Stereoselective bioaccumulation and dissipation of pyrisoxazole in earthworm-soil microcosm

Efficacy, Residue Risk, and Soil Ecosystem Safety of Butylidenephthalide for the Control of Peanut Stem Rot

Peanut stem rot caused by Sclerotium rolfsii is becoming increasingly severe. Although butylidenephthalide exhibits great antifungal activity against S. rolfsii, its appropriate application strategy is unclear. Greenhouse experiments suggested that butylidenephthalide was suitable to be preventatively applied by root drenching at 400 mg/L for three times with an interval of 7 days. In field trials, butylidenephthalide exhibited an efficacy of 51.75% after 21 days and increased the peanut yields by 9.89%. Butylidenephthalide rapidly dissipated in soil and plants (t1/2 = 2.28-3.41 d), with no residues detected in edible peanut kernels or haulms at harvest. Butylidenephthalide showed a strong uptake and accumulation ability in plants from the soil (root concentration factor/bioconcentration factor > 1) and a moderate upward conductivity from roots to the above-ground parts (TFstem+leaf = 0.95). Butylidenephthalide exhibited low earthworm toxicity and stimulated bacterial/actinomycete populations while suppressing fungi in soil. Overall, butylidenephthalide showed a favorable efficacy, no residue risks, and high safety on the soil ecosystem in the control of peanut stem rot.

Enantioseparation, bioactivity, environmental fate and toxicity of chiral triazole fungicide ipconazole in soil and earthworm

Ipconazole (IPC) is a chiral triazole fungicide and commonly used for disease control in seeds. This study investigated the bioactivity and potential mechanism of ipconazole against pathogenic microorganisms at the chiral perspective. It explored the accumulation behavior of ipconazole enantiomers within the soil-earthworm system and evaluated its toxic effects on earthworms. Bioactivity evaluation revealed that the bioactivity order of ipconazole against three plant pathogens is (-)-1S,2 R,5S-IPC > rac-IPC > (+)-1R,2S,5R-IPC, and the bioactivity of (-)-1S,2 R,5S-IPC is 34.6-129.5 times higher than that of (+)-1R,2S,5R-IPC. Molecular docking found that (-)-1S,2 R,5S-IPC has a stronger binding affinity for the target protein CYP51 to cause activity differences. Accumulation and metabolism studies revealed that (-)-1S,2 R,5S-IPC is more persistent than that of (+)-1R,2S,5R-IPC, and ipconazole was primarily metabolized into hydroxylated ipconazole through hydroxylation in the soil-earthworm system. Toxicological evaluation found growth inhibitory effects and histopathological damage to earthworms at an exposure concentration of 1.5 mg kg-1 ipconazole. Further investigation indicated that these toxic effects of ipconazole were caused by inducing oxidative damage and influencing the functional gene expression of related growth. These research findings will further enhance the understanding of the activity and risks of ipconazole enantiomers, contributing to the safer use of ipconazole in the agricultural environment.

Enantioselective bioaccumulation, biotransformation and spatial distribution of chiral fungicide difenoconazole in earthworms (Eisenia fetida)

The enantioselective environmental behavior of difenoconazole, a widely utilized triazole fungicide commonly detected in agricultural soils, has yet to be comprehensively explored within the earthworm-soil system. To address this research gap, we investigated the bioaccumulation and elimination kinetics, degradation pathways, biotransformation mechanisms, spatial distribution, and toxicity of chiral difenoconazole. The four stereoisomers of difenoconazole were baseline separated and analyzed using SFC-MS/MS. Pronounced enantioselectivity was observed during the uptake phase, with earthworms exhibiting a preference for (2R,4R)-difenoconazole and (2R,4S)-difenoconazole. A total of five transformation products (TPs) were detected and identified using UHPLC-QTOF/MS in the earthworm-soil system. Four of the TPs were detected in both earthworm and soil, and one TP was produced only in eaerthwroms. Hydrolysis and hydroxylation were the primary transformation pathways of difenoconazole in both earthworms and soil. Furthermore, a chiral TP, 3-chloro, 4-hydroxy difenoconazole, was generated with significant enantioselectivity, and molecular docking results indicate the greater catalytic bioactivity of (2R,4R)- and (2R,4S)-difenoconazole, leading to the preferential formation of their corresponding hydroxylated TPs. Furthermore, Mass Spectrometry Imaging (MSI) was applied for the first time to explore the spatial distribution of difenoconazole and the TPs in earthworms, and the "secretory zone" was found to be the dominant region to uptake and biodegrade difenoconazole. ECOSAR predictions highlighted the potentially hazardous impact of most difenoconazole TPs on aquatic ecosystems. These findings are important for understanding the environmental fate of difenoconazole, evaluating environmental risks, and offering valuable insights for guiding scientific bioremediation efforts.

Stereoselective bioaccumulation and degradation of chiral pesticide hexythiazox in earthworm-soil microcosm

The chiral pesticide hexythiazox was extensively employed in agricultural activities and has garnered growing concern for its harmful impact on the ecosystem. This study investigates the toxicodynamic earthworm at the enantiomeric level of hexythiazox. Earthworms exhibited notable enantioselectivity during the accumulation stage. Furthermore, the presence of earthworms can impact the rate of degradation and enantioselectivity of hexythiazox in soil. The accumulation of the two hexythiazox enantiomers in the earthworm adhered to the one-compartment model, whereas the elimination phase was governed by the first-order kinetics equation. Furthermore, it was discovered that there was no notable enantioselectivity observed during the elimination phase.

Stereoselective bioaccumulation and dissipation of four stereoisomers of cyproconazole in earthworm-soil microcosm

Cyproconazole is a representative and widely used triazole fungicide with four stereoisomers, which will bring some risks to non-target organisms. A fast analytical method on supercritical fluid chromatography-tandem mass spectrometry was established in 4 min, and the environmental hazards of chiral cyproconazole were studied in earthworm-soil microcosm, including stereoselective bioaccumulation and dissipation. In the process of bioaccumulation, the concentrations of cyproconazole stereoisomers in earthworms showed a trend of increasing first and then reaching a stable state at 6 mg/kg treatment, which was different from those at 0.6 mg/kg treatment (decease-increase-equilibrium). The concentration order was (2S,3R)- > (2S,3S)- > (2R,3R)- > (2R,3S)-cyproconazole and (2S,3S)- ≈ (2S,3R)- > (2R,3R)- > (2R,3S)-cyproconazole at 6 and 0.6 mg/kg treatments, respectively. The bioaccumulation factor (BAF) values were in the range of 0.018-0.55, showing weakly relative accumulation capacity. The dissipation of cyproconazole stereoisomers in artificial soil accorded with the first-order kinetics equation, and the half-lives were 20.1-23.6 and 7.66-8.28 days at 6 and 0.6 mg/kg treatments, respectively, without stereoselectivity and diastereoselectivity. In earthworms, the dissipation half-lives were 5.81-6.01 days with the preferential dissipation of (2R,3R)-cyproconazole. The study would help with the rational uses and risk assessments of cyproconazole.