Abstract 975: Can drinking tea prevent cancer
Authors: Jason K. Loong, Evita Giraldez, Jon Whitaker, Richard A. Robison, Kim L. O'Neill
Journal: Cancer Research (2010)

Abstract Tea is the second most consumed drink worldwide. In China, where tea was discovered, the population maintains the highest average life expectancy in the world, and credits tea for much of their enjoyed health benefits. It is suggested that the high concentration of (-)-epigallocatechin-3-gallate (EGCG), a powerful antioxidant and major polyphenol in tea, accounts for the ability of tea to combat reactive oxygen species (ROS). It is believed that the antioxidant capacity of tea yields significant health benefits including chemoprevention qualities. This study investigated the antioxidant capacity of four popular types of tea in China. The antioxidant uptake of the four teas in cells was investigated. In addition, oxidative stress was induced in cell models and the antioxidant capacity obtained from treatment with each tea was measured. These measurements were observed and recorded along a time interval to determine if indications of cellular demand for antioxidants exist in relation to time and source. The teas were analyzed for antioxidant capacity using the Oxygen Radical Absorbance Capacity (ORAC) assay, in which fluorescence of a sample is measured when combined with Fluorescein, and calculates the decay in fluorescence after addition of an oxidizer, AAPH ((2,2’)-Azobis (2-amidinopropane) dihydrochloride). ORAC values for antioxidants are reported in Trolox equivalents per liter (TE/L) and are obtained from a Trolox standard curve. The antioxidant capacity of the teas were compared to a Trolox standard curve. The following mean values of antioxidant levels (in TE/L) were obtained from Green, Black, Oolong, and Pu-Erh tea: 57.1; 52.5; 43.1; and 26.4 respectively. Cellular models of Raji lymphoblasts, a Burkitt's lymphoma cell line, were used to investigate the cellular uptake of antioxidants from each tea when exposed for 24 hours. After exposure to the teas, cell lysates were measured for antioxidant levels and compared to untreated control cells. The results confirmed the intake of antioxidants on a cellular level. Results for Green, Black, Oolong, and Pu-Erh tea (in TE/L) are as follows: 125.3; 141.5; 131.1; and 143.1 compared to control levels. Another cell model involving Raji cells was used to explore any relationship between oxidative stress and antioxidant uptake. Cells were pre-treated with an oxidant and then exposed to each tea. The antioxidant capacity was again assessed. This allowed us to investigate the effect of oxidative stress on cellular uptake of antioxidants. Our data supports the hypothesis that oxidative stress precedes an increased amount of antioxidant uptake in cancer cells. Results after one hour following exposure to oxidative stress for Green, Black, Oolong, and Pu-Erh tea (in TE/L) were: 141.3; 124.9; 107.3; and 124.0 when compared to untreated control groups. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 975.