Structures and cytotoxic properties of cucumariosides H2, H3 and H4 from the sea cucumber Eupentacta fraudatrix

New triterpene glycosides, cucumariosides H-2 (1), H3 (2) and H-4 (3), have been isolated from the Far Eastern sea cucumber Eupentacta fraudatrix. The structures of 1-3 were elucidated using extensive NMR spectroscopy (1 H-and 13 C-NMR, DEPT, H-1-H-1 COSY, 1D TOCSY, H2BC, HMBC, heteronuclear single-quantum coherence, and NOESY) and ESI-MS. Glycosides 1-3 are mono-sulphated branched pentaosides having rare 3-O-methyl-D-xylose as a terminal monosaccharide. Glycosides 1 and 3 contain holostane aglycones, whereas 2 has a 23,24,25,26,27-pentanorlanostane aglycone with an 18(16)-lactone, which is also uncommon for the sea cucumbers. Glycoside 3 contains a very rare ethoxyl radical at C-25 of the aglycone side chain, and it is most probably an artefact that was formed during long storage of the ethanolic extract. Cytotoxic activities of 1-3 against mouse spleen lymphocytes, haemolytic activity against mouse erythrocytes and Ehrlich carcinoma cells have been studied. The presence of 25-hydroxy group in aglycone moiety significantly decreased the activities.