Hydroxyl radical quenching

The key intermediate chemical species in the troposphere is undoubtedly the hydroxyl radical OH, the major source being the photolysis of tropospheric ozone, and subsequent reaction of the product O ( D) with water (13), (14), in competition with coUisional quenching to give O ( P) (15), which subsequently reforms ozone (16). 

Ability to quench hydroxyl radicals generated in a model system... 

Ascorbic acid reacts with 02" generated from the xanthine oxidase system and may play a role against 02" mediated toxicity. Ascorbic acid quenches the hydroxyl radical (40), Ascorbic acid may protect against free radicals in the lung because ascorbic acid is found in the fluid (39). The toxicity of ozone and oxygen may also be reduced by ascorbic acid (39). Carbon tetrachloride mortality in rats is lowered by ascorbic acid. Autoxidation of ascorbic acid did not generate 02". Reduced glutathione reacts with dehydroascorbic acid (VII) and recycles ascorbic acid. 

The scavenging effect of berbamine on active oxygen radicals was studied via a spintrapping technique and a chemiluminescence (CL) method in phorbol myristate acetate (PMA) stimulated polymorphonuclear leukocytes (PMN) and in four-cell superoxide (02+) or hydroxyl radical (OH ) generating systems. The alkaloid (0.1-0.3 mM) effectively reduced active oxygen radicals in PMA-stimulated PMN, but had no obvious effect on oxygen consumption during the respiratory burst of PMN (as measured with spin probe oxymetry). In addition, berbamine (0.3 mM) inhibited the CL response of PMA-stimulated PMN, and quenched 02 in the xanthine/xanthine oxidase and irradiation riboflavin systems, as well as OH in the Fenton... 

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-... 

In this study, therefore, flow injection analysis-chemiluminescence (FIA-CL) methods to evaluate quenching effects of functional foods against ROS such as singlet oxygen ( 02) and hydroxyl radicals (OH) were developed. The applicabilities of these methods were confirmed by evaluating quenching effects of grape seed extracts and their isolated polyphenols. 

It is believed that ascorbate free radicals have an important biological function in the reaction with destructive free radicals, particularly those associated with oxygen which often cause problems in living cells. They have been shown to quench hydroxyl radical and singlet oxygen, a function that is thought to be particularly important in the eye where comparatively large amounts of vitamin C are frequently found. 

The quenching of peroxidized luminol chemiluminescence by reduced pyridine nucleotides has been reported. Neither superoxide nor hydroxyl radical scavengers were found to quench the chemiluminescence of luminol in the presence of horseradish peroxidase and H2O2. Both chemi- and bio-luminescence of firefly luciferin have been investigated and a dioxetanone mechanism proposed for the light-producing pathway. ... 

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