Evaluation of the NO scavenging activity of procyanidin in grape seed by use of the TMA-PTIO/NOC 7 ESR system.

The nitrogen monoxide (NO) scavenging activity of grape seed extract (GSE) was studied in the TMA-PTIO/NOC 7 system. The procyanidin-rich (>95%) GSE showed strong NO scavenging activity in the system. The activity was found to depend on the condensation rate of cyanidin when synthetic oligomers were tested. Investigation of the NO scavenging activities of other polyphenols (catechin, epicatechin, epigallocatechin, and epigallocatechin gallate) in the TMA-PTIO/NOC 7 system revealed that gallocatechin, epigallocatechin, and epigallocatechin gallate exhibited strong activities. From the results, it was suggested that the high condensation rate of and the gallate ester moiety in procyanidin in GSE may play an important role in the NO scavenging activity. The mechanism of the NO scavenging activity of phenolic compounds such as GSE is speculated to be as follows: NO reacts with phenolic compounds directly to generate phenoxy radicals.