Mass Spectral Investigation on Toxins. I. Isolation, Purification, and Characterization of Hepatotoxins from Freshwater Blue-Green Algae (Cyanobacteria) by High-Performance Liquid Chromatography and Fast Atom Bombardment Mass Spec

摘要

Toxic peptides of freshwater cyanobacteria (blue-green algae) from two European Microcystis aeruginosa and one Canadian Anabaena flos-aquae were purified by high-performance liquid chromatography (HPLC) and examined by amino acid analysis and mass spectrometry. A toxic fraction from a butanol/methanol extract of toxic lyophilized cells was separated by G-25 gel filtration and purified by HPLC using a C-18 semiprep Column. A toxic peak with the same elution time was detected for each of the three toxic cyanobacteria. Signs of poisoning for the desalted, purified toxins (LD50, intraperitoneal mouse, 50 micrograms/kg) were identical with those previously reported for hepatotoxic peptides from Microcystis aeruginosa. On hydrolysis and amino acid analysis, all three toxins showed a similar profile consisting of equimolar amounts of glutamic acid, alanine, arginine, and leucine, Beta-methylaspartic acid was identified in all of the toxic peptides. The Fast Atom Bombardment (FAB) mass spectra of the toxins indicated the molecular weight to be 994 for all peptides. The absence of sequence ions in their corresponding FAB spectra indicated that the peptides were cyclic.