Wataha J: Green Tea Polyphenol Causes Differential Oxidative Environments in Tumor versus Normal Epithelial Cells

Green tea polyphenols (GTPPs) are considered beneficial to hu-man health, especially as chemopreventive agents. Recently, cy-totoxic reactive oxygen species (ROS) were identified in tumor and certain normal cell cultures incubated with high concentrations of the most abundant GTPP, ()-epigallocatechin-3-gallate (EGCG). If EGCG also provokes the production of ROS in normal epithelial cells, it may preclude the topical use of EGCG at higher doses. The current study examined the oxidative status of normal epithe-lial, normal salivary gland, and oral carcinoma cells treated with EGCG, using ROS measurement and catalase and superoxide dismutase activity assays. The results demonstrated that high concentrations of EGCG induced oxidative stress only in tumor cells. In contrast, EGCG reduced ROS in normal cells to back-ground levels. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazo