Small and Versatile Cyclotides as Anti-infective Agents

Plants provide an abundant source of potential therapeutic agents, including a diverse array of compounds, such as cyclotides, which are peptides known for their antimicrobial activity. Cyclotides are multifaceted molecules with a wide range of biological activities. Their unique topology forms a head-to-tail cyclic structure reinforced by a cysteine knot, which confers chemical and thermal stability. These molecules can directly target membranes of infectious agents by binding to phosphatidylethanolamine in lipid membranes, leading to membrane permeabilization. Additionally, they function as carriers and cell-penetrating molecules, demonstrating antiviral, antibacterial, antifungal, and nematicidal properties. The structure of cyclotides is also amenable to chemical synthesis, facilitating drug design through residue substitutions or grafting of bioactive epitopes within the cyclotide scaffold to enhance peptide stability. In this review, we explore the multifunctionality of these biomolecules as anti-infective agents, emphasizing their potential as a novel class of antimicrobial drugs.