Oxigênio molecular singlete [O2(1Δg)], uma espécie excitada, desempenha um papel importante em sistemas químicos e biológicos. É um poderoso eletrófilo, que reage com moléculas ricas em elétrons através de cicloadições [2+2], [4+2] e reações tipo ene. Ácidos graxos poliinsaturados, proteínas e DNA são alvos vulneráveis para o ataque de O2(1Δg). Os endoperóxidos de derivados de naftaleno são muito úteis e versáteis como fontes limpas de O2(1Δg), uma vez que são quase quimicamente inertes. Por outro lado, o desenvolvimento de novas fontes de O2(1Δg) ainda é uma tarefa desafiadora. Os derivados de naftaleno são capazes de armazenar O2(1Δg) por reação de cicloadiação [4+2] e liberá-lo em temperaturas amenas, o que os torna muito adequados para uso em estudos biológicos. A síntese destes compostos está baseada em modificações nos substituintes ligados nas posições 1 e 4 da estrutura do naftaleno. Na primeira parte deste trabalho, a síntese de três endoperóxidos derivados do naftaleno solúveis em água foi realizada. DHPNO2 e NDPO2 foram preparados de acordo com métodos similares descritos na literatura. A síntese de um novo endoperóxido dicatiônico derivado do naftaleno (NBTEO2) foi desenvolvida, contendo dois grupos de cloreto de amônio quaternário nas posições 1,4 do anel aromático. O intermediário chave na síntese dos três endoperóxidos é o BBMN, o qual foi preparado a partir da bromação radicalar do 1,4-dimetilnaftaleno. Nossos resultados têm indicado que este composto dicatiônico pode ser uma fonte química de O2(1Δg) em potencial, e pode ser explorado em estudos com mitocôndrias, onde o papel biológico de O2(1Δg) é investigado. A segunda parte deste trabalho foi dedicada a investigar a geração de O2(1Δg) através das reações entre hidroperóxidos de lipídeos (ácido oleico, linoleico e colesterol), hidroperóxidos orgânicos (cumeno e t-butila), bem como peróxido de hidrogênio com NO2+, utilizando o composto NO2BF4. Evidências da geração de O2(1Δg) foram obtidas através de medidas de emissão de luz na região do infravermelho próximo, no comprimento de onda de 1270 nm. Além disso, a prova inequívoca da presença de O2(1Δg) foi demonstrada através da caracterização espectral direta da emissão de luz no infravermelho próximo. O uso de azida de sódio como captador físico de O2(1Δg), juntamente com as medidas da quimiluminescência, contribuíram para identificar a geração desta espécie na reação entre hidroperóxidos de lipídeos e NO2BF4. Embora seja uma abordagem química, nossos resultados adicionaram informações importantes sobre a peroxidação lipídica, principalmente quando espécies reativas de nitrogênio estão envolvidas. O O2(1Δg) poderia ser gerado como um subproduto da peroxidação lipídica em condições onde espécies reativas de nitrogênio interagem com hidroperóxidos lipídicos. Isto pode contribuir para um melhor entendimento deste evento complexo com implicações fisiológicas ou fisiopatológicas. / Singlet molecular oxygen [O2(1Δg)], an excited species, plays an important role in chemical and biological systems. It is a powerfull electrophile, reacting with electron rich molecules through [2+2] cycloadditions, [4+2] cycloadditions and ene reactions. Polyunsaturated fatty acids, proteins and DNA are vulnerable targets for O2(1Δg) reaction. Naphthalene derivatives endoperoxides are very useful and versatile as a clean source of O2(1Δg), once they are almost chemically inert. On the other hand, developing new sources of O2(1Δg) are still a challenging task. Naphthalene derivatives are able to trap O2(1Δg) by [4+2] cycloaddition and release it in mild temperatures, which make them very suitable for biological studies. The synthesis of these compounds is based on modifications in substituents bonded in 1,4 positions of nafhthalene backbone. In the first part of present work, the synthesis of three water soluble naphthalene derivatives endoperoxides was performed. DHPNO2, NDPO2 were prepared according to similar methods described in the literature. A new di-cationic naphthalene derivative endoperoxide (NBTEO2) synthesis was developed, containing two quaternary ammonium chloride groups in 1,4-positions of aromatic ring. The key intermediate: for the synthesis of the three endoperoxides is the compound BBMN, which was prepared from radicalar bromination of 1,4-dimethylnaphthalene. Our