Optimization of intracellular microcystin extraction for their subsequent analysis by high-performance liquid chromatography

Microcystins are a family of heptapeptide hepatotoxins produced by some genera of cyanobacteria. These toxins have been responsible for the illness and death of both animals and humans. Due to their hazard to human health, extraction of all intracellular microcystin variants is required to characterize and quantify all microcystins present in a sample. To date, there is little work reported comparing results obtained with different extraction methods. Findings reported to date indicate that selection of solvent will vary depending on sample and its microcystin contents. In the present work, a wide range of extraction volumes and solvents were evaluated over a range of pH and extraction times in order to optimize a suitable method for the extraction of a wide range of microcystins. The number of extractions required was also studied. This study was carried out using mainly two laboratory cultures which contain microcystin variants with quite different hydrophobicities. This is the first time that the most commonly used solvents for intracellular microcystin extraction have been studied in detail.