Glycosides from the North Atlantic sea cucumber <i>Cucumaria frondosa</i> V - Structures of five new minor trisulfated triterpene oligoglycosides, frondosides A₇-1, A₇-2, A₇-3, A₇-4, and isofrondoside C

Abstract

Seven highly polar trisulfated triterpene glycosides belonging to the frondoside A 7 group have been isolated from the North Atlantic sea cucumber Cucumaria frondosa. The structures of five new glycosides, frondosides A 7 -1 (1), A 7 -2 (2), A 7 -3 (3), A 7 -4 (4), and isofrondoside C (5) were elucidated, three of which contained lanostane aglycons without a lactone-ring. Three pairs of the glycosides proved to be isomers by virture of the positions of double bonds in the aglycons nuclei; two pairs of the glycosides differed from each other by the character of the oxygen functionality at C-22. The results from these studies provided the basis for postulating the biosynthetic pathways of norlanostane glycosides in the sea cucumber.Key words: Cucumaria frondosa, sea cucumbers, frondosides, triterpene glycosides.