tea catechins
compound class / compound-catechins
茶カテキン類
Flavan-3-ols found in tea.
On this page (9 sections)
Reading the bitterness
A 2022 study examining astringency differences between 8 tea catechins and flavonol glycosides quantified astringency using aggregation and floating of artificial oil bodies coated with histatin-3-fused caleosin as the index. The astringency ranking of the 8 catechins showed galloylated forms stronger than non-galloylated: epicatechin gallate > epigallocatechin gallate > gallocatechin gallate > catechin gallate > epigallocatechin > epicatechin > gallocatechin > catechin. AFM/SEM observation showed the EGCG complex surface as rough and the rutinose (flavonol glycoside) complex as smooth; the authors attributed these to differences between puckering and velvety astringency. However, this is an in vitro physical model and does not directly demonstrate human perceptual subqualities.
A 2004 taste dilution analysis of black tea infusion reported that flavan-3-ol glycosides induced 『velvety and mouth-coating』 (in translation: "velvety and mouth-coating") astringency at an extremely low threshold, with quercetin glycoside threshold 0.001 µmol/L stated as 1/190,000 of the EGCG threshold. In contrast, a 2018 study targeting green tea infusion reported catechins as major contributing compounds to astringency and bitterness, with astringency highly correlated (R2 = 0.7878) to ECG and flavonol glycoside concentrations. For the same question 『茶カテキンは渋味に寄与するか』 (in translation: "does tea catechin contribute to astringency?"), green tea findings were supportive, whereas black tea taste dilution research identified flavonol glycosides as dominant, and conclusions diverged by tea type and method.
A 2011 cell assay examining green tea catechin TAS2R39 activation showed hTAS2R39-expressing cells displaying clear responses to 300 µM galloylated ECg and EGCg, with ECg strongest followed by EGCg, while non-galloylated EC and EGC responses were far weaker. An independent retest in 2013 derived threshold and EC50 from dose-response, reporting ECG and EGCG threshold 32 µM, EC 250 µM, EGC 500 µM, an ordering where galloylated forms show lower thresholds (stronger activation) consistent with the 2011 result. Co-authored work from University of Porto and DIfE also reported that non-galloylated (-)-epicatechin activates TAS2R4, TAS2R5, and TAS2R39, positioning galloylation not as an obligate requirement for receptor activation but as a factor affecting response strength.
The same 2013 study further reported that catechins act as agonists activating not only TAS2R39 but also hTAS2R14, noting 『これまではhTAS2R39の活性化のみが報告されていた』 (in translation: "hitherto only TAS2R39 activation had been reported"). Responses to hTAS2R14 were positive for (+)-catechin, ECG, and EGCG (thresholds 500, 125, 250 µM respectively), weak and uncertain for EC, and negative for EGC. A separate quantitative study using green tea infusion showed bitterness highly correlated (R2 = 0.7769) with galloylated catechin EGCG and ECG concentrations, with the cell assay relationship between galloylation and activation strength corresponding to actual infusion-based and sensory bitterness data.
Sources for this overview
Checked for this overview: Confirmed the 8-catechin astringency ranking in the AOB model and AFM/SEM observation descriptions
Checked for this overview: Confirmed black tea glycoside velvety astringency and 1/190,000 threshold description / Confirmed black tea flavonol glycoside as major astringency contributor—countervailing result
Quantitative analyses of the bitterness and astringency of catechins from green tea
Checked for this overview: Confirmed green tea astringency and EGCG/ECG concentration correlation R2=0.7878 / Confirmed green tea infusion bitterness and galloylated catechin correlation R2=0.7769
Checked for this overview: Confirmed 300 µM ECg and EGCg responses and weak EC and EGC responses
Checked for this overview: Confirmed Verbatim: 4-catechin thresholds 32/32/250/500 µM / Confirmed hTAS2R14 novel activation and threshold and negative results by compound
Different phenolic compounds activate distinct human bitter taste receptors
Checked for this overview: Confirmed non-galloylated EC activation of TAS2R4/5/39—independent replication
Follow the connections
tea catechins →are main contributors to→ astringency →is not synonymous with→ bitterness
tea catechins →activates→ TAS2R39
tea catechins →— galloylation strengthens→ bitterness →can be measured separately …→ astringency
Hypotheses and recipe candidates for this entry are on the Japanese page.
Structured claims — open a section to read each claim's confidence, evidence and limits
Composition and content (7)
Scope: Large-leaved kudingcha (Ilex latifolia, Ilex kudingcha)
Note: This review groups them under the term "flavones", but the compounds in the table are actually flavan-3-ols (catechins) (EC/EGCG/ECG). A new cross-entity connection showing these are compounds shared with green tea (ingredient-green-tea). The review does not state the content or contribution to bitterness. The primary isolation literature is citation [61], not data from this review itself.
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ingredient-kuding-tea —contains→ compound-catechinsScope: Shiga Prefecture Agricultural Technology Promotion Center Tea Industry Extension Office research field, Yabukita cultivar, second flush from June 28 to August 9, 2000, n=7 timepoints, 2 replicates
Note: Temporal change within the same second-flush window, distinct from the colloquial 「一番茶より二番茶の方がカテキンが多い」 (in translation: "second flush contains more catechins than first flush")—a different scale. Catechin yield (g/m²) rose until 7/19 then plateaued; concentration decline and yield dynamics require separate treatment.
