Kurilosides A, A, C, D, E and F-Triterpene Glycosides from the Far Eastern Sea Cucumber (Levin): Structures with Unusual Non-Holostane Aglycones and Cytotoxicities.

Six new monosulfated triterpene tetra-, penta- and hexaosides, namely, the kurilosides A (), A (), C (), D (), E () and F (), as well as the known earlier kuriloside A (), having unusual non-holostane aglycones without lactone, have been isolated from the sea cucumber (Levin) (Cucumariidae, Dendrochirotida) collected in the Sea of Okhotsk near Onekotan Island from a depth of 100 m. Structures of the glycosides were established by 2D NMR spectroscopy and HR-ESI mass spectrometry. Kurilosides of the groups A and E contain carbohydrate moieties with a rare architecture (a pentasaccharide branched by C(4) Xyl1), differing from each other in the second monosaccharide residue (quinovose or glucose, correspondingly); kurilosides of the group C are characterized by a unique tetrasaccharide branched by a C(4) Xyl1 sugar chain; and kurilosides of the groups D and F are hexaosides differing from each other in the presence of an -methyl group in the fourth (terminal) sugar unit. All these glycosides contain a sulfate group at C-6 of the glucose residue attached to C-4 Xyl1 and the non-holostane aglycones have a 9(11) double bond and lack γ-lactone. The cytotoxic activities of compounds - against mouse neuroblastoma Neuro 2a, normal epithelial JB-6 cells and erythrocytes were studied. Kuriloside A () was the most active compound in the series, demonstrating strong cytotoxicity against the erythrocytes and JB-6 cells and a moderate effect against Neuro 2a cells.