Liver Injury‐preventive Effect of Tea Theanine in Rats

This study was conducted to isolate the constituent, which had a preventive effect on D‐galactosamine‐induced rat liver injury, from the 70% ethanol‐soluble fraction of Japanese green tea. Theanine (glutamic acid γ‐ethylamide) was identified as the active compound, and the liver injury‐preventive effect of theanine was dose‐dependent. L‐Glutamic acid γ‐ethyl ester, but not glutamine, also brought about a significantly preventive effect on liver injury when added to the diet at equimolar levels to that of 1% theanine. The results indicate that theanine is one of the effective constituents of Japanese green tea in preventing D‐galactosamine‐induced liver injury.