Chlorothalonil Residues Research Articles

Hierarchical magneto-colorimetric labels for immediate lateral flow immunoassay of chlorothalonil residues

Quantitative detection of pesticide residues in food and environmental samples using an improved lateral flow immunoassay (LFIA) is of considerable importance for real-time analysis. This paper proposes a highly sensitive LFIA platform based on a hierarchical magneto-colorimetric compact. This compact serves as both the target magnetic enrichment substrate and a photosensitive label. Initially, a large porous dendritic silica template is prepared and doped with superparamagnetic ferric oxide nanoparticles (Fe3O4 NPs) and colloidal gold nanoparticles (AuNPs) at high densities within its vertical channels. The sequential assembly of central–radial channels allow for the three-dimensional integration of these two components, enabling independent control of their discrete functions without mutual interference. Following alkyl organosilicon encapsulation and silica sealing, the composite spheres are then applied in LFIA to detect chlorothalonil residues. Fe3O4 NPs enhance the binding efficiency to target analytes, while AuNPs amplify the signal, leveraging their high loading densities and robust optical properties. The developed LFIA platform exhibited a detection limit of 0.34 ng/mL for chlorothalonil and a linear range of 0.0085–824 ng/mL. The recoveries varied between 85.1 % and 103.1 %, and the relative standard deviations were 1.25%–8.84 %. This LFIA approach demonstrates high sensitivity, specificity, reproducibility and flexible detection modes, making it highly suitable for the on-site monitoring of pesticide residues.

Determination of chlorothalonil in vegetables/fruits using liquid chromatography-tandem mass spectrometry with a discharge adapter interface.

Chlorothalonil (CHT), a broad-spectrum fungicide, has been employed widely to control foliar diseases, whereas with a major metabolite of polar 4-hydroxychlorothalonil (CHT-4-OH), only an acceptable nonpolar CHT residue is allowed by most countries. This study involves the method development for CHT residue in vegetables/fruits using liquid chromatography-tandem mass spectrometry (LC-MS/MS) with a novel modified discharge-adaptor (DA) interface. CHT residue was analyzed using LC-MS/MS with DA interface (LC-DA-MS/MS), developed in our previous works. A DA was placed on the electrospray tip to switch the ionization modes. A modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) method was applied to extract CHT residue of vegetables/fruits efficiently with less sample preparation time and analysis cost. CHT and CHT-4-OH spiked in four different vegetables/fruits were extracted using the modified QuEChERS method. After LC with isocratic elution, CHT and CHT-4-OH were separated within 3min. Using LC-DA-MS/MS, the ion signals of CHT were improved two to three times, and the limit of quantification of 5ng/g and linearity (r2 > 0.99) in the range of 5-200 ng/g were achieved using 10g of vegetables/fruits. The precision and accuracy were within 15% each. The modified QuEChERS and LC-DA-MS/MS were applied to examine eight field-grown vegetables/fruits; 9.5 and 2588.9ng/g of CHT were detected in two vegetables/fruits. LC-DA-MS/MS combined with modified QuEChERS was successfully applied to determine CHT residue <10ng/g in vegetables/fruits and with satisfied validation results. The developed method could reduce both analysis cost and time, attributing to simplifications in modified QuEChERS, isocratic elution, and DA interface in LC-DA-MS/MS.

Non-destructive detection and recognition of pesticide residue levels on cauliflowers using visible/near-infrared spectroscopy combined with chemometrics.

