Simulated intestinal digestion of green and black teas

Previous studies have shown that significant changes to green tea catechins occur as a result of changes in pH similar to those found in the gastroint estinal tract. In this study we have: demonstrated that the sum of the anti oxidant activities attributable to the four major catechins in brewed green and black tea samples was less than the total measured antioxidant activit y. although there was a high degree of correlation between antioxidant acti vity and total measured polyphenol concentration. In addition. incubation o f either form of tea at acid pH (as found in the stomach) had little effect of the concentration of individual catechins. However, incubation at sligh tly alkaline pH, similar to that found in the small intestine, resulted in a rapid decline in the concentrations of both green and black tea catechins , but with a lesser reduction in antioxidant activity acid polyphenol conce ntration. (C) 2001 Elsevier Science Ltd. All rights reserved.