Bioactive isoquinolinequinone alkaloids from the South China Sea nudibranch Jorunna funebris and its sponge-prey Xestospongia sp.

Background: Nudibranchs are slug-like invertebrates, well known as rich sources of biologically active secondary metabolites with highly chemical diversity and complexity. The production of such interesting metabolites was possibly influenced by their diet relationship with sponges such as Xestospongia. Results: Our continuous investigation of South China Sea nudibranch Jorunna funebris and its sponge-prey Xestospongia sp. led to the isolation of two new and eight known metabolites (1-10). The absolute configurations were determined by time-dependent density functional theory (TDDFT) electronic circular dichroism (ECD) method and by the comparison of ECD spectra. In bioassays, 1-4 and 7 showed strong NF-kappa B inhibitory activity, 4-6 exhibited considerable cytotoxicity against A549 and HL-60 tumor cell lines. Conclusion: Five unusual isoquinolinequinones (3, 7-10) were discovered from both two animals, further confirmed their predator-prey relationship. Preliminary bioassay results and structure-activity relationship studies suggested that several isolated compounds were potential to be drug leads.