Toxic compounds produced by cyanobacteria belonging to several species of the order Nostocales: A review

Abstract Cyanobacteria are well recognised as producers of a wide range of natural compounds that are in turn recognised as toxins that have potential and useful applications in the future as pharmaceutical agents. The order Nostocales, which is largely overlooked in this regard, has become increasingly recognised as a source of toxin producers including Anabaena , Nostoc , Hapalosiphon , Fischerella , Anabaenopsis , Aphanizomenon , Gloeotrichia , Cylindrospermopsis , Scytonema , Raphidiopsis , Cuspidothrix , Nodularia , Stigonema , Calothrix , Cylindrospermum and Desmonostoc species. The toxin compounds (i.e., microcystins, nodularin, anatoxins, ambiguines, fischerindoles and welwitindolinones) and metabolites are about to have a destructive effect on both inland and aquatic environment aspects. The present review gives an overview of the various toxins that are extracted by the order Nostocales. The current research suggests that these compounds that are produced by cyanobacterial species have promising future considerations as potentially harmful algae and as promising leads for drug discovery.