Development of new sustainable pyridinium ionic liquids: From reactivity studies to mechanism-based activity predictions.

CONTEXT: This study addresses the development of sustainable pyridinium ionic liquids (ILs) because of their potential applications in agriculture and pharmaceuticals. Pyridinium-based ILs are known for their low melting points, high thermal stability, and moderate solvation properties. We synthesized three novel pyridinium-based ILs: 1-(2-(isopentyloxy)-2-oxoethyl)pyridin-1-ium chloride, 1-(2-(hexyloxy)-2-oxoethyl)pyridin-1-ium chloride, and 1-(2-(benzyloxy)-2-oxoethyl)pyridin-1-ium chloride. The biological activities of these compounds were evaluated through plant growth promotion, herbicidal, and insecticidal assays. Our results show that the benzyloxy derivative significantly enhances wheat and cucumber growth, whereas the isopentyloxy compound has potent herbicidal effects. Computational methods, including DFT calculations and molecular docking, were applied to understand the structure‒activity relationships (SARs) and mechanisms of action. METHODS: The computational techniques involved dispersion-corrected density functional theory (DFT) with the B3LYP functional and the 6-311G** basis set. Grimme's D3 corrections were included to account for dispersion interactions. The calculations were performed via GAMESS-US software. Quantum descriptors of reactivity, such as ionization potential, electron affinity, chemical potential, and electrophilicity index, were derived from the HOMO and LUMO energies. Molecular docking studies were conducted via the CB-Dock server via AutoDock Vina software to predict binding affinities to cancer-related proteins. Petra/Osiris/Molinspiration (POM) analysis was used to predict the drug likeness and other pharmaceutical properties of the synthesized ILs.

The effect of combinations of a glyphosate-based herbicide with various clinically used antibiotics on phenotypic traits of Gram-negative species from the ESKAPEE group.

The emission of glyphosate and antibiotic residues from human activities threatens the diversity and functioning of the microbial community. This study examines the impact of a glyphosate-based herbicide (GBH) and common antibiotics on Gram-negative bacteria within the ESKAPEE group (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp. and Escherichia coli). Ten strains, including type and multidrug-resistant strains for each species were analysed and eight antibiotics (cefotaxime, meropenem, aztreonam, ciprofloxacin, gentamicin, tigecycline, sulfamethoxazole-trimethoprim, and colistin) were combined with the GBH. While most combinations yielded additive or indifferent effects in 70 associations, antagonistic effects were observed with ciprofloxacin and gentamicin in five strains. GBH notably decreased the minimum inhibitory concentration of colistin in eight strains and displayed synergistic activity with meropenem against metallo-ß-lactamase (MBL)-producing strains. Investigation into the effect of GBH properties on outer membrane permeability involved exposing strains to a combination of this GBH and vancomycin. Results indicated that GBH rendered strains sensitive to vancomycin, which is typically ineffective against Gram-negative bacteria. Furthermore, we examined the impact of GBH in combination with three carbapenem agents on 14 strains exhibiting varying carbapenem-resistance mechanisms to assess its effect on carbapenemase activity. The GBH efficiently inhibited MBL activity, demonstrating similar effects to EDTA (ethylenediaminetetraacetic acid). Chelating effect of GBH may have multifaceted impacts on bacterial cells, potentially by increasing outer membrane permeability and inactivating metalloenzyme activity.

Novel mutations in acetolactate synthase confer high levels of resistance to tribenuron-methyl in Fagopyrum tataricum.

