Systemic stereoselectivity study of bromothalonil: stereoselective bioactivity, toxicity, and degradation in vegetables and soil

Comparative study of two indoor microbial volatile pollutants, 2-Methyl-1-butanol and 3-Methyl-1-butanol, on growth and antioxidant system of rice (Oryza sativa) seedlings

2-Methyl-1-butanol (2MB) and 3-Methyl-1-butanol (3MB) are microbial volatile organic compounds (VOCs) and found in indoor air. Here, we applied rice as a bioindicator to investigate the effects of these indoor microbial volatile pollutants. A remarkable decrease in germination percentage, shoot and root elongation, as well as lateral root numbers were observed in 3MB. Furthermore, ROS production increased by 2MB and 3MB, suggesting that pentanol isomers could induce cytotoxicity in rice seedlings. The enhancement of peroxidase (POD) and catalase (CAT) activity provided evidence that pentanol isomers activated the enzymatic antioxidant scavenging systems, with a more significant effect observed in 3MB. Furthermore, 3MB induced higher activity levels of glutathione (GSH), oxidized glutathione (GSSG), and the GSH/GSSG ratio in rice compared to the levels induced by 2MB. Additionally, qRT-PCR analysis showed more up-regulation in the expression of glutaredoxins (GRXs), peroxiredoxins (PRXs), thioredoxins (TRXs), and glutathione S-transferases (GSTUs) genes in 3MB. Taking the impacts of pentanol isomers together, the present study suggests that 3MB exhibits more cytotoxic than 2MB, as such has critical effects on germination and the early seedling stage of rice. Our results provide molecular insights into how isomeric indoor microbial volatile pollutants affect plant growth through airborne signals.

Stereoselectivity of paclobutrazol enantiomers to oxidative stress in wheat

Chiral pesticides have the special chiral structures, so enantioselective biological effects are usually observed in living organisms. Current study used paclobutrazol as a case study and explored the enantioselective degradation and oxidative stress effect on wheat. The results demonstrated that the degradation of R-paclobutrazol was faster than S-paclobutrazol significantly and improved the content of MDA and O2 - in wheat plants, which proved that the R-paclobutrazol induced oxidative damage in wheat, showing selective biological effects, and S-paclobutrazol was friendly to wheat. This study provided a theoretical basis for the selective activity of chiral pesticides and the development of chiral pesticide monomers.

Vermitoxicity of aged biochar and exploring potential damage factors

Although biochar is a promising soil amendment, its characteristics change owing to its aging in soil. Studies have shown that some aged biochar is hazardous to plants and soil microbiota. Earthworms are well-known soil ecosystem engineers; nevertheless, the toxic effects of aged biochar on them (vermitoxicity) are yet unknown, and it is necessary to explore the potential risk factors. Here, a series of soil culture experiments were conducted to systematically examine the vermitoxicity of aged biochar at various levels utilizing the earthworm Eisenia fetida and corncob biochar.. Acute toxicity bioassays were also used to evaluate several potential harm factors utilizing modified aged biochar/leaching solutions. The findings showed that both fresh and aged biochar might have adverse effects on earthworms, and that aged biochar was more toxic than fresh biochar with LC₅₀s reduced to 6.89%. Specifically, aged biochar caused earthworm death, growth inhibition with a maximum of 36.6%, and avoidance with 100% avoidance at the application rates of 2% at the individual-behavioral level. At the cellular and physiological-biochemical levels, aged biochar damaged coelomocyte lysosomal membrane stability, disrupted antioxidant enzyme activities, and improved the malondialdehyde (MDA) content in earthworms. Heat-treated and pH-modified aged biochar exhibited less acute toxicity on earthworms than aged biochar, whereas aqueous and acetone extracts showed weak vermitoxicity. As a result, earthworms may be harmed by volatile organic compounds (VOCs), an improper pH, and aqueous and acetone extracts. Additionally, the range of neural red retention times (NRRTs) was reviewed as ∼20-70 min mostly. This study, as far as we know, is the first to evaluate the vermitoxicity of aged biochar and its potential damage factors. The results may enhance our understanding of ecological toxicity of biochar, particularly over the long term, and lead to the development of application standards for biochar amendments to the soil.

