Oroxylin A can induce the relaxation of the aorta ring in endothelium-dependent manner. Nitric oxide may be involved in the endothelium-dependent effect of oroxylin A.
1) These compounds might contribute to the anti-hypertensive effect collectively. However, the anti-hypertensive effect of Eucommia ulmoides OLIV. bark remains largely unclear.Pharmacological studies have revealed that Eucommia ulmoides OLIV. bark extract induce endothelium and NO-cyclic guanosine monophosphate (cGMP) dependent relaxation in the rat thoracic aorta.2) Another report demonstrated that the endothelium-dependent vascular relaxation induced by the bark extract is mediated by NO and endothelium-derived hyperpolarizing factor in small vessels.3) However, the vasorelaxing components have been unclear. Recently, we found oroxylin A and wogonin isolated from Eucommia ulmoides OLIV. bark could significantly lower the perfusion pressure.4) In the previous study, we had reported that oroxylin A could relax rat thoracic aorta and it was endothelium and NO dependent.5)The present study was undertaken to investigate vasodilatory effect of wogonin and its mechanism.Wogonin ( Fig. 1) is a flavone and has a variety of cardiovascular protective effect. It could regulate migration, proliferation and apoptosis of vascular smooth muscle cells. [6][7][8] Besides, wogonin could inhibit angiogenesis, suppress collagen deposition in cardiac fibroblasts and inhibit ischemic brain injury. [9][10][11][12] There is no evidence for vascular relaxation effect of wogonin. We describe here that wogonin, unlike oroxylin A, is an endothelium-and NO-independent vasodilatory flavonoid. One report demonstrated that wogonin offered a wide margin of safety.13) It has therapeutic potential for the treatment of cardiovascular and cerebrovascular diseases.
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