Aerosols of nitrate solutions were irradiated in the presence of radical scavengers in an attempt to measure the yield of hydroxyl radical in both the aqueous phase and the gas phase. Carbon monoxide, benzoic acid, benzene and cyclohexane were used as scavengers to trap hydroxyl radical. The products from the reaction of these scavengers with hydroxyl radical were analysed with High Performance Liquid Chromatography and mass spectrometry. The radiant flux in the chamber was measured via ferrioxalate actinometry, both with bulk liquid and aerosol droplets. Many quantitative results were obtained but several anomalies were found. This suggests that Mie theory is not capable of predicting rates of photochemical reactions within droplets.

Aerosols of nitrate solutions were irradiated in the presence of radical scavengers in an attempt to measure the yield of hydroxyl radical in both the aqueous phase and the gas phase. Carbon monoxide, benzoic acid, benzene and cyclohexane were used as scavengers to trap hydroxyl radical. The products from the reaction of these scavengers with hydroxyl radical were analysed with High Performance Liquid Chromatography and mass spectrometry. The radiant flux in the chamber was measured via ferrioxalate actinometry, both with bulk liquid and aerosol droplets. Many quantitative results were obtained but several anomalies were found. This suggests that Mie theory is not capable of predicting rates of photochemical reactions within droplets.

Cette thèse décrit l'étude de la dégradation chimique des membranes de type acide perfluorosulfonique (PFSA) utilisées dans les piles à combustible à membrane échangeuse de protons. L'objectif de ces travaux réside d'une part en une meilleure compréhension des mécanismes de dégradation conduisant à la défaillance des membranes et en la proposition d'approches pour limiter les phénomènes de dégradation, d'autre part. Les études relatives à la dégradation chimique des membranes ont été réalisées sur une membrane de référence Nafion et sur des membranes contenant le cérium ou le manganèse incorporé par échange ionique. L'influence de la présence des pièges à radicaux Ce et Mn sur la limitation des phénomènes de dégradation des membranes a été évaluée sous deux types de conditions de vieillissement accéléré : in situ par l'abandon sous tension à vide (OCV) de la pile à combustible et ex situ par immersion de la membrane dans le réactif de fenton. La dégradation chimique de la membrane a été appréciée par mesure du taux d'émission de fluor (FER). Le taux d'émission de fluor, mesuré sur les membranes ayant subi l'un ou l'autre des vieillissements accélérés, est plus faible pour les systèmes Nafion/Ce et Nafion/Mn, préparés par échange ionique, que pour le système de référence. Ce phénomène est accompagné d'une diminution des performances de la pile à combustible, de la migration et de l'élution des ions métalliques (évaluées par MEB/EDX et HPLC) et des changements du degré d'oxydation des espèces métalliques (déterminés par XPS). Ces résultats ont été utilisés par la suite pour définir de nouvelles approches visant à limiter la dégradation chimique des membranes. Un mat à base de nanofibre CeOx/PFSA a é té préparé par electrospinning d'une dispersion d'ionomère nafion contenant des nanoparticules de CeOx préparées par flash combustion. La technique d'electrospinning permet la préparation de matériaux homogènes, d'épaisseur contrôlée et présentant une dispersion élevée de CeOx. Ce mat a été assemblé à la membrane de PFSA par pressage à chaud. L'intérêt de l'utilisation des mats de nanofibres réside dans la possibilité de positionner le piège à radical CeOx à proximité d'une couche catalytique plutôt que de le disperser au sein de la membrane. Ces nouvelles membranes ont été vieillies par abandon de la cellule de pile à combustible à l'OCV. Les résultats obtenus ont montré que les AMEs contenant une membrane de Nafion non modifiée ou un système modifié incorporant un mat de nanofibre de PFSA (sans CeOx) à l'interface membrane-electrode présentaient d'une part une chute significative de l'OCV avec le temps de fonctionnement et un FER élevé d'autre part. A l'inverse, un AME incorporant un mat de nanofibre contenant CeOx à l'interface membrane-electrode est caractérisé par un OCV stable et un FER faible. Finalement nous avons observé que le mat de nanofibre de CeOx est plus efficace lorsqu'il est placé au voisinage de l'anode. Les analyses post mortem des AMEs et les analyses de l'eau produite après fonctionnement de la pile ont été combinées afin de dresser un tableau des processus de dégradation se produisant dans les AMEs protégés par l'oxyde de cerium et dans les AMEs non modifiés. Les analyses à partir de spectroscopie photoélectronique à rayon X, de spectroscopie Raman et de microscopie électronique à balayage ont montré un niveau de dégradation des membranes plus faible pour les systèmes contenant CeOx par rapport aux membranes de référence de typer PFSA. Ces résultats sont en accords avec le profil de l'OCV et avec le taux d'émission de fluor. En conclusion l'approche consistant dans