The following work examines the hydrogenation of p-nitrotoluene in the liquid phase and the partial hydrogenation of acroleine in the gas phase. For both reactions a microchannel reactor (MCR) with catalytically active walls and fixed bed catalysts have been prepared and applicated. In case of the hydrogenation of p-nitrotoluene using the MCR the aim was to prepare a catalytically active wall coating. To achieve this the inner surface of the MCR was anodically oxidized and followed by a deposition of palladium in the resulting oxide layer by means of electrochemical and wetchemical reduction. The resulting coating was modified by promoting it with lanthane. The maximum space time yield of p-toluidine was 7 mols per liter and hour. This is significantly more than the state-of-the-art today which is limited by heat transfer and enables a space time yield in the range of 0.15 to 1.5 mol per liter and hour. Thus, the MCR could be profitably used for this reaction. In case of the partial hydrogenation of acroleine with allyl alcohol as the desired product silver based real and model catalysts have been used. The aim was to identify correlations between the chosen catalyst support and immobilization procedure on one side and the catalytical properties of the resulting catalyst on the other. Aluminum and silicon dioxide have been used as catalyst support. The catalytically active component silver was deposited using conventional wet impregnation procedures as well as electrochemical silver deposition and sputtering of silver. It was possible to discriminate between effects due to the choice of the support material and effects due to the choice of the immobilization procedure. For this reaction, the MCR could not be used profitably. / In der vorliegenden Arbeit wurde die Hydrierung von p-Nitrotoluol in der Flüssigphase und die partielle Hydrierung von Acrolein in der Gasphase untersucht. Für beide Reaktionen wurden Mikrostrukturreaktoren (MSR) mit katalytisch aktiven Wänden sowie Schüttgutkatalysatoren präpariert und eingesetzt. Im Fall der Hydrierung von p-Nitrotoluol im MSR bestand das Ziel in der Präparation einer geeigneten katalytisch aktiven Wandbeschichtung. Dazu wurde die innere Oberfläche des MSR anodisch oxidiert und in der resultierenden Oxidschicht Palladium durch elektrochemische und nasschemische Reduktion abgeschieden. Modifiziert wurden die erhaltenen Beschichtungen durch Lanthanpromotierung. Es wurde eine maximale Raumzeitausbeute an p-Toluidin im MSR von 7 mol pro Liter und Stunde erreicht. Dies ist deutlich höher als der durch die Grenzen des Wärmetransportes limitierte Stand der Technik, der für konventionelle Rührkesselreaktoren im Bereich von 0,15 bis 1,5 mol pro Liter und Stunde liegt. Der MSR konnte damit gewinnbringend für diese Reaktion eingesetzt werden. Für die Hydrierung von Acrolein mit dem Zielprodukt Allylalkohol wurden auf Silber basierende reale und Modellkatalysatoren eingesetzt. Ziel war es, Zusammenhänge zu finden zwischen der Wahl des Katalysatorträgers und der Techniken zur Silberimmobilisierung auf der einen Seite und den katalytischen Eigenschaften des resultierenden Katalysators auf der anderen. Als Trägermaterialien wurden Aluminium und Siliziumdioxid verwendet. Die Aktivkomponente Silber wurde konventionell nasschemisch, elektrochemisch und durch Sputtern abgeschieden. Einflüsse des Trägermaterials auf Aktivität und Selektivität des Katalysators konnten deutlich von den Einflüssen der verschiedenen Techniken der Silberimmobilisierung unterschieden werden. Der Mikrostrukturreaktor konnte für diese Reaktion nicht gewinnbringend eingesetzt werden.

