ISOLATION, STRUCTURE ELUCIDATION, AND BIOLOGICAL-ACTIVITY OF THE STEROID OLIGOGLYCOSIDES AND POLYHYDROXYSTEROIDS FROM THE ANTARCTIC STARFISH ACODONTASTER CONSPICUUS

A total of 19 steroids, of which 13 steroidal oligoglycosides (nine ne w and four known) and six polyhydroxylated steroids (four new and two known), has been isolated from the Antarctic starfish Acodontaster con spicuus. The mixture is dominated by glycosides composed of steroidal aglycons having the hydroxyl groups typically disposed on one side of the tetracyclic nucleus, i.e., 3 beta,4 beta,6 alpha,8,15 beta-, with some having a sulfate at C-6, and differing in the side chains and/or in the disaccharide moieties that are usually attached at C-26, with s ome at C-28 and C-29. Those compounds are accompanied by minute amount s of glycosides with a Delta(8(14))-double bond in the steroid, which is a structural feature not previously found among polyhydroxysteroids derived from starfish. Small amounts of six related unglycosidated po lyhydroxysteroids and three higher-molecular-weight asterosaponins com plete the composition of the mixture. The structures of the new compou nds were determined by interpretation of their spectral data and by co mparison with spectral data of known compounds. Eighteen of these comp ounds were evaluated for their ability to inhibit growth in Antarctic marine bacteria isolated from either the water column or the surfaces of benthic marine invertebrates. Of these compounds, 50% were active a gainst at least one Antarctic marine bacterium. This suggests that the se compounds may play an important role in deterring microbial fouling .