Protease Inhibitors from <i>Microcystis aeruginosa</i> Bloom Material Collected from the Dalton Reservoir, Israel

Nine new metabolites, aeruginosins DA495A (<b>1</b>), DA511 (<b>2</b>), DA642A (<b>3</b>), DA642B (<b>4</b>), DA688 (<b>5</b>), DA722 (<b>6</b>), and DA495B (<b>7</b>), microguanidine DA368 (<b>8</b>), and anabaenopeptin DA850 (<b>9</b>), were isolated along with the known micropeptins MZ924, MZ939A, and MZ1019, cyanopeptolins S and SS, microcin SF608, and aeruginazoles DA1497, DA1304, and DA1274 from bloom material of the cyanobacterium <i>Microcystis aeruginosa</i> collected from the Dalton reservoir, Israel, in October 2007. Their structures were elucidated by a combination of various spectroscopic techniques, primarily NMR and MS, while the absolute configurations of the asymmetric centers were determined by Marfey’s and chiral-phase HPLC methods. Two of the new aeruginosins, DA511 (<b>1</b>) and DA495A (<b>2</b>), contain a new Choi isomer, (2<i>S</i>,3a<i>S</i>,6<i>S</i>,7a<i>S</i>)-Choi. The structure elucidation and biological activities of the new metabolites are described