MYT1L haploinsufficiency in human neurons and mice causes autism-associated phenotypes that can be reversed by genetic and pharmacologic intervention.

MYT1L is an autism spectrum disorder (ASD)-associated transcription factor that is expressed in virtually all neurons throughout life. How MYT1L mutations cause neurological phenotypes and whether they can be targeted remains enigmatic. Here, we examine the effects of MYT1L deficiency in human neurons and mice. Mutant mice exhibit neurodevelopmental delays with thinner cortices, behavioural phenotypes, and gene expression changes that resemble those of ASD patients. MYT1L target genes, including WNT and NOTCH, are activated upon MYT1L depletion and their chemical inhibition can rescue delayed neurogenesis in vitro. MYT1L deficiency also causes upregulation of the main cardiac sodium channel, SCN5A, and neuronal hyperactivity, which could be restored by shRNA-mediated knockdown of SCN5A or MYT1L overexpression in postmitotic neurons. Acute application of the sodium channel blocker, lamotrigine, also rescued electrophysiological defects in vitro and behaviour phenotypes in vivo. Hence, MYT1L mutation causes both developmental and postmitotic neurological defects. However, acute intervention can normalise resulting electrophysiological and behavioural phenotypes in adulthood.

[A preliminary pharmacophylogenetic study of Solanaceae medicinal plants containing tropane alkaloids].

The Solanaceae plants distributed in China belong to 105 species and 35 varietas of 24 genera. Some medicinal plants of Solanaceae are rich in tropane alkaloids(TAs), which have significant pharmacological activities. In this paper, the geographical distribution, chemical components, traditional therapeutic effect, pharmacological activities, and biosynthetic pathways of TAs in Solanaceous plants were summarized. Besides, the phylogeny of medicinal plants belonging to Solanaceae was visualized by network diagram. Fourteen genera of Solanaceae plants in China contain TAs and have medical records. TAs mainly exist in Datura, Anisodus, Atropa, Physochlaina, and Hyoscyamus. The TAs-containing species were mainly concentrated in Southwest China, and the content of TAs was closely related to plant distribution area and altitude. The Solanaceae plants containing TAs mainly have antispasmodic, analgesic, antiasthmatic, and antitussive effects. Modern pharmacological studies have proved the central sedative, pupil dilating, glandular secretion-inhibiting, and anti-asthma activities of TAs. These pharmacological activities provide a reasonable explanation for the traditional therapeutic efficacy of tropane drugs. In this paper, the geographical distribution, chemical components, traditional therapeutic effect, and modern pharmacological activities of TAs-containing species in Solanaceae were analyzed for the first time. Based on these data, the genetic relationship of TAs-containing Solanaceae species was preliminarily discussed, which provided a scientific basis for the basic research on TAs-containing solanaceous species and was of great significance for the development of natural medicinal plant resources containing TAs.

Enhanced Na+ -K+ -2Cl- cotransporter 1 underlies motor dysfunction in huntington's disease.

BACKGROUND: Altered γ-aminobutyric acid signaling is believed to disrupt the excitation/inhibition balance in the striatum, which may account for the motor symptoms of Huntington's disease. Na-K-2Cl cotransporter-1 is a key molecule that controls γ-aminobutyric acid-ergic signaling. However, the role of Na-K-2Cl cotransporter-1 and efficacy of γ-aminobutyric acid-ergic transmission remain unknown in Huntington's disease. METHODS: We determined the levels of Na-K-2Cl cotransporter-1 in brain tissue from Huntington's disease mice and patients by real-time quantitative polymerase chain reaction, western blot, and immunocytochemistry. Gramicidin-perforated patch-clamp recordings were used to measure the Eγ-aminobutyric acid in striatal brain slices. To inhibit Na-K-2Cl cotransporter-1 activity, R6/2 mice were treated with an intraperitoneal injection of bumetanide or adeno-associated virus-mediated delivery of Na-K-2Cl cotransporter-1 short-hairpin RNA into the striatum. Motor behavior assays were employed. RESULTS: Expression of Na-K-2Cl cotransporter-1 was elevated in the striatum of R6/2 and Hdh150Q/7Q mouse models. An increase in Na-K-2Cl cotransporter-1 transcripts was also found in the caudate nucleus of Huntington's disease patients. Accordingly, a depolarizing shift of Eγ-aminobutyric acid was detected in the striatum of R6/2 mice. Expression of the mutant huntingtin in astrocytes and neuroinflammation were necessary for enhanced expression of Na-K-2Cl cotransporter-1 in HD mice. Notably, pharmacological or genetic inhibition of Na-K-2Cl cotransporter-1 rescued the motor deficits of R6/2 mice. CONCLUSIONS: Our findings demonstrate that aberrant γ-aminobutyric acid-ergic signaling and enhanced Na-K-2Cl cotransporter-1 contribute to the pathogenesis of Huntington's disease and identify a new therapeutic target for the potential rescue of motor dysfunction in patients with Huntington's disease. © 2019 International Parkinson and Movement Disorder Society.

