Chapter 83 - Differences in the Tissue Distribution of Green Tea Compared to Black Tea Polyphenols

Abstract

The polyphenols in green tea (GT) and black tea (BT) are very different due to the different post-harvest processing of the tea leaves, which result in polymerization of GT polyphenols as a result of auto-oxidation. Eighty percent of tea is consumed as BT, while the majority of the literature on the health benefits of tea concerns GT. GT contains higher concentrations of monomeric polyphenols such as epigallocatechin gallate (EGCG), while BT contains polymeric polyphenols such as theaflavins and thearubigins. We have studied the distribution of GT and BT polyphenols in urine and prostate tissue in humans after consumption of brewed GT or BT prior to prostatectomy. Overall, higher concentrations of polyphenols are found in the circulation after GT consumption. While EGCG, 4″-O-MeEGCG and ECG are present in prostate tissue following GT consumption, BT polymers are not found in either blood or prostate tissue. In contrast to human prostate tissue, mouse and rat tissues have detectable levels of both gallated and non-gallated GTPs, suggesting differences in their tissue metabolism of GTPs compared to humans. In both humans and mice, the majority of gallated GTPs are found in the free form, whereas 100% of non-gallated GTPs are conjugated and excreted in the urine. In humans and mice, about 50% of GTPs occur in the methylated form. Future research is needed to investigate how to increase the bioavailability of GTPs.