Toxins and bioactive compounds from cyanobacteria and their implications on human health

Many species of cyanobacteria (blue-green algae) produce secondary metabolites with potent biotoxic or cytotoxic properties. These metabolites differ from the intermediates and cofactor compounds that are essential for cell structural synthesis and energy transduction. The mass growth of cyanobacteria which develop in fresh, brackish and, marine waters commonly contain potent toxins. Cyanobacterial toxins or cyanotoxins are responsible for or implicated in animal poisoning, human gastroenteritis, dermal contact irritations and primary liver cancer in humans. These toxins (microcystins, nodularins, saxitoxins, anatoxin-a, anatoxin-a(s), cylindrospermopsin) are structurally diverse and their effects range from liver damage, including liver cancer to neurotoxicity. Several incidents of human illness and more recently, the death of 60 haemodialysis patients in Caruaru, Brazil, have been linked to the presence of microcystins in water. In response to the growing concern about the non-lethal acute and chronic effects of microcystins, World Health Organization has recently set a new provisional guideline value for microcystin-LR of 1.0 microg/L in drinking water. Cyanobacteria including microcystin-producing strains produce a large number of peptide compounds, e.g. micropeptins, cyanopeptolins, microviridin, circinamide, aeruginosin, with varying bioactivities and potential pharmacological application. This article discusses briefly cyanobacterial toxins and their implications on human health.