Definition:
Tea catechins are a family of flavanol polyphenols found in Camellia sinensis leaves, comprising four primary compounds — epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin gallate (ECG), and epicatechin (EC) — along with their non-epicatechin isomers and galloylated variants; EGCG is the most abundant (typically 50–60% of total catechins in green tea) and the most extensively studied for health effects, while the relative proportions shift with tea type, growing method, harvest season, and processing — with green tea preserving all four major catechins and black tea converting most to theaflavins and thearubigins through oxidation.
In-Depth Explanation
The word “catechin” in tea health marketing typically refers to all four compounds together, or often specifically to EGCG alone. Breaking down the individual catechins clarifies both their distinct properties and the claims made about them.
The Four Major Tea Catechins
1. Epigallocatechin Gallate (EGCG)
The dominant catechin in green tea by concentration (~100–200mg per cup of gyokuro/sencha; lower in less concentrated preparations). EGCG’s structure — a galloyl ester group attached to an epigallocatechin base — makes it the most biologically active and the most bitter/astringent. Nearly all significant clinical research on tea catechins’ anti-tumor, cardiovascular, and metabolic effects has focused primarily on EGCG or mixed EGCG-dominant extracts. See EGCG for a detailed entry.
2. Epigallocatechin (EGC)
The second most abundant green tea catechin (typically 30–70mg per cup of standard green tea). EGC lacks the gallate group, making it less bitter and less effective as a free-radical scavenger than EGCG but still contributing meaningfully to total antioxidant capacity. EGC has been studied for antimicrobial properties and some anti-inflammatory effects, but receives far less research attention than EGCG.
3. Epicatechin Gallate (ECG)
Structurally similar to EGCG but lacking one hydroxyl group on the B-ring, ECG is typically present at 30–60mg per cup. Like EGCG, ECG’s gallate group contributes to its astringency and its bioactivity. ECG shows activity in antimicrobial, anti-obesity, and lipid metabolism research, though typically at levels below EGCG’s potency.
4. Epicatechin (EC)
The simplest of the four major catechins, EC lacks both the gallate group and one hydroxyl group. Concentrations are typically lowest of the four (5–30mg per cup). EC is found abundantly in chocolate and red wine as well as tea, and has a distinct research profile — studied particularly for cardiovascular effects in flavanol research more broadly, including Kuna island population studies linking cocoa flavanols to heart health. In tea specifically, EC contributes less total antioxidant activity than EGCG but has favorable bioavailability.
Non-Epicatechin Isomers
Each of the four epicatechin forms has a corresponding non-epicatechin stereoisomer: catechin gallate (CG), gallocatechin (GC), gallocatechin gallate (GCG), and catechin (C). These are present in smaller quantities in fresh tea; certain processing conditions increase their proportion. They are less well studied but contribute to total polyphenol content.
Catechin Concentrations By Tea Type
| Tea Type | Approximate Total Catechins (per 200ml) | EGCG Proportion |
|---|---|---|
| Matcha (standard portion) | 200–350mg | ~60% |
| Gyokuro (standard brew) | 100–200mg | ~55% |
| Sencha (standard brew) | 60–120mg | ~50% |
| Oolong (light oxidation) | 40–80mg | ~40–45% (partially oxidized) |
| Oolong (heavy oxidation) | 15–40mg | ~25–35% |
| Black tea (standard brew) | 5–20mg as catechins | Low — converted to theaflavins/thearubigins |
| White tea | 30–70mg | ~50% |
Black tea’s catechins are substantially converted during enzymatic oxidation to theaflavins and thearubigins, which have distinct but overlapping health research profiles.
How Processing Changes Catechin Profile
- Green tea (steam or pan-fired): Catechins preserved intact; highest total catechin content
- Oxidation in oolong and black tea: Catechins oxidize into dimers (theaflavins) and polymers (thearubigins); flavor transforms from bitter/astringent to full/thick with distinct taste compounds
- Shading (gyokuro, matcha): Shading reduces total catechins by slowing photosynthetic conversion of theanine to catechins — producing relatively lower catechin but higher theanine content vs sun-grown tea
- Aging/pu-erh: Microbial and chemical processes convert monomeric catechins over time; theabrownins form, astringency decreases, flavor evolves toward earthy complexity
Research
- Khokhar, S., & Magnusdottir, S.G.M. (2002). Total phenol, catechin, and caffeine contents of teas commonly consumed in the United Kingdom. Journal of Agricultural and Food Chemistry, 50(3), 565–570.
Summary: Wide-ranging analysis of catechin types and concentrations across black, green, and herbal teas, providing reference data for how tea type and origin affect individual catechin profiles. - Graham, H.N. (1992). Green tea composition, consumption, and polyphenol chemistry. Preventive Medicine, 21(3), 334–350.
Summary: Foundational overview of green tea catechin structure and concentration data, covering the individual EGCG, EGC, ECG, and EC compounds and their relative proportions in green tea.