title: F4-isoprostanes: a novel class of prostanoids formed during peroxidation of docosahexaenoic acid (DHA).
abstract: Isoprostanes are prostaglandin (PG)-like compounds derived from free radical-catalyzed peroxidation of polyunsaturated fatty acids. F2-isoprostanes are produced in vivo by a non-cyclooxygenase mechanism involving free radical peroxidation of arachidonic acid. Peroxidation of eicosapentaenoic acid produces F3-isoprostanes. In this study, we explore the possibility of formation of F4-isoprostanes during peroxidation of docosahexaenoic acid (DHA) in vitro. DHA-liposomes were exposed at 37 degrees C to either 2,2'-azobis-(2-amidinopropane) hydrochloride (AAPH) or copper ions at final concentrations of 10 mM and 50 microM, respectively. Sample processing involved solid-phase extraction on a C18 and an NH2- cartridge. After conversion to pentafluorobenzyl ester and trimethylsilyl derivatives, F4-isoprostanes were analysed by negative ion-chemical ionisation mass spectrometry using tetradeuterated PGF2 alpha (PGF2-d4) as the internal standard. Quantitative analysis was carried out by selected ion monitoring (SIM) of the carboxylated anion [M-180]- at m/z 593 and 573 for the F4-isoprostanes and PGF2-d4, respectively. DHA oxidised by AAPH or by copper ions gave rise to a similar family of F4-isoprostanes. Formation of F4-isoprostanes increased throughout the oxidation period and was correlated with other indices of lipid peroxidation (hydroperoxides and thiobarbituric acid reactive substances). The possibility of analyzing F4-isoprostanes should provide new opportunities for studying the role of lipid peroxidation in nutritional studies and in the pathogenesis of neurodegenerative diseases.
authors.affiliation: Centre for Clinical Pharmacology and Therapeutic Toxicology, Department of Medicine, London, England. rmhajnz@ucl.ac.uk
authors.forename: J
authors.initials: J
authors.lastname: Nourooz-Zadeh
authors.forename: E H
authors.initials: EH
authors.lastname: Liu
authors.forename: E
authors.initials: E
authors.lastname: Anggård
authors.forename: B
authors.initials: B
authors.lastname: Halliwell
mesh_terms: D000578:Amidines / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D003300:Copper / Q000378:metabolism; D004281:Docosahexaenoic Acids / Q000378:metabolism*; D015227:Lipid Peroxidation / Q000502:physiology*; D008081:Liposomes / Q000378:metabolism; D013058:Mass Spectrometry; D015394:Molecular Structure; D016877:Oxidants / Q000378:metabolism; D011453:Prostaglandins / Q000032:analysis / Q000737:chemistry*; D017392:Thiobarbituric Acid Reactive Substances / Q000032:analysis; D013997:Time Factors
chemical_list: D000578:Amidines; D008081:Liposomes; D016877:Oxidants; D011453:Prostaglandins; D017392:Thiobarbituric Acid Reactive Substances; D004281:Docosahexaenoic Acids; C046728:2,2'-azobis(2-amidinopropane); D003300:Copper