Oxidation of Polyunsaturated Fatty Acids and its Impact on Food Quality and Human Health

Ling Tao, PhD

Department of Animal Science Cornell University 149 Morrison Hall Ithaca, NY 14853, USA; E-mail: Lt364@cornell.edu

INTRODUCTION

Over the past few decades, chronic diseases including cardiovascular diseases, obesity, diabetes and cancer have increased rapidly in the USA and other countries of the world.¹ Diet and nutrition are important factors in the maintenance and promotion of good health throughout the entire life. By far, both preclinical and clinical studies have shown that ω-3 Polyunsaturated fatty acids (PUFAs) in particular Eicosapentaenoic acid (EPA) and Docosahexaenoic acid (DHA) exert heath beneficial effects on cardiovascular diseases, diabetes, cancer and so on.^2,3,4,5 This leads to institutions worldwide publishing recommendations on the intake of EPA and DHA. For instance, Food and Agriculture Organization (FAO) and World Health Organization (WHO) recommend adults to take 0.25-2 g EPA+DHA per day.⁶ American Heart Association (AHA) recommends daily intake of 0.5-1 g EPA+DHA per day per adult.⁷

However, as reviewed by Weylandt et al more recently, there are controversial results regarding to the health efficacy of ω-3 PUFAs.8 On one hand, the dose and experimental designs may contribute to the variation in results. On the other hand, with the nature of unsaturated bonds, PUFAs are prone to oxidation which generates various metabolites as well as reactive oxygen species. The extent of oxidation and the resulting metabolites may positively or negatively affect the efficacy of PUFAs. This review will introduce different types of PUFA oxidation and discuss the effects of oxidation on food quality and human health.

ENZYMATIC AND NON-ENZYMATIC OXIDATION OF PUFAs

With multiple unsaturated bonds, PUFA is susceptible to oxidation, which is categorized into non-enzymatic oxidation and enzymatic oxidation. Non-enzymatic oxidation can be further divided into autoxidation (mediated by free radicals) and photooxidation (mediated by ultraviolet or singlet oxygen). In cells, several types of enzymes including Cyclooxygenases (COXs), Lipoxygenases (LOXs) and Cytochromes P450 (CYPs) are able to oxidize PUFAs and generate various metabolites.9

Non-Enzymatic Oxidation

In autoxidation, the reaction is mediated by free radicals, giving rise to a lipid hydroperoxide as the primary oxidation product.¹⁰ In many cases, hydroperoxides can be further oxidized to ketones and ultimate malonaldehyde.¹¹ Hydroxy alkenals such as 4-Hydroxy-2-nonenal (HNE), generated by peroxidation of ω-6 PUFAs,^12,13,14 and 4-Hydroxy-2-hexenal (HHE), a product from peroxidation of ω-3 PUFAs15,16,17 are also widelystudied autoxidative products of PUFAs. Apart from autooxidation, PUFAs are susceptible to light-induced photooxidation: photochemical oxidation and photosensitized oxidation.¹⁸ The former one is initiated during exposure to ultraviolet irradiation. Photosensitized oxidation, instead, requires photosensitizers (i.e. chlorophyll, hemeprotein, riboflavin and synthetic dyes) and visible light.¹⁹ The reaction can be categorized into two types: Type I reaction involves the production of free radicals by interaction of the excited sensitizer with a substrate; Type II reaction involves generation of singlet oxygen which further reacts with PUFAs to produce hydroperoxides.^20,21 In this case, vegetable oils with chlorophyll-like pigments are likely to undergo photooxidation during storage.

Enzymatic Oxidation

In enzymatic oxidation, Phospholipases A2 (PLA2) is the major phospholipase that cleaves phospholipids at the sn-2 position resulting in free PUFAs and lysophospholipids.²² After freeing from membrane, PUFAs can be further catalyzed by COXs (COX1 or COX2) to form prostaglandin H2. It is unstable and can be converted into various prostanoids depending on the cellular prevalence of terminal prostanoid synthases.^23,24 In addition to COX, free fatty acids can be converted by LOXs to form hydroperoxides. LOXs belong to a family of dioxygenases which catalyze the insertion of molecular oxygen into PUFAs with at least one cis, cis-1,4-pentadiene in the structure.²⁵ Some of the LOX-catalyzed products have recently been discovered as potent lipid mediators. For example, enzymatic oxygenation of EPA yields new metabolites, named E-series Resolvins (RvEs), which were the first omega-3 lipid mediators reported to resolve inflammation via receptor-specific actions.^26,27,28 Likewise, DHA can form D-series Resolvins (RvDs),^29,30 Protectins/neuroprotectins (PDs/NPDs)^31,32,33 and Maresins (MaRs)^34,35,36 through enzymesmediated oxygenation. Those metabolites have been widely studied to dampen or resolve inflammation, protect from renal or brain dysfunctions, etc. COXs and LOXs can also convert ω-3 and ω-6 PUFAs into different series of prostaglandins, thromboxanes and leukotrienes.³⁷ CYPs are better known for their role in xenobiotic metabolism. However, they can also transform PUFAs to epoxy-, monohydoxylated-and dihydroxylated-metabolites. Recent work using recombinant human CYP enzymes has identified the predominant products from the expoxidation of EPA and DHA as 17,18-epoxyeicosatetraenoic acid and epoxy docosapentaenoic acid, respectively.³⁸