l'incorporation de pièges à radicaux pour la réduction de la dégradation chimique des membranes permet d'augmenter significativement la durée de vie de la membrane et de positionner les pièges à radicaux à proximité des sites les plus exposés aux attaques de radicaux. / This thesis describes the study the chemical degradation of perfluorosulfonic acid (PFSA) membranes used in proton exchange membrane fuel cells, in order to gain a better understanding of the mechanisms leading to failure, and to propose strategies to mitigate this degradation. Studies of membrane chemical decomposition were performed on pristine Nafion and on cerium and manganese ion exchanged membranes. The effectiveness of Mn and Ce species as free radical scavengers was studied by using accelerated stress tests: in situ in a single fuel cell under open circuit voltage (OCV), and ex situ using Fenton's reagent. Membrane chemical degradation was assessed by the fluoride emission rate (FER). Significant reduction in FER was observed with Mn and Ce ion modified Nafion. These observations were related to the fuel cell performances losses and migration or elution of metal ions, as evaluated by SEM/EDX and HPLC, and to changes in the oxidation state of the metal species, determined by XPS. The results have been used to provide further guidance on materials strategies to mitigate membrane chemical degradation. A composite nanofibre CeOx/PFSA mat was prepared by electrospinning of a mixed dispersion of Nafion® ionomer with CeOx nanoparticles synthesised by flash combustion. The electrospinning technique allows fabrication of a homogenous material with well controlled thickness and highly dispersed CeOx. This mat was assembled with PFSA membranes by hot-pressing. These nanofibre mats are the means of siting the CeOx radical scavenger specifically in close proximity to one or other catalyst layer, rather than distributed throughout the membrane. The new membranes were further investigated by OCV hold testing in a fuel cell. The results show that MEAs integrating a non-modified PFSA membrane, or a PFSA membrane modified by an interlayer of nanofibre PFSA (no CeOx) only, demonstrate a marked drop in OCV with time, and high FER. In contrast an MEA comprising a CeOx nanofibre interlayer gives very stable open circuit voltage and low fluoride emission. Finally it was observed that the nanofibre – ceria interlayer is more effective when incorporated at the anode side. Post mortem analysis of the MEAs and analysis of exhaust water were combined to draw a picture of the overall degradation processes occurring in cerium oxide protected and non-modified MEAs. X-ray photoelectron spectroscopy, Raman spectroscopy and scanning electron microscopy analyses of aged MEAs indicated a lower degree of degradation for CeOx protected membranes than for a non-modified PFSA membrane. These results are in agreement with OCV profile and fluoride emission rate. In conclusion this new approach to the strategy of incorporating of radical scavengers to mitigate membrane chemical degradation efficiently increases membrane durability, and allows location of the radical scavenger within the MEA at the sites potentially most exposed to radical attack.

Free-radical generation is one of the primary causes of myocardial ischemia/reperfusion (I/R) injury. Melatonin is an efficient free-radical scavenger and induces the expression of antioxidant enzymes. We have previously shown that melatonin can prevent free-radical-induced myocardial injury. To date, the mechanism underlying melatonin's cardioprotective effect is not clear. In this study, we assessed the ability of melatonin to protect against I/R injury in mice deficient in glutathione peroxidase 1 (Gpx1). Mice hearts were subjected to 40 min of global ischemia in vitro followed by 45 min of reperfusion. Myocardial I/R injury (expressed as % of recovery of left ventricular developed pressure × heart rate) was exacerbated in mice deficient in Gpx1 (51 ± 3% for Gpx1+/+ mice versus 31 ± 6% for Gpx1-/- mice, P < 0.05). Administration of melatonin for 30 min protected against I/R injury in both Gpx1+/+ mice (72 ± 4.8%) and Gpx1-/- mice (63 ± 4.7%). This protection was accompanied by a significant improvement in left ventricular end-diastolic pressure and a twofold decrease in lactate dehydrogenase (LDH) level released from melatonin-treated hearts. In another set of experiments, mice were subjected to 50 min of ligation of the left descending anterior coronary artery in vivo followed by 4 hr of reperfusion. The infarct sizes, expressed as the percentage of the area at risk, were significantly larger in Gpx1-/- mice than in Gpx1+/+ mice (75 ± 9% versus 54 ± 6%, P < 0.05) and were reduced significantly in melatonin-treated mice (31 ± 3.7% Gpx1-/- mice and 33 ± 6.0% Gpx1+/+ mice). In hearts subjected to 30 min of coronary artery occlusion followed by 3 hr of reperfusion, melatonin-treated hearts had significantly fewer in situ oligo ligation-positive myocytes and less protein nitration. Our results demonstrate that the cardioprotective function of melatonin is independent of Gpx1.

