Active Targeted Janus Theranostic Nanoplatforms Enable Chemo-Photothermal Therapy to Inhibit the Growth of Breast Cancer.

Nanoscale structures have been developed to serve various functions in cancer therapy, encompassing areas such as diagnosis, biomedical visualization, tissue regeneration, and drug delivery. Based on biocompatible chitosan oligosaccharides (COS) and gold nanorods (GNRs), we designed the drug delivery systems (GNR@polyacrylic acid-Mn@COS Janus nanoparticles (JNPs)), which achieved paclitaxel (PTX) loaded on the side of GNRs, and the PAA-Mn domain served as magnetic resonance imaging contrast agents. This system was found to be effectively delivered to tumor sites through the enhanced permeability and retention (EPR) effect and the active target of the COS. The uniform JNPs selectively targeted cancer cells instead of normal cells through interacting with the COS on the surface of tumor cells, and the pH/NIR-responsive drug release behavior further enhanced their therapeutic effects. The in vivo effects of JNPs against tumors were evaluated using subcutaneous and orthotopic lung metastasis models, yielding promising outcomes for both tumor diagnosis and cancer treatment. In conclusion, the obtained JNPs hold great promise as a theranostic nanoplatform with synergistic chemotherapeutic and photothermal effects.

Method validation for detection of afidopyropen and M440I007 in tea.

BACKGROUND: Afidopyropen is a novel biorational insecticide for controlling piercing pests with great potential for application in tea gardens that can form the metabolite M440I007 when utilized for crops. However, because of a lack of analytical method for afidopyropen and M440I007 in tea, there is no means of monitoring the residues. Therefore, method development, validation and simultaneous determination of afidopyropen and M440I007 in fresh tea leaves, dried tea and tea infusion is of prime significance. RESULTS: A TPT cartridge-based method was developed for the solid phase extraction of afidopyropen and M440I007 from tea matrices. Extraction and clean-up conditions, including the composition, volume and temperature of elutions, were optimized to achieve the best results. Both targets were extracted using water and acetonitrile, with a water:acetonitrile (v/v) ratio of 4:10 for fresh leaves and 8:10 for dried tea, which were then cleaned and analyzed using ultraperformance liquid chromatography-tandem mass spectrometry. Both analytes demonstrated excellent linearity with a correlation coefficient above 0.998. The optimized analytical method offered limits of quantifications of 0.005, 0.005 and 0.002 mg kg-1 (converted to dried tea) in fresh tea shoots, dried tea and tea infusion for both targets, respectively. Average recoveries of afidopyropen and M440I007 ranged from 79.0% to 101.5%, with relative standard deviations ≤ 14.7%. CONCLUSION: The results showed that the method of determination for these insecticides in tea matrices was practical and efficient. © 2023 Society of Chemical Industry.

SPE-UPLC-MS/MS for Determination of 36 Monomers of Alkylphenol Ethoxylates in Tea.

Alkylphenol ethoxylates (APEOs) represent a non-ionic surfactant widely used as adjuvants in pesticide formulation, which is considered to cause an endocrine-disrupting effect. In the current study, we established a detection method for the APEOs residue in tea based on solid-phase extraction (SPE) for the simultaneous analysis of nonylphenol ethoxylates (NPEOs) and octylphenol ethoxylates (OPEOs) by UPLC-MS/MS. In the spiked concentrations from 0.024 to 125.38 µg/kg for 36 monomers of APEOs (nEO = 3-20), the recoveries of APEOs range from 70.3-110.7% with RSD ≤ 16.9%, except for OPEO20 (61.8%) and NPEO20 (62.9%). The LOQs of OPEOs and NPEOs are 0.024-6.27 and 0.16-5.01 µg/kg, respectively. OPEOs and NPEOs are detected in 50 marketed tea samples with a total concentration of 0.057-12.94 and 0.30-215.89 µg/kg, respectively. The detection rate and the range of the monomers of NPEOs are generally higher than those of OPEOs. The current study provides a theoretical basis for the rational use of APEOs as adjuvants in commercial pesticide production.