IMPACT OF PUFA OXIDATION ON FOOD QUALITY

Plant oils and fish are known as major sources of ω-3 PUFAs. Soybean oil, canola oil are commonly consumed oil and are rich in α-Linolenic acid or Alpha-linolenic acid ((ALA), 7.8-9.2%), while some fatty fish including salmon, sardine, and menhaden contain abundant EPA and DHA (17%-27% of total fatty acids). Other dietary sources of ω-3 PUFAs include nuts, seeds, egg yolk, etc. 39,40 With the recognition of the health beneficial effects of ω-3 PUFAs, there is a growing industry providing novel sources of ω-3 PUFAs such as fish oil capsules, algae products and food enriched with ω-3 PUFAs.⁴¹ Our lab recently used defatted green microalgal biomass to enrich ω-3 PUFAs in chicken meat⁴² and eggs (unpublished).

Susceptibility of lipid peroxidation in food depends on the lipid composition, the presence of prooxidants and antioxidants, oxygen levels, temperature, light and processing methods.⁴³ PUFA-rich foods are more susceptible for lipid oxidation. Likewise, presence of prooxidants such as redox active metals (Fe, Cu) and hemeproteins, exposure to high oxygen levels and high temperature may accelerate oxidation process. Lipid oxidation often brings problems in food processing and storage. First, it negatively affects food flavor due to the formation of aldehydes and ketones. Oxidation of PUFAs produces a complex mixture of volatile secondary oxidation products, and these cause particularly objectionable off-flavors.⁴⁴ For example, soybean oil can undergo “flavor reversion”, a type of light-induced oxidation.⁴⁵ It has been suggested that the oxidation of ALA in soybean oil is responsible for the formation of 2-pentylfuran and its isomer, which may result in flavor reversion.⁴⁶ Butter enriched with unsaturated fatty acids or conjugated linoleic acid may be susceptible to off-flavor by generation of oxidized products including 3-methyl-1H-indole (mothball-like), pentanal (fatty), heptanal (green) and butanoic acid (cheesy).⁴⁷ Second, lipid oxidation may reduce the nutritional value by causing the destruction of essential fatty acids and the lipid-soluble vitamins A, D, E, and K as well as the decrease in caloric content.⁴⁸ Third, free radicals and metabolites formed during oxidation may exert adverse effects on human health.⁴⁹ More details of impact on human will be discussed in the next section.

Given lipid oxidation-triggered negative effects, multiple methods have been applied to reduce or prevent lipid oxidation so as to improve the food quality. The most commonly used method is addition of antioxidants. Since the 1940’s, it is known that vitamin E is a major lipophilic chain-breaking antioxidant which protects tissue PUFAs against peroxidation⁵⁰ Serfert et al found a combination of tocopherols (rich in the δ-derivative and low in the α-derivative), ascorbyl palmitate and trace metal chelators (lecithin or citrem) efficiently stabilized the oil during microencapsulation. Addition of rosemary extract in the microencapsulated oil further retarded autoxidation during storage.⁵¹ Besides vitamin E, other vitamins or precursors like ascorbic acid and β-carotene were shown antioxidant activity in food system.^18,52 Plant bioactive compounds particularly polyphenols have been widely reported to have antioxidant effects. For example, apple skin extracts prepared from “Northern Spy” cultivar were found effective in reducing the lipid oxidation induced by heat, Ultraviolet (UV) light and peroxyl radicals.⁵³ Although it is plausible that natural polyphenols could prevent lipid oxidation, the approach of incorporating polyphenols into food and the effects of polyphenol additives on food flavor are not completely understood. In addition to the antioxidant supplementation, other methods are used to reduce lipid oxidation. Arruda et al reported that using nitrogen flushing to remove oxygen in the headspace of bottled soybean oil increased the sensory quality during storage. Shelf life can also be increased from 60 up to 180 days as the initial oxygen concentration is reduced from >15% to< 3%.⁵⁴ Larsen et al found that cups with a high light barrier (incorporation of a black pigment into the packaging material) can sufficiently protect the sour cream from getting rancid due to photooxidation.⁵⁵

IMPACT OF PUFA OXIDATION ON HUMAN HEALTH

In human body, PUFA is susceptible to oxidation under the exposure of free radicals and enzymes such as COXs, LOXs and CYPs. An increasing number of studies have been conducted to identify the oxidation pathway of PUFAs and related metabolites. However, the impact of PUFA oxidation on human health remains elusive.

