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2,3-Diarylxanthones as strong scavengers of reactive oxygen and nitrogen species: A structure–activity relationship study IPB - Escola Superior Agrária
Santos, Clementina M.M.; Freitas, Marisa; Ribeiro, Daniela; Gomes, Ana; Silva, Artur; Cavaleiro, José; Fernandes, Eduarda.
Xanthones are a class of oxygen-containing heterocyclic compounds widely distributed in nature. The natural derivatives can present different substitutions in the xanthone core that include hydroxyl, methoxyl, prenyl and glycosyl groups. The inclusion of aryl groups has only been reported for a few synthetic derivatives, the 2,3-diaryl moiety being recently introduced by our group. Xanthones are endowed with a broad spectrum of biological activities, many of them related to their antioxidant ability, including the scavenging of reactive oxygen species (ROS) and reactive nitrogen species (RNS), as well as metal chelating effects. Considering the interesting and promising antioxidant activities present in compounds derived from the xanthone core, the main...
Tipo: Article Palavras-chave: 2; 3-Diarylxanthones Reactive oxygen species Reactive nitrogen species Scavenging activity Antioxidant activity.
Ano: 2010 URL: http://hdl.handle.net/10198/3241
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2-Styrylchromones as novel inhibitors of xanthine oxidase. A structure-activity study IPB - Escola Superior Agrária
Fernandes, Eduarda; Carvalho, Félix; Silva, Artur; Santos, Clementina M.M.; Pinto, Diana; Cavaleiro, José; Bastos, Maria de Lourdes.
The purpose of this study was the evaluation of the xanthine oxidase (XO) inhibition produced by some synthetic 2-styrylchromones. Ten polyhydroxylated derivatives with several substitution patterns were synthesised, and these and a positive control, allopurinol, were tested for their effects on XO activity by measuring the formation of uric acid from xanthine. The synthesised 2-styrylchromones inhibited xanthine oxidase in a concentration-dependent and non-competitive manner. Some IC50 values found were as low as 0.55mM, which, by comparison with the IC50 found for allopurinol (5.43 mM), indicates promising new inhibitors. Those 2-styrylchromones found to be potent XO inhibitors should be further evaluated as potential agents for the treatment of...
Tipo: Article Palavras-chave: 2-styrylchromones; Allopurinol; Benzopyrone; Xanthine oxidase inhibition.
Ano: 2002 URL: http://hdl.handle.net/10198/3931
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2-Styrylchromones: novel strong scavengers of reactive oxygen and nitrogen species IPB - Escola Superior Agrária
Gomes, Ana; Fernandes, Eduarda; Silva, Artur; Pinto, Diana; Santos, Clementina M.M.; Cavaleiro, José; Lima, José Costa.
2-Styrylchromones are a small group of naturally occurring chromones, vinylogues of flavones (2-phenylchromones). Natural and synthetic 2-styrylchromones have been tested in different biological systems, showing activities with potential therapeutic applications. In particular, the potential and hitherto understudied antioxidant behavior of these compounds has been raised as a matter of interest. Thus the present work consisted in the study of the in vitro scavenging activities for reactive oxygen species (ROS) and reactive nitrogen species (RNS) of various 2-styrylchromone derivatives and structurally similar flavonoids. Some of the studied 2-styrylchromones proved to be extremely efficient scavengers of the different ROS and RNS, showing, in some cases,...
Tipo: Article Palavras-chave: 2-Styrylchromones; Reactive oxygen species; Reactive nitrogen species; Scavenging activity; Antioxidant activity.
Ano: 2007 URL: http://hdl.handle.net/10198/3922
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2-Styrylchromones with potencial antioxidant activity IPB - Escola Superior Agrária
Santos, Clementina M.M.; Silva, Artur; Cavaleiro, José.
