New Theonellapeptolides from Indonesian Marine Sponge Theonella swinhoei as Anti-Austerity Agents

We reported three new members of the theonellapeptolide family from theonellapeptolide II series, namely theonellapeptolides IIb (1), IIa (2), IIc (3), and three known members-IId (4), IIe (5), and Id (6)-from Kodingarengan marine sponge Theonella swinhoei collected in Makassar, Indonesia. The structures of tridecadepsipeptides 1-3, including the absolute configurations of their amino acids, were determined by the integrated NMR and tandem MS analyses followed by Marfey's analysis. To the best of our knowledge, 1 and 2 are the first theonellapeptolide-type compounds to have a valine residue with _D configuration at residue position 6. The isolated theonellapeptolide-type compounds 1-6 showed selective cytotoxic activity against human pancreatic MIA PaCa-2 cancer cells in a nutrient-deprived medium. Among them, the most potent preferential cytotoxicity was observed in new theonellapeptolide IIc (3) and known IId (4), IIe (5), and Id (6).