Briarenols O and P: Novel briaranes from a cultured octocoral Briareum excavatum (Briareidae)

Two new 3,8-cyclized cembranoids, briarenols O (1) and P (2), featuring with briarane carbon skeleton have been isolated from a cultured octocoral Briareum excavatum. The structures of 1 and 2 were established by spectroscopic methods and 1 was found to be a rare 2-ketobriarane. Briarane 1 enhanced the generation of inducible nitric oxide synthase (iNOS) from RAW 264.7 stimulated by lipopolysaccharides (LPS).