ANTIOXIDANT ACTIVITY OF OXIDATION-PRODUCTS OF ALPHA-TOCOPHEROL AND OF ITS MODEL-COMPOUND 2,2,5,7,8-PENTAMETHYL-6-CHROMANOL

A variety of oxidation products (4-29) of alpha-tocopherol, 1 and of its model compound, 2,2,5,7,8-pentamethyl-6-chromanol (2) has been tested for antioxidant activity against autoxidizing safflower oil (ASO) and autoxidizing methyl linoleate (AML). The following compounds showed good antioxidant activity against both substrates: 5-hydroxymethyl-2,2,7,8-tetramethyl-6-chromanol (4), 5-(2,2,5,7,8-pentamethyl-6-chromanoxy)methyl-2,2,7, 8-tetramethyl-6-chromanol (15), 1,2-bis(2,2,7,8-tetramethyl-6-chromanol-5-)ethane (16), 5-ethoxymethyl-7,8-dimethyltocol (19), 5-methoxymethyl-2,2,7,8-tetramethyl-6-chromanol (21), 5-ethoxymethyl-2,2,7,8-tetramethyl-6-chromanol (20), 5-propoxymethyl-2,2,7,8-tetramethyl-6-chromanol (22), 5-butoxymethyl-2,2,7,8-tetramethyl-6-chromanol (23), 5-(2-methyl-1-propoxy)methyl-2,2,7,8-tetramethyl-6-chromanol (24), 5-(2-methyl-2-propoxy)methyl-2,2,7,8-tetramethyl-6-chromanol (25), 5-heptoxymethyl-2,2,7,8-tetramethyl-6-chromanol (26), 5-undecoxymethyl-2,2,7,8-tetramethyl-6-chromanol (27), 5-phytoxymethyl-2,2,7,8-tetramethyl-6-chromanol (28) and 5-cholesteroxymethyl-2,2,7,8-tetramethyl-6-chromanol (29). 2,2,7,8-Tetramethylchroman-5,6-dione (17) and 1,2-bis(2,2,7-trimethylchroman-5,6-dione-8-)ethane (18) showed significant antioxidant activity against ASO but not against AML. If the corresponding oxidation products of 1 are formed in vivo it means that the antioxidant activity of 1 is not lost on oxidation. This may help to explain the outstanding capacity of 1 to protect cell membranes.