Tartary buckwheat (Fagopyrum tataricum) field weeds are rich in species, with many weeds causing reduced quality, yield, and crop failure. The selection of herbicide-resistant Tartary buckwheat varieties, while applying low-toxicity and efficient herbicides as a complementary weed control system, is one way to improve Tartary buckwheat yield and quality. Therefore, the development of herbicide-resistant varieties is important for the breeding of Tartary buckwheat. In this experiment, 50 mM ethyl methyl sulfonate solution was used to treat Tartary buckwheat seeds (M1) and then planted in the field. Harvested seeds (M2) were planted in the experiment field of Guizhou University, and when seedlings had 5-7 leaves, the seedlings were sprayed with 166 mg/L tribenuron-methyl (TBM). A total of 15 resistant plants were obtained, of which three were highly resistant. Using the homologous cloning method, an acetolactate synthase (ALS) gene encoding 547 amino acids was identified in Tartary buckwheat. A GTG (valine) to GGA (glycine) mutation (V409G) occurred at position 409 of the ALS gene in the high tribenuron-methyl resistant mutant sm113. The dm36 mutant harbored a double mutation, a deletion mutation at position 405, and a GTG (valine) to GGA (glycine) mutation (V411G) at position 411. The dm110 mutant underwent a double mutation: an ATG (methionine) to AGG (arginine) mutation (M333R) at position 333 and an insertion mutation at position 372. The synthesis of Chl a, Chl b, total Chl, and Car was significantly inhibited by TBM treatment. TBM was more efficient at suppressing the growth of wild-type plants than that of mutant plants. Antioxidant enzyme activities such as ascorbate peroxidase, peroxidase, and superoxide dismutase were significantly higher in resistant plants than in wild-type after spraying with TBM; malondialdehyde content was significantly lower than in wild-type plants after spraying with TBM. Plants with a single-site mutation in the ALS gene could survive, but their growth was affected by herbicide application. In contrast, plants with dual-site mutations in the ALS gene were not affected, indicating that plants with dual-site mutations in the ALS gene showed higher levels of resistance than plants with a single-site mutation in the ALS gene.

Low expression of auxin receptor EcAFB4 confers resistance to florpyrauxifen-benzyl in Echinochloa crus-galli (L.) P. Beauv.

Echinochloa crus-galli (L.) P. Beauv is a monocotyledonous weed that seriously infests rice fields. Florpyrauxifen-benzyl, a novel synthetic auxin herbicide commercialized in China in 2018, is an herbicide for controlling E. crus-galli. However, a suspected resistant population (R) collected in 2012 showed resistance to the previously unused florpyrauxifen-benzyl. Whole-plant dose-response bioassay indicated that the R population evolved high resistance to quinclorac and florpyrauxifen-benzyl. Pretreatment with P450 inhibitors did not influence the GR50 of E. crus-galli to florpyrauxifen-benzyl. The expression of target receptor EcAFB4 was down-regulated in the R population, leading to the reduced response to florpyrauxifen-benzyl (suppresses over-production of ethylene and ABA). We verified this resistance mechanism in the knockout OsAFB4 in Oryza sativa L. The Osafb4 mutants exhibited high resistance to florpyrauxifen-benzyl and moderate resistance to quinclorac. Furthermore, DNA methylation in the EcAFB4 promoter regulated its low expression in the R population after florpyrauxifen-benzyl treatment. In summary, the low expression of the auxin receptor EcAFB4 confers target resistance to the synthetic auxin herbicide florpyrauxifen-benzyl in the R- E. crus-galli.

Brassinosteroids Confer Resistance to Isoproturon through OsBZR4-Mediated Degradation Genes in Rice (Oryza sativa L.).

Plants have complex detoxification and metabolic systems that enable them to deal with environmental pollutants. We report accumulation of the pesticide isoproturon (IPU) in a BR signaling pathway for mutant bzr4-3/5 rice to be significantly higher than in wild-type (WT) rice controls and for exogenous 24-epibrassinolide to reverse toxic symptoms in WT rice but not in mutants. A genome-wide RNA sequencing study of WT/bzr4 rice is performed to identify transcriptomic changes and metabolic mechanisms under IPU exposure. Three differentially expressed genes in yeast cells increase the degradation rate of IPU in a growth medium by factors of 1.61, 1.51, and 1.29 after 72 h. Using UPLC/Q-TOF-MS/MS, five phase I metabolites and five phase II conjugates are characterized in rice grains, with concentrations generally decreasing in bzr4 rice grains. OsBZR4, a regulator of IPU degradation in rice, may eliminate IPU from edible parts of food crops by regulating downstream metabolic genes.

Herbicidal Sorbicillinoid Analogs Cause Lignin Accumulation in Aspergillus aculeatus TE-65L.

