title: Inhibitory effects of condensed tannins on angiotensin converting enzyme.
abstract: Effects of condensed tannins isolated from Rhei Rhizoma on the activities of angiotensin converting enzyme (ACE) and various proteases were examined in vitro. Among the various condensed tannins tested, procyanidin B-5 3,3'-di-O-gallate and procyanidin C-1 3,3',3"-tri-O-gallate strongly inhibited the activity of ACE. The concentration of procyanidin B-5 3,3'-di-O-gallate required for 50% inhibition of ACE was 1.3 X 10(-6) M. The inhibition of ACE by condensed tannins was reversible and non-competitive, according to dialysis and to Dixon plots. However, over one hundred times the concentration was required to inhibit activities of other proteases such as trypsin, chymotrypsin, leucine aminopeptidase, carboxypeptidase A and urinary kallikrein. These results suggest that the inhibitory effects of condensed tannins on the activities of ACE are specific.
mesh_terms: D000806:Angiotensin-Converting Enzyme Inhibitors; D000818:Animals; D044946:Biflavonoids; D002392:Catechin; D002417:Cattle; D003956:Dialysis; D007700:Kinetics; D044945:Proanthocyanidins; D013552:Swine; D013634:Tannins / Q000494:pharmacology*
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D044946:Biflavonoids; D044945:Proanthocyanidins; D013634:Tannins; C479578:procyanidin B; C479583:procyanidin C; D002392:Catechin