Four New Steroidal Glycosides, Protolinckiosides A - D, from the Starfish Protoreaster lincki.

Four new steroidal glycosides, protolinckiosides A - D (1 - 4, resp.), were isolated along with four previously known glycosides, 5 - 8, from the MeOH/EtOH extract of the starfish Protoreaster lincki. The structures of 1 - 4 were elucidated by extensive NMR and ESI-MS techniques as (3β,4β,5α,6β,7α,15α,16β,25S)-4,6,7,8,15,16,26-heptahydroxycholestan-3-yl 2-O-methyl-β-d-xylopyranoside (1), (3β,5α,6β,15α,24S)-3,5,6,8,15-pentahydroxycholestan-24-yl α-l-arabinofuranoside (2), sodium (3β,6β,15α,16β,24R)-29-(β-d-galactofuranosyloxy)-6,8,16-trihydroxy-3-[(2-O-methyl-β-d-xylopyranosyl)oxy]stigmast-4-en-15-yl sulfate (3), and sodium (3β,6β,15α,16β,22E,24R)-28-(β-d-galactofuranosyloxy)-6,8,16-trihydroxy-3-[(2-O-methyl-β-d-xylopyranosyl)oxy]ergosta-4,22-dien-15-yl sulfate (4). The unsubstituted β-d-galactofuranose residue at C(28) or C(29) of the side chains was found in starfish steroidal glycosides for the first time. Compounds 1 - 4 significantly decreased the intracellular reactive oxygen species (ROS) content in RAW 264.7 murine macrophages at induction by proinflammatory endotoxic lipopolysaccharide (LPS) from E. coli.