The metabolism and dissipation behavior of tolfenpyrad in tea: A comprehensive risk assessment from field to cup.

The metabolites of pesticides usually require rational risk assessment. In the present study, the metabolites of tolfenpyrad (TFP) in tea plants were identified using UPLC-QToF/MS analysis, and the transfer of TFP and its metabolites from tea bushes to consumption was studied for a comprehensive risk assessment. Four metabolites, PT-CA, PT-OH, OH-T-CA, and CA-T-CA, were identified, and PT-CA and PT-OH were detected along with dissipation of the parent TFP under field conditions. During processing, 3.11-50.00 % of TFP was further eliminated. Both PT-CA and PT-OH presented a downward trend (7.97-57.89 %) during green tea processing but an upward trend (34.48-124.17 %) during black tea manufacturing. The leaching rate (LR) of PT-CA (63.04-101.03 %) from dry tea to infusion was much higher than that of TFP (3.06-6.14 %). As PT-OH was no longer detected in tea infusions after 1 d of TFP application, TFP and PT-CA were taken into account in the comprehensive risk assessment. The risk quotient (RQ) assessment indicated a negligible health risk, but PT-CA posed a greater potential risk than TFP to tea consumers. Therefore, this study provides guidance for rational TFP application and suggests the sum of TFP and PT-CA residues as the maximum residual limit (MRL) in tea.

Method Validation for Multi-Pesticide Residue Determination in Chrysanthemum.

The chrysanthemum can be consumed in various forms, representing the "integration of medicine and food". Quantitative analysis of multi-pesticide residues in chrysanthemum matrices is therefore crucial for both product-safety assurance and consumer-risk evaluation. In the present study, a simple and effective method was developed for simultaneously detecting 15 pesticides frequently used in chrysanthemum cultivation in three matrices, including fresh flowers, dry chrysanthemum tea, and infusions. The calibration curves for the pesticides were linear in the 0.01-1 mg kg-1 range, with correlation coefficients greater than 0.99. The limits of quantification (LOQs) for fresh flowers, dry chrysanthemum tea, and infusions were 0.01-0.05 mg kg-1, 0.05 mg kg-1, and 0.001-0.005 mg L-1, respectively. In all selected matrices, satisfactory accuracy and precision were achieved, with recoveries ranging from 75.7 to 118.2% and relative standard deviations (RSDs) less than 20%. The validated method was then used to routinely monitor pesticide residues in 50 commercial chrysanthemum-tea samples. As a result, 56% of samples were detected with 5-13 pesticides. This research presents a method for the efficient analysis of multi-pesticide residues in chrysanthemum matrices.

Residue behavior and risk assessment of afidopyropen and its metabolite M440I007 in tea.

Afidopyropen, a novel insecticide, is highly effective against piercing insects such as the tea leafhopper. The residual levels of afidopyropen and M440I007 in tea cultivation, processing, and brewing were studied. During tea cultivation, afidopyropen dissipated faster in fresh tea shoots in the rainy season (T1/2 of 1.2-2.5 d) than that in the dry season (T1/2 of 3.1-4.4 d); afidopyropen was metabolized into M440I007, the level of which peaked in 1 d, and degraded rapidly (over 90 %) afterward 3 d. The green tea processing steps had little effect on decreasing the afidopyropen residue (PF of 0.90-1.18). Low infusion rates of afidopyropen (16.7 %-17.7 %) and M440I007 (4.1 %-6.2 %) were observed from dry green tea to infusion; furthermore, the risk of ingesting afidopyropen from drinking tea was low, with the risk quotient values < 0.0001. This study can offer guidance on the rational application of afidopyropen in tea plants.

A Tea Plant (Camellia sinensis) FLOWERING LOCUS C-like Gene, CsFLC1, Is Correlated to Bud Dormancy and Triggers Early Flowering in Arabidopsis.

