Hydroxyl Radicals (hydroxyl + radical)

Distribution by Scientific Domains
Distribution within Chemistry

Kinds of Hydroxyl Radicals

  • reactive hydroxyl radical

  • Terms modified by Hydroxyl Radicals

  • hydroxyl radical scavenger

  • Selected Abstracts

    Estimation of Aqueous-Phase Reaction Rate Constants of Hydroxyl Radical with Phenols, Alkanes and Alcohols

    MOLECULAR INFORMATICS, Issue 11-12 2009
    Ya-nan Wang
    Abstract A quantitative structure activity relationship (QSAR) model was developed for the aqueous-phase hydroxyl radical reaction rate constants (kOH) employing quantum chemical descriptors and multiple linear regressions (MLR). The QSAR development followed the OECD guidelines, with special attention to validation, applicability domain (AD) and mechanistic interpretation. The established model yielded satisfactory performance: the correlation coefficient square (R2) was 0.905, the root mean squared error (RMSE) was 0.139, the leave-many-out cross-validated QLMO2 was 0.806, and the external validated QEXT2 was 0.922 log units. The AD of the model covering compounds of phenols, alkanes and alcohols, was analyzed by Williams plot. The main molecular structural factors governing kOH are the energy of the highest occupied molecular orbital (EHOMO), average net atomic charges on hydrogen atoms (), molecular surface area (MSA) and dipole moment (,). It was concluded that kOH increased with increasing EHOMO and MSA, while decreased with increasing and ,. [source]

    ChemInform Abstract: Evidence for a Lower Enthalpy of Formation of Hydroxyl Radical and a Lower Gas-Phase Bond Dissociation Energy of Water.

    CHEMINFORM, Issue 15 2001
    Branko Ruscic
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

    Reactions of Hydroxyl Radical with Salicylic Acid Derivatives: A Pulse Radiolysis Study

    Jian-Hua Ma
    Abstract Based on pulse radiolysis of aqueous solutions of two salicylic acid derivatives including ethyl salicylate and benzylsalicylate the transient absorption spectra and the rate constants of hydroxyl radical with salicylic acid derivatives were determined for the first time. The results indicated that ethyl salicylate and benzylsalicylate have efficient activities to scavenge hydroxyl radical. [source]

    Hydroxyl Radicals Attack Metallic Gold,

    ANGEWANDTE CHEMIE, Issue 6 2010
    Maria Nowicka Dr.
    Feinschliff: Unebenheiten auf einer polierten Goldoberfläche werden von OH. -Radikalen aus dem Fenton-Reagens abgetragen. Anfangs wird Au dabei schnell aufgelöst, wenn die Unebenheiten verschwunden sind, kommt dieser Prozess jedoch praktisch zum Stillstand. Die OH. -Radikale oxidieren zwar auch glatte Au-Oberflächen, auf diesen bildet sich aber eine stabile Oxidmonoschicht. [source]

    The Ability Of Thiourea To Scavenge Hydrogen Peroxide And Hydroxyl Radicals During The Intra-Coronal Bleaching Of Root-Filled Blood-Stained Teeth

    Dr Dan Farmer
    No abstract is available for this article. [source]

    Oestradiol Protects Against the Harmful Effects of Fluoride More by Increasing Thiol Group Levels than Scavenging Hydroxyl Radicals

    Anna Dlugosz
    Interactions between xenobiotics and oestrogens need to be investigated, especially as many chemicals interact with the oestrogen receptor. It is still unknown whether free radical-generating xenobiotics can influence the antioxidative ability of oestradiol (E2). In an in vitro examination of human placental mitochondria, thiobarbituric active reagent species (TBARS), hydroxyl radical (,OH) generation and protein thiol (,SH) groups were detected. 17,-E2 was examined in physiological (0.15,0.73 nM) and experimental (1,10 µM) concentrations and sodium fluoride (NaF) in concentrations of 6,24 µM. E2 in all the concentrations significantly decreased lipid peroxidation measured as the TBARS level, in contrast to NaF, which increased lipid peroxidation. Lipid peroxidation induced by NaF was decreased by E2. The influence of E2 on ,OH generation was not very significant and depended on the E2 concentration. The main mechanism of E2 protection in NaF exposure appeared to be connected with the influence of E2 on thiol group levels, not ,OH scavenging ability. The E2 in concentrations 0.44,0.73 nM and 1,10 µM significantly increased the levels of ,SH groups, in contrast to NaF, which significantly decreased them. E2 at every concentration reversed the harmful effects of NaF on ,SH group levels. No unfavourable interactions in the influence of E2 and NaF on TBARS production, ,OH generation, or ,SH group levels were observed. The results suggest that postmenopausal women could be more sensitive to NaF-initiated oxidative stress. [source]

    Comparative study on composition and antioxidant properties of mint and black tea extract