In this study, two prediction models were developed using visible/near-infrared (Vis/NIR) spectroscopy combined with partial least squares discriminant analysis (PLS-DA) and least squares support vector machine (LS-SVM) for the detection of pesticide residues of avermectin, dichlorvos, and chlorothalonil at different concentration levels on the surface of cauliflowers. Five samples of each of the three different types of pesticide were prepared at different concentrations and sprayed in groups on the surface of the corresponding cauliflower samples. Utilizing the spectral data collected in the Vis/NIR as input values, comparison and analysis of preprocessed spectral data, and regression coefficient (RC), successive projections algorithm (SPA), and competitive adaptive reweighted sampling (CARS) were used in turn to downscale the data to select the main feature wavelengths, and PLS-DA and LS-SVM models were built for comparison. The results showed that the RC-LS-SVM was the best discriminant model for detecting avermectin residues concentration on the surface of cauliflowers, with a prediction set discriminant accuracy of 98.33%. For detecting different concentrations of dichlorvos, the SPA-LS-SVM had the best predictive accuracy of 95%. The accuracy of the model based on CARS-PLS-DA to identify chlorothalonil at different concentration levels on cauliflower surfaces reached 93.33%. The results demonstrated that the Vis/NIR spectroscopy combined with chemometrics could quickly and effectively identify pesticide residues on cauliflower surfaces, affording a certain reference for the rapid recognition of different pesticide residue concentrations on cauliflower surfaces. PRACTICAL APPLICATION: Vis/NIR spectroscopy can detect the concentration levels of pesticide residues on the surface of cauliflowers and help food regulators quickly and non-destructively detect traces of pesticides in food, providing a guarantee for food safety. The technique also provides a basis for determining pesticide residue concentrations on the surface of other vegetables.

Effects of four disease-controlling agents (chlorothalonil, CuCl2, harpin, and melatonin) on postharvest jujube fruit quality

Postharvest senescence and disease development can reduce the nutritional value of fresh jujube fruit. Herein, four different disease-controlling agents (chlorothalonil, CuCl2, harpin and melatonin) were separately applied to fresh jujube fruit, and all improved postharvest quality (evaluated by disease severity, antioxidant accumulation and senescence) relative to controls. Disease severity was drastically inhibited by these agents, in the order chlorothalonil > CuCl2 > harpin > melatonin. However, chlorothalonil residues were detected even after storage for 4 weeks. These agents increased the activities of defense enzymes including phenylalanine ammonia-lyase, polyphenol oxidase, glutathione reductase and glutathione S-transferase, as well as accumulation of antioxidant compounds such as ascorbic acid, glutathione, flavonoids and phenolics, in postharvest jujube fruit. The enhanced antioxidant content and antioxidant capacity (evaluated by Fe3+ reducing power) was ordered melatonin > harpin > CuCl2 > chlorothalonil. All four agents significantly delayed senescence (evaluated by weight loss, respiration rate and firmness), with the effect ordered CuCl2 > melatonin > harpin > chlorothalonil. Moreover, treatment with CuCl2 also increased copper accumulation ~ threefold in postharvest jujube fruit. Among the four agents, postharvest treatment with CuCl2 could be considered most appropriate for improving postharvest jujube fruit quality under low temperature conditions without sterilization.

Reactive oxygen species signaling is involved in melatonin-induced reduction of chlorothalonil residue in tomato leaves.

Pesticide overuse has led to serious global concerns regarding food safety and environmental pollution. Although the reduction of pesticide residue is critical, our knowledge about induced pesticide metabolism in plants remains fragmentary. Melatonin (N-acetyl-5-methoxytryptamine) is an effective stress-relieving agent in both animals and plants, but little is known about the melatonin signaling mechanism and its effect on pesticide metabolism in plants. Here, we found that exogenous melatonin treatment significantly reduced chlorothalonil residue by 41% but suppression of endogenous melatonin accumulation increased chlorothalonil residue in tomato leaves. Moreover, melatonin increased photosynthesis, Fv/Fm, Calvin cycle enzyme activity, antioxidant enzyme activity, glutathione pool, and RESPIRATORY BURST HOMOLOG1 (RBOH1) expression in tomato leaves. However, the upregulation of RBOH1, CYP724B2, GST1, GST2, GSH and ABC, the increased glutathione concentrations and the activity of detoxification enzymes due to melatonin treatment were all significantly attenuated by the treatment with an NADPH oxidase inhibitor and a ROS scavenger, indicating a clear relationship between the reduction of pesticide residue and induction in detoxifying enzymes and genes upon melatonin treatment in an apoplastic H2O2-dependent manner. These results reveal that melatonin-induced reduction in chlorothalonil residue is mediated by H2O2 signaling in tomato leaves.

