Two novel pentacyclic aromatic alkaloids, plakinidine A and B, were isolated from a Plakortis sponge. Their structures, which include a pyrrolo[2,3,4-kl]acridine, were determined from extensive 2D NMR experiments. The fused aromatic ring system is a structural variation not previously found in aromatic alkaloids of either marine or terrestrial origin. Plakinidine A and B exhibited in vitro activity against Nippostrongylus brasiliensis, and plakinidine A showed weak activity against reverse transcriptase. © 1990, American Chemical Society. All rights reserved.
