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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

SummaryHigh-performance liquid chromatography (HPLC) and different high-performance capillary electrophoresis (HPCE) methods have been developed for the detection and quantitation of cyanobacterial toxins in environmental samples.Cyanobacteria, also known as blue-green algae, are responsible for toxic contamination of fresh water. Several serious episodes involving microcystins have been reported in recent years; the most common and toxic of these hepatotoxins is microcystin-LR (MC-LR). Sensitive analytical methodologies are required for determination of these compounds because of the implications for human health when the toxins are present in drinking water.Different modes of operation of HPCE were used and the results obtained were compared with those obtained by HPLC. Citrate buffer resulted in good separation of the microcystins when capillary electrophoresis was used in capillary zone electrophoresis (CZE) and capillary isotachophoresis (CITP) modes; borate buffer containing sodium dodecyl sulphonate (SDS) was used in micellar electrokinetic chromatography (MEKC). Conditions were optimized and the methods were applied to water samples and cyanobacterial cells containing microcystins. Results obtained by use of HPLC-UV and different modes of operation of CE-UV were compared in terms of sensitivi~,, selectivi~,, and efficiency.

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