Characterization of Structure and Biological Activity of Cyclotide Mram 4: A Plant-Derived Peptide

Abstract

Cyclotides are a class of peptides generated from plants that exhibit a wide range of biological activity. This study seeks to isolate and characterize cyclotide mram 4 from the stem of Vietnamese Viola dalatensis Gadnep, employing extraction with 50% acetonitrile in miliQ-water containing 1% formic acid, followed by salt precipitation, RP-HPLC, LC–MS, and LC–MS/MS methods. A mixture of cyclotides and mram 4 shown significant antibacterial efficacy against Bacillus subtilis and Listeria ivanovii. The MIC results demonstrated the inhibitory effect of mram 4 on the growth of the specified bacteria, producing values of 0.63 µM for both B. subtilis and L. ivanovii. L. ivanovii is a strain that has not been previously examined in relation to cyclotides. The results show that a cyclotide mixture exhibits α-amylase inhibitory activity (IC₅₀ = 32.65 ± 0.55 mg/mL), indicating its potential for future antidiabetic applications. The homological model of the 3D structure of mram 4 was constructed utilizing AlphaFoldDB structures as templates inside the SWISS-MODEL homology modeling framework.