Abstract
L-theanine (γ-glutamylethylamide) is a unique amino acid present almost exclusively in the tea plant (Camellia sinensis). It appears to only occur in three other species; one mushroom species and two other species of the Camellia genus. Since tea is the second most consumed beverage in the world, a considerable amount of theanine is consumed daily throughout the world and is said to greatly contribute to the taste of green tea. Tea contains a number of constituents, including polyphenols, proteins, amino acids, organic acids, vitamins, minerals, and pigments. Theanine comprises 1-2 percent of the dry weight of tea leaves, makes up approximately 50 percent of the amino acids in tea, and is present as the free amino acid only – it does not occur in proteins. Theanine is synthesized in the root of the plant and concentrates in the leaves, where sunlight converts theanine to polyphenols. Because of this, some tea cultivators grow their plants out of direct sunlight to preserve the theanine content and thus the flavor.1