Isolation and functional characterization of an antifungal hydrophilic peptide, Skh-AMP1, derived from Satureja khuzistanica leaves

The increasing resistance of pathogenic fungi to conventional antifungal therapies is a major global health concern. Currently, antifungal peptides are receiving increasing attention as suitable candidates for antifungal drug discovery. In the present study, an antifungal peptide was isolated from Satureja khuzistanica by reverse phase-HPLC column and sequenced by de novo sequencing and Edman degradation. The peptide cytotoxicity on human red blood cells and HEK293 cells was assessed using hemolytic and MTT assays. The purified peptide had 25 amino acids with pI and net charge equal to 9.31 and + 2, respectively. According to the systematic nomenclature, this peptide was named Skh-AMP1. The peptide showed strong antifungal activity against pathogenic species of Aspergillus and Candida with MIC values of 19.8-23.4 μM and MFC values of 39.6-58.5 μM. Molecular modeling analysis predicted a α-helix conformation for Skh-AMP1 and the probable hydrophilic residues and hydrophobic regions in the peptide structure which may responsible for its antifungal activity. Skh-AMP1 preserved its stability at the pH of 7 and 8 and the temperatures of 30 and 40 °C. The peptide showed negligible hemolytic activity in the range of 0.19-2.1% at the concentrations of 3.6-72 μM. It has no obvious cytotoxicity against HEK293 cells at the MIC of 25.2 μM for the fungal growth. All together, these properties make Skh-AMP1 as a previously undescribed peptide a promising potential therapeutic agent to combat immerging fungal infections.