Enantioselectivity of indoxacarb during the growing, processing, and brewing of tea: Degradation, metabolites, and toxicities

A Novel "Mobile Phase Braking Drift Technique" Utilized for the Enantioselective Residual Analysis of Cyflumetofen and the Investigation of Its Enantiomeric Migration during Tea Growth, Processing, and Brewing

Cyflumetofen (CYF) enantiomers were first separated by reversed-phase liquid chromatography. The enantioselectivity during tea growth, processing, and brewing was studied by a reversed-phase ultrahigh performance liquid chromatography tandem mass spectrometry (RP-UHPLC-MS/MS) method. The linearity ranges of CYF enantiomers in different matrix-matched calibration curves were from 0.0025 to 1.0 mg/L, with satisfactory correlation coefficients (R2 ≥ 0.9985). The average recoveries of (+)-CYF and (-)-CYF were 76.3-116.9 and 82.9-116.9%, respectively. The limits of quantification (LOQs) for the two enantiomers were 2.5 μg/kg in fresh tea leaves and tea, and 0.25 μg/L in tea infusion. The dissipation half-life (t1/2) of (+)-CYF and (-)-CYF during fresh tea growth was 1.04 days and 1.23 days, respectively. After processing the fresh tea leaves into green tea (black tea), the processing factors (PFs) of (+)-CYF and (-)-CYF were 0.15-0.26 (0.18-0.61) and 0.11-0.26 (0.20-0.60), respectively. The total leaching rates (TLRs) of (+)-CYF and (-)-CYF from green tea (black tea) to tea infusion were 2.7% (4.2%) and 2.1% (4.9%). The enantiomeric fractions (EFs) of CYF migration during tea growth, processing, and brewing were 0.48-0.50, 0.44-0.56, and 0.47-0.57, respectively, indicating no enantioselectivity.

The stereoselective bioactivity and mechanism of indoxacarb against Spodoptera frugiperda

BACKGROUND

Indoxacarb, a type of chiral pesticide, is used to control Lepidoptera insects. Most studies had focused on the environmental behavior and selective toxicity of indoxacarb enantiomers, and the mechanism behind its selective biological activity against target organisms is not well understood.

RESULTS

Spodoptera frugiperda was selected as the target insect. The lethal concentrations (96 h) of indoxacarb enantiomers on S. frugiperda were 2.61 mg/kg (S-indoxacarb) and 463.52 mg/kg (R-indoxacarb). S-Indoxacarb resulted in stronger oxidative damage to S. frugiperda than R-indoxacarb, and catalase and malondialdehyde were upregulated by 40.46% and 68.64% respectively after treatment with S-indoxacarb. Furthermore, cytochrome P450 and carboxylesterase were activated by S-indoxacarb, increasing by 39.62% and 63.68% respectively. Decarbomethoxyllated JW062 (DCJW), a metabolite of indoxacarb, has insecticidal activity. The concentration of DCJW in the S-indoxacarb treatment group was 2.73 times that in the R-indoxacarb treatment group. Molecular docking results demonstrated that S-indoxacarb could spontaneously bind to metabolic enzymes and be metabolized.

CONCLUSIONS

Enantiomeric bioactivity of indoxacarb enantiomers against on S. frugiperda was observed. S-Indoxacarb demonstrated remarkable insecticidal efficacy. Upon ingestion by S. frugiperda, it induced oxidative damage. Furthermore, S-indoxacarb was metabolized to DCJW, which has a significant role in its insecticidal properties. The selective bioactivity of indoxacarb enantiomers in S. frugiperda might be attributed to the enantiomeric metabolites. These findings offer a new perspective on the selective mechanisms of chiral pesticides. © 2025 Society of Chemical Industry.

