Database : LILACS
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Id: biblio-1057403
Author: Sun, Yu; Zhu, Liping; Xu, Xiuhong; Meng, Qingxin; Men, Mengqi; Xu, Benshu; Deng, Liting.
Title: Correlación entre los microorganismos oxidantes del amonio y los factores ambientales durante el compostaje de estiércol de ganado / Correlation between ammonia-oxidizing microorganisms and environmental factors during cattle manure composting
Source: Rev. argent. microbiol;51(4):371-380, dic. 2019. graf.
Language: en.
Abstract: Abstract Cattle manure composting was performed in an aerated vessel. Community structure and diversity of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) were investigated using polymerase chain reaction and denaturing gradient gel electrophoresis (PCR-DGGE) techniques targeting the ammonia monooxygenase alpha subunit (amoA) gene and the correlation between AOB and AOA communities and environmental factors was explored. Thirteen (13) AOB sequences were obtained, which were closely related to Nitrosomonas spp., Nitrosomonas eutropha, and Nitrosospira spp. and uncultured bacteria, among which Nitrosomonas spp. were predominant. Excessively high temperature and high ammonium concentration were not favorable for AOB growth. Five AOA sequences, belonging to Candidatus Nitrososphaera gargensis and to an uncultured archaeon, were obtained. During composting, community diversity of AOB and AOA fluctuated, with AOA showing a higher Shannon-Wiener index. The AOB community changed more dramatically in the mesophilic stage and the early thermophilic stage, whereas the most obvious AOA community succession occurred in the late thermophilic stage, the cooling stage and the maturity stage. Water content, total nitrogen (TN) and ammonium concentration were more relevant to the AOB community structure, while higher correlations were observed between ammonia, nitrate and TN and the AOA community. AOB community diversity was negatively correlated with pH (r = -0.938, p < 0.01) and water content (r = -0.765, p < 0.05), while positively correlated with TN (r = 0.894, p < 0.01). AOA community diversity was negatively correlated with ammonium concentration (r = -0.901, p < 0.01). Ammonium concentration played an important role in the succession of AOB and AOA communities during composting.

Resumen Se llevó a cabo un compostaje de estiércol de ganado en un recipiente aireado. Se investigó la estructura de la comunidad y la diversidad de bacterias oxidantes del amoníaco (AOB) y las arqueas oxidantes del amoníaco (AOA) mediante el uso de las técnicas de reacción en cadena de la polimerasa y la electroforesis en gel con gradiente de desnaturalización (PCR-DGGE) dirigidas al gen de la subunidad alfa de la amonio monooxigenasa (amoA), y se exploró la correlación entre las comunidades AOB, AOA y los factores ambientales. Se obtuvieron 13 secuencias de AOB, las cuales se relacionaron estrechamente con Nitrosomonas spp., Nitrosomonas eutropha y Nitrosospira spp., y bacterias no cultivadas, entre las cuales fueron predominantes las Nitrosomonas spp. La temperatura excesivamente alta y la concentración de amonio elevada no fueron favorables para el crecimiento de las AOB. Se obtuvieron 5 secuencias de AOA, pertenecientes a Candidatus Nitrososphaera gargensis y un Archaeon no cultivado. Durante el compostaje, la diversidad de AOB y AOA fluctuó y las AOA mostraron un índice de Shannon-Wiener más alto. La comunidad de AOB cambió significativamente en la etapa mesofílica y la etapa termofílica temprana, mientras que la sucesión más obvia de la comunidad AOA ocurrió en la etapa termofílica tardía y las etapas de enfriamiento y de maduración. El contenido de agua, el nitrógeno total (TN) y la concentración de amonio fueron más relevantes para la estructura de la comunidad AOB, mientras que se observaron correlaciones mayores entre amoníaco, nitrato y TN, y la comunidad AOA. La diversidad de la comunidad AOB se correlacionó negativamente con el pH (r= -0,938; p < 0,01) y el contenido de agua (r = -0,765; p < 0,05), mientras que se relacionó positivamente con TN (r = 0,894; p < 0,01). La diversidad de la comunidad AOA se correlacionó negativamente con la concentración de amonio (r = -0,901; p < 0,01). La concentración de amonio desempenó un papel importante en la sucesión de las comunidades AOB y AOA durante el compostaje.
Responsable: AR635.1 - FCVyS - Servicio de Información y Documentación


