Cyanopeptolin SS, a disulphated depsipeptide from a water bloom: structural elucidation and biological activities

A new cyclic depsipeptide, cyanopeptolin SS, was isolated from a water bloom in Leipzig (Germany) dominated by Microcystis aeruginosa (Kützing) Kützing. The structure was determined by amino acid analysis, mass spectrometry, two-dimensional nuclear magnetic resonance spectroscopy, and Fourier-transformed infrared micro-spectroscopy. The structure of cyanopeptolin SS was similar to the previously reported monosulphated cyanopeptolin S isolated from the same water bloom. but cyanopeptolin SS contained a disulphated glyceric acid side chain. In contrast to microcystins, which co-occurred in the same water bloom. cyanopeptolin S and cyanopeptolin SS had no toxic effects on isolated rat hepatocytes. Cyanopeptolin S and SS inhibited trypsin, thrombin and plasmin. Their effects on protein phosphatases are discussed.