Asymmetric Total Synthesis of (+)-Chuanxiongnolide L1 via a Stereoselective Oxidative Dearomatization/Diels-Alder Strategy.

The first asymmetric total synthesis of chuanxiongnolide L1 was achieved in 16 steps and 1.9% overall yield by employing a bioinspired chiral auxiliary strategy. The key steps involving asymmetric oxidative dearomatization of chiral amino ether and subsequent asymmetric Diels-Alder reaction of the resulting masked chiral ortho-benzoquinone were adopted.

Resistance risk assessment of mefentrifluconazole in Corynespora cassiicola and the control of cucumber target spot by a two-way mixture of mefentrifluconazole and prochloraz.

The cucumber target spot, caused by Corynespora cassiicola, is a major cucumber disease in China. Mefentrifluconazole, a new triazole fungicide, exhibits remarkable efficacy in controlling cucumber target spot. However, the resistance risk and mechanism remain unclear. In this study, the inhibitory activity of mefentrifluconazole against 101 C. cassiicola isolates was determined, and the results indicated that the EC50 values ranged between 0.15 and 12.85 µg/mL, with a mean of 4.76 µg/mL. Fourteen mefentrifluconazole-resistant mutants of C. cassiicola were generated from six parental isolates in the laboratory through fungicide adaptation or UV irradiation. The resistance was relatively stable after ten consecutive transfers on a fungicide-free medium. No cross-resistance was observed between mefentrifluconazole and pyraclostrobin, fluopyram, prochloraz, mancozeb, or difenoconazole. Investigations into the biological characteristics of the resistant mutants revealed that six resistant mutants exhibited an enhanced compound fitness index (CFI) compared to the parental isolates, while others displayed a reduced or comparable CFI. The overexpression of CcCYP51A and CcCYP51B was detected in the resistant mutants, regardless of the presence or absence of mefentrifluconazole. Additionally, a two-way mixture of mefentrifluconazole and prochloraz at a concentration of 7:3 demonstrated superior control efficacy against the cucumber target spot, achieving a protection rate of 80%. In conclusion, this study suggests that the risk of C. cassiicola developing resistance to mefentrifluconazole is medium, and the overexpression of CcCYP51A and CcCYP51B might be associated with mefentrifluconazole resistance in C. cassiicola. The mefentrifluconazole and prochloraz two-way mixture presented promising control efficacy against the cucumber target spot.

Resistance to the DMI fungicide mefentrifluconazole in Monilinia fructicola: risk assessment and resistance basis analysis.

BACKGROUND: Brown rot disease, caused by Monilinia fructicola, poses a significant challenge to peach production in China. The efficacy of mefentrifluconazole, a new triazole fungicide, in controlling brown rot in peaches has been remarkable. However, the resistance risk and mechanism associated with this fungicide remain unclear. This study was designed to assess the resistance risk of M. fructicola to mefentrifluconazole and reveal the potential resistance mechanism. RESULTS: The mean median effective concentration (EC50 ) of 101 M. fructicola isolates to mefentrifluconazole was 0.003 µg mL-1 , and the sensitivity exhibited a unimodal distribution. Seven mefentrifluconazole-resistant mutants were generated from three parental isolates in the laboratory through fungicide adaption. The biological characteristics of the resistant mutants revealed that three of them exhibited enhanced survival fitness compared to the parental isolates, whereas the remaining four mutants displayed reduced survival fitness. Mefentrifluconazole showed strong positive cross-resistance with fenbuconazole, whereas no cross-resistance was observed with pyrimethanil, procymidone or pydiflumetofen. No overexpression of MfCYP51 gene was detected in the resistant mutants. Multiple sequence alignment revealed that three resistant mutants (MXSB2-2, Mf12-1 and Mf12-2) had a point mutation (G461S) in MfCYP51 protein. Molecular docking techniques confirmed the contribution of this point mutation to mefentrifluconazole resistance. CONCLUSION: The risk of M. fructicola developing resistance to mefentrifluconazole is relatively low-to-medium and point mutation G461S in MfCYP51 could confer mefentrifluconazole resistance in M. fructicola. This study provided essential data for monitoring the emergence of resistance and developing resistance management strategies for mefentrifluconazole. © 2023 Society of Chemical Industry.