A lipoperoxidação gera diversas espécies carbonílicas altamente reativas dentre as quais se destacam acroleína (ACR), malondialdeído (MDA), 4-hidroxi-2-hexenal (HHE) e 4-hidroxi-2-nonenal (HNE). A principal via endógena de metabolização desses compostos é através de conjugação com glutationa por ação da glutationa-S-tranferase. Contudo, diversos trabalhos têm mostrado que dipeptídeos contendo histidina, tal como a carnosina (CAR), também podem formar conjugados com aldeídos e auxiliar na detoxificação desses compostos. Em nosso trabalho adutos de CAR com ACR, HHE, HHEd5, HNE e HNEd11 foram sintetizados, purificados e caracterizados. A reação da CAR com ACR foi estudada em detalhes. Resultados mostraram que a carnosina reage com acroleína formando 03 produtos principais: m/z = 265, m/z = 283 e m/z = 303, sendo este último mais estável e mais abundante. Dados de RMN H1, COSY e HSQC permitiram elucidar a estrutura dessa molécula (m/z = 303) e propor uma rota de reação. Em seguida, uma metodologia baseada em cromatografia líquida acoplada à espectrometria de massas do tipo \"Ion Trap\" (ESI+ HPLC/MS-MS) foi desenvolvida e validada para quantificação simultânea dos adutos sintetizados. Pelo método desenvolvido é possível quantificar com precisão 25 pmol de CAR-HHE, 1 pmol de CAR-ACR e 1 pmol de CAR-HNE com um coeficiente de variação de aproximadamente 10 % e acurácia de 98 % (HHEd5 e HNEd11 foram usados como padrão interno). Análise em urina de adultos não fumantes mostraram que os produtos sintetizados estão presentes na urina de humanos em concentrações de 3,6 ± 1,4; 2,3 ± 1,5 e 1,3 ± 0,5 nmol / mg de creatinina, respectivamente para CAR-ACR, CAR-HHE e CAR-HNE. Em ratos transgênicos SODG93A modelo para esclerose lateral amiotrófica (ELA), a suplementação da dieta dos animais com 35 ± 5 mg carnosina/animal/semana melhorou a manutenção do peso e a sobrevida dos animais. Análises dos adutos sintetizados em amostras de músculo sugerem que a metabolização de aldeídos esteja comprometida nesses animais e que a carnosina poderia funcionar como \"scavenger\" para esses compostos. Esses resultados comprovam que dipeptídeos de histidina atuam na detoxificação de compostos carbonílicos e participa de suas vias de excreção. Além disso, a caracterização da estrutura e desenvolvimento de método sensível de detecção abre a possibilidade de utilização desses adutos como biomarcadores de estresse redox e exposição a aldeídos. / Lipid peroxidation generates reactive carbonyl species, including 4-hydroxy-2-nonenal (HNE), acrolein (ACR), 4-hydroxy-2-hexenal (HHE) and malondialdehyde (MDA). One major pathway of aldehyde detoxification in vivo is through conjugation with glutathione catalyzed by glutathione-S-transferases or, alternatively, by conjugation with endogenous histidine containing dipeptides, such as carnosine (CAR). The reaction of CAR with ACR was investigated in an effort to assess its possible biological role. One stable adduct was isolated by reverse-phase HPLC and characterized on the basis of extensive spectroscopic measurements. The proposed reaction route for product formation involves the reaction of the CAR amino group with ACR via a Schiff base formation followed by dehydration and cyclization through Michael addition in the imidazole ring forming an instable compound with m/z = 265. The subsequent reaction with another molecule of ACR followed by cyclization gives rise to the final product with m/z = 303.A highly sensitive method involving HPLC-MS analysis was developed for the simultaneous accurate quantification of CAR- ACR, CAR-HHE and CAR-HNE adducts in human urinary samples from non-smoking adults. This methodology permits quantification of 10 pmol CAR-HHE and 1 pmol of CAR-ACR and CAR-HNE. Adduct levels in urine were 3.6 ± 1.4, 2.3 ± 1.5, 1.3 ± 0.5 nmol/mg of creatinine, respectively to CAR-ACR, CAR-HHE and CAR-HNE. In SODG93A transgenic rats model to amyotrophic lateral sclerosis (ALS), the food supplementation of the animals with 35 ± 5 mg carnosine/animal/week improve de body weight and the life span of the ALS treated group. Analysis of the synthesized adducts in muscle sample showed suggest than aldehyde metabolization is compromised in this animals and that may be carnosine work like a scavenger for these compounds. Our results indicate that carnosine adduction can be an important detoxification route of α,β -unsaturated aldehydes. Moreover, carnosine adducts quantification may be useful as redox stress indicator in vivo.

