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Efeito da flutuação da disponibilidade de oxigênio e da privação alimentar sobre o metabolismo de radicais livres; Effect of fluctuation of oxygen availability and food deprivation on free radical metabolism

Welker, Alexis Fonseca
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 17/07/2009 PT
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56.14%
Muitas espécies de animais vivenciam situações nas quais há uma profunda depressão metabólica, como na anóxia, na hipóxia e na hibernação. Durante a reoxigenação ou o despertar, ocorre aumento da produção de espécies reativas de oxigênio (ROS), que tendem a causar danos oxidativos. Diferentes enzimas antioxidantes protegem o organismo contra as ROS, porém não se sabe qual a real importância de cada uma delas durante a reoxigenação. A hibernação é uma das formas de hipometabolismo menos estudadas, fazendo com que haja questionamentos sobre como os hibernantes se protegem das ROS durante o despertar. A análise dos dados existentes é complexa devido à existência de variáveis não controladas, como o efeito do jejum associado à hibernação. Nesta tese, foram desenvolvidos dois projetos. Em um, investigou-se a importância da catalase num ciclo de anóxia e reoxigenação em caramujos pulmonados. No segundo, investigou-se o efeito da hibernação e da privação alimentar no intestino de lagartos teiús. Com base nos resultados, foi possível concluir que a catalase exerce um papel complementar contra os danos oxidativos causados pelas ROS e em conjunto com os demais componentes do sistema antioxidante. Porém...

CH and C2 radicals characterization in natural gas turbulent diffusion flames

Martins, C. A.; Pimenta, A. P.; Carvalho, J. A.; Ferreira, M. A.; Caldeira-Pires, A. A.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 110-117
ENG
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This paper reports the construction of an axisymmetric nonpremixed piloted jet burner, with well-defined initial and boundary conditions, known as the Delft burner, to assess turbulence-chemistry interaction in non-premixed turbulent flames. Detailed experimental information is described, involving hot-wire anemometry, thin-wire thermocouples and chemiluminescence visualization measurements. Radial profile of the axial mean velocity indicates excellent agreement between flow patterns developed within Delft installation and the one described herein. Chemiluminescence emissions from CH and C2 free-radicals were acquired with a CCD camera. Tomography reconstruction analysis was utilised to compare radical emissions and temperature spatial distributions. There was a strong dependence between temperature and CH/C 2 emissions. This is an indication that these radicals can be used in flame front studies.

Preliminary in vitro and ex vivo evaluation of afzelin, kaempferitrin and pterogynoside action over free radicals and reactive oxygen species

Vellosa, José Carlos Rebuglio; Regasini, Luis Octavio; Belló, Caroline; Schemberger, Josiane Aparecida; Khalil, Najeh Maissar; Morandim-Giannetti, Andreia De Araújo; Bolzani, Vanderlan da Silva; Brunetti, Iguatemy Lourenço; Oliveira, Olga Maria Mascar
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica
ENG
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66.24%
Biological activities of flavonoids have been extensively reviewed in literature. The biochemical profile of afzelin, kaempferitrin, and pterogynoside acting on reactive oxygen species was investigated in this paper. The flavonoids were able to act as scavengers of the superoxide anion, hypochlorous acid and taurine chloramine. Although flavonoids are naturally occurring substances in plants which antioxidant activities have been widely advertised as beneficial, afzelin, kaempferitrin, and pterogynoside were able to promote cytotoxic effect. In red blood cells this toxicity was enhanced, depending on flavonoids concentration, in the presence of hypochlorous acid, but reduced in the presence of 2,20 -azo-bis(2-amidinopropane) free radical. These flavonoids had also promoted the death of neutrophils, which was exacerbated when the oxidative burst was initiated by phorbol miristate acetate. Therefore, despite their well-known scavenging action toward free radicals and oxidants, these compounds could be very harmful to living organisms through their action over erythrocytes and neutrophils.

EPR study of gamma induced radicals in amino and iminodiacetic acid derivatives

Aydin,Murat; Baskan,M. Halim; Emre Osmanoglu,M. Y.
Fonte: Sociedade Brasileira de Física Publicador: Sociedade Brasileira de Física
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2009 EN
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56.41%
In this study, electron paramagnetic resonance spectroscopy was used to investigate free radicals formed in gamma irradiated L-glutamine hydrochloride, iminodiacetic acid hydrochloride and N-(2-hyroxyethyl) iminodiacetic acid powders. The free radicals produced in L-glutamine hydrochloride powders were attributed to the CH2CHCOOH radical; and those in iminodiacetic acid hydrochloride and N-(2-hyroxyethyl) iminodiacetic acid powders to the HNCHCH2(COOH)2 and HOCH2CH2NCHCH2(COOH)2, respectively. The g-values of the radicals and the hyperfine structure constants of the free electron with the environmental protons and 14N nucleus were determined. The samples were not displayed before they were not irradiated. The free radicals were found stable at room temperature for more than six months. Some spectroscopic properties and suggestions concerning possible structure of the radicals are discussed in this paper.