    Ekambaram Padmini
    Summary The antioxidant properties of plants could be correlated with oxidative stress defence in different human diseases. The present study was undertaken to evaluate and compare the antioxidant potential and the phytochemical composition in the aqueous extracts of mint leaves, black tea and black tea enriched with mint extract. All the three preparations exhibited free radical-scavenging potential for nitric oxide (NO) radical, superoxide anion radical and hydroxyl radical, and the values were lesser than those of the antioxidants which acted as standards. In comparison, the mint extract exhibited higher free radical and NO scavenging effect. Hydroxyl radical and superoxide scavenging effects were more pronounced in tea with the mint extract, while the reducing power was exhibited more significantly by the black tea extract. The phytochemical compounds were identified and the total phenols and flavonoids were quantified and compared between these extracts. [source]

    Investigation on the interaction between dihydroxybenzene and Fe3+,H2O2,Rh6G system based on enhancing chemiluminescence

    Deyong He
    Abstract A highly sensitive flow-injection chemiluminescence (FI,CL) method has been developed for the determination of dihydroxybenzene, based on the hydroxyl radical reaction. Hydroxyl radical (·OH) produced by the reaction of Fe3+ and H2O2 oxidize rhodamine 6G to produce weak CL. It was observed that catechol and hydroquinone greatly enhanced the weak CL reaction. However, the proposed CL system is not suitable for determination of resorcinol because the enhancement reaction is very slow. The proposed procedure has a linear range of 0.01,2 mg/L for catechol, with a detection limit of 0.006 mg/L, and 0.008,1 mg/L for hydroquinone, with a detection limit of 0.004 mg/L. The possible mechanism of the CL system is discussed. Copyright © 2005 John Wiley & Sons, Ltd. [source]

    Reduction of ciclosporin and tacrolimus nephrotoxicity by plant polyphenols

    Zhi Zhong
    The immunosuppressants ciclosporin (cyclosporin A, CsA) and tacrolimus can cause severe nephrotoxicity. Since CsA increases free radical formation, this study investigated whether an extract from Camellia sinensis, which contains several polyphenolic free radical scavengers, could prevent nephrotoxicity caused by CsA and tacrolimus. Rats were fed powdered diet containing polyphenolic extract (0-0.1%) starting 3 days before CsA or tacrolimus. Free radicals were trapped with ,-(4-pyridyl-1-oxide)- N - tert -butylnitrone (POBN) and measured using an electron spin resonance spectrometer. Both CsA and tacrolimus decreased glomerular filtration rates (GFR) and caused tubular atrophy, vacuolization and calcification and arteriolar hyalinosis, effects that were blunted by treatment with dietary polyphenols. Moreover, CsA and tacrolimus increased POBN/radical adducts in urine nearly 3.5 fold. Hydroxyl radicals attack dimethyl sulfoxide (DMSO) to produce a methyl radical fragment. Administration of CsA or tacrolimus with 12C-DMSO produced a 6-line spectrum, while CsA or tacrolimus given with 13C-DMSO produced a 12-line ESR spectrum, confirming formation of hydroxyl radicals. 4-Hydroxynonenal (4-HNE), a product of lipid peroxidation, accumulated in proximal and distal tubules after CsA or tacrolimus treatment. ESR changes and 4-HNE formation were largely blocked by polyphenols. Taken together, these results demonstrate that both CsA and tacrolimus stimulate free radical production in the kidney, most likely in tubular cells, and that polyphenols minimize nephrotoxicity by scavenging free radicals. [source]

    Oxidative gating of water channels (aquaporins) in Chara by hydroxyl radicals

    PLANT CELL & ENVIRONMENT, Issue 9 2004
    ABSTRACT Hydroxyl radicals (*OH) as produced in the Fenton reaction (Fe2+ + H2O2 = Fe3+ + OH, + *OH) have been used to reversibly inhibit aquaporins in the plasma membrane of internodes of Chara corallina. Compared to conventional agents such as HgCl2, *OH proved to be more effective in blocking water channels and was less toxic to the cell. When internodes were treated for 30 min, cell hydraulic conductivity (Lp) decreased by 90% or even more. This effect was reversed within a few minutes after removing the radicals from the medium. In contrast to HgCl2, radical treatment reduced membrane permeability of small lipophilic organic solutes (ethanol, acetone, 1-propanol, and 2-propanol) by only 24 to 52%, indicating some continued limited movement of these solutes across aquaporins. The biggest effect of *OH treatment on solute permeability was found for isotopic water (HDO), which largely used water channels to cross the membrane. Inhibition of aquaporins reduced the diffusional water permeability (Pd) by about 70%. For the organic test solutes, which mainly use the bilayer to cross the membrane, channel closure caused anomalous (negative) osmosis; that is, cells had negative reflection coefficients (,s) and were transiently swelling in a hypertonic medium. From the ratio of bulk (Lp or osmotic permeability coefficient, Pf) to diffusional (Pd) permeability of water, the number (N) of water molecules that align in water channels was estimated to be N = Pf/Pd = 46 (on average). Radical treatment decreased N from 46 to 11, a value still larger than unity, which would be expected for a membrane lacking pores. The gating of aquaporins by *OH radicals is discussed in terms of a direct action of the radicals when passing the pores or by an indirect action via the bilayer. The rapid recovery of inhibited channels may indicate an easy access of cytoplasmic antioxidants to closed water channels. As hydrogen peroxide is a major signalling substance during different biotic and abiotic stresses, the reversible closure of water channels by *OH (as produced from H2O2 in the apoplast in the presence of transition metals such as Fe2+ or Cu+) may be downstream of the H2O2 signalling. This may provide appropriate adjustments in water relations (hydraulic conductivity), and a common response to different kinds of stresses. [source]

