Aplidiasterols A and B, two new cytotoxic 9,11-secosterols from the Mediterranean ascidian Aplidium conicum.

Two novel 9,11-secosterols, aplidiasterols A (3beta,6beta,11-trihydroxy-9,11-seco-5alpha-cholest-7-en-9-one, 1) and B (3beta,5alpha,6beta,11-tetrahydroxy-9,11-secocholest-7-en-9-one, 2), along with the known secosterols 3 and 4, were isolated from the Mediterranean ascidian Aplidium conicum and their structures were determined by spectroscopic data. Aplidiasterols A and B were found to be cytotoxic against rat glioma (C6) and murine monocyte/macrophage (J774) tumor cells in vitro. Compounds 1-4 represent the first example of secosterols isolated from tunicates.