Pharmacology and therapeutic uses of theanine

Extract

Except for water, tea is the most widely consumed beverage worldwide, primarily because of its perceived relaxant effects.^1,–3 Recently, interest has peaked in one component of green tea, theanine, which was isolated and identified in 1949 by a Japanese scientist.^1,4 Its purported uses are varied and often considered theoretical, with most data derived from in vitro or animal studies. This article reviews the data available on the pharmacology and therapeutic uses of theanine.

Theanine, or l-theanine, has many different names, including γ–glutamylethylamide, γ-ethylamino-l-glutamic acid,^1,5,6 and its commercial name, Suntheanine (Taiyo Kagaku Co. Ltd., Japan).¹ It is a water-soluble, nonproteinous amino acid predominantly found most in Camellia sinensis, the source of green tea.^6,7 Theanine is primarily responsible for the sweet taste of green tea.^4,6 It is also found in other Camellia species (Camellia japonica and Camellia sasanqua) and in the mushroom Xerocomus badius.^1,4,C. sinensis, an evergreen that can stand over 9 m high and bears dark green, serrated leaves and white, fragrant flowers, is native to eastern Asia and a member of the family Theaceae.¹ Theanine is the major amino acid found in green tea, comprising 50% of the plant’s total free amino acids and 1–2% of the dry weight of the leaves.^1,3,–6 Many people believe that tea leaves harvested from different times of the year contain different amounts of catechins (an anti-oxidant) and theanine (a relaxant), the chemical components of which are considered neuroprotective.^7,8 Theanine is converted by the plant into catechins.⁷