Tipo: ConferenceObject
Ano: 2000 URL: http://hdl.handle.net/10198/3487
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A novel and efficient route for the syntheses of hydroxylated 2,3-diarylxanthones IPB - Escola Superior Agrária
Santos, Clementina M.M.; Silva, Artur; Cavaleiro, José.
A novel, efficient and general route for the synthesis of hy-droxylated 2,3-diarylxanthones is described. 3-Bromo-2-styrylchromones, the key intermediate of this synthesis, is obtained by a Baker-Venkataraman rearrangement of appropriate 2’-cinnamoyloxyacetophenones, followed by a one-pot reaction with phenyltrimethylammonium tribromide. The Heck reaction of these bromochromones with substituted styrenes gives methoxylated 2,3-diarylxanthones. The cleavage of the methyl groups with BBr3 gives the desired hydroxylated 2,3-diarylxanthones.
Tipo: Article Palavras-chave: Hydroxylated diarylxanthones; 3-bromo-2-styrylchromones; Heck reaction; Phenyltrimethylammonium tribromide; Demethylation.
Ano: 2007 URL: http://hdl.handle.net/10198/3240
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A novel route for the synthesis of 2,3-Diarylxanthones IPB - Escola Superior Agrária
Santos, Clementina M.M.; Silva, Artur; Cavaleiro, José.
Chemically, xanthones are oxygenated heterocyclic compounds with a dibenzo-け-pirone nucleus [1]. Natural derivatives have several types of substituents in different positions of their nucleus, which can be associated to the pharmacological properties presented by this class of compounds [2]. Xanthones bearing aryl substituents are scarce and no natural derivatives have been reported with the 2,3-diaryl substitution pattern. Recently, we have reported the synthesis of several 2,3-diarylxanthones, starting from 3-bromo-2-methylchromone.
Tipo: ConferenceObject
Ano: 2006 URL: http://hdl.handle.net/10198/3427
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Anti-inflammatory potencial of 2-Styrylchromones regarding their interference with arachidonic acid metabolic pathways IPB - Escola Superior Agrária
Gomes, Ana; Fernandes, Eduarda; Silva, Artur; Santos, Clementina M.M.; Pinto, Diana; Cavaleiro, José; Lima, José Costa.
Tipo: ConferenceObject
Ano: 2008 URL: http://hdl.handle.net/10198/3375
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Anti-inflammatory potential of 2-styrylchromones regarding their interference with arachidonic acid metabolic pathways IPB - Escola Superior Agrária
Gomes, Ana; Fernandes, Eduarda; Silva, Artur; Pinto, Diana; Santos, Clementina M.M.; Cavaleiro, José; Lima, José Costa.
Cyclooxygenases (COXs) are the key enzymes in the biosynthesis of prostanoids. COX-1 is a constitutive enzyme while the expression of COX-2 is highly stimulated in the event of inflammatory processes, leading to the production of large amounts of prostaglandins (PGs), in particular PGE2 and PGI2, which are pro-inflammatory mediators. Lipoxygenases (LOXs) are enzymes that produce hydroxy acids and leukotrienes (LTs). 5-LOX metabolizes arachidonic acid to yield, among other products, LTB4, a potent chemoattractantmediator of inflammation. The aim of the present work was to evaluate the anti-inflammatory potential of 2-styrylchromones (2-SC), a chemical family of oxygen heterocyclic compounds, vinylogues of flavones (2-phenylchromones), by studying their...
Tipo: Article Palavras-chave: 2-Styrylchromones; Cyclooxygenase; 5-Lipoxigenase; Leukotriene B4; Dual inhibitors; Inflammation.
Ano: 2009 URL: http://hdl.handle.net/10198/3919
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Cyclic voltammetric analysis of 2-styrylchromones IPB - Escola Superior Agrária
Gomes, Ana; Fernandes, Eduarda; Garcia, M. Beatriz; Silva, Artur; Pinto, Diana; Santos, Clementina M.M.; Cavaleiro, José; Lima, José Costa.
