L-theanine, also known as L-glutamic acid γ-ethylamide, prevents extracellular glutamine from entering neurons, which in turn prevents glutamate from being released exocytotically [3]. L-theanine (500 μM; 72 hours) raises glutathione levels in astrocytes and inhibits neuronal death brought on by excess dopamine [3]. Glutathione synthesis involves L-theanine (0–5 mM; 72 hours) [3]. Melanoma cells' viability is dose-dependently inhibited by L-theanine (0.1–5 mM; 24 hours), but not that of normal epidermal melanocytes [4]. In A375 cells, L-theanine (1–5 mM; 24 hours) causes apoptosis, suppresses cell migration, and stops the cell cycle in the G0/G1 phase [4]. Additionally, B16–F10 melanoma cells' migration, apoptosis, and proliferation are impacted by L-theanine (1–5 mM; 24 hours) [4]. By blocking mitochondria-mediated processes and lowering ROS generation, L-theanine prevents cadmium-induced PC12 cell apoptosis [5].

In the striatum of normal mice, L-theanine (4.0 mg/kg; oral; once daily for 14 days) increases the glutathione concentration [3].

Cell proliferation assay [4]
Cell Types: A375 and PIG1 Cell
Tested Concentrations: 0.1, 0.5, 1, 2 and 5 mM
Incubation Duration: 24 hrs (hours)
Experimental Results: The viability of A375 cells diminished in a dose-dependent manner, but that of PIG1 cells did not.

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Cell cycle analysis [4]
Cell Types: A375
Tested Concentrations: 1, 2 and 5 mM
Incubation Duration: 24 hrs (hours)
Experimental Results: Causes dose-dependent accumulation of A375 cells in G0/G1 phase and prevents cells from entering S phase.

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Western Blot Analysis[4]
Cell Types: A375
Tested Concentrations: 1, 2 and 5 mM
Incubation Duration: 24 h
Experimental Results: Remarkably diminished the expression of proliferating cell nuclear antigen (PCNA), diminished protein levels of cyclinD1, cyclinE1, and cyclin-dependent protein kinase (CDK2 and CDK4). Potentiated the expression of cyclin-dependent kinase inhibitor 1A (CDKN1A, p21). Dose-dependently increased the levels of apoptosis-promoting proteins including BAX and cleaved-caspase3 and diminished the level of antiapoptotic protein BCL-2. Concentration dependently diminished the protein levels of ICAM-1, VCAM-1, MMP9, and MMP2. Dose-dependently increased the p53 expression.

Animal/Disease Models: Healthy male ICR mice, body weight 32-34 grams [3]
Doses: 4.0 mg/kg
Route of Administration: Orally, one time/day for 14 days
Experimental Results: Glutathione content in the striatum increased Dramatically, but Glutathione levels were not increased in the midbrain.

Absorption, Distribution and Excretion
From animal studies, it appears that L-theanine is absorbed from the small intestine via a sodium-coupled active transport process and appears to cross the blood-brain barrier. It has been found in the rat studies that the D-enantiomer of theanine may decrease the absorption of L-theanine.

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Metabolism / Metabolites
In medium containing theanine with glutaminase in vitro, glutamate gradually generated, showing that glutaminase reacted with theanine. Furthermore, the generation of glutamate increased by reaction of theanine and gamma-glutamyltranspeptidase (gamma-GTP), showed that gamma-GTP converted theanine to glutamate. It is expected that theanine metabolism occurred by hydrolysis and rearrangement reaction by gamma-GTP in the liver. Namely, it is suggested that the metabolism of theanine mediated by glutaminase and gamma-GTP and the increase of glutamate mediated GSH is important for theanine-induced action.

