: Cavernosine, a novel ichthyotoxic terpenoid lactone has been isolated from the sponge Fasciospongia cavernosa. Its structure has been determined by spectral analysis, chemical degradation and correlation with 8-ionone.During this last decade, a great variety of secondary metabolites have been isolated from marine sponges ( 3 ) . It has been repeatedly suggested that some of these compounds may act as deterrents against potential predators (4'5). Thus it is not surprising that many of them show ichthyotoxic activity. This aspect of the ecology of sponges has been briefly discussed in a recent paper ( 6 ) .In the course of OUT invescigations on ecologically significant constituents of sponges, we now wish to present the structure elucidation of cavernosine (i), a novel terpenoid lactone. This compound is responsible, at least in part, for the toxicity of the dichloromethane extract of the marine sponge Fasciospongia cauernosa asainst the freshwater fish Lebistes reticulatus (LD=ZOmg/l). Successive silica gel column chromatographies of the CH C1 extract, monitored by toxicity bioassays, yielded a toxic fraction containing most of the original activity. This fraction shows two main spots on tlc. After further purification, it was found that ichthyotoxicity was associated with each of these spots. The more polar spot corresponds to a mixture of 5.8-sterol peroxides which was not further examined ('). The less polar spot corresponds to a single derivative, homogeneous by GLC, which was named cavernosine . Ac O/pyridine at room temperature, the hydroxyl group must be tertiary. The isoprenoid character of -1 was suggested by the presence in its 'H NMR spectrum of four 3H singlets attributable to four quaternary methyl groups [two on sp3 carbon atoms (6 0.98 and O.99), one on an sp2 carbon atom (6 1.58) and one on an sp -2 carbon atom bearing an oxygen atom (6 1-34)].-7 9 1 -
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