    Bioaccumulation and ROS generation in liver of freshwater fish, goldfish Carassius auratus under HC Orange No. 1 exposure

    Yuanyuan Sun
    Abstract HC Orange No. 1 (CAS No. 54381-08-7, 2-nitro-4,-hydroxydiphenylamine) is used as a color additive in hair dyes. In this study, laboratory experiment was carried out to determine HC Orange No. 1 bioaccumulation and oxidative stress in the liver of freshwater fish, goldfish Carassius auratus. Fish were exposed to different concentrations (0.05, 0.1, 0.2, 0.5, and 1.0 mg/L) of HC Orange No. 1 for 10 days, with one group assigned as control. The accumulation of HC Orange No. 1 in liver increased with the exposure concentration (R2 = 0.94). A secondary spin trapping technique was used followed by electron paramagnetic resonance (EPR) analysis to study the reactive oxygen species (ROS) production. On the basis of the hyperfine splitting constants and shape of the EPR spectrum, the ROS generated in fish liver after exposure was identified as hydroxyl radical (,OH). There is a good correlation between the exposure concentrations and ,OH generation (R2 = 0.92). The ,OH signal intensity of the EPR spectrum showed a significant increase (P < 0.05) when the HC Orange No. 1 concentration was 1.0 mg/L, compared with that of the control. A good positive relationship (R2 = 0.95) was found between the ,OH formation and accumulation level of HC Orange No. 1 in liver. The changes of the activities of catalase (CAT), superoxide dismutase (SOD), glutathione S -transferase (GST), and contents of reduced glutathione (GSH) were also detected. These observations indicated a possible mechanism of oxidative stress induced by HC Orange No. 1 on fish. © 2007 Wiley Periodicals, Inc. Environ Toxicol 22: 256,263, 2007. [source]

    Aqueous photolysis of 8:2 fluorotelomer alcohol

    Suzanne A. Gauthier
    Abstract The 8:2 fluorotelomer alcohol (8:2 FTOH) was photodegraded in aqueous hydrogen peroxide solutions, synthetic field water (SFW) systems, and Lake Ontario (Canada) water samples. It was found to undergo indirect photolysis, with the data suggesting that the hydroxyl radical was the main degradation agent and that nitrate promoted photolysis whereas dissolved organic carbon inhibited it. The half-lives of 8:2 FTOH were 0.83 ± 0.20 h (10 mM H2O2), 38.0 ± 6.0 h (100 ,M H2O2), 30.5 ± 8.0 to 163.1 ± 3.0 h (SFW systems), and 93.2 ± 10.0 h (Lake Ontario). No significant loss of the parent compound by direct photolysis could be observed. The major monitored products were the 8:2 fluorotelomer aldehyde, the 8:2 fluorotelomer acid (8:2 FTCA), and perfluorooctanoate (PFOA); the minor monitored products were the 8:2 fluorotelomer unsaturated acid (8:2 FTUCA) and perfluorononanoate (PFNA). The intermediates, 8:2 FTCA and 8:2 FTUCA, were photodegraded to verify the degradation pathway, and a mechanism for the photolysis was proposed whereby the end products of the photolysis pathway were PFOA (major) and PFNA (minor). [source]

    Efficient DNA Cleavage Induced by Copper(II) Complexes of Hydrolysis Derivatives of 2,4,6-Tri(2-pyridyl)-1,3,5-triazine in the Presence of Reducing Agents

    Joaquķn Borrįs
    Abstract The reaction of 2,4,6-tri(pyridyl)-1,3,5-triazine (ptz) and copper(II) salts in dmf/water (1:1) results in the hydrolysis of ptz and formation of the anions bis(2-pyridylcarbonyl)amide (ptO2,) and bis(2-pyridylamine)amide (ptN2,), which are found in the complexes [Cu(ptN2)(OAc)]·3H2O (1), [Cu(ptO2)(OAc)(H2O)]·H2O (2), [Cu(ptN2)(for)]·3H2O (3) (for = formate), [Cu(ptO2)(for)(H2O)] (4), [Cu(ptO2)(benz)]·H2O (5) (benz = benzoate), and [Cu(ptO2)F(H2O)]2·3H2O (6). This report includes the chemical and spectroscopic characterization of all these complexes along with the crystal structures of 4,6. The coordination spheres of CuII in 4 and 5 are best described as distorted tetragonal square pyramidal for the former and distorted square planar for the latter. The crystal structure of 6 shows the presence of two discrete monomeric [Cu(ptO2)F(H2O)] entities in the crystallographic asymmetric unit in which both copper(II) ions have a distorted square-pyramidal coordination geometry. The binding of the complexes to DNA has been investigated with the aid of viscosity and thermal denaturation studies, both of which indicate that the interaction is probably due to the outer-sphere mechanism. The ability of the compounds to cleave DNA has also been tested. Efficient oxidative cleavage was observed in the presence of a mild reducing agent (ascorbate) and dioxygen. Mechanistic studies with reactive oxygen species (ROS) scavengers confirm that hydrogen peroxide, the hydroxyl radical, singlet oxygen-like species, and the superoxide anion are necessary diffusible intermediates in the scission process. A mechanism involving either the Fenton or theHaber,Weiss reaction plus the formation of copper oxene species is proposed for the DNA cleavage mediated by these compounds.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