Revisiting the Lamotrigine-Mediated Effect on Hippocampal GABAergic Transmission.

Lamotrigine (LTG) is generally considered as a voltage-gated sodium (Nav) channel blocker. However, recent studies suggest that LTG can also serve as a hyperpolarization-activated cyclic nucleotide-gated (HCN) channel enhancer and can increase the excitability of GABAergic interneurons (INs). Perisomatic inhibitory INs, predominantly fast-spiking basket cells (BCs), powerfully inhibit granule cells (GCs) in the hippocampal dentate gyrus. Notably, BCs express abundant Nav channels and HCN channels, both of which are able to support sustained action potential generation. Using whole-cell recording in rat hippocampal slices, we investigated the net LTG effect on BC output. We showed that bath application of LTG significantly decreased the amplitude of evoked compound inhibitory postsynaptic currents (IPSCs) in GCs. In contrast, simultaneous paired recordings from BCs to GCs showed that LTG had no effect on both the amplitude and the paired-pulse ratio of the unitary IPSCs, suggesting that LTG did not affect GABA release, though it suppressed cell excitability. In line with this, LTG decreased spontaneous IPSC (sIPSC) frequency, but not miniature IPSC frequency. When re-examining the LTG effect on GABAergic transmission in the cornus ammonis region 1 (CA1) area, we found that LTG markedly inhibits both the excitability of dendrite-targeting INs in the stratum oriens and the concurrent sIPSCs recorded on their targeting pyramidal cells (PCs) without significant hyperpolarization-activated current (Ih) enhancement. In summary, LTG has no effect on augmenting Ih in GABAergic INs and does not promote GABAergic inhibitory output. The antiepileptic effect of LTG is likely through Nav channel inhibition and the suppression of global neuronal network activity.

Rapid dynamic changes of dendritic inhibition in the dentate gyrus by presynaptic activity patterns.

The dentate gyrus (DG) serves as a primary gate to control information transfer from the cortex to the hippocampus. Activation of incoming cortical inputs results in rapid synaptic excitation followed by slow GABA-mediated (GABAergic) synaptic inhibition onto DG granule cells (GCs). GABAergic inhibitory interneurons (INs) in the DG comprise fast-spiking (FS) and non-fast-spiking (non-FS) cells. Anatomical analyses of DG INs reveal that FS cells are soma-targeting INs, whereas non-FS cells are dendrite-targeting INs. These two IN classes are differentially recruited by excitatory inputs and in turn provide exquisite spatiotemporal control over GC activity. Yet, little is known how FS and non-FS cells transform their presynaptic dynamics into varying postsynaptic response amplitudes. Using paired recordings in rat hippocampal slices, we show that inhibition in the DG is dominated by somatic GABAergic inputs during periods of sparse presynaptic activity, whereas dendritic GABAergic inputs are rapidly shifted to powerful and sustained inhibition during periods of intense presynaptic activity. The variant dynamics of dendritic inhibition is dependent on presynaptic IN subtypes and their activity patterns and is attributed to Ca(2+)-dependent increases in the probability of release and the size of the readily releasable pool. Furthermore, the degree of dynamic GABA release can be reduced by blocking voltage-gated K(+) channels, which increases the efficacy of dendrite-targeting IN output synapses during sparse firing. Such rapid dynamic modulation of dendritic inhibition may act as a frequency-dependent filter to prevent overexcitation of GC dendrites and thus set the excitatory-inhibitory synaptic balance in the DG circuits.

