Pure & Appl.Che,j., Vol.54, No.10, pp.l935—I950, 1982. 00334545/821b0193516$03.00/0 Printed in Great Britain. Pergamon Press Ltd. ©1982 IUPAC STEROIDAL GLYCOSIDES FROM STARFISHES L. Minale , C. Pizza, R. Riccio and F. Zollo Istituto di Chimica Biorganica, Università, Via RodinO, 22,Napies, and Istituto di Chimica di Molecole di Interesse Biologico del C.N.R., Arco Felice, Naples, Italy Abstract - This paper covers recent work - much of it from the author's laboratory - dealing with novel steroidal oligoglyco- sides from starfishes. The steroidal glycosides until now encountered in this class of marine animals can be grouped into three structure types. Compounds of the first type, reco- gnized for long time, include the sulphated saponins (astero- saponins) , characterized by steroidal aglycones possessing a 3,6ct-diol pattern and a 9,11-double bond; the oligosaccharide moiety (four up to six sugar units) is attached at C-6 and the sulphate residue is at C-3. Compounds of the second type, recently discovered in two species of the genus Echinaster, have a number of unusual features: a L7,3,613-dihydroxy stero- idal moiety, there is no sulphate group and, most remarkably, the carbohydrate chain (three sugar units) is cyclized between C-3 and C-6 of the aglycone. Compounds of the third type include glycosides having highly hydroxylated steroidal agly- cones; the carbohydrate moiety (one or two sugar units) is attached at C-24 of the side chain and there is no sulphate residue. During the course of our investigation on the stero- idal glycosides from starfishes we have also encountered several polyhydroxylated sterols and their structures are presented. INTRODUCTION Saponins, water soluble compounds composed of sugars and steroid or triterpen- oid moieties, are common constituents of terrestrial plants, but are uncommon as animal constituents. In the animal kingdom saponins have been found in the exclusively marine phylum Echinodermata and particularly in species of the classes Holothuroidea (sea cucumbers) and Asteroidea (starfishes) . These compounds are apparently absent from the other three classes, Crinoidea (sea lilies), Echinoidea (sea urchins) and Ophiuroidea (brittle stars), of echino- derms. Saponins derived from sea-cucumbers (holothurins) are triterpenoid glycosides, which, upon acid hydrolysis, give triterpenoid aglycones based on the lanos- tane skeleton, sugars and sulphate, whereas those from starfishes (asterosa— ponins) are sulphated steroidal glycosides (Ref s. 1, 2, 3). The toxicity of starfishes has been described in various ways for many years, but most of the reports can be explained by the presence of saponins. Starfish extracts and also purified saponins have been reported to exhibit a broad spectrum of physiological and pharmacological activities. Asterosaponins are highly surface active, and most of them show potent haemolitic properties (Ref s. 2, 4). They also have antitumor (Ref. 5) and antibacterial activities (Ref. 6); Shimizu reported that asterosaponins from Asterias forbesi, ster planci and Asterina pectinifera inhibited influenza virus multiplication (Ref. 7). Antiinflammatory activity was reported for Asterias forbesi saponins (Ref. 8), and activity toward contraction of the rat phrenic nerve-diaphram preparation was reported for Asterias amurensis saponins (Ref. 9). Several observations concerning with the biological functions of the asterosaponins have also been described. Because of their general toxicity it is probable that saponins act primarily as chemical defence agents, discouraging many predators; they also induce escape reactions in bivalve molluscs (Ref. 10), thus reducing the predation ability of the starfishes theirself. Asterosaponins have been identified as the spawning inhibitor in the Japanese starfish Asteria amurensis (Ref. 11) and more recently they have been reported 1935