Triterpene glycosides from the sea cucumber Eupentacta fraudatrix. Structure and biological activity of cucumariosides B_1and B_2, two new minor non-sulfated unprecedented triosides

摘要

Two new minor triterpene glycosides, cucumariosides B_1 (1) and B_2 (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 B_1 (1) was not active in any of the tests, while cucumarioside B_2 (2) demonstrated moderate hemolytic activity and low cytotoxic action against Ehrlich carcinoma cells.