In Vitro Inhibition of [3H]-Angiotensin II Binding on the Human AT1 Receptor by Proanthocyanidins from Guazuma ulmifolia Bark

Abstract A bioassay-guided fractionation of the 70 % acetone extract of the bark of GUAZUMA ULMIFOLIA Lam. on the inhibition of angiotensin II binding to the AT 1 receptor led to the isolation and identification of bioactive oligomeric and polymeric proanthocyanidins consisting mainly of (-)-epicatechin units. The displacement of [ 3 H]-angiotensin II binding was dose-dependent and correlated with the degree of polymerization of the different fractions containing proanthocyanidins. A strong displacement was seen for the residual fraction suggesting that the most active substances corresponding to the highly polymerized proanthocyanidins. Angiotensin II AT 1 receptor binding might be considered as a potentially interesting biological activity of proanthocyanidins contributing to the very broad spectrum of biological activities of the condensed tannins.