HNE, a product from ω-6 oxidation of PUFAs, has been found in many diseases including atherosclerosis,^56,57 neurodegenerative diseases,^58,59 cancer^60,61 and so on. Indeed, Uchida et al have recently found that HNE markedly induced intracellular ROS production in cultured rat hepatocytes RL34 cells.⁶² This pro-oxidant effect of HNE was also observed in human neuroblastoma SH-SY5Y cells.⁶³ Awada et al reported that oxidized PUFAs (rich in HNE and HHE) induced oxidative stress and inflammation in mice and in human intestinal Caco-2/TC7 cells.⁶⁴ In human trials, Jenkinson et al also found that high PUFA diet (15% PUFA) significantly increased whole blood oxidized glutathione and urinary thiobarbituric acid reactive substances, indices of oxidative stress, in healthy male subjects.65 Interestingly, PUFA oxidation products have also been reported to activate antioxidant pathways which detoxify cytotoxic xenobiotics. For instance, HNE has been shown to enhance the gene and protein expression of class P Glutathione S-Transferase (GST-P) as well as the total GST activity in normal rat liver epithelial cells.⁶⁶ HNE can also activate antioxidant response element, leading to the induction of class A GST isozymes, such as GSTA1 and GSTA4, in rat clone 9 hepatoma cells.⁶⁷ In addition, HHE upregulated nuclear factor, erythroid 2-like 2, an important regulator of antioxidant responses in the heart of high fat-fed mice.⁶⁸ The bi-directional effects of HNE or HHE are concentration dependent. HNE at concentration lower than 10 μM tends to exert beneficial effects while higher concentrations may have toxic effects.⁶⁹ As supported by Zhang et al, treating cardiomyocytes with small, subtoxic doses (5 μM) of HNE offered protection from subsequent exposure to toxic doses (>=20 μM).⁷⁰

Over a decade, a growing number of PUFA metabolites have been discovered, including ω-3 PUFAs-derived resolvins, protectins, maresins, prostaglandin-3-, thromboxane-3- and leukotriene-5-series as well as ω-6 PUFA-derived prostaglandin-2-, thromboxane-2- and leukotriene-4-series.^37,71 ω-3 PUFA-derived metabolites have shown potent anti-inflammatory, tissue protective and resolution-stimulating functions. For instance, RvDs and PD1/NPD1 inhibit neutrophil infiltration into injured kidneys, block toll-like receptor-mediated inflammatory activation of macrophages and mitigate renal dysfunctions.⁷² Recently, Chiang et al demonstrated a previously unrecognized role of GPR18 as a receptor for RvD2 that stimulates efferocytosis and mediates the resolution of inflammation.⁷³ Another type of lipid mediator, MaR1 and MaR2 were identified to have potency at enhancing human macrophage phagocytosis and efferocytosis.^34,74 ω-3 PUFAs-derived prostaglandin-3- and leukotriene-5-series have been found to exert anti-arrhythmic and anti-inflammatory effects, respectively. By contrast, ω-6 PUFAs-derived prostaglandin-2-series have shown proarrhythmic effects and leukotriene-4-series from ω-6 PUFAs have presented pro-inflammatory effects.^37,75 This indicates that enzymatic oxidation products of ω-3 and ω-6 PUFA may exert opposing effects on human health.

From current studies, we learnt that more PUFAs do not necessarily yield better effects as they may undergo oxidation and produce metabolites that exert adverse effects at high levels. Co-supplementation with antioxidants such as vitamin C and vitamin E may reduce autoxidation of PUFAs and potentially enhance the efficacy. In addition, increasing ω-3 to ω-6 ratio in the diet is likely to produce more beneficial metabolites, thereby enhancing efficacies of PUFAs. The optimal dose of PUFAs, antioxidant supplementation as well as ω-3 to ω-6 ratio, however, require additional research evidences.

