Structure of cucumarioside I2 from the sea cucumber Eupentacta fraudatrix ( Djakonov et Baranova) and cytotoxic and immunostimulatory activities of this saponin and relative compounds

A new triterpene glycoside cucumarioside I-2 (1) has been isolated from holothurian Eupentacta fraudatrix. The structure of 1 was elucidated using extensive NMR spectroscopy (H-1 and C-13 NMR, H-1-H-1 COSY, 1D TOCSY, HSQC, H2BC, HMBC and NOESY) and MALDI-TOF-MS. Glycoside 1 is a disulfated branched pentaoside having rare 3-O-methyl-D-xylose. Cytotoxic activity of the glycoside 1 and known cucumariosides H (2), A(5) (3), A(6) (4), B-2 (5) and B-1 (6) against mouse Ehrlich carcinoma cells and their influence on lysosomal activity of mouse peritoneal macrophages have been studied. Glycosides 1 and 5 possessed low cytotoxicities, glycoside 6 was not cytotoxic while compounds 2, 3 and 4 possessed moderate cytotoxicities. Glycosides 1, 3 and 5 increased the lysosomal activity of macrophages on 15-17% at doses of 1-5g/mL. Hence lysosomal activity depends on structures of both aglycone and carbohydrate chain and does not have a direct correlation with cytotoxicities of the glycosides.