Tipo: ConferenceObject
Ano: 2008 URL: http://hdl.handle.net/10198/3355
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Cyclic voltammetric analysis of 2-styrylchromones: Relationship with the antioxidant activity IPB - Escola Superior Agrária
Gomes, Ana; Fernandes, Eduarda; Garcia, M. Beatriz; Silva, Artur; Pinto, Diana; Santos, Clementina M.M.; Cavaleiro, José; Lima, José Costa.
2-Styrylchromones (2-SC) are a chemical family of oxygen heterocyclic compounds, vinylogues of flavones (2-phenylchromones), whose occurrence in nature has been reported. Recently, several 2-SC derivatives were demonstrated to have antioxidant properties, namely, xanthine oxidase inhibition, hepatoprotection against pro-oxidant agents in cellular and non-cellular systems and scavenging activity against reactive oxygen and reactive nitrogen species (ROS and RNS). Considering these antioxidant properties, it may be hypothesised that the electrochemical redox behaviour of 2-SC contributes significantly to their activity. To test this hypothesis, the electrochemical behaviour of different 2-SC was studied, together with a number of flavonoids with well-known...
Tipo: Article Palavras-chave: 2-Styrylchromones; Cyclic voltammetry; Oxidation mechanism; Scavenging activity; Reactive oxygen species; Reactive nitrogen species.
Ano: 2008 URL: http://hdl.handle.net/10198/4011
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Dimethyldioxirane oxidation of exocyclic (E,E)-cinnamylideneketones IPB - Escola Superior Agrária
Lévai, Albert; Silva, Artur; Santos, Clementina M.M.; Cavaleiro, José; Jeko, József.
Exocyclic (E,E)-cinnamylideneketones were oxidized by an excess of isolated dimethyldioxirane (DMDO, in acetone solution) at room temperature, providing diastereomeric mixtures of the α,β:γ,δ-diepoxides. In the case of derivatives bearing an ortho-nitrocinnamylidene moiety, α,β-monoepoxides were also isolated as minor products. The structures of all new compounds and the stereochemistry of the monoepoxides and diepoxide diastereomers were established by NMR studies.
Tipo: Article Palavras-chave: Cinnamylideneketones; Dimethyldioxirane; Epoxides; NMR spectroscopy.
Ano: 2009 URL: http://hdl.handle.net/10198/3921
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Efficient syntheses of new polyhydroxylated 2,3-diaryl-9h-xanthen-9-ones IPB - Escola Superior Agrária
Santos, Clementina M.M.; Silva, Artur; Cavaleiro, José.
A large number of hydroxylated 2,3-diaryl-9H-xanthen-9- ones have been synthesised by two different approaches, starting either from 3-bromo-2-methyl-4H-chromen-4-one or from (E)-3-bromo-2-styryl-4H-chromen-4-ones. The former method involves Heck reactions between 3-bromo-2-methyl- 4H-chromen-4-one and styrenes, leading to (E)-2-methyl-3- styryl-4H-chromen-4-ones; these condensed with benzaldehyde to give (E,E)-2,3-distyryl-4H-chromen-4-ones, which led to the desired 2,3-diaryl-9H-xanthen-9-ones under reflux in 1,2,4-trichlorobenzene. 3-Bromo-2-styryl-4H-chromen-4- ones were obtained either by aldol condensations between 3-bromo-2-methyl-4H-chromen-4-one and benzaldehydes, or through Baker–Venkataraman rearrangements of 2-acetylphenyl cinnamates, followed...
Tipo: Article Palavras-chave: Xanthones; Alcohols; Oxygen heterocycles; Heck reaction; NMR spectroscopy.
Ano: 2009 URL: http://hdl.handle.net/10198/3221
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Epoxidação de (E,E)-Cinamilidenoacetofenonas com Peróxido de Hidrogénio IPB - Escola Superior Agrária
Santos, Clementina M.M.; Silva, Artur; Cavaleiro, José.