Identification of free radicals induced by gamma irradiation in amino acid derivatives

Aydin,Murat
Fonte: Sociedade Brasileira de Física Publicador: Sociedade Brasileira de Física
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2010 EN
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66.41%
Powders of N- acetyl- L- leucine and N- methyl- L- glutamic acid were gamma irradiated and the free radicals formed were investigated at room temperature by electron paramagnetic resonance technique. The free radicals formed in compounds were attributed to the (CH3)2CCH2CH(NHCOCH3)COOH and HOOCCH2CH2C (NHCH3)COOH radicals respectively. Both radicals are very stable and we could observe them for five months without almost intensity diminution at room temperature. The g values of the radicals and the hyperfine structure constants of the free electron with nearby protons and 14N nucleus were determined. The results were found to be in good agreement with the existing literature data.

Study of the structure of free radicals in gamma: irradiated amino acid derivatives

Aydin,Murat
Fonte: Sociedade Brasileira de Física Publicador: Sociedade Brasileira de Física
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2010 EN
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66.39%
Electron paramagnetic resonance spectroscopy has been used for the study of the free radicals produced in the powders of L-arginine monohydrochloride, ala-ala and DL-β-leucine gamma-irradiated at room temperature. The structures of the radicals formed in compounds were determined as NH2(NH)NHCHCH2CH2CH(NH2)COOH, CH3CHCOOH and (CH3)2C CH(NH2)CH2COOH respectively. The paramagnetic species were found to be stable at room temperature more than three months. It was determined that unpaired electron interacted with nearby protons and 14N nucleus in these radicals. The g values of the radicals and the hyperfine structure constants of the free electron were also measured. These results were compared with the earlier studies in amino acid and derivatives radicals and discussed.

Profile of Maytenus aquifolium action over free radicals and reactive oxygen species

Vellosa,José Carlos Rebuglio; Barbosa,Vanessa de Frias; Khalil,Najeh Maissar; Santos,Vânia Aparecida de Freitas Formenton Macedo dos; Furlan,Maysa; Brunetti,Iguatemy Lourenço; Oliveira,Olga Maria Mascarenhas de Faria
Fonte: Divisão de Biblioteca e Documentação do Conjunto das Químicas da Universidade de São Paulo Publicador: Divisão de Biblioteca e Documentação do Conjunto das Químicas da Universidade de São Paulo
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2007 EN
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66.34%
Reactive oxygen species (ROS) and free radical species have been implicated in initiating, accompanying or causing many diseases in living organisms; there is thus, a continual need for antioxidants molecules to inactivate ROS/free radicals. Many studies of plants crude extracts have demonstrated free-radical scavenging and antioxidant action. Maytenus species have long been used, in several countries, as traditional medicines against gastric ulcers, dyspepsia and others gastric problems and for their anti-inflammatory properties. In this study, Maytenus aquifolium (Celastraceae) root bark ethanol extract was assessed for its ability to scavenge free radicals and reactive oxygen species. The results were expressed as percentage inhibition of the active species. The extract was efficient against studied reactive species: DPPH radical (obtained inhibition = 35.5 ± 1.3 %), ABTS•+ (IC50 = 0.0036 ± 0.0003 mg/mL), HOCl (IC50 = 0.002 ± 0.0001 mg/mL ), O2•- (obtained inhibition = 36.0 ± 2.1 %), and NO• (obtained inhibition = 18.3 ± 0.4 %).

