title: Green tea extract as food antioxidant. Synergism and antagonism with α-tocopherol in vegetable oils and their colloidal systems.
abstract: The antioxidant effects of α-tocopherol (TOH) in combination with green tea extract (GTE), the green tea polyphenol (-)-epicatechin (EC) or the isomeric (+)-catechin (C), were investigated using different lipid systems based on high linoleic sunflower oil: bulk oil, o/w-emulsion and a phosphatidylcholine-based liposome system. Both polyphenols as well as TOH were efficient antioxidants in all systems when used alone, as detected by the formation of free radicals and conjugated dienes and by oxygen consumption. Strong synergistic effect was found for the combination of TOH and GTE in a methyl linoleate o/w-emulsion and in the pure bulk oil, while only an additive effect was observed in a liposome system. The synergism was already evident for the tendency for radical formation in the bulk oil as detected by electron spin resonance (ESR) spectroscopy. On the contrary, combinations of TOH with either EC or C showed clear synergistic effects in both heterogeneous systems, but antagonistic or additive effects in bulk oil. GTE may accordingly be used to protect both vegetable oils and their emulsions against oxidation through enhancement of the activity of their endogenous antioxidants, while GTE is less efficient in the protection of phospholipids as in liposomes.
authors.affiliation: Food Chemistry, Department of Food Science, University of Copenhagen, Rolighedsvej 30, 1958 Frederiksberg C, Denmark.
authors.forename: Jie
authors.initials: J
authors.lastname: Yin
authors.forename: Eleonora Miquel
authors.initials: EM
authors.lastname: Becker
authors.forename: Mogens L
authors.initials: ML
authors.lastname: Andersen
authors.forename: Leif H
authors.initials: LH
authors.lastname: Skibsted
mesh_terms: D000975:Antioxidants / Q000737:chemistry*; D028241:Camellia sinensis / Q000737:chemistry*; D004655:Emulsions / Q000737:chemistry; D005503:Food Additives / Q000737:chemistry*; D010084:Oxidation-Reduction; D010936:Plant Extracts / Q000737:chemistry*; D010938:Plant Oils / Q000737:chemistry*; D000074242:Sunflower Oil; D013662:Tea / Q000737:chemistry; D024502:alpha-Tocopherol / Q000737:chemistry*
chemical_list: D000975:Antioxidants; D004655:Emulsions; D005503:Food Additives; D010936:Plant Extracts; D010938:Plant Oils; D000074242:Sunflower Oil; D013662:Tea; D024502:alpha-Tocopherol