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Id: lil-475312
Author: Guija, Henry; Troncoso C., Luzmila; Guija Poma, Emilio.
Title: Propiedades prooxidantes del camu camu (Myrciaria dubia) / Prooxidant properties of camu camu (Myrciaria dubia)
Source: An. Fac. Med. (Perú);66(4):261-268, oct. 2005. tab.
Language: es.
Abstract: Objetivo: Determinar el efecto del ion férrico sobre las propiedades prooxidantes del camu camu (Myrciaria dubia). Diseño: Estudio analítico, experimental, prospectivo y longitudinal. Materiales y Métodos: Se ha evaluado las propiedades prooxidantes del camu camu (Myrciaria dubia), fruto caracterizado por tener un elevado contenido de vitamina C, frente a Fe(III), etilendiamino tetraacético (EDTA), tiourea y manitol. Resultados: El camu camu en presencia de Fe-III en tampón fosfato a pH 7,4 incrementó notablemente la generación de radicales libres a través de una cinética de saturación, efecto que fue dependiente de la concentración del metal. La presencia de tiourea o manitol, compuestos de conocida acción antioxidante, inhibieron la formación de radicales libres, en cambio el EDTA lo incrementó. Conclusión: El camu camu incrementa la generación de radicales libres en presencia de Fe(III) y EDTA.
Responsable: PE13.1 - Oficina de Biblioteca, Hemeroteca y Centro de Documentación


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Id: lil-513913
Author: Pinto, Cristiane Franco; Leme, Adriana Franco Paes; Cavalli, Vanessa; Giannini, Marcelo.
Title: Effect of 10 percent carbamide peroxide bleaching on sound and artificial enamel carious lesions
Source: Braz. dent. j;20(1):48-53, 2009. ilus, tab.
Language: en.
Abstract: This study evaluated the effect of 10 percent carbamide peroxide (CP) bleaching on Knoop surface microhardness (KHN) and morphology of sound enamel and enamel with early artificial caries lesions (CL) after pH-cycling model (pHcm). Human dental enamel blocks were randomly divided into 6 groups (n=10): 1 - sound enamel bleached (S) with CP (Rembrandt/Den-Mat); 2 - S and submitted to pHcm; 3 - CL bleached with CP; 4 - CL stored in artificial saliva and submitted to pHcm; 5 - CL treated with placebo gel and submitted to pHcm; 6 - CL bleached with CP and submitted to pHcm. Enamel blocks with known initial KHN values were demineralized (groups 3 to 6) and submitted to 12 day pHcm (groups 2, 4, 5 and 6). After demineralization and treatments, KHN was determined and the specimens were examined using scanning electron microscopy (SEM). Data were analyzed statistically by ANOVA and Tukey's test at 5 percent significance level. The results showed that among CL groups (3 to 6) only the group 3 presented remineralization after treatments. S groups (1 and 2) showed higher KHN and presented less formation of porosities on enamel surface than CL groups after treatments. In conclusion, bleaching procedures on enamel with CL did not exacerbate the demineralization, but should be indicated with caution.

Este estudo analisou o efeito do peróxido de carbamida a 10 por cento (PC) na microdureza Knoop de superfície (KHN) e morfologia do esmalte hígido e com lesões iniciais de cárie artificial (EC), após modelo de ciclagem de pH (cpH). Blocos de esmalte dental humano foram divididos aleatoriamente em 6 grupos (n=10): 1- esmalte hígido clareado (EHC) com PC (Rembrandt/Den-Mat); 2- EHC e submetido a cpH; 3- EC clareado com PC; 4- EC armazenado em saliva artificial e submetido a cpH; 5- EC tratado com gel placebo e submetido a cpH; 6- EC clareado com PC e submetido a cpH. Blocos de esmalte com a KHN conhecida eram desmineralizados (grupos 3 a 6) e submetidos a cpH (grupos 2, 4, 5 e 6). KHN foi determinada após a desmineralização e os tratamentos. Os espécimes foram examinados através de Microscopia Eletrônica de Varredura (MEV). Os dados foram analisados através de ANOVA e teste de Tukey (p<0,05). Os resultados indicaram que entre os grupos com EC (3 a 6) somente o grupo 3 apresentou remineralização após os tratamentos. Os grupos EHC (1 e 2) mostraram maior KHN e menor formação porosidades quando comparados aos grupos EC após os tratamentos. Os procedimentos clareadores no esmalte com lesão de cárie não exacerbaram a desmineralização, entretanto precisam ser indicados com cautela.
Responsable: BR1.1 - BIREME


