Enantioselective effect of the chiral fungicide tebuconazole on the microbiota community and antibiotic resistance genes in the soil and earthworm gut.

Tebuconazole, consisting of two enantiomers, has a high detectable rate in the soil. The residue of tebuconazole in the soil may cause risk to microbiota community. Antibiotic resistance genes (ARGs) are considered as emerging environmental contaminants, and they can be transferred vertically and horizontally between microbiota community in the soil. Until now, the enantioselective effect of tebuconazole on the microbiota community and ARGs in the soil and earthworm gut has remained largely unknown. Tebuconazole enantiomers showed different bioconcentration behaviors in earthworms. The relative abundances of bacteria belonging to Actinobacteriota, Crenarchaeota and Chloroflexi in R-(-)-tebuconazole-treated soil were higher than those in S-(+)-tebuconazole-treated soil at same concentrations. In the earthworm gut, bacteria belonging to Proteobacteria and Bacteroidota exhibited different relative abundances between the S-(+)-tebuconazole and R-(-)-tebuconazole treatments. The numbers and abundances of ARGs in the soil treated with fungicides were higher than those in the control. In earthworm gut, the diversities of ARGs in all treatments were higher than that in the control, and the relative abundances of Aminoglycoside, Chloramphenicol, Multidrug resistance genes and mobile genetic elements (MGEs) in R-(-)-tebuconazole-treated earthworm gut were higher than those in S-(+)-tebuconazole-treated earthworm gut. Most of ARGs showed a significantly positive correlation with MGEs. Based on network analysis, many ARGs may be carried by bacteria belonging to Bacteroidota and Proteobacteria. These results provide valuable information for understanding the enantioselective effect of tebuconazole on the microbiota community and ARGs.

Effect of Cd/Cu on the toxicity and stereoselective environmental behavior of dinotefuran in earthworms Eisenia foetida.

Pesticides and heavy metals commonly coexist in soil. In this study, the influence of Cd and Cu on the toxicity of rac-dinotefuran and the enantioselective behavior of dinotefuran enantiomers in soil-earthworm microcosms were investigated. The acute toxic tests showed that S-dinotefuran has higher toxic than that of R-dinotefuran. The rac-dinotefuran and Cd has an antagonistic effect on earthworms, and the Cu and rac-dinotefuran has a synergistic effect. Earthworms maybe promoted the enantioselective behavior of dinotefuran in soil. Co-exposure to Cd or Cu inhibited the dissipation of dinotefuran enantiomers (S-dinotefuran and R-enantiomers), and slightly reduced the enantioselectivity in soil. The earthworms were found to be preferentially enriched with S-dinotefuran. However, Cd or Cu attenuated the accumulation of dinotefuran enantiomers in earthworms and decreased the enantioselectivity. The effect of Cd and Cu on the environmental behaviors of dinotefuran enantiomers were correlated positively with the dose of Cd/Cu. These results showed that Cd and Cu alter the environmental behaviors and the toxicity of dinotefuran enantiomers in soil-earthworm microcosms. Thus, the influence of coexistent heavy metals on the ecological risk assessment of chiral pesticides should be considered.

Enantioselective Effect of Flutriafol on Growth, Deoxynivalenol Production, and TRI Gene Transcript Levels in Fusarium graminearum.

In recent years, deoxynivalenol (DON) has frequently been detected in wheat grains and their products. The enantioselective impact of flutriafol on the growth and DON biosynthesis of Fusarium graminearum was investigated in relation to water activity (αw, 0.97 and 0.99) and temperature (20, 25, and 30 °C) on the wheat-based medium. R-(-)-flutriafol exhibited higher bioactivity than S-(+)-flutriafol and Rac-flutriafol under the above conditions. Flutriafol enantiomers reduced or stimulated DON biosynthesis depending on αw. DON levels were negligible after 14 or 7 days of incubation times under 0.97 and 0.99 aw, respectively. Quantitative real-time polymerase chain reaction (qRT-PCR) analyses showed that the expression levels of trichothecene biosynthetic (TRI) genes of F. graminearum under 0.97 aw were significantly higher than those under 0.99 aw. In addition, R-(-)-flutriafol can induce more TRI gene expression than S-(+)-flutriafol. Taken together, this study indicated that aw and temperature play important roles in regulating DON biosynthesis in F. graminearum with flutriafol enantiomers.