results have indicated that this di-cationic compound can be a potential chemical source of O2(1Δg) and may be explored in mitochondrial studies where O2(1Δg) biological role is investigated. The second part of this work is dedicated to the investigation of generation of O2(1Δg) through reaction of lipid hydroperoxides (oleic acid, linoleic acids and cholesterol), organic hydroperoxides (cumene and t-butyl), as well as hydrogen peroxide with NO2+, using the compound NO2BF4. Evidences of generation of O2(1Δg) were obtained recording the monomol light emission measurement in near infrared region at wavelength of 1270 nm. Moreover, the proof of the presence of O2(1Δg) was unequivocally demonstrated by the direct spectral characterization of near-infrared light emission. The use of sodium azide as a physical quencher of O2(1Δg), associated to chemiluminescence measurements, contributed to identify the generation of this species in the reaction of lipid hydroperoxides and NO2BF4. Although, it is a chemical approach, our results add important information about lipid peroxidation, mainly when reactive species of nitrogen are involved. O2(1Δg) might be generate as a byproduct of lipid peroxidation, in conditions where reactive nitrogen species interact with lipid hydroperoxides. This might contribute to a better understand of this complex event and physiological or physiopathological implications

<p>Lipid peroxidation is thought to be an important factor in the pathophysiology of a number of diseases and in the process of ageing, but its measurement <i>in vivo</i> has been difficult. The aim of this thesis was to evaluate methods for measurement of lipid peroxidation <i>in vivo</i> that are suitable for clinical investigations, and to apply these methods in animal and human studies investigating basal conditions and situations associated with increased lipid peroxidation.</p><p>The ferrous oxidation in xylenol orange assay for quantification of total plasma lipid hydroperoxides was re-evaluated regarding sample handling and storage. It was shown to be a useful tool for analyses of fresh but not stored plasma samples.</p><p>A methodology for measurement of the total amount (sum of free and esterified) of an F₂-isoprostane, 8-iso-prostaglandin F_2α, in tissues using alkaline hydrolysis in combination with an existing radioimmunoassay was developed. High levels of 8-iso-prostaglandin F_2α in rat liver tissue were quantified by this technique both at basal conditions and in an experimental model of increased lipid peroxidation induced by carbon tetrachloride.</p><p>Supplementation with vitamin E to rats decreased both non-enzymatic and enzymatic lipid peroxidation as measured by 8-iso-prostaglandin F_2α and a major prostaglandin F_2α metabolite. This was verified both in the urine at basal conditions, and in the urine and liver tissue after carbon tetrachloride induced lipid peroxidation.</p><p>In a randomised cross-over study in humans, a rapeseed oil-based diet with an increased proportion of easily oxidised polyunsaturated fatty acids was compared to a control diet rich in saturated fats. The rapeseed oil-based diet did not seem to increase the degree of lipid peroxidation in plasma and urine as measured by 8-iso-prostaglandin F_2α, hydroperoxides and malondialdehyde, presumably due to a sufficient content of antioxidants in the rapeseed oil diet.</p><p>In conclusion, the simultaneous measurement of several biomarkers of lipid peroxidation is a promising approach for future studies investigating the possible role of lipid peroxidation <i>in vivo</i> under basal conditions and in the pathology of diseases.</p>

Lipid peroxidation is thought to be an important factor in the pathophysiology of a number of diseases and in the process of ageing, but its measurement in vivo has been difficult. The aim of this thesis was to evaluate methods for measurement of lipid peroxidation in vivo that are suitable for clinical investigations, and to apply these methods in animal and human studies investigating basal conditions and situations associated with increased lipid peroxidation. The ferrous oxidation in xylenol orange assay for quantification of total plasma lipid hydroperoxides was re-evaluated regarding sample handling and storage. It was shown to be a useful tool