New Discorhabdin B Dimers with Anticancer Activity from the Antarctic Deep-Sea Sponge .

sponges represent a rich source of discorhabdin-type pyrroloiminoquinone alkaloids, a few of which comprise a dimeric structure. The anticancer-activity-guided isolation of the -hexane subextract of the Antarctic deep-sea sponge yielded the known compound (-)-(1R,2R,6R,8S,6'S)-discorhabdin B dimer () and two new derivatives, (-)-(1S,2R,6R,8S,6'S)-discorhabdin B dimer (2) and (-)-(1R,2R,6R,8S,6'S)-16',17'-dehydrodiscorhabdin B dimer (3). The chemical structures of compounds - were elucidated by means of HR-ESIMS, NMR, [], ECD spectroscopy, and a comparison with the previously reported discorhabdin analogs. Compounds and showed significant in vitro anticancer activity against the human colon cancer cell line (HCT-116), with IC values of 0.16 and 2.01 µM, respectively. Compared to monomeric discorhabdins, dimeric discorhabdins are very rare in Nature. This study adds two new discorhabdin dimers ( and ) to this small pyrroloiminoquinone subfamily. This is also the first report of compound as a natural product and the first assessment of its in vitro anticancer activity.