Antihypertensive and vasorelaxant effects of water-soluble proanthocyanidins from persimmon leaf tea in spontaneously hypertensive rats.

The antihypertensive and vasorelaxant effects of water-soluble proanthocyanidins, extracted in persimmon leaf tea, were investigated in spontaneously hypertensive rats, rat aortas, and human umbilical vein endothelial cells. Oral administration of proanthocyanidins significantly decreased the systolic blood pressure of the rats after 4 h, as compared with distilled water controls. A vasorelaxant effect on rat aortas was induced by proanthocyanidins, and it was abolished by removal of the endothelium and inhibition of endothelial nitric oxide synthase and soluble guanylyl cyclase activity. The phosphorylation levels of endothelial nitric oxide synthase (Ser-1177) and the upstream kinase Akt (Ser-473) in umbilical cells also increased in a time-dependent manner after the addition of a proanthocyanidin-rich fraction. These results suggest that the antihypertensive effect of proanthocyanidins in persimmon leaf tea is due to vasorelaxation via an endothelium-dependent nitric oxide/cGMP pathway, and that proanthocyanidins might be useful in dietary lowering of blood pressure.