Interactions
The aim of this study was to compare 50 mg caffeine, with and without 100 mg L-theanine, on cognition and mood in healthy volunteers. The effects of these treatments on word recognition, rapid visual information processing, critical flicker fusion threshold, attention switching and mood were compared to placebo in 27 participants. Performance was measured at baseline and again 60 min and 90 min after each treatment (separated by a 7-day washout). Caffeine improved subjective alertness at 60 min and accuracy on the attention-switching task at 90 min. The L-theanine and caffeine combination improved both speed and accuracy of performance of the attention-switching task at 60 min, and reduced susceptibility to distracting information in the memory task at both 60 min and 90 min. These results replicate previous evidence which suggests that L-theanine and caffeine in combination are beneficial for improving performance on cognitively demanding tasks.
A combination of green tea extract and l-theanine (LGNC-07) has been reported to have beneficial effects on cognition in animal studies. In this randomized, double-blind, placebo-controlled study, the effect of LGNC-07 on memory and attention in subjects with mild cognitive impairment (MCI) was investigated. Ninety-one MCI subjects whose Mini Mental State Examination-K (MMSE-K) scores were between 21 and 26 and who were in either stage 2 or 3 on the Global Deterioration Scale were enrolled in this study. The treatment group (13 men, 32 women; 57.58 +/- 9.45 years) took 1,680 mg of LGNC-07, and the placebo group (12 men, 34 women; 56.28 +/- 9.92 years) received an equivalent amount of maltodextrin and lactose for 16 weeks. Neuropsychological tests (Rey-Kim memory test and Stroop color-word test) and electroencephalography were conducted to evaluate the effect of LGNC-07 on memory and attention. Further analyses were stratified by baseline severity to evaluate treatment response on the degree of impairment (MMSE-K 21-23 and 24-26). LGNC-07 led to improvements in memory by marginally increasing delayed recognition in the Rey-Kim memory test (P=0 .0572). Stratified analyses showed that LGNC-07 improved memory and selective attention by significantly increasing the Rey-Kim memory quotient and word reading in the subjects with MMSE-K scores of 21-23 (LGNC-07, n=11; placebo, n=9). Electroencephalograms were recorded in 24 randomly selected subjects hourly for 3 hours in eye-open, eye-closed, and reading states after a single dose of LGNC-07 (LGNC-07, n=12; placebo, n=12). Brain theta waves, an indicator of cognitive alertness, were increased significantly in the temporal, frontal, parietal, and occipital areas after 3 hours in the eye-open and reading states. Therefore, this study suggests that LGNC-07 has potential as an intervention for cognitive improvement.
Recent neuropharmacological research has suggested that certain constituents of tea may have modulatory effects on brain state. The bulk of this research has focused on either L-theanine or caffeine ingested alone (mostly the latter) and has been limited to behavioral testing, subjective rating, or neurophysiological assessments during resting. Here, we investigated the effects of both L-theanine and caffeine, ingested separately or together, on behavioral and electrophysiological indices of tonic (background) and phasic (event-related) visuospatial attentional deployment. Subjects underwent 4 d of testing, ingesting either placebo, 100 mg of L-theanine, 50 mg of caffeine, or these treatments combined. The task involved cued shifts of attention to the left or right visual hemifield in anticipation of an imperative stimulus requiring discrimination. In addition to behavioral measures, we examined overall, tonic attentional focus as well as phasic, cue-dependent anticipatory attentional biasing, as indexed by scalp-recorded alpha-band (8-14 Hz) activity. We found an increase in hit rate and target discriminability (d') for the combined treatment relative to placebo, and an increase in d' but not hit rate for caffeine alone, whereas no effects were detected for L-theanine alone. Electrophysiological results did not show increased differential biasing in phasic alpha across hemifields but showed lower overall tonic alpha power in the combined treatment, similar to previous findings at a larger dosage of L-theanine alone. This may signify a more generalized tonic deployment of attentional resources to the visual modality and may underlie the facilitated behavioral performance on the combined ingestion of these 2 major constituents of tea.
This review summarizes the literature on the association between two dietary components of tea, caffeine and L-theanine, and the psychological outcomes of consumption; it also identifies areas for future research. The studies reviewed suggest that caffeinated tea, when ingested at regular intervals, may maintain alertness, focused attention, and accuracy and may modulate the more acute effects of higher doses of caffeine. These findings concur with the neurochemical effects of L-theanine on the brain. L-theanine may interact with caffeine to enhance performance in terms of attention switching and the ability to ignore distraction; this is likely to be reflective of higher-level cognitive activity and may be sensitive to the detrimental effects of overstimulation. Further research should investigate the interactive effects of caffeine, L-theanine, and task complexity, utilize a range of ecologically valid psychological outcomes, and assess the neuroprotective effects of L-theanine using epidemiological or longer-term intervention studies among individuals at risk of neurodegenerative disease.
For more Interactions (Complete) data for Theanine (32 total), please visit the HSDB record page.

[1]. L-Theanine: properties, synthesis and isolation from tea. J Sci Food Agric. 2011 Aug 30;91(11):1931-9.

[2]. L-Theanine reduces psychological and physiological stress responses. Biol Psychol. 2007 Jan;74(1):39-45.

[3]. l-Theanine protects against excess dopamine-induced neurotoxicity in the presence of astrocytes. J Clin Biochem Nutr. 2016 Sep;59(2):93-99.

[4]. L-Theanine inhibits melanoma cell growth and migration via regulating expression of the clock gene BMAL1. Eur J Nutr. 2022 Mar;61(2):763-777.

