Tocotrienamines and tocopheramines: Reactions with radicals and metal ions

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.