Absolute Stereostructures of Carabrane-Type Sesquiterpenes, Curcumenone, 4S-Dihydrocurcumenone, and Curcarabranols A and B : Vasorelaxant Activity of Zedoary Sesquiterpenes

New carabrane-type sesquiterpenes, curcarabranols A and B, were isolated from zedoary together with the two known carabrane-type sesquiterpenes curcumenone and 4S-dihydrocurcumenone. The absolute stereostructures of these carabrane-type sesquiterpenes were determined on the basis of physicochemical and chemical evidence. Zedoary sesquiterpenes including 4S-dihydrocurcumenone and curcarabranols A and B were found to inhibit the contraction induced by a high concentration of K + in isolated rat aortic strips.