title: Identification of a novel selenium-containing compound, selenoneine, as the predominant chemical form of organic selenium in the blood of bluefin tuna.
abstract: A novel selenium-containing compound having a selenium atom in the imidazole ring, 2-selenyl-N(alpha),N(alpha),N(alpha)-trimethyl-L-histidine, 3-(2-hydroseleno-1H-imidazol-5-yl)-2-(trimethylammonio)propanoate, was identified from the blood and other tissues of the bluefin tuna, Thunnus orientalis. The selenium-containing compound was purified from the tuna blood in several chromatographic steps. High resolution mass spectrometry and nuclear magnetic resonance spectroscopy showed that the exact mass of the [M+H](+) ion of the compound was 533.0562 and the molecular formula was C(18)H(29)N(6)O(4)Se(2). Its gross structure was assigned as the oxidized dimeric form of an ergothioneine selenium analog in which the sulfur of ergothioneine is replaced by selenium. Therefore, we named this novel selenium-containing compound "selenoneine." By speciation analysis of organic selenium compounds using liquid chromatography inductively coupled plasma mass spectrometry, selenoneine was found widely distributed in various tissues of the tuna, with the highest concentration in blood; mackerel blood contained similar levels. Selenoneine was measurable at 2-4 orders of magnitude lower concentration in a limited set of tissues from squid, tilapia, pig, and chicken. Quantitatively, selenoneine is the predominant form of organic selenium in tuna tissues.
authors.affiliation: National Research Institute of Fisheries Science, Fukuura, Yokohama 236-8648, Japan.
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Yamashita
authors.forename: Michiaki
authors.initials: M
authors.lastname: Yamashita
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000737:chemistry; D019281:Dimerization; D005396:Fish Products; D016166:Free Radical Scavengers / Q000737:chemistry; D006639:Histidine / Q000031:analogs & derivatives* / Q000097:blood; D006801:Humans; D013058:Mass Spectrometry / Q000379:methods; D008956:Models, Chemical; D009930:Organic Chemicals; D016566:Organoselenium Compounds / Q000097:blood*; D010100:Oxygen / Q000737:chemistry; D012643:Selenium / Q000097:blood*; D018036:Selenium Compounds / Q000097:blood*; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D014413:Tuna / Q000097:blood*; D014867:Water / Q000737:chemistry
chemical_list: D000975:Antioxidants; D016166:Free Radical Scavengers; D009930:Organic Chemicals; D016566:Organoselenium Compounds; D018036:Selenium Compounds; C550322:selenoneine; D014867:Water; D006639:Histidine; D012643:Selenium; D010100:Oxygen
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