Five new sorbicillinoid derivatives, including (±)-aspersorbicillin A [(±)-1], a pair of enantiomers at C-9, and aspersorbicillins B-D (2-4), together with two known analogs (5 and 6) were isolated from the endophytic fungus Aspergillus aculeatus TE-65L. Their structures including absolute configurations were determined by detailed spectroscopic analyses and electronic circular dichroism calculations. The herbicidal activity of sorbicillinoids on the germ and radicle elongation of various weed types was reported for the first time. Compound 1 displayed significant herbicidal activity against Eleusine indica germ elongation (IC50 = 28.8 µg/mL), while compound 6 inhibited radicle elongation (IC50 = 25.6 µg/mL). Both were stronger than those of glyphosate (66.2 and 30.9 µg/mL, respectively). Further transcriptomic and LC-MS/MS metabolomic analysis indicated that 6 induced the transcriptional expressions of genes related to the lignin biosynthetic pathway, resulting in lignin accumulation. Transmission electron microscopy confirmed the cell wall thickening of seeds treated with 6, suggesting weed growth inhibition. This study reveals new lead compounds for fabricating natural herbicides and expands the agricultural use of sorbicillinoid analogs.

3D structure of acetolactate synthase explains why the Asp-376-Glu point mutation does not give the same resistance level to different imidazolinone herbicides.

Resistance to ALS-inhibiting herbicides has dramatically increased worldwide due to the persisting evolution of target site mutations that reduce the affinity between the herbicide and the target. We evaluated the effect of the well-known ALS Asp-376-Glu target site mutation on different imidazolinone herbicides, including imazamox and imazethapyr. Greenhouse dose response experiments indicate that the Amaranthus retroflexus biotype carrying Asp-376-Glu was fully controlled by applying the field recommended dose of imazamox, whereas it displayed high level of resistance to imazethapyr. Likewise, Sorghum halepense, carrying Asp-376-Glu showed resistance to field recommended doses of imazethapyr but not of imazamox. Biochemical inhibition and kinetic characterization of the Asp-376-Glu mutant enzyme heterologously expressed using different plant sequence backbones, indicate that the Asp-376-Glu shows high level of insensitivity to imazethapyr but not to imazamox, corroborating the greenhouse results. Docking simulations revealed that imazamox can still inhibit the Asp-376-Glu mutant enzyme through a chalcogen interaction between the oxygen of the ligand and the sulfur atom of the ALS Met200, while imazethapyr does not create such interaction. These results explain the different sensitivity of the Asp-376-Glu mutation towards imidazolinone herbicides, thus providing novel information that can be exploited for defining stewardship guidelines to manage fields infested by weeds harboring the Asp-376-Glu mutation.

Validation of shikimate dehydrogenase as the herbicidal target of drupacine and screening of target-based compounds with high herbicidal activity.

The discovery of new targets and lead compounds is the key to developing new pesticides. The herbicidal target of drupacine has been identified as shikimate dehydrogenase (SkDH). However, the mechanism of interaction between them remains unclear. This study found that drupacine specifically binds to SkDH with a dissociation equilibrium constant (KD) of 8.88 µM and a Kd value of 2.15 µM, as confirmed by surface plasmon resonance and microscale thermophoresis. Site-directed mutagenesis coupled with fluorescence quenching analysis indicated that residue THR431 was the key amino acid site for drupacine binding to SkDH. Nine compounds with the best binding ability to SkDH were identified by virtual screening from about 120,000 compounds. Among them, compound 8 showed the highest inhibition rate with values of 41.95% against SkDH, also exhibiting the strongest herbicidal activity. This research identifies a novel potential target SkDH and a candidate lead compound with high herbicidal activity for developing new herbicides.

Diverse mechanisms confer bensulfuron-methyl resistance in Schoenoplectiella juncoides (Roxb.) lye.