Kinetics, pathways, mechanism and toxicity evaluation of chiral pesticide Paichongding during the fermentation of Puer tea

The presence of pesticide residues in tea has garnered increasing scholarly attention. Following the withdrawal of highly toxic pesticides from the market, there is a pressing need for alternative solutions to mitigate pest and disease occurrences in tea plantations. This study focuses on the neonicotinoid chiral pesticide of Paichongding(IPP), which possesses two chiral centers and four distinct isomers. We investigated the selective degradation of Paichongding isomers during the fermentation of Puer tea, tracking intermediate metabolites throughout the process. Using Density Functional Theory (DFT), we estimated the potential active sites of Paichongding and evaluated the toxicity of its intermediate products. Our findings indicate that Paichongding undergoes diastereo-selective degradation during Puer tea fermentation, resulting in the identification of seven key intermediates. Computational analysis revealed that the primary reaction sites of Paichongding are located on the imidazole and tetrahydropyridine rings. Toxicity assessments demonstrated that the metabolites exhibited heightened toxicity towards human genetic material, respiratory functions, and small aquatic organisms.

Chirality in Insecticide Design and Efficacy

Chirality plays a crucial role in the design and efficacy of insecticides, significantly influencing their biological activity, selectivity, and environmental impact. Recent advancements in chiral insecticides have focused on enhancing their effectiveness, reducing toxicity to nontarget organisms, and improving environmental sustainability. This review provides a comprehensive overview of the current state of knowledge on chiral insecticides, including neonicotinoids, isoxazolines, and sulfiliminyls. We discuss the stereochemistry, synthetic development, mode of action, and environmental fate of these compounds. The review highlights the importance of chirality in optimizing insecticidal properties and underscores the need for continued research into novel chiral compounds and advanced synthesis technologies. By understanding the role of chirality, we can develop more effective and environmentally friendly insecticides for sustainable pest management.

Toxicokinetics and bioavailability of indoxacarb enantiomers and their new metabolites in rats

Indoxacarb is a chiral insecticide that consists of two enantiomers, S-(+)-indoxacarb and R-(-)-indoxacarb, of which only S-(+)-indoxacarb has insecticidal activity. Previous enantioselective toxicology studies of indoxacarb focused mostly on simple environmental model organisms. The lack of a toxicology evaluation of indoxacarb conducted in a mammalian system could mean that the extent of the potential health risk posed by the insecticide to humans is not adequately known. In this study, we reported on a new pair of enantiomers, S-IN-RM294 and R-IN-RM294, derived from the metabolic breakdown of S-(+)-indoxacarb and R-(-)-indoxacarb, respectively, in rats. The toxicokinetics of S-(+)-indoxacarb, R-(-)-indoxacarb, S-IN-RM294, and R-IN-RM294 in rats were evaluated to provide a more comprehensive risk assessment of these molecules. The bioavailability and excretion rates of both S-(+)-indoxacarb and R-(-)-indoxacarb were relatively low, which may be due to their faster metabolism and accumulation in the tissues. In addition, there were significant differences in the metabolism and distribution between the two indoxacarb enantiomers and their metabolites in vivo. S-(+)-Indoxacarb was found to be more easily metabolized in the blood compared with R-(-)-indoxacarb, as shown by the differences in pharmacokinetic parameters between oral and intravenous administration. Analysis of their tissue distribution showed that S-(+)-indoxacarb was less likely to accumulate in most tissues. The results obtained for the two metabolites were consistent with those of the two parent compounds. S-IN-RM294 was more readily cleared from the blood and less likely to accumulate in the tissues compared with R-IN-RM294. Therefore, whether from the perspective of insecticidal activity or from the perspective of mammalian and environmental friendliness, the application of optically pure S-(+)-indoxacarb in agriculture may be a more efficient and safer strategy.