As (E,E)-cinamilidenoacetofenonas pertencem a um importante grupo de cetonas a,β,Y,∂-insaturadas, cuja síntese envolve a condensação aldólica de acetofenonas com cinamaldeídos adequadamente substituídos. Certos derivados saturados, as 1,5-diaril-1-pentanonas, foram isolados a partir de plantas usadas na medicina tradicional da Africa tropical, da Ásia e da Austrália e demonstraram possuir forte actividade anti-bacteriana.2 No entanto, os compostos desta família com mais aplicações são as (E,E)-2'-hidroxicinamilidenoacetofenonas, as quais constituem uma importante classe de intermediários na síntese de 2- estirilcromonas.3 A epoxidação deste tipo de compostos com dimetildioxirano ou com o método de epoxidação assimétrica de Juliá já foi descrita, embora...
Tipo: ConferenceObject
Ano: 2004 URL: http://hdl.handle.net/10198/3430
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Epoxidation of 2-Styrylchromone derivatives IPB - Escola Superior Agrária
Santos, Clementina M.M.; Silva, Artur; Cavaleiro, José; Patonay, Támas; Lévai, Albert.
Tipo: ConferenceObject
Ano: 2004 URL: http://hdl.handle.net/10198/3493
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Epoxidation of (E,E)-Cinnamylideneacetophenones Using Salen Mn(III) as Catalyst IPB - Escola Superior Agrária
Santos, Clementina M.M.; Silva, Artur; Cavaleiro, José; Patonay, Támas; Lévai, Albert.
Salen Mn(III) complexes are efficient and practical catalysts for the epoxidation of various α,β-unsaturated carbonyl compounds. Among common oxidants used are iodosylbenzene, sodium hipochlorite, oxone, peracids and dimethyldioxirane [1]. Although the epoxidation of cinnamylideneacetophenones have already been reported in literature (by Julia’s epoxidation using hydrogen peroxide as oxidant [2] and by oxidation with dimethyldioxirane [3]), no studies were performed using these kind of salen Mn(III) complexes as catalysts. On these basis, we developed a study on the epoxidation of cinnamylideneacetophenones 1, catalyzed by commercially available Jacobsen’s catalyst [salen Mn(III)] and using iodosylbenzene and hydrogen peroxide as oxidants. Several...
Tipo: ConferenceObject Palavras-chave: Cinnamylideneacetophenones; Salen catalyst; Epoxidation; Iodosylbenzene; Hydrogen peroxide; NMR spectroscopy.
Ano: 2006 URL: http://hdl.handle.net/10198/3978
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Epoxidation of (E,E)-cinnamylideneacetophenones with hydrogen peroxide and iodosylbenzene with salen-mnIII as the catalyst IPB - Escola Superior Agrária
Santos, Clementina M.M.; Silva, Artur; Cavaleiro, José; Lévai, Albert; Patonay, Támas.
(E,E)-Cinnamylideneacetophenones 3a–j were epoxidized under mild conditions with Jacobsen’s catalyst 4 and hydrogen peroxide or iodosylbenzene as oxidants. γ,δ-Monoepoxides and a diastereomeric mixture of α,β:γ,δ-diepoxides were obtained in each case, and only the α,β-monoepoxide of 4- nitrocinnamylideneacetophenone (3d) was isolated. The presence of a methyl group in the vinylic moiety of substrates 3i,j allowed the formation of two γ,δ-monoepoxide diastereomers. The epoxidation of (E,E)-2 -hydroxycinnamylid- Introduction Salen MnIII complexes are efficient catalysts for the epoxidation of various olefinic compounds.[1–3] Since the pioneering work of Kochi et al.,[4] many contributors have reviewed a wide range of applications of these powerful and...
Tipo: Article Palavras-chave: Cinnamylideneacetophenones; Epoxidation; Jacobsen’s catalyst; Hydrogen peroxide; Iodosylbenzene.