Fungicide Exposure in Honey Bee Hives Varies By Time, Worker Role, and Proximity to Orchards in Spring.

Fungicides are commonly applied to prevent diseases in eastern North American cherry orchards at the same time that honey bees (Apis mellifera L. (Hymenoptera: Apidae)) are rented for pollination services. Fungicide exposure in honey bees can cause negative health effects. To measure fungicide exposure, we sampled commercial honey bee colonies during orchard bloom at two commercial tart cherry orchards and one holding yard in northern Michigan over two seasons. Nurse bees, foragers, larvae, pollen, bee bread, and wax were screened for captan, chlorothalonil, and thiophanate-methyl. We also looked at the composition of pollens collected by foragers during spring bloom. We found differences in fungicide residue levels between nurse bees and foragers, with higher captan levels in nurse bees. We also found that residue levels of chlorothalonil in workers were significantly increased during tart cherry bloom, and that nurse bees from hives adjacent to orchards had significantly higher chlorothalonil residues than nurse bees from hives kept in a holding yard. Our results suggest that fungicide exposure of individual honey bees depends greatly on hive location in relation to mass-flowering crops, and worker role (life stage) at the time of collection. In some pollen samples, captan and chlorothalonil were detected at levels known to cause negative health effects for honey bees. This study increases our understanding of exposure risk for bees under current bloom time orchard management in this region. Further research is needed to balance crop disease management requirements with necessary pollination services and long-term pollinator health.

Human health risk assessment of pesticides in lettuce and spinach grown in urban backyard garden soils

Pesticide residues in lettuce and spinach could be a serious human health concern since the average per capita consumption per day of leafy salad vegetables is ∼60 g. Here, we determined the leftover residues (LoR) of dimethoate, 2,4-D, glyphosate, and chlorothalonil in lettuce and spinach grown in three urban backyard soils to assess their potential human health hazards. Pesticide residues were extracted by QuEChERS method and quantified through LC-MS and LC-DAD. In most cases, residue levels in the vegetable samples were above the EU-MRLs. Soil organic carbon, silt, oxides of iron and aluminium negatively correlated (P < 0.05) with LoR of the pesticides while LoR positively correlated (P < 0.05) with contents of sand and clay, and pH. The estimated short-term intake (ESTI) values (mg kg1 day1) for dimethoate, 2,4-D, glyphosate and chlorothalonil even at recommended doses in case of lettuce and spinach were 0.003–9.90 × 103 and 0.005–37.10 × 103 for adults and children, respectively, whereas the corresponding estimated daily intake (EDI) values were 0.007–9.58 × 103 and 0.03–35.90 × 103. Accordingly, the calculated values of non-cancer acute health hazard (aHI <100%) and hazard quotient (HQ <1) indicated that consumption of salad vegetables grown in soils spiked with pesticides at doses recommended in agriculture does not pose human health risks. On the other hand, both lettuce and spinach grown in soils at ten-fold higher concentrations of dimethoate or chlorothalonil exceeded the threshold limit of aHI (>100%) for children and HQ > 1 for both children and adults, suggesting their potential acute and chronic health hazards. The present study, for the first time, provides health awareness about the consumption of pesticide-contaminated leafy vegetables grown in urban backyard garden soils.

Glutathione Promotes Degradation and Metabolism of Residual Fungicides by Inducing UDP-Glycosyltransferase Genes in Tomato.

Reduced glutathione (GSH) is a key antioxidant, which plays a crucial role in the detoxification of xenobiotics in plants. In the present study, glutathione could reduce chlorothalonil (CHT) residues in tomatoes by inducing the expression of the UDP-glycosyltransferase (UGT) gene. In plants, UGT is an important glycosylation catalyst, which can respond to stresses in time by activating plant hormones and defense compounds. Given the importance of plant growth and development, the genome-wipe analyses of Arabidopsis and soybean samples have been carried out, though not on the tomato, which is a vital vegetable crop. In this study, we identified 143 UGT genes in the tomato that were unevenly distributed on 12 chromosomes and divided into 16 subgroups and found that a variety of plant hormones and stress response cis-elements were discovered in the promoter region of the SlUGT genes, indicating that the UGT genes were involved in several aspects of the tomato stress response. Transcriptome analysis and results of qRT-PCR showed that most SlUGT genes could be induced by CHT, and the expression of these genes was regulated by glutathione. In addition, we found that SlUGT genes could participate in plant detoxification through interaction with transcription factors. These findings further clarify the potential function of the UGT gene family in the detoxification of exogenous substances in tomatoes and provide valuable information for the future study of functional genomics of tomatoes.

