Biol. Pharm. Bull. 29(2) 365—370 (2006)

bidity and mortality throughout the world, has been associated with a variety of biomedical and psychological factors. In Western populations, CAD and myocardial ischemia are the most common causes of heart failure, which occurs when the heart fails to pump blood at a rate needed to meet metabolic requirements under normal cardiac filling pressure. Patients who survive myocardial infarction resulting from CAD have an approximately 3-fold increased risk of developing left ventricular systolic dysfunction (systolic ejection fraction 45%) thereafter. However, our understanding of CAD pathophysiology has undergone a remarkable evolution over the past decade, and the likelihood of survival from myocardial infarction has almost doubled in some countries. Ginseng, a widely recognized herbal medicine, has been used extensively in Korean, Japanese, and Chinese medicine, and has become increasingly popular in the Western world for its alleged tonic effects and possible curative and restorative properties. Accumulating clinical evidence supports the potential benefits of ginseng roots in the cardiovascular system. For example, administration of ginsenosides, the active ingredients extracted from Panax ginseng, has been shown to decrease blood pressure in both hypertensive patients and experimental animals. The anti-hypertensive effects of ginsenosides may be at least partially due to their ability to inhibit vascular tone. Indeed, ginsenosides have been shown to concentration-dependently relax the prostaglandin F2a-induced contraction of isolated rabbit pulmonary arteries and the phenylephrine-induced contraction of isolated rabbit and rat aortas. Studies examining the effect of various purified ginsenosides on vascular contractions have demonstrated that ginsenoside Rg3, which is one of the protopanaxadiol ginsenosides, acts as the most potent vasodilator among ginsenosides. Ginsenoside Rg3 exists as a pair of stereoisomers, with a change in the position of the hydroxyl group on carbon-20 differentiating between the epimers, 20(R)-ginsenoside and 20(S )-ginsenoside (Fig. 1). Although we previously reported that 20(R)and 20(S )-ginsenoside Rg3 regulate voltage-dependent ion channel activities in a stereospecific manner, no previous work has examined the effects of these epimers on vasorelaxation. Here, we investigated the relaxation effects of 20(S )and 20(R)-ginsenoside Rg3 on high K and 5-HT-induced contraction of swine coronary arteries with intactor endothelium-denuded artery rings. Our results revealed that 20(S )and 20(R)-ginsenoside Rg3 exhibit differential relaxation effects in swine coronary arteries.