The sterols of the echinoderm Asterias rubens

1. Twenty-two sterols were identified in the starfish Asterias rubens (Phylum, Echinodermata; Class, Asteroidea). 2. The major 4-demethyl sterols had a Δ7 bond and the C27 compound 5α-cholest-7-en-3β-ol predominated over other mono- and di-unsaturated sterols belonging to the C26, C27, C28 and C29 series. 3. Small amounts of cholest-5-en-3β-ol and 5α-cholestan-3β-ol were also present. 4. The minor sterols identified all contained either one or two methyl groups at C-4 and are considered to be potential biosynthetic precursors of 5α-cholest-7-en-3β-ol. 5. Three sterols possessing a 9β,19-cyclopropane ring were also isolated and were probably derived by the starfish from a dietary source.