Cytotoxic Triterpene Glycosides from Far‐Eastern Sea Cucumbers Belonging to the Genus Cucumaria

New cytotoxic triterpene oligoglycoside disulfates, cucumariosides A 3 ( 1 ) and A 6 ‐2 ( 2 ), have been isolated from the sea cucumber Cucumaria japonica . The trisulfated cucumarioside A 7 ‐3 ( 4 ) was found to be the major component in the glycoside fraction of Cucumaria miniata . The structures were assigned on the basis of extensive spectral data (NMR and MS), selective solvolysis of desulfated derivative 3 and other chemical evidence. The presence or absence of a carbonyl group at C‐16 of the aglycone and of sulfate groups at C‐6 of the glucose and 3‐ O ‐methylglucose units are interpreted in terms of the functional evolution of sea cucumbers in order to improve their defensive system. Both ( 1 ) and ( 2 ) are cytotoxic in vitro at IC 50 = 1 μg/ml against a selection of five human and mice tumoral cell lines.