Structure of Eximisoside A, a Novel Triterpene Glycoside from the Far-Eastern Sea Cucumber Psolus eximius

The new triterpene saponin eximisoside A (1) has been isolated from the Far-Eastern sea cucumber Psolus eximius and its structure elucidated by 1D and 2D NMR (13C, 1H, 1H-1H COSY, HMQC, and NOESY spectra), and FABMS studies. The structural features of eximisoside A (1) are the rare presence of a 23 double bond in the aglycon and the absence of quinovose, typically found in the oligosaccharide chain of holothurian glycosides.