Dysiarenone, a Dimeric C₂₁ Meroterpenoid with Inhibition of COX‑2 Expression from the Marine Sponge <i>Dysidea arenaria</i>

Dysiarenone (<b>1</b>), a dimeric C₂₁ meroterpenoid featuring an unprecedented 2-oxaspiro­[bicyclo[3.3.1]­nonane-9,1′-cyclopentane] carbon skeleton, was isolated from the marine sponge <i>Dysidea arenaria</i>. The structure of <b>1</b> was determined by HRMS and NMR spectroscopic analyses coupled with ECD calculations. Dysiarenone showed inhibitory activities against COX-2 expression and the production of prostaglandin E₂ with an IC₅₀ value of 6.4 μM in LPS-stimulated RAW264.7 macrophages