Abstract Chemical investigations on the cultured octocoral Briareum excavatum have led to the isolation of five new 8,17-epoxybriarane diterpenoids, excavatoids G–K (1–5). The structures of briaranes 1–5 were determined on the basis of spectroscopic methods and the structure of 1 was further confirmed by a single-crystal X-ray diffraction analysis. Cytotoxicity of these metabolites toward various tumor cell lines is described. Excavatoid I (3) was found to show mild inhibitory effects on elastase release and superoxide anion generation by human neutrophils.