The antioxidant effects of a-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/wemulsion
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.
The antioxidant effects of a-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/wemulsion
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.
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