Flowering and bud dormancy are crucial stages in the life cycle of perennial angiosperms in temperate climates. MADS-box family genes are involved in many plant growth and development processes. Here, we identified three MADS-box genes in tea plant belonging to the FLOWERING LOCUS C (CsFLC) family. We monitored CsFLC1 transcription throughout the year and found that CsFLC1 was expressed at a higher level during the winter bud dormancy and flowering phases. To clarify the function of CsFLC1, we developed transgenic Arabidopsis thaliana plants heterologously expressing 35S::CsFLC1. These lines bolted and bloomed earlier than the WT (Col-0), and the seed germination rate was inversely proportional to the increased CsFLC1 expression level. The RNA-seq of 35S::CsFLC1 transgenic Arabidopsis showed that many genes responding to ageing, flower development and leaf senescence were affected, and phytohormone-related pathways were especially enriched. According to the results of hormone content detection and RNA transcript level analysis, CsFLC1 controls flowering time possibly by regulating SOC1, AGL42, SEP3 and AP3 and hormone signaling, accumulation and metabolism. This is the first time a study has identified FLC-like genes and characterized CsFLC1 in tea plant. Our results suggest that CsFLC1 might play dual roles in flowering and winter bud dormancy and provide new insight into the molecular mechanisms of FLC in tea plants as well as other plant species.

Concentrations, generation and risk characterization of phthalimide in tea-derived from folpet or not?

The fungicide folpet is rapidly degraded into phthalimide (PI) during both thermal processing and analytical procedures in sample preparation; thus, its residue definition has been modified into the sum of itself and PI. Tea is one of the world's most popular nonalcoholic beverages, where folpet is not listed as an applicable pesticide. To demonstrate how serious false-positives and overestimation in dietary risk are caused by the application of a new residue definition, the residue pattern of PI in made tea and processed tea leaves, along with its transfer rate during tea brewing and corresponding dietary risk, were investigated in the present study. The results revealed that PI residue in tea ranged from <10 µg/kg to 180 µg/kg with a median value of 10 µg/kg, 7.3 % of which was over the maximum residue limit established by EU (100 µg/kg, expressed as folpet). The PI residue in green tea was obviously higher than that in black, dark and oolong tea. Simulated heating experiments revealed that PI can arise from improper heating of folpet-free fresh tea leaves, and thus green tea bears a higher risk for its manufacturing employing a comparatively higher temperature. The transfer rate of PI during tea brewing was 104 ± 14 %. Nevertheless, the risk of PI through drinking tea was negligible to humans depending on the risk quotient (RQ) value, which was significantly lower than 1.

Siderophore production in pseudomonas SP. strain SP3 enhances iron acquisition in apple rootstock.

AIMS: The purpose of this study was to analyse the effects of siderophore-producing bacteria and bacterial siderophore on the iron nutrition of apple rootstocks under iron-deficient conditions. METHODS AND RESULTS: We isolated three Pseudomonas strains, SP1, SP2 and SP3 from the rhizosphere of the Fe-efficient apple rootstocks using the chrome azurol S agar plate assay. We found that all three strains had the ability to secrete indole acetic acid-like compounds and siderophores, especially SP3. When Fe-inefficient rootstocks treated with SP3 were grown in alkaline soil, an increase in the biomass, root development, and Fe concentration was observed in the plants. In addition, SP3 secreted pyoverdine, a siderophore that can chelate Fe3+ to enhance the bioavailability of Fe for plants. We purified the pyoverdine from the SP3 culture supernatant. Hydroponic experiments were conducted with a Fe-deficient solution supplemented with pyoverdine, resulting in a reduction in the chlorosis caused by Fe deficiency and marked improvement in Fe uptake. CONCLUSIONS: Under iron-deficient conditions, Pseudomonas sp. strain SP3 can effectively promote apple rootstock growth and improve plant iron nutrition by secreting siderophores that enhance Fe availability. SIGNIFICANCE AND IMPACT OF THE STUDY: This study showed that plant growth-promoting rhizobacteria from Fe-efficient plants have the potential to improve iron nutrition in Fe-inefficient plants, and Fe-siderophore chelates can be used as an effective source of iron for apple plants. Based on these findings, it may be possible to develop biological agents such as siderophore-producing bacteria for sustainable agricultural and horticultural production.

