TOXINS FROM ASCIDIANS

A wide range of toxins with interesting pharmacological properties hav e been isolated from ascidians. These include cyclic peptides, one of which, didemnin B, is undergoing clinical trials for cancer chemothera py and is also a powerful immunosuppressive agent. Other classes of to xins from these organisms are alkaloids, macrolides, polyethers, preny lated hydroquinones and others of diverse chemical structure. The majo rity of these compounds are cytotoxic and in some cases the mechanisms of action have been investigated. The toxins are most likely used for chemical defense but the question of how the ascidians themselves esc ape the toxic actions is also not resolved.