Cerium oxide has been used extensively for various applications over the past two decades. The use of cerium oxide nanoparticles is beneficial in present applications and can open avenues for future applications. The present study utilizes the microemulsion technique to synthesize uniformly distributed cerium oxide nanoparticles. The same technique was also used to synthesize cerium oxide nanoparticles doped with trivalent elements (La and Nd). The fundamental study of cerium oxide nanoparticles identified variations in properties as a function of particle size and also due to doping with trivalent elements (La and Nd). It was found that the lattice parameter of cerium oxide nanoparticles increases with decrease in particle size. Also Raman allowed mode shift to lower energies and the peak at 464 cm-1 becomes broader and asymmetric. The size dependent changes in cerium oxide were correlated to increase in oxygen vacancy concentration in the cerium oxide lattice. The doping of cerium oxide nanoparticles with trivalent elements introduces more oxygen vacancies and expands the cerium oxide lattice further (in addition to the lattice expansion due to the size effect). The lattice expansion is greater for La-doped cerium oxide nanoparticles compared to Nd-doping due to the larger ionic radius of La compared to Nd, the lattice expansion is directly proportional to the dopant concentration. The synthesized cerium oxide nanoparticles were used to develop an electrochemical biosensor of hydrogen peroxide (H2O2). The sensor was useful to detect H2O2 concentrations as low as 1µM in water. Also the preliminary testing of the sensor on tomato stem and leaf extracts indicated that the sensor can be used in practical applications such as plant physiological studies etc. The nanomolar concentrations of cerium oxide nanoparticles were also found to be useful in decreasing ROS (reactive oxygen species) mediated cellular damages in various in vitro cell cultures. Cerium oxide nanoparticles reduced the cellular damages to the normal breast epithelial cell line (CRL 8798) induced by X-rays and to the Keratinocyte cell line induced by UV irradiation. Cerium oxide nanoparticles were also found to be neuroprotective to adult rat spinal cord and retinal neurons. We propose that cerium oxide nanoparticles act as free radical scavenger (via redox reactions on its surface) to decrease the ROS induced cellular damages. Additionally, UV-visible spectroscopic studies indicated that cerium oxide nanoparticles possess auto-regenerative property by switching its oxidation state between Ce3+ and Ce4+. The auto-regenerative antioxidant property of these nanoparticles appears to be a key component in all the biological applications discussed in the present study.

The antioxidant activity of novel drugs has been of increasing interest in recent years. Free radicals are linked as a cause to many diseases such as atherosclerosis and cancer,1 so development of drugs that can scavenge and break down free radicals is needed. One such potential solution is using dopamine, which is water-soluble and an antioxidant. However, the tendency of antioxidant drugs reacting undesirably with proteins and other biochemical compounds is a big issue for the drugs' antioxidant potential. One solution is by encapsulating the antioxidant compound in biocompatible polymer nanoparticles. In this project, dopamine is bound to the polymer polyacrylic acid (PAA) and spherical PAA-dopamine nanoparticles were synthesized. Following their synthesis, the nanoparticles were characterized by Dynamic Light Scattering (DLS), Transmission Electron Microscope (TEM), and Fourier-Transform Infrared (FT-IR) spectroscopy and were shown to have an average size of 90 nm after dialysis cleaning. Finally, their hydroxyl radical (OH·) scavenging ability was tested through pH changes and fluorescence, and the data acquired suggests possible radical scavenging potential.