The effectiveness of bensulfuron-methyl in controlling Schoenoplectiella juncoides (Roxb.) Lye has significantly decreased in rice fields in China. Hence, a bensulfuron-methyl-resistant S. juncoides population (W15) was collected from Dandong City, Liaoning Province, China, to investigate the underlying resistance mechanisms. Whole-plant dose-response experiments and ALS activity assay confirmed that W15 has evolved high-level resistance to bensulfuron-methyl compared with the susceptible S. juncoides population (W4). Molecular analysis revealed a Pro-197-Ser mutation in ALS1, while there was no significant difference in the relative ALS gene expression between W15 and W4. LC-MS/MS analysis showed W15 metabolized bensulfuron-methyl more rapidly than W4. Furthermore, bensulfuron-methyl resistance in W15 was significantly alleviated by malathion and 4-chloro-7-nitrobenzoxadiazole (NBD-Cl). Glutathione S-transferase activity was higher in W15 than in W4. Meanwhile, W15 displayed cross-resistance to halosulfuron-methyl and multi-resistance to MCPA-Na. In summary, these findings demonstrated for the first time that both target- and non-target-site resistance are relevant in the resistance of S. juncoides to bensulfuron-methyl.

Involvement of P450s in the metabolic resistance of Digitaria sanguinalis (L.) Scop. To ALS-inhibiting herbicides.

Weed resistance to a range of herbicides has rapidly evolved, often with different mechanisms of action. The resulting uninhibited growth of weeds poses demonstrable threats to crop production and sustainable agriculture. Digitaria sanguinalis (L.) Scop., a troublesome weed in corn and other agricultural fields, has developed resistance to herbicides that inhibiting ALS (Acetolactate Synthase), such as nicosulfuron. Understanding the weed's resistance patterns and mechanisms is crucial. However, little is known of the non-target site resistance (NTSR) mechanisms of D. sanguinalis owing to a lack of relevant genome sequences and other materials. Therefore, in this study, a population of D.sanguinalis presenting multiple resistance was tested and found that its high level of resistance to ALS-inhibiting herbicides was not associated with target-related alterations.Administration of P450 inhibitors reversed the resistance to ALS-inhibiting herbicides. Following the application of ALS-inhibiting herbicides, the activities of NADPH-P450 reductase and p-nitroanisole O-demethylase (PNOD) were notably greater in the resistant population of D. sanguinalis than those in the susceptible population. The results suggested P450 enzyme familyplays a major role in the metabolic resistance mechanism, that increased P450 enzyme activity promote cross-resistance in D. sanguinalis to ALS-inhibiting herbicides. RNA-seq analysis showed that five genes from the P450 family (CYP709B2, CYP714C2, CYP71A1, CYP76C2, and CYP81E8) were upregulated in resistant D. sanguinalis. In conclusion, the upregulation of several P450 genes is responsible for establishing resistance to ALS-inhibiting herbicides in D. sanguinalis.

Metabolic resistance mechanism to glufosinate in Eleusine indica.

Eleusine indica is one of the most troublesome weeds in farmland worldwide, especially in Citrus Orchard of China. Glufosinate, as an efficient non-selective broad-spectrum herbicide, has been widely utilized for the control of E. indica in Citrus Orchard. The E. indica resistant population (R) was collected from a Citrus Orchard in Yichang City in Hubei province, China. Bioassay experiments showed that the R plants exhibited 3-fold resistance to glufosinate compared with the E. indica susceptible population (S). No known glutamine synthetase (GS) gene mutation associated with glufosinate resistance was found in R plants. And there was also no significant difference in GS activity between R and S plants. Those results indicated that the resistance to glufosinate in R did not involve target-site resistance. However, glutathione S-transferase (GST) inhibitor 4-chloro-7-nitrobenzoxadiazole (NBD-Cl) plus glufosinate gave a better control of R plants compared with glufosinate treatment alone. Moreover, both before and after glufosinate treatment, the GST activity in R plants was significantly higher than that in S plants. By RNA-seq, the expression of GSTU6 and GST4 up-regulated in R plants relative to S plants with or without glufosinate treatment. They were also significantly up-regulated expression in E. indica field resistant populations compared with S population. In summary, the study elucidated that R plants developed metabolic resistance to glufosinate involving GST. And GSTU6 and GST4 genes may play an important role in this glufosinate metabolic resistance. The research results provide a theoretical basis for a deeper understanding of resistance mechanism to glufosinate in E. indica.