    Fluorescent Gold Nanoprobe Sensitive to Intracellular Reactive Oxygen Species

    Hyukjin Lee
    Abstract Gold nanoprobes immobilized with fluorescein-hyaluronic acid (HA) conjugates are fabricated and utilized for monitoring intracellular reactive oxygen species (ROS) generation in live cells via nanoparticle surface energy transfer. A bio-inspired adhesive molecule, dopamine, is used to robustly end-immobilize HA onto the surface of gold nanoparticles (AuNPs) for securing intracellular stability against glutathione. ROS induces cleavage and fragmentation of the HA chains immobilized on the surface of the AuNPs allows rapid and specific detection of intracellular ROS by emitting strong fluorescence-recovery signals. In particular, fluorescence-quenched gold nanoprobes exhibit selective and dose-dependent fluorescence-recovery signals upon exposure to certain oxygen species such as superoxide anion () and hydroxyl radical (·OH). The fluorescent gold nanoprobe is usefully exploited for real-time intracellular ROS detection and antioxidant screening assay, and has exciting potential for various biomedical applications as a new class of ROS imaging probes. [source]

    Redox Properties of the Iron Complexes of Orally Active Iron Chelators CP20, CP502, CP509, and ICL670

    Martin Merkofer
    Redox cycling of iron is a critical aspect of iron toxicity. Reduction of a low-molecular-weight iron(III)-complex followed by oxidation of the iron(II)-complex by hydrogen peroxide may yield the reactive hydroxyl radical (OH.) or an oxoiron(IV) species (the Fenton reaction). Complexation of iron by a ligand that shifts the electrode potential of the complex to either to far below ,350,mV (dioxygen/superoxide, pH=7) or to far above +320,mV (H2O2/HO., H2O pH=7) is essential for limitting Fenton reactivity. The oral chelating agents CP20, CP502, CP509, and ICL670 effectively remove iron from patients suffering from iron overload. We measured the electrode potentials of the iron(III) complexes of these drugs by cyclic voltammetry with a mercury electrode and determined the dependence on concentration, pH, and stoichiometry. The standard electrode potentials measured are ,620,mV, ,600,mV, ,535,mV, and ,535,mV with iron bound to CP20, ICL670, CP502, and CP509, respectively, but, at lower chelator concentrations, electrode potentials are significantly higher. [source]

    Hepatocyte NAD(P)H oxidases as an endogenous source of reactive oxygen species during hepatitis C virus infection,

    HEPATOLOGY, Issue 1 2010
    Nabora Soledad Reyes de Mochel
    Oxidative stress has been identified as a key mechanism of hepatitis C virus (HCV),induced pathogenesis. Studies have suggested that HCV increases the generation of hydroxyl radical and peroxynitrite close to the cell nucleus, inflicting DNA damage, but the source of reactive oxygen species (ROS) remains incompletely characterized. We hypothesized that HCV increases the generation of superoxide and hydrogen peroxide close to the hepatocyte nucleus and that this source of ROS is reduced nicotinamide adenine dinucleotide phosphate (NAD(P)H) oxidase 4 (Nox4). Huh7 human hepatoma cells and telomerase-reconstituted primary human hepatocytes, transfected or infected with virus-producing HCV strains of genotypes 2a and 1b, were examined for messenger RNA (mRNA), protein, and subcellular localization of Nox proteins along with the human liver. We found that genotype 2a HCV induced persistent elevations of Nox1 and Nox4 mRNA and proteins in Huh7 cells. HCV genotype 1b likewise elevated the levels of Nox1 and Nox4 in telomerase-reconstituted primary human hepatocytes. Furthermore, Nox1 and Nox4 proteins were increased in HCV-infected human liver versus uninfected liver samples. Unlike Nox1, Nox4 was prominent in the nuclear compartment of these cells as well as the human liver, particularly in the presence of HCV. HCV-induced ROS and nuclear nitrotyrosine could be decreased with small interfering RNAs to Nox1 and Nox4. Finally, HCV increased the level of transforming growth factor beta 1 (TGF,1). TGF,1 could elevate Nox4 expression in the presence of infectious HCV, and HCV increased Nox4 at least in part through TGF,1. Conclusion: HCV induced a persistent elevation of Nox1 and Nox4 and increased nuclear localization of Nox4 in hepatocytes in vitro and in the human liver. Hepatocyte Nox proteins are likely to act as a persistent, endogenous source of ROS during HCV-induced pathogenesis. Hepatology 2010 [source]