for analyses of fresh but not stored plasma samples. A methodology for measurement of the total amount (sum of free and esterified) of an F2-isoprostane, 8-iso-prostaglandin F2α, in tissues using alkaline hydrolysis in combination with an existing radioimmunoassay was developed. High levels of 8-iso-prostaglandin F2α in rat liver tissue were quantified by this technique both at basal conditions and in an experimental model of increased lipid peroxidation induced by carbon tetrachloride. Supplementation with vitamin E to rats decreased both non-enzymatic and enzymatic lipid peroxidation as measured by 8-iso-prostaglandin F2α and a major prostaglandin F2α metabolite. This was verified both in the urine at basal conditions, and in the urine and liver tissue after carbon tetrachloride induced lipid peroxidation. In a randomised cross-over study in humans, a rapeseed oil-based diet with an increased proportion of easily oxidised polyunsaturated fatty acids was compared to a control diet rich in saturated fats. The rapeseed oil-based diet did not seem to increase the degree of lipid peroxidation in plasma and urine as measured by 8-iso-prostaglandin F2α, hydroperoxides and malondialdehyde, presumably due to a sufficient content of antioxidants in the rapeseed oil diet. In conclusion, the simultaneous measurement of several biomarkers of lipid peroxidation is a promising approach for future studies investigating the possible role of lipid peroxidation in vivo under basal conditions and in the pathology of diseases.

Thesis (PhD) -- Macquarie University, Division of Environmental and Life Sciences, Dept. of Chemistry and Biomolecular Sciences, 2007. / Bibliography: leaves 295-322. / Generation of peroxide groups in proteins exposed to a wide variety of reactive oxygen species (ROS) requires an initial formation of protein carbon-centred or peroxyl free radicals, which can be reduced to hydroperoxides. Both protein radicals and protein hydroperoxides are capable of oxidizing important biomolecules and thus initiate biological damage. In this study, we investigated the inhibition of protein hydroperoxide formation by ascorbate and GSH in gamma-irradiated HL-60 cells.--We used HL-60 cells as a model for general protection of living organisms by ascorbate (Asc) and glutathione (GSH) from the deleterious effects of protein hydroperoxides generated by radicals produced by gamma radiation. Measurement by HPLC indicated that incubation of HL-60 cells with Asc in the presence of ascorbate oxidase resulted in the accumulation of intracellular Asc. The intracellular Asc levels were lowered by irradiation, demonstrating intracellular consumption of Asc by the radiation-generated radicals. Exposure of HL-60 cells to increasing gamma irradiation doses resulted in increasing accumulation of protein peroxides in the cells. This was measured by the FOX assay. A significant decrease in intracellular protein hydroperoxides was noted when the cells were treated with ascorbic acid before irradiation. A dose-dependent protective effect of Asc was observed. Asc loading also provided strong protection from radiation-generated protein hydroperoxides independently of the composition of the external medium, showing that only the radicals formed within the cells were effective in oxidizing the cell proteins. Similarly, protein peroxidation was inhibited in cells with enhanced levels of GSH and increased when the intracellular GSH concentration was reduced. These findings indicate that ascorbate and GSH are important antioxidants in protecting cells from oxidative stress associated with the generation of protein hydroperoxide. / Mode of access: World Wide Web. / xxix, 322 leaves ill

