ELISA and LC-MS/MS methods for determining cyanobacterial toxins in blue-green algae food supplements

The use of natural products as a diet supplement is increasing worldwide but sometimes is not followed by adequate sanitary controls and analyses. Twenty samples of pills and capsules of lyophilised cyanobacteria (blue-green algae), commercialised in Italy as dietary supplements, were found positive at the Vibrio fischeri bioassay. Further analyses with ELISA and LC-MS/MS methods revealed the presence of four microcystin (MC) analogues, MC-LR, -YR, -LA, -RR and two demethylated forms of MC-RR. The highest total microcystin content was 4.5 and 1.4 microg g-1 in pills and capsules, respectively. The ELISA measurements, compared to the LC-MS/MS analyses, showed significantly lower concentrations of microcystins in pills, this confirming a possible ELISA underestimate of mixed microcystins, due to different sensitivities for some toxic analogues.