Diversity of hepatotoxic microcystins and bioactive anabaenopeptins in cyanobacterial blooms from Greek freshwaters

Microcystins (MCs) and anabaenopeptins from 26 cyanobacterial bloom samples dominated mainly by the genus Microcystis and collected from seven Greek freshwaters were identified and quantified by high-performance liquid chromatography coupled to a diode array detector. All the samples analyzed contained microcystins; in 27% of the samples anabaenopeptins were detected but not anabaenopeptilide (A). In each sample 1-7 microcystins and up to two anabaenopeptins (anabaenopeptins A and B) were identified. MC-RR and MC-LR were the predominant microcystins, followed by MC-YR. MC-LA and demethylated variants of MC-LR and MC-RR also were present but were not abundant. Total content of microcystin and anabaenopeptin varied from 40 to 2565 microg g(-1) freeze-dried material (mean 674.5 microg g(-1)) and from undetectable to 48 microg g(-1) freeze-dried material (mean 6.2 microg g(-1)), respectively. Qualitative and quantitative variation in the microcystins in the samples indicates there may be geographical trends in the distribution of microcystins. This study reports for the first time (1) the widespread occurrence of several different microcystins in Greek freshwaters and (2) quantitative data on the anabaenopeptins produced in natural cyanobacterial populations.