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L-theanine

compound / compound-l-theanine

L-テアニン

L-theanine. Its effect on bitter-ligand response in hTAS2R16-expressing cells has been tested.

On this page (7 sections)
  1. Overview
  2. Sources for this overview (3)
  3. Topic hubs
  4. Follow the connections
  5. Related entries (10)
  6. Sensory (2)
  7. Mechanism and receptors (1)
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Reading the bitterness

L-theanine has been reported to inhibit, partially in a noncompetitive manner, the response of this receptor to its bitter ligand salicin in an assay using hTAS2R16-expressing HEK293T cells. Quantitatively, when theanine was added up to a highest concentration of 100 mM, the maximum response to salicin alone decreased by 55%, and the half-maximal effect concentration (EC50) increased 2- to 3-fold. This effect is also seen with other umami compounds (glutamate dimer and inosinate), and is not an action specific to theanine. Note that this result is from calcium response in heterologously expressed receptors, not human sensory testing, and extrapolation to the bitterness of tea or dishes overall cannot be confirmed within the scope of this collection.

In electronic tongue measurements targeting the major galloylated catechins of green tea (EGCG, ECG, GCG), umami amino acids including theanine have been reported to inhibit, in a concentration-dependent manner, the electronic tongue response to the bitterness intensity of these catechins. Theanine, together with glutamate, interacts more strongly with galloylated catechins than aspartate does, and hydrogen bonding is reported to be the main interactive force.

In a sensory and compositional analysis of green tea extracted 3 times in succession, some amino acids including L-theanine (glutamate and lysine) showed positive correlation with bitter and astringent attributes of the 1st infusion (the extract evaluated as having the strongest bitterness and astringency), together with catechins, gallic acid, and caffeine. On the other hand, the authors of the same study also argue that amino acids as a whole contribute to a fresh and sweet taste and have a role in mitigating bitterness.

Sources for this overview

  1. Suppression of hTAS2R16 Signaling by Umami Substances

    Rhyu Mee-Ra; Kim Yiseul; Misaka Takumi / 2020 / journal article / full text checked

    Checked for this overview: Used as the basis for the report that salicin response is inhibited noncompetitively / Used as the basis for the quantitative value of 55% reduction at 100 mM

  2. Interaction between major catechins and umami amino acids in green tea based on electronic tongue technology

    Liu Zhongying; Ran Qiansong; Li Qin; Yang Ting; Dai Yuqiao; Zhang Tuo; Fang Shimao; Pan Ke; Long Lin / 2023 / journal article / abstract checked

    Checked for this overview: Used as the basis for concentration-dependent inhibition of galloylated catechin bitterness by electronic tongue

  3. Three Successive Infusions: Scientific Insights Into a Traditional Green Tea Drinking Custom

    Zhang X; Yusuf A; Xu M; Isah MB / 2026 / journal article / full text checked

    Checked for this overview: Positive correlation between 1st-infusion bitterness and astringency and theanine concentration, with mitigation theory also noted

Follow the connections

L-theanine →antagonizes→ TAS2R16

epigallocatechin gallate →— electronic-tongue bittern…→ L-theanine

L-theanine →— perceived bitterness is a…→ green tea infusion →— sensory attribute→ bitterness

Structured claims — open a section to read each claim's confidence, evidence and limits

Sensory (2)

epigallocatechin gallate — electronic-tongue bitterness response was reduced by: L-theaninesupported

Scope: Electronic tongue measurement targeting major galloylated catechins of green tea (EGCG, ECG, GCG). Tested with theanine, glutamate, and aspartate

Note: Glutamate and aspartate have also been reported to inhibit the electronic tongue response to bitterness intensity in a concentration-dependent manner. This is based on electronic tongue (instrument) response values, not confirmation by human sensory panel. Theanine and glutamate interact more strongly with galloylated catechins than aspartate does, and hydrogen bonding is reported to be the main interactive force.

Reported that umami amino acids (theanine, Glu, Asp) inhibit electronic tongue response to bitterness intensity of galloylated catechins in a concentration-dependent manner
Limitations: Electronic tongue instrument response, not verification by human sensory panel. Experiment used purified single catechin solutions, not matcha itself.
Source: Interaction between major catechins and umami amino acids in green tea based on electronic tongue technology (Liu Zhongying; Ran Qiansong; Li Qin; Yang Ting; Dai Yuqiao; Zhang Tuo; Fang Shimao; Pan Ke; Long Lin, 2023) · abstract checked
Show datacompound-egcg —has_e_tongue_bitterness_reduced_by→ compound-l-theanine
claim: clm-egcg-etongue-bitterness-theanine / type: sensory / updated: 2026-09-02
L-theanine — perceived bitterness is associated with: green tea infusionsupported

Scope: Layer: food. Green tea extracted in 3 successive infusions (GT1-GT3), five-taste sensory evaluation by electronic tongue, Pearson correlation analysis, and PLSR.

"GT1 was distinctly characterized by its pronounced bitterness and puckery, correlating strongly with elevated levels of catechins (epigallocatechin gallate, epicatechin gallate), gallic acid, caffeine, and certain amino acids (L‐theanine, L‐glutamic acid, and L‐lysine)." And: "amino acids contribute to the fresh and sweet taste of tea, playing a key role in enhancing the overall refreshing quality of tea and mitigating its bitterness."
Limitations: This is a correlational analysis, not an intervention experiment that manipulated L-theanine alone. The direction of its effect on bitterness (positive correlation vs. mitigation) is not necessarily stated consistently within the text.
Source: Three Successive Infusions: Scientific Insights Into a Traditional Green Tea Drinking Custom (Zhang X; Yusuf A; Xu M; Isah MB, 2026) · full text checked
Show datacompound-l-theanine —has_perceived_bitterness_associated_with→ ingredient-green-tea
claim: clm-w71a2-theanine-correlates-first-infusion-bitterness / type: sensory / updated: 2026-09-07

Mechanism and receptors (1)

L-theanine antagonizes TAS2R16preliminary

Scope: The same hTAS2R16-expressing cell system

Note: Reported as partial, non-surmountable antagonism. Not extrapolated to the overall bitterness of tea or dishes.

L-theanine was reported to act as a partial, non-surmountable antagonist of the bitter-ligand response of wild-type hTAS2R16.
Limitations: No human sensory testing. This does not explain the overall bitterness of tea.
Source: Suppression of hTAS2R16 Signaling by Umami Substances (Rhyu Mee-Ra; Kim Yiseul; Misaka Takumi, 2020) · full text checked
At the highest concentration of L-theanine (100 mM), the maximal response to salicin alone decreased by 55%, and the EC50 rose 2-3 fold. Verbatim: "the maximal response of salicin alone was gradually decreased by 61%, 50%, and 55% at the highest concentration of Glu-Glu (10 mM), IMP (30 mM), and l-theanine (100 mM), respectively".
Limitations: Not a human sensory test. Whether this effect occurs at the concentrations of theanine found in tea infusions is outside the scope of this study.
Source: Suppression of hTAS2R16 Signaling by Umami Substances (Rhyu Mee-Ra; Kim Yiseul; Misaka Takumi, 2020) · full text checked
Show datacompound-l-theanine —antagonizes→ receptor-tas2r16
claim: clm-theanine-antagonizes-tas2r16 / type: mechanism / updated: 2026-08-31

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