We have previously reported peptides composed of sequential arginine (R) residues paired with tryptophan (W) or 3,3-diphenyl-L-alanine residues (Dip), such as cyclic peptides [RW] and [R(Dip)], as antibacterial agents. Herein, we report antibacterial and antifungal activities of five linear peptides, namely ((DipR)(WR)), ((DipR)(WR)), ((DipR)(WR)), ((DipR)(WR)), and (DipR)R, and five cyclic peptides [(DipR)(WR)], [(DipR)(WR)], [(DipR)(WR)], [(DipR)(WR)], and [DipR], containing alternate positively charged R and hydrophobic W and Dip residues against fungal, Gram-positive, and Gram-negative bacterial pathogens. The minimum inhibitory concentrations (MICs) of all peptides were determined by the micro-broth dilution method against , , , , , , , , and . Fungal organisms were , , and [DipR] and ((DipR)(WR)) showed MIC values of 0.39-25 ��M and 0.78-12.5 ��M against Gram-positive and Gram-negative bacteria strains, respectively. The highest activity was observed against with MIC values of 0.39-0.78 ��M among tested compounds. [DipR] demonstrated MIC values of 6.6 ��M against and 1.6 ��M against , whereas fluconazole showed MIC values of 3.3 ��M and >209 ��M, respectively. These findings highlight the potential of these peptides as broad-spectrum antimicrobial agents.
