Two norcembranoidal diterpenes, 5-episinuleptolide acetate (1) and scabrolide D (2), were isolated from a Formosan octocoral identified as Sinularia sp. The structures of norcembranoids 1 and 2 were established by spectroscopic methods and by comparison of the spectral data with those of known analogues and 1 was proven to be a new natural product. Norcembranoid 1 was found to exhibit cytotoxicity toward a panel of tumor cells.

A new halimane-type diterpenoid, echinohalimane A (1), was isolated from a gorgonian, identified as Echinomuricea sp. The structure of 1 was determined by spectroscopic methods and this compound was found to exhibit cytotoxicity toward various tumor cells and display an inhibitory effect on the release of elastase by human neutrophils. Echinohalimane A (1) is the first halimane analogue from the marine organisms belonging to phylum Cnidaria.

5-Episinuleptolide acetate (5EPA), a cytotoxic norcembranoidal diterpene recently identified from the Formosan soft coral Sinularia sp., exhibited potent activity against the K562, Molt 4 and HL 60 cancer cell lines. The antiproliferative assay, as well as the annexin V-FITC/propidium iodide (PI) apoptotic assay, indicated that the HL 60 cell line is the most sensitive one towards 5EPA. This diterpenoid led to caspases -3, -8, and -9 activation as well as PARP cleavage. It also induced ROS generation, calcium accumulation and disruption of mitochondrial membrane potential. Additionally, the expression levels of Hsp90 protein and several client proteins were downregulated in OPEN ACCESSMolecules 2013, 18 2925 response to 5EPA treatment. These results suggest that 5EPA's cytotoxic effect on HL 60 cells may be attributed to the inhibition of Hsp90 as well as the induction of mitochondrial stress which finally results in apoptotic cell death.

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Two new 6-hydroxyeunicellin diterpenoids, cladieunicellin G (1) and 6-epi-cladieunicellin F (2), were isolated from an Indonesian octocoral Cladiella sp. The structures of eunicellins 1 and 2 were established by spectroscopic methods and 2 was found to be an epimer of the known eunicellin cladieunicellin F (3). Eunicellin 2 displayed inhibitory effects on the generation of superoxide anion and the release of elastase by human neutrophils.

Abstract:A new sterol, (22R,23R,24R)-5α,8α-epidioxy-22,23-methylene-24-methylcholest-6,9(11)-dien-3β-ol (1), and two known sterols, (22R,23R,24R)-5α,8α-epidioxy- OPEN ACCESSMolecules 2013, 18 2896 22,23-methylene-24-methylcholest-6-en-3β-ol (2) and 24-methylenecholestane-1α,3β,5α, 6β,11α-pentol (3), were isolated from the soft coral Sinularia gaweli. The structure of sterol 1 was established by spectroscopic methods and by comparison of the spectral data with those of known analogues. The cytotoxicity of sterols 1-3 towards various tumor cells is reported.