Three point mutations in AaCYP51 combined with induced overexpression of AaCYP51 conferred low-level resistance to mefentrifluconazole in Alternaria alternata.

Tomato early blight is a significant disease that causes substantial losses to tomato yield and quality. Mefentrifluconazole, an isopropanol-azole subgroup of triazole fungicides, has been registered in China for controlling various plant diseases, including tomato early blight, grape anthracnose, and apple brown spot. However, limited information is available on the mefentrifluconazole resistance risk and mechanism in plant pathogens. The sensitivity to mefentrifluconazole of 122 isolates of Alternaria alternata, one of the causal agents of tomato early blight, collected from different provinces in China, was evaluated. The results showed a unimodal curve for the sensitivity frequency, with an average EC50 of 0.306 µg/mL. Through fungicide adaption, six resistant mutants (N4, N5, T4, T5, NG1, and NG10) were obtained from three parental isolates, with a mutation frequency of 3.28 × 10-4 and resistance factors ranging between 19 and 147. The survival fitness of the resistant mutants, except for NG1, was significantly lower than that of their parental isolates. Positive cross-resistance was observed between mefentrifluconazole and difenoconazole or fenbuconazole, whereas no cross-resistance was found with three non-DMI fungicides. Furthermore, three distinct point mutations were detected in the AaCYP51 protein of the resistant mutants: I300S in T4 and T5; A303T in N4, NG1, and NG10; and A303V in N5. Compared to the parental isolates, the AaCYP51 gene was overexpressed in all six resistant mutants when treated with mefentrifluconazole. In summary, the resistance risk of A. alternata to mefentrifluconazole was low, and point mutations and overexpression of the AaCYP51 gene were identified as contributing factors to mefentrifluconazole resistance in A. alternata.

Access to Fully Substituted Dihydroindazoles Via Hexadehydro-Diels-Alder/[3 + 2] Cycloaddition.

A cascade hexadehydro-Diels-Alder (HDDA)/[3 + 2] cycloaddition reaction between tetrayne and N,N'-cyclic acylhydrazone is described. This strategy allows the efficient construction of fully substituted 2,3-dihydro-1H-indazole scaffolds which have insecticidal activity against the third instar larvae of Mythimna separata.

Furan Synthesis via a Tandem 1,2-Acyloxy Migration/[3 + 2] Cycloaddition/Aromatization of Enol Ether-Tethered Propargylic Esters.

An effective method for the synthesis of furans is developed via a tandem 1,2-acyloxy migration/intramolecular [3 + 2] cycloaddition/aromatization of enol ether-tethered propargylic esters. The reaction exhibits excellent functional group tolerance, broad substrate scope, and excellent chemoselectivity. The isolation of dihydrofuran intermediates in some cases gives more insight into the [3 + 2] cycloisomerization process.

Structural Diversity Design, Synthesis, and Insecticidal Activity Analysis of Ester-Containing Isoxazoline Derivatives Acting on the GABA Receptor.

To explore insecticides targeting the γ-aminobutyric acid (GABA) receptor, two series of novel isoxazoline derivatives containing sulfonic and carboxylic esters were designed and synthesized. Their insecticidal activities against Plutella xylostella, Mythimna separata, and Aedes aegypti larvae and their structure-activity relationship were investigated. The sulfonate-containing isoxazoline derivatives (10k-q) exhibited promising insecticidal activities against the three insect larvae. Compound 10o displayed excellent activities with LC50 values of 8.32, 5.23, and 0.35 µg/mL at 48 h against P. xylostella, M. separata, and A. aegypti larvae, respectively, which were better than or similar to those of avermectin. Furthermore, compound 10o exhibited a faster insecticidal effect than avermectin against M. separata. The mode of action of 10o was preliminarily verified by molecular docking, theoretical calculations, and measurement of glutamate decarboxylase and glutamic pyruvic transaminase activities. Compound 10o is a novel insecticidal candidate acting on GABA receptors, which could guide the discovery of isoxazoline insecticides.

