The influence of polymerisation (number of subunits), galloylation (content of esterified gallates) and type of subunit in the polymeric chain of proanthocyanidins (PAs) in skin and seed extracts of Vitis vinifera L cv. Pais on the inhibition of angiotensin I-converting enzyme (ACE) was evaluated. Gel permeation chromatography was used to purify the extracts, which were characterised by acid-catalysis depolymerisation followed by HPLC. ACE activity was tested by quantitative HPLC, measuring the hippuric acid (HA) produced from hippuryl-L-histidyl-L-leucine (HHL) hydrolysis by ACE. The inhibitory activity on ACE was verified for all the obtained fractions, although the PAs' molecular size and structural composition affected the ACE inhibition. The higher inhibitory power of skin extract was associated with greater OH availability, higher mean degree of polymerisation (mDP) and the presence of epicatechin-gallate (ECG) expressed as percentage of galloylation (%G). However, comparing only the structural composition (for samples with similar mDP), % epicatechin (EC) and ECG, <3 %G appeared to be the most important characteristic when considering inhibitory effect of both tissues. Thus, these results indicate that the ACE inhibition by grape PAs depend on the stereochemical configuration of the studied flavanols. (C) 2012 Elsevier Ltd. All rights reserved.