The Hoiamides, Structurally Intriguing Neurotoxic Lipopeptides from Papua New Guinea Marine Cyanobacteria

Two related peptide metabolites, one a cyclic depsipeptide, hoiamide B , and the other a linear lipopeptide, hoiamide C, were isolated from two different collections of marine cyanobacteria obtained in Papua New Guinea. Their structures were elucidated by combining various techniques in spectroscopy, chromatography and synthetic chemistry. Both metabolites belong to the unique hoiamide structural class, characterized by possessing an acetate extended and S-adenosyl methionine modified isoleucine unit, a central triheterocyclic system comprised of two -methylated thiazolines and one thiazole, as well as a highly oxygenated and methylated C-15 polyketide unit. The cyclic depsipeptide 2 stimulated sodium influx and suppressed spontaneous Ca2+ oscillations with EC50 values of 3.92 μM and 79.8 nM, respectively, while 3 had no significant effects in these assays