Synaptosides A and A1, triterpene glycosides from the sea cucumber Synapta maculata containing 3-O-methylglucuronic acid and their cytotoxic activity against tumor cells

Two novel triterpene holostane glycosides, synaptosides A ( 1) and A 1 ( 2), have been isolated from the Vietnamese sea cucumber Synapta maculata (Synaptida, Apodida). Their structures were elucidated by spectroscopic methods (NMR and MS) and chemical transformations. Glycosides 1 and 2 have rare branched pentasaccharide carbohydrate chains featuring a 3- O-methylglucuronic acid residue not previously reported in glycosides from sea cucumbers and a 6- O-sulfated glucose. Glycoside 2 has an oxo group at C-7 and a 8(9)-double bond. All these structural features are unknown in glycosides from sea cucumbers. Glycoside 1 has moderate cytotoxic activity (IC 50 8.6 microg/mL) and glycoside 2 is inactive against HeLa tumor cells.