Inhibitory effect of phenolic compounds from grape seeds (Vitis vinifera L.) on the activity of angiotensin I converting enzyme

Inhibition of the angiotensin I converting enzyme (ACE) is an important therapeutic approach in the treatment of several cardiovascular disorders. In this study the inhibitory potential of procyanidin-rich fractions of grape seed (Vitis vinifera L.) was evaluated. The inhibitory capacity was assayed by fluorometric determination of the amount of histidyl-leucine released from the substrate utilized in the presence of ACE from rabbit lung. Four purified monomers [(+)-catechin, (-)-epicatechin, (+)-catechin-O-gallate, and (-)-epigallocatechin] were also tested for comparison. Results showed that the natural phenolic extracts exhibit higher inhibitory potential than the monomers, and that fractions with higher average degrees of polymerization (DPn = 8, IC50 = 0.1 mg/L) present lower IC50 than the intermediate ones (DPn = 5, IC50 = 3.5 mg/L). Such findings strengthen the idea that the inhibitor extension, and the number of heterocyclic oxygen and hydroxyl groups in their structures, could define their in vitro action. (C) 2013 Elsevier Ltd. All rights reserved.