Characterization and diversity of cyano-bacterial hepatotoxins (Microcystins) in blooms from polish freshwaters identified by liquid chromatography-electrospray ionisation mass spectrometry

Microcystins were determined in 36 cyanobacterial (blue-green algal) bloom samples dominated by Microcystis aeruginosa, Aphanizomenon flos-aquae and Nostoc spp. The analysed samples were collected from 8 water bodies in Poland during summers of 1996-2001. Ten microcystins (MC), three major and seven minor variants, were detected in natural cyanobacterial samples by high-performance liquid chromatography (HPLC). The structures of the microcystins were assigned on the basis of liquid chromatography-electrospray ionisation mass spectrometry (LC-ESI-MS). The main microcystins detected in the blooms from Polish freshwaters were MC-LR, MC-RR and MC-YR. Microcystin content of the blooms varied from a few μg g^-1 to 1687 μg g^-1 freeze-dried material. Also some monodesmethyl (dm) and didesmethyl (dmdm) variants of MC-LR, MC-RR, MC-YR were found in a few analysed samples. Furthermore, two compounds were tentatively characterised as MC-(H₄)YR and dm-MC-FR.