Risk assessment of broflanilide for human and non-target terrestrial organisms in cauliflower production

Broflanilide is a newly-developed meta-diamide insecticide, proposed for the control of a wide variety of chewing pests on many crops. In view of the proposed use of broflanilide and its environmental fate, it may be exposed to consumers and non-target organisms, which adversely affect human and the environment. In this paper, a rapid, sensitive and valid UPLC-MS/MS method was established for simultaneous analysis of broflanilide and its two major metabolites, DM-8007 and S (PFP-OH)-8007, in cauliflower. Then, the dissipation behaviors and final residues of broflanilide and its two major metabolites in cauliflower from eight sites with different climatic conditions in China were studied via the described analytical method. In addition, the acute toxicity test of 9.5 % suspension concentrate of broflanilide, broflanilide standard, DM-8007 and S (PFP-OH)-8007 were conducted to non-target terrestrial organisms. Risk assessment for human and non-target terrestrial organisms in cauliflower production was evaluated based on the maximum annual application rates and intervals. The results showed that the highest residue of broflanilide detected in cauliflower samples was all lower than the corresponding MRLs (2 mg/kg) in Japan. Chronic food dietary risk estimates for broflanilide do not exceed 50 % for all the Chinese population groups. Moreover, broflanilide is of low acute toxicity to birds and earthworm, while broflanilide and its metabolites is classified as highly toxic to adult honeybees. Acute risks of broflanilide to birds and earthworms were deemed to be acceptable in a realistic worst-case scenario, while its risk to adult honeybees and ladybug was unacceptable. A protection statement for honeybees and ladybug is required to recognize the high toxicity of broflanilide on related product labels. The study will be conducive to provide guidance for the rational application of broflanilide in cauliflower production.

Pesticide contamination pattern from Morocco, insights into the surveillance situation and health risk assessment: a review

The widespread application of pesticides in Morocco's agriculture renders their monitoring in food and environmental samples very necessary. Recent years have witnessed a growing interest in reporting studies related to the monitoring of pesticide residues in food, water, groundwater, and soil as well as their quantitative health risk assessment. Most published studies have been done by university researchers. However, the lack of research reproducibility remains a problem that considerably limits the possibility of exploiting data from the literature. Our study involves an extensive literature review utilizing search engines with keywords like "pesticide residues," "monitoring," "vegetables and fruits," "water and soil," "risk assessment," and "Morocco" from 2009 to 2023. Analysis of pesticide residues in foodstuffs and environmental samples highlights concerns over compliance with EU regulations, the health risks associated with pesticide exposure, and the necessity for comprehensive monitoring and risk assessment strategies. This paper could help influence policies to develop a strategy and action plan for the sound management of pesticides, including measures to reduce their use, raise awareness, and monitor compliance. Also, this paper could be useful for scientists interested in understanding the current situation and challenges regarding pesticide residues in Morocco, as well as countries with which commercial links exist.

Monitoring 432 potential pesticides in tomatoes produced and commercialized in Souss Massa region-Morocco, using LC-MS/MS and GC-MS/MS

In this work, we monitored 432 pesticide residues in 39 tomato samples (cherry tomato) obtained from local markets in Souss Massa region-Morocco. We used a QuEChERS combined with LC-MS/MS and GC-MS/MS, and the method was validated based on SANTE 11312/2021 guideline. The limits of quantification (LOQ) obtained for most of the pesticides analyzed are at the limit with default EU MRLs or well below other EU MRLs. Recoveries (between 70 and 120%) and RSDs (≤20%) are satisfactory for more than 95% of the analytes at spiking level of 0.01 mg/kg and more than 97% at 0.1 mg/kg. The results indicated that 22 out of 39 tomato samples are positives and the most of our samples had levels lower than the maximum residue levels (MRLs) with average concentrations between 0.011 and 0.156 mg/kg. The most found pesticides were azoxystrobin and difenoconazole in tomato (7 samples). Only buprofezin (0.095 mg/kg) was found above the EU MRLs (0.01 mg/kg). Also, banned pesticides namely benalaxyl, spirodiclofen and imidacloprid have been detected. The results of our study confirm the previous findings and gives insights on the occurrence of different pesticides in tomato samples from Souss Massa region-Morocco.

