Studies on the inhibitory effect of Graptopetalum paraguayense E.!Walther extracts on the angiotensin converting enzyme

This study was aimed at evaluating the kinetic properties and capacities of water (GWE), 50% ethanolic (GE50) and 95% ethanolic (GE95) extracts from Graptopetalum paraguayense for the potential to inhibit angiotensin converting enzyme (ACE). The results showed that GWE, GE50 and GE95 showed potent inhibitory effects on ACE. It was found that the ACE inhibitory activities of all the tested extracts increased with the increase of their concentrations. In addition, the ACE inhibition of the tested extracts of G. paraguayense were significantly reduced after the addition of 1.5 mM ZnCl2, suggesting the inhibitory action of the extracts may have resulted from the chelation of the ACE zinc cofactor. The inhibition kinetics, analyzed by Lineweaver-Burk plots, revealed that G. paraguayense extracts showed a mixed-type inhibition. A comparison of the 50% inhibition concentration (IC50) and K-i values showed that the ethanolic extracts, including GE50 and GE95 exhibited the more effective ACE inhibitory activity than the water extracts of G. paraguayense. (c) 2005 Elsevier Ltd. All rights reserved.