Ano: 2007 URL: http://hdl.handle.net/10198/3920
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Epoxidation Studies do 2-Styrylchromones IPB - Escola Superior Agrária
Santos, Clementina M.M.; Silva, Artur; Cavaleiro, José.
Chromones represent an important class of compounds due to their broad range of applications. Certain natural and synthetic hydroxyl derivatives have shown important pharmacological, biocidal and mainly antioxidant activities.1 We are interested in the design of new 2-styrylchromones analogues containing hydroxyl groups at the C-3 and Cα=Cβ systems because they could increase the antioxidation activity of these compounds.2 Our first approach is the preparation of epoxide systems and then we intend to open the epoxide ring to give the desired hydroxyl derivatives. We studied the epoxidation of 2-styrylchromones 1 with hydrogen peroxide and iodosylbenzene using N,N'-bis(3,5-di-tert-butylsalicylidine)- 1,2-cyclohexanediaminomanganese (III) chloride [salen...
Tipo: ConferenceObject
Ano: 2003 URL: http://hdl.handle.net/10198/3433
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Epoxidation studies of 2-styrylchromones using Jacobsen’s catalyst and hydrogen peroxide and iodosylbenzene as oxidants IPB - Escola Superior Agrária
Santos, Clementina M.M.; Silva, Artur; Cavaleiro, José; Patonay, Támas; Lévai, Albert.
The epoxidation of 2-styrylchromones 2a-h using Jacobsen’s Mn(III)[salen] complex 1 as catalyst is reported for the first time. Several studies were performed using both hydrogen peroxide and iodosylbenzene as oxidants, in order to obtain the α,β-epoxy-2-styrylchromones 3a-h regioselectively. Due to the low reactivity of the substrates and the highly unstable character of the formed epoxides, reactions should be interrupted at lower conversions to obtain acceptable yields, especially when hydrogen peroxide is used.
Tipo: Article Palavras-chave: 2-Styrylchromones; Jacobsen catalyst; Epoxidation; Iodosylbenzene; Hydrogen peroxide.
Ano: 2006 URL: http://hdl.handle.net/10198/3923
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Hepatoprotective activity of 2-styrylchromone derivatives against the pro-oxidant hepatotoxic effect elicited by tert-butylhydroperoxide in freshy isolated rat hepatocytes IPB - Escola Superior Agrária
Fernandes, Eduarda; Carvalho, M.; Carvalho, Félix; Silva, Artur; Santos, Clementina M.M.; Pinto, Diana; Cavaleiro, José; Bastos, Maria de Lourdes.
Tipo: ConferenceObject
Ano: 2003 URL: http://hdl.handle.net/10198/3496
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Hepatoprotective activity of polyhydroxylated 2-styrylchromones against tert-butylhydroperoxide induced toxicity in freshly isolated rat hepatocytes IPB - Escola Superior Agrária
Fernandes, Eduarda; Carvalho, M.; Carvalho, Félix; Silva, Artur; Santos, Clementina M.M.; Pinto, Diana; Cavaleiro, José; Bastos, Maria de Lourdes.
2-Styrylchromones are a novel class of chromones, vinylogues of flavones (2-phenylchromones), which have recently been found in nature. The best described property of almost every group of flavones and other flavonoids, especially the hydroxylated derivatives, is their capacity to act as antioxidants. Indeed there is a widely accepted view that the positive health effects of flavones are due to their antioxidant activity. As oxidative stress is a main cause of liver toxicity induced by several hepatotoxicants, agents with the ability to protect the liver against reactive pro-oxidant species may be therapeutically useful. The present study evaluated the possible protective activity of six new synthetic polyhydroxylated 2-styrylchromone derivatives against...
Tipo: Article Palavras-chave: 2-Styrylchromones; Tert-Butylhydroperoxide; Hepatoprotective activity; Freshly isolated rat hepatocytes.
Ano: 2003 URL: http://hdl.handle.net/10198/3977
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