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At least 19 recordsLinked to original sources
PubMed2002

Antioxidant activity of Hypericum androsaemum infusion: scavenging activity against superoxide radical, hydroxyl radical and hypochlorous acid.

Hypericum androsaemum is a medicinal plant species containing many polyphenolic compounds, namely flavonoids and phenolic acids. Since polyphenolic compounds have high antioxidant potential, the ability of H. androsaemum infusion to act as a scavenger of reactive oxygen species (superoxide radical, hydroxyl radical and hypochlorous acid) was investigated. Superoxide radical was generated by the xanthine/xanthine oxidase and phenazine methosulphate/NADH systems. The infusion-mediated prevention of nitroblue tetrazolium reduction by the superoxide radical was used as the measured endpoint. Hydroxyl radical was generated by the Fe3+-EDTA/ascorbate Fenton system, and assayed by evaluating deoxyribose degradation using the thiobarbituric acid method. Hypochlorous acid scavenging activity was tested by measuring the inhibition of hypochlorous acid-induced 5-thio-2-nitrobenzoic acid oxidation to 5,5'-dithiobis(2-nitrobenzoic acid). The tested infusion mainly exhibited a potent scavenging effect on superoxide radicals (although a noncompetitive inhibitory effect on xanthine oxidase was also observed). The infusion also acted as a moderate scavenger of hydroxyl radicals and hypochlorous acid. A phytochemical study of the infusion was also undertaken, and nine phenolic compounds were identified.

Antioxidants↗
PubMed2002

Studies on the antioxidant activity of Lippia citriodora infusion: scavenging effect on superoxide radical, hydroxyl radical and hypochlorous acid.

Lippia citriodora is an herbal species which contains several flavonoids and phenolic acids. In view of the pharmacological interest in natural phenolic compounds as antioxidants, this study examined the superoxide radical, hydroxyl radical and hypochlorous acid scavenging activities of L. citriodora infusion. Superoxide radical was generated either in an enzymatic or in a chemical system, and scavenging ability was assessed by the inhibition of nitroblue tetrazolium reduction. Hydroxyl radical was generated by the reaction of an iron-EDTA complex with H2O2 in the presence of ascorbic acid, and was assayed by evaluating deoxyribose degradation. Hypochlorous acid scavenging activity was tested by measuring the inhibition of 5-thio-2-nitrobenzoic acid oxidation. The results demonstrate that this infusion has a potent superoxide radical scavenging activity and a moderate scavenging activity of hydroxyl radical and hypochlorous acid. The chemical composition of the lyophilized infusion was also determined in an attempt to establish its relationship with the antioxidant activity found in the present study.

Antioxidants↗
PubMed2002

Antioxidative properties of cardoon (Cynara cardunculus L.) infusion against superoxide radical, hydroxyl radical, and hypochlorous acid.

Polyphenols are able to act as antioxidants by virtue of their hydrogen-donating and metal-chelating capacities. Cardoon (Cynara cardunculus L.) is a species containing considerable amounts of polyphenolic compounds, namely flavonoids and phenolic acids. This study examined the antioxidant activity of cardoon lyophilized infusion against superoxide radical, hydroxyl radical, and hypochlorous acid. Superoxide radical was generated either in an enzymatic system or nonenzymatically, and the scavenging ability was assessed by the inhibition of superoxide radical-induced reduction of nitroblue tetrazolium. Hydroxyl radical was generated by the Fe3+-EDTA/ascorbate Fenton system, and scavenging capacity was estimated by evaluating the inhibition of hydroxyl radical-induced deoxyribose degradation into thiobarbituric acid-reactive substances. Inhibition of hypochlorous acid-induced 5-thio-2-nitrobenzoic acid oxidation to 5,5'-dithiobis(2-nitrobenzoic acid) was used in order to test the hypochlorous acid scavenging activity.

Antioxidants↗
PubMed1999

Assaying for hydroxyl radicals: hydroxylated terephthalate is a superior fluorescence marker than hydroxylated benzoate.

