Abstract: The cellular accumulation of individual catechins was measured as an index of intestinal absorption to clarify the interactions among catechins. The cellular accumulation of (−)-epicatechin (EC) increased in the presence of other catechins. The ability of gallate catechin such as (−)-epigallocatechin gallate (EGCG) and (−)-epicatechin gallate (ECG) to increase the cellular accumulation of EC was greater than that of nongallate catechins. Gallic acid octyl ester (GAO) also increased the cellular accumulation of EC by 426% as compared with that in untreated cells. Conversely, the cellular accumulation of ECG was not influenced by other catechins, but it increased by 54% in the presence of GAO. Experiments using GAO derivatives indicated that the gallate moiety required the presence of a catechol group and a neighboring carbonyl group, whereas the pyrogallol moiety, without a neighboring carbonyl group, required 3 hydroxyl groups to increase the cellular accumulation of EC. Furthermore, gallate esters required long carbon chains to increase the same. The experiment using EGCG, GAO, or their derivatives indicated that the ability of gallate or pyrogallol moiety to increase the cellular accumulation of EC was restricted by their hydrophobicity. These results suggest that the co-administration of foods containing functional materials such as gallate or pyrogallol moieties, increases the intestinal absorption of catechin.
Practical Application: The cellular accumulation of (−)-epicatechin increased by the gallate or pyrogallol moiety in catechin structure. The interaction among catechins appeared to affect intestinal absorption of catechin. The bioavailability of catechin may be improved by co-administration of functional foods.