The presence of cyanobacterial toxins (microcystins) in waters and food increases the risk of toxicity
to animal and human health. These toxins can degrade in the human gastrointestinal tract before
they are absorbed. To evaluate this possible degradation, water samples spiked with known
concentrations of microcystins MC-LR, MC-RR, and MC-YR, which are the toxins most commonly
produced by such toxic cyanobacteria as Microcystis aeruginosa, Oscillatoria spp., and Nostoc spp.,
were submitted to a dissolution test that used gastric and intestinal fluids according to U.S.
Pharmacopeia conditions. HPLC with UV detection was used to determine the toxins before and
after treatments. This study revealed enzymatic alterations in gastric conditions for all the toxins
assayed. MC-RR was the toxin most affected: its range of inactivation was 49−64%. The percentage
of degradation for MC-YR and MC-LR was around 30%. However, none was degraded by intestinal
digestion.
Keywords: Microcystins; MC-LR; MC-RR; MC-YR; gastrointestinal fluids; dissolution test
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