Long-range inhibition from prelimbic to cingulate areas of the medial prefrontal cortex enhances network activity and response execution.

It is well established that the medial prefrontal cortex (mPFC) exerts top-down control of many behaviors, but little is known regarding how cross-talk between distinct areas of the mPFC influences top-down signaling. We performed virus-mediated tracing and functional studies in male mice, homing in on GABAergic projections whose axons are located mainly in layer 1 and that connect two areas of the mPFC, namely the prelimbic area (PrL) with the cingulate area 1 and 2 (Cg1/2). We revealed the identity of the targeted neurons that comprise two distinct types of layer 1 GABAergic interneurons, namely single-bouquet cells (SBCs) and neurogliaform cells (NGFs), and propose that this connectivity links GABAergic projection neurons with cortical canonical circuits. In vitro electrophysiological and in vivo calcium imaging studies support the notion that the GABAergic projection neurons from the PrL to the Cg1/2 exert a crucial role in regulating the activity in the target area by disinhibiting layer 5 output neurons. Finally, we demonstrated that recruitment of these projections affects impulsivity and mechanical responsiveness, behaviors which are known to be modulated by Cg1/2 activity.

GABA is depolarizing in hippocampal dentate granule cells of the adolescent and adult rats.

GABAergic signaling in hippocampal pyramidal neurons undergoes a switch from depolarizing to hyperpolarizing during early neuronal development. Whether such a transformation of GABAergic action occurs in dentate granule cells (DGCs), located at the first stage of the hippocampal trisynaptic circuit, is unclear. Here, we use noninvasive extracellular recording to monitor the effect of synaptically released GABA on the DGC population. We find that GABAergic responses in adolescent and adult rat DGCs are still depolarizing from rest. Using a morphologically realistic DGC model, we show that GABAergic action, depending on its precise timing and location, can have either an excitatory or inhibitory role in signal processing in the dentate gyrus.

Mutations in KCND3 cause spinocerebellar ataxia type 22.

OBJECTIVE: To identify the causative gene in spinocerebellar ataxia (SCA) 22, an autosomal dominant cerebellar ataxia mapped to chromosome 1p21-q23. METHODS: We previously characterized a large Chinese family with progressive ataxia designated SCA22, which overlaps with the locus of SCA19. The disease locus in a French family and an Ashkenazi Jewish American family was also mapped to this region. Members from all 3 families were enrolled. Whole exome sequencing was performed to identify candidate mutations, which were narrowed by linkage analysis and confirmed by Sanger sequencing and cosegregation analyses. Mutational analyses were also performed in 105 Chinese and 55 Japanese families with cerebellar ataxia. Mutant gene products were examined in a heterologous expression system to address the changes in protein localization and electrophysiological functions. RESULTS: We identified heterozygous mutations in the voltage-gated potassium channel Kv4.3-encoding gene KCND3: an in-frame 3-nucleotide deletion c.679_681delTTC p.F227del in both the Chinese and French pedigrees, and a missense mutation c.1034G>T p.G345V in the Ashkenazi Jewish family. Direct sequencing of KCND3 further identified 3 mutations, c.1034G>T p.G345V, c.1013T>C p.V338E, and c.1130C>T p.T377M, in 3 Japanese kindreds. Immunofluorescence analyses revealed that the mutant p.F227del Kv4.3 subunits were retained in the cytoplasm, consistent with the lack of A-type K(+) channel conductance in whole cell patch-clamp recordings. INTERPRETATION: Our data identify the cause of SCA19/22 in patients of diverse ethnic origins as mutations in KCND3. These findings further emphasize the important role of ion channels as key regulators of neuronal excitability in the pathogenesis of cerebellar degeneration.

Medial entorhinal cortex commissural input regulates the activity of spatially and object-tuned cells contributing to episodic memory.