Comparative toxicity of multiple exposure routes of pyraclostrobin in adult zebrafish (Danio rerio).

Pyraclostrobin, one of the most widely used fungicides globally, is highly toxic to aquatic organisms, which restricts its application in paddy fields. Most studies have focused on the molecular mechanism of pyraclostrobin toxicity; however, the exposure routes and target organs of pyraclostrobin in fish are poorly known. Here, we found that the lethal effects of aquatic exposure, head immersion, trunk immersion and oral exposure on the toxicity and accumulation of pyraclostrobin in adult zebrafish were different. The major pathway leading to pyraclostrobin accumulation, followed by high hazard to fish, was crossing over the gill rather than the intestine or skin. Additionally, serious histological abnormalities, mitochondrial dysfunction, energy deficiency and respiratory impairment occurred in the gills, while no overt change was observed in the heart and brain at the organic and cellular levels. This result suggested that the gill is the dominant portal and target organ of pyraclostrobin in fish, a fact that has been further verified by intravenous injection. The differences in the toxicity and translocation factor of crystalline and dissolved pyraclostrobin in fish demonstrated that reducing the concentration in the branchial environment is a vital direction for the future design of an effective toxicity regulation strategy to protect key sites from pyraclostrobin attack.

The Bioactivity and Efficacy of Benzovindiflupyr Against Corynespora cassiicola, the Causal Agent of Cucumber Corynespora Leaf Spot.

Corynespora cassiicola, which causes Corynespora leaf spot, results in considerable yield loss of cucumber grown in greenhouses. Frequent reports of reduced efficacy and control failure of fungicides warrant new, efficient alternative chemistries. In this study, the sensitivity of C. cassiicola to benzovindiflupyr was evaluated using a collection of 81 isolates collected from Shandong, China. The mean EC50 values for mycelial growth, spore germination, and germ tube elongation of C. cassiicola were 0.69 ± 0.44, 0.12 ± 0.063, and 0.13 ± 0.076 µg ml-1, respectively. Benzovindiflupyr treatment led to a reduced respiration rate and ATP production of C. cassiicola and decreased spore pathogenicity by 21.9% on average. Additionally, detached cucumber leaves sprayed with fungicides before or after inoculation were used to assess the efficacy of benzovindiflupyr against C. cassiicola. Benzovindiflupyr (150 µg ml-1) exhibited preventive and curative efficacies of 86.9 and 77.1%, respectively. Benzovindiflupyr at 150 g a.i. ha-1 provided over 70% efficacy in field trials performed in 2018 and 2019, which was significantly higher than that of the reference fungicides fluopyram and fluxapyroxad at the same dose. Furthermore, the yield of commercial cucumber increased as disease incidence decreased. Our findings pave the way for the introduction of benzovindiflupyr in the integrated management of Corynespora leaf spot.

Determination of pyraclostrobin dynamic residual distribution in tilapia tissues by UPLC-MS/MS under acute toxicity conditions.

As a lipophilic fungicide, pyraclostrobin is highly toxic to aquatic organisms, especially to fish. In recent years, research has mainly focused on the pyraclostrobin residue in fish tissues under chronic toxicity, but less is known about its distribution in fish tissues under acute toxicity conditions. In this study, the distribution of pyraclostrobin in fish tissues (blood, liver, muscle and gill) was determined by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The purification effects of different purification materials [1) mixtures of PSA, C18 and MgSO4; 2) QuEChERS-PC; and 3) Oasis HLB SPE] were compared for the detection of pyraclostrobin in fish tissues. Finally, the quick and easy clean-up tool of the Oasis HLB SPE procedure was selected. Under optimum conditions, the linearities had a good relationship (determination coefficient R2 > 0.999). The mean recoveries of the analyte for all tested concentrations ranged from 86.94% to 108.81% with RSDs of 0.7%-4.9%. The pyraclostrobin residue amount was much different in fish tissues. Furthermore, the pyraclostrobin residue in different fish tissues increased initially and then decreased gradually. The concentrations in each tissue were initially ranked before 120 min in the following order: gill > liver > blood > muscle. These phenomena may be attributed to the stress response of fish under acute poisoning. This is the first study to document the distribution of pyraclostrobin in fish tissues under acute toxicity conditions, and it provides reference for the management of agrochemicals in terms of aquatic ecological risks.