    Thermochemistry for enthalpies and reaction paths of nitrous acid isomers

    Rubik Asatryan
    Recent studies show that nitrous acid, HONO, a significant precursor of the hydroxyl radical in the atmosphere, is formed during the photolysis of nitrogen dioxide in soils. The term nitrous acid is largely used interchangeably in the atmospheric literature, and the analytical methods employed do not often distinguish between the HONO structure (nitrous acid) and HNO2 (nitryl hydride or isonitrous acid). The objective of this study is to determine the thermochemistry of the HNO2 isomer, which has not been determined experimentally, and to evaluate its thermal and atmospheric stability relative to HONO. The thermochemistry of these isomers is also needed for reference and internal consistency in the calculation of larger nitrite and nitryl systems. We review, evaluate, and compare the thermochemical properties of several small nitric oxide and hydrogen nitrogen oxide molecules. The enthalpies of HONO and HNO2 are calculated using computational chemistry with the following methods of analysis for the atomization, isomerization, and work reactions using closed- and open-shell reference molecules. Three high-level composite methods G3, CBS-QB3, and CBS-APNO are used for the computation of enthalpy. The enthalpy of formation, ,Hof(298 K), for HONO is determined as ,18.90 ± 0.05 kcal mol,1 (,79.08 ± 0.2 kJ mol,1) and as ,10.90 ± 0.05 kcal mol,1 (,45.61 ± 0.2 kJ mol,1) for nitryl hydride (HNO2), which is significantly higher than values used in recent NOx combustion mechanisms. H-NO2 is the weakest bond in isonitrous acid; but HNO2 will isomerize to HONO with a similar barrier to the HONO bond energy; thus, it also serves as a source of OH in atmospheric chemistry. Kinetics of the isomerization is determined; a potential energy diagram of H/N/O2 system is presented, and an analysis of the triplet surface is initiated. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 378,398, 2007 [source]

    The hydroxyl radical reaction rate constant and products of 3,5-dimethyl-1-hexyn-3-ol,

    J. R. Wells
    A bimolecular rate constant,kDHO, of (29 ± 9) × 10,12 cm3 molecule,1 s,1 was measured using the relative rate technique for the reaction of the hydroxyl radical (OH) with 3,5-dimethyl-1-hexyn-3-ol (DHO, HCCC(OH)(CH3)CH2CH(CH3)2) at (297 ± 3) K and 1 atm total pressure. To more clearly define DHO's indoor environment degradation mechanism, the products of the DHO + OH reaction were also investigated. The positively identified DHO/OH reaction products were acetone ((CH3)2CO), 3-butyne-2-one (3B2O, HCCC(O)(CH3)), 2-methyl-propanal (2MP, H(O)CCH(CH3)2), 4-methyl-2-pentanone (MIBK, CH3C(O)CH2CH(CH3)2), ethanedial (GLY, HC(O)C(O)H), 2-oxopropanal (MGLY, CH3C(O)C(O)H), and 2,3-butanedione (23BD, CH3C(O)C(O)CH3). The yields of 3B2O and MIBK from the DHO/OH reaction were (8.4 ± 0.3) and (26 ± 2)%, respectively. The use of derivatizing agents O -(2,3,4,5,6-pentalfluorobenzyl)hydroxylamine (PFBHA) and N,O -bis(trimethylsilyl)trifluoroacetamide (BSTFA) clearly indicated that several other reaction products were formed. The elucidation of these other reaction products was facilitated by mass spectrometry of the derivatized reaction products coupled with plausible DHO/OH reaction mechanisms based on previously published volatile organic compound/OH gas-phase reaction mechanisms. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 534,544, 2004 [source]

    The inhibitory effect of the components of Cornus officinalis on melanogenesis

    Yasuhiko Nawa
    Five known compounds were isolated from a Cornus officinalis 50% ethanol extract (C. officinalis extract) and a hot water extract. We investigated the photochemical and pharmacological active compounds of C. officinalis hot water extract and ethanol extract. We understood that C. officinalis is a medicinal plant with potent free-radical-scavenging activity not only against reactive oxygen species (H2O2, superoxiside anion, hydroxyl radical, etc.) in a narrow sense, but also against many other free radicals (peroxynitrate, peroxyradical). It is estimated that the reduction effect with C. officinalis extract can block oxidative reaction on melanogenesis. Loganin and cornuside, the components in C. officinalis, showed a significant free-radical-scavenging activity and inhibitory effects on melanogenesis. We report to prove the inhibitory effect of UVB-induced pigmentation in C. officinalis extract through its radical scavenging activity. [source]

    Comparative study on composition and antioxidant properties of mint and black tea extract