Scavenging Effects of Dexrazoxane on Free Radicals

Junjing, Zhang; Yan, Zhao; Baolu, Zhao
Fonte: the Society for Free Radical Research Japan Publicador: the Society for Free Radical Research Japan
Tipo: Artigo de Revista Científica
EN
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56.35%
Dexrazoxane (ICRF-187) has been clinically used to reduce doxorubicin-induced cardiotoxicity for more than 20 years. It has been proposed that dexrazoxane may act through its rings-opened hydrolysis product ADR-925, which can either remove iron from the iron-doxorubicin complex or bind to free iron, thus preventing iron-based oxygen radical formation. However, it is not known whether the antioxidant actions of dexrazoxane are totally dependent on its metabolization to its rings-opened hydrolysis product and whether dexrazoxane has any effect on the iron-independent oxygen free radical production. In this study, we examined the scavenging effect of dexrazoxane on hydroxyl, superoxide, lipid, DPPH and ABTS+ free radicals in vitro solution systems. The results demonstrated that dexrazoxane was an antioxidant that could effectively scavenge these free radicals and the scavenging effects of dexrazoxane did not require the enzymatic hydrolysis. In addition, dexrazoxane was capable to inhibit the generation superoxide and hydroxyl radicals in iron free reaction system, indicating that the antioxidant properties of dexrazoxane were not solely dependent on iron chelation. Thus the application of dexrazoxane should not be limited to doxorubicin-induced cardiotoxicity. Instead...

Do free radicals play causal role in atherosclerosis? Low density lipoprotein oxidation and vitamin E revisited

Niki, Etsuo
Fonte: the Society for Free Radical Research Japan Publicador: the Society for Free Radical Research Japan
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
56.34%
Lipid peroxidation induced by free radicals has been implicated in the pathogenesis of various diseases. Numerous in vitro and animal studies show that oxidative modification of low density lipoprotein (LDL) is an important initial event of atherosclerosis. Vitamin E and other antioxidants inhibit low density lipoprotein oxidation efficiently in vitro, however, human clinical trials with vitamin E have not yielded positive results. The mixed results for vitamin E effect may be ascribed primarily to the two factors. Firstly low density lipoprotein oxidation proceeds by multiple pathways mediated not only by free radicals but also by other non-radical oxidants and vitamin E is effective only against free radical mediated oxidation. Secondly, in contrast to animal experiments, vitamin E is given at the latter stage where oxidation is no more important. Free radicals must play causal role in pathogenesis of atherosclerosis and vitamin E should be effective if given at right time to right subjects.

Iron regulation by hepatocytes and free radicals

Takami, Taro; Sakaida, Isao
Fonte: the Society for Free Radical Research Japan Publicador: the Society for Free Radical Research Japan
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
56.39%
Iron is an essential metallic microelement for life. However, iron overload is toxic. The liver serves an important role as a storehouse for iron in the body. About 20–25 mg of iron is required each day for hemoglobin synthesis. To maintain iron homeostasis, transferrin and transferrin receptors are primarily involved in the uptake of iron into hepatocytes, ferritin in its storage, and ferroportin in its export. Moreover, hepcidin controls ferroportin and plays a central role in the iron metabolism. Excess “free” reactive iron produces damaging free radicals via Fenton or Harber-Weiss reactions. Produced free radicals attack cellular proteins, lipids and nucleic acid. Several detoxification system and anti-oxidant defense mechanisms exist to prevent cellular damage by free radicals. Excessive free radicals can lead to hepatocellular damage, liver fibrosis, and hepatocarcinogenesis.

Environmentally Persistent Free Radicals (EPFRs) - 2. Are Free Hydroxyl Radicals Generated in Aqueous Solutions?

Khachatryan, Lavrent; Dellinger, Barry
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
46.48%
A chemical spin trap, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), in conjunction with electron paramagnetic resonance (EPR) spectroscopy was employed to measure the production of hydroxyl radical (.OH) in aqueous suspensions of 5% Cu(II)O/silica (3.9% Cu) particles containing environmentally persistent free radicals (EPFRs) of 2-monochlorophenol (2-MCP). The results indicate: 1) a significant differences in accumulated DMPO-OH adducts between EPFR containing particles and non-EPFR control samples, 2) a strong correlation between the concentration of DMPO-OH adducts and EPFRs per gram of particles, and 3) a slow, constant growth of DMPO-OH concentration over a period of days in solution containing 50 μg/ml EPFRs particles + DMPO (150 mM) + reagent balanced by 200 μl phosphate buffered (pH = 7.4) saline. However, failure to form secondary radicals using standard scavengers, such as ethanol, dimethylsulfoxide, sodium formate, and sodium azide, suggests free hydroxyl radicals may not have been generated in solution. This suggests surface-bound, rather than free, hydroxyl radicals were generated by a surface catalyzed-redox cycle involving both the EPFRs and Cu(II)O. Toxicological studies clearly indicate these bound free radicals promote various types of cardiovascular and pulmonary disease normally attributed to unbound free radicals; however...