CONCLUSION

As summarized in Figure 1, through non-enzymatic and enzymatic oxidation, PUFAs are transformed to various metabolites. In most cases, oxidation of PUFAs results in offflavors and reduction of food quality and shelf life. The oxidation may induce oxidative stress and inflammation when the metabolites are at high concentrations. At low concentrations, the metabolites may exert antioxidant effects. The enzymatic oxidative products of ω-3 and ω-6 PUFAs may have opposing effects on inflammation and cardiac arrhythmicity. At present, the functions and working mechanisms of PUFA metabolites are not completely understood. Moreover, whether PUFA itself or oxidized PUFA metabolites play more important roles in various disease context remains unclear. Herein, future studies are needed to tackle these problems.

Figure 1: The oxidation of PUFAs and its impact on food quality and human health. With multiple unsaturated bonds, PUFAs can undergo both nonenzymatic and enzymatic oxidation and generate a variety of metabolites. Oxidation of PUFAs often brings adverse effects to food by producing off-flavors, reducing food quality and shelf life. The non-enzymatic oxidative products may induce oxidative stress and inflammation at high concentrations while exerting antioxidant effects at low concentrations. The enzymatic oxidative products of ω-3 and ω-6 PUFA may have opposing effects on inflammation and cardiac arrhythmicity.

COX: Cyclooxygenase; CYP: Cytochromes P450; DHA: Docosahexaenoic acid; EPA: Eicosapentaenoic acid; HHE: 4-Hydroxy-2-hexenal; HNE: 4-Hydroxy-2-nonenal; LOX: Lipoxygenase; MaR: Maresin; PD/NPD: Protectin/neuroprotectin; PUFA: Polyunsaturated fatty acid; Rv: Resolvin.

CONFLICTS OF INTEREST

The authors declare that they have no conflicts of interest.

ACKNOWLEDGMENT

The author would like to acknowledge Dr. Lei Liu, currently an Assistant Professor in College of Veterinary Medline, Hunan Agricultural University, China for the helpful comments and suggestions.

1. World Health Organization. The world health report: reducing risks, promoting healthy life. Geneva, Switherland, 2002.

2. Yessoufou A, Nekoua MP, Gbankoto A, Mashalla Y, Moutairou K. Beneficial effects of omega-3 polyunsaturated fatty acids in gestational diabetes: consequences in macrosomia and adulthood obesity. Exp Diabetes Res. 2015. 2015: 1-11. doi: 10.1155/2015/731434

3. Nabavi SF, Bilotto S, Russo GL, et al. Omega-3 polyunsaturated fatty acids and cancer: Lessons learned from clinical trials. Cancer Metastasis Rev. 2015; 34(3): 359-380. doi: 10.1007/s10555-015-9572-2

4. Khawaja OA, Gaziano JM, Djousse L. N-3 fatty acids for prevention of cardiovascular disease. Curr Atheroscler Rep. 2014;16(11): 1477S-1482S. doi: 10.1007/s11883-014-0450-0

5. van den Elsen L, Garssen J, Willemsen L. Long chain n-3 polyunsaturated fatty acids in the prevention of allergic and cardiovascular disease. Curr Pharm Design. 2012. 18(16): 2375-2392. doi: 10.2174/138161212800165960

6. FAO-WHO. Fats and fatty acids in human nutrition: report of an expert consultation, fao food and nutrition paper #91, FAO, WHO: Geneva, Switherland, 2010.

7. Harris WS, Mozaffarian D, Rimm E, et al. Omega-6 fatty acids and risk for cardiovascular disease a science advisory from the american heart association nutrition subcommittee of the council on nutrition, physical activity, and metabolism; council on cardiovascular nursing; and council on epidemiology and prevention. Circulation. 2009; 119(6): 902-907. doi: 10.1161/CIRCULATIONAHA.108.191627

8. Weylandt KH, Serini S, Chen YQ, et al. Omega-3 polyunsaturated fatty acids: the way forward in times of mixed evidence. Biomed Res Int. 2015; 2015: 1-24. doi: 10.1155/2015/143109

9. Gruber F, Ornelas CM, Karner S, et al. Nrf2 deficiency causes lipid oxidation, inflammation, and matrix-protease expression in dha-supplemented and Uva-irradiated skin fibroblasts. Free Radic Biol Med. 2015; 88(Pt B): 439-451. doi: 10.1016/j.freeradbiomed.2015.05.006

10. Thomas MJ. Analysis of lipid peroxidation products in health and disease. In: Spickett CM, Forman H J, eds. Lipid oxidation in health and disease. Boca Raton: CRC Press, 2015: 137.