Orientador: Adriana Zerlotti Mercadante / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-11T02:48:48Z (GMT). No. of bitstreams: 1 Barreto_GiselaPizarrodeMattos_D.pdf: 1819752 bytes, checksum: 73ae705ff5b48a9b194ef27159fe6ab1 (MD5) Previous issue date: 2008 / Resumo: O aumento da demanda dos consumidores por maior qualidade de vida tem impulsionado o interesse da indústria de alimentos pelo segmento de alimentos funcionais, definidos como qualquer alimento com potencial para conferir benefícios à saúde do consumidor. Os compostos bioativos, como os carotenóides, compostos fenólicos e ácido ascórbico, presentes em alimentos estão envolvidos nestas ações benéficas. Inicialmente, foi realizado um estudo com alguns padrões de carotenóides, que não somente apresentam atividade anti-radical livre como também são responsáveis pela cor de vários alimentos. Foi avaliado o comportamento destes carotenóides, em diferentes concentrações, em relação à sua atividade anti-radical livre (ABTS) e parâmetros de cor CIELAB. Os resultados revelaram que, o número de ligações duplas conjugadas e a presença do grupo carbonila influenciaram tanto na atividade anti-radical livre como nos parâmetros de cor dos carotenóides, assim como a concentração. Posteriormente, para a determinação da atividade anti-radical livre de extratos complexos, pelo método ABTS, foram preparadas no laboratório extratos de polpas de 18 frutas tropicais, aplicando análises estatísticas multivariadas, especificamente Análise de Componentes Principais (ACP) e Análise Hierárquica de Agrupamentos (AHA), para caracterizar e agrupar as 18 polpas de frutas e verificar a correlação entre atividade anti-radical livre e alguns constituintes químicos que apresentam funcionalidade como ácido ascórbico, compostos fenólicos, flavonóides e carotenóides totais. As frutas foram agrupadas em 5 grupos, segundo análise hierárquica de agrupamentos (AHA). Na Análise de Componentes Principais, observou-se que a atividade antioxidante apresentou alta correlação com os fenóis (r = 0,99) e flavonóides (r = 0,86) totais, porém apresentou baixa correlação com ácido ascórbico (r = 0,02) e carotenóides totais (r= 0,08). Em especial, foi estudado o caju, pois, o processamento de suco a partir do pseudofruto (pedúnculo) de caju gera como subproduto um bagaço, que constitui uma rica fonte de compostos fenólicos, ácido ascórbico (AA) e carotenóides. Considerando que este bagaço pode ser transformado para produzir ingredientes funcionais, o caju clone CCP-076, proveniente da Estação Experimental de Paraipaba (CE) da Embrapa Agroindústria Tropical, foi prensado e o bagaço obtido foi umidificado e novamente prensado até exaustão (retentado), sendo a fase líquida filtrada (extrato bruto) e concentrada (extrato concentrado). O retentado apresentou maior teor de fenóis totais, de carotenóides totais e de atividade anti-radical livre, além de apresentar cor amarela mais intensa. Por outro lado, o extrato concentrado apresentou o maior teor de AA. Os principais carotenóides encontrados, tanto no retentado como nos extratos, foram all-trans-b- criptoxantina e all-trans-b-caroteno. Uma outra fruta também analisada em separado foi o mamão papaia (Carica papaya cv. Golden) que tem uma grande demanda de exportação para os mercados da América do Norte e Europa; entretanto, é uma fruta climatérica sendo susceptível a perdas após a colheita. O mamão-papaia foi dividido em três grupos: controle (sem tratamento), etileno (tratamento com etileno) e 1- metilciclopropeno (1-MCP) (tratamento com 1-MCP). A composição de carotenóides e os parâmetros de cor de todos os grupos foram determinados durante o amadurecimento da fruta. A presença do gás etileno e 1-MCP reduziram o teor de carotenóides e favoreceram a biossíntese de carotenóides acíclicos. Entretanto, mesmo com menor teor de carotenóides que o grupo controle, os valores de cor (a*, b*) foram similares nos três grupos durante o amadurecimento / Abstract: The increased demand for high life quality has been associated to healthy food, increasing the industry interest for functional foods, which are defined as any food or bioactive compounds with potential to be benefic for the consumer health. The bioactive compounds found in foods, such as carotenoids, phenolic compounds and ascorbic acid (AA) are involved with these benefic actions. Firstly, some carotenoid standards in different concentrations were evaluated regarding not only their radical scavenger activity, but also their color parameters (CIELAB), since these pigments are responsible for the color of many foods. The results showed that the number of conjugated double bonds, presence of carbonyl group and concentration influenced both the radical scavenger activity and the color parameters. After that, the radical scavenger activity of complex extracts were determined, by ABTS assay, obtained from pulps extracts prepared in the laboratory from 18 tropical fruit applying Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) to characterize and grouped the 18 extracts, as well as to correlate radical scavenger and the bioactive compounds, such