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Id: biblio-1049246
Author: Taha, Mervat El-Sayed; Kamal, Amaal Mohamed; Ibrahim, Dalia Ramzy.
Title: Possible protective effect of olive leaves extract on paracetamol induced hepatotoxicity in male albino rats / Possível efeito protetor do extrato de folhas de oliveira na hepatotoxicidade induzida por paracetamol em ratos albinos machos
Source: Biosci. j. (Online);36(1):245-255, jan./feb. 2020. tab, ilus.
Language: en.
Abstract: Paracetamol (PCM) overdose can cause hepatotoxicity with oxidative stress; the present study was carried out to establish the possible protective effect of olive leaves extract (OLE) on toxicity induced by paracetamol in adult male rats. Twenty four adult male rats were divided into four equal groups; control, olive leaves extract group, paracetamol group and olive leaves extract plus paracetamol group. Some biochemical parameters and liver histopathology were evaluated. PCM treatment significantly increased serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), total bilirubin, gamma-glutamyltransferase (GGT), lactate dehydrogenase (LDH), urea, creatinine and alpha-fetoprotein. Paracetamol was found to significantly increase malonaldehyde (MDA) and decrease glutathione reductase (GR) activity in tissue and significantly decrease total antioxidant capacity (TAC) and superoxide dismutase (SOD) in serum. Administration of OLE caused a significant decrease serum AST, ALT enzyme, total bilirubin, GGT, LDH, creatinine, urea, alpha-fetoprotein. Also, amelioration of oxidant ­ antioxidant status with olive leaves extract was observed in addition to a significant decrease in MDA and a significant increase in TAC in liver tissue with a significant increase in glutathione reductase (GR) and SOD in serum compared to paracetamol treated group The chemical pathological changes were in step with histopathological observation suggesting marked hepatoprotective result of olive leaves extract. It could be concluded that olive leaves extract (OLE) treatment may be effective in decreasing hepatic injury and oxidative stress induced by paracetamol overdose in male albino rats

A sobredosagem de paracetamol (PCM) pode causar hepatotoxicidade com estresse oxidativo; o presente estudo foi realizado para estabelecer o possível efeito protetor do extrato de folhas de oliveira (OLE) na toxicidade induzida pelo paracetamol em ratos machos adultos. Vinte e quatro ratos machos adultos foram divididos em quatro grupos iguais: controle, grupo extrato de folhas de oliveira, grupo paracetamol e extrato de folhas de oliveira mais grupo paracetamol. Alguns parâmetros bioquímicos e histopatologia hepática foram avaliados. O tratamento com PCM aumentou significativamente aspartato aminotransferase sérica (AST), alanina aminotransferase (ALT), bilirrubina total, gama-glutamiltransferase (GGT), lactato desidrogenase (LDH), uréia, creatinina e alfa-fetoproteína. Verificou-se que o paracetamol aumenta significativamente o malonaldeído (MDA) e diminui a atividade da glutationa redutase (GR) no tecido e diminui significativamente a capacidade antioxidante total (TAC) e a superóxido dismutase (SOD) no soro. A administração de OLE causou uma diminuição significativa de AST, enzima ALT, bilirrubina total, GGT, LDH, creatinina, uréia, alfa-fetoproteína. Também foi observada melhora do status oxidante - antioxidante com extrato de folhas de oliveira, além de uma diminuição significativa no MDA e um aumento significativo no TAC no tecido hepático, com um aumento significativo na glutationa redutase (GR) e SOD no soro em comparação ao grupo tratado com paracetamol. As alterações patológicas químicas acompanharam a observação histopatológica, sugerindo resultado hepatoprotetor acentuado do extrato de folhas de oliveira. Pode-se concluir que o tratamento com extrato de folhas de oliveira (OLE) pode ser eficaz na diminuição da lesão hepática e do estresse oxidativo induzido pela overdose de paracetamol em ratos albinos machos
Responsable: BR396.1 - Biblioteca Central


