Briarenols C-E, new polyoxygenated briaranes from the octocoral briareum excavatum

Abstract

Three new polyoxygenated briarane diterpenoids, briarenols C-E (1-3), were isolated from the octocoral Briareum excavatum. The structures of briaranes 1-3 were elucidated by interpretation of spectroscopic data, and the methylenecyclohexane ring in 1 was found to exist in a twisted boat conformation. Briarenol D (2) displayed an inhibitory effect on the release of elastase by human neutrophils with an IC50 value of 4.65 μM. Briarenol E (3) was found to inhibit the protein expression of pro-inflammatory inducible nitric oxide synthase (iNOS) in a murine macrophage-like cell line, RAW 264.7, stimulated with lipopolysaccharides (LPS).