11. Pryor WA, Stanley JP. Letter: A suggested mechanism for the production of malonaldehyde during the autoxidation of polyunsaturated fatty acids. Nonenzymatic production of prostaglandin endoperoxides during autoxidation. J Org Chem. 1975; 40(24):3615-3617.
doi: 10.1021/jo00912a038

12. Pryor WA, Porter NA. Suggested mechanisms for the production of 4-hydroxy-2-240 nonenal from the autoxidation of polyunsaturated fatty acids. Free Radic Biol Med. 1990. 8(6):541-543. doi: 10.1016/0891-5849(90)90153-a

13. Esterbauer H, Benedetti A, Lang J, Fulceri R, Fauler G, Comporti M. Studies on themechanism of formation of 4-hydroxynonenal during microsomal lipid peroxidation. Biochim Biophys Acta. 1986; 876(1): 154-166. doi: 10.1016/0005-2760(86)90329-2

14. Esterbauer H, Schaur RJ, Zollner H. Chemistry and biochemistry of 4-246 hydroxynonenal, malonaldehyde and related aldehydes. Free Radic Biol Med. 1991; 247 11(1): 81-128. doi: 10.1016/0891-5849(91)90192-6

15. Tanaka R, Shigeta K, Sugiura Y, Hatate H, Matsushita T. Accumulation of hydroxyl lipids and 4-hydroxy-2-hexenal in live fish infected with fish diseases. Lipids. 2014; 49(4): 385-396. doi: 10.1007/s11745-013-3875-2

16. Long EK, Picklo MJ, Sr. Trans-4-hydroxy-2-hexenal, a product of n-3 fatty acid peroxidation: Make some room hne. Free Radic Biol Med. 2010; 49(1): 1-8. doi: 10.1016/j.freeradbiomed.2010.03.015

17. Yamada S, Funada T, Shibata N, et al. Protein-bound 4-hydroxy-2-hexenal as a marker of oxidized n-3 polyunsaturated fatty acids. J Lipid Res. 2004; 45(4): 626-634. doi: 10.1194/jlr.M300376-JLR200

18. Matsushita S, Terao J. Singlet oxygen-initiated photooxidation of unsaturated fatty acid esters and inhibitory effects of tocopherols and beta-carotene. In: Simic MG, Karel M, eds. Autooxidation in food and biological systems. Springer US, 1980:27-44.

19. Frankel EN. Lipid oxidation. 2nd ed. Oily Press, 2005.

20. Foote CS. Photosensitized oxidation and singlet-oxygen: consequences in biological systems. In: Pryor WA, ed. Free radicals in biology.
New York: Academic Press, 1976: 85-133.

21. Stratton SP, Liebler DC. Determination of singlet oxygenspecific versus radical-263 mediated lipid peroxidation in photosensitized oxidation of lipid bilayers: effect of beta-264 carotene and alpha-tocopherol. Biochemistry. 1997; 36(42): 11-20. doi: 10.1021/bi9708646

22. Dennis EA, Cao J, Hsu YH, Magrioti V, Kokotos G. Phospholipase A2 enzymes: Physical structure, biological function, disease implication, chemical inhibition, and therapeutic intervention. Chem Rev. 2011; 111(10): 6130-6185. doi: 10.1021/cr200085w

23. Smith WL, Urade Y, Jakobsson PJ. Enzymes of the cyclooxygenase pathways of prostanoid biosynthesis. Chem Rev. 2011. 111(10): 5821-5865. doi: 10.1021/cr2002992

24. Smith WL, DeWitt DL, Garavito RM. Cyclooxygenases: structural, cellular, and molecular biology. Annu Rev Biochem.2000. 69: 145-182.
doi: 10.1146/annurev.biochem.69.1.145

25. Joo YC, Oh DK. Lipoxygenases: potential starting biocatalysts for the synthesis of signaling compounds. Biotechnol Adv.2012. 30(6): 1524-1532. doi: 10.1016/j.biotechadv.2012.04.004

26. Isobe Y, Arita M, Iwamoto R, et al. Stereochemical assignment and anti-inflammatory properties of the omega-3 lipid mediator resolvin E3. J Biochem. 2013; 153(4): 355-360. doi: 10.1093/jb/mvs151

27. Serhan CN, Clish CB, Brannon J, Colgan SP, Chiang N, Gronert K. Novel functional sets of lipid-derived mediators with antiinflammatory actions generated from omega-3 fatty acids via cyclooxygenase 2-nonsteroidal antiinflammatory drugs and transcellular processing. J Exp Med. 2000; 192(8): 1197-1204. doi: 10.1084/jem.192.8.1197

28. Arita M, Bianchini F, Aliberti J, et al. Stereochemical assignment, antiinflammatory properties, and receptor for the omega-3 lipid mediator resolvin E1. J Exp Med. 2005; 201(5): 713-722. doi: 10.1084/jem.20042031