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Id: biblio-1009439
Author: Yilmaz, Gonca; Demirli Caylan, Nilgun; Demir Karacan, Can.
Title: Efecto del tabaquismo materno sobre el estado oxidativo en los niños / The effect of smoking by the mother on a child's oxidant and antioxidant status
Source: Salud(i)ciencia (Impresa) = Salud(i)ciencia (En linea);21(7):740-745, dic. 2015.
Language: es.
Abstract: El hábito de fumar es una de las más importantes causas evitables de muerte. Globalmente, más de mil millones de personas son fumadoras, dejando vulnerable al resto de la población no fumadora expuesta al humo de segunda mano (HSM). La exposición a los componentes del cigarrillo durante el embarazo y la vida posnatal temprana es, quizá, la exposición ambiental ubicua más peligrosa y evitable. Asimismo, se demostró que el humo del cigarrillo tiene consecuencias negativas sobre la salud de los niños, en especial, durante el primer año de vida. El daño oxidativo es un cambio en el equilibrio entre los procesos prooxidantes y el sistema de defensa antioxidante a favor de los prooxidantes. Esta aparece en condiciones de producción aumentada de radicales libres, en la insuficiencia de los sistemas antioxidantes o en ambos. Se ha sugerido que el aumento del daño oxidativo desempeña un papel importante en la patogenia de varias enfermedades relacionadas con el tabaquismo. El humo del cigarrillo contiene grandes cantidades de radicales libres que muchos de ellos son oxidantes y prooxidantes. El tipo de nutrición en niños expuestos al HSM es muy importante para protegerlos del daño oxidativo. El propósito de esta revisión es efectuar una revisión de los estudios que han tratado la relación entre el daño oxidativo y el tipo de nutrición en la infancia y el daño oxidativo causado por la exposición al HSM durante los períodos prenatal, posnatal y en la infancia.

Tobacco smoking is one of the most important preventable causes of death. Globally, more than 1 billion people smoke, leaving much of the world's non-smoking population vulnerable to second-hand smoke (SHS) exposure. Exposure to tobacco constituents during pregnancy and early postnatal life is perhaps the most ubiquitous avoidable hazardous environmental exposure. Additionally, tobacco smoke has been shown to have negative consequences on infant health, especially during the first year of life. Oxidative stress is a change in balance between pro-oxidant processes and antioxidant defense system in favor of pro-oxidants. It appears in conditions of increased production of free radicals, insufficiency of antioxidant systems or both. It has been suggested that increased oxidative stress plays a major role in the pathogenesis of several smoking-related diseases. Tobacco smoke contains large quantities of free radicals, many of which are oxidants and pro-oxidants. The type of nutrition in infants who are exposed to SHS is very important to protect them from oxidative stress. The purpose of this paper is to review the studies dealing with the relation between oxidative stress and the type of nutrition in infancy and oxidative stress caused by SHS exposure during prenatal, neonatal, postnatal and childhood periods.
Responsable: AR392.1 - Biblioteca


