Few botanical categories are quoted as loosely as tea polyphenols. A buyer sees “polyphenols 98%” on one sheet and “EGCG 50%” on another and assumes the second is weaker. It is not — the two numbers describe different things, and the gap between them is measurable in grams per mole. Getting that straight is the whole of Tea Polyphenol procurement discipline.
The catechin ladder, in molecular weights
Catechin, the parent flavan-3-ol, is CAS 154-23-4, C15H14O6, 290.27 g/mol, CID 9064, XLogP 0.4. Add one hydroxyl and you have epigallocatechin: CAS 970-74-1, C15H14O7, 306.27 g/mol, CID 72277, XLogP 0.0. The increment is a single oxygen at 16.00 g/mol, and it shows up exactly as expected.
Gallate esterification is the bigger step. Epigallocatechin gallate — EGCG — is CAS 989-51-5, C22H18O11, 458.4 g/mol, CID 65064, XLogP 1.2. Compared with epigallocatechin at 306.27 g/mol, that is +152.13 g/mol, which is a galloyl group (C7H4O4, 152.11 g/mol) less the hydrogen displaced at the ester oxygen. Epicatechin gallate sits just below at C22H18O10, 442.4 g/mol, CID 107905, XLogP 1.5, exactly 16.00 g/mol lighter — one fewer hydroxyl.
Full assay reference
| Compound | CAS | Formula | MW (g/mol) | CID | XLogP |
|---|---|---|---|---|---|
| Catechin | 154-23-4 | C15H14O6 | 290.27 | 9064 | 0.4 |
| Epigallocatechin (EGC) | 970-74-1 | C15H14O7 | 306.27 | 72277 | 0.0 |
| Epicatechin gallate (ECG) | 1257-08-5 | C22H18O10 | 442.4 | 107905 | 1.5 |
| Epigallocatechin gallate (EGCG) | 989-51-5 | C22H18O11 | 458.4 | 65064 | 1.2 |
| Gallic acid | 149-91-7 | C7H6O5 | 170.12 | 370 | 0.7 |
| Caffeine | 58-08-2 | C8H10N4O2 | 194.19 | 2519 | -0.1 |
Why the two headline percentages are not comparable
| Claim | What it measures | Mass basis |
|---|---|---|
| Total polyphenols | All phenolics by colorimetric assay | Usually gallic acid, 170.12 g/mol |
| Total catechins | Sum of individual catechins by HPLC | 290.27 to 458.4 g/mol range |
| EGCG content | Single peak | 458.4 g/mol |
| Caffeine content | Single peak | 194.19 g/mol |
A colorimetric total-polyphenol figure calibrated against gallic acid at 170.12 g/mol will systematically overstate a material whose dominant species is EGCG at 458.4 g/mol, because the response factor per gram is not the same. That is not fraud — it is a method artefact, and it is why HPLC speciation is worth paying for.
Procurement checklist
- Insist on the calibration standard. Gallic acid at 170.12 g/mol and EGCG at 458.4 g/mol produce different numbers from the same sample.
- Ask for the caffeine figure separately. At 194.19 g/mol it is easy to resolve and it tells you how far the material has been decaffeinated.
- Check the ECG-to-EGCG ratio. The 16.00 g/mol spacing means the two co-elute only on poor columns; a clean chromatogram is a quality signal in itself.
- Request batch-specific data. Assay, moisture, particle size, packaging and shelf life belong on the COA.
Frequently asked questions
Is 98% polyphenols better than 50% EGCG?
Neither is inherently better. The first is a colorimetric total and the second is a single-compound HPLC result. Compare like with like or you will overpay.
Why does EGCG weigh more than EGC?
A galloyl ester group: 306.27 g/mol plus 152.13 g/mol gives 458.4 g/mol.
Should caffeine be zero?
Not necessarily. Caffeine at 194.19 g/mol is a legitimate co-extractive; specify the target level rather than assuming removal.
Facts in this article are taken from PubChem (US National Library of Medicine) records for CIDs 9064, 72277, 107905, 65064, 370 and 2519. Grade-specific data is issued per batch on the COA and is not published here.