29. Serhan CN, Hong S, Gronert K, et al. Resolvins: a family of bioactive products of omega-3 fatty acid transformation circuits initiated by aspirin treatment that counter proinflammation signals. J Exp Med. 2002. 196(8): 1025-1037. doi: 10.1084/jem.20020760

30. Ward PA. Resolvins on the way to resolution. J Exp Med. 2015; 212(8): 1142. doi: 10.1084/jem.2128insight4

31. Marcheselli VL, Hong S, Lukiw WJ, et al. Novel docosanoids inhibit brain ischemia- reperfusion-mediated leukocyte infiltration and pro-inflammatory gene expression. J Biol Chem. 2003; 278(44): 43807-43817. doi: 10.1074/jbc.M305841200

32. Mukherjee PK, Marcheselli VL, Serhan CN, Bazan NG. Neuroprotectin D1: A docosahexaenoic acid-derived docosatriene protects human retinal pigment epithelial cells from oxidative stress. Proc Natl Acad Sci USA. 2004; 101(22): 8491-8496. doi: 10.1073/pnas.0402531101

33. Serhan CN, Gotlinger K, Hong S, et al. Anti-inflammatory actions of neuroprotectin d1/protectin d1 and its natural stereoisomers: assignments of dihydroxy-containing docosatrienes. J Immunol. 2006. 176(3): 1848-1859. doi: 10.4049/jimmunol.176.3.1848

34. Serhan CN, Yang R, Martinod K, et al. Maresins: novel macrophage mediators with potent antiinflammatory and proresolving actions. J Exp Med. 2009; 206(1): 15-23. doi: 10.1084/jem.20081880

35. Serhan CN, Dalli J, Karamnov S, et al. Macrophage proresolving mediator maresin 1 stimulates tissue regeneration and controls pain. FASEB journal. 2012; 26(4): 1755-1765. doi: 10.1096/fj.11-201442

36. Dalli J, Zhu M, Vlasenko NA, et al. The novel 13s, 14s-epoxy-aresin is converted by human macrophages to maresin 1 (MaR1), inhibits leukotriene A4 hydrolase (LTA4H), and shifts macrophage phenotype. FASEB journal. 2013; 27(7): 2573-2583. doi: 10.1096/fj.13-227728

37. Schmitz G, Ecker J. The opposing effects of n-3 and n-6 fatty acids. Prog Lipid Res. 2008; 47(2): 147-155. doi: 10.1016/j.plipres.2007.12.004

38. Fer M, Dreano Y, Lucas D, et al. Metabolism of eicosapentaenoic and docosahexaenoic acids by recombinant human cytochromes p450. Arch Biochem Biophys. 2008; 471(2): 116-125. doi: 10.1016/j.abb.2008.01.002

39. Racine RA, Deckelbaum RJ. Sources of the very-long-chain unsaturated omega-3 fatty acids: eicosapentaenoic acid and docosahexaenoic acid. Curr Opin Clin Nutr Metab Care. 2007; 10(2): 123-128. doi: 10.1097/MCO.0b013e3280129652

40. Kris-Etherton PM, Taylor DS, Yu-Poth S, et al. Polyunsaturated fatty acids in the food chain in the United States. Am J Clin Nutr. 2000; 71(1): 179s-88s. doi: 10.1093/ajcn/71.1.179s

41. Whelan J, Rust C. Innovative dietary sources of n-3 fatty acids. Annu Rev Nutr. 2006; 26: 75-103. doi: 10.1146/annurev. nutr.25.050304.092605

42. Gatrell SK, Kim J, Derksen TJ, O’Neil EV, Lei XG. Creating omega-3 fatty-acid-enriched chicken using defatted green microalgal biomass. J Agr Food Chem. 2015; 63(42): 9315-322. doi: 10.1021/acs.jafc.5b03137

43. Kolakowska A, Bartosz G. Oxidation of food components: an introduction. In: Bartosz G, ed. Food oxidants and antioxidants: chemical, biological and functional properties. Taylor & Francis Group, LLC, 2014: 9-10.