Residue levels, household processing evolution, and risk assessment of chlorothalonil, SDS‐3701, metalaxyl, and dimethomorph in Dendrobium officinale Kimura et Migo

Dendrobium officinale, a minor crop with medicinal and edible value, is increasingly entering people's diets, but the pesticide residues on it have received little attention. In this work, field trials were conducted under good agricultural practice (GAP) conditions to investigate the residues of chlorothalonil, SDS-3701, metalaxyl and dimethomorph in D. officinale, then the evolution of these pesticides after household processing were studied. The results indicated that chlorothalonil, SDS-3701, metalaxyl and dimethomorph were 2.41-30.12, 0.20-1.23, 0.07-0.80, 0.19-7.90 mg kg-1 respectively in stems at recommended preharvest interval (PHI, 30 d). Washing and soaking removed the pesticides in fresh stems with the processing factors (PFs) of 0.41-1.14 and 0.12-1.13, respectively. In brewing test, the transfer rates (TRs) of pesticides in dry stems decreased from the first time (4.27-95.40%) to the third time (3.89-15.57%). Intake risk assessments were also conducted and the risk quotients (RQs) were no more than 27.02% for all compounds in different samples, which indicated acceptable risks for consumers. As effective risk-reducing home processing methods, washing, soaking and multiple brewing were suggested in this work, hoping to help consumers with diet safety.

Dynamics and residues of difenoconazole and chlorothalonil in leafy vegetables grown in open-field and greenhouse

Lettuce and pak choi are major leafy vegetable crops grown globally. They are susceptible to a wide range of fungal pathogens, which cause severe disease symptoms and decrease yield and quality. Difenoconazole and chlorothalonil are important broad-spectrum fungicides used to manage fungal diseases in leafy vegetables. The dynamics and residues of difenoconazole and chlorothalonil applied on lettuce and pak choi were investigated. The degradation of difenoconazole and chlorothalonil in leafy vegetables under open-field and greenhouse conditions fitted the first-order kinetic equation, with half-lives varying between 2.09–3.07 days and 3.81–6.54 days, respectively. The terminal residues in leafy vegetables were performed by different spraying times under open-field. The residue levels of difenoconazole and chlorothalonil sprayed one to three times on leafy vegetables were lower than the maximum residue limits (MRLs) with seven and twenty-one interval days, respectively. The dietary risk assessment was performed using risk quotient (RQ) and revealed that the risk of difenoconazole with seven interval days and chlorothalonil with twenty-one interval days in leafy vegetables was acceptable. The pre-harvest intervals (PHIs) were recommended of seven days for difenoconazole and twenty-one days for chlorothalonil in leafy vegetables. The study contributes to a better understanding of the potential risks of fungicides in leafy vegetables.

Two different spectrophotometric methods for simultaneous determination of binary mixture of atenolol and amlodipine in commercial formulation

Two different spectrophotometric methods for simultaneous determination of binary mixture of atenolol and amlodipine in commercial formulation

Jasmonic acid promotes glutathione assisted degradation of chlorothalonil during tomato growth