as AA, phenolic compounds, flavonoids and total carotenoids. The fruits were divided into five groups, following Hierarchical Cluster Analysis (HCA). Principal Component Analysis (PCA) indicated that antioxidant activity showed high correlation to total phenolic compounds (r= 0.99) and flavonoids (r= 0.86); however, correlation was found to be very poor with AA (r= 0.02) and total carotenoid levels (r= 0.08). The cashew-apple was specially evaluated since the processing of juice from the cashew-apple fruit generates a pomace that constitutes a rich source of phenolic compounds, AA and carotenoids. Considering that this pomace can be processed into functional ingredients, the cashew-apple clone CCP-076, from Estação Experimental de Paraipaba (CE) at Embrapa Agroindústria Tropical, was pressed and than the pomace formed was humidified and pressed again until exhaustion (retentado), followed by filtration (raw extract) and concentration (concentrated extract). The retentado presented significantly higher total phenol and total carotenoid contents, higher free radical scavenger activity, as well as higher yellow color intensity, indicated by higher b* and chroma (C*) values. On the other hand, the concentrated extract showed the highest AA content. The major carotenoids identified in both retentado and extracts were all-trans-b-cryptoxanthin and all-trans-b-carotene. These results showed that the retentado has a good potential to be applied as a functional ingredient. Another fruit also specially analyzed was the papaya fruit (Carica papaya cv. Golden) that has a great export demand to North American and Europe markets; however, since it is a climacteric fruit, it is susceptible to postharvest losses. The papaya fruits were divided into three groups: control (without treatment), ethylene (treated with ethylene) and 1-methylcyclopropene (1-MCP) (treated with 1-MCP). In all groups, carotenoid composition, carried out by HPLC, and color parameters were evaluated during ripening. The treatment with ethylene and 1-MCP decreased carotenoid accumulation and enhanced acyclic carotenoid biosynthesis. Although the gas treated fruits presented lower carotenoid content as compared to the control, the color values (a*, b*) were similar in treated and non-treated fruits during ripening / Doutorado / Doutor em Ciência de Alimentos

La fonctionnalisation de surface par réduction de précurseurs diazoniums est une puissante méthode de fonctionnalisation de surface. Cependant, bien que cette approche permette l’obtention de matériaux robustes, elle reste encore mal maîtrisée et conduit systématiquement à l’élaboration de films organiques épais, non reproductibles, et structurellement désorganisés. Dans ce contexte, nous avons développé une méthodologie permettant le contrôle du greffage dans le but de réaliser des matériaux organisés et reproductibles. Basée sur l’utilisation de piégeur de radicaux, cette méthode a permis l’obtention d’une monocouche sur un substrat carboné. La stratégie de contrôle a ensuite été exploitée pour bloquer sélectivement le mécanisme radicalaire et évaluer le rôle des mécanismes non-radicalaires dans le processus de greffage. Cette étude a permis une meilleure caractérisation du processus de greffage et mis en lumière l’impact du substituant du précurseur diazonium sur le processus de croissance du film organique. L’exploitation de ces connaissances a été mise à profit via la réalisation d’une plateforme monocouche multifonctionnelle. L’étude des relations structures/propriété a révélé des performances accrues en matière de transfert électronique et d’électro catalyse. Pour finir, la transposition de la méthode de contrôle à un greffage de type spontané a fourni un résultat similaire à celui observé pour le greffage électro-induit. L’approche a été validée par l’optimisation des performances d’un super condensateur réalisé à base de matériaux carbonés dispersés. / The surface functionalization by diazonium salt reduction is a powerful grafting method. However, despite that this approach allows the preparation of robust materials, it leads to thick and unorganized organic films. In this context, we have developped a method allowing the grafting control in order to obtain films having controlled thickness. Based on the use of radical scavengers, this method gives access to monolayer formations on carbon substrates. The control strategy was then exploited to selectively block the radical grafting mechanism and allows to assess the role of non-radical mechanisms in the process. This study provided a better understanding of the layer growth, highlighting the impact of precursor substituent.This knowledge has been used to elaborate a multifunctional platform monolayer. The establishment of sutructure/properties relathionships revealed better performances for electronic transfert and electrocatalysis. Finally, the control method was transposed to the spontaneous grafting and gives similar results than those obtained for the electrochemical one. This approach was validated by the performance optimization of supercapacitor made of carbon powder.

