Nine New Triterpene Glycosides, Magnumosides A(1)–A(4), B(1), B(2), C(1), C(2) and C(4), from the Vietnamese Sea Cucumber Neothyonidium (=Massinium) magnum: Structures and Activities against Tumor Cells Independently and in Synergy with Radioactive Irradiation

Nine new sulfated triterpene glycosides, magnumosides A(1) (1), A(2) (2), A(3) (3), A(4) (4), B(1) (5), B(2) (6), C(1) (7), C(2) (8) and C(4) (9) as well as a known colochiroside B(2) (10) have been isolated from the tropical Indo-West Pacific sea cucumber Neothynidium (=Massinium) magnum (Phyllophoridae, Dendrochirotida) collected in the Vietnamese shallow waters. The structures of new glycosides were elucidated by 2D NMR spectroscopy and mass-spectrometry. All the isolated new glycosides were characterized by the non-holostane type lanostane aglycones having 18(16)-lactone and 7(8)-double bond and differed from each other by the side chains and carbohydrate moieties structures. Magnumoside A(1) (1) has unprecedented 20(24)-epoxy-group in the aglycone side chain. Magnumosides of the group A (1–4) contained disaccharide monosulfated carbohydrate moieties, of the group B (5, 6)—tetrasaccharide monosulfated carbohydrate moieties and, finally, of the group C (7–9)—tetrasaccharide disulfated carbohydrate moieties. The cytotoxic activities of the compounds 1–9 against mouse spleen lymphocytes, the ascites form of mouse Ehrlich carcinoma cells, human colorectal carcinoma DLD-1 cells as well as their hemolytic effects have been studied. Interestingly, the erythrocytes were more sensitive to the glycosides action than spleenocytes and cancer cells tested. The compounds 3 and 7 significantly inhibited the colony formation and decreased the size of colonies of DLD-1 cancer cells at non-cytotoxic concentrations. Moreover, the synergism of effects of radioactive irradiation and compounds 3 and 7–9 at subtoxic doses on proliferation of DLD-1 cells was demonstrated.