Characterisation of low-level pyrasulfotole resistance and the role of herbicide translocation in wild radish (Raphanus raphanistrum).

The synthetic auxin 2,4-D and the 4-hydroxyphenylpyruvate dioxygenase inhibitor pyrasulfotole are phloem-mobile post-emergence herbicides, the latter applied in co-formulation with either bromoxynil (a contact herbicide causing leaf desiccation) or MCPA (another synthetic auxin). Previous studies have shown a wide range of 2,4-D translocation phenotypes in resistant populations of the agricultural weed Raphanus raphanistrum, but it was hypothesised that enhanced movement out of the apical meristem could contribute to resistance. Little is known about pyrasulfotole translocation or the effect of bromoxynil on pyrasulfotole movement. Therefore, the behaviour of pyrasulfotole and 2,4-D applied to the growing point of susceptible and resistant R. raphanistrum seedlings was assessed, along with the effect of bromoxynil on pyrasulfotole translocation. The small amount of herbicide directly contacting the growing point after spraying was sufficient to induce herbicide symptoms, and there was no enhancement of translocation away from the growing point in either pyrasulfotole- or 2,4-D-resistant populations. Bromoxynil had a slightly inhibitory effect on pyrasulfotole translocation in some populations, somewhat negating the minor differences observed among populations when pyrasulfotole was applied alone. Resistance to pyrasulfotole could not explained by enhanced metabolism or vacuolar sequestration of the herbicide. Overall, differential translocation in either the treated leaves or apical meristems does not appear to be a major determinant of resistance to pyrasulfotole or 2,4-D.

Unravelling the role of proline in glyphosate-mediated toxicity - tolerance mechanism or stress signal?

Glyphosate (GLY), the most widely used herbicide, has been regarded as an emergent environmental contaminant due to its constant and cumulative use, with potential harm to non-target organisms, such as crops, disrupting cells' redox balance. Therefore, plants need to fine-tune their antioxidant (AOX) mechanisms to thrive under GLY-contaminated environments. Proline overaccumulation is a common response in plants exposed to GLY, yet its role in GLY-induced toxicity remains unclear. Thus, this study explores whether Pro overaccumulation in response to GLY is perceived as a downstream tolerance mechanism or an early-warning stress signal. To investigate this, Arabidopsis thaliana T-DNA mutant lines for Pro biosynthetic (P5CS1) and catabolic genes (ProDH) were used and screened for their GLY susceptibility. Upon seedlings' exposure to GLY (0.75 mg L-1) for 14 days, the herbicide led to reduced biomass in all genotypes, accompanied by Pro overaccumulation. Mutants with heightened Pro levels (prodh) exhibited the greatest biomass reduction, increased lipid peroxidation (LP), and hydrogen peroxide (H2O2) levels, accompanied by a compromised performance of the AOX system. Conversely, p5cs1-4, mutants with lower Pro levels, demonstrated an enhanced AOX system activation, not only with increased levels of glutathione (GSH) and ascorbate (AsA), but also with increased activity of both ascorbate peroxidase (APX) and catalase (CAT). These findings suggest that Pro overaccumulation under GLY exposure is associated with stress sensitivity rather than tolerance, highlighting its potential as an early-warning signal for GLY toxicity in non-target plants and for detecting weed resistance.

GO promotes detoxification of nicosulfuron in sweet corn by enhancing photosynthesis, chlorophyll fluorescence parameters, and antioxidant enzyme activity.