La déshydratation du glycérol en acroléine en phase gazeuse sur catalyseur solide a été étudiée pour comprendre la formation des sous-produits, déterminer un mécanisme réactionnel et expliquer la désactivation du catalyseur. Les expériences ont été réalisées dans un réacteur isotherme à lit fixe sous différentes conditions opératoires. Pour déterminer les chemins réactionnels de la réaction, de nombreux sous-produits ont été passés séparément sur le catalyseur. Une chromatographie gazeuse en ligne, en continu et originale a été utilisée pour analyser tous les produits de la réaction simultanément. Deux produits ont été quantifiés par chromatographie liquide et de nouveaux composés ont été identifiés par chromatographie gazeuse couplée à un spectromètre de masse. Un mécanisme réactionnel a été proposé. Pour comprendre la désactivation du catalyseur, les produits responsables du dépôt carboné ont été identifiés et la chute de la conversion du glycérol au cours du temps a été modélisée / Glycerol dehydration to form acrolein in gas phase over a solid acid catalyst was studied to understand by-products formation, to determine a detailed mechanism and to explain the deactivation process. Experiments were run in an isothermal fixed bed reactor under different operating conditions. To understand the multiple pathways of the glycerol dehydration mechanism, many by-products of the reaction were passed separately over the catalyst. An original multivalve on-line gas chromatography was used to analyze the whole reaction products continuously and simultaneously. Two products were quantified by high performance liquid chromatography, and the unknown products were identified by gas chromatography-mass spectrometry. A detailed reaction mechanism was then proposed. In order to understand the deactivation process, compounds responsible of carbon deposit were identified and the glycerol conversion fall during an experiment was modelled

This thesis describes and develops two experimental techniques, Time Resolved Photoelectron Spectroscopy (TRPES), and Time Resolved Coincidence Imaging Spectroscopy (TRCIS), to study ultrafast gas phase chemical dynamics. We use TRPES to investigate the effects of methyl substitution on the electronic dynamics of the simple alpha, beta-enones acrolein, crotonaldehyde, methylvinylketone, and methacrolein following excitation to the S2 state. We determine that following excitation, the molecules move rapidly away from the Franck-Condon region reaching a conical intersection promoting relaxation to the S1 state. Once on the S1 surface, the trajectories access another conical intersection leading them to the ground state. Only small variations between molecules are seen in their S2 decay times. However, the position of methyl group substitution greatly affects the relaxation rate from the S1 surface. Ab initio calculations used to compare the geometries, energies, and topographies of the S1/S0 conical intersections of the molecules are not able to explain the variations in relaxation behaviour. We propose a model that uses dynamical factors of specific motions in the molecules to explain the differing nonadiabatic S1/S0 crossing rates. The second part of this thesis examines the issues involved with design and construction of a Coincidence Imaging Spectrometer. This type of spectrometer measures the 3-dimensional velocities of both photoelectrons and photoions generated from probing of laser induced photodissociation reactions. Importantly, the photoelectrons and photoions are measured in coincidence from single molecules, enabling measurements such as recoil frame photoelectron angular distributions and correlated photoelectron/photoion energy maps, inaccessible using existing techniques. How to optimize the spectrometer resolution through design, tuning, and calibration is discussed. The power of TRCIS is demonstrated with the investigation of the photodissociation dynamics of the NO dimer. TRPES experiments first identified a sequential kinetic model following 209nm excitation resulting in NO(X) (ground state) and NO(A) (excited state) products. Using TRCIS, it was possible to measure time resolved vibrational energy distributions of the products, indicating the extent of vibrational energy redistribution within the dimers prior to dissociation. Recoil frame photoelectron angular distributions and theoretical support allow identification of a previously disputed intermediate on the dissociation pathway. / Thesis (Ph.D, Chemistry) -- Queen's University, 2007-04-01 10:12:39.968

Zugl.: Bayreuth, Universiẗat, Diss., 2009.