Extensive interhemispheric projections connect many homotopic brain regions, including the hippocampal formation, but little is known as to how information transfer affects the functions supported by the target area. Here, we studied whether the commissural projections connecting the medial entorhinal cortices contribute to spatial coding, object coding, and memory. We demonstrate that input from the contralateral medial entorhinal cortex targets all major cell types in the superficial medial entorhinal cortex, modulating their firing rate. Notably, a fraction of responsive cells displayed object tuning and exhibited a reduction in their firing rate upon the inhibition of commissural input. In line with this finding are behavioral results that revealed the contribution of commissural input to episodic-like memory retrieval.

Dianthi herba: a comprehensive review of its botany, traditional use, phytochemistry, and pharmacology.

Dianthi herba (called "Qumai" in Chinese) is the dried aerial part of Dianthus superbus L. and Dianthus chinensis L. The species are mainly distributed in the temperate and warm temperate regions in the northern hemisphere, and some regions in Africa and Oceania, as well as South America. However, the distribution pattern of Dianthi herba has not been reviewed. In this review, we summarize the research progress on the botany, traditional use, phytochemistry, pharmacology, toxicology, and clinical applications of Dianthi herba. Approximately 194 chemical compounds have been identified and isolated from Dianthi herba, the most important being triterpenoid saponins, flavonoids, and volatile oil compounds. These compounds possess antiviral, anticancer, antioxidant, and antimicrobial properties, inter alia. Further studies should be carried out on Dianthi herba to elucidate more of its active principles and their mechanisms of action.

Diazepam binding inhibitor governs neurogenesis of excitatory and inhibitory neurons during embryonic development via GABA signaling.

Of the neurotransmitters that influence neurogenesis, gamma-aminobutyric acid (GABA) plays an outstanding role, and GABA receptors support non-synaptic signaling in progenitors and migrating neurons. Here, we report that expression levels of diazepam binding inhibitor (DBI), an endozepine that modulates GABA signaling, regulate embryonic neurogenesis, affecting the long-term outcome regarding the number of neurons in the postnatal mouse brain. We demonstrate that DBI is highly expressed in radial glia and intermediate progenitor cells in the germinal zones of the embryonic mouse brain that give rise to excitatory and inhibitory cells. The mechanism by which DBI controls neurogenesis involves its action as a negative allosteric modulator of GABA-induced currents on progenitor cells that express GABAA receptors containing γ2 subunits. DBI's modulatory effect parallels that of GABAA-receptor-mediating signaling in these cells in the proliferative areas, reflecting the tight control that DBI exerts on embryonic neurogenesis.

Synthesis of Dialkyl-Substituted Monofluoroalkenes via Palladium-Catalyzed Cross-Coupling of Alkyl Carbagermatranes.

An unprecedented cross-coupling reaction of alkyl carbagermatranes with bromofluoroolefins to deliver dialkyl-substituted monofluoroalkenes was achieved. This cross-coupling reaction was performed under base/additive-free conditions with excellent functional group tolerance, therefore offering an opportunity for challenging dialkyl-substituted monofluoroalkenes. The preparation of bioactive agent analogues including an antitubercular agent mimic and a COX-2 inhibitor analogue and the late-stage fluoroalkenylation of drug-molecule derivatives proved the utility of this strategy.

Syntheses and herbicidal activity of new triazolopyrimidine-2-sulfonamides as acetohydroxyacid synthase inhibitor.

The triazolopyrimidine-2-sulfonanilide, discovered from preparing bioisosteres of the sulfonylurea herbicides, is an important class of acetohydroxyacid synthase (AHAS, EC 4.1.3.18) inhibitors. At least over ten triazolopyrimidine sulfonanilides have been commercialized as herbicides for the control of broadleaf weeds and grass with cereal crop selectivity. Herein, a series of triazolopyrimidine-2-sulfonanilides were designed and synthesized with the aim of discovery of new herbicides with higher activity. The assay results of the inhibition activity of the synthesized compounds against Arabidopsis thatiana AHAS indicated that some compounds showed a little higher activity against flumetsulam (FS), the first commercial triazolopyrimidine-2-sulfonanilide-type herbicide. The ki values of two promising compounds 3d and 8h are respectively, 1.61 and 1.29 microM, while that of FS is 1.85 microM. Computational simulation results indicated the ester group of compound 3d formed hydrogen bonds with the surrounding residues Arg'198 and Ser653, which accounts for its 11.5-folds higher AHAS inhibition activity than Y6610. Further green house assay showed that compound 3d has comparable herbicidal activity as FS. Even at the concentration of 37.5g.ai/ha, 3d showed excellent herbicidal activity against Galium aparine, Cerastium arvense, Chenopodium album, Amaranthus retroflexus, and Rmumex acetasa, moderate herbicidal activity against Polygonum humifusum, Cyperus iria, and Eclipta prostrate. The combination of in vitro and in vivo assay indicated that 3d could be regarded as a new potential acetohydroxyacid synthase-inhibiting herbicide candidate for further study.

