Investigation of an extract from the marine cyanobacterium Lyngbya semiplena, collected in Tumon Bay, Guam, led to the identification of three new cyclodepsipeptides, lyngbyastatins 8-10 (1-3). The structures of 1-3 were determined by NMR, MS, ESIMS fragmentation and chemical degradation. Compounds 1-3 are closely related to lyngbyastatins 4-7. Like the latter compounds, we found 1-3 to inhibit porcine pancreatic elastase, with IC(50) values of 123 nM, 210 nM and 120 nM, respectively.
Keywords: Lyngbya semiplena; cyanobacteria; cyclic depsipeptides; elastase inhibitors; lyngbyastatins.