Enantioselective Behaviors of Chiral Pesticides and Enantiomeric Signatures in Foods and the Environment

Unreasonable application of pesticides may result in residues in the environment and foods. Chiral pesticides consist of two or more enantiomers, which may exhibit different behaviors. This Review intends to provide progress on the enantioselective residues of chiral pesticides in foods. Among the main chiral analytical methods, high performance liquid chromatography (HPLC) is the most frequently utilized. Most chiral pesticides are utilized as racemates; however, due to enantioselective dissipation, bioaccumulation, biodegradation, and chiral conversion, enantiospecific residues have been found in the environment and foods. Some chiral pesticides exhibit strong enantioselectivity, highlighting the importance of evaluation on an enantiomeric level. However, the occurrence characteristics of chiral pesticides in foods and specific enzymes or transport proteins involved in enantioselectivity needs to be further investigated. This Review could help the production of some chiral pesticides to single-enantiomer formulations, thereby reducing pesticide consumption as well as increasing food production and finally reducing human health risks.

Enantioselectivity of indoxacarb enantiomers in Bombyx mori larvae: toxicity, bioaccumulation and biotransformation

BACKGROUND

Indoxacarb is a chiral insecticide with excellent insecticidal activity against lepidopterous insects. Because of their enantioselectivity, chiral pesticides' environmental behavior at the enantiomeric level has been highlighted. The chiral stability, enantioselective bioaccumulation, biotransformation behavior of indoxacarb to a non-target insect silkworm are still unclear.

RESULTS

A chiral analysis method for indoxacarb and its metabolite DCJW in silkworm was developed using liquid chromatography and high-resolution mass spectrometry (HPLC/HRMS). In silkworms, the recoveries of indoxacarb and DCJW were 86.06%-104.52% with relative standard deviation (RSD) < 9.01%. The 96-h lethal concentration (LC₅₀ ) values of R-indoxacarb, S-indoxacarb, and enriched S-indoxacarb (2.333 S/1R) were 1.08 × 10² , 1.92, and 6.89 mg a.i. L^-1 , respectively, according to the acute toxicity test results. When silkworm larvae were exposed to 1/50 of the LC₅₀ concentration, the bioconcentration factor (BCF) of R-indoxacarb was 0.0296-0.318, and the BCF of S-indoxacarb was 0.0125-0.211. In silkworm larvae, the amount of R-DCJW produced by R-indoxacarb was 0.00610 to 2.34 times that of the parent R-indoxacarb, and the amount of S-DCJW produced by S-indoxacarb was 0.125-36.9 times that of the parent S-indoxacarb.

CONCLUSION

There was no chiral transition from S-indoxacarb to R-indoxacarb or a transformation from R-indoxacarb to S-indoxacarb. Indoxacarb was preferentially bioaccumulated in silkworm larva, while S-indoxacarb bioconversion into the metabolite S-DCJW was much greater than R-indoxacarb bioconversion into R-DCJW. This study could improve understanding of the indoxacarb accumulation and transformation process in insects, as well as provide more scientific data for indoxacarb environmental and ecological risk assessment. © 2023 Society of Chemical Industry.

Ecological threat caused by malathion and its chiral metabolite in a honey bee-rape system: Stereoselective exposure risk and the mechanism revealed by proteome

Honey bees play an important role in the ecological environment. Regrettably, a decline in honey bee colonies caused by chemical insecticides has occurred throughout the world. Potential stereoselective toxicity of chiral insecticides may be a hidden source of danger to bee colonies. In this study, the stereoselective exposure risk and mechanism of malathion and its chiral metabolite malaoxon were investigated. The absolute configurations were identified using an electron circular dichroism (ECD) model. Ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was used for chiral separation. In pollen, the initial residues of malathion and malaoxon enantiomers were 3571-3619 and 397-402 μg/kg, respectively, and R-malathion degraded relatively slowly. The oral LD₅₀ values of R-malathion and S-malathion were 0.187 and 0.912 μg/bee with 5 times difference, respectively, and the malaoxon values were 0.633 and 0.766 μg/bee. The Pollen Hazard Quotient (PHQ) was used to evaluate exposure risk. R-malathion showed a higher risk. An analysis of the proteome, including Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and subcellular localization, indicated that energy metabolism and neurotransmitter transport were the main affected pathways. Our results provide a new scheme for the evaluation of the stereoselective exposure risk of chiral pesticides to honey bees.

