作者:Niel C. Hoglen、Stephen C. Waller、I. Glenn Sipes、Daniel C. Liebler
DOI:10.1021/tx960200h
日期:1997.4.1
detected in reactions involving peroxynitrite. Oxidation of gamma-TH by peroxynitrite involves nitration and electron transfer reactions. Since the product distribution in oxidations with NO2+BF4- differed substantially from that in oxidations with peroxynitrite and SIN-1, NO2+ appeared not to be the principal species involved in NGT formation. Nitration of gamma-TH may involve either peroxynitrite or some
过氧亚硝酸盐与γ-生育酚(gamma-TH)在甲醇/磷酸钾缓冲溶液中的反应导致形成四个主要产物,被鉴定为2,7,8-三甲基-2-(4,8,12) -(三甲基癸基)-5-硝基-6-苯并甲醇++(NGT),2,7,8-三甲基-2-(4,8,12-三甲基癸基)-5,6-苯并二氢萘醌(有环)和两个8a非对映异构体-(羟基)-γ-生育酚。NGT是在这些反应中形成的主要产物,并通过增加Fe(3 +)-EDTA的量适度增加了它的形成。当γ-TH暴露于3-吗啉代亚砜亚胺(SIN-1)时,也形成了Tocored和NGT,该化合物会分解形成过氧亚硝酸盐。当γ-TH与硝化剂NO2 + BF4-在乙腈或甲醇/磷酸钾缓冲液中反应时,还会生成NGT和tocored,但检测到的主要产物是γ-生育酚醌(γ-TQ)。在涉及过氧亚硝酸盐的反应中未检测到该产物。过亚硝酸盐氧化γ-TH涉及硝化和电子转移反应。由于用 + B
Novel tocopheryl compounds XXIV. Studies into the nitrosation chemistry of γ-tocopherol: preparation of 5-nitroso-γ-tocopherol via an organomercury derivative of vitamin E
exists in equilibrium with its ortho-quinone monoxime tautomer 6, the latter being the major component with >99%. NMR and analytical data of the tautomeric couple are reported for the first time. The chemistry of the nitrosation of γ-tocopherol was studied in detail. In the presence of oxygen, 5 is readily oxidized to 5-nitro-γ-tocopherol (7), whereas at elevated temperatures an additional process, the
The antioxidant activity of vitamin E (VE) homologs alpha, gamma and delta-tocotrienamines (4b-6b), never studied before, and alpha, gamma and delta-tocopheramines (4a-7a) was investigated by means of different total antioxidant capacity (TAC) tests. In all the test model systems, compounds 4a-7a and 4b-6b showed similar or higher TAC values than the parental vitamin E forms and their physiological metabolites. alpha-Homologs of VE amines showed markedly higher activity than the VE congeners in the TEAC test, which is tailored for liposoluble antioxidants, while gamma-homologs of the amine analogs showed higher activity in the FRAP tests. Kinetics analysis of the reaction with DPPH center dot showed higher second order rate k for 4a than for alpha-tocopherol (1a). alpha-Tocopherolquinone 1f was the common main oxidation product for both 1a and alpha-tocopheramine (4a) exposed to ferric ions or DPPH center dot, and the implied oxidative deamination of 4a was accompanied by a nitration reaction of phenolic substrates that were added to the reaction medium. Possible mechanisms of these reactions were studied. (C) 2011 Elsevier Ltd. All rights reserved.