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 mu g/mL, respectively) and 2 exhibited moderate cytotoxicity toward the leukemia MOLT-4 cells (IC50 = 18.8 mu g/mL).