Computationally designed AOPP herbicide compounds targeting echinochloa with improved selectivity and safety

Overview

This research delivers a set of computationally designed herbicide candidates built around the cyhalofop-butyl pharmacophore, an aryloxyphenoxypropionate (AOPP) class herbicide widely used for post-emergence grass control in rice. Cyhalofop-butyl works by inhibiting acetyl-CoA carboxylase (ACCase), a key enzyme in fatty acid biosynthesis, and shows natural selectivity between Echinochloa (barnyard grass) species and rice.

The work leverages this selectivity by designing novel molecular derivatives that improve binding efficiency to ACCase in target weeds while remaining safe for rice. Using both ligand-based and structure-based pharmacophore modeling, the team identified 16 compounds with stronger predicted interactions than cyhalofop-butyl. These candidates were further validated through 100 ns molecular dynamics simulations and complete in-silico safety profiling to assess potential human exposure risks. The result is a shortlist of promising lead molecules positioned as next-generation, high-selectivity herbicides for rice cultivation systems.

Technical specifications

Core approach:

• Pharmacophore-based design using the cyhalofop-butyl template as a structural starting point
• Dual ligand-based and structure-based pharmacophore modeling to capture key interaction features
• Molecular docking followed by MM-GBSA binding energy calculations to rank candidates
• 100 ns molecular dynamics simulations to confirm binding stability and interaction profiles
• Comprehensive in-silico safety and toxicity profiling for human exposure assessment

Key features:

• 16 lead compounds identified with improved predicted binding to ACCase compared to the parent herbicide
• Designed to exploit the differential ACCase sensitivity and metabolic activation between barnyard grass and rice
• Potential for broad-spectrum activity through machine learning-informed optimization of the pharmacophore
• Computational evidence supporting both target potency and reduced non-target toxicity

Planned experimental validation:

• Plant material collection and standardized seed pretreatment protocols
• Greenhouse efficacy testing at maximum recommended label field rates applied at the 3–4 leaf growth stage
• Dosage-response studies to determine GR50 values (herbicide dose producing 50% reduction in dry weight)

Technology readiness level

The technology is currently at an early-to-mid stage of development, corresponding to a TRL of approximately 3–4. The lead compounds have been identified and prioritized through rigorous in-silico methods, including pharmacophore modeling, docking, binding free energy analysis, MD simulations, and computational safety profiling. These results provide strong preliminary evidence of improved target engagement and selectivity.

The next critical step is laboratory validation, including in vitro enzyme assays against ACCase and greenhouse plant trials to confirm herbicidal efficacy, crop safety, and dose-response behavior. Successful completion of these planned studies would establish proof of concept and enable progression toward formulation development, field trials, and potential licensing or co-development partnerships with agrochemical companies.