Generation of hydroxyl radicals in terephthalate (benzene-1,4-dicarboxylic acid) solution yields fluorescent 2-hydroxy-terephthalate. The reaction product is stable for hours and can readily be assessed using standard fluorimeters. The efficiency, i.e. the relative increase of fluorescence per *OH radical, is about three times higher than that of the formation of salicylate (2-hydroxy-benzoate) from benzoic acid and approximately hundred-fold higher than that of the hydroxylation of phenylalanine. As the terephthalate molecule is symmetric with respect to ring-hydroxylation, only one isomer is formed; hence, mechanistic interpretation of the hydroxylation reaction is facilitated. The scavenging rate constant of terephthalate for *OH yielding the hydroxycyclohexadienyl adduct as first intermediate is close to the diffusion controlled limit (k = 3.3 x 10(9) M(-1) s(-1)). Therefore, competition of the detector molecule with biomolecules being present under physiological conditions is expected to be efficient. The assay can be used to detect 'free' *OH radicals produced by the radiolysis of water as well as 'hydroxyl analogous species' that have been suggested to arise from the interaction of complex-bound reduced metal with either oxygen or hydrogen peroxide, e.g. from Fenton reactions. Based on calibration with radiolytically generated hydroxyl radicals the detection limit of the method is estimated to be around 50 nmol/dm3. Terephthalate is classified non-toxic and hence may also prove useful for microdialysis and continuous flow experiments as observation of fluorescence is 'non-destructive' and the reporter substance does not necessarily have to be subjected to HPLC.

Benzoic Acid↗
PubMed1998

Nitric oxide donor-induced hyperpermeability of cultured intestinal epithelial monolayers: role of superoxide radical, hydroxyl radical, and peroxynitrite.

Many of the cytopathic effects of nitric oxide (NO*) are mediated by peroxynitrite (PN), a product of the reaction between NO* and superoxide radical (O2*-). In the present study, we investigated the role of PN, O2*- and hydroxyl radical (OH*) as mediators of epithelial hyperpermeability induced by the NO* donor, S-nitroso-N-acetylpenicillamine (SNAP), and the PN generator, 3-morpholinosydnonimine (SIN-1). Caco-2BBe enterocytic monolayers were grown on permeable supports in bicameral chambers. Epithelial permeability, measured as the apical-to-basolateral flux of fluorescein disulfonic acid, increased after 24 h of incubation with 5.0 mM SNAP or SIN-1. Addition of 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, an NO* scavenger, or Tiron, an O2*- scavenger, reduced the increase in permeability induced by both donor compounds. The SNAP-induced increase in permeability was prevented by allopurinol, an inhibitor of xanthine oxidase (a source of endogenous O2*-). Diethyldithiocarbamate, a superoxide dismutase inhibitor, and pyrogallol, an O2* generator, potentiated the increase in permeability induced by SNAP. Addition of the PN scavengers deferoxamine, urate, or glutathione, or the OH* scavenger mannitol, attenuated the increase in permeability induced by both SNAP and SIN-1. Both donor compounds decreased intracellular levels of glutathione and protein-bound sulfhydryl groups, suggesting the generation of a potent oxidant. These results support a role for PN, and possibly OH*, in the pathogenesis of NO* donor-induced intestinal epithelial hyperpermeability.

Antioxidants↗
PubMed1997

Mannitol Protects against Oxidation by Hydroxyl Radicals.

Hydroxyl radicals may be responsible for oxidative damage during drought or chilling stress. We have shown that the presence of mannitol in chloroplasts can protect plants against oxidative damage by hydroxyl radicals (B. Shen, R.G. Jensen, H.J. Bohnert [1997] Plant Physiol 113: 1177-1183). Here we identify one of the target enzymes that may be protected by mannitol. Isolated thylakoids in the presence of physiological concentrations of Fe2+ generated hydroxyl radicals that were detected by the conversion of phenylalanine into tyrosine. The activity of phosphoribulokinase (PRK), a thiol-regulated enzyme of the Calvin cycle, was reduced by 65% in illuminated thylakoids producing hydroxyl radicals. Mannitol (125 mM) and sodium formate (15 mM), both hydroxyl radical scavengers, and catalase (3000 units mL-1) prevented loss of PRK activity. In contrast, superoxide dismutase (300 units mL-1) and glycine betaine (125 mM) were not effective in protecting PRK against oxidative inactivation. Ribulose-1,5-bisphosphate carboxylase/oxygenase activity was not affected by hydroxyl radicals. We suggest that the stress-protective role of mannitol may be to shield susceptible thiol-regulated enzymes like PRK plus thioredoxin, ferredoxin, and glutathione from inactivation by hydroxyl radicals in plants.

Journal Article↗
PubMed1987

The deoxyribose method: a simple "test-tube" assay for determination of rate constants for reactions of hydroxyl radicals.

