Starfish saponins. Part 14. Structures of the steroidal glycoside sulphates from the starfish Marthasterias glacialis

Abstract

The major sulphated asterosaponins, marthasterosides A₁, A₂, B, and C, isolated from the starfish Marthasterias glacialis, have been completely characterized. Marthasterosides A₁ and A₂ are hexaglycosides and contain the same aglycone, thornasterol A. They have been established as 6α-O-{β-D-fucopyranosyl-(1→3)-β-D-fucopyranosyl-(1→2)-β-D-galactopyranosyl-(1→4)-[β-D-quinovopyranosyl-(1→2)]-β-D-xylopyranosyl-(1→3)-β-D-quinovopyranosyl}-20-hydroxy-23-oxo-5α-cholest-9(11)-en-3β-yl sodium sulphate (6) and 6α-O-{β-D-fucopyranosyl-(1→3)-β-D-fucopyranosyl-(1→2)-β-D-quinovopyranpsyl-(1→4)-[β-D-quinovopyranosyl-(1→2)]-β-D-xylopyranosyl-(1→3)-β-D-quinovopyranosyl}-20-hydroxy-23-oxo-5α-cholest-9(11 )-en-3β-yl sodium sulphate (7) respectively. Marthasterosides B and C are the pentaglycosides (8) and (9); they contain the same oligosaccharide moiety, i.e. β-D-fucopyranosyl-(1→2)-β-D-fucopyranosyl-(1→4)-[β-D-quinovopyranosyl-(1→2)]-β-D-quinovo-pyranosyl-(1→3)-β-D-glucopyranosyl, which is attached to C-6 of 3β-sulphomarthasterone, i.e. 3β,6α-dihydroxy-5α-cholesta-9(11)24-dien-23-one, and of 3β-sulpho-24,25-dihydromarthasterone, respectively.