L-Theanine

L-Theanine(3081-61-6), like the protein-based amino acids, exists as a zwitterionic species and is a colorless crystalline solid [needles, melting point 214-216 ℃]^[2]. Studies on the buffering capacity of green tea extracts suggest the pKa of the theanine amino group to be^{[10, 12]}. The pKa of the carboxyl unit was not formally quantified due to interference from other acidic species. However, comparisons with close structural analogues such as glutamine suggest the value lies in the range 2.1-2.5^[13] Theanine is stable under acidic conditions but undergoes base hydrolysis to yield glutamic acid and ethylamine^{[2, 14]}. During infusion, theanine does not react chemically with any of the other tea components. This is in contrast to catechins, which can precipitate from solution as a result of π stacking interactions with caffeine^{[15, 16]}or can react with proteins and enzymes such as lipoxygenase, α-amylase, pepsin, trypsin and lipase^[15].

Green tea leaves have many beneficial health activities including anti-inflammatory, anti-carcinogenic, anti-mutagenic, antioxidative and antimicrobial and hypolipidemic effects^{[38, 39]}. Those beneficial effects are largely originated from the biological effects from L-Theanine as below:
Ingestion of theanine has been reported to facilitate the generation of alpha brain waves, which are associated with a relaxed but alert mental state^[40]. In addition, theanine is reported to promote the release of the inhibitory neurotransmitter γ-aminobutyric acid [GABA], which in turn regulates dopamine and serotonin levels in the brain^[41]. Thus, theanine consumption has been closely associated with relaxation and improved learning ability.

FDA classified L-theanine as “generally recognized as safe.” This classification means that they believe this additive to be safe when people use it as the packaging suggests.
Women who are pregnant or breastfeeding should not use L-theanine.

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L-Theanine is the major amino acid found in Camellia sinensis, the source of green tea. It is an analog of the excitatory neurotransmitter, glutamate, and thusly, binds to glutamate receptors. L-Theanine can antagonize various glutamate receptor subtypes as well as inhibit glutamine and glutamate transporters, which has been shown to be neuroprotective in animal models of focal cerebral ischemia. Further, L-theanine is reported to increase brain levels of dopamine, serotonin, GABA, nerve growth factor, and brain-derived neurotrophic factor.

White Crystalline Solid

A non-protein amino acid mainly found naturally in the green tea plant. It may have activity in modulating the metabolism of cancer chemotherapeutics agents.

L-Theanine is a safe and non-toxic photogenic food supplement.
It has been studied as a food additive and functional food in relation to human nutrition.
It has noticeable bioactivities including anti-cerebral ischemia-reperfusion injury, stress-reducing, antitumor, anti-aging, and anti-anxiety activities.

ChEBI: L-Theanine 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.

L-Theanine is one of the active ingredients in green tea. It has a variety of physiological functions such as protecting nerves, lowering blood pressure, antioxidant, regulating immune response, improving cognitive ability and calming the mind. Therefore, L-Theanine helps to improve concentration and cognitive ability, improve immune function, reduce stress, relieve anxiety and depression symptoms, and improve sleep. In addition, studies have shown that L-Theanine also helps to alleviate symptoms in patients with high blood pressure and reduces the risk of pancreatic cancer in women.

Amino acid analog of glutamine and component of green tea. Shown to bind to AMPA, Kainate, NMDA and group I mGlu receptors. Displays neuroprotective effects in vivo . Promotes self-renewal of human embryonic stem cells (hESC).

Theanine is able to bind to AMPA, kainite, and NMDA glycine receptors in rat cortical neurons but with less affinity than glutamic acid. It has been studied as a glutamate transport inhibitor, preventing glutamate uptake by M5076 ovarian sarcoma-bearing mouse cells and increasing the effect of doxorubicin on tumor growth in M5076 mice.

Side effects have not been reported. But drinking too much tea may cause: Headaches; Trouble staying asleep; Nausea (feeling like you are going to throw up); Irritability; Stomach pain

Theanine was first chemically synthesised in 1942 by Lichtenstein^[28]with a yield of 90 g kg^-1 by treating pyrrolidone-5-carboxylic acid with aqueous ethylamine for 20 days at 37 ℃. A number of other synthetic approaches have since been developed including a large-scale production method involving the reaction of γ-benzyl glutamate in the presence of trityl chloride and ethylamine [339 g kg^-1]^[29]and a two-step approach involving initial dehydration of L-glutamic acid to L-pyrrolidone carboxylic acid followed by ring opening in the presence of ethylamine to yield theanine [374 g kg^-1]^[30]. More recently, theanine was produced in four steps starting from commercially available N-phthaloyl-L-glutamic acid, which was dehydrated to the corresponding cyclic anhydride by reaction with acetic anhydride and then the ring was opened by reaction with ethylamine. Subsequent de-protection of the amine unit with hydrazine hydrate gave theanine with a 700 g kg^-1 overall yield^[31].
In the tea plant, theanine is bio-synthesised from glutamic acid and ethylamine by the enzyme theanine synthetase. However, the enzyme is very labile and cannot be used to produce the amino acid in commercial quantities^[32]. Therefore, other methods for the enzymatic synthesis of theanine have been developed using bacterial enzymes such as glutaminase, glutamine synthetase and γ-glutamyl-transpeptidase.

NF-kB | TGF-β/Smad | IL Receptor | COX | PGE | CTGF

There is some evidence L-theanine supplements may lower blood pressure. If you take one or more medications to lower blood pressure, you may want to avoid taking L-theanine. Due to its relaxing and sleep-supporting effects, L-theanine may also have an additive effect with some sedative medications. Avoid taking supplements containing D-theanine as it may prevent the absorption of L-theanine in the body. 

The tropical and temperate regions of Asian, African, South American countries are considered the main origin of tea plant [C. sinensis or Thea sinensis]. It is a member of Theaceae family. The majority members of Theaceae family are obtained from India, Sri Lanka, China, and Japan. The physiological properties and colour e.g. black, white, green, yellow or oolong tea strongly depends upon the degree of fermentation and processing conditions^[20]. L-theanine is mainly derived from a non-edible mushroom of Xerocomus badius, and C. sinensis. It is an amino acid which accumulates in the leaves of tea like C. sasanqua and C. japonica^[21]. In tea, L-theanine is responsible for a strong smell [aroma]in general and in particular it is linked with tea umami taste^[22]. From the compositional viewpoint, L-theanine comprises approximately 50% of the tea contents. Whereas, the dry tea contains 1-3% of L-theanine only, this higher or lower ratio of L-theanine can vary depending on several factors i.e. cultivation zone, production season, processing techniques, class of tea, time and type of harvest, etc^[27]. Additionally, the harvested tea at the beginning of summer is reported to have more theanine compared with tea harvested in late summer^[27]. Moreover, L-theanine concentration also depends on the type/class of tea. According to one study, a specific type of C. sinensis var. Sinensis has more L-theanine contents as compared to the C. sinensis var. Assamica^[23]. 

Room temperature