Antitumor-promoting effects of new sesquiterpenes from Crossopetalum tonduzii.

Seven new sesquiterpenes (1-7) with a 'dihydro-beta-agarofuran' (= 5,11-epoxy-5beta,10alpha-eudesmane) skeleton were isolated from Crossopetalum tonduzii. Their structures were elucidated spectroscopically, especially by means of homo- and heteronuclear NMR correlation (COSY, ROESY, HSQC, and HMBC). The absolute configurations of the new compounds were determined by circular dichroism (CD) studies and by chemical correlations via the derivatives 8-11. The new compounds showed moderate antitumor-promoting effects with respect to the activation of the Epstein-Barr virus early antigen (EBV-EA).