Rhabdastrellosides A and B: Two New Isomalabaricane Glycosides from the Marine Sponge , and Their Cytotoxic and Cytoprotective Effects.

Investigation of the Vietnamese marine sponge led to the isolation of two new polar isomalabaricanes: rhabdastrellosides A () and B (). Their structures and stereochemistry were elucidated with the application of 1D and 2D NMR, HRESIMS, and HRESIMS/MS methods, as well as chemical modifications and GC-MS analysis. Metabolites and are the first isomalabaricanes with non-oxidized cyclopentane ring in the tricyclic core system. Moreover, having a 3-O-disaccharide moiety in their structures, they increase a very rare group of isomalabaricane glycosides. We report here a weak cytotoxicity of and toward human neuroblastoma SH-SY5Y cells and normal rat H9c2 cardiomyocytes, as well as the cytoprotective activity of rhabdastrelloside B () at 1 µM evaluated using CoCl-treated SH-SY5Y and H9c2 cells.