title: Physiological levels of tea catechins increase cellular lipid antioxidant activity of vitamin C and vitamin E in human intestinal caco-2 cells.
abstract: Oxidative stress has been linked to the development of various chronic diseases. Vegetables and fruits, which contain polyphenols, were shown to have protective effects. (-)-Epigallocatechin-3-gallate (EGCG), a polyphenol abundant in tea, has been shown to have antioxidant activities in cell-free conditions and this study focused on the effect of cellular EGCG. Using an intestinal cell model to examine the oxidative stress induced by hydroxyl radicals, we report here that physiological concentrations (0.1-1 microM) of EGCG have dose- and incubation duration-dependent cell-associated lipid antioxidant activity (measuring malondialdehyde production). Vitamin E and vitamin C at 10-40 microM also showed cell-associated lipid antioxidant activities under shorter incubation durations. When EGCG was included in the incubation with vitamin E or C, more antioxidant activities were consistently observed than when vitamins were added alone. Catechin (widely present in fruits and vegetables) at 1 microM also significantly increased the antioxidant activity of vitamins E and C. Previous studies examining cell-associated activity of EGCG mainly focused on the 10-100 microM concentration range. Our results suggest that although the physiological level (0.1-1 microM) of dietary catechins is much lower than that of vitamins, they further contribute to the total antioxidant capacity even in the presence of vitamins.
authors.affiliation: Department of Exercise and Nutrition Sciences, University at Buffalo, 15 Farber Hall, Buffalo, NY 14214, USA.
authors.forename: Janjira
authors.initials: J
authors.lastname: Intra
authors.forename: Shiu-Ming
authors.initials: SM
authors.lastname: Kuo
mesh_terms: D000975:Antioxidants / Q000378:metabolism*; D001205:Ascorbic Acid / Q000378:metabolism*; D018938:Caco-2 Cells; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000187:drug effects*; D050356:Lipid Metabolism; D008315:Malondialdehyde / Q000378:metabolism; D013662:Tea / Q000737:chemistry*; D014810:Vitamin E / Q000378:metabolism*
chemical_list: D000975:Antioxidants; D013662:Tea; D014810:Vitamin E; D008315:Malondialdehyde; D002392:Catechin; C045651:epigallocatechin gallate; D001205:Ascorbic Acid