| Summary: | Ten new di-, tri- and tetrasulfated triterpene glycosides, psolusosides B<sub>1</sub> (<b>1</b>), B<sub>2</sub> (<b>2</b>), J (<b>3</b>), K (<b>4</b>), L (<b>5</b>), M (<b>6</b>), N (<b>7</b>), O (<b>8</b>), P (<b>9</b>), and Q (<b>10</b>), were isolated from the sea cucumber <i>Psolus fabricii </i>collected in the Sea of Okhotsk near the Kurile Islands. Structures of these glycosides were established by two-dimensional (2D) NMR spectroscopy and HR-ESI mass-spectrometry. It is particularly interesting that highly polar compounds <b>9</b> and <b>10</b> contain four sulfate groups in their carbohydrate moieties, including two sulfates in the same terminal glucose residue. Glycoside <b>2</b> has an unusual non-holostane aglycone with 18(16)-lactone and a unique 7,8-epoxy fragment. Cytotoxic activities of compounds <b>1</b>−<b>10</b> against several mouse cell lines such as Ehrlich ascites carcinoma cells, neuroblastoma Neuro 2A, normal epithelial JB-6 cells, and erythrocytes were quite different depending both on structural peculiarities of these glycosides and the type of cells subjected to their actions. Psolusoside L (<b>5</b>), pentaoside, with three sulfate groups at C-6 of two glucose and one 3-<i>O</i>-methylglucose residue and holostane aglycone, is the most active compound in the series. The presence of a sulfate group at C-2 of the terminal glucose residue attached to C-4 of the first (xylose) residue significantly decreases activities of the corresponding glycosides. Psolusosides of group B (<b>1</b>, <b>2</b><b>,</b><b> </b>and known psolusoside B) are inactive in all tests due to the presence of non-holostane aglycones and tetrasaccharide-branched sugar chains sulfated by C-2 of Glc4.
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