STARFISH SAPONINS .52. CHEMICAL-CONSTITUENTS FROM THE STARFISH ECHINASTER BRASILIENSIS

This paper reports an analysis of the chemical constituents from the C aribbean starfish Echinaster brasiliensis collected at Grand Bahama Is land, This species is completely devoid of cyclic steroidal glycosides , previously isolated from two species of the genus Echinaster in plac e of the more common penta- and hexa-glycoside steroidal sulfates (''a sterosaponins''). Two typical ''asterosaponins'' and ten glycosides of polyhydroxysteroids were instead isolated in relatively large amounts from E. brasiliensis. The asterosaponins include the known marthaster oside A(1) [1] and the new brasiliensoside [2], while the glycosides o f polyhydroxysteroids include seven new compounds (six monoglycosides and one diglycoside). The known echinasteroside A, previously found in Echinaster sepositus and in the related Henricia laeviuscula (both be longing to the family Echinasteridae), and laeviusculosides C and I fr om H. laeviuscula were also isolated. Most of the glycosides from E. b rasiliensis are 3-O-beta-xylopyranosides of Delta(4)-3 beta,6 beta,8,1 5 alpha,16 beta pentahydroxysteroid aglycones, having different side c hains and sometimes a sulfate group at C-15, structural features which are typical of steroidal glycosides from starfishes of the family Ech inasteridae. Continuing the analysis of the constituents of E. brasili ensis, we have also isolated a series of anthraquinones, known animal pigments found only in echinoderms and particularly in Crinoidea and i n the Echinasteridae family of Asteroidea.