Green Tea Catechins: Total Polyphenols by Folin-Ciocalteu vs EGCG by HPLC

The Three Numbers

Figure	Method	What it counts	Typical grade value
Total polyphenols	Folin-Ciocalteu colorimetry, read at about 765 nm against gallic acid	Everything that reduces the reagent: catechins, gallic acid, flavonols, some non-phenolics	50% to 98%
Total catechins	HPLC, sum of named catechins	EGCG, EGC, ECG, EC, C, GCG and gallocatechins as resolved	30% to 80%
EGCG	HPLC, single peak against standard	Epigallocatechin gallate only	15% to 90%

Folin-Ciocalteu: Useful, Not Specific

The Folin reagent is reduced by any phenolic hydroxyl and by several non-phenolic reducing substances, so the result is an estimate of total reducing capacity expressed as gallic acid equivalents. It is quick and it tracks overall extract quality, which is why it is the trade’s first number. It cannot tell EGCG from gallic acid or from an added antioxidant, and it is the figure most easily inflated.

HPLC: The Numbers a Formulator Needs

Reversed-phase HPLC with UV detection at about 280 nm resolves the individual catechins and caffeine in one run; validated methods are published for tea leaf, extracts and fermented tea products, and newer sample-preparation approaches shorten the clean-up. The catechin sum and the EGCG figure come from the same chromatogram, as does caffeine, which is why one HPLC report can replace three separate results. Where the specification names EGCG, only HPLC will do.

Why 98% Polyphenols Can Mean 40% EGCG

A highly refined extract can reach 98% total polyphenols while its EGCG sits at 40% to 50%, because the remaining polyphenols are other catechins and gallic acid. Conversely a 90% EGCG material is a purified fraction, not a whole extract, and behaves differently in formulation and safety assessment. The dose guidance in the safety literature is written in EGCG, so the specification should be too; see the green tea dosage guide for the ceilings.

Caffeine and Decaffeination

Caffeine by HPLC belongs on every green tea COA because it changes labelling and safety in most markets. Decaffeinated grades are produced by water or solvent washing; ask for the method and for residual solvent where a solvent was used, and expect some catechin loss in the process.

What to Specify

1. EGCG NLT x% by HPLC, total catechins NLT y% by HPLC, total polyphenols NLT z% by Folin-Ciocalteu, all three on the COA.
2. Caffeine reported by HPLC, with a maximum for decaffeinated grades.
3. Solvent named and residual solvent by GC.
4. Pesticide screen against the destination MRLs, since tea is a heavily treated crop, and heavy metals by ICP-MS with attention to aluminium and fluoride where the buyer’s market asks.