Lyngbyastatins 8–10, Elastase Inhibitors with Cyclic Depsipeptide Scaffolds Isolated from the Marine Cyanobacterium Lyngbya semiplena

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 IC50 values of 123 nM, 210 nM and 120 nM, respectively.