Environmental problems generated due the widespread use of fossil fuels has led the search for new energy alternatives. In this context, the biodiesel emerged as a product of great interest. However, the increase in the biofuel production leads to the production of large amounts of glycerol, which emerges as a cheap raw material with high functionality to produce different products such acrolein (currently it is obtained by selective propylene oxidation), 1,2-propanediol and others. In this study, previously, was performed a theorical and thermodynamic study of acrolein production from glycerol and others products. Catalytic tests from glycerol under different acid solid catalysts, such as materials based on alumina, niobium and zeolite, temperatures between 275 and 350°C and atmospheric pressure were performed. The catalysts were characterized by nitrogen physisorption, X-ray diffraction (XRD), temperature programmed desorption (TPD) and temperature programmed oxidation (TPO). The aim of this study is to evaluate the performance of catalysts and reaction temperature influence, in the formation of products as acrolein and acetol, main products of the reaction of dehydration of glycerol. / Problemas ambientais gerados devido ao uso generalizado de combustíveis fósseis têm levado a busca por novas alternativas energéticas. Nesse contexto, o biodiesel, surge como um combustível de grande interesse. Entretanto, o aumento na produção deste biocombustível acarreta a produção de grandes quantidades de glicerol, que por sua vez, desponta como uma matéria-prima com baixo valor de mercado e de grande funcionalidade para produção de diferentes produtos, tais como a acroleína (atualmente obtido pela oxidação seletiva do propeno), 1,2-propanodiol, entre outros. Neste trabalho, previamente foi realizado um estudo teórico e termodinâmico da reação de formação da acroleína e outras possíveis reações que podem ocorrer no sistema reacional. Testes catalíticos a partir do glicerol sob diferentes catalisadores sólidos ácidos, tais como materiais a base de alumina, nióbio e zeólita, temperaturas entre 275 e 350°C e pressão ambiente foram realizados. Os catalisadores foram caracterizados por fisissorção de nitrogênio, difratometria de raio-x (DRX), dessorção à temperatura programada (TPD) e oxidação à temperatura programada (TPO). O objetivo deste trabalho é a avaliação do desempenho de catalisadores e da influência da temperatura reacional na formação de produtos como a acroléina e acetol, principais produtos da reação de desidratação do glicerol. / Mestre em Engenharia Química

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / A viabilidade econÃmica da produÃÃo do biodiesel depende do uso do glicerol, subproduto com estrutura multifuncional, considerado matÃriaâprima bio-renovÃvel, de grande potencial para ser transformado a combustÃveis ou produtos quÃmicos de maior valor agregado. Com o intuito de contribuir para o desenvolvimento dessa linha de pesquisa, foi realizado estudo do potencial catalÃtico da γ-Al2O3 modificada com Ãxido de molibdÃnio e promotores (Cu, Ni ou Co), na reaÃÃo de desidrataÃÃo do glicerol a intermediÃrios quÃmicos com aplicaÃÃo industrial. A estratÃgia foi sintetizar esferas de Al2O3 por mÃtodo hÃbrido, as quais apresentam interessantes propriedades estruturais, texturais e quÃmicas para em seguida impregnar com precursores dos metais via mÃtodo nÃo-convencional (Pechini). A composiÃÃo dos materiais foi escolhida com o objetivo de avaliar o efeito bifuncional causado pela combinaÃÃo das propriedades Ãcido/bÃsicas e redox de catalisadores de molibdÃnio suportado em alumina. Para fins comparativos foi testado catalisador comercial Ni-Mo/Al2O3 com elevada acidez e porosidade. Os catalisadores foram caracterizados por: ICP-OES, FRX, TGA/DTA, DRX, MEV, IV, TPR-H2, TPD-CO2, isotermas de adsorÃÃo/dessorÃÃo de N2, e acidez atravÃs de adsorÃÃo de piridina. O desempenho dos catalisadores foi avaliado na desidrataÃÃo do glicerol, sob fluxo de N2 ou H2, a 1atm e 250ÂC. As mudanÃas na atividade e seletividade devido à troca do gÃs de arraste estÃo associadas a alteraÃÃes