Systematic evaluation of chiral pesticides at the enantiomeric level: A new strategy for the development of highly effective and less harmful pesticides

Over the past few decades, pesticides have been used in large quantities, and they pose potential risks to organisms across various environments. Reducing the use of pesticides and their environmental risks has been an active research focus and difficult issue worldwide. As a class of pesticides with special structures, chiral pesticides generally exhibit enantioselectivity differences in biological activity, ecotoxicity, and environmental behavior. At present, replacing the racemates of chiral pesticides by identifying and developing their individual enantiomers with high efficiency and environmentally friendly characteristics is an effective strategy to reduce the use of pesticides and their environmental risks. In this study, we review the stereoselective behaviors of chiral pesticide, including their environmental behavior, stereoselective biological activity, and ecotoxicity. In addition, we emphasize that the systematic evaluation of chiral pesticides at the enantiomeric level is a promising novel strategy for developing highly effective and less harmful pesticides, which will provide important data support and an empirical basis for reducing pesticide application.

Evaluation of Chiral Fungicide Penflufen in Legume Vegetables: Enantioseparation and Its Mechanism, Enantioselective Behaviors, and Risk Assessment

Illustrating the enantioselective behaviors of the novel chiral fungicide penflufen was extremely important for ecological safety and human health. For penflufen enantiomers, an excellent separation method including a short analysis time (4 min), a high sensitivity (2 ng/g), and lesser consumption of an organic solvent was first established through supercritical fluid chromatography-tandem mass spectrometry. The enantioseparation mechanism was explained by computational chemistry, and the stronger binding ability of S-(+)-penflufen with cellulose tris-(3-chloro-4-methylphenylcarbamate) (the chiral stationary phase OZ-3 column) contributed to the posterior elution. In legume vegetables, penflufen dissipation was the fastest in Pisum sativum Linn plants (half-life, 1 day) and the slowest in Glycine max plants (half-lives, 11.3-12.9 days). After 30, 50, and 40 days, the rac-penflufen residues were lower than the maximum residue level value in the Electronic Code of Federal Regulations (10 ng/g) in G. max, P. sativum Linn, and Vigna unguiculata, respectively. Abundant S-(+)-penflufen was found in these plants with stereoisomeric excess (se) changes being >10% in the initial stage, so the risk assessment might be driven by S-(+)-penflufen. However, the se changes were <10% in V. unguiculata plants, and the risk assessment might be calculated based on rac-penflufen. Moreover, penflufen enantiomers could be transferred from legume vegetables to soils, and the concentrations increased with time. The high persistence and medium mobility of penflufen in soils might lead to potential groundwater contamination, which was noteworthy. These results could contribute to a more accurate risk assessment of penflufen in legume vegetables.

Chiral separation of new chiral insecticide pyraquinil isomers and establishment of analytical methods in vegetables