    Ekambaram Padmini
    Summary The antioxidant properties of plants could be correlated with oxidative stress defence in different human diseases. The present study was undertaken to evaluate and compare the antioxidant potential and the phytochemical composition in the aqueous extracts of mint leaves, black tea and black tea enriched with mint extract. All the three preparations exhibited free radical-scavenging potential for nitric oxide (NO) radical, superoxide anion radical and hydroxyl radical, and the values were lesser than those of the antioxidants which acted as standards. In comparison, the mint extract exhibited higher free radical and NO scavenging effect. Hydroxyl radical and superoxide scavenging effects were more pronounced in tea with the mint extract, while the reducing power was exhibited more significantly by the black tea extract. The phytochemical compounds were identified and the total phenols and flavonoids were quantified and compared between these extracts. [source]

    Mechanisms underlying the inhibition of the cytochrome P450 system by copper ions

    M. E. Letelier
    Abstract Copper toxicity has been associated to the capacity of free copper ions to catalyze the production of superoxide anion and hydroxyl radical, reactive species that modify the structure and/or function of biomolecules. In addition, nonspecific Cu2+ -binding to thiol enzymes, which modifies their catalytic activities, has been reported. Cytochrome P450 (CYP450) monooxygenase is a thiol protein that binds substrates in the first and limiting step of CYP450 system catalytic cycle, necessary for the metabolism of lipophilic xenobiotics. Therefore, copper ions have the potential to oxidize and bind to cysteinyl residues of this monooxygenase, altering the CYP450 system activity. To test this postulate, we studied the effect of Cu2+ alone and Cu2+/ascorbate in rat liver microsomes, to independently evaluate its nonspecific binding and its pro-oxidant effects, respectively. We assessed these effects on the absorbance spectrum of the monooxygenase, as a measure of structural damage, and p -nitroanisole O -demethylating activity of CYP450 system, as a marker of functional impairment. Data obtained indicate that Cu2+ could both oxidize and bind to some amino acid residues of the CYP450 monooxygenase but not to its heme group. The differences observed between the effects of Cu2+ and Cu2+/ascorbate show that both mechanisms are involved in the catalytic activity inhibition of CYP450 system by copper ions. The significance of these findings on the pharmacokinetics and pharmacodynamics of drugs is discussed. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Oxidative stress during leukocyte absorption apheresis

    Aki Hirayama
    Abstract Leukocyte absorption apheresis absorbs leukocytes to the apheresis columns involving leukocyte activation. This process is regarded as bioincompatible and avoided in hemodialysis or other extracorporeal circulation processes. Thus, leukocyte apheresis has a potential risk to exacerbate in vivo oxidative stress. We evaluated the changes in plasma oxidative stress during leukocyte apheresis. Patients diagnosed as ulcerative colitis (UC) and treated with leukocyte apheresis were studied. Adacolumn (celluloseacetate beads) or Cellsorba EX (polyethylenephtarate fiber) was used for the leukocyte absorption device. Oxidative stress was measured by thiobarbituric acid reactive substances (TBARS) and hydroxyl radical (,OH) scavenging activity. Plasma samples were collected from the pre- and post-column sampling port at the start, and from the pre-column sampling port at the end of the treatment. The ,OH signal intensities (OHRI) significantly increased during a column passage, indicating a loss of plasma ,OH scavenging activity. However, OHRI was reduced at the end, suggesting a recovery of radical scavenging activity during leukocyte apheresis. Significant decreases of OHRI and TBARS were only observed in the early phase of the therapeutic course. No differences of OHRI and TBARS levels were observed between the two columns. These results indicate that though the plasma antioxidant activity was diminished by a column passage, plasma antioxidant activity recovers during the procedure. This efficient antioxidative effect is limited to the early phase of the therapeutic course. J. Clin. Apheresis 18:61,66, 2003. © 2003 Wiley-Liss, Inc. [source]


    Methanolic extracts from the seed coats of five major tamarinds (Srichomphu, Sithong-nak, Sithong-bao, Priao-yak and Khanti) cultivated in Thailand were investigated for their content of phenolic compounds and their antioxidative properties. Antioxidative properties were evaluated by various different methods: scavenging effect on the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl radical, anti-lipid peroxidation and reducing power assay. The phenolic compound contents were determined by spectrophotometric methods. Extract of Priao-yak with the highest tannin content showed the strongest reducing power, while extract of Khanti with the highest proanthocyanidin content revealed high scavenging ability on both DPPH and hydroxyl radicals. Stronger antioxidative activity measured by most assays was noted for the extract of Sithong-bao with a high content of total phenols, proanthocyanidin and tannins. The results suggest that specific phenolic constituents in the extract could be responsible for the different antioxidant properties observed in different cultivars. Furthermore, seed coat extract of Sithong-bao may be a potential source of natural antioxidant to be developed into nutraceuticals. PRACTICAL APPLICATIONS Components of Tamarindus indica L., a tree indigenous to India and South-East Asia, have long been used as a spice, food component and traditional medicine. According To traditional medicine, the tamarind pulp is used as a digestive, carminative, laxative, expectorant and blood tonic; the seeds are used as an anthelmintic, antidiarrheal and emetic. In addition, the seed coat is used to treat burns and aid wound healing as well as as an antidysenteric. Recent studies have demonstrated polyphenolic constituents with more potent antioxidant and anti-inflammatory activities of T. indica seed coat extract. Therefore, seed coat extracts of T. indica have economic potential for development into health promotion products as well as natural preservatives to increase the shelf life of food by preventing lipid peroxidation. [source]