Oxigênio molecular singlete [O2(1&#916;g)], uma espécie excitada, desempenha um papel importante em sistemas químicos e biológicos. É um poderoso eletrófilo, que reage com moléculas ricas em elétrons através de cicloadições [2+2], [4+2] e reações tipo ene. Ácidos graxos poliinsaturados, proteínas e DNA são alvos vulneráveis para o ataque de O2(1&#916;g). Os endoperóxidos de derivados de naftaleno são muito úteis e versáteis como fontes limpas de O2(1&#916;g), uma vez que são quase quimicamente inertes. Por outro lado, o desenvolvimento de novas fontes de O2(1&#916;g) ainda é uma tarefa desafiadora. Os derivados de naftaleno são capazes de armazenar O2(1&#916;g) por reação de cicloadiação [4+2] e liberá-lo em temperaturas amenas, o que os torna muito adequados para uso em estudos biológicos. A síntese destes compostos está baseada em modificações nos substituintes ligados nas posições 1 e 4 da estrutura do naftaleno. Na primeira parte deste trabalho, a síntese de três endoperóxidos derivados do naftaleno solúveis em água foi realizada. DHPNO2 e NDPO2 foram preparados de acordo com métodos similares descritos na literatura. A síntese de um novo endoperóxido dicatiônico derivado do naftaleno (NBTEO2) foi desenvolvida, contendo dois grupos de cloreto de amônio quaternário nas posições 1,4 do anel aromático. O intermediário chave na síntese dos três endoperóxidos é o BBMN, o qual foi preparado a partir da bromação radicalar do 1,4-dimetilnaftaleno. Nossos resultados têm indicado que este composto dicatiônico pode ser uma fonte química de O2(1&#916;g) em potencial, e pode ser explorado em estudos com mitocôndrias, onde o papel biológico de O2(1&#916;g) é investigado. A segunda parte deste trabalho foi dedicada a investigar a geração de O2(1&#916;g) através das reações entre hidroperóxidos de lipídeos (ácido oleico, linoleico e colesterol), hidroperóxidos orgânicos (cumeno e t-butila), bem como peróxido de hidrogênio com NO2+, utilizando o composto NO2BF4. Evidências da geração de O2(1&#916;g) foram obtidas através de medidas de emissão de luz na região do infravermelho próximo, no comprimento de onda de 1270 nm. Além disso, a prova inequívoca da presença de O2(1&#916;g) foi demonstrada através da caracterização espectral direta da emissão de luz no infravermelho próximo. O uso de azida de sódio como captador físico de O2(1&#916;g), juntamente com as medidas da quimiluminescência, contribuíram para identificar a geração desta espécie na reação entre hidroperóxidos de lipídeos e NO2BF4. Embora seja uma abordagem química, nossos resultados adicionaram informações importantes sobre a peroxidação lipídica, principalmente quando espécies reativas de nitrogênio estão envolvidas. O O2(1&#916;g) poderia ser gerado como um subproduto da peroxidação lipídica em condições onde espécies reativas de nitrogênio interagem com hidroperóxidos lipídicos. Isto pode contribuir para um melhor entendimento deste evento complexo com implicações fisiológicas ou fisiopatológicas. / Singlet molecular oxygen [O2(1&#916;g)], an excited species, plays an important role in chemical and biological systems. It is a powerfull electrophile, reacting with electron rich molecules through [2+2] cycloadditions, [4+2] cycloadditions and ene reactions. Polyunsaturated fatty acids, proteins and DNA are vulnerable targets for O2(1&#916;g) reaction. Naphthalene derivatives endoperoxides are very useful and versatile as a clean source of O2(1&#916;g), once they are almost chemically inert. On the other hand, developing new sources of O2(1&#916;g) are still a challenging task. Naphthalene derivatives are able to trap O2(1&#916;g) by [4+2] cycloaddition and release it in mild temperatures, which make them very suitable for biological studies. The synthesis of these compounds is based on modifications in substituents bonded in 1,4 positions of nafhthalene backbone. In the first part of present work, the synthesis of three water soluble naphthalene derivatives endoperoxides was performed. DHPNO2, NDPO2 were prepared according to similar methods described in the literature. A new di-cationic naphthalene derivative endoperoxide (NBTEO2) synthesis was developed, containing two quaternary ammonium chloride groups in 1,4-positions of aromatic ring. The key intermediate: for the synthesis of the three endoperoxides is the compound BBMN, which was prepared from radicalar bromination of 1,4-dimethylnaphthalene. Our results have indicated that this di-cationic compound can be a potential chemical source of O2(1&#916;g) and may be explored in mitochondrial studies where O2(1&#916;g) biological role is investigated. The second part of this work is dedicated to the investigation of generation of O2(1&#916;g) through reaction of lipid hydroperoxides (oleic acid, linoleic acids and cholesterol), organic hydroperoxides (cumene and t-butyl), as well as hydrogen peroxide with NO2+, using the compound NO2BF4. Evidences of generation of