Effects of cocoa extracts on endothelium-dependent relaxation

The aim of this study was to examine the effects of procyanidins derived fr om cocoa on vascular smooth muscle. Two hypotheses were tested: 1) extracts of cocoa, which are rich in procyanidins, cause endothelium-dependent rela xation (EDR), and 2) extracts of cocoa activate endothelial nitric oxide sy nthase (NOS), The experiments were carried out on aortic rings obtained fro m New Zealand White rabbits. The polymeric procyanidins (tetramer through d ecamer of catechin) caused an EDR. In addition, the Ca2+-dependent NOS acti vity, measured by the L-arginine to L-citrulline conversion assay, was sign ificantly increased in aortic endothelial cells exposed to polymeric procya nidins, whereas monomeric compounds had no such effect. These findings demo nstrate that polymeric procyanidins cause an EDR that is mediated by activa tion of NOS.