44. Let MB, Jacobsen C, Meyer AS. Sensory stability and oxidation of fish oil enriched milk is affected by milk storage temperature and oil quality. Int Dairy J. 2005; 15(2): 173-182. doi: 10.1016/j.idairyj.2004.06.003

45. Kao JW, Hammond EG, White PJ. Volatile compounds produced during deodorization of soybean oil and their flavor significance. J Am Oil Chem Soc. 1998; 75(9): 1103-1107. doi: 10.1007/s11746-998-0297-z

46. Min DB, Callison AL, Lee HO. Singlet oxygen oxidation for 2-pentylfuran and 2-329 pentenyfuran formation in soybean oil. J Food Sci. 2003; 68(4): 1175-1178. doi 10.1111/j.1365-2621.2003.tb09620.x

47. Mallia S, Escher F, Dubois S, Schieberle P, SchlichtherleCerny H. Characterizationand quantification of odor-active compounds in unsaturated fatty acid/conjugated linoleic acid (UFA/CLA)-enriched butter and in conventional butter during storage and induced oxidation. J Agr Food Chem. 2009; 57(16):7464-7672. doi: 10.1021/jf9002158

48. Arab-Tehrany E, Jacquot M, Gaiani C, Imran M, Desobry S, Linder M. Beneficial effects and oxidative stability of omega-3 long-chain polyunsaturated fatty acids. Trends Food Sci Tech. 2012; 25(1): 24-33. doi: 10.1016/j.tifs.2011.12.002

49. Jacobsen C, Hartvigsen K, Lund P, et al. Oxidation in fishoil-enriched mayonnaise 1. Assessment of propyl gallate as an antioxidant by discriminant partial least squares regression analysis. Eur Food Res Technol. 1999; 210(1): 13-30. doi: 10.1007/s002170050526

50. Buettner GR. The pecking order of free radicals and antioxidants: Lipid peroxidation, alpha-tocopherol, and ascorbate. Arch Biochem Biophys. 1993; 300(2): 535-543. doi: 10.1006/abbi.1993.1074

51. Serfert Y, Drusch S, Schwarz K. Chemical stabilisation of oils rich in long-chain polyunsaturated fatty acids during homogenisation, microencapsulation and storage. Food Chem. 2009; 113(4): 1106-1112. doi: 10.1016/j.foodchem.2008.08.079

52. Nielsen JH, Ostdal H, Andersen HJ. The influence of ascorbic acid and uric acid on the oxidative stability of raw and pasteurized milk. In: Morello MJ, Shahidi F, Ho CT, eds. Free radicals in food: Chemistry, nutrition and health effects. Washington, DC: ACS Symposium Series, American Chemical Society, 2002: 126-137. doi: 10.1021/bk-2002-0807.ch009

53. Rupasinghe HPV, Erkan N, Yasmin A. Antioxidant protection of eicosapentaenoic acid and fish oil oxidation by polyphenolic-enriched apple skin extract. J Agr Food Chem. 2010; 58(2): 1233-1239. doi: 10.1021/jf903162k

54. Arruda CS, Garcez WS, Barrera-Arellano D, Block JM. Industrial trial to evaluate the effect of oxygen concentration on overall quality of refined, bleached, and deodorized soybean oil in pet bottles. J Am Oil Chem Soc. 2006; 83(9): 797-802. doi: 10.1007/s11746-006-5017-y

55. Larsen H, Tellefsen SBG, Dahl AV. Quality of sour cream packaged in cups with different light barrier properties measured by fluorescence spectroscopy and sensory analysis. J Food Sci. 2009; 74(8): S345-S350. doi: 10.1111/j.1750-3841.2009.01303.x

56. Rosenfeld ME, Palinski W, Yla-Herttuala S, Butler S, Witztum JL. Distribution of oxidation specific lipid-protein adducts and apolipoprotein b in atherosclerotic lesions of varying severity from WHHL rabbits. Arteriosclerosis. 1990; 10(3): 336-349. doi: 10.1161/01.ATV.10.3.336

57. Palinski W, Yla-Herttuala S, Rosenfeld ME, et al. Antisera and monoclonal antibodies specific for epitopes generated during oxidative modification of low density lipoprotein. Arteriosclerosis. 1990. 10(3): 325-335. doi: 10.1161/01.ATV.10.3.325

58. Yoritaka A, Hattori N, Uchida K, Tanaka M, Stadtman ER, Mizuno Y. Immunohistochemical detection of 4-hydroxynonenal protein adducts in parkinson disease. Proc Natl Acad Sci USA. 1996; 93(7): 2696-2701. doi: 10.1073/pnas.93.7.2696

59. Shibata N, Nagai R, Uchida K, et al. Morphological evidence for lipid peroxidation and protein glycoxidation in spinal cords from sporadic amyotrophic lateral sclerosis patients. Brain Res. 2001; 917(1): 97-104. doi: 10.1016/S0006-8993(01)02926-2

60. Okamoto K, Toyokuni S, Uchida K, et al. Formation of 8-hydroxy-2’-deoxyguanosine and 4-hydroxy-2-nonenal-modified proteins in human renal-cell carcinoma. Int J Cancer. 1994; 58(6): 825-859. doi: 10.1002/ijc.2910580613

