title: Antioxidant activity of alkyl hydroxytyrosyl ethers in unsaturated lipids.
abstract: The antioxidant activity of ethyl and octyl hydroxytyrosyl ethers toward lipids was determined using the Rancimat and open cup methods at high temperatures and 50 °C, respectively. The effect of the unsaturation of the matrix was evaluated using sunflower, soya, and fish refined oils. The antioxidant activities of alkyl hydroxytyrosyl ethers (HTy ethers), hydroxytyrosyl esters, and free hydroxytyrosol are similar, and are much higher than that of α-tocopherol at the same millimolar concentration. The relationship between the induction period and the concentration of the HTy ethers is a sigmoidal curve; an accurate concentration of HTy ethers is necessary to achieve maximum activity, as it increases with the level of matrix unsaturation. The presence of tocopherols in commercial oils affects the antioxidant effect of HTy ethers. Thus, the addition of a low concentration of HTy ethers results in a positive effect, whereas the effect of the addition of high amounts of ethers is slightly less than that of the phenol alone. The addition of HTy ethers to commercial refined oils increases the stability of the oils and preserves tocopherols and polyunsaturated fatty acids from oxidation, enabling the oils to maintain their nutritional properties for longer periods of time.
authors.affiliation: Instituto de la Grasa, CSIC, Campus Universidad Pablo de Olavide, E41013 Seville, Spain.
authors.forename: Rosa
authors.initials: R
authors.lastname: Cert
authors.forename: Andrés
authors.initials: A
authors.lastname: Madrona
authors.forename: José Luis
authors.initials: JL
authors.lastname: Espartero
authors.forename: M Carmen
authors.initials: MC
authors.lastname: Pérez-Camino
mesh_terms: D000478:Alkylation; D000975:Antioxidants / Q000737:chemistry*; D004042:Dietary Fats, Unsaturated / Q000032:analysis*; D004987:Ethers / Q000737:chemistry; D005224:Fats, Unsaturated / Q000032:analysis / Q000737:chemistry*; D005395:Fish Oils / Q000737:chemistry; D005520:Food Preservatives / Q000737:chemistry*; D063427:Food Quality; D061353:Food Storage; D006358:Hot Temperature / Q000009:adverse effects; D007700:Kinetics; D008054:Lipid Peroxides / Q000032:analysis; D010084:Oxidation-Reduction; D010626:Phenylethyl Alcohol / Q000031:analogs & derivatives* / Q000737:chemistry; D010938:Plant Oils / Q000737:chemistry; D013024:Soybean Oil / Q000737:chemistry; D000074242:Sunflower Oil; D024505:Tocopherols / Q000032:analysis / Q000737:chemistry
chemical_list: D000975:Antioxidants; D004042:Dietary Fats, Unsaturated; D004987:Ethers; D005224:Fats, Unsaturated; D005395:Fish Oils; D005520:Food Preservatives; D008054:Lipid Peroxides; D010938:Plant Oils; D000074242:Sunflower Oil; C000605802:ethyl hydroxytyrosyl ether; C000605803:octyl hydroxytyrosyl ether; C005975:3,4-dihydroxyphenylethanol; D013024:Soybean Oil; D010626:Phenylethyl Alcohol; D024505:Tocopherols