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

Chiral pesticides are unique hazardous materials. Here, we systematically studied the potentially harmful products of enantioselective indoxacarb degradation throughout tea growth, processing, and brewing and tested their toxicity to tea geometrid larvae and honeybees. The half-lives of S-indoxacarb and R-indoxacarb during tea growth were 2.6 d and 3.3 d, respectively. There was a trend toward the production of S-indoxacarb from R-indoxacarb. The degradation products IN-JT333, IN-MK638, IN-MF014, and IN-KG433 were also characterized in tea growth and processing and detected. IN-JT333, previously known as a direct insecticidal compound produced by the enzymatic transformation of indoxacarb in insects, was first found in plant samples. The fixation and rolling of green tea and the rolling of black tea were the most important steps that affected indoxacarb and its degradation products. The leaching rates of R-indoxacarb and S-indoxacarb were slightly higher in green tea than in black tea. The maximum leaching rates of IN-MK638 and IN-MF014 during the brewing process reached 89.9% and 94.1%, respectively. Contact toxicity tests with honeybees and tea geometrid larvae in the lab showed that the relative toxicities of the compounds could be ranked as follows: S-indoxacarb > indoxacarb (3S + 1R) ≫ R-indoxacarb. TEST toxicity predictions showed that relative toxicities were ranked IN-KG433 > indoxacarb > IN-JT333 > IN-MK638 > IN-MF014. The toxicity of the degradation product IN-KG433 is higher than that of indoxacarb itself, and its maximum leaching rate is as high as 88.2%. It therefore transfers readily from processed tea to the tea infusion during the brewing process. These findings indicate the need to pay attention to the risk of metabolites and enantiomeric differences and provide new, comprehensive insight into the risk factors for indoxacarb in tea and are relevant to the study of other chiral pesticides.

Uptake, translocation, and metabolism of anthracene in tea plants.

The origin of 9, 10-anthraquinone (AQ) contamination in tea remains unclear at present. The objective of this study was to test the hypothesis that AQ could be produced from the precursor anthracene in tea plantations. To test this hypothesis, the uptake, translocation, and transformation of anthracene in tea (Camellia sinensis) seedlings using hydroponic experimentation was investigated. Anthracene concentrations in tea tissues rose with increased anthracene exposure, which in the roots were significantly (p < 0.05) higher than those in aboveground parts at the end of the exposure. These results indicated that anthracene tended to be adsorbed into tea seedling via the roots and accumulated largely within roots. The three main pathways of anthracene degradation in tea seedlings were suggested: oxygen was incorporated in the 9th and 10th positions of anthracene resulting in AQ (I) and anthrone (II), and naphthalene was formed by ring fission of anthracene via methylanthracene (III). The principal anthracene metabolites were AQ and anthrone. The concentrations of AQ, like anthrone, were markedly elevated in the roots than those in stems throughout the entire exposure period. Moreover, the translocation factors for anthracene and its primary metabolites AQ and anthrone from roots to stems were persistently lower than 0.1, demonstrating a poor translocation from roots to the aboveground regions. However, tea seedlings could take anthracene up from water and translocate it to the leaves. It was a possible risk for AQ contamination in tea leaves continuously exposed to anthracene for long periods of time because tea plants were perennial crops.

Residue degradation, transfer and risk assessment of pyriproxyfen and its metabolites from tea garden to cup by ultra performance liquid chromatography tandem mass spectrometry.

BACKGROUND: Tea is one of the most popular drinks in the world. The growth of tea plant is inseparable from the control of pesticides on diseases and pests. Pyriproxyfen is used as a pesticide substitute to control insect pests in tea gardens, but little is known about its residue degradation. Here, we performed an integrative study of the degradation and metabolism of pyriproxyfen from the tea garden to the cup. RESULTS: The dissipation half-life of pyriproxyfen during tea growth was 2.74 days, and five metabolites PYPAC, PYPA, DPH-Pyr, 5''-OH-Pyr, and 4'-OH-Pyr were generated. The total processing factors for pyriproxyfen in green tea and black tea were 2.41-2.83 and 2.77-3.70, respectively. The residues of pyriproxyfen and its metabolites were affected by different processing steps. The total leaching rates of pyriproxyfen from green tea and black tea into their infusions were 9.8-12.3% and 5.3-13.8%, respectively. The leaching rates of the five metabolites were higher than that of pyriproxyfen and increased the intake risk. CONCLUSION: To ensure safe consumption, the recommended maximum residue limit value of pyriproxyfen in tea can be set to 5 mg kg-1 and the pre-harvest interval can be set to 5 days. © 2022 Society of Chemical Industry.