nas propriedades Ãcido/redox dos catalisadores, como sugerido pelas medidas de acidez e TPR-H2. AcroleÃna foi o principal produto observado para todos os catalisadores, porÃm a amostra contendo cobre (CuMoAl), mostrou maior atividade catalÃtica e superior seletividade a Ãlcool alÃlico, bem como produÃÃo do 1-propanol; o que està associado a transferÃncia de hidrogÃnio. Essa seletividade concorda com resultados de TPR-H2, que mostram maior influÃncia do cobre sobre a reduÃÃo do Ãxido de molibdÃnio, quando comparado aos promotores (Co ou Ni). Ao final sÃo propostos passos reacionais envolvidos na conversÃo do glicerol a Ãlcool alÃlico. / The economic viability of biodiesel production depends of the use of glycerol, by-product with multifunctional structure, considered a bio-renewable feedstock of great potential to be transformed to fuel or higher value-added chemicals products. In order to contribute to the development of this research area, study was carried out in order to explore the catalytic potential γ-Al2O3 modified with molybdenum oxide and promoter (Cu, Ni or Co) in the glycerol dehydration reaction to chemical intermediates with industrial application was performed. The strategy was to synthesize Al2O3 spheres by hybrid method with interesting structural, textural and chemical properties for then impregnating with precursors of metals via unconventional method (Pechini). The material composition was chosen with the aim of evaluating the bifunctional effect caused by the combination of acid-base and redox properties of molybdenum catalysts supported on alumina. For comparison was evaluated commercial Ni-Mo/Al2O3 catalyst with high acidity and porosidade. The catalysts were characterized for: ICP-OES, XRF, TGA/DTA, XRD, SEM, IR, H2-TPR, TPD-CO2, N2 adsorption/desorption isotherms, and acidity measurements through pyridine adsorption. The catalytic performance was evaluated in the glycerol dehydration under N2 or H2 flow at atmospheric pressure and 250ÂC. The modification in the activity and selectivity due to the change of carrier gas are attributed to the changes of acid/redox properties of the catalyst, as suggested by acidity measurements and TPR-H2. Acrolein was the main product observed for all catalysts, but the cupper containing catalyst (CuMoAl) showed higher catalytic activity and, and superior selectivity to allyl alcohol, as well as the production of 1-propanol, which is due to the hydrogen transfer. This selectivity agrees with H2-TPR results, which show stronger effect of the copper over the molybdenum oxide reduction, if compared to the others promoter (Co or Ni). At the end it is proposed the reaction steps mechanism for the glycerol conversion to allyl alcohol.

Le glycérol et le fructose sont des molécules qui peuvent être extraites facilement de labiomasse et en des quantités substantielles. Ce travail de recherche porte sur la déshydratationcomme moyen de valoriser ces composés. C’est dans ce but que des catalyseurs supportés suroxydes de zirconium et de titane, ainsi que des matériaux de type phosphate de calcium, ontété préparés et testés pour la réaction de déshydratation du glycérol en phase gazeuse. Desoxydes mixtes de niobium et cerium ainsi que des oxydes mixtes mésoporeux de Nb2O5-MeO2 (M = Ce, Zr, Ti) ont été également préparés et cette fois-ci testés pour la réaction dedéshydratation du fructose en milieu aqueux. Dans les deux cas, les propriétés acido-basiquesde surface des catalyseurs étudiés ont été corrélées à leur efficacité catalytique. / Glycerol and fructose are molecules that are readily available in substantial quantities fromthe biomass. In this work dehydration routes for valorization of these compounds wereinvestigated. Therefore, zirconia and titania based catalysts, and calcium phosphate materialswere prepared and evaluated in the glycerol dehydration in gas phase. Niobia-ceria mixedoxides and mesoporous Nb2O5-MeO2 (M = Ce, Zr, Ti) mixed oxides were prepared andtested in fructose dehydration reaction in aqueous phase. The surface acid-base properties ofthe studied catalysts were correlated to their catalytic performance.

