Starfish Saponins XXX. Isolation of Sixteen Steroidal Glycosides and Three Polyhydroxysteroids from the Mediterranean Starfish Coscinasterias Tenuispina

Sixteen steroidal glycosides have been isolated from the starfish Coscinasterias tenuispina. The more polar components are the “asterosaponins” 1A–1E, 2A–2C, 3E and 3G, consisting of a Δ9(11)-3β,6α-dihydroxysteroidal moiety, a pentasaccharide portion attached at C-6 and a sulphate group at C-3. Compounds 1C, 2C and 1D are new saponins assigned as the tenuispinoside A through C. The second group of polar glycosides consists of two new xylose saponins, possessing monosulphate polyhydroxysteroidal aglycones and two new 4-O-sulphated glucose saponins, assigned as the coscinasteroside A through D (4–2). The less polar glycosides are the new “non-sulphated” xylosides 8 and 9, designed as coscinasterosides E and F. The structures of the new saponins were determined by extensive 1H and 13C NMR investigations, FAB mass spectroscopy, and by comparison with known compounds. The location of the sulphate ester functionalities in 4–7 were assigned on comparison of their spectral data with those of the corresponding desulphated analogues. C. tenuispina also contains three new monosulphated polyhydroxysteroids, which were assigned the structures 10 to 12.