title: alpha-tocopherol oxidation in beef and in bovine muscle microsomes.
abstract: The oxidation of alpha-tocopherol (TH) in beef was analyzed using a stable isotope dilution capillary gas chromatography-mass spectrometry assay. TH decreased while alpha-tocopherolquinone (TQ) and 2,3-epoxy-alpha-tocopherolquinone (TQE(2)) increased in ground longissimus lumborum (LL) and psoas major (PM) muscles during storage (P < 0.10). In LL steaks, the relative concentrations of TH decreased and TQ and TQE(2) increased in surface samples; changes were less dramatic in deep samples. Deuterated alpha-tocopherolhydroquinone (THQ) standard was not recovered and endogenous THQ was not detected in meat; THQ was measurable in microsomes isolated from PM and incubated in the presence of 2, 2'-azobis(2-amidopropane)HCl (ABAP) or myoglobin. ABAP-challenged microsomes yielded a tocopherol product profile which favored 5, 6-epoxy-alpha-tocopherolquinone (TQE(1)) and TQE(2), while the use of myoglobin as prooxidant resulted in a higher proportion of TQ and THQ. Results demonstrated that concentrations of TH decreased and TQ and TQE(2) increased in meat during storage and are consistent with the peroxy-radical scavenging function of tocopherol.
authors.affiliation: Animal Science Department, University of Connecticut, Storrs, Connecticut 06269, USA. cfaustma@ansc1.cag.uconn.edu
authors.forename: C
authors.initials: C
authors.lastname: Faustman
authors.forename: D C
authors.initials: DC
authors.lastname: Liebler
authors.forename: J A
authors.initials: JA
authors.lastname: Burr
mesh_terms: D000818:Animals; D002417:Cattle; D003903:Deuterium; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods; D008460:Meat / Q000032:analysis*; D008861:Microsomes / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism*; D010084:Oxidation-Reduction; D014810:Vitamin E / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism
chemical_list: D014810:Vitamin E; D003903:Deuterium