Dissipation behavior and risk assessment of tolfenpyrad from tea bushes to consuming.

The dissipation behavior of tolfenpyrad, a widely used pyrazole insecticide in tea plantations, was investigated during tea bushes growing, manufacturing and brewing. Tolfenpyrad dissipated fast on the tea bushes with the half-lives of 1.8-2.3 days. Manufacturing processes of green tea and black tea further reduced the tolfenpyrad residue by 3.5%-36.4%. The average processing factors (PFs) of tolfenpyrad ranged from 0.68 to 1.40 and 0.84 to 1.30 during the processing of green tea and black tea, respectively. Then a low infusion factor of 9.8%-19.9% was observed during the brewing of made tea, as the water solubility of tolfenpyrad was only 0.087 mg/L. Therefore, more than 96% of the initial deposition of tolfenpyrad was dissipated and not accessible for consuming. Results of the risk quotient (RQ) assessment also indicated a negligible health risk by tea consumption. Results from this study indicated that the residue of tolfenpyrad can be reduced by proper field management, manufacturing and brewing processes, where field dissipation and brewing were key steps to minimize its risks. Data of this study could also provide guidance for rational application of tolfenpyrad in tea plantations.

Uptake, Accumulation, Translocation, and Subcellular Distribution of Perchlorate in Tea (Camellia sinensis L.) Plants.

Perchlorate, emerging pollution with thyroid toxicity, has a high detection rate in fresh tea leaves. What needs attention is that the uptake characteristic is insufficiently understood. Herein, the uptake, accumulation, and translocation of perchlorate in a tea plant-hydroponic solution system were investigated, of which the mechanism was further lucubrated by subcellular distribution. The perchlorate concentration in tea tissues is ramped up along with the increase in the exposure level and time. The bioaccumulation factor of tea tissues followed the rank: mature leaves > tender leaves > roots. After the seedlings have been transplanted to a perchlorate-free solution, the perchlorate in mature leaves is reduced significantly, accompanied by a progressive increase in perchlorate in new shoots and solutions. The cell-soluble fractions are the major reservoir of perchlorate both for roots (>59%) and leaves (>76%), which precisely explained the translocation within the tea plant-hydroponic solution system. These results not only illuminate the uptake characteristic in tea plants but also improve the understanding of the behavior of perchlorate in higher plants.

Residue dissipation, transfer and safety evaluation of picoxystrobin during tea growing and brewing.

BACKGROUND: Picoxystrobin is a new osmotic and systemic broad-spectrum methoxyacrylate fungicide with a good control effect on tea anthracnose, so it has been proposed to spray picoxystrobin before the occurrence and onset of tea anthracnose during tea bud growth in order to protect them. However, there are few reports about the residue analysis method, field dissipation, terminal residue and risk assessment of picoxystrobin in tea. And there is no scientific and reasonable maximum residue limit of picoxystrobin in green tea. RESULTS: A rapid and sensitive analysis method for picoxystrobin residue in fresh tea leaf, green tea, tea infusion and soil was established by UPLC-MS/MS. The spiked recoveries of picoxystrobin ranged from 73.1% to 111.0%, with relative standard deviations from 1.8% to 9.2%. The limits of quantitation were 20 µg kg-1 in green tea, 8 µg kg-1 in fresh tea leaves and soil and 0.16 µg kg-1 in tea infusion. The dissipation half-lives of picoxystrobin in fresh tea leaf and soil were 2.7-6.8 and 2.5-14.4 days, respectively. And the maximum residue of picoxystrobin in green tea was 15.28 mg kg-1 with PHI at 10 days for terminal test. The total leaching rate of picoxystrobin during green tea brewing was lower than 35.8%. CONCLUSIONS: According to safety evaluation, the RQc and RQa values of picoxystrobin in tea after 5 to 14 days for the last application were significantly lower than 1. Therefore, the maximum residue limit value of picoxystrobin in tea that we suggest to set at 20 mg kg-1 can ensure the safety of tea for human drinking. © 2020 Society of Chemical Industry.

