LC-High Resolution MSn and LC-Tandem mass spectrometry for a data merging of a Greek cyanobacteria biomass from Lake Kastoria

Microcystins (MCs) are a large group of structurally related compounds produced by cyanobacteria belonging to different genera, including the planktonic Microcystis, Planktothrix, Anabaena species, and the benthic Oscillatoria. There are more than 240 cyclic peptides and they have often been implicated in accidental human and animal poisonings along lake and estuarine shores. Nodularins are other cyanobacterial toxins produced by the species Nodularia spumigena sharing structural features with MCs, which occurs in brackish waters, essentially in the Baltic Sea, Australia, and New Zealand. All these compounds are potent inhibitors of serine/threonine protein phosphatases 1 and 2A, with hepatocytes being their final molecular target. A number of cyanopeptolins and micropeptines are known from literature to be produced by cyanobacteria, some of them toxic too. In the present study we analyzed a biomass sample collected in September 2014 from Lake of Kastoria (Greece) during a cyanobacterial bloom by using two different approaches: a targeted analysis by LC-tandem mass spectrometry at unit resolution and an untargeted approach by LC-High resolution LTQ Orbitrap MSn. A good correlation between the two approaches emerged but from untargeted analyses the presence of some MC variants that were not detected by LC-MS/MS emerged together with the presence of potentially new cyanopetolins.