Binary mixtures of alcohol ethoxylates, nonylphenol ethoxylates and pesticides exhibit comparative bioactivity against three pests and toxicological risks to aquatic organisms.

Nonylphenol ethoxylates are widely used surfactants in the industry and agriculture. However, seeking for alternatives has been imperative considering their effects of the hormonal and other toxicological risks. In the current study, the synergistic effects of nonylphenol ethoxylates or alcohol ethoxylates on the bioactivity of indoxacarb and acetamiprid were compared. Results showed that synergistic ratios of nonylphenol ethoxylates (TX-7∼TX-30) and alcohol ethoxylates (MOA-5∼MOA-20) against Spodoptera exigua, Agrotis ipsilon and Aphis citricola decreased with the EO (ethylene oxide) numbers, although different magnitudes of decreases were observed. Single toxicities of all ethoxylates to Daphnia magna and Brachydanio rerio also dramatically decreased with the EO numbers. In terms of joint toxicity, the combined effects of all ethoxylates and pesticides upon D. magna turned from synergism to antagonism with the increasing EO numbers; the combined effects of nonylphenol ethoxylates and pesticides turned from synergism to antagonism with the increasing EO numbers of ethoxylates, whereas alcohol ethoxylates and pesticides always showed antagonistic effects whatever EO numbers. Overall, alcohol ethoxylates may be potential alternatives for nonylphenol ethoxylates as they exhibited nearly comparative bioactivity against tested pests and toxicities to D. magna and B. rerio.

Oxysterol-binding protein-related protein 2 is not essential for Phytophthora sojae based on CRISPR/Cas9 deletions.

Oxysterol-binding protein (OSBP)-related proteins (ORPs) are a large conserved family of lipid transfer proteins in eukaryotes. In oomycetes, some ORPs are the target of the novel oomycide oxathiapiprolin. By searching the Phytophthora sojae genome database, two ORP proteins, PsORP1 (Protein ID: 558498) and PsORP2 (Protein ID: 470921), were found. Here, we investigated the biological function of PsORP2. The expression level of PsORP2 was higher in germinated cysts and late infection than in other developmental stages. However, deletion of PsORP2 using CRISPR/Cas9 had no significant effect on sporangia production, zoospore production, cyst germination, oospore production, virulence or oxathiapiprolin sensitivity. PsORP1 also was not upregulated in ΔPsORP2 transformants. Collectively, our studies demonstrate that PsORP2 is not an essential protein for development or virulence in P. sojae under the conditions we tested.

Positive-Charge Functionalized Mesoporous Silica Nanoparticles as Nanocarriers for Controlled 2,4-Dichlorophenoxy Acetic Acid Sodium Salt Release.

Because of its relatively high water solubility and mobility, 2,4-dichlorophenoxy acetic acid (2,4-D) has a high leaching potential threatening the surface water and groundwater. Controlled release formulations of 2,4-D could alleviate the adverse effects on the environment. In the present study, positive-charge functionalized mesoporous silica nanoparticles (MSNs) were facilely synthesized by incorporating trimethylammonium (TA) groups onto MSNs via a postgrafting method. 2,4-D sodium salt, the anionic form of 2,4-D, was effectively loaded into these positively charged MSN-TA nanoparticles. The loading content can be greatly improved to 21.7% compared to using bare MSNs as a single encapsulant (1.5%). Pesticide loading and release patterns were pH, ionic strength and temperature responsive, which were mainly dominated by the electrostatic interactions. Soil column experiments clearly demonstrated that MSN-TA can decrease the soil leaching of 2, 4-D sodium salt. Moreover, this novel nanoformulation showed good bioactivity on target plant without adverse effects on the growth of nontarget plant. This strategy based on electrostatic interactions could be widely applied to charge carrying agrochemicals using carriers bearing opposite charges to alleviate the potential adverse effects on the environment.