Η νευρολογικές διαταραχές και κυρίως η παραπληγία, αποτελούν τις πιο καταστροφικές επιπλοκές των επεμβάσεων στη θωρακο-κοιλιακή αορτή. Η διαδικασία ισχαιμίας/επαναιμάτωσης κατά τις επεμβάσεις αυτές λόγω του αποκλεισμού της αορτής, προκαλεί την ανάπτυξη τοξικών ελεύθερων ριζών οξυγόνου φαινόμενο που ορίζει το οξειδωτικό stress. Ο σκοπός της παρούσας μελέτης είναι ο καθορισμός και η ανίχνευση των ελευθέρων ριζών, αλλά και η επίδραση της Αμιφοστίνης, ενός αντιοξειδωτικού παράγοντα της κατηγορίας των θειολών. Μέθοδος: Η μέθοδος αφορά δεκαοκτώ αρσενικούς κονίκλους που υποβάλλονται σε ισχαιμία του νωτιαίου μυελού με αποκλεισμό της αορτής με τη χρήση ενδο-αορτικού ασκού. Ο ασκός προωθείται μέσω της μηριαίας αρτηρίας σε επίπεδο αμέσως κάτωθεν της αριστεράς υποκλειδίου αρτηρίας. Τα ζώα αποτελούσαν τρείς ομάδες. Η Ομάδα Ι αποτέλεσε την ομάδα ελέγχου. Στην Ομάδα ΙΙ η αορτή αποκλείσθηκε για 30΄και ακολούθησε επαναιμάτωση για 75΄. Στην Ομάδα ΙΙΙ χορηγήθηκε Αμιφοστίνη μέσω του καθετήρα αποκλεισμού κατά το δεύτερο ήμισυ της περιόδου αποκλεισμού (των 30΄). Στο τέλος της επαναιμάτωσης δείγματα νωτιαίου μυελού υποβλήθηκαν σε ανάλογη επεξεργασία για την ανίχνευση ελευθέρων ριζών οξυγόνου με τη χρήση υδροεθιδίνης και παραγώγων λιπιδικής υπεροξείδωσης με ιδιαίτερα ευαίσθητη μέθοδο φθορισμού. Αποτελέσματα: Τα αποτελέσματα των μετρήσεων έδειξαν αύξηση του υπεροξειδίου του οξυγόνου στην Ομάδα ΙΙ κατά 27.43% σχετικά με την Ομάδα Ι για να ακολουθήσει μείωση στην Ομάδα ΙΙΙ κατά 42.55% σε σχέση με την Ομάδα ΙΙ και κατά 15.25% από την Ομάδα ΙΙΙ. Η μέτρηση ενώσεων λιπιδικής υπεροξείδωσης που αντιδρούν με θειοβαρβιτουρικό οξύ (TBARSassay) έδειξε αύξηση κατά 55.3% στην Ομάδα ΙΙ σε σχέση με την Ομάδα Ι και μείωση κατά 30.3% στην Ομάδα ΙΙΙ σε σχέση με την Ομάδα ΙΙ. Η στατιστική ανάλυση και των δύο μεθόδων ανέδειξε σημαντική διαφορά με ( p<0.05). Συμπεράσματα: Ο αποκλεισμός της κατιούσας αορτής σε επίπεδο αμέσως κάτωθεν της αριστεράς υποκλειδίου αρτηρίας, προκαλεί αναμφισβήτητα ισχαιμία του νωτιαίου μυελού. Η ανάπτυξη οξειδωτικού stressως αποτέλεσμα της διαδικασίας ισχαιμία/επαναιμάτωση ανιχνεύεται μέσω των ριζών υπεροξειδίου και παραγώγων λιπιδικής υπεροξείδωσης. Η έγχυση Αμιφοστίνης προτείνεται ως αντιοξειδωτικός παράγων που μπορεί να ανιχνεύσει και να δεσμεύσει τις ελεύθερες ρίζες οξυγόνου κατά το οξειδωτικό stress που προκαλεί η ισχαιμία /επαναιμάτωση του νωτιαίου μυελού. / Paraplegia is the most devastating complication of thoraco-abdominal aortic procedures. An ischemia-reperfusion procedure is known to elevate free radicals causing oxidative stress. The aim of this study is to determine and to detect the free radical products and to examine the influence of Amifostine, a triphosphate agent, on oxidative stress of spinal cord ischemia-reperfusion in rabbits. Methods: Eighteen male, New Zealand white rabbits were anesthetized and spinal cord ischemia was induced by inflation of a coronary artery balloon catheter, advanced to descending thoracic aorta through the femoral artery. The animals were randomly divided into 3 groups. Group I functioned as control. In group II the aorta was occluded for 30 minutes and then re-perfused for 75 min. In group III, 500mg Amifostine was infused into the distal aorta during the second half-time of ischemia period. At the end of reperfusion all animals were sacrificed and spinal cord specimens were examined for superoxide radicals by an ultra sensitive fluorescent assay. Results: Superoxide radical levels ranged, in group I between 1.52 and 1.76 (1.64±0.10), in group II between 1.96 and 2.50 (2.10±0.21), and in group III (amifostine) between 1.21 and 1.60 (1.40±0.13) (p=0.00), showing a