Effect of defined green tea extract in various dosage schemes on drug-metabolizing enzymes in mice in vivo

Green tea represents a favourite beverage and green tea extracts are popular components of dietary supplements. The aim of present in vivo study was to report on the effect of defined green tea extract (Polyphenon) in various dosage schemes on drug-metabolizing enzymes in mice. The specific activities and expressions of a panel of drug-metabolizing enzymes (totally 16) were tested in liver and small intestine. Nine enzymes were significantly altered by Polyphenon treatment. The intestinal enzymes were more affected than the hepatic ones. The effects were mostly dose-dependent but short-term treatment had more pronounced impact than the long-term administration. Based on the results, normal consumption of green tea seems to be safe but extremely high doses of green tea extracts in dietary supplements could influence drugs metabolism and efficacy.