Synthesis of linear and cyclic peptides with N-MeAA as sustainable herbicides

Overview

This research focuses on the design, synthesis, and biological evaluation of linear and cyclic peptides containing N-methyl amino acids (N-MeAA) as sustainable herbicide candidates. Natural cyclopeptides and their synthetic analogs have demonstrated herbicidal, fungicidal, and insecticidal activity. By incorporating N-MeAA into peptide structures, the project aims to enhance cell permeability and chemical stability, key factors for agrochemical performance. The lead compounds, including the natural product Versicotide D and synthetic cyclotetrapeptides, have shown significant phytotoxic activity and low cytotoxicity, positioning them as promising leads for environmentally friendly weed management.

Technical specifications

Synthesis approach:

• Solid Phase Peptide Synthesis (SPPS) for linear peptide assembly
• On-resin or solution-phase macrocyclization using oxima resin and 2-chloro trityl resin
• Preparation of at least 30 cyclopeptides and corresponding open-chain precursors, ranging from 4 to 6 amino acid residues
• Incorporation of L-, D-, and N-methylated amino acids to explore stereochemical and structural effects on bioactivity

Key bioactive results:

• Versicotide D: 74% radicle growth inhibition at 67 μg/mL against Rye grass, with low cytotoxicity on HepG2 cells and inhibitory activity against cyanobacteria
• Cyclotetrapeptides containing one or two N-MeAA residues: 53% and 62% growth inhibition at 9 and 10 μM, respectively
• Cyclic penta- and hexapeptides showing bioactivity with statistical significance

Planned characterization and evaluation:

• Physicochemical profiling: solubility, LogP, and permeability
• Herbicidal evaluation against multiple weed species with statistical analysis
• Phytotoxicity assessment on crops and selectivity index determination
• Post-emergence herbicidal activity testing
• Structure-activity relationship (SAR) studies and hit class optimization

Technology readiness level

The technology is at an early-to-mid stage of development. Lead cyclopeptide candidates have been synthesized and validated in laboratory bioassays, demonstrating reproducible phytotoxic activity against Rye grass and inhibitory effects on cyanobacteria. The research team has established synthetic protocols for both linear and cyclic peptides and has prepared a library of over 30 compounds. Next steps include expanded physicochemical characterization, broader weed-spectrum evaluation, crop selectivity profiling, and SAR-guided optimization to advance candidates toward field-ready herbicide development. The program is open to collaboration on additional bioassays and translational studies.