61. Zhong H, Yin H. Role of lipid peroxidation derived 4-ydroxynonenal (4-HNE) in cancer: Focusing on mitochondria. Redox Biol. 2015; 4: 193-199. doi: 10.1016/j.redox.2014.12.011

62. Uchida K, Shiraishi M, Naito Y, Torii Y, Nakamura Y, Osawa T. Activation of stress signaling pathways by the end product of lipid peroxidation. 4-hydroxy-2-nonenal is a potential inducer of intracellular peroxide production. J Biol Chem. 1999; 274(4):
2234-2242. doi: 10.1074/jbc.274.4.2234

63. Kondo M, Oya-Ito T, Kumagai T, Osawa T, Uchida K. Cyclopentenone prostaglandins as potential inducers of intracellular oxidative stress. J Biol Chem. 2001; 276(15): 12076-12083. doi: 10.1074/jbc.M009630200

64. Awada M, Soulage CO, Meynier A, et al. Dietary oxidized n-3 PUFA induce oxidative stress and inflammation: role of intestinal absorption of 4-HHE and reactivity in intestinal cells. J Lipid Res. 2012. 53(10): 2069-2080. doi: 10.1194/jlr.M026179

65. Jenkinson A, Franklin MF, Wahle K, Duthie GG. Dietary intakes of polyunsaturated fatty acids and indices of oxidative stress in human volunteers. Eur J Clin Nutr. 1999; 53(7): 523-528. doi: 10.1038/sj.ejcn.1600783

66. Fukuda A, Nakamura Y, Ohigashi H, Osawa T, Uchida K. Cellular response to the redox active lipid peroxidation products: induction of glutathione s-transferase p by 4-hydroxy2-nonenal. Biochem Biophys Res Commun. 1997; 236(2): 505-509. doi: 10.1006/bbrc.1997.6585

67. Tjalkens RB, Luckey SW, Kroll DJ, Petersen DR. Alpha, beta-unsaturated aldehydes mediate inducible expression of glutathione s-transferase in hepatoma cells through 393 activation of the antioxidant response element (ARE). Adv Exp Med Biol. 1999; 463: 123-131.

68. Anderson EJ, Thayne K, Harris M, Carraway K, Shaikh SR. Aldehyde stress and up-regulation of Nrf2-mediated antioxidant systems accompany functional adaptations in cardiac mitochondria from mice fed n-3 polyunsaturated fatty acids. Biochem J.2012; 441(1): 359-366.
doi: 10.1042/BJ20110626

69. Anderson EJ, Taylor DA. Stressing the heart of the matter: re-thinking the mechanisms underlying therapeutic effects of n-3 polyunsaturated fatty acids. F1000 medicine reports. 2012; 4: 13. doi: 10.3410/M4-13

70. Zhang Y, Sano M, Shinmura K, et al. 4-hydroxy-2-nonenal protects against cardiac ischemia-reperfusion injury via the Nrf2-dependent pathway. J Mol Cell Cardiol. 2010; 49(4): 576-586. doi: 10.1016/j.yjmcc.2010.05.011

71. Isobe Y, Arita M. Identification of novel omega-3 fatty acidderived bioactive metabolites based on a targeted lipidomics approach. J Clin Biochem Nutr. 2014; 55(2): 79-84. doi: 10.3164/jcbn.14-18

72. Hong S, Lu Y. Omega-3 fatty acid-derived resolvins and protectins in inflammation resolution and leukocyte functions: targeting novel lipid mediator pathways in mitigation of acute kidney injury. Front Immunol. 2013; 4: 13. doi: 10.3389/fimmu.2013.00013

73. Chiang N, Dalli J, Colas RA, Serhan CN. Identification of resolvin D2 receptor mediating resolution of infections and organ protection. J Exp Med. 2015; 212(8): 1203-1217. doi: 10.1084/jem.20150225

74. Deng B, Wang CW, Arnardottir HH, et al. Maresin biosynthesis and identification of maresin 2, a new anti-inflammatory and pro-resolving mediator from human macrophages. PLoS One. 2014; 9(7): e102362. doi: 10.1371/journal.pone.0102362

75. Bagga D, Wang L, Farias-Eisner R, Glaspy JA, Reddy ST. Differential effects of prostaglandin derived from omega-6 and omega-3 polyunsaturated fatty acids on COX-2 expression and IL-6 secretion. Proc Natl Acad Sci USA. 2003; 100(4): 1751-1756.
doi: 10.1073/pnas.0334211100