Hydroxyl radical toxicity scavengers

Peroxynitrite is a potent bactericidal agent for E. coli, with an LD50 of 250 tM at pH 7.4 and 37°C (Zhu et al., 1992). Neither 1 mM HjOj nor 10 mU/ml of xanthine oxidase plus xanthine were toxic in the same system. The toxicity was not due to the hydroxyl radical-like reactivity because lipid soluble radical scavengers either had no effect or slightly increased toxicity of peroxynitrite (Zhu... 

Although oxygen radicals are destructive to islet cells, the inability of nicotinamide, Probucol, and other free radical scavengers to completely prevent cytokine mediated islet destruction suggests that other cytotoxic mechanisms may be involved in cytokine-induced islet-cell lysis. The possible interactions of superoxide with nitric oxide resulting in the generation of peroxynitrite and hydroxyl radicals may contribute to islet-cell lysis. The chemistry of these free radical interactions, and potential biological roles t)f these toxic radicals are reviewed in this book (see Chapter 1). 

EGb 761 might also directly scavenge peroxynitrites and inhibit lipid peroxidation because it has been reported both to block the cytotoxicity induced by peroxynitrites and inhibit cyclosporine-A-induced peroxidation. This hypothesis is supported by the finding that the purported anti-ischemic agent ebselen completely protected and rescued hippocampal cells against SNP-induced toxicity. In contrast, the hydroxyl radical scavenging properties of EGb 761 do not seem able to account for its protective effects because catalase failed to display any neuroprotective properties in this model. 

Antioxidants, quenching molecules or radical scavenging enzymes such as superoxide dismutase (SOD), ascorbate peroxidase and catalase react with and neutralize the effects of the highly toxic ROS or hydroxyl radicals (HO ) pro-... 

An infusion of the dried flowering tops showed in vitro hydroxyl radical and hypochlorus acid scavenging activity. Orally administered, a Altered water suspension of the dried herb showed anti-inflammatory activity in a rat model of polyarthritis and when topically applied in a cream (2.5-10%) in the air-pouch granuloma bioassay. Antipyretic activity was found in rats from oral administration of the suspension against 2,4-dinitrophenol- and amphetamine-induced hyperthermia. Antipyretic activity of the herh is reported to be due to phenolic acids.Hepatoprotective activity against acetaminophen-induced toxicity was shown from oral administration of a methanol extract of the leaves. 

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