[5]. Protective Effect of L-Theanine on Cadmium-Induced Apoptosis in PC12 Cells by Inhibiting the Mitochondria-Mediated Pathway. Neurochem Res. 2015 Aug;40(8):1661-70.

N(5)-ethyl-L-glutamine is a N(5)-alkylglutamine where the alkyl group is ethyl. It has been isolated from green tea. It has a role as a neuroprotective agent, a plant metabolite and a geroprotector. It is a tautomer of a N(5)-ethyl-L-glutamine zwitterion.
Theanine, a precursor of ethylamine, is found in green tea. It is under investigation in clinical trial NCT00291070 (Effects of L-Theanine in Boys With ADHD).
L-Theanine has been reported in Camellia sinensis, Eurya japonica, and other organisms with data available.
See also: Green tea leaf (part of).

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Mechanism of Action
L-theanine (N-ethyl-L-glutamine) or theanine is a major amino acid uniquely found in green tea. L-theanine has been historically reported as a relaxing agent, prompting scientific research on its pharmacology. Animal neurochemistry studies suggest that L-theanine increases brain serotonin, dopamine, GABA levels and has micromolar affinities for AMPA, Kainate and NMDA receptors. In addition has been shown to exert neuroprotective effects in animal models possibly through its antagonistic effects on group 1 metabotrophic glutamate receptors. Behavioural studies in animals suggest improvement in learning and memory. Overall, L-theanine displays a neuropharmacology suggestive of a possible neuroprotective and cognitive enhancing agent and warrants further investigation in animals and humans.
In an investigation of the mechanisms of the neuroprotective effects of theanine (gamma-glutamylethylamide) in brain ischemia, inhibition by theanine of the binding of [(3)H](RS)-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA), [(3)H]kainate, and [(3)H](E)-3-(2-phenyl-2-carboxyethenyl)-4,6-dichloro-1-H-indole-2-carboxylic acid (MDL 105,519) to glutamate receptors was studied in terms of its possible inhibiting effects on the three receptor subtypes (AMPA, kainate, and NMDA glycine), with rat cortical neurons. Theanine bound the three receptors, but its IC50 of theanine was 80- to 30,000-fold less than that of L-glutamic acid.
In this study, the inhibitory effect of L-theanine, an amino acid derivative of tea, on the rewarding effects of nicotine and its underlying mechanisms of action were studied. We found that L-theanine inhibited the rewarding effects of nicotine in a conditioned place preference (CPP) model of the mouse and reduced the excitatory status induced by nicotine in SH-SY5Y cells to the same extent as the nicotine receptor inhibitor dihydro-beta-erythroidine (DHbetaE). Further studies using high performance liquid chromatography, western blotting and immunofluorescence staining analyses showed that L-theanine significantly inhibited nicotine-induced tyrosine hydroxylase (TH) expression and dopamine production in the midbrain of mice. L-theanine treatment also reduced the upregulation of the a(4), beta(2) and a(7) nicotine acetylcholine receptor (nAChR) subunits induced by nicotine in mouse brain regions that related to the dopamine reward pathway, thus decreasing the number of cells that could react to nicotine. In addition, L-theanine treatment inhibited nicotine-induced c-Fos expression in the reward circuit related areas of the mouse brain. Knockdown of c-Fos by siRNA inhibited the excitatory status of cells but not the upregulation of TH induced by nicotine in SH-SY5Y cells. Overall, the present study showed that L-theanine reduced the nicotine-induced reward effects via inhibition of the nAChR-dopamine reward pathway. These results may offer new therapeutic strategies for treatment of tobacco addiction.
L-theanine, previously shown to penetrate the blood-brain barrier through the leucine-preferring transport system, has been demonstrated to produce significant increases in serotonin and/or dopamine concentrations in the brain principally in the striatum, hypothalamus and hippocampus.
For more Mechanism of Action (Complete) data for Theanine (9 total), please visit the HSDB record page.

