A new steroidal glycoside granulatoside c from the starfish choriaster granulatus, unexpectedly combining structural features of polar steroids from several different marine invertebrate phyla

Abstract

A new unique steroidal glycoside, granulatoside C (1), was isolated from the ethanol extract of the starfish Choriaster granulatus. The structure of 1 was elucidated by extensive NMR and ESI-MS techniques as (20R)-16,21-O-di-(β-D-fucopyranosyl)-24-methyl-cholesta-5,24(28)-diene-3β,7α,16α,21-tetraol (1). This glycoside is unusual one, because combines some characteristic structural peculiarities of steroids from several different phyla of marine invertebrates, it has a range of structural features that not previously found in starfish polyhydroxysteroidal glycosides, such as Δ5-3β,7α,16α-trihydroxysteroidal nucleus, Δ 24 (28)-21-hydroxy-24-methyl-cholestane side chain and 16,21-diglycosylation by D-fucopyranosyl residues, but also characteristic of sponges, ophiuroids and soft corals, respectively.