Although graphene oxide (GO) has extensive recognized application prospects in slow-release fertilizer, plant pest control, and plant growth regulation, the incorporation of GO into nano herbicides is still in its early stages of development. This study selected a pair of sweet corn sister lines, nicosulfuron (NIF)-resistant HK301 and NIF-sensitive HK320, and sprayed them both with 80 mg kg-1 of GO-NIF, with clean water as a control, to study the effect of GO-NIF on sweet corn seedling growth, photosynthesis, chlorophyll fluorescence, and antioxidant system enzyme activity. Compared to spraying water and GO alone, spraying GO-NIF was able to effectively reduce the toxic effect of NIF on sweet corn seedlings. Compared with NIF treatment, 10 days after of spraying GO-NIF, the net photosynthetic rate (A), stomatal conductance (Gs), transpiration rate (E), photosystem II photochemical maximum quantum yield (Fv/Fm), photochemical quenching coefficient (qP), and photosynthetic electron transfer rate (ETR) of GO-NIF treatment were significantly increased by 328.31%, 132.44%, 574.39%, 73.53%, 152.41%, and 140.72%, respectively, compared to HK320. Compared to the imbalance of redox reactions continuously induced by NIF in HK320, GO-NIF effectively alleviated the observed oxidative pressure. Furthermore, compared to NIF treatment alone, GO-NIF treatment effectively increased the activities of superoxide dismutase (SOD), guaiacol peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) in both lines, indicating GO induced resistance to the damage caused by NIF to sweet corn seedlings. This study will provides an empirical basis for understanding the detoxification promoting effect of GO in NIF and analyzing the mechanism of GO induced allogeneic detoxification in cells.

Natural Rubrolides and Their Synthetic Congeners as Inhibitors of the Photosynthetic Electron Transport Chain.

Rubrolides are a family of naturally occurring 5-benzylidenebutenolides, which generally contain brominated phenol groups, and nearly half of them also present a chlorine attached to the butenolide core. Seven natural rubrolides were previously synthesized. When these compounds were tested against the model plant Raphanus sativus, six were found to exert a slight inhibition on plant growth. Aiming to exploit their scaffold as a model for the synthesis of new compounds targeting photosynthesis, nine new rubrolide analogues were prepared. The synthesis was accomplished in 2-4 steps with a 10-39% overall yield from 3,4-dichlorofuran-2(5H)-one. All compounds were evaluated for their ability to inhibit the whole Hill reaction or excluding photosystem I (PSI). Several natural rubrolides and their analogues displayed good inhibitory potential (IC50 = 2-8 µM). Molecular docking studies on the photosystem II-light harvesting complex II (PSII-LHCII supercomplex) binding site were also performed. Overall, data support the use of rubrolides as a model for the development of new active principles targeting the photosynthetic electron transport chain to be used as herbicides.

Colchicine, Caffeine, Gramine, and Their Derivatives as Potential Herbicides, Fungicides, and Insecticides.

A preliminary in silico screening of 94 compounds, including colchicine, caffeine, gramine, and their derivatives, was conducted to identify potential herbicides, insecticides, and fungicides. Among the compounds tested, only gramine and its 13 derivatives exhibited potential activity. These compounds were further tested against eight species of insects, three species of weeds, and four species of fungi. All of the tested alkaloids were found to be ineffective as herbicides and insecticides, but they did exhibit some fungicidal activity. Four gramine derivatives showed some activity against Phytophthora infestans, Botrytis cinerea, Zymoseptoria tritici, and Fusarium culmorum.

Biocompatible Nano-Cocrystal Engineering for Targeted Herbicide Delivery: Enhancing Efficacy through Stimuli-Responsive Release and Reduced Environmental Losses.

In addressing the critical challenges posed by the misuse and inefficiency of traditional pesticides, we introduce a Nano-Cocrystal material composed of the herbicide clopyralid and coformer phenazine. Developed through synergistic supramolecular self-assembly and mechanochemical nanotechnology, this Nano-Cocrystal significantly enhances pesticide performance. It exhibits a marked improvement in stability, with reductions in hygroscopicity and volatility by approximately 38%. Moreover, it intelligently modulates release according to environmental factors, such as temperature, pH, and soil inorganic salts, demonstrating decreased solubility by up to four times and improved wettability and adhesion on leaf surfaces. Importantly, the herbicidal activity surpasses that of pure clopyralid, increasing suppression rates of Medicago sativa L. and Oxalis corniculata L. by up to 27% at the highest dosage. This Nano-Cocrystal also shows enhanced crop safety and reduced genotoxicity compared to conventional formulations. Offering a blend of simplicity, cost-effectiveness, and robust stability, our findings contribute a sustainable solution to agricultural practices, favoring the safety of nontarget organisms.

