Evaluation of plasma antioxidant activity in rats given excess EGCg with reference to endogenous antioxidants concentrations and assay methods.
The contribution of (-)-epigallocatechin gallate (EGCg) intake to in vivo antioxidant activity is unclear, even with respect to plasma. In this study, we examined how administration of EGCg contributes to plasma antioxidant activity, relative to its concentration, endogenous antioxidants, and assay methods, namely oxygen radical absorbance capacity (ORAC) and ferric reducing/antioxidant power (FRAP). Administration of EGCg (500 mg/kg) to rats increased plasma EGCg (4μmol/L as free form) and ascorbic acid (1.7-fold), as well as ORAC (1.2-fold) and FRAP (3-fold) values. The increase in plasma ascorbic acid following EGCg administration was accompanied by its relocation from the adrenal glands and lymphocytes into plasma, and was related to the increase in FRAP. Plasma deproteinization and assays in plasma model solutions revealed that protein levels significantly contributed to ORAC values, where <3 μmol/L EGCg in the presence of protein exhibited minimal antioxidant activity, as measured by both FRAP and ORAC. As the concentration of plasma ascorbic acid was not influenced by deproteinization, differences in FRAP values with and without deproteinization were estimated to determine the contribution of enhanced ascorbic acid attributable to EGCg administration. These results will help to understand the points that should be considered when evaluating EGCg antioxidant activity in plasma.
a Faculty of Human Life and Environmental Sciences , Showa Women's University , Tokyo , Japan.
Kaori
K
Yokotani
b Information Center, National Institute of Health and Nutrition, National Institutes of Biomedical Innovation, Health and Nutrition , Tokyo , Japan.
Keizo
K
Umegaki
D000818:Animals; D000975:Antioxidants / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology*; D001205:Ascorbic Acid / Q000097:blood* / Q000494:pharmacology; D001774:Blood Chemical Analysis; D002392:Catechin / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D008214:Lymphocytes / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D010084:Oxidation-Reduction; D010949:Plasma / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
D000975:Antioxidants; D002392:Catechin; C045651:epigallocatechin gallate; D001205:Ascorbic Acid
Epigallocatechin gallate; antioxidant activity; ascorbic acid; plasma