Biol. Pharm. Bull. 30(7) 1278—1283 (2007)

velopment and progression of cerebroand cardiovascular disorders. The pathogenesis of hypertension is accompanied with the increased oxygen free radical production, the decreased nitric oxide bioavailability in the vasculature and reactive oxygen species-mediated cardiovascular remodeling. Hypertensive patients show increased levels of plasma superoxide, hydrogen peroxide and lipid peroxide. In various rodent models of experimental hypertension, including spontaneously hypertensive rats (SHRs) and renal hypertensive rats, enhanced endothelial superoxide anion production leading to impairment of endothelium-dependent relaxation has been demonstrated. The phytomedicine have been extensively used to prevent and heal of various cardiovascular problems for over a millennium in oriental countries. Over the last decade, interest by the general public in the use dietary phytomedicine has risen exponentially, due to its low toxicity and good therapeutically performance. Morus bombycis KOIDZUMI (MK) is widely distributed in Asia and has been used in traditional medicine on account of its apparent anti-inflammatory, antibiotic, antioxidant, and hepatoprotective effects. Moreover, the young branch of mulberry tree (Morus spp.) is generally recognized as herbal medicine used for treatment of hypertension and paralysis of arms and legs in China. Recently, mulberry (Morus alba L.) leaves showed anti-atherosclerotic effects in LDL receptor-deficient mice and a neuroprotection effect against in vivo cerebral ischemia. In addition, Morus alba L. root bark fractions exhibited a potent antioxidant activity via inhibition of lipid peroxidation in cholesterol-fed rats. However, there is little information about the effects of MK extract on pharmacological actions in cardiovascular disease associated with hypertension, particularly, on animal models of systemic hypertension. In the present study, we evaluated the antihypertensive effects of long-term administration with MK extract in SHRs. In addition, we also examined the effects on the vascular responses of isolated rat aorta and the cardiac functions of isolated rat heart.