    ABSTRACT The potential antioxidant activity of enzymatic extracts from Picrorrhiza kurroa was evaluated on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical, hydroxyl radical and alkyl radical-scavenging activities using an electron spin resonance spectrometer (JEOL Ltd., Tokyo, Japan). P. kurroa was enzymatically hydrolyzed by seven carbohydrases and five proteases to prepare water-soluble extracts. The DPPH radical-scavenging activities of the pancreatic trypsin and Amyloglucosidase (AMG) (artificial carbohydrase by Novozyme Nordisk, Bagsvaerd, Denmark) extracts from P. kurroa were the highest among protease and carbohydrase extracts, and 50% inhibitory concentration (IC50) values were 35.58 and 29.03 µg/mL, respectively. The hydroxyl radical-scavenging activity of the Protamex and Viscozyme extracts from P. kurroa were the highest scavenging activities, and the IC50 values were 0.46 and 1.89 mg/mL, respectively. In addition, the Protamex and Maltogenase extracts from P. kurroa showed the highest alkyl radical-scavenging activities, and the IC50 values were 18.03 and 10.66 µg/mL, respectively. The protective effect of the Protamex extracts from P. kurroa on DNA damage which was free radical-induced was 92% at 3 mg/mL. These results indicate that enzymatic extracts of P. kurroa show potent antioxidant activity. PRACTICAL APPLICATIONS Picrorrhiza kurroa could be used to produce protein and carbohydrate extracts with antioxidative activity. Many industrial commercial enzymes such as Promozyme, Celluclast 1.5 L FG, Maltogenase L, Viscozyme L, Termamyl SC, Dextrozyme E, AMG 300 L, Protamex, Flavourzyme 500 MG, Neutrase 0.8 L, Pancreatic Trypsin and Alcalase 2.4 L could be also used to attain the extracts processing the high antioxidative activity. The extracts can be used as natural antioxidants. [source]


    ABSTRACT This study compared the free radical-scavenging properties of chondroitin sulfate (ChS) from pig laryngeal cartilage and its reduced or sulfonated derivatives. The binding behavior between Cu2+ and ChS and its derivatives, and the interaction between superoxide radical and ChS were studied by fluorescence quenching, equilibrium dialysis, infrared spectra and thermal analysis. Purified ChS inhibited the generation of hydroxyl radical and scavenged superoxide radical in a concentration-dependent manner. Reduced ChS did not scavenge hydroxyl radical and superoxide radical. Sulfonated ChS had no hydroxyl radical scavenging activity but scavenged superoxide radical as strongly as purified ChS. ChS showed strong binding activity with Cu2+ in deionized water but not in 0.01-M HCl. Both reduced ChS and sulfonated ChS did not exhibit such chelating behavior. The structural basis of hydroxyl radical inhibiting of ChS was attributed to a complex of the Cu2+ with the carboxyl group of glucuronic acid residue. The reaction of superoxide radical with the sulfate ester and the carboxyl group may be the basis of superoxide radical scavenging activity of ChS. [source]


    ABSTRACT We tested the antioxidant properties of both aqueous and methanolic extracts of oregano (origanum vulgare) They proved to be effective in the inhibition of all phases of the peroxidative process: first neutralizing free radicals (superoxide anion, hydroxyl radical and 1,1-diphenyl-2-picrylhydrazyl radical), then blocking peroxidation catalysis by iron (through iron-chelating and iron-oxidizing properties), and finally through interruption of lipid-radical chain reactions (chain-breaking activity). Their anti-glycosylation activity was also effective. The glycosylation oflipoproteins is directly related to their peroxidation. The amount of extract used in our experiments was obtained from 0.1,1 mg of dried leaves, amounts far less than those normally used in the Mediterranean diet. [source]

    Reactivity of Tyr,Leu and Leu,Tyr dipeptides: identification of oxidation products by liquid chromatography,tandem mass spectrometry

    Conceiēćo Fonseca
    Abstract The exposure of peptides and proteins to reactive hydroxyl radicals results in covalent modifications of amino acid side-chains and protein backbone. In this study we have investigated the oxidation the isomeric peptides tyrosine,leucine (YL) and leucine,tyrosine (LY), by the hydroxyl radical formed under Fenton reaction (Fe2+/H2O2). Through mass spectrometry (MS), high-performance liquid chromatography (HPLC-MS) and electrospray tandem mass spectrometry (HPLC-MSn) measurements, we have identified and characterized the oxidation products of these two dipeptides. This approach allowed observing and identifying a wide variety of oxidation products, including isomeric forms of the oxidized dipeptides. We detected oxidation products with 1, 2, 3 and 4 oxygen atoms for both peptides; however, oxidation products with 5 oxygen atoms were only present in LY. LY dipeptide oxidation leads to more isomers with 1 and 2 oxygen atoms than YL (3 vs 5 and 4 vs 5, respectively). Formation of the peroxy group occurred preferentially in the C -terminal residue. We have also detected oxidation products with double bonds or keto groups, dimers (YL,YL and LY,LY) and other products as a result of cross-linking. Both amino acids in the dipeptides were oxidized although the peptides showed different oxidation products. Also, amino acid residues have shown different oxidation products depending on the relative position on the dipeptide. Results suggest that amino acids in the C -terminal position are more prone to oxidation. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Protective effect of Hachimi-jio-gan against renal failure in a subtotal nephrectomy rat model

