Theanine

Theanine
IUPAC name 2-Amino-4-(ethylcarbamoyl)butyric acid[citation needed]
Other names N5-Ethyl-L-glutamine[1]
Identifiers
CAS number	3081-61-6 S Y
PubChem	228398, 9964226 R, 439378 S
ChemSpider	198778 Y, 8139819 R Y, 388498 S Y
UNII	8021PR16QO Y
EC number	3081-61-6
MeSH	theanine
ChEBI	CHEBI:17394 Y
Jmol-3D images	{{#if:CC[nH]:c(:[o])CCC(N)c(:[o]):[oH]CCNC(=O)CCC(N)C(O)=O|Image 1 Image 2
SMILES CC[nH]:c(:[o])CCC(N)c(:[o]):[oH] CCNC(=O)CCC(N)C(O)=O
InChI InChI=1S/C7H14N2O3/c1-2-9-6(10)4-3-5(8)7(11)12/h5H,2-4,8H2,1H3,(H,9,10)(H,11,12) Y Key: DATAGRPVKZEWHA-UHFFFAOYSA-N Y
Properties
Molecular formula	C7H14N2O3
Molar mass	174.20 g mol−1
Related compounds
Related alkanoic acids	Arginine Pantothenic acid Hopantenic acid
Related compounds	Panthenol
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Theanine /ˈθiːəniːn/, also gamma-glutamylethylamide or 5-N-ethyl-glutamine, is an amino acid and a glutamic acid analog primarily found in tea (Camellia sinensis),^[2] and also in the basidiomycete mushroom Boletus badius and in guayusa.^[3] The L-enantiomer is the form which is found in tea and used as a supplement by humans.

L-Theanine was discovered as a constituent of green tea in 1949 and was approved in Japan in 1964 for unlimited use in all foods, including chocolates, soft drinks, and herb teas, except infant foods. It also provides a unique umami (brothy or savory) taste and flavor to green tea infusion.^[4]

In 1950, the tea laboratory of Kyoto successfully separated theanine from gyokuro leaf, which has high theanine content.^{[citation needed]} Theanine is an analog to glutamine and glutamate, and can cross the blood–brain barrier.^[5] It is sold in the US as a dietary supplement, and is classified by the Food and Drug Administration (FDA) as a generally recognized as safe (GRAS) ingredient.^[6] However, the German Federal Institute for Risk Assessment (Bundesinstitut für Risikobewertung, BfR) has objected to the addition of isolated theanine to beverages.^[7]

Research

Early studies of theanine involved much larger doses than are found in an everyday cup of tea. Researchers wonder whether drinking tea might have the same effects found in those studies.^[8] However, one recent study by Unilever found that smaller doses typical of those found in a cup of tea did induce changes in alpha waves as shown by EEG.^[9]

Effects on the brain

Able to cross the blood–brain barrier, theanine has psychoactive properties.^[10] Theanine has been studied for its potential ability to reduce mental and physical stress,^[11] improve cognition,^[12] and boost mood and cognitive performance in a synergistic manner with caffeine.^{[13][14][15][16][17][18]}

Theanine promotes alpha wave production in the brain.^[10] While structurally similar to the excitatory neurotransmitter glutamate, theanine has only weak affinity for the glutamate receptor on postsynaptic cells.^[19] It also has low affinity for AMPA, kainate, and NMDA receptors but does however increase brain dopamine levels.^[20] Its effect on serotonin is still a matter of debate in the scientific community, with studies showing increases and decreases in brain serotonin levels using similar experimental protocols.^[5][21] It has also been found that injecting spontaneously hypertensive mice with theanine significantly lowered levels of 5-hydroxyindoles in the brain.^[22] Researchers also speculate it may inhibit glutamate excitotoxicity thereby increasing glutamate.^[20]

Studies on test rats have shown even repeated, extremely high doses of theanine cause little to no harmful psychological or physical effects.^[23] Theanine showed neuroprotective effects in one rat study.^[24]

A placebo-controlled trial has shown adding theanine to ongoing antipsychotic medication is helpful in reducing some symptoms of schizophrenia.^[7][25]

Several beverage manufacturers are selling drinks containing theanine and are marketing them as drinks to help people focus and concentrate,^[8] while other manufacturers claim relaxing and tranquillizing properties.^[7]

As a supplement

In 2003, the German Federal Institute for Risk Assessment (Bundesinstitut für Risikobewertung, BfR) objected to the addition of isolated theanine to beverages. The institute stated the amount of theanine consumed by regular drinkers of tea or coffee is virtually impossible to determine. While it was estimated the quantity of green tea consumed by the average Japanese tea drinker per day contains about 20 mg of the substance, there are no studies measuring the amount of theanine being extracted by typical preparation methods, or the percentage lost by discarding the first infusion. Therefore, with the Japanese being exposed to possibly much less than 20 mg per day, and Europeans presumably even less, pharmacological reactions to drinks typically containing 50 mg of theanine per 500 millilitres cannot be excluded, in the opinion of the BfR. Such reactions could include impairment of psychomotor skills and amplification of the sedating effects of alcohol and hypnotics.^[7]

In 2006, a study found no consistent, statistically significant treatment-related adverse effects on behavior, morbidity, mortality, body weight, food consumption and efficiency, clinical chemistry, hematology, or urinalysis in rats fed high doses of theanine for 13 weeks.^[23] Large studies in humans have not been undertaken, however several smaller-scale studies (less than 100 participants) have shown increased alpha wave generation and lowered anxiety, along with benefits to sleep quality in patients with ADHD.^{[11][26][26][27][28]}

The combination of L-theanine and caffeine has been shown to promote faster simple reaction time, faster numeric working memory reaction time and improved sentence verification accuracy.^{[13][15][29][30]}

L-Theanine may help the body's immune response to infection by boosting the disease-fighting capacity of gamma delta T cells. The study, published in 2003, included a four-week trial with 11 coffee drinkers and 10 tea drinkers, who consumed 600 milliliters of coffee or black tea daily. Blood sample analysis found the production of antibacterial proteins was up to five times higher in the tea drinkers, an indicator of a stronger immune response.^[31] L-Theanine may contain mast cell-stabilizing properties in an animal model.^[32]

See also

• gamma-Glutamylmethylamide
• Green tea

References