Gene Expression, Network Analysis, and Drug Discovery of Neurofibromatosis Type 2-Associated Vestibular Schwannomas Based on Bioinformatics Analysis.

Neurofibromatosis Type 2- (NF2-) associated vestibular schwannomas (VSs) are histologically benign tumors. This study aimed to determine disease-related genes, pathways, and potential therapeutic drugs associated with NF2-VSs using the bioinformatics method. Microarray data of GSE108524 were downloaded from the Gene Expression Omnibus (GEO) database, and differentially expressed genes (DEGs) were screened using GEO2R. The functional enrichment and pathway enrichment of DEGs were performed using Gene Ontology (GO) and Kyoto Encyclopedia of Genes Genomes (KEGG). Furthermore, the STRING and Cytoscape were used to analyze the protein-protein interaction (PPI) network of all differentially expressed genes and identify hub genes. Finally, the enriched gene sets belonging to the identified pathways were queried against the Drug-Gene Interaction database to find drug candidates for topical use in NF2-associated VSs. A total of 542 DEGs were identified, including 13 upregulated and 329 downregulated genes, which were mainly enriched in terms of focal adhesion, PI3K-Akt signaling pathway, ECM-receptor interaction, Toll-like receptor signaling pathway, Rap1 signaling pathway, and regulation of actin cytoskeleton. 28 hub genes were identified based on the subset of PPI network, and 31 drugs were selected based on the Drug-Gene Interaction database. Drug discovery using bioinformatics methods facilitates the identification of existing or potential therapeutic drugs to improve NF2 treatment.

Efficacy of Modified Qufeng Runmian Powder () on Acne Vulgaris with Syndromes of Dampness and Blood Stasis: A Multicenter, Randomized, Double-Blind, Placebo-Controlled Clinical Trial.

OBJECTIVE: To evaluate the efficacy and safety of a Chinese medicine (CM) Modified Qufeng Runmian Powder (, MQFRMP) for the treatment of acne vulgaris with CM syndromes of dampness and blood stasis. METHODS: In this multicenter, randomized, double-blind, placebo-controlled clinical trial, 220 acne vulgaris patients with CM syndrome of dampness and blood stasis were included and randomly assigned using a central area group random design to receive either MQFRMP or the placebo, with 110 cases in each group. MQFRMP or a placebo at 145 g/bag were administered once daily for 4 weeks, respectively. The primary index of efficacy was the effective rate according to the acne severity score (ASS). The secondary indices of efficacy included the changes in the dermatology life quality index (DLQI) score, VISIA scores (spots, pores, brown spots, porphyrins and red areas) and skin assessment (skin pH, sebum amount and hydration) according to a SOFT skin multianalyzer. RESULTS: (1) Follow-up: a total of 204 patients completed the follow-up, with 103 in the treatment group and 101 in the control group. (2) Effective rate: the total effective rate of the treatment group was significantly higher than the control group [83.5% (86/103) vs. 31.7% (32/101), P<0.01)] with 95% confidence interval of 39.3%-66.4%. (3) DLQI: DLQI scores were significantly decreased the treatment and control groups (both P<0.01), but the treatment group was more obvious than the placebo group (P<0.01). (4) VISIA scores: the scores of spots, brown spots and red areas in the treatment group decreased compared with baseline (P<0.05). In the control group, the scores of brown spots and pores decreased compared with baseline (P<0.05). The improvement was more obvious in the treatment group than in the control group for all items (P<0.05). (5) Skin assessment: the pH and sebum score in the both groups decreased drastically compared with the baseline (all P<0.01), however, the improvement was more obvious in the treatment group than in the control group (P<0.01). The hydration amount in the two groups showed no statistically significant difference compared with the baseline (both P>0.05). (6) Safety: two cases of mild drug allergy were observed in the treatment group. CONCLUSION: MQFRMP was effective and safe for the treatment of acne vulgaris with syndromes of dampness and blood stasis. (No. ChiCTR1900020479).

