Free flavan-3-ol aglycone (2R,3S stereochemistry) — the (+)-enantiomer. Minor component of most flavan-3-ol sources compared with its stereoisomer (−)-epicatechin. Absorbed at the small-intestine enterocyte and extensively glucuronidated / sulfated / methylated (via COMT) before entering portal circulation; free catechin in plasma is <3% of total SRC conjugates. Carbohydrate co-ingestion boosts AUC ~2× (Schramm 2003); dairy protein reduces it. Shares antioxidant, mild eNOS-upregulating, and anti-inflammatory effects with epicatechin.
Half-Life (t½)
PO: 2h
Dosing Guidelines
PO: Typical 300 mg (Range: 200–500 mg)
Target Organ Systems
digestive
immune-hematologic
Interactions
Epicatechin (synergistic): Stereoisomer; co-occur in most flavanol sources. Epicatechin is the more abundant isomer in cocoa.
EGCG (synergistic): Co-occur in tea; EGCG is the gallate-esterified, more bioactive form.