Platelet protein damage by free radicals and glycationin vitro: The pathological consequences

Goswami, K.; Bhatla, B. D.; Shankar, R.
Fonte: Springer India Publicador: Springer India
Tipo: Artigo de Revista Científica
Publicado em /08/2000 EN
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66.2%
Modification of platelet proteins by free radicals and glycation has been studied in the present work, as anin vitro model. The results of the two parameters, SDS-PAGE and carbonylation study are quite corroborative. We observed that the inducers like ferrous sulphate, ascorbate (mainly in supraphysiological concentration) and glucose attack the protein in a dose dependent manner, of which ferrous sulphate is most potent. Proteins from aged and degenerative conditions like malignancy and diabetes mellitus have suffered greater damage than normal adult and foetal proteins. The individual life expectancy in terms of biological versus chronological age may also be worked out from the individual stress level.

Distribution and Evolution of Free Radicals in DNA and Protein Powders: Multiple-Track Radiation Chemistry

Black, Paul J. (1985 - ); Bernhard, William A. ; Gunter, Thomas E.
Fonte: University of Rochester Publicador: University of Rochester
Tipo: Tese de Doutorado
ENG
Relevância na Pesquisa
66.2%
Thesis (Ph.D.)--University of Rochester. School of Medicine & Dentistry. Dept. of Biochemistry and Biophysics, 2012.; For decades the effect of ionizing radiation on DNA has been an active field of research. Understanding the fundamental mechanisms of radiation damage to DNA is essential for predicting damage distribution in biologically relevant sequences and for the development of important medical applications, such as increasing radiation therapy efficacy. The chemical reactions that result from the direct deposition of energy from ionizing radiation into DNA are known as direct-type radiation damage. This can be further categorized as single-track or multiple-track, depending on the average number of radiation tracks that a target is exposed to. To date a large amount of work has been focused on the initial events resulting from low radiation doses, which produce predominantly single-track radiation chemistry. In this study, Electron Paramagnetic Resonance (EPR) spectra of oligodeoxynucleotide (ODN) powders were collected after x-irradiating samples over a large dose range (2-400 kGy) in order to follow both single- and multiple-track radiation chemistry in a controlled manner. Principle component analysis of EPR spectra from samples exposed to low doses (2-50 kGy) yielded important results on the initial distribution of free radicals caused by single-track events and revealed important charge transfer properties in addition to identifying an electron scavenging contaminant found in synthesized DNA oligomers. EPR spectra of ODN powders at high dose (400 kGy) allowed the study of complex damage that occurs in radiation spurs where multiple-track events are likely. These results were used to develop a comprehensive model for single- and multiple-track radical chemistry in organic molecules. This model was also applied to proteins where it gave new insights into the mechanism of crystal death and...

Oxygen free radicals in medicine (I).; Radicais livres do oxigénio em medicina (1. Parte).

Ribeiro, L M
Fonte: Ordem dos Médicos Publicador: Ordem dos Médicos
Tipo: info:eu-repo/semantics/article; article; article; info:eu-repo/semantics/publishedVersion Formato: application/pdf
Publicado em 30/04/1989 POR
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Free radicals are highly reactive molecules, and therefore transient, which have an odd number of electrons and are generated in vivo as byproducts of normal metabolism. In this review we survey basic concepts on the chemistry of oxygen free radicals, their cellular sources and the reactions they can undergo. We also discuss the cellular defenses against free radicals induced damage. The disfunction induced by free radicals may thus be a major component of several pathological conditions. The critical role played by free radicals in ageing, carcinogenesis, reperfusion injury and and respiratory distress is reviewed.; Free radicals are highly reactive molecules, and therefore transient, which have an odd number of electrons and are generated in vivo as byproducts of normal metabolism. In this review we survey basic concepts on the chemistry of oxygen free radicals, their cellular sources and the reactions they can undergo. We also discuss the cellular defenses against free radicals induced damage. The disfunction induced by free radicals may thus be a major component of several pathological conditions. The critical role played by free radicals in ageing, carcinogenesis, reperfusion injury and and respiratory distress is reviewed.

Oxygen free-radicals in medicine (2).; Radicais livres do oxigénio em medicina (2. parte).