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Id: biblio-975689
Author: Mis, Leyla; Comba, Bahat; Uslu, Sema; Yeltekin, Asli.
Title: Effect of wheatgrass on DNA damage, oxidative stress index and histological findings in diabetic rats / Efecto del pasto de trigo sobre el daño del ADN, el índice de estrés oxidativo y los hallazgos histológicos en ratas diabéticas
Source: Int. j. morphol;36(4):1235-1240, Dec. 2018. tab, graf.
Language: en.
Abstract: This study was aimed to search the effect of wheatgrass on the Total Antioxidan (TAS)-Oxidan Status (TOS) and DNA damage in rat with diabetes. The rats used in the study were randomly divided into 4 groups that each of has 10 rats: Control group; 1 ml single dose phosphate-citrate buffer injected i.p (pH: 4.5), Diabetes group; 45 mg/kg single dose streptozotocin injected i.p., Wheatgrass group; was given oral wheatgrass (10 ml/kg/day) for 6 weeks, Diabetes +Wheatgrass group; 45 mg/kg single dose streptozotocin injected i.p. and wheatgrass (10 ml/kg/day) was given by oral during 6 weeks. After the process of experiment during 6 weeks, blood sample and pancreas tissue were taken. The analysis were done of blood glucose levels, TAS, TOS levels by colorimetric kits; DNA damage by ELISA kits in serum. The pancreas tissues were examined histopathologically. In the group of Diabetes+Wheatgrass was determined that the levels of glucose levels (p<0.001), TOS (p<0.05) and OSI (p<0.01) statistically decreased and heal histopatolojical compared to diabetes group. In the group of Wheatgrass was determined that the levels of TAS p<0.05 statistically increased from other groups. The statistical significance were not found in the level of serum 8OHdG differences between the groups. The beta cells were seen to increase in the group receiving wheatgrass for therapeutic purposes.As a conclusion, it was determined that wheatgrass strengthened the anti-oxidant defense system and reduced the glucose level in diabetic rats.

El objetivo de este estudio fue buscar el efecto del pasto de trigo sobre el estado total de antioxidantes (TAS) -Oxidan Status (TOS) y el daño del ADN en ratas con diabetes. Las ratas analizadas en el estudio se dividieron aleatoriamente en 4 grupos de 10 ejemplares cada uno: grupo control; 1 ml de tampón fosfato-citrato de dosis única inyectado i.p. (pH: 4,5)., Grupo diabetes; 45 mg / kg de estreptozotocina en dosis única inyectada i.p., grupo pasto de trigo; se administró pasto de trigo oral (10 ml / kg / día) durante 6 semanas, grupo diabetes + pasto de trigo; 45 mg / kg de estreptozotocina en dosis única inyectada i.p. y pasto de trigo (10 ml / kg / día) por vía oral durante 6 semanas. Después del proceso experimental durante 6 semanas, se tomaron muestras de sangre y tejido de páncreas. Se midieron los niveles de glucosa en sangre, TAS, y TOS mediante kits colorimétricos; El daño al ADN fue realizado por kits de ELISA en suero. Los tejidos del páncreas se examinaron histopatológicamente. En el grupo de diabetes + pasto de trigo se determinó que los niveles de glucosa (p <0,001), TOS (p <0,05) y OSI (p <0,01) disminuyeron estadísticamente y curaron histopatológicamente en comparación con el grupo de diabetes. En el grupo de pasto de trigo se determinó que los niveles de TAS p <0,05 se incrementaron estadísticamente con respecto a otros grupos. No fue estadísticamente significativo el nivel de las diferencias séricas de 8OHdG entre los grupos. Se observó que las células beta aumentaron en el grupo que recibió pasto de trigo con fines terapéuticos. Como conclusión, se determinó que el pasto de trigo fortaleció el sistema de defensa antioxidante y redujo el nivel de glucosa en las ratas diabéticas.
Responsable: CL1.1 - Biblioteca Central


