Gerhard Liebisch, Eoin Fahy, Junken Aoki, Edward A. Dennis, Thierry Durand, Christer S. Ejsing, Maria Fedorova, Ivo Feussner, William J. Griffiths, Harald Köfeler, Alfred H. Merrill Jr., Robert C. Murphy, Valerie B. O’Donnell, Olga Oskolkova, Shankar Subramaniam, Michael J. O. Wakelam, Friedrich Spener

Consumption of food containing n-3 PUFAs, namely EPA and DHA, are known to benefit health and protect against chronic diseases. Both are richly found in marine-based food such as fatty fish and seafood that are commonly cooked prior to consumption. However, the elevated temperature during cooking potentially degrades the EPA and DHA through oxidation. To understand the changes during different cooking methods, lipid profiles of raw, boiled, pan-fried and baked salmon were determined by LC-MS/MS. Our results showed that pan-frying and baking elevated the concentration of peroxides in salmon, whereas only pan-frying increased the MDA concentration, indicating it to be the most severe procedure to cause oxidation among the cooking methods. Pan-frying augmented oxidized products of n-3 and n-6 PUFAs, while only those of n-3 PUFA were elevated in baked salmon. Notably, pan-frying and baking increased bioactive oxidized n-3 PUFA products, in particular F-_4t-neuroprostanes derived from DHA. The results of this study provided a new insight into the application of heat and its effect on PUFAs and the release of its oxidized products in salmon.

Several oxylipins are potent lipid mediators that regulate diverse aspects of health and disease and whose quantitative analysis by liquid chromatography–mass spectrometry (LC-MS) presents substantial technical challenges. As members of the lipidomics community, we developed technical recommendations to ensure best practices when quantifying oxylipins by LC-MS.

Polyunsaturated fatty acids (PUFAs) are essential components in eukaryotic cell membrane. They take part in the regulation of cell signalling pathways and act as precursors in inflammatory metabolism. Beside these, PUFAs auto-oxidize through free radical initiated mechanism and release key products that have various physiological functions. These products surfaced in the early nineties and were classified as prostaglandin isomers or isoprostanes, neuroprostanes and phytoprostanes. Although these molecules are considered robust biomarkers of oxidative damage in diseases, they also contain biological activities in humans. Conceptual progress in the last 3 years has added more understanding about the importance of these molecules in different fields. In this chapter, a brief overview of the past 30 years and the recent scope of these molecules, including their biological activities, biosynthetic pathways and analytical approaches are discussed.

The ecological success of diatoms requires a remarkable ability to survive many types of stress, including variations in temperature, light, salinity, and nutrient availability. On exposure to these stresses, diatoms exhibit common responses, including growth arrest, impairment of photosynthesis, production of reactive oxygen species, and accumulation of triacylglycerol (TAG). We studied the production of cyclopentane oxylipins derived from fatty acids in the diatom Phaeodactylum tricornutum in response to oxidative stress. Phaeodactylum lacks the enzymatic pathway for producing cyclopentane-oxylipins, such as jasmonate, prostaglandins or thromboxanes. In cells subjected to increasing doses of hydrogen peroxide (H2O2), we detected non-enzymatic production of isoprostanoids, including six PhytoPs, three F2t-IsoPs, two F3t-IsoPs and three F4t-NeuroPs, by radical peroxidation of alpha-linolenic, arachidonic, eicosapentaenoic and docosahexanoic acids, respectively. H2O2 also triggered photosynthesis impairment and TAG accumulation. F1t-PhytoPs constitute the major class detected (300 pmol per million cells; intracellular concentration, ~4 µM). Only two glycerolipids, phosphatidylcholine and diacylglycerylhydroxymethyl-trimethyl-alanine, could provide all substrates for these isoprostanoids. Treatment of Phaeodactylum with nine synthetic isoprostanoids produced an effect in the micromolar range, marked by accumulation of TAG and reduced growth, without affecting photosynthesis. Emission of H2O2 and free radicals upon exposure to stresses can therefore lead to glycerolipid peroxidation and non-enzymatic synthesis of isoprostanoids, inhibiting growth and contributing to the induction of TAG accumulation via unknown processes. This characterization of non-enzymatic oxylipins in Phaeodactylum opens a field of research on the study of processes controlled by isoprostanoid signaling in various physiological and environmental contexts in diatoms.