Chemistry of theanine

Theanine is a unique free amino acid found only in tea leaves. It is one of the important chemical components that contribute to the taste of green tea infusion.

Green flavor has four characteristic taste elements: bitterness, astringence, sweetness and umami (a brothy or savory tatse). The brothy, sweet, umami taste is due to amino acids, especially theanine. Theanine has two enantiomers: L- and D-theanine. The average level of D-theanine was around 1.85% of the total theanine.

Theanine is the analogue of glutamine. Theanine is found in every part of the tea except for the fruit and contributes the major part of amino acids in tea.

Structure of theanine

It was detected by Japanese researchers as an unknown compound but the major one in the amino acid fraction of tea and was named theanine. Later, it was isolated and finally identified to be N-ethylglutamic acid.
Chemistry of theanine