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Id: biblio-866648
Author: Iano, Flávia Godoy.
Title: Efeito da ingestão crônica do fluoreto sobre o sistema oxidante/antioxidante de ratos / Effect of chronic fluoride intake in the oxidant/antioxidant system of rats.
Source: Bauru; s.n; 2012. 166 p. ilus, tab, graf.
Language: pt.
Thesis: Submitted to Universidade de São Paulo. Faculdade de Odontologia de Bauru presented for the degree Doutor.
Abstract: A ingestão excessiva de fluoreto por um longo período de tempo pode resultar em fluorose, que pode causar manifestações dentárias e esqueléticas. Danos metabólicos, funcionais e estruturais causados pela fluorose crônica tem sido relatados em vários tecidos. O objetivo deste estudo foi avaliar os efeitos do fluoreto administrado na água de beber, da administração de fluoreto na água de beber na defesa antioxidante de ratos. Quatro grupos de ratos wistar foram usados (n=10/grupo). Os animais receberam água de beber contendo 0 (controle), 5, 15 ou 50 ppm de fluoreto durante 60 dias. Eles foram eutanasiados e os tecidos (fígado, rins e coração) e plasma foram coletados e homogenizados. Superóxido dismutase (SOD), catalase (CAT), glutationa peroxidase (GPx), glutationa reduzida (GSH), substâncias antioxidantes totais (SAT), substâncias reativas ao ácido tiobarbitúrico (TBARS), hidroperóxido de lipídios (HL) e fluoreto foram análisadas. Dados foram analisados por ANOVA e teste de Tukey ou Kruskal-Wallis e teste de Dunn (p<0,05). Nos rins, SOD, GPx, GSH e SAT diminuiram e fluoreto e HL aumentaram significantivamente. No fígado, CAT e TBARS diminuiram, SOD, HL e SAT aumentaram significativamente. No coração, GPx aumentou significativamente. No plasma, SOD e HL diminuiram significativamente. Em resumo, esses resultados mostram que a administração crônica de fluoreto altera o sistema antioxidante de ratos. Nosso dados sugerem que a exposição em níveis elevados de fluoreto, a conversão do ânion superóxido em água nos rins parecem ocorrer principalmente através da SOD e CAT, com baixa participação do sistema glutationa, diferindo do que parece ocorrer no fígado.

Excessive fluoride intake over a long period of time could result in fluorosis, which can lead to dental and skeletal manifestations. Metabolic, functional and structural damages caused by chronic fluorosis have been reported in many tissues. The aim of this study was to evaluate the effect of fluoride, administered in drinking water, in the antioxidant defense of rats. Four groups of Wistar rats were included (n=10/group). The animals received drinking water containing 0 (control), 5, 15 or 50 ppm of fluoride during 60 days. They were euthanized and the tissues (liver, kidney and heart) and plasma were collected and homogenized. Superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), reduced glutathione (GSH), antioxidants, thiobarbituric acid reactive substances (TBARS), lipid hydroperoxide (LH), and fluoride were analyzed. Data were analyzed by ANOVA and Tukeys test or Kruskal-Wallis and Dunns tests (p<0.05). In the kidney SOD, GPx, GSH and SAT decreased and fluoride and LH increased significantly. In the liver, CAT and TBARS decreased and fluoride, SOD, LH and SAT increased significantly. In the heart, GPx increased significantly. In the plasma, SOD and LH decreased significantly. In summary, these results show that chronic fluoride administration alters the antioxidant system of the rats. Our data suggest that upon exposure to high levels of fluoride, the conversion of the superoxide anion to water in the kidney seems to occur mainly through the SOD and CAT, with a low participation of the glutathione system, differing from what seems to occur in the liver.
Responsable: BR28.1 - Serviço de Biblioteca e Documentação Professor Doutor Antônio Gabriel Atta


