title: Iron-catalyzed reaction products of alpha-tocopherol with 1-palmitoyl-2-linoleoyl-3-sn-phosphatidylcholine (13S)-hydroperoxide.
abstract: Alpha-tocopherol was reacted with 1-palmitoyl-2-[(9Z,11E)-(S)-13-hydroperoxy-9,11-octadecadienoyl]-3-sn-phosphatidylcholine (13-PLPC-OOH) in the presence of a lipid-soluble iron chelate, Fe(III) acetylacetonate, in methanol at 37 degrees C. The reaction product was isolated and identified as a mixture of 1-palmitoyl-2-[(10E)-(12S,13S)-9-(8a-dioxy-alpha-tocopherone)-12,13-epoxy-10-octadecenoyl]-3-sn-phosphatidylcholine and 1-palmitoyl-2-[(9Z)-(12S,13S)-11-(8a-dioxy-alpha-tocopherone)-12,13-epoxy-9-octadecenoyl]-3-sn-phosphatidylcholine (TOO-epoxyPLPC), in which the 12,13-epoxyperoxyl radicals derived from 13-PLPC-OOH attacked the 8a-position of the alpha-tocopheroxyl radical. The iron and ascorbate-catalyzed reaction of 13-PLPC-OOH with alpha-tocopherol in phosphatidylcholine (PC) liposomes was assessed by measuring the reaction products of alpha-tocopherol. When 13-PLPC-OOH and alpha-tocopherol were added in saturated dimyristoyl-PC liposomes, the products were TOO-epoxyPLPC, alpha-tocopherylquinone, and epoxy-alpha-tocopherylquinones. In 1-palmitoyl-2-linoleoyl-PC (PLPC) liposomes, alpha-tocopherol could react with both the 13-PLPC-OOH derived 12,13-epoxyperoxyl radicals and the PLPC-derived peroxyl radicals and formed the addition products together with alpha-tocopherylquinone and epoxy-alpha-tocopherylquinones. Therefore, the iron-catalyzed decomposition of phospholipid hydroperoxides primarily produces epoxyperoxyl radicals, which react with the 8a-carbon centered radical of alpha-tocopherol in liposomal systems.
authors.affiliation: Department of Bioprocessing, Faculty of Agriculture, Gifu University, 1-1 Yanagido, Gifu City, Gifu 501-1193, Japan. yamautir@cc.gifu-u.ac.jp
authors.forename: Ryo
authors.initials: R
authors.lastname: Yamauchi
authors.forename: Keiko
authors.initials: K
authors.lastname: Ozaki
authors.forename: Makoto
authors.initials: M
authors.lastname: Shimoyamada
authors.forename: Koji
authors.initials: K
authors.lastname: Kato
mesh_terms: D002384:Catalysis; D002518:Ceramides / Q000138:chemical synthesis* / Q000737:chemistry*; D005609:Free Radicals / Q000737:chemistry; D006885:Hydroxybutyrates / Q000378:metabolism; D066298:In Vitro Techniques; D007501:Iron / Q000378:metabolism; D007502:Iron Chelating Agents / Q000378:metabolism; D015227:Lipid Peroxidation; D008081:Liposomes; D009682:Magnetic Resonance Spectroscopy; D010422:Pentanones / Q000378:metabolism; D010713:Phosphatidylcholines / Q000737:chemistry / Q000378:metabolism; D024502:alpha-Tocopherol / Q000737:chemistry* / Q000378:metabolism*
chemical_list: C460279:2-N-(10-pyrenedecanoyl)-1,3,17-trihydroxy-17-(3,5-dinitrobenzoyl)-4-heptadecene; D002518:Ceramides; D005609:Free Radicals; D006885:Hydroxybutyrates; D007502:Iron Chelating Agents; D008081:Liposomes; D010422:Pentanones; D010713:Phosphatidylcholines; C049529:acetyl acetonate; C055402:1-palmitoyl-2-linoleoylphosphatidylcholine; D007501:Iron; D024502:alpha-Tocopherol