Triterpene Glycosides from the Sea Cucumber Cladolabes schmeltzii. II. Structure and Biological Action of Cladolosides A1-A6

Abstract

Six new triterpene glycosides, cladolosides A1–A6(1–6), have been isolated from the Vietnamese sea cucumber Cladolabes schmeltzii (Cladolabinae, Sclerodactylidae, Dendrochirotida). Structures of the glycosides were elucidated by 2D NMR spectroscopy and MS. All the glycosides have nonsulfated tetrasaccharide linear carbohydrate moieties. Glycoside 6 has a glucose residue as the third monosaccharide unit, while the rest of the compounds comprise a xylose in this postion of the carbohydrate chain. Glycosides 1–6 differ from each other in the structures of their holostane aglycones. Cytotoxic activities of glycosides 1–6 were studied against mouse spleenocytes, along with hemolytic activities against mouse erythrocytes. All the compounds, except cladoloside A5(5) posessing a hydroxy-group in the aglycone side chain, demonstrated rather strong cytotoxic and hemolytic effects. The most active glycosides were cladolosides A1(1) and A2(2) having two O-acetic groups and the xylose residue in the third position of the sugar chain.