Some cyanobacterial species can produce different types of bioactive peptides (cyanopeptides), such as aeruginosins, cyanopeptolins, microginins, microviridins, anabaenopeptins and microcystins. Microcystins are well known in the scientific literature as hepatotoxins that inhibit phosphatases type 1 and 2A. Microginins are reported as inhibitors of the angiotensin-converting enzyme (ACE) and other proteases, being important candidates for the development of anti-hypertensive compounds. Nevertheless, the physiological functions of these compounds have not been fully elucidated and limited information concerning the production of these classes of molecules by cyanobacteria is available, especially in Brazil. Therefore, the investigation of cyanopeptides is relevant both for their ecotoxicological effects as well as for their pharmacological potential.The aim of this study is to isolate and identify cyanopeptides, namely microginins, produced by cyanobacteria strains isolated from reservoirs in the State of São Paulo (Billings, Guarapiranga and Salto Grande in Americana-SP). Cyanobacterial extracts will be prepared from cultures cultivated under laboratory conditions. The extracts will be fractionated by solid phase extraction and reversed-phase chromatography and the obtained fractions will be tested in order to verify the inhibition of proteases. Fractions demonstrating inhibitory activity will be further purified by semi-preparative high performance liquid chromatography for the structural determination of cyanopeptides.Initial studies have been performed by our group and the production of microginins was confirmed in some strains that are already maintained in the laboratory. We believe that our results will contribute to the identification of the main protease inhibitors produced by Brazilian cyanobacterial strains.
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