 ) generated by the xanthine/xanthine oxidase system and/or on lipid peroxidation by terf-butyl hydroperoxide (f-BuOOH) in the erythrocyte membrane ghost system. 

Dipyridamole has also been shown to have antioxidant effects (19). Antioxidants act to remove harmful reactive-oxygen species and protect low-density lipoproteins (LDL) from oxidation oxidized LDL plays a key role in the development and propagation of atherosclerosis. The antioxidant effects of dipyridamole may be both direct (by scavenging oxygen and hydroxyl radicals, inhibiting lipid peroxidation and oxidative modification of LDL) (20-22) and indirect (via adenosine, which reduces superoxide anion generation). Dipyridamole has been shown to be a more effective anioxidant than ascorbic acid, alpha-tocopherol, or probucol (22). 

All the inhibitions reported so far indicate that there is no known specific inhibitor for the manganese superoxide dismutase. The enzyme from B. stearothermophilus was found to be inhibited by cacodylate (Thornalley et al., 1982) however, the inhibition could only be observed in the xanthine/xanthine oxidase assay and not in the pulse radiolysis assay. No evidence was obtained that cacodylate could be competing with the enzyme for because little or no inhibition was observed when the copper/zinc rather than the manganese enzyme was assayed in the presence of cacodylate. Further investigations revealed that the inhibitory effect is due to a cacodylate anion radical produced by the interaction of hydroxyl radicals (generated by the xanthine/xanthine oxidase reaction) and cacodylate anions. A radical of pamoic acid (4,4 -methylenebis-(3-... 

Marchantin H is a natural compound isolated from Marchantia diptera (Wu 1990). Marchantins are naturally phenolic structures isolated from different species of liverwort (Tori et al. 1985, Asakawa et al. 1987). Marchantin H could scavenge the stable free radical l,l-diphenyl-2-picrylhydrazyl and per-oxyl radical derived from 2,2 -azobis(2-amidino-propane) dihydrochloride in aqueous phase, but not the peroxyl radical derived from 2,2 -azobis (2,4-dimethylvaleronitrile) in hexane (Hsiao et al. 1996). It was reactive toward superoxide anion generated by the xanthine/xanthine oxidase system. Marchantin H inhibited copper-catalysed oxidation of human low-density lipoprotein, as measured by... 

Superoxide radicals are produced by a xanthine-xanthine oxidase system. Xanthine is able to generate 02 and H2O2 by using xanthine oxidase as a substrate. The superoxide radicals are able to reduce the yellow colored nitro triazolium blue (NTE) to the blue formazan, which is used for monitoring the reaction. The superoxide anions are measured spectrophotometricaUy. This test method was developed to explore the reaction between antioxidants and 02. So the inhibition of the superoxide reductase is a mark for the ability of antioxidative activity. 

---