(-)-Epigallocatechin-3-gallate prevents oxidative damage in both the aqueous and lipid compartments of human plasma.
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.
Aldini
Giancarlo
G
Istituto Chimico Farmaceutico Tossicologico, University of Milan, Milan, Italy.
Yeum
Kyung-Jin
KJ
Carini
Marina
M
Krinsky
Norman I
NI
Russell
Robert M
RM
D000975:Antioxidants / Q000494:pharmacology*; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D002451:Cell Compartmentation; D004305:Dose-Response Relationship, Drug; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D066298:In Vitro Techniques; D010084:Oxidation-Reduction / Q000187:drug effects; D010636:Phenols / Q000378:metabolism; D010949:Plasma / Q000187:drug effects* / Q000378:metabolism; D024502:alpha-Tocopherol / Q000378:metabolism
D000975:Antioxidants; D010636:Phenols; C042329:phenoxy radical; D002392:Catechin; C045651:epigallocatechin gallate; D024502:alpha-Tocopherol