ABSTRACT
This chapter discusses the structures and cytotoxicity of these compounds, and speculate on their mode of action. Ascidians or sea squirts are marine benthic invertebrate organisms from which a large number of biologically active compounds have been isolated, ranging from simple organic molecules to alkaloids and complex peptides and depsipeptides. The cells were exposed to the toxins for 1 hour, and viability determined after several days. The primary mode of action remains to be determined and this new class of toxins promises to provide us with useful new probes with which to dissect the molecular mechanisms governing cell growth regulation and differentiation. The cyclic peptides are purified from an organic solvent extract of frozen animal tissue by chromatography on a preparative reverse-phase HPLC column. The structures are determined by amino acid analysis, two-dimensional NMR Spectroscopy and mass spectroscopy. The crystal structures of ascidiacyclamide and patellamide D have been determined and also the solution structure of ulithia-cyclamide.
