Marine microorganisms are potentially prolific sources of highly bioactive secondary metabolites that might represent useful leads in the development of new pharmaceutical agents. As part of our ongoing search for new antitumour metabolites produced by microorganisms from marine organisms, anthcolorins A (1)-H (8) have been isolated from a strain of Aspergillus versicolor OUPS-N136 originally separated from the sea urchin Anthocidaris crassispina. The absolute stereostructures for these metabolites have been elucidated by spectroscopic and X-ray analyses. Compounds 1-4, 7 and 8 are tricyclic diterpenes with an oxindole moiety, while 5 and 6 have structures in which the C-ring of 1 and 2 is opened. Among these compounds, 1-4 exhibited significant cytotoxicity against cultured P388 cells.
