Polyphenols

Polyphenols are the chemical foundation of tea's health reputation, flavor complexity, and color. The term encompasses hundreds of individual compounds, with tea's polyphenol profile varying dramatically based on processing. Green tea's polyphenol fraction is dominated by monomeric catechins, especially EGCG. As oxidation progresses through oolong to black tea, these monomers polymerize into increasingly complex structures: theaflavins (dimers), thearubigins (polymers), and other oligomeric compounds still being characterized by researchers. Despite this transformation, total antioxidant capacity remains relatively stable across tea types — the larger molecules simply operate through different mechanisms. Beyond catechins and their derivatives, tea contains flavonols (quercetin, kaempferol, myricetin), phenolic acids, and tannins. Polyphenols are responsible for astringency (the dry, puckering mouthfeel), which diminishes with oxidation as catechins convert to smoother thearubigins. The health research on tea polyphenols spans thousands of studies, with the strongest evidence supporting roles in cardiovascular protection, anti-inflammatory activity, and metabolic health.