The processes of absorption, blood transport, tissular distribution, metabolism, and excretion are at present understood very little. The aim of this study was to investigate blood transport and identify which principal plasma proteins in humans and rats bind to monomeric catechin and procyanidins in red wine ex vivo. Human and rat plasma and serum were incubated with (+)-catechin and procyanidins from grape seed, the origin of red wine catechins. Proteins were separated by SDS-PAGE and native-PAGE to determine which proteins bound to these compounds. The principal protein that bound to (+)-catechin in each species was sequenced. SDS-PAGE showed that (+)-catechin and procyanidins mainly bound to a protein of about 80 kDa in rats and 35 kDa in humans. Their sequencing indicated that these proteins were apo A-I in humans and transferrin in rats. The fact that red wine procyanidins bind to both proteins suggests that they may have a role in reverse cholesterol transport and in the oxidizing action of iron.