Poecillastrosides, Steroidal Saponins from the Mediterranean Deep-Sea Sponge Poecillastra compressa (Bowerbank, 1866).

The first chemical investigation of the Mediterranean deep-sea sponge (Bowerbank, 1866) led to the identification of seven new steroidal saponins named poecillastrosides A-G (-). All saponins feature an oxidized methyl at C-18 into a primary alcohol or a carboxylic acid. While poecillastrosides A-D (-) all contain an double bond at C-24 of the side-chain and two osidic residues connected at O-2', poecillastrosides E-G (-) are characterized by a cyclopropane on the side-chain and a connection at O-3' between both sugar units. The chemical structures were elucidated through extensive spectroscopic analysis (High-Resolution Mass Spectrometry (HRESIMS), 1D and 2D NMR) and the absolute configurations of the sugar residues were assigned after acidic hydrolysis and cysteine derivatization followed by LC-HRMS analyses. Poecillastrosides D and E, bearing a carboxylic acid at C-18, were shown to exhibit antifungal activity against .