title: The effect of fatty acid unsaturation on the antioxidant activity of beta-carotene and alpha-tocopherol in hexane solutions.
abstract: The effect of fatty acid unsaturation on the antioxidant ability of beta-carotene and alpha-tocopherol to inhibit azobis-isobutyronitrile AIBN)-induced malondialdehyde (MDA) formation is investigated in a hexane solution. A positive correlation is shown between the fatty acid unsaturation and MDA production in homogeneous solutions. Both beta-carotene and alpha-tocopherol act as chain-breaking antioxidants in our model, effectively suppressing AIBN-induced MDA formation. When alpha-tocopherol is added to fatty acid solutions, a lag phase of about 30 min is observed and a propagation phase is produced at a rate dependent on the degree of unsaturation and similar to that observed in the absence of the antioxidant. A specific inhibition of initiation phase by alpha-tocopherol is confirmed by its total consumption after 30 min of incubation with AIBN. On the other hand, when beta-carotene is added, a lag period is not observed and the inhibition of propagation phase progressively increases in relation to the degree of fatty acid unsaturation. These data present different antioxidant roles for beta-carotene and alpha-tocopherol in AIBN-induced lipid peroxidation and suggest that beta-carotene can be a very effective antioxidant in highly unsaturated membranes, such as those enriched with n-3 polyunsaturated fatty acids (PUFA).
authors.affiliation: Institute of General Pathology, Catholic University, Rome, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Palozza
authors.forename: C
authors.initials: C
authors.lastname: Luberto
authors.forename: G M
authors.initials: GM
authors.lastname: Bartoli
mesh_terms: D000704:Analysis of Variance; D000975:Antioxidants; D002338:Carotenoids; D005231:Fatty Acids, Unsaturated / Q000737:chemistry*; D005609:Free Radicals; D006586:Hexanes; D007700:Kinetics; D008315:Malondialdehyde / Q000032:analysis*; D009570:Nitriles; D014810:Vitamin E; D019207:beta Carotene
chemical_list: D000975:Antioxidants; D005231:Fatty Acids, Unsaturated; D005609:Free Radicals; D006586:Hexanes; D009570:Nitriles; D019207:beta Carotene; D014810:Vitamin E; D002338:Carotenoids; D008315:Malondialdehyde; C004526:azobis(isobutyronitrile)