Regulusosides A, B, and C, Three New Polyhydroxysteroid Glycosides from the Starfish Pentaceraster regulus.

Three new polyhydroxysteroid glycosides, regulusosides A-C (1-3) along with the previously known five steroid compounds (4-8) were isolated from the tropical starfish Pentaceraster regulus. The structures of compounds 1-3 were established by extensive NMR and ESI-MS techniques. New glycosides have the same aglycon, (24S)-5α-cholestane-3β,5,6β,8,15α,24-hexol, and various disaccharide moieties: β-D-xylopyranosyl-(l->2)-3-0-methyl-α-L- arabinofuranosyl (1), β-D-xylopyranosyl-(l->2)-c-L-arabinofuranosy (2), and 2-0-methyl-β-D-xylopyranosyl-(->2)-3-0-methyl-α-L-arabinofuranosy (3), attached at C-24 of the side chain. Compounds 1, 2 and 6 exhibit potential immunomodulatory properties, inducing intracellular ROS (reactive oxygen species) formation in the RAW 264.7 murine macrophage cells.