Relationship between rate and extent of catechin absorption and plasma antioxidant status

Flavonoids are described to exert a large array of biological activities, w hich are mostly ascribed to their radical-scavenging, metal chelating and e nzyme modulation ability. Most of these evidences have been obtained by in vitro studies on individual compounds and at doses largely exceeding those dietary. Little is known about a possible relationship between rate and ext ent of the absorption and modifications of plasma antioxidants. To elucidat e this aspect, human volunteers were supplemented with single doses of gree n tea catechins in free (Greenselect(TM)) or phospholipid complex form (Gre enselect(TM) Phytosome(R)) equivalent to 400 mg epigallocatechingallate (EG Cg). EGCg was chosen as biomarker for green tea catechin absorption, and it s time course plasma concentration was correlated to the subsequent percent variations of plasma ascorbate, total glutathione, a-tocopherol, p-caroten e and Total Radical Antioxidant Parameter (TRAP). Green tea catechins were absorbed more extensively when administered as phospholipid complex rather than as free catechins. Single dose intake of both forms of catechins produ ced a transient decrease (10-20%) of plasma ascorbate and total glutathione and an increase of plasma TRAP (16-19%). These variations were consistent with the plasmatic levels of EGCg, ascorbate and total glutathione.