茶の成分に關する研究

(第3報)一新Amide “Theanine” に就て

抄録

The author discovered a new amide in the water extract of Japanese green tea, and named it “theanine”. This substance crystallizes in the form of colorless needle; molecular formula C₇H₁₄O₃N₂, melting point 217_??_218° (decompose), and [α]¹² _D=+7.1. It presents strong ninhydrin reaction. It is very soluble in water, and is dissolved in 2.6 times of water at 0° and 1.8 times of water at 100°, but insoluble in ethyl alcohol and ether. By hydrolysis of theanine, it gives L-glutamic acid and ethyl amine nearly quantitatively. From the fact that it shows no biuret reaction and that the natural glutamine is γ-amide, it seems very probable that theanine may be L-glutamic acid γ-ethyl amide. It is the first time that ethyl amine has been discovered, though not in a free state, in plant kingdom. The author has also studied the distribution of theanine in each stage of tea leaf developments. Gyokuro is rich (about 1%) in it, but Sencha is poor. It seems, therefore, that theanine assumes the analogous rôle of glutamine or asparagine in other plants though the destination of ethyl amine is yet unknown.