Endothelium-dependent vasorelaxation caused by various plant extracts.

In a previous study (Am J Physiol 1993;265: H774-8), we found that certain red wines and other grape products caused endothelium-dependent vasorelaxation. In the present study, aqueous extracts of a variety of vegetables, fruits, teas, nuts, herbs, and spices were tested for their endothelium-dependent relaxing ability in vitro. Rings of rat aorta, with or without an intact endothelium, were mounted in tissue baths, contracted with phenylephrine, and then exposed to diluted plant extracts. Many, but not all, extracts exhibited endothelium-dependent relaxations that were reversed by NG-monomethyl-L-arginine, a nitric oxide synthase inhibitor, which suggested involvement of nitric oxide, the endothelium-derived relaxing factor in the response. Furthermore, extracts that caused relaxation also increased tissue levels of cyclic GMP, the mediator of nitric oxide-induced vascular smooth-muscle relaxation. These results may lend further support to mounting evidence that plant foods contain compounds that, if absorbed intact and in sufficient quantities, could conceivably be beneficial in prevention of cardiovascular disease.