Ribeiro, L M
Fonte: Ordem dos Médicos Publicador: Ordem dos Médicos
Tipo: info:eu-repo/semantics/article; article; article; info:eu-repo/semantics/publishedVersion Formato: application/pdf
Publicado em 30/06/1989 POR
Relevância na Pesquisa
46.52%
Free radicals are highly reactive molecules, and therefore transient, which have an odd number of electrons and are generated in vivo as byproducts of normal metabolism. In this review we survey basic concepts on the chemistry of oxygen free radicals, their cellular sources and the reactions they can undergo. We also discuss the cellular defenses against free radicals induced damage. The disfunction induced by free radicals may thus be a major component of several pathological conditions. The critical role played by free radicals in ageing, carcinogenesis, reperfusion injury and respiratory distress is reviewed.; Free radicals are highly reactive molecules, and therefore transient, which have an odd number of electrons and are generated in vivo as byproducts of normal metabolism. In this review we survey basic concepts on the chemistry of oxygen free radicals, their cellular sources and the reactions they can undergo. We also discuss the cellular defenses against free radicals induced damage. The disfunction induced by free radicals may thus be a major component of several pathological conditions. The critical role played by free radicals in ageing, carcinogenesis, reperfusion injury and respiratory distress is reviewed.

A Protocol for Detecting and Scavenging Gas-phase Free Radicals in Mainstream Cigarette Smoke

Yu, Long-Xi; Dzikovski, Boris G.; Freed, Jack H.
Fonte: MyJove Corporation Publicador: MyJove Corporation
Tipo: Artigo de Revista Científica
Publicado em 02/01/2012 EN
Relevância na Pesquisa
46.48%
Cigarette smoking is associated with human cancers. It has been reported that most of the lung cancer deaths are caused by cigarette smoking 5,6,7,12. Although tobacco tars and related products in the particle phase of cigarette smoke are major causes of carcinogenic and mutagenic related diseases, cigarette smoke contains significant amounts of free radicals that are also considered as an important group of carcinogens9,10. Free radicals attack cell constituents by damaging protein structure, lipids and DNA sequences and increase the risks of developing various types of cancers. Inhaled radicals produce adducts that contribute to many of the negative health effects of tobacco smoke in the lung3. Studies have been conducted to reduce free radicals in cigarette smoke to decrease risks of the smoking-induced damage. It has been reported that haemoglobin and heme-containing compounds could partially scavenge nitric oxide, reactive oxidants and carcinogenic volatile nitrosocompounds of cigarette smoke4. A 'bio-filter' consisted of haemoglobin and activated carbon was used to scavenge the free radicals and to remove up to 90% of the free radicals from cigarette smoke14. However, due to the cost-ineffectiveness, it has not been successfully commercialized. Another study showed good scavenging efficiency of shikonin...

Alteraciones en los lípidos nucleares hepáticos debidas a la activación in situ del tetracloruro de carbono a radicales libresAlterations in hepatic nuclear lipids due to in situ carbon tetrachloride activation to free radicals.

Fanelli, Silvia Laura
Fonte: Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires Publicador: Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires
Tipo: info:eu-repo/semantics/doctoralThesis; tesis doctoral; info:eu-repo/semantics/publishedVersion Formato: application/pdf
Publicado em //1996 SPA
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66.43%
Se evidenció que a partir de la activación nuclear hepática del tetracloruro de carbono (CCl4) se forman radicales libres triclorometilo (*CCl3). Los radicales *CC13 y los CCl3O2* derivados de la reacción de los primeros con el oxígeno, promueven reacciones de adición y de abstracción de H desde los lípidos nucleares. Las reacciones de adición son más intensas con los *CCl3 ; mientras que las de abstracción de H son promovidas más fuertemente por los CCl302*. Los *CCl3 se adicionan preferentemente a los ácidos grasos poliinsaturados de los fosfolípidos (PUFA) de la membrana perinuclear. Los CCl3O2* y los *CCl3 abstraen hidrógenos de los PUFA (especialmente ac. araquidónico) e inician procesos de peroxidación de lípidos de la membrana perinuclear que conducen a la formación de aldehídos reactivos (ej. malondialdehído). También abstraen H del colesterol de la membrana perinuclear formando productos de oxidación y cetoderivados del mismo. Por estudio comparativo en dos cepas de ratas con distinta susceptibdidad a sufrir cáncer hepático por efecto del CCl4, se deduce que la intensidad de producción de los radicales *CCl3 en las cercanías del ADN y la unión covalente de los mismos a fosfolípidos específicos...

