STARFISH SAPONINS .54. CYTOTOXIC ASTEROSAPONINS FROM AN ANTARCTIC STARFISH OF THE FAMILY ECHINASTERIDAE

An investigation of the polar extracts from a starfish, collected in t he Antarctic Sea, and identified as belonging to the Echinasteridae fa mily, has led to the isolation of seven sulphated <<asterosaponins>>. Five are new compounds. Three of them, named antarcticoside A, 1, B, 2 , and C, 3, contain a novel hexasaccharide chain with two branches: i. e., ta-quinovopyranosyl-(1-->3)-beta-quinovopyranosyl, linked to C-6 o f sulphated steroidal aglycones, which differ from one another in the side chains. The novel asterosaponins 4-5, are the 24-methyl analogues of brasiliensoside, 6, and pectinioside A, 7, pentaglycosides describ ed from Echinaster brasiliensis and Asterina pectinifera, respectively . The spectral data of the two remaining asterosaponins agree with tho se of brasiliensoside, 6 and with those of pectinioside A, 7, respecti vely. The isolated asterosaponins have been found to be cytotoxic agai nst human bronchopulmunary non-small-cell-lung carcinoma cells at IC50 < 3.3 mu g/ml.