Isolation and identification of eight microcystins from thirteen Oscillatoria agardhii strains and structure of a new microcystin

Abstract

Microcystins (cyclic heptapeptide hepatotoxins), isolated from 13 freshwater Oscillatoria agardhii strains from eight different Finnish lakes by high-performance liquid chromatography, were characterized by amino acid analysis, fast atom bombardment mass spectrometry (FABMS), and tandem FABMS (FABMS/collisionaryinduced dissociation/MS). All strains produced two to five different microcystins. In total, eight different compounds, of which five were known microcystins, were isolated. The known compounds identified were [D-Asp3]MCYST (microcystin)-LR, [Dha71MCYST-LR, [D-Asp3]MCYST-RR, [Dha7]MCYST-RR, and [D-Asp3,Dha71MCYST-RR. This is the first time that isolation of these toxins from Oscillatoria spp., with the exception of [D-Asp3jMCYST-RR, has been reported. Three of the strains produced a new microcystin, and the structure was assigned as [D-Asp3,Mser7JMCYST-RR. The structures of two new microcystins, produced as minor components by one Oscilatoria strain, could not be determined because of the small amounts isolated from the cells. Four strains produced [Dha71MCYST-RR as the main toxin, but [D-Asp3jMCYST-RR was

Structural Diversity, Characterization and Toxicology of Microcystins

“…Amino acids can then be derivatized with a UV absorbent tag and analyzed by reverse phase LC-UV [83]. Alternatively, they can be derivatized with trifluoroacetic anhydride to make them volatile and then analyzed by gas chromatography [114]. When chiral stationary phases or derivatizing agents are used, it is possible to determine the absolute configuration of the amino acids, which is not possible by MS or NMR alone.…”

“…However, Marahiel et al [186] suggested that the concomitant biosynthesis of Dha-and Mdha-containing MC variants could also be the result of the limitation of SAM, the source of the N-methyl group. Such mixtures of MCs containing both Mdha and Dha are common in Planktothrix [114] and Microcystis [139], and partial inactivation of the NMT domain may be a widespread feature of MC biosynthesis.…”

Chemistry and Biology of the Aeruginosin Family of Serine Protease Inhibitors

“…They have been named as such owing to the cyan color of the algae from which they are derived. Hepatotoxic cyclic peptides such as the microcystins5–7 and nodularins8, 9 are largely responsible for the health risks associated with these algal blooms 10–12. Reports of contaminated water supplies and outbreaks of livestock poisoning have motivated researchers to more closely examine the compounds produced by freshwater blue‐green algae.…”

Aeruginosine: Chemie und Biologie der Serinprotease‐Inhibitoren

“…Ihr Name leitet sich von der Cyanfarbe der Algen ab, die diese Wasserblüten bilden. Enthaltene hepatotoxische cyclische Peptide wie die Microcystine5–7 und Nodularine8, 9 sind die Hauptursachen für die gesundheitlichen Risiken beim Umgang mit den Blüten 10–12. Berichte über kontaminierte Wasservorräte und über die Vergiftung von Tierbeständen gaben Anlass, die von Frischwasser‐Blaualgen produzierten Substanzen näher zu untersuchen.…”