Relationship between alcohol use, blood pressure and hypertension: an association study and a Mendelian randomisation study.

BACKGROUND: Past studies have found a strong relationship between alcohol drinking and human health. METHODS: In this study, we first tested the association of rs671 with alcohol use in 2349 participants in southeast China. We then evaluated the causal impact between alcohol use and cardiovascular traits through a Mendelian randomisation (MR) analysis. RESULTS: We found strong evidence for the association of rs671 in the ALDH2 gene with alcohol drinking (p=6.08×10-47; ORadj G=4.50, 95% CI 3.67 to 5.52). We found that female G carriers of rs671 had a higher proportion of non-drinkers than male G carriers (88.01% vs 38.70%). In non-drinkers, the female G allele frequency was higher than the male G allele frequency (71.1% vs 55.2%). MR analysis suggested that alcohol use had a causal effect on blood pressure (increasing 9.46 mm Hg for systolic blood pressure (p=9.67×10-4) and 7.50 mm Hg for diastolic blood pressure (p=9.62×10-5)), and on hypertension in men (p=0.011; OR =1.19, 95% CI 1.04 to 1.36) and in pooled samples (p=0.013; OR =1.20, 95% CI 1.04 to 1.39), but not in women. We did not observe a causal effect of alcohol use on body mass index and lipid levels; further studies are needed to clarify the non-causal relationship. CONCLUSIONS: Compared to never-drinkers, current and previous alcohol use had a causal effect on blood pressure and hypertension in pooled samples and in men. These results reflect Chinese culture which does not encourage women to drink.

Design, Synthesis, and Herbicidal Activity of Pyrimidine-Biphenyl Hybrids as Novel Acetohydroxyacid Synthase Inhibitors.

The issue of weed resistance to acetohydroxyacid synthase (EC 2.2.1.6, AHAS) inhibitors has become one of the largest obstacles for the application of this class of herbicides. In a continuing effort to discover novel AHAS inhibitors to overcome weed resistance, a series of pyrimidine-biphenyl hybrids (4aa-bb and 5aa-ah) were designed and synthesized via a scaffold hopping strategy. Among these derivatives, compounds 4aa ( Ki = 0.09 µM) and 4bb ( Ki = 0.02 µM) displayed higher inhibitory activities against Arabidopsis thaliana AHAS than those of the controls bispyribac ( Ki = 0.54 µM) and flumetsulam ( Ki = 0.38 µM). Remarkably, compounds 4aa, 4bb, 5ah, and 5ag exhibited excellent postemergence herbicidal activity and a broad spectrum of weed control at application rates of 37.5-150 g of active ingredient (ai)/ha. Furthermore, 4aa and 4bb showed higher herbicidal activity against AHAS inhibitor-resistant Descurainia sophia, Ammannia arenaria, and the corresponding sensitive weeds than that of bispyribac at 0.94-0.235 g ai/ha. Therefore, the pyrimidine-biphenyl motif and lead compounds 4aa and 4bb have great potential for the discovery of novel AHAS inhibitors to combat AHAS-inhibiting herbicide-resistant weeds.

Computational design of novel inhibitors to overcome weed resistance associated with acetohydroxyacid synthase (AHAS) P197L mutant.