decrease of 43% in the Group of Amifostine. A lipid peroxidation marker measurement ranged, in group I between 0.28 and 0.31 (0.30±0.01), in group II between 0.427 and 0.497 (0.466±0.024), and in group III (amifostine) between 0.343 and 0.357 (0.36±0.005) (p<0.00), showing a decrease of 38% after Amifostine administration. Conclusions: Occlusion of aorta below left subclavian artery causes spinal cause ischemia without the interference of collateral perfusion. Modified use of hydrο-ethidine is a useful assay for the detection of superoxide radicals. By direct and indirect methods of measuring the oxidative stress of spinal cord after ischemia/reperfusion, it is suggested that intra-aortic Amifostine infusion significantly attenuated the spinal cord oxidative injury.

Piptadenia stipulacea belongs to the Fabaceae family,and is widely distributed in the caatinga. This species is commonly known in the Brazilian Northeast as jurema-branca , carcará and rasga-beiço , and is used in folk medicine in inflammation.In this study, we attempted to identify the possible antinociceptive and anti-inflammatory activities of the aqueous phase, the ethyl acetate phase and one flavonoid obtained from aerial parts of Piptadenia stipulacea. Aerial parts of Piptadenia stipulaceawere used and after fractionation, the flavonoid Galetin 3,6-dimethyl ether(FGAL) was obtained of the chloroformic phase of this plant. Experiments were conducted on Swiss mice using the acetic acid-induced writhing test, the hot plate test, the formalin test and zymosan A-induced peritonitis test. To characterize the mechanism(s) responsible for these antinociceptive and anti-inflammatory actions of FGAL, COX inhibitor screening assay kit and test of DPPH was used. The aqueous and ethyl acetate phases (100 mg/kg, p.o.); and the flavonoid FGAL (100 &#956;mol/kg, p.o. or i.p.), reduced the nociception produced by acetic acid, by 49,9 ± 11,2, 54,6 ± 5,3, 39,0 ± 6,8 and64,8% ± 8,1, respectively. As FGAL have greater antinociceptive activity when administered intraperitoneally compared to oral route, we chose this route you follow up the study with FGAL. The ethyl acetate phase (100 mg/kg, p.o.) reduced nociception in the hot plate, indicating that this fraction exhibited central activity. The ethyl acetate phase (100 mg/kg, p.o.) reduced the formalin effects in both phases by 40,2± 10,3 and59,9% ± 6,5, respectively. Treatment with the aqueous phase (100 mg/kg, p.o.) and FGAL (100_mol/kg, i.p.) only protected the second phase by 78,5± 5,5 and 64,0% ± 8,0, respectively. In addition, it was observed in the zymosan A-induced peritonitis test that the aqueous phase, the ethyl acetate phase and FGAL exhibited anti-inflammatory activity, reducing significantly the number of recruit cells by 35,8 ± 4,9, 37,7 ± 6,2 and 31,3% ± 13,3, respectively. Moreover, FGAL at 0,2&#956;M was able to inhibit COX-1 (79,5% ± 0,6) and COX-2 (56,0% ± 3,8), with an inhibition profile similar to indomethacin in the same concentration (93.0 ±2.6and79.0±1.5%, respectively), showinginhibitionofCOX-1 in greaterproportionthanCOX-2. Furthermore, indomethacin was more effective, both COX-1 andCOX-2 when compared to FGAL. In the test of DPPH, FGAL showed high radical scavenging activity. These results infer that the aqueous phase, the ethyl acetate phase and FGAL obtained from aerial parts of Piptadeniastipulacea are able to modulate the peripheral nociception and acute inflammatory response. TheflavonoidFGALinhibitCOX-1 andCOX-2, probably for its ability to scavenge free radicals, this being one of its mechanism of action in nociception and inflammation. Moreover, the results corroborate the popular use of Piptadenia stipulacea by their anti-inflammatory property. