L-theanine is a unique free amino acid in tea, theanine is glutamic acid γ-ethylamide, sweet. Theanine content due to the variety of tea, parts and changes. Theanine accounts for 1% -2% by weight of the dry tea.
Theanine is chemically similar to glutamic acid and glutamic acid in the brain and is the main component of tea in the body fluid sweet. Theanine content of about 1 to 2% of new tea, its content decreased with the fermentation process.

    Tea tree amino acids refer to all 26 kinds of amino acids contained in tea, 20 of which are protein related amino acids, called protein amino acids; and 6 kinds of amino acids, which are not related to protein synthesis, are called non protein amino acids. Tea is more important in these six kinds, the most important of which is theanine, so theanine is one of the amino acids, also known as the characteristic amino acids of tea. As a characteristic non protein amino acid with the highest content in tea, theanine is safe, non-toxic and side-effect. It has many biological activities, such as anti-oxidation, immune regulation, anti-aging, antagonizing the cell excitatory toxicity caused by glutamate excess. At the same time, L-theanine, as an alkylamine, can activate γ - t immune cells to promote cell proliferation and cytokine secretion, enhance the ability to resist tumor cells, reduce the infection of external microorganisms, and reduce the chance of the body suffering from cold and influenza.