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Id: biblio-849475
Author: Martins, Rodrigo dos Santos.
Title: Busca por oxidantes quirais para a transformação enantiosseletiva de compostos orgânicos de boro / Search for chiral oxidants for the enantioselective transformation of organic boron compounds.
Source: São Paulo; s.n; 2017. 201p p. ilus, tab, graf.
Language: pt.
Thesis: Submitted to Universidade de São Paulo. Instituto de Química presented for the degree Doutor.
Abstract: Neste trabalho, avaliou-se o potencial do uso de oxidantes quirais em oxidações enantiosseletivas de compostos orgânicos de boro. É de conhecimento geral que compostos orgânicos de boro, especialmente ésteres e ácidos borônicos são facilmente oxidados por hidroperóxidos em meio básico. No entanto, são escassos na literatura exemplos destas reações de modo enantiosseletivo. A fim de realizar as reações mencionadas, sintetizou-se os hidroperóxidos quirais TADOOH ({(4R,5R)-5-[(hidroperoxidifenil)metil]-2,2-dimetil-1,3-dioxolan-4il}difenilmetanol) e o hidroperóxido quiral derivado de carboidrato, 2,3-dideoxi1-O-oxidanil-4,6-di-O-pivaloil-α-D-eritro-hex-2-enopiranose (di-O-PivOOH). Estes compostos apresentaram resultados interessantes na literatura em oxidações enantiosseletiva de sulfetos orgânicos, em epoxidações de alcenos e em oxidações de Baeyer-Villiger. Inicialmente o potencial oxidativo de ambos hidroperóxidos, bem como a seletividade destes, foi avaliado frente a diversos ésteres borônicos, sendo que somente o TADOOH apresentou resultados promissores. (Ver esquema no PDF) Observou-se uma melhor seletividade do TADOOH frente a ésteres borônicos que possuíam grupos carbonílicos em sua estrutura. Ao submeter o ß-boronil-éster, 3-fenil-3-(4,4,5,5-tetrametil-1,3,2-dioxaborolan-2-il)propanoato de etila, à oxidação com o TADOOH em THF utilizando NaOH como base, a -30°C por 1 hora, obteve-se o respectivo álcool com 40% de e.e. Cálculos de DFT para o estado de transição na oxidação dos ésteres borônicos com o TADOOH foram realizados em colaboração com o grupo do Prof. Dr. Ataualpa Albert Carmo Braga. Estes cálculos demonstraram que o estado de transição é estabilizado por uma ligação de hidrogênio não clássica entre o oxigênio da carbonila e umas das ligações C-H dos grupos fenila do TADOOH. Além dos estudos relatados, a reconhecida metodologia de Sharpless na epoxidação assimétrica de alcoóis alílicos foi adaptada para a oxidação enantiosseletiva de ésteres borônicos. Ao trocar o ligante derivado de éster tártarico, normalmente utilizado nas epoxidações de Sharpless, por (-)-efedrina observou-se uma moderada seletividade deste sistema frente ao pinacol l-fenietilboronato. Investigações mais detalhadas demonstraram que a presença do Ti(IV) não era necessária, sendo que a (-)efedrina era a responsável pela ativação e indução quiral nesta reação.

In this work, it was investigated the potential use of chiral oxidants in organic boron compound oxidation. It is known in the literature, that organic boron compounds can be easily oxidized by hydroperoxides. However, an enantioselective approach in literature is scarce. In order to perform these reactions, hydroperoxide TADOOH ({(4R,5R)-5[(hydroperoxydiphenyl)methyl]-2,2-dimethyl-l,3-dioxolan-4-yl}diphenylmethanol) and carbohydrate derived hydroperoxide, 2,3-dideoxy-1-O-oxidanyl-4,6-di-O-pivaloyl-α-D-erythro-hex-2-enopyranose (di-O-PivOOH), have been synthesized. These compounds showed interesting results in several enantioselective oxidations, as like, organic sulfides oxidation, alkenes epoxidation and Baeyer-Villiger oxidations. The oxidative potential of both hydroperoxides, as well as their selectivity, were evaluated against several boronic esters. Only TADOOH has shown promissing results for further studies. (See Scheme on PDF). Boronic esters containing a carbonyl moiety showed better selectivities with TADOOH, for example, the reaction of ß-boronyl-ester, ethyl 3-phenyl-3-(4,4,5,5-tetramethyl-l,3,2-dioxaborolan-2-yl)propanoate, gave the correponding alcohol with 40% e.e. DFT calculations for the transition state in the oxidation of the boronic esters with TADOOH were carried out in collaboration with the group of Prof. Dr. Ataualpa Albert Carmo Braga. These calculations have shown that the transition state is stabilized by a non-classical hydrogen bond between the carbonyl oxygen and one of the C-H bonds of the TADOOH phenyl groups. In addition to the studies, the well-known Sharpless protocol for asymmetric epoxidation of allylic alcohols was adapted in the enantioselective oxidation of boronic esters. By replacing the tartaric ester-derived, commonly used in the Sharpless experiments, for (-)-ephedrine moderate selectivity was observed with pinacol 1-phenylethyl boronate. Further investigations showed that the presence of Ti (IV) was not necessary, and (-)-ephedrine was responsible for the activation and chiral induction in this reaction.
Responsable: BR40.1 - DBD - Divisão de Biblioteca e Documentacão do Conjunto das Químicas


