Cytotoxic Microcolin Lipopeptides from the MarineCyanobacterium Moorea producens

Nine new linear lipopeptides, microcolins E–M (1–9), together with four known related compounds, microcolins A–D (10–13), were isolated from the marine cyanobacterium Moorea producens using bioassay-guided and LC-MS/MS molecular networking approaches. Catalytic hydrogenation of microcolins A–D (10–13) yielded two known compounds, 3,4-dihydromicrocolins A and B (14, 15), and two new derivatives, 3,4-dihydromicrocolins C and D (16, 17), respectively. The structures of these new compounds were determined by a combination of spectroscopic and advanced Marfey’s analysis. Structurally unusual amino acid units, 4-methyl-2-(methylamino)pent-3-enoic (Mpe) acid and 2-amino-4-methylhexanoic acid (N-Me-homoisoleucine), in compounds 1–3 and 8, respectively, are rare residues in naturally occurring peptides. These metabolites showed significant cytotoxic activity against H-460 human lung cancer cells with IC50 values ranging from 6 nM to 5.0 μM. The variations in structure and attendant biological activities provided f...