Six New Polyhydroxysteroidal Glycosides, Anthenosides S1 – S6, from the Starfish Anthenea Sibogae

Six new polyhydroxysteroidal glycosides, anthenosides S1 – S6 (1 – 6), along with a mixture of two previously known related glycosides, 7 and 8, were isolated from the methanolic extract of the starfish Anthenea sibogae. The structures of 1 – 6 were established by NMR and HR‐ESI‐MS techniques as well as by chemical transformations. All new compounds have a 5α‐cholest‐8(14)‐ene‐3α,6β,7β,16α‐tetrahydroxysteroidal nucleus and differ from majority of starfish glycosides in positions of carbohydrate moieties at C(7) and C(16) (1 – 4, 6) or only at C(16) (5). The 4‐O‐methyl‐β‐d‐glucopyranose residue (2) and Δ24‐cholestane side chain (3) have not been found earlier in the starfish steroidal glycosides. The mixture of 7 and 8 slightly inhibited the proliferation of human breast cancer T‐47D cells and decreased the colony size in the colony formation assay.