Methylated polyphenols are poor "chemical" antioxidants but can still effectively protect cells from hydrogen peroxide-induced cytotoxicity.
Several polyphenolic compounds, including flavonoids and phenolic acids, were compared with their per-methylated forms in both chemical and cell-based assays for antioxidant capacity. Methylation largely eliminated "chemical" antioxidant capacity, according to ferric reducing antioxidant power and oxygen radical absorbance capacity assays. Methylation, however, only moderately reduced protection of human Jurkat cells in culture, from hydrogen peroxide-mediated cytotoxicity, at physiologically relevant concentrations. Neither methylated nor un-methylated compounds were detectably metabolized by the cells. It appears that the protective mechanism of polyphenolic antioxidants against high concentrations of hydrogen peroxide in human cells may be largely unrelated to chemical antioxidant capacity.
Deng
Dawei
D
HortResearch, The Horticulture and Food Research Institute of New Zealand, Private Bag 92-169, Mt Albert, Auckland, New Zealand.
Zhang
Jingli
J
Cooney
Janine M
JM
Skinner
Margot A
MA
Adaim
Aselle
A
Jensen
Dwayne J
DJ
Stevenson
David E
DE
D000975:Antioxidants / Q000494:pharmacology*; D019610:Cytoprotection; D004305:Dose-Response Relationship, Drug; D005419:Flavonoids / Q000494:pharmacology*; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology / Q000633:toxicity*; D062385:Hydroxybenzoates / Q000494:pharmacology; D019169:Jurkat Cells; D008745:Methylation; D016877:Oxidants / Q000494:pharmacology / Q000633:toxicity*; D010636:Phenols / Q000494:pharmacology*; D059808:Polyphenols; D017382:Reactive Oxygen Species / Q000037:antagonists & inhibitors / Q000378:metabolism
D000975:Antioxidants; D005419:Flavonoids; D062385:Hydroxybenzoates; D016877:Oxidants; D010636:Phenols; D059808:Polyphenols; D017382:Reactive Oxygen Species; D006861:Hydrogen Peroxide; C017616:phenolic acid