L-theanine, also named N-ethyl-glutamine, with CAS number of 3081-61-6 and formula of C7H14N2O3, is an amide compound in white or off-white powder with melting point of 214-215℃, is easily dissolved in water, and has an incense of burned sugar and a taste of monosodium glutamate.

L-theanine in nature only exists in tea plants accounting of 1%～2% of dry tea in free state, and is the main amino acid in tea accounting of some 50% of free amino acids. L-theanine is essential to human body, which can not synthesize and shall be supplied externally.

Since ancient time, it has been thought that drinking tea may relax tension of human being, but theanine in tea really plays the role and endows tea with the flavor and outstanding relaxation effect. In modern time, human being endures various spiritual tensions, and tea may enable human being to relax.