Glutathione (GSH) biosynthesis and regeneration play a significant role in the metabolism of chlorothalonil (CHT) in tomatoes. However, the specific regulatory mechanism of GSH in the degradation of CHT remains uncertain. To address this, we investigate the critical regulatory pathways in the degradation of residual CHT in tomatoes. The results revealed that the detoxification of CHT residue in tomatoes was inhibited by buthionine sulfoximine and oxidized glutathione pretreatment, which increased by 26% and 46.12% compared with control, respectively. Gene silencing of γECS, GS, and GR also compromised the CHT detoxification potential of plants, which could be alleviated by GSH application and decreased the CHT accumulation by 33%, 25%, and 21%, respectively. Notably, it was found that the jasmonic acid (JA) pathway participated in the degradation of CHT regulated by GSH. CHT residues reduced by 28% after application of JA. JA played a role downstream of the glutathione pathway by promoting the degradation of CHT residue in tomatoes via nitric oxide signaling and improving the gene expression of antioxidant and detoxification-related enzymes. This study unveiled a crucial regulatory mechanism of GSH via the JA pathway in CHT degradation in tomatoes and offered new insights for understanding residual pesticide degradation.

The Residual Behavior of Chlorothalonil and Metalaxyl in The Egyptian Cucumbers Fields Infested with Downy Mildew Using The High-Performance Liquid Chromatography (Hplc) and Quechers Method. سلوک متبقيات الکلوروثالونيل والميتالاکسيل فى حقول الخيار المصابه بالبياض الزغبى بإستخدام جهاز الکروماتوجراف السائل عالى الأداء HPLC)) بإستخدام طريقة الـQUECHER.

The dissipation rate of the commercial fungicide with two active ingredients (Chlorothalonil 64% + Metalaxyl 8%) that was approved by the agriculture pesticides committee was evaluated in the cucumber fields infested with downy mildew in Egypt using HPLC analytical system. The experiment was designed in randomized block design. After spraying at the recommended rate of applications, the samples of cucumber were chosen randomly from treated and un-treated plants after the interval of zero time(2hours), 1, 3, 7,10, and 14 days. The technique was validated at different fortification levels (0.01, 0.5, and 0.1 μg mL−1). The recoveries of both fungicides Chlorothalonil and Metalaxyl were 87.6 and 95 %. The results showed that the initial residues (zero time) were 4.38and 3.21 mg/kg-1. All detected residues significantly decreased upon time elevated. The residues extracted by an optimized QuEChERS coupled with HPLC analytical system were accurate and acceptable The limit of quantitation was 0.05 for both fungicides. The dissipation curves of both Chlorothalonil and Metalaxyl followed the first-order kinetics. The half-life’s (t½) values were 0.89 and 1.1days in, respectively. Under the optimized condition, the residues of Chlorothalonil and Metalaxyl in cucumber were below the codex maximum residue limit (0.5 and 3 mg/kg-1). Consequently, the pre-harvest intervals (PHI) in cucumber were seven days for the fungicide.

Deposition, dissipation, metabolism and dietary risk assessment of chlorothalonil in open field-planted cabbage

Chlorothalonil is a fungicide commonly used to prevent and control leafy vegetable diseases. The residual distribution of chlorothalonil on cabbage is unclear and rarely reported. The spatiotemporal distribution of chlorothalonil was used to understand its environmental behavior in cabbage. The results of open-field experiments demonstrated that chlorothalonil was distributed primarily on the second and third layers of rosette leaves and the first layer of bulb leaves. The chlorothalonil residues on cabbage followed the order of winter > fall > summer, and heading stage > rosette stage > seedling stage. Chlorothalonil on cabbage underwent −OH substitution forming 4-hydroxychlorothalonil, and reductive dechlorination forming 2,4,5-trichloro-1,3-isophthalonitrile, 2,5-dichloro-1,3-isophthalonitrile, and 5-chloro-1,3-isophthalonitrile. The residues of chlorothalonil in the outermost leaves of cabbage bulb pose an unacceptable risk to human health via dietary exposure. This study contributes to better understanding on the fate and transformation chlorothalonil in cabbage and potential risks to human health via dietary consumption.

Evaluation of confirmatory data following the Article 12 MRL review for chlorothalonil, including assessments for import tolerances for banana, papaya and peanuts.