Hydroxyl radicals, generated by reaction of an iron-EDTA complex with H2O2 in the presence of ascorbic acid, attack deoxyribose to form products that, upon heating with thiobarbituric acid at low pH, yield a pink chromogen. Added hydroxyl radical "scavengers" compete with deoxyribose for the hydroxyl radicals produced and diminish chromogen formation. A rate constant for reaction of the scavenger with hydroxyl radical can be deduced from the inhibition of color formation. For a wide range of compounds, rate constants obtained in this way are similar to those determined by pulse radiolysis. It is suggested that the deoxyribose assay is a simple and cheap alternative to pulse radiolysis for determination of rate constants for reaction of most biological molecules with hydroxyl radicals. Rate constants for reactions of ATP, ADP, and Good's buffers with hydroxyl radicals have been determined by this method.

Ascorbic Acid↗
PubMed1999

Quantification of total oxidant scavenging capacity of antioxidants for peroxynitrite, peroxyl radicals, and hydroxyl radicals.

We have extended the application of our previously reported total oxidant scavenging capacity (TOSC) assay (Winston et al., Free Radical Biol. Med. 24, 480-493, 1998) to permit facile quantification of the absorbance capacity of antioxidants toward three potent oxidants, i.e., hydroxyl radicals, peroxyl radicals, and peroxynitrite. Respectively, these oxidants were generated by the iron plus ascorbate-driven Fenton reaction, thermal homolysis of 2,2'-azobis(2-methylpropionamidine) dihydrochloride (ABAP), and 3-morpholinosydnonimine N-ethylcarbamide (SIN-1). Each of these oxidants reacts with alpha-keto-gamma-methiolbutyric acid (KMBA), which is oxidized and yields ethylene. The antioxidant capacity of the compounds tested is quantified from their ability to inhibit ethylene formation relative to a control reaction. Assay conditions were established in which control reactions give comparable yields of ethylene with each of the oxidants studied. Thus, the relative efficiency of various antioxidants could be compared under conditions of quantitatively similar KMBA oxidizing capability by the three oxidants. Reduced glutathione was an efficient scavenger of peroxyl radicals, but scavenged peroxynitrite and hydroxyl radicals relatively poorly. Uric acid, Trolox, and ascorbic acid were comparable scavengers of peroxynitrite and peroxyl radicals. Uric acid and Trolox were approximately an order of magnitude less efficient as scavengers of hydroxyl radicals. The classical hydroxyl radical scavenging agents mannitol, dimethyl sulfoxide, and benzoic acid had much higher TOSC values with hydroxyl than with peroxyl radicals or peroxynitrite. The very different chemical reactivity toward KMBA by the SIN-1- and iron-ascorbate-generated oxidants indicates that hydroxyl radical is not a major oxidant produced by the SIN-1 system. The data show that the TOSC assay is useful and robust in distinguishing the reactivity of various oxidants and the relative capacities of antioxidants to scavenge these oxidants.

Amidines↗
PubMed1983

Superoxide-dependent lipid peroxidation. Problems with the use of catalase as a specific probe for fenton-derived hydroxyl radicals.

Hydroxyl radicals (OH.) can initiate lipid oxidation by hydrogen abstraction. Transition metals however, particularly iron and copper, stimulate lipid oxidation by reacting with lipid peroxides to form new radical species. The haem-iron protein catalase can react non-specifically with lipid peroxides in this way resulting in loss of their conjugated diene structures. When a superoxide-generating system is used to stimulate lipid autoxidation, catalase can conceivably inhibit the reaction in two ways (A) by decomposing lipid peroxides as they are formed (B) through the removal of hydrogen peroxide preventing OH. radical formation. Results presented here suggest that the latter interpretation, although commonly presented, cannot be automatically assumed.

Catalase↗
PubMed2005

In vitro evaluation of orthopedic composite cytotoxicity: assessing the potential for postsurgical production of hydroxyl radicals.