Residue analysis and dietary exposure risk assessment of acibenzolar-S-methyl and its metabolite acibenzolar acid in potato, garlic, cabbage, grape and tomato.

Acibenzolar-S-methyl (ASM) is one of the most effective plant resistance activators and protects against a broad spectrum of fungal, bacterial and viral pathogens. A rapid, efficient and high-throughput analysis method for ASM and its metabolite acibenzolar acid in fruits and vegetables was developed using potato, garlic, cabbage, grape and tomato as representative commodities by modified QuEChERS and UPLC-MS/MS. The modified procedure showed satisfying recoveries (70-108%) fortified in the range of 0.01-1 mg/kg with relative standard deviations (RSDs) lower than 17.7%. With the established analytical method, the dietary risk of ASM in fruits and vegetables from Chinese markets were further monitored using risk quotient (RQ) method. The RQ value based on ASM residue in China are far less than 1, elucidating that the potential health risk induced by ASM ingestion for Chinese population is not significant. Comparing the residue and risk assessment results of ASM in agricultural products in China to those in Codex, the maximum residue limits (MRLs) for ASM on garlic, cabbage and tomato established by CAC (Codex Alimentarius Commission) can be safely adopted in China, whereas the MRLs on potato and grape in China should be proposed as 0.01 mg/kg.

The degradation and metabolism of chlorfluazuron and flonicamid in tea: A risk assessment from tea garden to cup.

Degradation and metabolism of chlorfluazuron and flonicamid from tea garden to cup were simultaneously investigated by a modified QuEChERS method coupled with UPLC-MS/MS quantification. The dissipation half-lives of chlorfluazuron, flonicamid, and total flonicamid (the sum of flonicamid and its metabolites TFNG, TFNA, and TFNA-AM) in fresh tea leaves during tea growth were 6.0 d, 4.8 d, and 8.1 d, respectively. TFNG and TFNA were generated during tea growth. After tea processing, the residues of chlorfluazuron, flonicamid, and its metabolites in black tea were higher than those in green tea. The average processing factors of chlorfluazuron, flonicamid, and total flonicamid in black tea were 2.54, 3.02, and 2.87, respectively, while in green tea they were 2.40, 2.93, and 2.79, respectively. TFNG, TFNA, and TFNA-AM were formed rapidly during the drying step. Considering the influence of water content at various processing steps, the average loss rates of chlorfluazuron, flonicamid, and total flonicamid residue from fresh tea leaves to black tea were 16.7%, 33.8%, and 20.7%, respectively, and 29.6%, 14.0% and 18.2%, respectively, in the case of green tea. The highest leaching rates of chlorfluazuron, flonicamid, and total flonicamid during tea brewing were 6.8%, 97.0%, and 97.4%, respectively, in black tea infusion, and 6.0%, 98.9%, and 98.6%, respectively, in green tea infusion. The metabolites, especially TFNG, had a higher leaching rate during tea brewing. The migration of chlorfluazuron from fresh leaves to tea infusion was low, and the migration of flonicamid was high. The RQc and RQa of chlorfluazuron and total flonicamid were less than 1. This result indicates that the potential dietary intake risk of chlorfluazuron from tea is negligible. However, the risk of total flonicamid intake is three times higher than that of chlorfluazuron. There is a potential risk of intake of flonicamid and its metabolites in tea for human consumption.

Residue behavior and safety evaluation of pymetrozine in tea.