La déshydratation du glycérol en acroléine a été étudiée sur de nouveaux catalyseurs à base d'oxydes en vue de mettre au point un nouveau procédé de production de la méthionine. Ces catalyseurs performants sont des zircones niobiées et des zircones tungstées dopées à la silice. Si les catalyseurs proposés dans la littérature jusqu'à présent pouvaient être sélectifs, ils se désactivaient rapidement par cokage. Les nouveaux catalyseurs mis au point sont aussi actifs et sélectifs mais beaucoup plus stables sous flux réactionnel. Les performances des zircones niobiées sont très sensibles à la méthode de préparation; les catalyseurs ont été caractérisés par DRX, spectroscopie Raman, MET, EDX, XPS. Ces analyses ont montré qu'une partie du niobium est incorporée dans la zircone qui est recouverte d'espèces polymères de niobium. Les zircones tungstées performantes sont constituées d'une zircone recouverte de silice et de polytunsgtates. L'acido-basicité des catalyseurs a été étudiée par différentes techniques: réactions modèles de transformation du méthylbutynol et du 2-propanol, TPD-NH3, adsorption de NH3 et SO2étudiée par microcalorimétrie et adsorption de pyridine suivie par IR. Ces études ont permis de montrer que les sites basiques de la zircone sont néfastes pour les performances et que les sites acides de Brönsted avec une large gamme de force acide sont actifs et sélectifs en acroléine. Nous avons montré par microcalorimétrie que même les sites acides très faibles participent à la réaction / Glycerol dehydration to acrolein has been studied over innovative oxide catalysts in order to develop a new methionine production process. These performing catalysts are niobiate zirconia mixed oxides and tungstated zirconia doped with silicium. The catalysts proposed so far in the literature are active and selective but they show fast deactivation under reaction flow due to coke deposition. The new catalysts appear at least as active and selective but much more stable. The niobiate zirconia mixed oxides, which catalytic performances are very sensitive to the preparation method, have been characterized by XRD, Raman spectroscopy, TEM with EDX analyses and XPS. Theses analyses show that niobium cations are partially incorporated into zirconia and covered its surface as polymeric niobium oxide species. The efficient tungstated zirconia catalysts consist of zirconia cover with silicium and polymeric tungstate species. Acid-base properties of the catalysts have been studied by model reaction of methylbutynol and 2-propanol, NH3-TPD, SO2 and NH3adsorption followed by microcalorimetry and IR spectroscopy of pyridine adsorption. These studies show that the zirconia uncovered by silica or containing no niobium are unselective sites and that Brönsted acid sites of the polymeric tungstate or niobium oxide species are the selective sites in acrolein. The strength of these sites does not appear as a key parameter to acrolein selectivity and even weak sites participate to the reaction

A lipoperoxidação gera diversas espécies carbonílicas altamente reativas dentre as quais se destacam acroleína (ACR), malondialdeído (MDA), 4-hidroxi-2-hexenal (HHE) e 4-hidroxi-2-nonenal (HNE). A principal via endógena de metabolização desses compostos é através de conjugação com glutationa por ação da glutationa-S-tranferase. Contudo, diversos trabalhos têm mostrado que dipeptídeos contendo histidina, tal como a carnosina (CAR), também podem formar conjugados com aldeídos e auxiliar na detoxificação desses compostos. Em nosso trabalho adutos de CAR com ACR, HHE, HHEd5, HNE e HNEd11 foram sintetizados, purificados e caracterizados. A reação da CAR com ACR foi estudada em detalhes. Resultados mostraram que a carnosina reage com acroleína