O2(1&#916;g) were obtained recording the monomol light emission measurement in near infrared region at wavelength of 1270 nm. Moreover, the proof of the presence of O2(1&#916;g) was unequivocally demonstrated by the direct spectral characterization of near-infrared light emission. The use of sodium azide as a physical quencher of O2(1&#916;g), associated to chemiluminescence measurements, contributed to identify the generation of this species in the reaction of lipid hydroperoxides and NO2BF4. Although, it is a chemical approach, our results add important information about lipid peroxidation, mainly when reactive species of nitrogen are involved. O2(1&#916;g) might be generate as a byproduct of lipid peroxidation, in conditions where reactive nitrogen species interact with lipid hydroperoxides. This might contribute to a better understand of this complex event and physiological or physiopathological implications

Evidências apontam para o envolvimento da peroxidação lipídica em diversas patologias. Os hidroperóxidos de lipídios (LOOH) são os produtos primários da peroxidação lipídica e sua decomposição resulta em produtos de maior reatividade e toxicidade, como os radicais peroxila. Esses radicais desempenham papel importante na propagação da peroxidação lipídica e também podem gerar oxigênio molecular singlete (1O2) por meio da combinação de dois radicais peroxila. Neste trabalho investigamos a possibilidade dos LOOH, em particular dos hidroperóxidos de ácido linoléico (LAOOH), de servirem como fonte 1O2 na presença de oxidantes de relevância biológica como metais, peroxinitrito ou ácido hipocloroso. A formação de 1O2 foi claramente demonstrada na reação de LAOOH com esses oxidantes pelas detecções (i) da emissão bimolecular na região espectral do vermelho (&#955;>570 nm), (ii) da emissão monomolecular no infravermelho-próximo (&#955;=1270 nm), (iii) do espectro de emissão no infravermelho, e (iv) da intensificação e supressão da luminescência na presença de D2O e azida, respectivamente. Além disso, os mecanismos de reação foram estudados utilizando LAOOH marcados com oxigênio-18 (LA18O18OH) e captadores químicos específicos para 1O2 aliada à tecnica de detecção por HPLC acoplada à espectrometria de massa. Os resultados mostraram a formação de 1O2 marcado [18(1O2) ] na reação de LA18O18OH com os três oxidantes, revelando que os átomos de oxigênio do 1O2 são derivados do hidroperóxido. Em conjunto, as evidências obtidas levam à conclusão de que os LOOH podem servir como fontes potenciais de 1O2 em sistemas biológicos em situações onde haja a coexistência de LOOH e metais, peroxinitrito ou ácido hipocloroso. / Evidences point to the involvement of lipid peroxidation in several diseases. Lipid hydroperoxides (LOOH) are the primary products of lipid peroxidation and their decomposition generates more reactive and toxic compounds, such as peroxyl radicals. These radicals play an important role in the propagation of lipid peroxidation and may also generate singlet molecular oxygen (1O2) by the combination of two peroxyl radicals. In this study we have investigated the possibility of LOOH, in particular linoleic acid hydroperoxide (LAOOH), to be a source of 1O2 in the presence of biologically relevant oxidants such as, metal ions, peroxynitrite or hypochlorous acid. The formation of 1O2 was clearly demonstrated in the reaction of LAOOH with all the three tested oxidants by detecting: (i) the dimol light emission in the red spectral region (&#955;>570 nm), (ii) the monomol light emission in the near-infrared region (&#955;=1270 nm), (iii) the infrared light emission spectrum, and (iv) the enhancing effect of deuterium oxide and the quenching effect of azide on light emission. Furthermore, the mechanism was studied using LAOOH labeled with 18-oxygen isotope (LA18O18OH) and specific 1O2 chemical traps in combination with HPLC coupled to mass spectrometry detection. The results have showed the formation of 18-oxygen labeled 1O2 [18(1O2) ] in the reaction of LA18O18OH with the three oxidants, indicating that oxygen atoms in 1O2 are derived from the hydroperoxide. Altogether, the obtained evidences lead to the conclusion that LOOH may serve as a potential source of 1O2 in biological systems, in situations where LOOH can interact with metals, peroxynitrite or hypochlorous acid.

