What the word covers
Antioxidant is a chemistry word that turned into a marketing word.
In a flask it means a molecule that donates an electron and breaks a chain reaction.
On a packet it means very little, because it carries no dose and no outcome.
Tea is full of molecules that behave that way under glass.
Most of them are polyphenols, and in fresh leaf they run 20 to 35 percent of the dry weight.
The largest slice of that is a group called catechins.
EGCG is the one printed on labels, and it is the biggest single catechin in green tea.
Theanine gets listed beside it, and theanine is not an antioxidant at all.
It is an amino acid, and it is why a cup of tea feels unlike a cup of coffee.
Caffeine is not an antioxidant either, though it turns up in the same tables.
Caffeine sits at 2 to 4 percent of the dry weight, and it is the part drinkers notice.
So a leaf can be rich in these compounds and still do nothing measurable in a person.
Those are two separate claims, and packaging tends to merge them into one.
The gap between them is where the selling happens.
The compounds in tea, and what processing does to them
Processing decides which of these molecules are left in the leaf you buy.
Green tea is heated early, which kills the enzymes and leaves catechins largely intact.
White tea is only withered and dried, so it keeps a similar profile.
Yellow tea adds men huang（闷黄）, a slow damp rest that trims the catechins a little.
Oolong is partly oxidised, and some catechins pair up into bigger molecules.
Red tea, sold as black tea in the West, is oxidised all the way.
Its catechins convert mostly into theaflavins and thearubigins.
Theaflavins give the bright edge, while thearubigins give body and colour.
Dark tea goes further still, with microbes working on the leaf over weeks.
Ripe dark tea is piled for 45 to 60 days, and that is where most of the change happens.
What comes out has a smaller polyphenol count and a different set of compounds.
None of that makes one tea better for you than another.
It makes them different, which is the more honest thing to say.
The table below sets out what each type ends up holding.
| Tea type | Main polyphenols | What processing changed |
|---|---|---|
| White | Catechins, the highest share of EGCG | Withered and dried only; catechins left alone |
| Green | Catechins (EGCG, EGC) | Heat applied early, so the catechins stay intact |
| Yellow | Catechins, slightly reduced | Men huang（闷黄）lets a little slow oxidation through |
| Oolong | Catechins mixed with theaflavins | Partial oxidation; some catechins pair up |
| Red (black) | Theaflavins and thearubigins | Full oxidation converts most of the catechins |
| Dark (pu-erh) | Residual polyphenols plus microbial products | Post-fermentation over weeks or years |
What the test-tube numbers actually measure
Most of the numbers quoted for tea come from assays run in glassware.
ORAC is the best known of them, and the one to distrust most.
The United States Department of Agriculture withdrew its ORAC table in 2012.
It withdrew the table because the figures predicted nothing in a living body.
Tea still scores well in tests like that, and the score still tells you little.
The molecules are measured in conditions no tissue in you ever supplies.
The assay never asks whether the compound reaches the tissue in the first place.
Absorption is usually where the story ends.
A large share of tea catechins passes through the gut unchanged.
What does get absorbed is modified, circulated and cleared within hours.
That is not a failing of tea; it is what happens to most plant compounds.
It does mean a larger figure on a packet is not a larger effect in a drinker.
Anyone quoting one number from one assay is selling something.
What survives into the cup
Brewing is the last filter, and the only one you control.
Catechins move into hot water fast, and most of them leave the leaf in the first minute.
Water at 80 °C for 2 minutes takes plenty out of a green tea.
Boiling water on green tea adds bitterness faster than it adds anything else.
Red tea behaves the other way, and gives up its compounds more slowly.
Hotter water and a longer steep help there, up to the point where it turns harsh.
A second infusion still carries a good share of what the leaf holds.
Throwing leaf away after one cup wastes most of what you paid for.
Milk is the old argument, and the trials still disagree on it.
The difference lands small whichever way the next trial reports.
Lemon is the addition with a clear mechanism, since vitamin C keeps catechins stable.
Brew it the way you enjoy it, and treat the chemistry as context.
Tea is a good drink with interesting chemistry, and that is enough.