Absolute stereostructure of carabrane-type sesquiterpene and vasorelaxant-active sesquiterpenes from Zedoariae Rhizoma

The aqueous acetone extract of Zedoariae Rhizoma was found to show inhibito ry effects on contractions induced by high concentrations of potassium cati on (K+) in isolated rat aortic strips. From the extract, two new carabrane- type sesquiterpenes, curcarabranols A and B, were isolated together with a few carabrane-type sesquiterpenes, such as curcumenone and 4S-dihydrocurcum enone. Their absolute stereostructures were determined on the basis of chem ical and physicochemical evidence, which included the application of the mo dified Mosher's method and chemical conversion from curcumenone to curcarab ranols A and B. In addition, several sesquiterpenes and diaryl-heptanoids ( e.g. germacrone, glechomanolide, isocurucmenol, beta -eudesmol, and beta -d ictyopterol) showed potent inhibitory effects on contractions induced by hi gh concentrations of K+ in isolated rat aortic strips (inhibition > 80% at 100 muM), while they did not inhibit norepinephrine-induced contractions, s o that the vasorelaxant activities of these sesquiterpenes were presumed to be dependent on their calcium channel-blocking activity. (C) 2001 Elsevier Science Ltd. AE rights reserved.