Les capteurs d’oxygène sont le plus grand apport dans la technologie des emballages actifs parce qu’ils permettent de retarder la dégradation oxydante des aliments et ainsi éviter la perte de saveurs et le développement microbien au sein des aliments. Bien que le développement des emballages actes existe depuis les années 70 dans des pays producteur agricole, la recherche sur ces emballages reste encore embryonnaire, en particulier sur les critères techniques portant sur l’absorption d’oxygène de films. Cette thèse constitue une contribution sur l’étude des cinétiques d’absorption d’oxygène de l’huile de lin comme capteur d’oxygène. L’oxydation de l’huile et d’esters insaturés (composé modèle de l’huile) est suivie sous différentes conditions d’exposition (températures comprises entre 40-110°C et pressions partielles d’oxygène entre 0 et 1 bar). Expérimentalement, on propose de caractériser l’absorption d’oxygène liée à l’oxydation de l’huile par thermogravimétrie (ATG), suivi de concentration d’oxygène et titrage de peroxide. Un modèle cinétique basé des schémas classiques avec décomposition des hydroperoxydes, est proposé pour simuler l’oxydation de l’huile de lin et des esters insaturés modèles. Ce modèle est ensuite extrapolé à des films de différentes épaisseurs de polypropylène (PP) contenant 1% d’huile de lin en considérant que cette dernière est bien dispersé dans la matrice PP et que la diffusion d’oxygène est pilotée par la matrice PP. / Oxygen scavengers (OS) are one of the most important technology of active packaging, because prevents oxidative degradation related with off-flavours, off-odours and microbial growth in food. Although active packaging has been proposed since 1970s, in developing countries with a large agricultural base, active packaging still remains unexplored both in terms of application and research, there is a lack of technical criteria on O2 scavenging films, labels, sheets, and trays. This PhD thesis is a contribution in the study of linseed oil as active ingredient for OS providing a kinetic characterization of its thermo-oxidation between 40°C and 110°C in atmospheres with different oxygen concentration. In the experimental approach, innovative application of TGA was proposed to study oxygen uptake capacity complemented by headspace and peroxide value measurements. The kinetic model, derived from a classic mechanistic scheme where initiation of thermo-oxidation results from decomposition of hydroperoxides, was capable to simulated linseed oil oxidation, and also oxygen absorptions of polypropylene films, of different thickness, containing 1% of linseed oil, with hypotheses of well dispersion of linseed oil in PP matrix, and oxygen diffusion governed by the PP matrix.

