Briarenols F–H: New polyoxygenated briarane diterpenoids produced by the octocoral Briareum excavatum

[Display omitted] •New briaranes, briarenols F–H (2–4), were obtained from octocoral B. excavatum.•Absolute configuration of excavatolide C (1) was determined by X-ray analysis.•Excavatolide C (1) showed inhibition effect on iNOS release from RAW 264.7. Two known briarane diterpenoids, excavatolide C (1) and briacavatolide C (5), along with three new polyoxygenated analogues, briarenols F–H (2–4), have been isolated from the supercritical CO2 extraction of an octocoral identified as Briareum excavatum. The absolute configuration of 1 was determined by a single-crystal X-ray diffraction analysis for the first time and the structures of 2–5 were established by spectroscopic methods. Bioactivity study showed that briaranes 1, 4 and 5 showed inhibition effects on iNOS release from RAW264.7.