Triterpene glycosides from Antarctic sea cucumbers III. Structures of liouvillosides A(4) and A(5), two minor disulphated tetraosides containing 3-O-methylquinovose as terminal monosaccharide units from the sea cucumber Staurocucumis liouvillei (Vaney)

Two new minor triterpene glycosides, liouvillosides A(4) (1) and A(5) (2) have been isolated from the sea cucumber Staurocucumis liouvillei living in Antarctic and Sub-Antarctic waters. The structures of the new glycosides were elucidated using extensive nuclear magnetic resonance (NMR) spectroscopy (H-1- and C-13-NMR spectroscopy, H-1-H-1 COSY, 1D-TOCSY, HMBC, HSQC and NOESY), ESI-MS and MALDI TOF MS. The glycosides 1 and 2 are disulphated tetraosides having very rare 3-O-methylquinovose as terminal monosaccharide.