La biohydrogénation (BH) ruminale des acides gras polyinsaturés (AGPI) est à l’origine de la production d’AG trans pouvant se retrouver dans les productions de ruminants, dont le lait. Parmi ceux-ci, les isomères t11 auraient des effets bénéfiques pour la santé des consommateurs alors que les isomères t10 sont potentiellement défavorables. En élevage, l’apport de graines oléagineuses dans la ration des vaches permet d’augmenter la teneur du lait en ces acides gras. Or ces graines sont souvent distribuées chauffées pour améliorer leur valeur nutritionnelle. Expérimentalement, les effets des graines chauffées sur les teneurs en isomères t11 dans le rumen ou le lait sont variables, mais généralement elles permettent une augmentation des isomères t11 et une protection des AGPI. Au contraire, des huiles très oxydées par chauffage diminuent fortement les isomères t11 et augmentent parfois les isomères t10. Les produits d’oxydation des lipides générés pendant le chauffage des graines ou des huiles pourraient être incriminés. Les objectifs de la présente étude étaient d’explorer les éventuels effets des produits d’oxydation du c9,c12-C18:2 sur sa BH ruminale. In vitro, la protection des AGPI dans des graines de soja chauffées a été liée aux aldéhydes et en particulier à l’hexanal. L’augmentation des isomères t11 a été observée avec un aldéhyde long et insaturé, le t2,t4-décadiénal, suite à une inhibition de la dernière étape de la BH. Cet effet était concomitant à une modification marquée de la communauté bactérienne du rumen induite par cet aldéhyde. Les hydroperoxydes issus du c9,c12-C18:2 sont le 13HPOD et le 9HPOD. L’augmentation des isomères t10 a systématiquement été reliée au 13HPOD dans nos différentes expérimentations. Aucun mécanisme d’action n’a pu être formellement démontré mais l’effet du 13HPOD s’exercerait plutôt sur le microbiote, car il ne module pas l’activité de la Δ9-isomérase. Quant à la diminution des isomères t11 observée avec les huiles chauffées, elle n’a pas pu être expliquée. Elle pourrait également être liée, au moins partiellement, aux 13HPOD et 9HPOD, capables d’inhiber la Δ12-isomérase. Des modifications des fermentations ruminales, sans altération mesurable de l’abondance, de la diversité ou de la structure de la communauté bactérienne, suggèrent aussi un effet des AGPI chauffés sur l’activité des bactéries. / Ruminal biohydrogenation (BH) of polyunsaturated fatty acids (PUFA) produces some trans FA which can be found in ruminant products. Among them, t11 isomers would be beneficial for human health while t10 isomers are potentially deleterious. In farms, addition of oilseeds to the diet of dairy cows increases these fatty acids in milk. Oilseeds are often heated before incorporation to cow’s diets, to enhance their nutritional value. Experiments investigating effects on t11 isomers content in rumen and milk of cows receiving heated oilseeds provided variable results, but they usually increased t11 isomers and protected PUFA from BH. On the contrary, highly oxidized oil decrease t11 isomers and sometimes increase t10 isomers. Lipid oxidation products generated during heating of oilseeds and oils could be incriminated. The objectives of the present study were to investigate the effects of c9,c12-C18:2 oxidation products on its BH. Protection of PUFA in heated soybeans was linked to aldehydes, mainly hexanal. An increase of t11 isomers was observed with a long and unsaturated aldehyde, the t2,t4-decadienal, due to an inhibition of the last BH step. This effect was concomitant with a modification of bacterial community by t2,t4-decadienal. Hydroperoxides formed during c9,c12-C18:2 heating are 13HPOD and 9HPOD. The increase of t10 isomers in all of our experimentations was systematically linked with 13HPOD. No definitive explanation about the mechanism of action could be proposed, but 13HPOD would most probably act on microbiote since it had no effect on Δ9-isomerase. Our experiments did not explain the decrease of t11 isomers observed with heated oils, which could, at least in part, be due to 13HPOD and 9HPOD, which were able to inhibit Δ12-isomerase Some modifications of ruminal fermentation without measurable alteration of bacterial community abundance, diversity or structure also suggest an action of heated PUFA on bacterial activity.

The oxidation of polyunsaturated fatty acids to the corresponding hydroperoxide by plant and animal lipoxygenases is an important step for the generation of bioactive lipid mediators. Thereby fatty acid hydroperoxide represent a common intermediate, also in human innate immune cells, like neutrophil granulocytes. In these cells a further key component is the heme protein myeloperoxidase producing HOCl as a reactive oxidant. On the basis of different investigation a reaction of the fatty acid hydroperoxide and hypochlorous acid (HOCl) could be assumed. Here, chromatographic and spectrometric analysis revealed that the hydroperoxide moiety of 15S-hydroperoxy-5Z,8Z,11Z,13E-eicosatetraenoic acid (15-HpETE) and 13S-hydroperoxy-9Z,11E-octadecadienoic acid (13-HpODE) is not affected by HOCl. No reduction of the hydroperoxide group due to a reaction with HOCl could be measured. It could be demonstrated that the double bonds of the fatty acid hydroperoxides are the major target of HOCl, present either as reagent or formed by the myeloperoxidase-hydrogen peroxide-chloride system.