Antifungal activity of synthetic peptides derived from Impatiens balsamina antimicrobial peptides Ib-AMP1 and Ib-AMP4

Seeds of Impatiens balsamina contain a set of related antimicrobial peptides (Ib-AMPs). We have produced a synthetic variant of Ib-AMP1, oxidized to the bicyclic native conformation, which was fully active on yeast and fungal strains; and four linear 20-mer Ib-AMP variants, including two all-d forms. We show that the all-d variants are as active on yeast and fungal strains as native peptides. In addition, fungal growth inhibition nor salt-dependency of Ib-AMP4 could be improved by more than two-fold via replacement of amino acid residues by arginine or tryptophan. Native Ib-AMPs showed no hemolytic nor toxic activity up to a concentration of 100 μM. All these data demonstrate the potential of the native Ib-AMPs to combat fungal infections.