Enantioselective aquatic toxicity and degradation in soil of the chiral fungicide oxathiapiprolin

Evaluation of Chiral Pesticide Chlorbufam at the Enantiomeric Level: Absolute Configuration, Separation, Herbicidal Activity, and Degradation in Soil

Chlorbufam is a photosynthesis inhibitor chiral herbicide with a pair of enantiomers, which is rarely a concern. In this work, the optically pure enantiomers of chlorbufam were first synthesized and characterized, and the enantioselective herbicidal activity and mechanism were studied. Chlorbufam enantiomers showed significant differences in bioactivity against Echinochloa crus-galli and Abutilon theophrasti, and R-(+)-chlorbufam was identified as the most active against the targeted organisms with higher bioactivity of 3.95 and 1.71 times than S-(-)-chlorbufam. Chlorbufam enantiomers exerted herbicidal activity by inhibiting photosynthesis according to the results of the determination of photosynthetic pigment contents and molecular docking. Additionally, a novel HPLC-MS/MS method was successfully developed and validated for the detection of chlorbufam enantiomers and further applied for the enantioselective degradation study in soil. As a result, chlorbufam was satisfactory enantioseparated with a resolution of 2.37 on a Chiralpak IH column using the mobile phase of acetonitrile and water (60:40, v/v). Good linearity for chlorbufam enantiomers was obtained with correlation coefficients ≥0.9990, and the recovery ranged from 74.1 to 119% with relative standard deviations ≤10.9% at three spiked levels. The degradation behaviors of chlorbufam enantiomers were significantly different, and S-(-)-chlorbufam was preferentially degraded. The findings encouraged the application of enantiopure R-(+)-chlorbufam herbicide to reduce dosage rates, decrease environmental risks, and protect human health.

Enantioselective Toxicity of Ibuprofen to Earthworms: Unraveling the Effect and Mechanism on Enhanced Toxicity of S-Ibuprofen Over R-Ibuprofen

With the global implementation of wastewater reuse, accurately assessing the soil ecological risk of chiral pollutants from wastewater necessitates a comprehensive understanding of their enantioselective toxicity to soil animals. Ibuprofen (IBU) is the most prevalent chiral pharmaceutical in municipal wastewater. However, its enantioselective toxicity toward soil animals and the underlying mechanism remain largely unknown. In this study, the toxicity of IBU enantiomers, S-IBU and R-IBU, to earthworms was evaluated at environmentally relevant concentrations (10 and 100 μg/L), simulating wastewater reuse for irrigation. The results demonstrated that IBU adversely affects the growth, reproduction, regeneration, defense systems, and metabolic processes of earthworms, with S-IBU exhibiting stronger toxic effects than R-IBU. The bioavailability assessment revealed that S-IBU was more readily absorbed by earthworms and converted to its enantiomer within earthworms than R-IBU. This is consistent with molecular docking results showing that S-IBU had stronger affinities for functional proteins associated with xenobiotic transport and transformation. The findings of this study highlight that S-IBU poses a higher risk than R-IBU to soil organisms under wastewater reuse scenarios and that the chirality of chemical pollutants in wastewater deserves more attention when implementing wastewater reuse. In addition, our study underscores that the differences in bioavailability and bioactivity may account for the enantioselective toxicity of chiral pollutants.

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.

Chiral Carbon Dots and Chiral Carbon Dots with Circularly Polarized Luminescence: Synthesis, Mechanistic Investigation and Applications

Chiral carbon dots (CCDs) can be widely used in various fields such as chiral recognition, chiral catalysis and biomedicine because of their unique optical properties, low toxicity and good biocompatibility. In addition, CCDs with circularly polarized luminescence (CPL) can be synthesized, thus broadening the prospects of CCDs applications. Since the research on CCDs is still in its infancy, this paper reviews the chiral origin, formation mechanism, chiral evolution, synthesis and emerging applications of CCDs, with a special focus on CCDs with CPL activity. It is hoped that it will provide some reference to solve the current problems faced by CCDs. Finally, the opportunities and challenges of the current research on CCDs are described, and their future development trends have also been prospected.

Co-existing antibiotics alter the enantioselective dissipation characteristics of zoxamide and drive combined impact on soil microenvironment

Co-existence of antibiotics (ABX) in soil may expand the environmental harm of pesticide pollution. Our study investigated the combined effects of five antibiotics chlortetracycline (CTC), oxytetracycline (OTC), tetracycline (TC), sulfamethoxazole (SMX), enrofloxacin (ENR) on enantioselective fate of zoxamide (ZXM) and soil health. The results showed that S-(+)-ZXM preferentially dissipated in soil. ABX prolonged dissipation half-life and reduced enantioselectivity of ZXM. Soil was detected to be more acidic after long-term treatment of ZXM and ABX. Lowest soil available N, P, K were found in ZXM + SMX, ZXM + OTC and ZXM + SMX groups at 80 days, respectively. ABX had demonstrated effective promotion of catalase (S-CAT), urease (S-UE) and negative impact on dehydrogenase (S-DHA), sucrase (S-SC) activities. Bacteria Lysobacter, Sphingomonas and fungus Mortierella were identified as the most dominant genera, which possessed as potential microbial resources for removal of composite pollution from ZXM and ABX. SMX and TC, SMX, ENR, respectively, contributed to the alteration of bacteria and fungi community abundance. Soil acidity, available N and enzyme activity showed stronger correlations with bacteria and fungi compared to other environmental factors. Our findings highlighted the interactions between ZXM and ABX from the perspective of soil microenvironment changes. Moreover, a theoretical basis for the mechanism was actively provided.

