prapasin

Prapasin is a naturally occurring antimicrobial peptide isolated from the aerial parts of the medicinal herb *Prapasius officinalis*, a perennial plant native to the temperate regions of Eastern Asia. The peptide consists of 34 amino acids and contains six cysteine residues that form three intramolecular disulfide bonds, giving it a compact, globular three-dimensional structure characteristic of the defensin protein family. Mass spectrometry and NMR analysis revealed that prapasin adopts a triple-stranded β-sheet fold with a β‑turn at the C‑terminus. The sequence alignment shows high similarity to thionin‑like peptides found in other dicotyledonous species, indicating a conserved evolutionary origin.

Functional studies of prapasin demonstrate broad-spectrum antibacterial activity, with minimum inhibitory concentrations ranging from 2 to 5 µg mL⁻¹ against *Staphylococcus aureus* and *Escherichia coli*. In addition, the peptide exhibits moderate activity against fungal pathogens such as *Candida albicans* and *Botrytis cinerea*. In vitro cytotoxicity assays indicate that prapasin selectively permeabilizes bacterial membranes while sparing mammalian cells, suggesting potential utility in topical antimicrobial formulations. The mode of action is thought to involve induction of pore formation in the microbial lipid bilayer, leading to ion dysregulation and cell death.

Since its initial discovery in 2018, prapasin has attracted interest for use as a lead compound in the development of new antimicrobial agents. Researchers are exploring synthetic analogues with improved stability and potency, as well as exploring its application in plant protection to reduce dependence on conventional fungicides. Current studies have also examined the peptide’s immunomodulatory properties, revealing that prapasin can stimulate cytokine production in macrophages, thereby enhancing innate immune responses.