Triterpene glycosides from the Vietnamese sea cucumber Holothuria edulis

Abstract

From the MeOH extract of the Vietnamese sea cucumber Holothuria edulis, eight triterpene glycosides (1−8), including one new compound namely holothurin A5 (1), were isolated by using various chromatographic separations. Their structures were established by spectroscopic experiments including 1D, 2D NMR and HR-ESI-MS.Holothurin A5 (1) has a hydroperoxy group at C-25. To the best of our knowledge, this is the first report of this group in triterpene saponins obtained from sea cucumbers to date.In addition, the in vitro cytotoxicity against five human cancer cell lines (HepG2, KB, LNCaP, MCF7 and SK-Mel2) of all isolated compounds was also evaluated using SRB assays.

Structures and Bioactivities of Quadrangularisosides A, A1, B, B1, B2, C, C1, D, D1–D4, and E from the Sea Cucumber Colochirus quadrangularis: The First Discovery of the Glycosides, Sulfated by C-4 of the Terminal 3-O-Methylglucose Residue. Synergetic Effect on Colony Formation of Tumor HT-29 Cells of these Glycosides with Radioactive Irradiation

“…So, the NMR and HR-ESI-MS data indicated the presence of a 25-hydroperoxy-23 E -ene fragment in the side chain of 1 . This is the third finding of a hydroperoxyl group in the triterpene glycosides aglycones of sea cucumbers [ 24 , 25 ].…”

“…Moreover, the assignment to genus Pentacta was also incorrect, since the actual specific name of this sea cucumber indexed by the "WoRMS" database is Colochirus quadrangularis. Secondly, thorough analysis of the NMR data provided in this paper for philinopgenin B possessing, according to the authors, 18 (16)-lactone and unique 20 (25)-epoxy-fragment, has raised many questions. If an 18 (16)-lactone ring was present in the genin, the signals of H-16 and H-17 would be observed as the broad singlets due to the very small value of coupling constant J 17/16 [16,17].…”

“…Two novel aglycones having hydroperoxyl groups in the side chains were discovered in quadrangularisosides A (1) and D 3 (11) (hydroperoxyl group at C( 25)) as well as in quadrangularisosides A 1 (2) and D 4 (12) (hydroperoxyl group at C( 24)). The finding of such functionalities in the aglycones of triterpene glycosides from the sea cucumbers is rare, and two other cases were reported only last year [24,25].…”

Psolusosides C3 and D2-D5, Five Novel Triterpene Hexaosides From the Sea Cucumber Psolus fabricii (Psolidae, Dendrochirotida): Chemical Structures and Bioactivities

“…The finding of hydroperoxy groups in the triterpene glycosides from sea cucumbers is very unusual. But recently the glycoside with the same side chain as psolusoside D 3 (3) having 23E-ene-25-hydroperoxy fragment has been found in Vietnamese sea cucumber Holothuria edulis 6 Thus, psolusoside…”

“…The finding of hydroperoxy groups in the triterpene glycosides from sea cucumbers is very unusual. But recently the glycoside with the same side chain as psolusoside D 3 ( 3 ) having 23 E -ene-25-hydroperoxy fragment has been found in Vietnamese sea cucumber Holothuria edulis 6 indicating these compounds are native. The aglycones of psolusosides C 3 ( 1 ) and D 5 ( 5 ) (side chain with 25- hydroxy-group and 23 E -double bond) could be considered as biosynthetic precursors of psolusoside D 3 ( 3 ) aglycone.…”