Decomposition of Microcystin-LR, Microcystin-RR, and Microcystin-YR in Water Samples Submitted to in Vitro Dissolution Tests

Abstract

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

Transfer of microcystin from freshwater lakes to Puget Sound, WA and toxin accumulation in marine mussels (Mytilus trossulus)

“…Polyclonal Adda ELISA has been validated by several studies for MC screening in seafood tissues (Ernst et al, 2005;Moreno et al, 2004;Geis-Asteggiante et al, 2011). This method is commonly used for general MC analyses because it has good cross-reactivity with at least 80% of known MC variants due to the presence of 6E-Adda (Fischer, 2001).…”

Assessment of the factors contributing to the variations in microcystins biodegradability of the biofilms on a practical biological treatment facility

“…Concomitantly, the seasonal variations in both MC-degrader and overall bacterial abundance within the biofilms was determined by quantitative polymerase chain reaction (qPCR) assays, with mlrA and bacterial 16S rDNA genes acting as surrogates, respectively. Moreover, microcystin-RR (MCRR) and microcystin-YR (MCYR) are also found as common MCs variants produced by cyanobacteria in natural waters (Moreno et al, 2004). Supposing that other co-existing MCs variants could be one factor affecting the biodegradation of one MC alone, separate and simultaneous biodegradation of these MCs variants was thus compared, and time-dependent dynamics in mlrA and 16S rDNA gene copy number were monitored along these biodegradation processes.…”

In vitro biodegradation of cyanotoxins in the rumen fluid of cattle

“…Recently, MCs were detected in the serum (average 0.228 ng MC-LR eq/mL) of chronically exposed fishermen [13], which indicate that low dose exposure may be common in certain segments of the population. World Health Organization (WHO) has set the provisional drinking water guideline value at 1.0 μg/L for MC-LR [14]. …”