DPPH and oxygen free radicals as pro-oxidant of biomolecules

Miranda, Dante; Montoya, Margarita; Holst, Marianne; Cortés Troncoso, Juan; Molina Berríos, Alfredo; González Lira, Víctor Manuel; Jara Sandoval, José; Palma, Karina; Letelier Muñoz, María Eugenia
Fonte: PERGAMON-ELSEVIER SCIENCE LTD Publicador: PERGAMON-ELSEVIER SCIENCE LTD
Tipo: Artículo de revista
EN
Relevância na Pesquisa
66.38%
Numerous investigations exist about the alterations that oxygen free radicals can provoke on biomolecules; these modifications can be prevented and/or reversed by different antioxidants agents. On the other hand, 2,2-diphenyl-1-picrylhydrazyl radical (DPPH), a stable nitrogen synthetic radical, is used to evaluate the antioxidant capacity of medicinal herbal products; however, the structural changes that this radical provoke on the herbal active principles are not clear yet. In this work, we compared the redox reactivity of oxygen free radicals and DPPH radical on phospholipids and protein thiol groups present in rat liver microsomes. Cu2+/ascorbate was used as generator system of oxygen free radical and as antioxidant, an extract of Buddleja globosa’s leaves. Cu2+/ascorbate provoked microsomal lipid peroxidation, microsomal thiols oxidation and oxygen consumption; all of these phenomena were inhibited by B. globosa extract. On the other hand, DPPH was bleached in different extension by the herbal extract and phosphatidyl choline; beside, DPPH decreased microsomal thiols content, but this phenomenon were not prevented by the herbal extract. Furthermore, DPPH did not induce oxygen consumption and neither modified the oxygen consumption induced by Cu2+/ascorbate. Distinct redox mechanisms may explain the differences between the reactivity of DPPH and oxygen free radicals on biomolecules...

Factors affecting the rates of addition of free radicals to alkenes?Determination of absolute rate coefficients using the persistent aminoxyl method.

Beckwith, Athelstan (Athel); Poole, James
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
56.3%
The rate of coupling of alkyl radicals with the persistent aminoxyl radical 1,1,3,3-tetramethyl-isoindolin-N-oxyl (1) has been used as a kinetic probe to determine absolute rate coefficients for the addition of alkyl radicals to methyl acrylate. The results are discussed in terms of the role of the structure and functionalization of the attacking radical on the rates of addition, particularly as they affect steric, polar, and enthalpic factors. The aminoxyl method is assessed against other methods for determining free radical addition rate coefficients.

Perfil de ação da Maytenus aquifolium sobre radicais livres e espécies reativas do oxigênio; Profile of Maytenus aquifolium action over free radicals and reactive oxygen species

Vellosa, José Carlos Rebuglio; Barbosa, Vanessa de Frias; Khalil, Najeh Maissar; Santos, Vânia Aparecida de Freitas Formenton Macedo do; Furlan, Maysa; Brunetti, Iguatemy Lourenço; Oliveira, Olga Maria Mascarenhas de Faria
Fonte: Universidade de São Paulo. Faculdade de Ciências Farmacêuticas Publicador: Universidade de São Paulo. Faculdade de Ciências Farmacêuticas
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; Artigo Avaliado pelos Pares Formato: application/pdf
Publicado em 01/09/2007 ENG
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66.34%
Espécies Reativas do Oxigênio (ERO) e radicais livres têm tido implicações na iniciação e evolução de muitas doenças ou nas causas das mesmas em organismos vivos; há portanto, necessidade contínua por moléculas antioxidantes para inativar ERO/radicais livres. Estudos sobre extratos brutos de plantas têm demonstrado suas ações antioxidante e seqüestradora de radicais livres. Espécies do gênero Maytenus são utilizadas, em vários países, como medicamentos tradicionais no combate a úlceras gástricas, dispepsia e outras desordens gástricas, bem como por suas propriedades antiinflamatórias. Neste estudo, o extrato bruto etanólico da raiz da Maytenus aquifolium (Celastraceae) foi avaliado quanto à sua habilidade em seqüestrar radicais livres e outras espécies reativas do oxigênio. Os resultados são expressos como porcentagem de inibição das espécies ativas. O extrato foi eficiente contra as espécies estudadas: radical DPPH (inibição alcançada = 35,5 ± 1,3 %), ABTS•+ (IC50 = 0,0036 ± 0,0003 mg/mL), HOCl (IC50 = 0,002 ± 0,0001 mg/mL ), O2•- (inibição alcançada = 36,0 ± 2,1 %), and NO· (inibição alcançada = 18,3 ± 0,4 %).; Reactive oxygen species (ROS) and free radical species have been implicated in initiating...