(-)-Epigallocatechin-3-gallate prevents oxidative damage in both the aqueous and lipid compartments of human plasma |
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Authors: | Aldini Giancarlo Yeum Kyung-Jin Carini Marina Krinsky Norman I Russell Robert M |
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Affiliation: | Istituto Chimico Farmaceutico Tossicologico, University of Milan, Milan, Italy. |
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Abstract: | When human plasma was exposed to the hydrophilic radical initiator, AAPH, (-)-epigallocatechin-(3)-gallate (EGCG) dose-dependently inhibited the aqueous compartment oxidation (IC(50)=0.72 microM) (monitored by DCFH oxidation) and spared the lipophilic antioxidants, alpha-tocopherol, and carotenoids, but not ascorbic acid. When radicals were selectively induced in the lipid compartment by the lipophilic radical initiator, MeO-AMVN, EGCG spared alpha-tocopherol, but not carotenoids and inhibited the lipid compartment oxidation (monitored by BODIPY 581/591) with a potency lower than that found in the aqueous compartment (IC(50)=4.37 microM). Our results indicate that EGCG, mainly localized in the aqueous compartment, effectively quenches aqueous radical species, thus limiting their diffusion into the lipid compartment and preventing lipid-soluble antioxidant depletion. Further, ESR experiments confirmed that EGCG recycled alpha-tocopherol through a H-transfer mechanism at the aqueous/lipid interface affording an additional protective mechanism to the lipid compartment of plasma. |
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Keywords: | (−)-Epigallocatechin-(3)-gallate Antioxidant Carotenoids α-Tocopherol Aqueous and lipid plasma compartments |
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