Triterpene glycosides from the sea cucumber Eupentacta fraudatrix. Structure and biological activity of cucumariosides B1 and B2, two new minor non-sulfated unprecedented triosides.

Two new minor triterpene glycosides, cucumariosides B1 (1) and B2 (2) have been isolated from the Far Eastern sea cucumber Eupentacta fraudatrix. Structures of the glycosides were elucidated by 2D NMR spectroscopy and MS. Glycosides 1 and 2 belong to the cucumariosides B group and have unprecedented trisaccharide carbohydrate moieties without sulfate groups. Glycosides 1 and 2 differ from each other in side chain structures in the aglycone moieties. These minor substances are probably intermediate metabolites in the biosynthesis of triterpene pentaosides. Cytotoxic activities of glycosides 1 and 2 against mouse spleen lymphocytes and the cells of the ascite form of mouse Ehrlich carcinoma were studied, along with hemolytic activity against mouse erythrocytes and antifungal activity. Cucumarioside B1 (1) was not active in any of the tests, while cucumarioside B2 (2) demonstrated moderate hemolytic activity and low cytotoxic action against Ehrlich carcinoma cells.