Determination of Inorganic Cations and Anions in Chitooligosaccharides by Ion Chromatography with Conductivity Detection.

Chitooligosaccharides (COSs) are a promising drug candidate and food ingredient because they are innately biocompatible, non-toxic, and non-allergenic to living tissues. Therefore, the impurities in COSs must be clearly elucidated and precisely determined. As for COSs, most analytical methods focus on the determination of the average degrees of polymerization (DPs) and deacetylation (DD), as well as separation and analysis of the single COSs with different DPs. However, little is known about the concentrations of inorganic cations and anions in COSs. In the present study, an efficient and sensitive ion chromatography coupled with conductivity detection (IC-CD) for the determination of inorganic cations Na⁺, NH4⁺, K⁺, Mg2+, Ca2+, and chloride, acetate and lactate anions was developed. Detection limits were 0.01-0.05 µM for cations and 0.5-0.6 µM for anions. The linear range was 0.001-0.8 mM. The optimized analysis was carried out on IonPac CS12A and IonPac AS12A analytical column for cations and anions, respectively, using isocratic elution with 20 mM methanesulfonic acid and 4 mM sodium hydroxide aqueous solution as the mobile phase at a 1.0 mL/min flow rate. Quality parameters, including precision and accuracy, were fully validated and found to be satisfactory. The fully validated IC-CD method was readily applied for the quantification of various cations and anions in commercial COS technical concentrate.

Validated HPAEC-PAD Method for the Determination of Fully Deacetylated Chitooligosaccharides.

An efficient and sensitive analytical method based on high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) was established for the simultaneous separation and determination of glucosamine (GlcN)1 and chitooligosaccharides (COS) ranging from (GlcN)2 to (GlcN)6 without prior derivatization. Detection limits were 0.003 to 0.016 mg/L (corresponding to 0.4-0.6 pmol), and the linear range was 0.2 to 10 mg/L. The optimized analysis was carried out on a CarboPac-PA100 analytical column (4 × 250 mm) using isocratic elution with 0.2 M aqueous sodium hydroxide-water mixture (10:90, v/v) as the mobile phase at a 0.4 mL/min flow rate. Regression equations revealed a good linear relationship (R² = 0.9979-0.9995, n = 7) within the test ranges. Quality parameters, including precision and accuracy, were fully validated and found to be satisfactory. The fully validated HPAEC-PAD method was readily applied for the quantification of (GlcN)1-6 in a commercial COS technical concentrate. The established method was also used to monitor the acid hydrolysis of a COS technical concentrate to ensure optimization of reaction conditions and minimization of (GlcN)1 degradation.

[Acute toxicity of different type pesticide surfactants to Daphnia magna].

By using the standard test methods in Experimental Guideline for Environmental Safety Evaluation of Chemical Pesticide to aquatic organisms, a comparative study was conducted on the acute toxicity of 39 nonionic, 6 anionic, and 3 cationic surfactants to Daphnia magna. The acute toxicity of three cationic surfactants 1427, 1227 and C8-10 to D. magna belonged to virulent level, and the toxicity of 1427 was the highest, with the EC50 value being 0.97 x 10(-2) mg x L(-1). The acute toxicity of nonionic surfactants polyoxyethylene ether castor oil EL, Tween, and Span emulsifiers belonged to low level, but the toxicity of alkylphenol polyoxyethylene ether and fatty alcohol polyoxyethylene ether surfactants was relatively high, of which, AEO-7 and AEO-5 displayed high toxicity, with the EC50 value being 0.82 and 0.97 mg x L(-1), respectively. In these surfactants, the more liposolubility, the higher the toxicity was. Most of the anionic surfactants were medium in toxicity, but the acute toxicity of NNO belonged to high toxicity, with the EC50 value being 0.17 mg x L(-1).