Sublethal effects of an indoxacarb enantiomer insecticide on Plutella xylostella caterpillar and Chrysoperla sinica predator

Plutella xylostella (L.) is a migratory species and an important insect pest of cruciferous crops worldwide, and Chrysoperla sinica (Tjeder) is a predaceous insect of agricultural and forest pests in the field. Indoxacarb has two enantiomers: (+)-S-indoxacarb and (-)-R-indoxacarb. This study was conducted to clarify the selective toxicity and sublethal effects of both enantiomers on P. xylostella and C. sinica. The (+)-S-indoxacarb isomer had greater acute toxicity to P. xylostella and C. sinica, while (-)-R-indoxacarb had less toxicity to P. xylostella and low toxicity to C. sinica. Lethal concentration 25 % (LC₂₅) of (+)-S-indoxacarb had significant effects on the development, population, and fecundity of P. xylostella and C. sinica. The LC₂₅ concentration of (-)-R-indoxacarb had a significant effect on the oviposition of P. xylostella. The field recommended concentration of (-)-R-indoxacarb significantly affected the pupal stage, adult survival rate, oviposition, and larval survival rate of C. sinica. Both enantiomers could significantly affect the search efficiency, successful attack rate, prey handling time, and maximum predation of C. sinica larvae, and the effects of (+)-S-indoxacarb alone were greater than those of (-)-R-indoxacarb. This study provided evidence of the different selective toxicity, sublethal effects of indoxacarb enantiomers on P. xylostella and C. sinica, which of the results could provide a basis for more rational use of indoxacarb in ecosystems.

Dissipation behavior, residue transfer, and safety evaluation of chlorantraniliprole and indoxacarb during tea growing and brewing by ultrahigh-performance liquid chromatography-tandem mass spectrometry

A reliable and simple analytical method was developed and validated to simultaneously determine chlorantraniliprole and indoxacarb in tea using ultrahigh-performance liquid chromatography-tandem mass spectrometry. The average recoveries of chlorantraniliprole were in the range of 86-110%, with the precision of intraday (n = 5) and interday (n = 15) ranging from 1.9 to 8.4% and from 2.4 to 8.8%, respectively. The average recoveries of indoxacarb were in the range 81-105%, with the precision of intraday (n = 5) and interday (n = 15) ranging from 2.0 to 9.8% and from 2.7 to 9.1%, respectively. The limits of quantification (LOQs) were all 0.01 mg/kg. The results based on the supervised field trials showed that chlorantraniliprole and indoxacarb in two tea samples followed first-order kinetics models with half-lives of 2.2-4.7 days and 2.5-3.5 days, which could be regarded as a moderately degrading pesticide. The terminal residues of chlorantraniliprole and indoxacarb in made tea were below 6.7 and 4.5 mg/kg, respectively, lower than their corresponding maximum residue limits (MRLs) established by several major countries and organizations (50 and 5 mg/kg). The leaching rates of chlorantraniliprole and indoxacarb during the tea brewing ranged from 4.78 to 12.62% and 4.13 to 10.67%, respectively. The chronic intake risk quotient (RQc) values for chlorantraniliprole and indoxacarb were 0.24% and 35.10%, while the acute dietary risk assessment (RQa) value of indoxacarb was 5.8%, which were all much lower than 100%. The results in the present study indicated that the health risk posed by the chlorantraniliprole and indoxacarb mixture pesticides was negligible in tea for consumers at the recommended dosages.