Nobilisides A - C, three new triterpene glycosides from the sea cucumber Holothuria nobilis.

Three new triterpene glycosides, named nobilisides A ( 1), B ( 2) and C ( 3), were isolated from the sea cucumber Holothuria nobilis Selenka. Their structures were deduced by extensive spectral analysis and chemical evidence. Compounds 1 and 3 are non-sulfated monoglycosides while 2 is a sulfated diglycoside. The presence of two conjugated double bonds [22 E,24-diene and 7,9(11)-diene] in the aglycone of 1 is a rare structural feature among sea cucumber glycosides, while 2 and 3 possess the same 22,25-epoxy moiety as their side chains. All three glycosides exhibited significant cytotoxicity against human tumor cell lines.