The applicants Syngenta Crop Protection, UPL Europe Ltd. and Oxon Italia S.p.A. submitted requests to the competent national authority in the Netherlands to evaluate the confirmatory data for chlorothalonil that were identified in the framework of the MRL review under Article 12 of Regulation (EC) No 396/2005 as not available; in addition, Syngenta and UPL submitted requests for modifications of existing MRLs. Considering the recent decision on the non‐approval of chlorothalonil, the requests for amending existing MRLs to reflect intended EU uses for chlorothalonil and confirmatory data for EU uses became obsolete. EFSA focused therefore its assessment on the import tolerances and on general information on the analytical method required to enforce legal limits for chlorothalonil and its metabolite SDS‐3701 (R182281). Analytical methods for enforcement are available to control the residues of chlorothalonil and SDS‐3701 in plant matrices at the validated LOQ of 0.01 mg/kg; data on the extraction efficiency for high oil content matrices as requested in the MRL review were not provided. This data gap is relevant for the import tolerance for peanuts. The data submitted in support of import tolerances were found to be sufficient to derive MRL proposals for chlorothalonil and SDS‐3701 for bagged bananas, papayas and peanuts. Studies investigating the effect of high temperature processing on the magnitude of SDS‐3701 in processed products are not available. Based on exposure calculations for chlorothalonil, EFSA concluded that the long‐term intake of residues resulting from the use of chlorothalonil according to the reported agricultural practices is unlikely to present a risk to consumers. For papaya, an acute intake concern was noted for chlorothalonil, while for banana and peanuts, the expected short‐term intake of chlorothalonil residues was below the toxicological reference value. For the metabolite SDS‐3701, the toxicological profile is not fully elucidated, and therefore, toxicological reference values could not be derived. Hence, for this metabolite, the consumer risk assessment cannot be finalised.

Spatial distribution of environmental pollutants in natural honeys collected from some regions of Saudi Arabia

Natural honeys produced in some regions located in Saudi Arabia (KSA) were characterized on the basis of their physicochemical properties and the contents of heavy metals and pesticide residues. Some of the investigated samples fit most of the national and international specifications with geographical and seasonal variations. The levels of Pb2+, Cd2+, and Cu2+ in most of the tested samples were below the guideline values of 0.1, 0.05, and 5 mg/kg, respectively; however, Zn2+ and Fe3+ levels in most of the tested samples exceeded the guideline values of 5 and 15 mg/kg, respectively. The high levels of Mn2+ and Ni2+ have been found in all the tested samples which can be attributed either to the production stages of honey or the region from where the honey has been taken. Also, the present results revealed that some pesticides such as chlorothalonil, carbaryl, dicofol, and monocrotophos residues were detected in some samples. It can be concluded that some metals and pesticide residues are not in safety baseline levels for human consumption and may pose a health risk to consumers.

Determination of residual amounts of chlorothalonil in peaches: problems of gas chromatographic identification with the use of electron capture detector

In the work there are presented results of studies on the validation of the gas chromatographic (GC) methodfor the determination of chlorothalonil residue amounts in peaches with the use of electron capture detector (ECD). For the analytical control there was selected such stone fruit crop as the peach, referring to the crops, the most contaminated with residue amounts ofpesticides. There was justified the necessity of the inclusion in the procedure of the detection of the method of confirmation, based on mass spectrometry detection (MSD) (the type of ionization - electron impact). The significant source of the obtaining of incorrect data in the identification with the use of ECD of ions are shown to be phthalates, visualized in the chromatogram as intense and/or broad peaks. Mass spectra of compounds of the class ofphthalates are characterized by the dominant peak of the ion with the value of (mass/ charge) 149, just on this peak the detection of low molecular weight phthalates occurs in various matrices, on the spectrum there are also recorded typical ions corresponding to fragments of radical residues. The combination of the use of various types of the detection allows to prove that the revealed response (detector signal) is caused just by the analyte, but not the impurities, and optionally to optimize chromatographic conditions towards to the obtaining reliable results. The lower limit of the quantitation of chlorothalonil in peach fruits accounts for 0.01 mg/kg, determined with a signal/noise ratio of 10. The range of measured concentrations is volatile between 0.01-0.1 mg/kg, recovery rate of chlorothalonil from samples of peaches, established according to results of the analysis of model samples with the introduction of the substance in four points along the detection range, was 84-102%, the SD value of the repeatability varies in the range of 2.0-5.8%.