formando 03 produtos principais: m/z = 265, m/z = 283 e m/z = 303, sendo este último mais estável e mais abundante. Dados de RMN H1, COSY e HSQC permitiram elucidar a estrutura dessa molécula (m/z = 303) e propor uma rota de reação. Em seguida, uma metodologia baseada em cromatografia líquida acoplada à espectrometria de massas do tipo \"Ion Trap\" (ESI+ HPLC/MS-MS) foi desenvolvida e validada para quantificação simultânea dos adutos sintetizados. Pelo método desenvolvido é possível quantificar com precisão 25 pmol de CAR-HHE, 1 pmol de CAR-ACR e 1 pmol de CAR-HNE com um coeficiente de variação de aproximadamente 10 % e acurácia de 98 % (HHEd5 e HNEd11 foram usados como padrão interno). Análise em urina de adultos não fumantes mostraram que os produtos sintetizados estão presentes na urina de humanos em concentrações de 3,6 ± 1,4; 2,3 ± 1,5 e 1,3 ± 0,5 nmol / mg de creatinina, respectivamente para CAR-ACR, CAR-HHE e CAR-HNE. Em ratos transgênicos SODG93A modelo para esclerose lateral amiotrófica (ELA), a suplementação da dieta dos animais com 35 ± 5 mg carnosina/animal/semana melhorou a manutenção do peso e a sobrevida dos animais. Análises dos adutos sintetizados em amostras de músculo sugerem que a metabolização de aldeídos esteja comprometida nesses animais e que a carnosina poderia funcionar como \"scavenger\" para esses compostos. Esses resultados comprovam que dipeptídeos de histidina atuam na detoxificação de compostos carbonílicos e participa de suas vias de excreção. Além disso, a caracterização da estrutura e desenvolvimento de método sensível de detecção abre a possibilidade de utilização desses adutos como biomarcadores de estresse redox e exposição a aldeídos. / Lipid peroxidation generates reactive carbonyl species, including 4-hydroxy-2-nonenal (HNE), acrolein (ACR), 4-hydroxy-2-hexenal (HHE) and malondialdehyde (MDA). One major pathway of aldehyde detoxification in vivo is through conjugation with glutathione catalyzed by glutathione-S-transferases or, alternatively, by conjugation with endogenous histidine containing dipeptides, such as carnosine (CAR). The reaction of CAR with ACR was investigated in an effort to assess its possible biological role. One stable adduct was isolated by reverse-phase HPLC and characterized on the basis of extensive spectroscopic measurements. The proposed reaction route for product formation involves the reaction of the CAR amino group with ACR via a Schiff base formation followed by dehydration and cyclization through Michael addition in the imidazole ring forming an instable compound with m/z = 265. The subsequent reaction with another molecule of ACR followed by cyclization gives rise to the final product with m/z = 303.A highly sensitive method involving HPLC-MS analysis was developed for the simultaneous accurate quantification of CAR- ACR, CAR-HHE and CAR-HNE adducts in human urinary samples from non-smoking adults. This methodology permits quantification of 10 pmol CAR-HHE and 1 pmol of CAR-ACR and CAR-HNE. Adduct levels in urine were 3.6 ± 1.4, 2.3 ± 1.5, 1.3 ± 0.5 nmol/mg of creatinine, respectively to CAR-ACR, CAR-HHE and CAR-HNE. In SODG93A transgenic rats model to amyotrophic lateral sclerosis (ALS), the food supplementation of the animals with 35 ± 5 mg carnosine/animal/week improve de body weight and the life span of the ALS treated group. Analysis of the synthesized adducts in muscle sample showed suggest than aldehyde metabolization is compromised in this animals and that may be carnosine work like a scavenger for these compounds. Our results indicate that carnosine adduction can be an important detoxification route of α,β -unsaturated aldehydes. Moreover, carnosine adducts quantification may be useful as redox stress indicator in vivo.