BACKGROUND: Pymetrozine is a widely used pesticide. It is challenging to analyze and difficult to manage due to the large gap in its global maximum residue limits (MRLs) in tea. The development of a high-efficiency detection method for the evaluation of the transfer of residual pymetrozine from tea plantations to tea cups is therefore of prime significance. RESULTS: An analytical method for the determination of pymetrozine residues in tea was established based on Cleanert PCX solid-phase extraction. The average recoveries were 72.2-93.7%, with relative standard deviations (RSDs) of less than 12%. The limits of quantification (LOQs) were 0.005 mg·kg-1 in fresh tea leaves and dry tea, and 0.00025 mg·L-1 in tea brew. Pymetrozine degraded rapidly in tea plants with a half-life (t1/2 ) of 1.9 days in open tea plantations, and decreased by 9.4-23.7% in the green tea-processing procedure, which was concentration dependent. The residual pymetrozine levels in green tea collected at 6 and 21 days were below the MRLs in China and EU at a dosage of 30 g a.i. ha-1 , respectively. The leaching rates of pymetrozine from dry tea to tea brew were 58.7-96.3%. Hazard quotient (HQ) values of pymetrozine were significantly <100% when tea shoots were plucked in 6 days, which indicated a negligible risk to humans. CONCLUSION: This work allows the determination of residual pymetrozine in tea and illustrates a low intake risk with the use of pymetrozine in tea plantations. It could serve as reference for further regulation consideration for maximum residue limits (MRLs). © 2020 Society of Chemical Industry.

Enantioselective residue analysis of oxathiapiprolin and its metabolite in tea and other crops by ultra-high performance liquid chromatography-tandem mass spectrometry.

Oxathiapiprolin is the first chiral piperidinyl thiazole isoxazoline fungicide developed to control downy mildew and other diseases, and there were no prior reports on its enantiomeric residue. In this study, a modified quick, easy, cheap, effective, rugged, and safe extraction and purification method followed by ultra-high performance liquid chromatography-tandem mass spectrometry determination was first developed and validated for the residue analysis of oxathiapiprolin enantiomers and its metabolite IN-E8S72 in green tea and other crops. Oxathiapiprolin enantiomers and IN-E8S72 were separated on a chiral Lux Cellulose-3 column with the use of 0.1% formic acid in acetonitrile and 5 mmol/L ammonium acetate in water as mobile phases. IN-E8S72 was eluted first, followed by (-)-oxathiapiprolin, and then (+)-oxathiapiprolin. The recoveries ranged from 53.3 to 125.3% with relative standard deviations ranging from 1.4 to 16.0%. The limits of quantification for (-)-oxathiapiprolin and (+)-oxathiapiprolin were 0.005 mg/kg in romaine lettuce, head cabbage, potato, grape, and garlic, 0.01 mg/kg in soybean and pea, and 0.025 mg/kg in green tea and dry pepper. The limits of quantification of IN-E8S72 were twice those of (-)-oxathiapiprolin. Screening results with real market samples indicated that there was no enantiomeric excess in the oxathiapiprolin residue in romaine lettuce.

Integrated transcriptomic and metabolomic analyses reveal the effects of callose deposition and multihormone signal transduction pathways on the tea plant-Colletotrichum camelliae interaction.

Colletotrichum infects diverse hosts, including tea plants, and can lead to crop failure. Numerous studies have reported that biological processes are involved in the resistance of tea plants to Colletotrichum spp. However, the molecular and biochemical responses in the host during this interaction are unclear. Cuttings of the tea cultivar Longjing 43 (LJ43) were inoculated with a conidial suspension of Colletotrichum camelliae, and water-sprayed cuttings were used as controls. In total, 10,592 differentially expressed genes (DEGs) were identified from the transcriptomic data of the tea plants and were significantly enriched in callose deposition and the biosynthesis of various phytohormones. Subsequently, 3,555 mass spectra peaks were obtained by LC-MS detection in the negative ion mode, and 27, 18 and 81 differentially expressed metabolites (DEMs) were identified in the tea leaves at 12 hpi, 24 hpi and 72 hpi, respectively. The metabolomic analysis also revealed that the levels of the precursors and intermediate products of jasmonic acid (JA) and indole-3-acetate (IAA) biosynthesis were significantly increased during the interaction, especially when the symptoms became apparent. In conclusion, we suggest that callose deposition and various phytohormone signaling systems play important roles in the tea plant-C. camelliae interaction.