The use of antimicrobial peptides as agents of food additives, cosmeceuticals and preservatives is becoming increasingly popular. This research reported the design of nine de novo peptides (P1P9) and their activities against seven bacterial strains together with their antioxidant and hemolytic activities. The secondary structure of two of these peptides (P8 and P9) was also studied as well as their effects on the membrane of Staphylococcus epidermidis. The results showed that the 12 amino acid residue peptides, P8 and P9, had eight positive charges, 50% hydrophobic ratio, and 1.61 Boman index. However, their amino acid sequence and hydrophobic facet sizes were different. P8 and P9 displayed no toxicity against human red blood cells at their minimum inhibitory concentrations required to inhibit the bacterial growth of at least 90% of organisms (MIC90) against Staphylococcus epidermidis and Staphylococcus aureus. P8 and P9 resulted in S. epidermidis cell blebs. The Circular dichroism spectra of P8 and P9 revealed that their structures in 50% trifluoroethanol (TFE) were more ordered indicating the possibility of structural change in the antibacterial mechanism. Moreover, all designed peptides had antioxidant activity. All peptides except P9 had low toxicity against human red blood cells and less than 5% at concentrations higher than their half maximal inhibitory concentration (IC50) approximately more than 830 times. P8 and P9 are interesting to further develop as antibiotic agents. Moreover, all peptides are interesting for antioxidant applications.
Key words: Antibacterial peptide, Antioxidant peptide, Antibacterial peptide design, Short peptides, Hemolysis
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