Novel Discorhabdin Derivatives from Antarctic Sponges of the Genus Latrunculia: Expanding the Chemical Diversity of Polar Marine Natural Products

In this study, three Antarctic sponges of the genus <i>Latrunculia</i> were investigated, leading to the isolation of five unreported pyrroloiminoquinone alkaloids along with the known metabolite (+)-debromodiscorhabdin A (<b>3</b>). Three of the new metabolites were brominated, while the other two were found to have a C-5/C-8 sulfur bridge and a C-2/N-18 bridge. Three of the metabolites were shown to have a phenyl ketone substituent on C-14, not previously reported for discorhabdin derivatives. The cytotoxicity against the A549 cell lines was studied and compounds <b>1</b>-<b>4</b> showed activity of 4.3, 1.8, 1.0, and 23.9 µM, respectively, while no inhibition was found for <b>5</b> and <b>6</b>.