Isolation and Analysis of Pharmacologically-Active Peptides of Microcystis Flos-Aquae
Cyanobacteria are recognized as a rich source of pharmacologically important secondary metabolites. Vigorous screening programs have identified numerous species that synthesize cytotoxic compounds responsible for growth inhibition of bacteria, viruses, fungi and other algal species. These bioactive metabolites represent a class of alternative, natural pharmaceuticals, to combat the rising number of drug-resistant pathogens.
Non-toxic Microcystis flos-aquae biomass was collected from the Torrens River, South Australia, and assessed for growth inhibition of bacteria and viruses. Methanol extracts exhibited strong antimicrobial activity against Staphylococcus aureus, indicated by clear zones of 3-4 mm in bacterial lawns. Antiviral activity was observed against Dengue virus and Respiratory Syncytial virus (RSV) by the same extracts; however, due to differences in infection mechanisms by bacteria and viruses, it is probable the inhibitory activity is caused by separate compounds. A peptide profile of the extract was constructed using MS-MS, and the sample fractionated by HPLC, with each fraction reassessed for activity. Active fractions were analysed by 2D NMR and the structure and functional groups of the compounds determined.