Starfish Saponins, 52. Chemical Constituents from the Starfish Echinaster brasiliensis

This paper reports an anal. of the chem. constituents from the Caribbean starfish E. brasiliensis collected at Grand Bahama Island. This species is completely devoid of cyclic steroidal glycosides, previously isolated from 2 species of Echinaster in place of the more common penta- and hexa-glycoside steroidal sulfates (asterosaponins). Two typical asterosaponins and 10 glycosides of polyhydroxysteroids were instead isolated in relatively large amts. from E. brasiliensis. The asterosaponins include the known marthasteroside A1 and the new brasiliensoside, while the glycosides of polyhydroxysteroids include 7 new compds. (6 monoglycosides and 1 diglycoside). The known echinasteroside A, previously found in E. sepositus and in the related Henricia laeviuscula (both belonging to the family Echinasteridae), and laeviusculosides C and I from H. laeviuscula were also isolated. Most of the glycosides from E. brasiliensis are 3-O-β-xylopyranosides of Δ4-3β,6β,8,15α,15β-pentahydroxysteroid aglycons, having different side chains and sometimes a sulfate group at C-15, structural features which are typical of steroidal glycosides from starfishes of the family Echinasteridae. Continuing the anal. of the constituents of E. brasiliensis, the authors have also isolated a series of anthraquinones, known animal pigments found only in echinoderms and particularly in Crinoidea and in the Echinasteridae family of Asteroidea.