New bioactive Δ11(17)-furanoeunicellins from an octocoral Cladiella sp

A new eunicellin diterpenoid, cladieunicellin U (1), along with a new natural eunicellin, cladieunicellin V (2), and two known analogues, sclerophytins A (3) and B (4), were obtained from an octocoral identified as Cladiella sp. The structures, including the absolute configurations, of eunicellins 1–4 were elucidated by using spectroscopic methods and compared with the spectroscopic and physical data reported in the literature. Eunicellins 1, 3 and 4 decreased the release of elastase, while eunicellins 2 and 4 showed inhibitory effects in terms of the generation of superoxide anions by human neutrophils. Eunicellins 1 and 4 were found to show moderate cytotoxicity toward the leukemia K562 cells (IC50 = 12.8, 11.4 μg/mL, respectively) and 2 exhibited moderate cytotoxicity toward the leukemia MOLT-4 cells (IC50 = 18.8 μg/mL).