Hydroxyl radical (*OH)-induced inflammation is a primary mode for in vivo cytotoxicity. A legitimate concern is whether particulate wear debris from orthopedic composites can stimulate inflammation via ferrous ion (Fe2+)-mediated production of *OH. The purpose of this research was to utilize electron paramagnetic resonance (EPR) spin trapping in investigating and comparing the potential for postsurgical cytotoxicity induced specifically by *OH in the presence of two composites: Simplex P and the novel, hybrid, CORTOSS. Cytotoxicity is evaluated based on the composites competitively chelating catalytic Fe2+ or readily reducing ferric ions (Fe3+), in facilitating the Fenton reaction (FR). *OH that are produced were then validated by a radical scavenger to confirm a genuine radical signal and mechanism. Spin adduct peak areas decreased in the presence of CORTOSS as opposed to increasing in the presence of Simplex P, evaluated against their respective controls. A plausible theory elucidating this finding is that CORTOSS may sequester the Fe form, by virtue of its monomers. Principally, direct comparison of composites indicated that Simplex P had greater tendency to produce *OH, yielding 25.6 and 48.7% greater spin adduct peak areas when chelated and non-chelated Fe2+ are used, respectively. Moreover, the rate of FR accelerated when chelated Fe2+ was used, leading to the formation of a ternary complex with the composites. This was more prominent in Simplex P, as coordination of chelated Fe2+ occurs on its surface via an electrostatic attraction to allow a seventh coordination site for ligand exchange in the ternary complex, stabilized by Ba2+. Conversely, the silica found in CORTOSS possesses radical quenching abilities that deactivate generated *OH in impeding the efficiency of FR. Neither composite demonstrated a capacity to readily reduce Fe3+ to the relevant Fe2+, as validated by a non-radical pathway. Instead, the artificial spin adduct signal attained when employing chelated Fe3+ was due to the nucleophilic addition of water onto DMPO. Simplex P may also serve as a template for surface catalysis of the nucleophilic addition of water onto DMPO involving chelated Fe3+. CORTOSS is thought not to induce cytotoxicity, whereas the propensity of Simplex P in promoting Fenton chemistry is a serious issue that must be addressed.

Composite Resins↗
PubMed1994

Aromatic hydroxylation of phenylalanine as an assay for hydroxyl radicals. Measurement of hydroxyl radical formation from ozone and in blood from premature babies using improved HPLC methodology.

Highly reactive hydroxyl radicals (OH.) attack the amino acid phenylalanine to give ortho-, meta-, and para-tyrosines. An improved HPLC-based separation of these products is described. Both D- and L-phenylalanine are attacked by OH., although only the latter is a substrate for the enzyme phenylalanine hydroxylase. Use of this improved aromatic hydroxylation assay to detect OH. is illustrated by measuring OH. in ozonized aqueous solutions at pH 7.4, and by showing that blood from some premature babies appears to be capable of catalyzing OH. formation.

Catalysis↗
PubMed1997

Mass spectrometric quantification of markers for protein oxidation by tyrosyl radical, copper, and hydroxyl radical in low density lipoprotein isolated from human atherosclerotic plaques.

Lipoprotein oxidation has been implicated in the pathogenesis of atherosclerosis. However, the physiologically relevant pathways mediating oxidative damage have not yet been identified. Three potential mechanisms are tyrosyl radical, hydroxyl radical, and redox active metal ions. Tyrosyl radical forms o,o'-dityrosine cross-links in proteins. The highly reactive hydroxyl radical oxidizes phenylalanine residues to o-tyrosine and m-tyrosine. Metal ions oxidize low density lipoprotein (LDL) by poorly understood pathways. To explore the involvement of tyrosyl radical, hydroxyl radical, and metal ions in atherosclerosis, we developed a highly sensitive and quantitative method for measuring levels of o, o'-dityrosine, o-tyrosine, and m-tyrosine in proteins, lipoproteins, and tissue, using stable isotope dilution gas chromatography-mass spectrometry. We showed that o,o'-dityrosine was selectively produced in LDL oxidized with tyrosyl radical. Both o-tyrosine and o, o'-dityrosine were major products when LDL was oxidized with hydroxyl radical. Only o-tyrosine was formed in LDL oxidized with copper. Similar profiles of oxidation products were observed in bovine serum albumin oxidized with the three different systems. Applying these findings to LDL isolated from human atherosclerotic lesions, we detected a 100-fold increase in o,o'-dityrosine levels compared to those in circulating LDL. In striking contrast, levels of o-tyrosine and m-tyrosine were not elevated in LDL isolated from atherosclerotic tissue. Analysis of fatty streaks revealed a similar pattern of oxidation products; compared with normal aortic tissue, there was a selective increase in o,o'-dityrosine with no change in o-tyrosine. The detection of a selective increase of o,o'-dityrosine in LDL isolated from vascular lesions is consistent with the hypothesis that oxidative damage in human atherosclerosis is mediated in part by tyrosyl radical. In contrast, these observations do not support a role for free metal ions as catalysts of LDL oxidation in the artery wall.

Animals↗
PubMed1985

Cobalt(II) ion as a promoter of hydroxyl radical and possible 'crypto-hydroxyl' radical formation under physiological conditions. Differential effects of hydroxyl radical scavengers.