    Noriko Yamabe
    The protective effect of Hachimi-jio-gan extract against chronic renal failure in a subtotal nephrectomy rat model was investigated. The level of serum urea nitrogen by nephrectomy was increased over 15 weeks, but the administration of Hachimi-jio-gan at 50 and 200 mg led to the decrease. In addition, the levels of creatinine (Cr), urinary methylguanidine (MG) and MG/Cr were increased, whereas Cr clearance dramatically decreased in nephrectomized rats. However, oral administration of Hachimi-jio-gan extract prevented the elevation of these uremic toxins in serum and urine, and the production of hydroxyl radical. Moreover, nephrectomy led to a significant decline in superoxide dismutase (SOD) and catalase activities, but increased glutathione peroxidase activity compared with normal levels, indicating an abnormal antioxidative system. The increased activity of both SOD and catalase by the oral administration of Hachimi-jio-gan suggested that these enzymes are associated with the protective role of Hachimi-jio-gan extract against oxidative stress by nephrectomy. Moreover, the decrease in serum albumin in nephrectomized control rats was increased and proteinuria was ameliorated by the administration of Hachimi-jio-gan with improved glomerular hyalinosis, interstitial fibrosis and inflammation, suggesting the beneficial effect of Hachimi-jio-gan to prevent glomerular sclerosis and progressive renal fibrosis. This study suggests that Hachimi-jio-gan plays a protective role in the progression of chronic renal failure through the decline in uremic toxins, elevation of antioxidative enzyme activity such as SOD and catalase, and amelioration of histopathological lesions in the kidney. [source]

    Effects of melatonin on paraquat or ultraviolet light exposure-induced DNA damage

    Hiro-aki Yamamoto
    The effect of paraquat or ultraviolet (UV) light exposure on calf thymus DNA was investigated in vitro. When paraquat (0.1, 0.25, 0.5, or 1.0 mM) was incubated with brain or lung homogenates prepared from mice in the presence of calf thymus DNA at 37°C for 90 min, paraquat inflicted damage to DNA in a concentration-dependent manner. However, DNA damage was completely abolished by co-treatment with melatonin (1.5 mM), a hydroxyl radical (,OH) scavenger. In addition, when paraquat (1.0 or 2.5 mM) was incubated with liver microsomes in the presence of calf thymus DNA and Fe3+ (3.0 ,M) at 37°C for 90 min, DNA damage also occurred and was prevented by the co-treatment of melatonin (1.5 mM). DNA was also damaged by UV light exposure or when the Fenton reaction was induced; the Fenton reaction generates ,OH; again, the damage was blocked by the co-treatment of melatonin. These results suggest that ,OH induced by paraquat or UV light probably account for the DNA damage. In short, DNA damage induced by paraquat and UV radiation were completely prevented by co-treatment with the ,OH scavenger, melatonin. [source]

    Scirpusin A, a hydroxystilbene dimer from Xinjiang wine grape, acts as an effective singlet oxygen quencher and DNA damage protector

    Qingjun Kong
    Abstract BACKGROUND: Grapes and red wines are rich sources of phenolic compounds such as anthocyanins, catechins, flavonols and stilbenes, most of which are potent antioxidants showing cardioprotective properties. We first isolated scirpusin A, a hydroxystilbene dimer, from a wine grape of Xinjiang, and studied its antioxidant activity. RESULTS: Reactive oxygen species scavenging effects and the protection against reactive singlet oxygen-induced DNA damage of scirpusin A have been investigated in our experiments. The concentration of scirpusin A required to inhibit 50% of 1O2 generation was 17 µmol L,1, while addition of scirpusin A at 140 µmol L,1 caused complete inhibition. Further kinetic study revealed that the reaction of Scirpusin A with singlet oxygen has an extremely high rate constant (ka = 4.68 × 109 L mol,1 s,1). Scirpusin A (140 µmol L,1) exhibited significant inhibition effects on pBR322 DNA breakage. However, scavenging effects of scirpusin A on superoxide anion O2,, and hydroxyl radical ·OH were not potent as the inhibitor rates at a concentration of 1400 µmol L,1 were 28.83% and 19.5%, respectively. CONCLUSION: The present study shows that scirpusin A is a selective quencher of singlet oxygen and a protector against reactive singlet oxygen-induced pBR322 DNA damage at very low concentrations. Copyright © 2010 Society of Chemical Industry [source]