Enantioselective Toxicology of Chiral Agrochemicals

Chiral agrochemicals exist as non-superimposable mirror-image forms, or enantiomers, that often display markedly different biological activities, environmental fates and toxicological profiles. While racemic mixtures have traditionally been applied in agriculture, there is growing recognition that one enantiomer may be more efficacious against target pests while the other poses greater risk to non-target organisms, including wildlife and humans. Enantioselective toxicology examines these differential effects, encompassing absorption, distribution, metabolism and excretion (ADME) processes as well as specific modes of toxic action. Advances in chiral analytical methods have revealed that microbial communities, plant matrices and abiotic factors such as photolysis can preferentially transform one enantiomer, altering ecotoxicological risk. A comprehensive understanding of enantiomer-specific behaviour underpins more precise risk assessments, informs regulatory frameworks and can guide the development of single-enantiomer formulations with reduced environmental burden and improved safety margins.

Research from Nature Portfolio

Investigation into the environmental fate of a chiral aryloxyphenoxypropionate herbicide demonstrated rapid degradation of its active S-enantiomer in water-sediment microcosms, with half-lives of less than one day, whereas the R-enantiomer persisted longer. Subsequent breakdown products also exhibited enantioselective hydrolysis, implicating sediment microorganisms as key drivers of chiral transformation. These findings highlight that enantiomer-specific degradation pathways and persistence must be integrated into ecological risk models to predict long-term impacts on aquatic ecosystems.

Enantioselective Toxicology of Chiral Agrochemicals publication trend

The graph below shows the total number of articles in enantioselective toxicology of chiral agrochemicals across all publications each year (not limited to Nature Index journals).

Technical terms

Chirality: A molecular property whereby a compound exists in two non-superimposable mirror-image forms (enantiomers).

Enantiomer: One of two stereoisomers that are mirror images of each other and cannot be aligned by rotation.

Racemate: A 1:1 mixture of both enantiomers of a chiral compound, often exhibiting different overall bioactivity from individual enantiomers.

Enantioselectivity: The preference of a physical, chemical or biological process to interact with one enantiomer over the other, leading to unequal rates of reaction or transformation.

References

1. Environmental Fate of Chiral Herbicide Fenoxaprop-ethyl in Water-Sediment Microcosms. Scientific Reports (2016).
2. Identifying Metabolic Perturbations and Toxic Effects of Rac-Metalaxyl and Metalaxyl-M in Mice Using Integrative NMR and UPLC-MS/MS Based Metabolomics. International Journal of Molecular Sciences (2019).
3. Mechanistic Insights into Stereospecific Antifungal Activity of Chiral Fungicide Prothioconazole against Fusarium oxysporum F. sp. cubense. International Journal of Molecular Sciences (2022).