The Effect of Quercus salicina Leaf Extracts on Vascular Endothelial Function: Role of Nitric Oxide

Dysfunction of the vascular endothelium is reported as a hallmark of cardiovascular diseases. Many evidences suggest that polyphenols are associated with a decreased global mortality and might be involved in protection against cardiovascular risk. This beneficial effect of polyphenol may be due to many actions as antioxidant that increases bioavailability of nitric oxide, vasodilation or antihypertensive properties. To identify new natural medicine candidate for cardiovascular protection, plant extracts used in traditional medicine were evaluated by vascular reactivity system. Porcine coronary artery rings were suspended in organ chambers for the measurement of changes in isometric tension. Screening results indicated that the ethanolic extract of leaf from Quercus salicina (QSE) has been found to exhibit potent vasorelaxant activity. QSE dose-dependently induced endothelium-dependent relaxations, which were abolished by inhibitors of nitric oxide synthase (N-omega-nitro-L-arginine). In addition, QSE strongly and dose-dependently activate endothelial nitric oxide synthase (eNOS) in porcine coronary artery endothelial cell. Taken together, the present study has demonstrated that QSE is a powerful endothelium-dependent vasodilator and that this effect involves increased nitric oxide bioavailability. In conclusion, QSE could be a cardiovascular protective herbal medicine candidate associated with cardiovascular diseases and endothelial dysfunction.