The toxicity and enzyme activity of a chlorine and sulfate containing aeruginosin isolated from a non-microcystin-producing Planktothrix strain

Abstract The toxicity of six different Planktothrix strains was examined in acute toxicity assays with the crustacean Thamnocephalus platyurus. The presence of toxicity in two strains could be explained by the occurrence of microcystins. The other four Planktothrix strains were not able to produce microcystins due to different mutations in the microcystin synthetase (mcy) gene cluster. In these strains, toxicity was attributed to the presence of chlorine and sulfate containing compounds. The main representative, called aeruginosin 828A, of such a compound in the Planktothrix strain 91/1 was isolated, and structure elucidation by 2D NMR and MS methods revealed the presence of phenyllactic acid (Pla), chloroleucine (Cleu), 2-carboxy-6-(4′-sulfo-xylosyl)-octahydroindole (Choi), and 3-aminoethyl-1-N-amidino-Δ-3-pyrroline (Aeap) residues. Aeruginosin 828A was found to be toxic for T. platyurus with a LC50 value of 22.4 Î¼M, which is only slightly higher than the toxicity found for microcystins. Additionally