以全新手性杀虫剂唑虫酯为研究对象,通过筛选手性色谱柱和优化流动相比例,建立了唑虫酯及其氧化代谢物异构体的拆分方法,在此基础上开发利用高效液相色谱-串联质谱(HPLC-MS/MS)同时测定小白菜和蕹菜中唑虫酯及其氧化产物手性异构体的分析方法。以纤维素-三(3,5-二氯苯基氨基甲酸酯)共价键合手性柱(Chiral INC)(250 mm×4.6 mm, 5 μm)为分析柱,乙腈和2 mmol/L甲酸铵水溶液作为流动相进行梯度洗脱分离,在多反应监测负离子模式下进行检测,唑虫酯4个异构体分离度分别为1.63、2.83和1.74,唑虫酯氧化产物异构体分离度为5.82。通过衍生化的方法进一步确定出峰顺序为RS-唑虫酯、SS-唑虫酯、RR-唑虫酯、SR-唑虫酯、S-唑虫酯氧化产物和R-唑虫酯氧化产物。唑虫酯和其氧化产物的手性异构体分别在1.25~1250 μg/L和2.5~2500 μg/L范围内具有良好的线性关系,相关系数(R²)大于0.99。在蕹菜和小白菜样品中同时添加唑虫酯和唑虫酯氧化产物消旋体进行添加回收试验,添加水平为1、20、400 μg/kg(即唑虫酯异构体为0.25、5、100 μg/kg;唑虫酯氧化代谢产物异构体为0.5、10、200 μg/kg),回收率为72.6%~110.6%,相对标准偏差(RSD)均在9.4%以下,其中日内重复性的RSD在0.5%~9.4%之间;日间重复性的RSD在1.0%~8.6%之间,表明该方法具有良好的回收率和精密度。该研究可为唑虫酯这一新型手性农药的环境行为研究及后续质量控制、药效评价等提供相应的分析技术,为新农药开发应用提供有力的技术支撑。

Study on stereoselective bioactivity, acute toxicity, and degradation in cucurbits and soil of chiral fungicide famoxadone

The chiral pesticide famoxadone is mainly applied to control fungal diseases on fruiting vegetables. The fungicidal activity, ecotoxicological effects, and degradation behavior of famoxadone enantiomers are less well known. In this study, a systemic assessment of the stereoselectivity of famoxadone was performed in cucurbits and soil. Famoxadone enantiomers presented distinct inhibitory activities among different fungal species. The bioactivities of R-(-)-famoxadone were 2.7-178 times higher than S-(+)-famoxadone toward five phytopathogens. Based on the obtained LC₅₀ values, famoxadone was super toxic to Eisenia foetida (E. foetida). Moreover, the acute toxicity of R-(-)-famoxadone presented 167 times greater to E. foetida than that of S-(+)-famoxadone, indicating that R-(-)-famoxadone showed higher bioactivity toward target organisms and non-target organisms than S-(+)-famoxadone. In addition, a simple high-performance liquid chromatography (HPLC) method was established to determine the stereoselective degradation of famoxadone in two species of cucurbits (cucumber and chieh-qua) and in field soil. The half-life values of famoxadone degradation were from 5.4 to 14.1 days, indicating that famoxadone was easily degraded. Additionally, no stereoselective degradation was found in cucurbits and soil. The results may provide promising implications for comprehensive environmental and ecological risk assessments of famoxadone.

Chiral Organophosphorous Pesticide Fosthiazate: Absolute Configuration, Stereoselective Bioactivity, Toxicity, and Degradation in Vegetables

Fosthiazate is a widely used chiral organophosphorous nematicide with four stereoisomers. The present study systemically assessed the stereoselectivity of fosthiazate for the first time, including absolute configuration confirmation, stereoselective bioactivity toward nematode and aphid, toxicity to honeybees, and stereoselective degradation in cucumber and pepper under field conditions. The absolute configurations of the four stereoisomers that eluted on the Superchiral IG-3 column were confirmed as (1S,3R)-(-)-fosthiazate, (1S,3S)-(-)-fosthiazate, (1R,3S)-(+)-fosthiazate, and (1R,3R)-(+)-fosthiazate. In comparison to the other two stereoisomers, (1S,3R)-fosthiazate and (1S,3S)-fosthiazate possess more than 100 times bioactivity and 10 times toxicity toward the target and non-target organisms, respectively. The molecular docking found that (1S,3R)-fosthiazate and (1S,3S)-fosthiazate had shorter binding distances and lower energies with acetylcholinesterase (AChE), which illuminated the mechanism of the experimental results. In addition, both of the high-bioactive stereoisomers had faster degradation rates in cucumber and pepper. On the basis of the results of bioactivity, toxicity, and degradation behavior, the stereoisomer mixture with (1S,3R)-fosthiazate and (1S,3S)-fosthiazate will be a better option than racemic fosthiazate to increase the bioactivity and reduce application rates.