New antimalarial norterpene cyclic peroxides from Xisha Islands sponge Diacarnus megaspinorhabdosa

Seven norterpene cyclic peroxides including four new ones have been isolated from Xisha Islands sponge Diacarnus megaspinorhabdosa in the South China Sea. The structures of the compounds were elucidated on the basis of spectroscopic analyses. All the norterpene cyclic peroxides displayed antimalarial activity against Plasmodium falciparum (D6 and W2 clones) with the IC50 values in the range of 1.6-8.6 μM. Especially, the new compound 3 showed significant antimalarial activity with the IC50 values of 1.6 (W2) and 2.2 (D6) μM.