The effects of phenolic components of tea on the production of pro- and anti-inflammatory cytokines by human leukocytes in vitro.

Epidemiological evidence suggests protective effects of dietary flavonoids against cardiovascular disease. Tea provides a major source of dietary flavonoids in many countries and its polyphenolic components have well-recognised antioxidant properties. However, scavenging of free radicals may not be the sole mechanism by which tea-derived polyphenols exert their protective effects. This study investigates the effects of four major tea-derived catechins and a black tea extract on the production of pro- and anti-inflammatory cytokines by human leukocytes in vitro. Epicatechin gallate, epigallocatechin and epigallocatechin gallate decreased the production of interleukin 1beta and enhanced the production of interleukin 10, but had no effect on the production of interleukin 6 or tumour necrosis factor-alpha. Although these effects suggest anti-inflammatory properties of the tea-derived catechins, they were observed at concentrations which were unlikely to be achievable in plasma in vivo and are therefore unlikely to contribute to the protective effects of tea-derived flavonoids in inflammatory diseases.