Influence of alkylamides of glutamic acid and related compounds on the central nervous system. I. Central depressant effect of theanine.

In 1949, Sakato2) isolated an amino acid, theanine (L-GluNHEt), from Japanese tea leaves and identified it as N-ethylglutamine amide. The presence of L-GluNHEt in other varieties of tea was confirmed by Cartwright, et al.3) And L-GluNHEt has been thought to be a flavourous constituent of tea leaves. On the other hand, caffeine, a central stimulant, has been known to be a pharmacological active constituent of tea. Hayashi,4) however, reported that the magnitude of stimulant effect produced by the water extract of tea is less marked than that seen following administration of caffeine in a dose comparable to its content in the extract of tea leaves. This report concerned with the studies on the pharmacological action of L-GluNHEt on the central nervous system comparing with other alkylamides of glutamic acid (Glu).