Synthesis of Novel Propionamide-Methylpyrazole Carboxylates as Herbicidal Candidates.

Transketolase (TKL; EC 2.2.1.1) is a highly promising potential target for herbicidal applications. To identify novel TKL inhibitors, we designed and synthesized a series of 3-oxopropionamide-1-methylpyrazole carboxylate analogues and assessed their herbicidal activities. Ethyl 3-((1-((2,4-dichlorophenyl)amino)-1-oxopropan-2-yl)oxy)-1-methyl-1H-pyrazole-5-carboxylate (D15) and ethyl 1-methyl-3-((1-oxo-1-((thiophen-2-ylmethyl)amino)propan-2-yl)oxy)-1H-pyrazole-5-carboxylate (D20) exhibited superior growth inhibition activities against both the root and stem of Amaranthus retroflexus (A. retroflexus) compared to nicosulfuron and mesotrione. Additionally, D15 achieved an inhibition rate of more than 90% against the roots and stems of Digitaria sanguinalis (D. sanguinalis), outperforming the four control agents at a concentration of 200 mg/L using the small cup method. In the pre-emergence herbicidal activity test, D15 effectively inhibited D. sanguinalis by more than 90% at 150 g ai/ha, surpassing the efficacy of the control, mesotrione. Conversely, in the postemergence herbicidal activity test, D20 exhibited efficient inhibition of A. retroflexus by more than 90% at 150 g ai/ha, outperforming the control agents nicosulfuron, mesotrione, and metamifop. The results of the TKL enzyme activity test showed that the IC50 values of compounds D15 and D20 were 0.384 and 0.655 mg/L, respectively, which were close to those of the control agents. Furthermore, molecular docking and molecular dynamics simulation studies revealed that D15 and D20 interacted favorably with the TKL of Setaria viridis. Such findings highlight the promising potential of D15 and D20 as lead TKL inhibitors for the optimization of new herbicides.

Metproxybicyclone, a Novel Carbocyclic Aryl-dione Acetyl-CoA Carboxylase-Inhibiting Herbicide for the Management of Sensitive and Resistant Grass Weeds.

Postemergence control of grass weeds has become problematic due to the evolution of resistance to 5-enolpyruvylshikimate-3-phosphate synthase, acetyl-CoA carboxylase (ACCase), and acetolactate synthase-inhibiting herbicides. Herein we describe the invention and synthesis journey toward metproxybicyclone, the first commercial carbocyclic aryl-dione ACCase-inhibiting herbicide for the cost-effective management of grass weeds in dicotyledonous crops and in preplant burndown applications. Glasshouse and field experiments have shown that metproxybicyclone is safe for use on soybean, cotton, and sugar beet, among other crops. It is effective on a variety of key grass weeds including Eleusine indica, Digitaria insularis, Sorghum halepense, and Echinochloa crus-galli. Importantly, metproxybicyclone was more efficacious at killing resistant grass weed populations than current ACCase herbicides. Metproxybicyclone controlled the main ACCase target-site and nontarget site resistant mechanisms in characterized Lolium multiflorum and E. indica populations under glasshouse conditions. Excellent control of a broad resistance-causing D2078G target-site mutant E. indica population was also observed under field conditions.

Study of Amino Acid-Derived 3-Acyltetramic Acids as Herbicidal Agents.

The growing problem of herbicide resistance necessitates the development of novel herbicidal active ingredients, together with other integrated weed management approaches. Natural products are a major source of inspiration for novel actives. In previous research, we identified a 3-acyltetramic acid of microbial origin that inhibited algal growth in marine biofilms, at least in part through inhibition of photosystem II. In this work, we demonstrate the herbicidal effect of this lead compound and construct multiple libraries to test the impact of the different substituents of the central scaffold in order to study the structure-activity relationships. Among these analogues, the highest activities were found for medium- to long-chain acyl groups and apolar secondary amino acid residues. Finally, we provide first insights into the herbicidal mechanisms and present preliminary field-trial and ecotoxicological results for TA12-Pro, the most active analogue in our library. Together, this research shows the potential of 3-acyltetramic acids for herbicide development.