The presence of the oxidized and reduced forms of ubiquinones Q(9) and Q(10) was determined in commercial extra virgin olive and seed oils, where the amounts of alpha- and gamma-tocopherols and beta-carotene were also quantitated. Very high concentrations of ubiquinones were found in soybean and corn oils. Furthermore, the total antioxidant capability of each oil was evaluated by measuring total radical-trapping antioxidant parameters (TRAP) in tert-butyl alcohol and using egg lecithin as the oxidizable substrate. These values decreased in the order sunflower > corn > peanut > olive; the highest TRAP, which was found in sunflower oil, was related to the very high amount of alpha-tocopherol. Olive oil, because of the low content of alpha-tocopherol, exhibited a TRAP value approximately one-third that of sunflower oil. TRAP values of corn and soybean oils, in which low amounts of alpha-tocopherol but very high contents of gamma-tocopherol and reduced ubiquinones were present, were intermediate. gamma-Tocopherol exhibited a poor ability of trapping peroxyl radicals in tert-butyl alcohol. This behavior was probably due to the effects of the solvent on the rate of hydrogen abstraction from this phenol.

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A correlation between dietary lipids and cellular enzyme activities is a problem that has only been partially addressed by nutritionists. Therefore, changes in the fatty acid composition and the activities of some key metabolic enzymes (ubiquinol-2-cytochrome c reductase (EC 1.10.2.2), cytochrome oxidase (EC 1.9.3.1) and ATPase (EC 3.6.1.3)) in the mitochondria of liver, heart and brain of rats fed on diets differing extensively in their polyunsaturated fatty acid compositions have been investigated. The results showed that fatty acid compositional changes brought about by the dietary differences were associated with extensive changes in the activities of these key enzymes in the mitochondria. The extent of the influence differed considerably with the period over which the diets were fed. The role of dietary lipids to effect changes through the preservation of membrane structural integrity is discussed.Fat intake: Mitochondria1 fatty acids: Metabolic enzymes

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