Assessment of the vasodilator effect of “24-hydroxymethyl-23,26,27-trihydroxy-cucurbit-5-ene-3-yl-acetate” (NC36) isolated from Sechium edule (Jacq.) Swartz (Cucurbitaceae) fruits

Our previous studies have demonstrated that the hydroalcoholic extract of Sechium elude fruits exerts significant antihypertensive and vasodilatory effects. The present study was undertaken to elucidate the mechanism underlying the vasorelaxant activity of NC36 (cucurbitane-type triterpenoid) isolated from this extract. Experiments were performed on isolated aortic rings precontracted with norepinephrine. The results showed that NC36 induced complete (100 %) relaxation in isolated aorta with intact endothelium, whereas no significant relaxation was observed in endothelium-denuded preparations, indicating that the vasodilatory effect of NC36 is endothelium-dependent. Pre-incubation of the aortic rings with indomethacin at the concentrations of 10^⁻7, 10^⁻6 and 10^⁻5 M induced a significant rightward shift of the concentration–response curves and an increase in NC36 EC₅₀ values (p < 0.05), indicating the participation of cyclooxygenase-derived metabolites. These findings suggest that NC36 induces endothelium-dependent vasorelaxation, at least in part, through the prostacyclin pathway and most probably NO release.