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Piptadenia stipulacea,pertence à família Fabaceae, é amplamente distribuída na caatinga. Esta espécie é conhecida no Nordeste brasileiro como jurema-branca, carcará e rasga-beiço, sendo utilizada na medicina popular para tratar inflamação. Neste trabalho, buscou-se investigar a atividade antinociceptiva e anti-inflamatória da fase aquosa, fase acetato de etila e de um flavonoide isolado das partes aéreas de Piptadenia stipulacea. As partes aéreas de Piptadenia stipulacea foram usadas para o fracionamento e, posteriormente o flavonóide galetina 3,6-dimetil éter(FGAL)foi obtido da fase clorofórmica da planta. Experimentos foram realizados em camundongos Swiss usando o modelo de contorções abdominais induzidas por ácido acético, ensaio da placa quente, teste de formalina e peritonite induzida por zymosan A. Para caracterizar o mecanismo de ação de FGAL responsável por sua ação antinociceptiva, o ensaio de inibição de cicloxigenase (COX) in vitro e a análise da atividade sequestrante radicalar através do método fotocolorimétrico de consumo de 2,2-difenil-1-picrihidrazila(DPPH) foram utilizados. As fases aquosa e acetato de etila(100 mg/kg, v.o.); e o flavonoide FGAL (100 &#956;mol/kg, v.o. ou i.p.) reduziram a nocicepção produzida por ácido acético, na proporção de 49,9 ± 11,2, 54,6 ± 5,3, 39,0 ± 6,8 e 64,8% ± 8,1, respectivamente.Por FGAL apresentar maior atividade antinociceptiva ao ser administrado pela via intraperitoneal quando comparado com a via oral, escolheu-se essa via para dar sequência ao estudo com FGAL. Posteriormente, verificou-se também a inibição da nocicepção no ensaio de placa quente através do tratamento com a fase acetato de etila (v.o., 100 mg/kg), indicando que esta fase apresenta atividade central. A fase acetato de etila (v.o., 100 mg/kg) reduziu a nocicepção gerada pela aplicação de formalina em ambas as fases do teste, apresentando porcentagem de inibição de 40,2 ± 10,3e 59,9% ± 6,5, respectivamente. O tratamento com a fase aquosa (100 mg/kg, v.o.) e FGAL (100 &#956;mol/kg, i.p.) apenas se mostraram ativos na segunda fase do teste de formalina na proporção de 72,6± 5,5 e 66,0% ± 8,0, respectivamente. Além disso, as fases aquosa (100 mg/kg, v.o.), acetato deetila (100 mg/kg, v.o.) e FGAL (100 &#956;mol/kg, i.p.) tambémapresentaram efeito anti-inflamatório significante quando comparadas ao grupo controle, apresentando porcentagem de inibição de recrutamento celular na peritonite induzida por zymosan A de 35,8 ± 4,9, 37,7 ± 6,2 e 31,3% ± 13,3, respectivamente.FGAL, na concentração de 0,2 &#956;M inibiu COX-1 (79,5% ± 0,6) e COX-2 (56,0% ± 3,8), com um perfil de inibição similar ao observado para indometacina na mesma concentração (93,0 ± 2,6 e 79,0% ± 1,5, respectivamente), apresentando inibição de COX-1 em maior proporção do que COX-2. Além disso, indometacina inibiu de forma mais eficaz, tanto COX-1 como COX-2 quando comparado a FGAL. No teste de2,2-difenil-1-picriidrazila(DPPH), FGAL, na concentração de 0,3 mM, mostrou alta atividade sequestrante radicalar. Estes resultados inferem que a fase aquosa, a fase acetato e FGAL obtidos das partes aéreas de Piptadenia stipulacea são capazes de modular a antinocicepção e a resposta inflamatória aguda.O flavonoide FGAL inibe COX-1 e COX-2, provavelmente por sua capacidade de sequestrar radicais livres, sendo este um dos seus mecanismos de ação na nocicepção e inflamação. Além disso, os resultados encontrados corroboram com o uso popular de Piptadenia stipulacea por suas propriedade anti-inflamatória.