Determination of pyrethroid residues in herbal tea using temperature-controlled ionic liquid dispersive liquid-liquid microextraction by high performance liquid chromatography.

A simple and effective method for determining five pyrethroid residues in herbal tea by ultrasound-enhanced temperature-controlled (UETC) ionic liquid dispersive liquid-liquid microextraction (IL-DLLME) coupled with high performance liquid chromatography-diode array detection (HPLC-DAD) was developed. The use of ultrasonication and heating improved the ability of the ionic liquid to extract the analytes. Various parameters that affect the extraction efficiency were investigated and optimized using single factor experiments and response surface design. The optimum conditions of the experiment were 121 µL of [HMIM][PF6] (extraction solvent), 794 µL of acetonitrile (dispersive solvent), a heating temperature of 40°C, a sonication time of 3.6 min and a pH of 2.9. Under optimized conditions, the linearity was in the range of 0.05-5 mg L-1 with correlation coefficients above 0.9993. The limits of detection and quantification were 1.25-1.35 µg L-1 and 5 µg L-1, respectively. The mean recoveries of the five pyrethroids ranged from 74.02% to 109.01%, with RSDs below 9.04%. The proposed method was reliable for the analysis of pyrethroids in Chinese herbal tea.

Dissipation of fluazinam in citrus groves and a risk assessment for its dietary intake.

BACKGROUND: Citrus is one of the most important fruit crops worldwide. Fluazinam is a fungicide that is used to control fungal diseases, and its dissipation and residue in citrus fruits should be studied. RESULTS: A Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) procedure combined with gas chromatography with an electron capture detector (GC-ECD) has been developed. The fortified recoveries ranged from 82.1% to 105.9%, with relative standard deviations (RSDs) of less than 5.7%. Fluazinam dissipated relatively quickly following first-order kinetics, with a half-life of 8.5-9.5 days. The experiments on the terminal residue of fluazinam in citrus were conducted at six locations in China, and the risk quotient (RQ) method was applied to citrus fruits for dietary exposure risk assessment based on the terminal residue test. The RQs of fluazinam at three preharvest intervals (PHIs) (21, 28, and 35 days) were all less than 100%, which is an acceptable level for human consumption. The present study provides a reference for the establishment of maximum residue limit (MRL) for fluazinam in citrus. CONCLUSIONS: The dissipation and residues of fluazinam in citrus were monitored. The half-life of less than 10 days showed that fluazinam could degrade relatively easily in citrus. The risk assessment also indicated the intake safety of fluazinam in citrus. © 2019 Society of Chemical Industry.

A Vortex-Assisted Dispersive Liquid-Liquid Microextraction Followed by UPLC-MS/MS for Simultaneous Determination of Pesticides and Aflatoxins in Herbal Tea.

A method for detecting the organophosphorus pesticides residue and aflatoxins in China herbal tea has been developed by UPLC-MS/MS coupled with vortex-assisted dispersive liquid-liquid microextraction (DLLME). The extraction conditions for vortex-assisted DLLME extraction were optimized using single-factor experiments and response surface design. The optimum conditions for the experiment were the pH 5.1, 347 µL of chloroform (extraction solvent) and 1614 µL of acetonitrile (dispersive solvent). Under the optimum conditions, the targets were good linearity in the range of 0.1 µg/L⁻25 µg/L and the correlation coefficient above 0.9998. The mean recoveries of all analytes were in the ranged from 70.06%⁻115.65% with RSDs below 8.54%. The detection limits were in the range of 0.001 µg/L⁻0.01µg/L. The proposed method is a fast and effective sample preparation with good enrichment and extraction efficiency, which can simultaneously detect pesticides and aflatoxins in China herbal tea.