Sixteen subfractions have resulted from this flash chromatography step; these were then analyzed by LC-HRESIMS. The m/z values for major microginins were detected in subfractions 2-12. These were again pooled and fractionated by reverse-phase HPLC using a semi-preparative ACE 10 C18-AR (250 × 10 mm) column. The chromatography was carried out at 3 mL min -1 flow at 30 ºC with iPrOH (solution A), water (solution B) and acetonitrile (solution C). Samples were eluted by a linear gradient of B and C, from 0% to 66.6% of solution C, over 20 minutes. This was followed by a linear gradient of A and B solutions, from 0% to 70% of solution A over 5 minutes, then held at 70% solution A for 1 minute, before returning to initial conditions. This chromatography yielded 16 fractions and after LC-HRESIMS analysis the target compounds indicated that the interaction with the stationary phase was poor and that the compounds eluted mostly in the baseline, which had also been collected (130 mg). This fraction solubilized poorly in common HPLC solvents or their mixtures, so a liquid-liquid extraction (2× H2O/EtOAc, 1:1, v/v) was performed. The aqueous layer was collected and showed precipitation. After filtration, the precipitate could be dissolved in a 1:1 mixture (v/v) of iPrOH/H2O. LC-HRESIMS analysis showed that several microginins were present and abundant in both the filtered aqueous layer and in the solubilized precipitate. We used the aqueous