Co(II) ions react with hydrogen peroxide under physiological conditions to form a 'reactive species' that can hydroxylate aromatic compounds (phenol and salicylate) and degrade deoxyribose to thiobarbituric-acid-reactive material. Catalase decreases the formation of this species but superoxide dismutase or low concentrations of ascorbic acid have little effect. EDTA, present in excess over the Co(II), can accelerate deoxyribose degradation and aromatic hydroxylation. In the presence of EDTA, deoxyribose degradation by the reactive species is inhibited competitively by scavengers of the hydroxyl radical (.OH), their effectiveness being related to their second-order rate constants for reaction with .OH. In the absence of EDTA the scavengers inhibit only at much higher concentrations and their order of effectiveness is changed. It is suggested that, in the presence of EDTA, hydroxyl radical is formed 'in free solution' and attacks deoxyribose or an aromatic molecule. In the absence of EDTA, .OH radical is formed in a 'site-specific' manner and is difficult to intercept by .OH scavengers. The relationship of these results to the proposed 'crypto .OH' radical is discussed.

Chemical Phenomena↗
PubMed1995

Elucidation of antioxidant activity of dihydrolipoic acid toward hydroxyl radical using a novel hydroxyl radical generator NP-III.

The photosensitive organic hydroperoxide, NP-III, which produces hydroxyl radicals on illumination by UVA light, was used to examine the antioxidant activity of dihydrolipoic acid toward hydroxyl radical. Apolipoprotein (apo-B) of human low density lipoprotein (LDL), and bovine serum albumin (BSA), were irradiated with UVA in the presence of NP-III and dihydrolipoic acid. The oxidation of BSA and apo-B of LDL by NP-III was completely inhibited by dihydrolipoic acid. ESR studies using dimethylpyrroline oxide (DMPO) as a spin trapping reagent also revealed that in the presence of dihydrolipoic acid, the DMPO-OH adduct produced from the irradiation of NP-III and DMPO completely disappeared. Hence, the scavenging activity of dihydrolipoic acid is not due to its chelating activity toward transition metals (ferrous ions). The results lead us to conclude that dihydrolipoic acid is an efficient hydroxyl radical scavenger through the direct reaction of dihydrolipoic acid with hydroxyl radical.

Antioxidants↗
PubMed1979

Response of platelets exposed to potassium tetraperoxochromate, an extracellular source of singlet oxygen, hydroxyl radicals, superoxide anions and hydrogen-peroxide.

When potassium tetraperoxochromate (K3CrO8) is added to platelet suspension media it decomposes to the oxygen species hydrogen peroxide, superoxide radicals, hydroxyl radicals, and singlet oxygen. K3CrO8 induces a reversible shape change and aggregation of human platelets and, in the presence of Tris or sucrose, also the release of serotonin. Its effect on shape change and aggregation is due to the long-lived species hydrogen peroxide and is abolished by indomethacin and acetylsalicylic acid. Superoxide radicals, which are formed from K3CrO8 in HEPES-containing media do not evoke a platelet response. The release of serotonin depends on an interaction of hydroxyl radicals with Tris or sucrose and is associated with excessive formation of thiobarbituric acid-reactive material from platelets. Other scavengers of hydroxyl radicals such as mannitol, dimethylsulfoxide, EDTA or histidine prevent the release and the formation of thiobarbituric acid chromogen. Interaction of hydroxyl radicals with Tris or sucrose most likely results in the generation of short-lived intermediates which may act on platelets to produce thiobarbituric acid chromogen and to promote serotonin release. These effects on platelets are not inhibited by acetylsalicylic acid or indomethacin. Therefore the highly reactive hydroxyl radical and singlet oxygen, when generated extracellularly, do not mediate their effects via the enzyme-catalyzed prostaglandin pathway, in contrast to those evoked by the less reactive hydrogen peroxide.

Blood Platelets↗
PubMed1993

Effective inhibition of hydroxyl radicals by hydroxylated biphenyl compounds.

In aqueous media, approximate rate constants for the reactions between hydroxyl radicals (.OH) and biphenyl compounds such as dehydrodieugenol, magnolol, honokiol, dehydrodidihydroeugenol, dehydrodivanillyl alcohol, and dehydrodicreosol were estimated by competition reactions for .OH between these biphenyls and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). By measuring the decrease in the height of the EPR signals of the .OH spin adduct, rate constants in the order of 10(9) to 10(10) M were measured.

Biphenyl Compounds↗