STRUCTURES AND BIOACTIVITIES OF NEW ASBESTININ DITERPENOIDS FROM THE CARIBBEAN GORGONIAN OCTOCORAL BRIAREUM-ASBESTINUM

Five new diterpenoids representatives from the rare skeletal class asbestinins have been isolated from the Caribbean gorgonian octocoral Briareum asbestinum. The structures of these secondary metabolites, named asbestinin-6 (1), asbestinin-7 (4), asbestinin-8 (5), asbestinin-9 (10) and asbestinin-10 (11), were defined hy chemical and spectroscopic methods. The specimens of B. asbestinum collected in Puerto Rico yielded exclusively diterpenoids possessing the asbestinane carbon skeleton thus suggesting lack of biosynthetic versatility for this gorgonian. Diterpenoids 1, 4, 5, 10 and 11 showed significant cytotoxicity when screened against a panel of five human tumor cell lines.