Theanine (amino acid)

Theanine (amino acid)

This is an amino acid in green tea. "The IDA [idarubicin (IDA)-induced antitumor activity and toxicity] concentration in the tumors in the theanine plus IDA group increased to twice the level in the IDA alone group. Furthermore, the decrease in tumor weight caused by IDA at 1.0 mg/kg per day x4 days (at this dose IDA exhibits antitumor activity) was significantly amplified by theanine. The numbers of leukocyte and bone marrow cells decreased significantly on IDA injection. Theanine significantly reversed these changes."
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L-Theanine

Introduction

L-theanine (Y-glutamylcthylamide) is a
unique amino acid present almost exclusively
in the tea plant {Camellia siiicnsis). It appears to
only occur in three other speeies: one mushroom

speeies and two other speeies of the Camellia genus. Sinee tea is the seeond 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. Theanitie comprises 1-2 percent of the dry weight of tea leaves, makes up
approximately .'^0 percent of the amino acids in tea. and is present as the free amino acid only - it does not occur
in proteins. Theanitie 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
L-theanine was discovered as a constituent of green tea in 1949 by Sakato.- and in 1964 was approved as a
food additive in Japan. It is a water-soluble eompound and when ingested orally is absorbed in the small intestine.
In rats, peak plasma concentration was found 30 minutes after oral dosing.'

Theanine crosses the blood-brain bar-
rier via the large neutral amino acid (leueine-preferring) transport system. Theanine. when reaching the brain, has
been shown in rats to increase both serotonin atid dopamine production/ Theanine is hydrolyzed in the kidtiey to
In the brain L-theanine increases dopamine and serotonin production.^ although one study showed a de-
crease in serotonin in rats administered theanine.' Regardless of the mechanism, theanine increases alpha-brain
L-theanine has been studied extensively lor its effects on tumor cells and the sensitivity of those eells to
chemothcrapeutic agents. It appears theanine competitively inhibits glutamate transport into tumor eells. which
causes decreased intracellular glutathione (GSH) levels. Theanine also inhibits the efttux of chemotherapeutic
agents, such as doxorubicin. idarubiein. cisplatin. and irinotecan. causing them to accumulate in tumor cells. The-
anine also protects normal cells from damage by these drugs via antioxidant activity, specifically by maintaining
The antioxidant activity of L-theanine has been studied in regard to its effect on the oxidation of LDL
cholesterol. //; vitro testing using malondialdchyde as a marker of lipid peroxidation demonstrated inhibition of
LDL oxidation with theanine. although the effect was weaker than the potent antioxidant effect of green tea poly-
L-theanine may counteract the stimulatory effect of caffeine. In rats, theanine administered intravenously
after caffeine dosing, and at approximately the same dose, blunted the stimulant effect of caffeine seen on elec-
troencephalographic recordings. When given by itself in a smaller dose (20-40% of the original dose), theanine
administration resulted in excitatory effects, suggesting a dual activity of theanine. depending on the dose.'-

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