New Cytotoxic Peroxylactones from the Marine Sponge, Plakinastrella onkodes

: Three new peroxylactones, plakortolides B [6], C [7], and D [8], and a new peroxy ester, epiplakinic acid E methyl ester [9], were isolated and characterized from a previously unstudied marine sponge, Plakinastrella onkodes. A mixture of steroidal peroxides was also found in this organism. Plakortolides B [6] and D [8], and epiplakinic acid E methyl ester [9], were evaluated for biological activity and found to show cytotoxicity against the A549 human lung carcinoma and P388 murine leukemia cell lines, and to effect adhesion in an assay employing the EL-4.IL-2 cell line, which correlates with signal transduction activity.