Calcium-Alginate-Chitosan Nanoparticle as a Potential Solution for Pesticide Removal, a Computational Approach

Pesticides have a significant negative impact on the environment, non-target organisms, and human health. To address these issues, sustainable pest management practices and government regulations are necessary. However, biotechnology can provide additional solutions, such as the use of polyelectrolyte complexes to encapsulate and remove pesticides from water sources. We introduce a computational methodology to evaluate the capture capabilities of Calcium-Alginate-Chitosan (CAC) nanoparticles for a broad range of pesticides. By employing ensemble-docking and molecular dynamics simulations, we investigate the intermolecular interactions and absorption/adsorption characteristics between the CAC nanoparticles and selected pesticides. Our findings reveal that charged pesticide molecules exhibit more than double capture rates compared to neutral counterparts, owing to their stronger affinity for the CAC nanoparticles. Non-covalent interactions, such as van der Waals forces, π-π stacking, and hydrogen bonds, are identified as key factors which stabilized the capture and physisorption of pesticides. Density profile analysis confirms the localization of pesticides adsorbed onto the surface or absorbed into the polymer matrix, depending on their chemical nature. The mobility and diffusion behavior of captured compounds within the nanoparticle matrix is assessed using mean square displacement and diffusion coefficients. Compounds with high capture levels exhibit limited mobility, indicative of effective absorption and adsorption. Intermolecular interaction analysis highlights the significance of hydrogen bonds and electrostatic interactions in the pesticide-polymer association. Notably, two promising candidates, an antibiotic derived from tetracycline and a rodenticide, demonstrate a strong affinity for CAC nanoparticles. This computational methodology offers a reliable and efficient screening approach for identifying effective pesticide capture agents, contributing to the development of eco-friendly strategies for pesticide removal.

Enantioselective Degradation and Bioactivity Mechanism of a New Chiral Fungicide Fluindapyr in Paddy Ecosystems

Fluindapyr is a novel chiral succinate dehydrogenase inhibitor used to control fungal diseases. The enantioselective effects of fluindapyr in paddy ecosystems are unknown. We developed a new chiral determination method of fluindapyr using ultrahigh performance liquid chromatography tandem mass spectrometry. The absolute configuration of the fluindapyr enantiomers was identified by an electron circular dichroism model. A new husk-based biochar material was used to optimize and establish a QuEchERs method for paddy soil determination. Under anaerobic conditions, the half-lives of R-fluindapyr and S-fluindapyr in paddy soil were 69.6 and 101.8 days, respectively. R-fluindapyr degraded more rapidly than S-fluindapyr. S-fluindapyr was 87.8 times more active against Rhizoctonia solani than R-fluindapyr. The enantioselective bioactivity mechanism was illustrated by molecular docking between the fluindapyr enantiomers and SDH of R. solani. The binding powers of R-fluindapyr and S-fluindapyr to proteins were -32.12 and - 42.91 kcal/mol, respectively. This study reports the stereoselectivity of fluindapyr about determination, degradation, bioactivity, and its mechanism. It provides a foundation for an in-depth study of fluindapyr at the enantiomer level.

Enantioselective toxic effects of the novel chiral antifungal agrochemical penthiopyrad in the early life stage of zebrafish (Danio rerio)

Penthiopyrad was extensively applied in agricultural production, however, the toxicities information of the penthiopyrad enantiomers on early life stages of aquatic organism were limited. This study investigated the enantioselective toxicity of penthiopyrad on the early life stage of zebrafish by acute toxicity, sublethal toxic effects and the mRNA relative expression levels of genes related to succinate dehydrogenase, cardiac development, and lipid metabolism. The results showed that the 96-h-LC₅₀ of penthiopyrad racemate and enantiomers to zebrafish embryos were Rac-: 2.784 mg/L; R-(-)-: 3.528 mg/L; S-(+)-: 1.882 mg/L. Penthiopyrad exposure induced autonomous movement abnormalities, slowed heart rate and delayed hatching in zebrafish embryos, and caused developmental toxic effects such as pericardial edema and yolk sac edema. The mRNA relative expression levels results showed that penthiopyrad exposure induced significant enantioselectivity effect for the expression of the Sdha, Pr1 and Nkx2.5 with a 1.94-4.98-fold difference between different enantiomers, and significantly affected succinate dehydrogenase (energy metabolism), lipid metabolism and cardiac development-related genes expression. In general, S-(+)-penthiopyrad induced higher toxic effects in zebrafish embryos, and mitochondrial dysfunction may be an important cause of abnormal development. This study contributed to improve the comprehensive risk assessment and enantiomeric research system of penthiopyrad to early life stage of zebrafish.