| Summary: | Amphibian skin secretions are abundant in bioactive compounds, especially antimicrobial peptides. These molecules are generally cationic and rich in hydrophobic amino acids, have an amphipathic structure and adopt an α-helical conformation when in contact with microorganisms membranes. In this work, we purified and characterized Figainin 1, a novel antimicrobial and antiproliferative peptide from the cutaneous secretion of the frog <i>Boana raniceps</i>. Figainin 1 is a cationic peptide with eighteen amino acid residues—rich in leucine and isoleucine, with an amidated C-terminus—and adopts an α-helical conformation in the presence of trifluoroethanol (TFE). It displayed activity against Gram-negative and especially Gram-positive bacteria, with MIC values ranging from 2 to 16 µM, and showed an IC<sub>50</sub> value of 15.9 µM against epimastigote forms of <i>T. cruzi</i>; however, Figanin 1 did not show activity against <i>Candida</i> species. This peptide also showed cytolytic effects against human erythrocytes with an HC<sub>50</sub> of 10 µM, in addition to antiproliferative activity against cancer cells and murine fibroblasts, with IC<sub>50</sub> values ranging from 10.5 to 13.7 µM. Despite its adverse effects on noncancerous cells, Figainin 1 exhibits interesting properties for the development of new anticancer agents and anti-infective drugs against pathogenic microorganisms.
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