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Therapeutic Uses
EXPL THER Recent neuropharmacological research has suggested that certain constituents of tea may have modulatory effects on brain state. The bulk of this research has focused on either L-theanine or caffeine ingested alone (mostly the latter) and has been limited to behavioral testing, subjective rating, or neurophysiological assessments during resting. Here, we investigated the effects of both L-theanine and caffeine, ingested separately or together, on behavioral and electrophysiological indices of tonic (background) and phasic (event-related) visuospatial attentional deployment. Subjects underwent 4 d of testing, ingesting either placebo, 100 mg of L-theanine, 50 mg of caffeine, or these treatments combined. The task involved cued shifts of attention to the left or right visual hemifield in anticipation of an imperative stimulus requiring discrimination. In addition to behavioral measures, we examined overall, tonic attentional focus as well as phasic, cue-dependent anticipatory attentional biasing, as indexed by scalp-recorded alpha-band (8-14 Hz) activity. We found an increase in hit rate and target discriminability (d') for the combined treatment relative to placebo, and an increase in d' but not hit rate for caffeine alone, whereas no effects were detected for L-theanine alone. Electrophysiological results did not show increased differential biasing in phasic alpha across hemifields but showed lower overall tonic alpha power in the combined treatment, similar to previous findings at a larger dosage of L-theanine alone. This may signify a more generalized tonic deployment of attentional resources to the visual modality and may underlie the facilitated behavioral performance on the combined ingestion of these 2 major constituents of tea.
EXPL THER The non-proteinic amino acid L-theanine and caffeine, a methylxanthine derivative, are naturally occurring ingredients in tea. The present study investigated the effect of a combination of 97 mg L-theanine and 40 mg caffeine as compared to placebo treatment on cognitive performance, alertness, blood pressure, and heart rate in a sample of young adults (n = 44). Cognitive performance, self-reported mood, blood pressure, and heart rate were measured before L-theanine and caffeine administration (i.e. at baseline) and 20 min and 70 min thereafter. The combination of moderate levels of L-theanine and caffeine significantly improved accuracy during task switching and self-reported alertness (both P < 0.01) and reduced self-reported tiredness (P < 0.05). There were no significant effects on other cognitive tasks, such as visual search, choice reaction times, or mental rotation. The present results suggest that 97 mg of L-theanine in combination with 40 mg of caffeine helps to focus attention during a demanding cognitive task.
EXPL THER The aim of this study was to compare 50 mg caffeine, with and without 100 mg L-theanine, on cognition and mood in healthy volunteers. The effects of these treatments on word recognition, rapid visual information processing, critical flicker fusion threshold, attention switching and mood were compared to placebo in 27 participants. Performance was measured at baseline and again 60 min and 90 min after each treatment (separated by a 7-day washout). Caffeine improved subjective alertness at 60 min and accuracy on the attention-switching task at 90 min. The L-theanine and caffeine combination improved both speed and accuracy of performance of the attention-switching task at 60 min, and reduced susceptibility to distracting information in the memory task at both 60 min and 90 min. These results replicate previous evidence which suggests that L-theanine and caffeine in combination are beneficial for improving performance on cognitively demanding tasks.
EXPL THER L-Theanine, an ethylamide derivate of glutamate found in abundance in green tea, has been shown to exert beneficial actions in animal models for several neurological disorders. /Authors/ here investigated for the first time the effect of L-theanine intake on seizure susceptibility using acute pilocarpine and pentylenetetrazol (PTZ) mouse models for studying, respectively, limbic seizures or primarily generalized seizures. Moreover, /authors/ studied the effect of l-theanine intake on extracellular hippocampal and cortical glutamate and gamma-aminobutyric acid (GABA) levels, using in vivo microdialysis. Feeding mice with a 4% L-theanine solution significantly decreased their susceptibility to pilocarpine-induced seizures whereas susceptibility to PTZ-induced seizures was increased. The latter effect was linked to decreased extracellular GABA concentrations in frontal cortex.
For more Therapeutic Uses (Complete) data for Theanine (16 total), please visit the HSDB record page.

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Drug Warnings
Pregnant women and nursing mothers should avoid L-theanine supplements. Use of L-theanine supplements cocomiitantly with cancer chemotherapeutic agents must be done under medical supervision.
L-theanine is contraindicated in those who are hypersensitive to any component of an L-theanine-containing product.

C7H14N2O3

174.1977

174.1

3081-61-6

L-Theanine-d5;1217451-85-8

439378

White to off-white solid powder

1.2±0.1 g/cm3

430.2±40.0 °C at 760 mmHg

207°C

214.0±27.3 °C

0.0±2.2 mmHg at 25°C

1.492

-1.02

3

4

5

12

170

1

CCNC(=O)CC[C@@H](C(=O)O)N

DATAGRPVKZEWHA-YFKPBYRVSA-N

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)/t5-/m0/s1

(2S)-2-amino-5-(ethylamino)-5-oxopentanoic acid

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: Please store this product in a sealed and protected environment, avoid exposure to moisture.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

H2O : ~150 mg/mL (~861.08 mM)

Solubility in Formulation 1: 100 mg/mL (574.05 mM) in PBS (add these co-solvents sequentially from left to right, and one by one), clear solution; with sonication.

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 (Please use freshly prepared in vivo formulations for optimal results.)