Extraction of cyanostatins and their analysis, with microcystins and anabaenopeptin A, in a 21-year archive of cyanobacterial bloom samples
Codd, Geoffrey A.; Morrison, Louise F.; Nath, Matish; Sano, Tomoharu; Kaya, Kunimitsu
Cyanobacteria produce a large number of bioactive peptides. In addition to the well-characterized hepatotoxic microcystins, other cyanobacterial peptides may contribute to the biological activity of cyanobacterial blooms. Until recently, information has been lacking on the environmental concentrations of these non-microcystin peptides and it has not been possible to assess their ecological impacts and potential risks at relevant concentrations.Optimized methods for the routine extraction of two cyanobacterial peptides, cyanostatins A and B, were developed and applied to the extraction and HPLC analysis of bloom samples which had been collected, lyophilized and stored from a single freshwater lake over 21 years. Samples were also analysed for microcystins and anabaenopeptin A, using quantitated standards in all cases. The maximal concentration of cyanostatin A was 6 times higher than the highest microcystin concentration in samples taken over the 21-year period. No non-microcystin cyanopeptides were detected until samples taken in 1992, although microcystins were present when neither cyanostatins nor anabaenopeptin A were detectable, and vice versa. Possible explanations include differences in the stability of non-microcystin cyanopeptides versus microcystins, but more likely is that differences are also due to alterations in total cyanopeptide pools due to heterogeneity and succession of cyanobacterial bloom composition.