Optimization of a Microcystin Extraction Protocol for Blue-Green Algae-Based Dietary Supplements

Blue-green algae as dietary supplements are used for their reported health benefits. Outdoor harvested algae can be contaminated by cyanobacteria producing harmful secondary metabolites, including microcystins (MCs). MCs are a group of hepatotoxic cyclooligopeptides that inhibit the function of protein phosphatases in eukaryotes. Development of a routine monitoring protocol is necessary due to the concern for human health. MC quantification in dietary supplement are subject to interferences from compounds present in the supplement. Herein, algal tablets and capsules were used to evaluate cleanup and analytical protocols to improve the accuracy of MC quantification. Two solid-phase extraction (SPE) cartridges (i.e., Bond-Elute and Oasis HLB) and two types of dispersive SPE media were tested for cleanup. Eight MCs (i.e., MC-LA, -LF, -LR, -LW, -LY, -RR, -YR, and nodularin-R) were spiked into pre- and post-cleanup processes. Samples were loaded onto two C18-based liquid chromatography columns for comparison on column specificity. MC quantification were determined using a QTrap mass spectrometer. The eight MCs can be grouped by the retention time into R-group (i.e., MC-LR, MC-RR, MC-YR and nodularin-R) and L-group (MC-LA, -LF, -LW, and -LY). Overall, L-group MCs were more susceptible to interfering compounds than R-group MCs even with these cleanup processes.