Microcystins: Toxicological Profile

Abstract

Cyanobacteria are ubiquitous photosynthetic prokaryotic organisms, which can form blooms and scums in surface water, characterized by a wide morphological variability. Different cyanobacteria strains, i.e., Microcystis, Planktothrix and Anabaena spp., produce microcystins (MCs), a group of more than 100 different structural variants of toxic cyclic heptapeptides, with a common cyanobacteria- specific amino acid, Adda. MC variants differ from each other for amino acid substitutions in positions 2 and 4 (where MC-LR has leucine (L) and arginine (R), respectively) and other changes. Humans may be exposed to MCs through the oral route, by ingestion of contaminated drinking water or food (including dietary supplements) or water during recreational activities. Dermal/inhalation and parenteral exposure may also occur, the latter due to the use of contaminated water for hemodialysis, leading to fatal outcome. The acute hepatotoxicity is congener specific (range of intraperitoneal LD50 in mice: 50–1200 μg/kg body S.