Environmental view for chlorothalonil on tomato and pepper fruits and soil field in Egypt: Risk assessment and pre-harvest gap

ABSTRACT The objectives of this study were to determine the residues of chlorothalonil which was sprayed with a recommended dose on tomato, pepper, soil under and the nearest water source and to examine the decline and safety. Recovery for tomato and pepper fruits ranged from 88.27% to 108.01%, 79.81% and 102.57% for soil and nearest water source, respectively. Limit of detection and quantification were 0.01 and 0.05 mg kg−1 respectively.The field trial was carried out in El-Sharkia Governorate, Egypt. Samples were randomly collected at pre-harvest intervals (PHI) of 0 day (1 h), 1, 3, 7, 10, and 15 days, respectively. A gas chromatography micro-electron capture detector method was used to detect residue levels. The data showed that the initial deposits were 2.86, 4.01 mg/kg in tomato and pepper, 0.89, 1.43 mg/kg in soil under tomato and pepper, respectively. The half-lives were found to be 1.79 and 1.83 days for tomato and pepper, respectively, while they were 1.63 days and 2.28 days in soil under tomato and pepper, respectively. No chlorothalonil residues were detected in water samples. Apparently, there is no chlorothalonil risk to consumers.

Glutaredoxin S25 and its interacting TGACG motif-binding factor TGA2 mediate brassinosteroid-induced chlorothalonil metabolism in tomato plants

The presence of pesticide residues in fresh fruits and vegetables poses a serious threat to human health. Brassinosteroids (BRs) can reduce pesticide residues in plants, but the underlying mechanisms still remain unclear. Here, we identified a tomato glutaredoxin gene GRXS25 which was induced by 24-epibrassinolide (EBR) and chlorothalonil (CHT) in a way dependent on apoplastic reactive oxygen species (ROS). Silencing of GRXS25 in tomato abolished EBR-induced glutathione S-transferases (GSTs) gene expression and activity, leading to an increased CHT residue. Yeast two-hybrid and bimolecular fluorescence complementation assays showed protein-protein interaction between GRXS25 and a transcription factor TGA2. Electrophoretic mobility shift and chromatin immunoprecipitation assays indicated that TGA2 factor bound to the TGACG-motif in the GST3 promoter. While silencing of TGA2 strongly compromised, overexpression of TGA2 enhanced expression of GST genes and CHT residue metabolism. Our results suggest that BR-induced apoplastic ROS trigger metabolism of pesticide residue in tomato plants through activating TGA2 factor via GRXS25-dependent posttranslational redox modification. Activation of plant detoxification through physiological approaches has potential implication in improving the food safety of agricultural products.

Three Different Spectrophotometric Methods for Simultaneous Determination of Pyriproxyfen and Chlorothalonil Residues in Cucumber and Cabbage Samples

In this study, three simple and accurate spectrophotometric methods for simultaneous determination of pyriproxyfen and chlorothalonil residues in cucumbers and cabbages grown in experimental greenhouse were studied. The first method was based on the zero-crossing technique measurement for first and second derivative spectrophotometry. The second method was based on the first derivative of the ratio spectra. However, the third method was based on mean centering of ratio spectra. These procedures lack any previous separation steps. The calibration curves for three spectrophotometric methods are linear in the concentration range of 1–30 μg·mL−1and 0.5–7 μg·mL−1for pyriproxyfen and chlorothalonil successively. The recoveries ranged from 82.12–97.40% for pyriproxyfen and 81.51–97.04% for chlorothalonil with relative standard deviations less than 4.95% and 5.45% in all instances for pyriproxyfen and chlorothalonil, respectively. The results obtained from the proposed methods were compared statistically by using one-way ANOVA, and the results revealed there were no significant differences between ratio spectra and mean centering methods with the zero-crossing technique. The proposed methods are successfully applied for the simultaneous estimation of the residue of both pesticides in cucumber and cabbage samples.