  9 / 107 LILACS  
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Mondelli, Rafael Francisco Lia
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Id: lil-779900
Author: MONDELLI, Rafael Francisco Lia; SOARES, Ana Flávia; PANGRAZIO, Eugenio Gabriel Kegler; WANG, Linda; ISHIKIRIAMA, Sergio Kiyoshi; BOMBONATTI, Juliana Fraga Soares.
Title: Evaluation of temperature increase during in-office bleaching
Source: J. appl. oral sci;24(2):136-141, Mar.-Apr. 2016. tab, graf.
Language: en.
Abstract: ABSTRACT The use of light sources in the bleaching process reduces the time required and promotes satisfactory results. However, these light sources can cause an increase in the pulp temperature. Objective The purpose of the present study was to measure the increase in intrapulpal temperature induced by different light-activated bleaching procedures with and without the use of a bleaching gel. Material and Methods A human maxillary central incisor was sectioned 2 mm below the cementoenamel junction. A K-type thermocouple probe was introduced into the pulp chamber. A 35% hydrogen peroxide bleaching gel was applied to the vestibular tooth surface. The light units used were a conventional halogen, a hybrid light (only LED and LED/Laser), a high intensity LED, and a green LED light. Temperature increase values were compared by two-way ANOVA and Tukey´s tests (p<0.05). Results There were statistically significant differences in temperature increases between the different light sources used and between the same light sources with and without the use of a bleaching gel. The presence of a bleaching gel generated an increase in intra-pulpal temperature in groups activated with halogen light, hybrid light, and high intensity LED. Compared to the other light sources, the conventional halogen lamp applied over the bleaching gel induced a significant increase in temperature (3.83±0.41°C). The green LED unit with and without gel application did not produce any significant intrapulpal temperature variations. Conclusion In the present study, the conventional halogen lamp caused the highest increase in intrapulpal temperature, and the green LED caused the least. There was an increase in temperature with all lights tested and the maximum temperature remained below the critical level (5.5°C). The addition of a bleaching gel led to a higher increase in intrapulpal temperatures.
Responsable: BR1.1 - BIREME


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Author: Pizani, Andréia Mara Andrade; Tholt, Beatriz; Paciornik, Sidnei; Dias, Katia Regina Hostilio Cervantes; Albuquerque, Pedro Paulo Albuquerque Cavacanti de; Queiroz, Celso Silva.
Title: Dental bleaching agents with calcium and their effects on enamel microhardness and morphology
Source: Braz. j. oral sci;14(2):154-158, Apr.-June 2015. tab, ilus.
Language: en.
Abstract: Aim: To evaluate enamel microhardness and morphology after bleaching with hydrogen peroxide containing calcium in different concentrations. Methods: One hundred specimens of human teeth were ground and polished and had the initial microhardness evaluated. The specimens were randomly assigned into five groups (n=20): Group 1 - Control group (no treatment); Group 2 - Home Peroxide 6% (without calcium); Group 3 - Home Peroxide 7.5% (without calcium); Group 4 - White Class 6% (with calcium); Group 5 - White Class 7.5% (with calcium). For each group, the bleaching was performed according to the manufacturer's specifications. The specimens were bleached once a day for 5 days and subjected to pH cycling. Microhardness and scanning electron microscopy (SEM) analysis were performed before and after bleaching. Results: The results showed that groups submitted to bleaching treatment presented hardness loss compared to the control group. The group of 7.5% hydrogen peroxide with calcium showed a lower percentage of hardness loss in relation to other groups. Conclusion: Calcium in association with a higher hydrogen peroxide concentration may decrease microhardness changes on enamel.
Responsable: BR218.1 - Biblioteca Carlos Henrique Robertson Liberalli



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