Comparative Evaluation of Vasorelaxant and Antiplatelet Activity of Two Plant-Derived Benzoquinones: Rapanone and Embelin

Vasorelaxant and antiplatelet agents play an important role in preventing and combating endothelial dysfunction, atherosclerosis and a plethora of associated cardiovascular diseases (CVDs). CVDs are the leading cause of death worldwide and nowadays occur not only in developed but also in developing societies. They include, among others, coronary heart disease, cerebrovascular disease and peripheral artery disease. Due to their high prevalence, it is important to seek efficient preventive measures, such as lifestyle changes and the implementation of appropriate herbal dietary supplementation and treatment alternatives. Plant-derived quinones have recently drawn researchers' attention due to their interesting biological potential. Embelin and rapanone are two plant-derived benzoquinones with anti-inflammatory and antioxidant properties. Embelin has already been shown to have vasorelaxant and antiplatelet activity, but little is known about rapanone in the context of CVDs. Therefore, we decided to comparatively evaluate their activity in a specially designed experimental protocol. Following the isolation of both benzoquinones from plant sources (rapanone from <i>Ardisia crenata</i> leaves; embelin from <i>Lysimachia punctata</i> roots), their effects were comparatively assessed in a biofunctional study on isolated rat aorta (precontracted with phenylephrine) and in vitro on platelet aggregation. Both benzoquinones showed 50% vasorelaxation in an NO-dependent manner. Interestingly, rapanone was slightly more effective as an antiplatelet agent than embelin. The antiplatelet effect of both benzoquinones was specific, as no cytotoxicity towards platelets was observed at the concentrations tested. This is the first report on the vasorelaxant and antiplatelet activity of rapanone.