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compound-catechins —shows_developmental_concentration_decline_due_to→ "Second-flush bud growth and hardening. In 2 periods—early growth (6/28 to 7/7) when bud weight surged and leaf-opening increased sharply, and after 7/19 when leaf-opening reached 100% and hardening progressed—catechin content decline (EGC+EC+EGCG+ECG sum, % dry weight) was large. Between 7/7–7/19 when growth slowed, decline was smaller."Scope: Same as above second-flush layer survey (July 1, 1999 harvest, no replicates, trial unit 4.32 m²)
Note: Records position-dependent differences within a single flush (corresponding to node position). Authors did not explain the physiological mechanism of the non-monotonic pattern, and no replicates preclude generalization.
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compound-catechins —has_composition→ "Second-flush layer-by-layer catechin content (measured 1 cm intervals from height above first-flush heading line, 1999 July 1 harvest) showed non-monotonic distribution: 2–3 cm layer 10.7%, 7–8 cm layer 10.9% (high), and 4–5 cm, 5–6 cm layers 9.1% (low). EGCG content showed the same pattern (2–3 cm layer 5.7% highest, 0–1 cm layer 4.4% lowest). Lower harvest position increased fresh leaf yield and catechin yield per unit area, but content percent showed no monotonic trend."Scope: Generalization by review author affiliated with Shizuoka Prefecture University Tea Comprehensive Research Center (individual primary studies and regions within the review are not specified)
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compound-catechins —shows_developmental_concentration_decline_due_to→ "Tea harvest progression. The review states 「カテキンは一番茶に多く，二番茶，三番茶になると減少し」 (in translation: "catechins abundant in first flush, decrease in second and third flushes")."Scope: Same review-level generalization
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compound-catechins —shows_developmental_concentration_decline_due_to→ "Tea leaf position. The review states 「成熟した葉（3・4葉目）よりも若い芽（1・2葉目）に多く含まれている」 (in translation: "more catechins in young buds (1st–2nd leaf) than mature leaves (3rd–4th leaf)")."Scope: Kochi Prefectural Agricultural Technology Center Tea Experiment Station; crude teas of first flush, cut-leaf, and second flush with a 50-second steaming time. Roasted 2 times with an automatic continuous hojicha roaster (exhaust temperature 90 C for the 1st roast, 100 C for the 2nd roast, with drum rotation speed adjusted for each flush and roasting degree).
Note: Direct quantification by HPLC (JASCO X-LC system). Only 1 sample per condition; the number of replicates is not stated.
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process-hojicha-roasting —reduces→ compound-catechinsScope: Layer: Food. LC-MS metabolite quantification. Oolong tea 2 cultivars (Tieguanyin and Jinguanyin) compared across processing stages.
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ingredient-tieguanyin-infusion —has_composition→ compound-catechinsSensory (2)
Scope: Artificial oil body in vitro assay
Note: This model does not provide direct human demonstration of independent astringency subqualities.
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compound-catechins —may_differ_from_flavonol_glycosides_in→ "Rough, puckering astringency vs smooth, velvety astringency"Scope: Tea infusions. Asserted for green tea; contradicted for black tea.
Note: The green tea literature regards catechins as the main contributor to astringency, but a taste-dilution study on black tea found flavonol glycosides to be dominant instead. The matrix (green tea vs. black tea) and the method (correlation vs. dilution-to-threshold) differ.
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compound-catechins —are_main_contributors_to→ sensation-astringentMechanism and receptors (3)
Scope: A cultured-cell assay. A clear response to 300 uM ECg and EGCg. ECg is strongest, followed by EGCg, with EC and EGC far weaker
Note: The abstract reports only a single concentration (300 uM). The receptor is broadly tuned (many flavonoids also activate TAS2R39).
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compound-catechins —activate→ receptor-tas2r39Scope: The role of the galloyl group is inferred from the hTAS2R39 response order (ECg, EGCg >> EC, EGC), described as resembling human taste-intensity observations.
Note: A direct human dose-response is not part of this assay. The human comparison in the receptor study is a citation, not something the study itself carried out.
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compound-catechins —have_bitterness_increased_by_galloylation→ sensation-bitterScope: A heterologous-expression cell receptor assay (cultured cells expressing hTAS2R14)
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compound-catechins —activate→ receptor-tas2r14How processing and cooking change it (4)
Scope: Layer: Food. Summary table of tea-plant buds (showing qualitative increase/decrease/no-change classification, not numeric values).
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process-tea-shading-cultivation —reduces→ compound-catechinsScope: Layer: Food. Green tea (unfermented, control) and Goishicha (two-stage fermented) extracted under identical conditions (hot water 100 mL, 1.5 g leaf, 5 minutes), n=5 comparison.
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process-goishi-cha-fermentation —reduces→ compound-catechinsScope: Layer: Food. Green tea (unfermented, control) and Ishizuchi-kurocha (2 samples from different producers) extracted under identical conditions (hot water 100 mL, 1.5 g leaf, 5 minutes), n=5 comparison.
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process-ishizuchi-kurocha-fermentation —reduces→ compound-catechinsScope: Layer: Food. Green tea (unfermented, control) and Awa-bancha (2 samples from different producers) extracted under identical conditions (hot water 100 mL, 1.5 g leaf, 5 minutes), n=5 comparison.
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process-awa-bancha-fermentation —reduces→ compound-catechins