46C-20

Epidemiological studies have reported an association between tea consumption and decreased risks of developing certain types of cancer, coronary heart disease, and the incidence of stroke. However, results have not been reproduced consistently. These beneficial health effects have been attributed to the presence of polyphenols, such as catechins, in black and green tea. Our objective was to determine the polyphenol content of different brands of black and green tea and its relationship to their antioxidant capacity measured by the oxygen radical absorbance capacity (ORAC) assay. Eleven different brands of black tea and eight brands of green teas were purchased from local supermarkets. Individual tea bags were brewed in 100 ml of boiling water for 3 minutes. The ORAC value for the brewed tea samples was determined using a modification of the method described by Cao and Prior (1999). HPLC analysis was used to measure the catechin, gallic acid and theaflavin content in the tea samples. The polyphenol content varied from 9.8 mg to 216.7 mg/100 ml brewed tea in decaf black and green tea, respectively. The polyphenol content was significantly lower in decaf vs. regular tea. ORAC values varied from 506 mmol TE/g  decaf black tea to 1686 mmol TE/g  green tea. The ORAC value was significantly associated with the polyphenol content (r=0.79). These results suggest a strong correlation between polyphenol content of tea samples and their antioxidant capacity as measured by the modified ORAC assay. The significant variation in polyphenol content among various brands of tea might explain the inconsistency in epidemiological studies mentioned above.