BACKGOUND: Acetohydroxyacid synthase (AHAS; EC 2.2.1.6) is the first common enzyme in the biosynthetic pathway leading to the branched-chain amino acids in plants and a wide range of microorganisms. With the long-term and wide application of AHAS inhibitors, weed resistance is becoming a global problem, which leads to an urgent demand for novel inhibitors to antagonize both wild-type and resistant AHAS. RESULTS: Pyrimidinyl salicylic acid derivatives, as one of the main classes of commercial AHAS herbicides, show potential anti-resistant bioactivity to wild-type and P197L mutant. In current work, a series of novel 2-benzoyloxy-6-pyrimidinyl salicylic acid derivatives were designed through fragment-based drug discovery. Fortunately, the newly synthesized compounds showed good inhibitory activity against both wild-type and P197L mutant. Some compounds not only had a lower resistance factor value but also showed excellent inhibitory activity against wild-type AHAS and P197L mutant. Furthermore, greenhouse experiments showed compound 11m displayed almost 100% inhibition against both wild-type and high-resistant Descurainia sophia at a dosage of 150 g a.i. ha-1 . CONCLUSION: The present work indicated that the 2-benzoyloxy-6-pyrimidinyl salicylic acid motif was well worth further optimization. Also, compound 11m could be used as a potential anti-resistant AHAS herbicide, which requires further research. © 2016 Society of Chemical Industry.

Discovery of New 2-[(4,6-Dimethoxy-1,3,5-triazin-2-yl)oxy]-6-(substituted phenoxy)benzoic Acids as Flexible Inhibitors of Arabidopsis thaliana Acetohydroxyacid Synthase and Its P197L Mutant.

In the search for new antiresistance acetohydroxyacid synthase (AHAS, EC 2.2.1.6) inhibitors to combat weed resistance associated with AHAS mutations, a series of 2-[(4,6-dimethoxy-1,3,5-triazin-2-yl)oxy]-6-(substituted phenoxy)benzoic acids 11-38 were designed and synthesized via the strategy of conformational flexibility analysis. Compounds 21, 22, 26, 33, 36, and 38 with high potency against both wild-type AtAHAS and its P197L mutant were identified as promising candidates with low resistance factors (RF, defined as the ratio between the ki values toward P197L mutant and wild-type AHAS) ranging from 0.73 to 6.32. Especially, compound 22 (RF = 0.73) was further identified as the most potent antiresistance AHAS inhibitor because of its significantly reduced resistance level compared with that of tribenuron-methyl (RF = 2650) and bispyribac (RF = 4.57). Furthermore, compounds 26, 33, 36, and 38 also displayed promising herbicidal activities against sensitive and resistant (P197L) Descurainia sophia at the dosage of 75-150 g of active ingredient (ai)/ha. Notably, compounds 33 and 38 still maintained over 60% herbicidal activity toward the resistant weed even at much lower dosages (37.5 g ai/ha). Therefore, the designed scaffold has the great potential to discover new candidate compounds for the control of weed resistance associated with AHAS mutation.

Triazolopyrimidines as a New Herbicidal Lead for Combating Weed Resistance Associated with Acetohydroxyacid Synthase Mutation.

Acetohydroxyacid synthase (AHAS; also known as acetolactate synthase; EC 2.2.1.6, formerly EC 4.1.3.18) is the first common enzyme in the biosynthetic pathway leading to the branched-chain amino acids in plants and a wide range of microorganisms. Weed resistance to AHAS-inhibiting herbicides, increasing at an exponential rate, is becoming a global problem and leading to an urgent demand of developing novel compounds against both resistant and wild AHAS. In the present work, a series of novel 2-aroxyl-1,2,4-triazolopyrimidine derivatives (a total of 55) were designed and synthesized with the aim to discover an antiresistant lead compound. Fortunately, the screening results indicated that many of the newly synthesized compounds showed a better, even excellent, inhibition effect against both the wild-type Arabidopsis thaliana AHAS and P197L mutants. Among them, compounds 5-3 to 5-17, compounds 5-19 to 5-26, compounds 5-28 to 5-45, and compound 5-48 have the lower values of resistance factor (RF) and display a potential power to overcome resistance associated with the P197L mutation in the enzyme levels. Further greenhouse in vivo assay showed that compounds 5-15 and 5-20 displayed "moderate" to "good" herbicidal activity against both the wild type-and the resistant (P197L mutation) Descurainia sophia, even at a rate as low as 0.9375 (g of ai/ha). The above results indicated that these two compounds could be used as new leads for the future development of antiresistance herbicides.