Psolusosides C3 and D2-D5, Five Novel Triterpene Hexaosides From the Sea Cucumber Psolus fabricii (Psolidae, Dendrochirotida): Chemical Structures and Bioactivities

Five new triterpene glycosides, psolusosides C-3 (1), D-2 (2), D-3 (3), D-4 (4), and D-5 (5), have been isolated from the sea cucumber Psolus fabricii. The structures of these glycosides were elucidated by 2-dimensional nuclear magnetic resonance spectroscopy and high-resolution mass spectrometry. All the compounds contain hexasaccharide carbohydrate chains, differing from each other in the third monosaccharide residue: xylose was found in psolusosides of group C and glucose in group D. Aglycones of the isolated compounds belong to the holostane type, contain 9(11)-double bond and 16-keto-group and have different side chains. The hemolytic activity against mouse erythrocytes and cytotoxic activity against mouse Ehrlich carcinoma cells (ascite form) and neuroblastoma Neuro 2A cells of 1 to 5 as well as the psolusosides isolated by us earlier, C-1, C-2, and D-1, 26-nor-25-oxo-holotoxin A(1), and holotoxin A(1), have been studied. Psolusosides C-2, D-1, and D-2 (2) having the aglycones without hydroxy group in the side chain showed the strongest hemolytic action in this series. Psolusoside D-3 (3) containing a peroxide group in the side chain of its aglycone was surprisingly highly cytotoxic in all the tests.