Repairing Host Damage Caused by Tobacco Mosaic Virus Stress: Design, Synthesis, and Mechanism Study of Novel Oxadiazole and Arylhydrazone Derivatives.

Tobacco mosaic virus (TMV), as one of the most traditional and extensive biological stresses, poses a serious threat to plant growth and development. In this work, a series of 1-phenyl/tertbutyl-5-amino-4-pyrazole oxadiazole and arylhydrazone derivatives was synthesized. Bioassay evaluation demonstrated that the title compounds (P1-P18) without a "thioether bond" lost their anti-TMV activity, while some of the ring-opening arylhydrazone compounds exhibited superior in vivo activity against TMV in tobacco. The EC50 value of title compound T8 for curative activity was 139 µg/mL, similar to that of ningnanmycin (NNM) (EC50 = 152 µg/mL). Safety analysis revealed that compound T8 had no adverse effects on plant growth or seed germination at a concentration of 250 µg/mL. Morphological observation revealed that compound T8 could restore the leaf tissue of a TMV-stressed host and the leaf stomatal aperture to normal. A mechanism study further revealed that compound T8 not only restored the photosynthetic and growth ability of the damaged host to normal levels but also enhanced catalase (CAT) activity and reduced the content of malondialdehyde (MDA) and hydrogen peroxide (H2O2) in the damaged host, thereby reducing the oxidation damage to the host. TMV-green fluorescent protein (GFP) experiments further demonstrated that compound T8 not only slowed the transmission speed of TMV in the host but also inhibited its reproduction. All of the experimental results demonstrated that compound T8 could reduce the oxidative damage caused by TMV stress and regulate the photosynthetic ability of the host, achieving the ability to repair damage, to make the plant grow normally.

Design, Synthesis, and Antifungal Activity of Acrylamide Derivatives Containing Trifluoromethylpyridine and Piperazine.

In this study, a series of acrylamide derivatives containing trifluoromethylpyridine or piperazine fragments were rationally designed and synthesized. Subsequently, the in vitro antifungal activities of all of the synthesized compounds were evaluated. The findings revealed that compounds 6b, 6c, and 7e exhibited >80% antifungal activity against Phomopsis sp. (Ps) at the concentration of 50 µg/mL. Furthermore, the EC50 values for compounds 6b, 6c, and 7e against Ps were determined to be 4.49, 6.47, and 8.68 µg/mL, respectively, which were better than the positive control with azoxystrobin (24.83 µg/mL). At the concentration of 200 µg/mL, the protective activity of compound 6b against Ps reached 65%, which was comparable to that of azoxystrobin (60.9%). Comprehensive mechanistic studies, including morphological studies with fluorescence microscopy (FM), cytoplasmic leakage, and enzyme activity assays, indicated that compound 6b disrupts cell membrane integrity and induces the accumulation of defense enzyme activity, thereby inhibiting mycelial growth. Therefore, compound 6b serves as a valuable candidate for the development of novel fungicides for plant protection.

Design and Synthesis of Mandelic Acid Derivatives for Suppression of Virulence via T3SS against Citrus Canker.

Citrus canker, a highly contagious bacterial disease caused by Xanthomonas citri subsp. citri (Xcc), poses a substantial threat to citrus crops, leading to serious reductions in fruit yield and economic losses. Most commonly used bactericides against Xcc lead to the rapid development of resistant subpopulations. Therefore, it is imperative to create novel drugs, such as type III secretion system (T3SS) inhibitors, that specifically target bacterial virulence factors rather than bacterial viability. In our study, we designed and synthesized a series of mandelic acid derivatives including 2-mercapto-1,3,4-thiazole. Seven substances were found to reduce the level of transcription of hpa1 without affecting bacterial viability. In vivo bioassays indicated that compound F9 significantly inhibited hypersensitive response and pathogenicity. RT-qPCR assays showed that compound F9 visibly suppressed the expression of Xcc T3SS-related genes as well as citrus canker susceptibility gene CsLOB1. Furthermore, the combination with compound F9 and quorum-quenching bacteria HN-8 can also obviously alleviate canker symptoms.

Application of thifluzamide to stem rot in peppers: Infection and control mechanisms of sclerotium rolfsii.

In recent years, the fungal disease 'pepper stem rot', contracted from the soil-borne pathogen sclerotium rolfsii, has been increasing year by year, causing significant losses to the pepper (Capsicum annuum L.) industry. To investigate the infection mechanism of stem rot, the fungus S. rolfsii was used to infect the roots of pepper plants, and was found to affect root morphology and reduce root activity, which subsequently inhibited root growth and development. With fungal infestation, its secretions (oxalic acid, PG and PMG enzyme) were able to break normal tissues in the stem base and induced the burst of the active oxygen, which leads to injury aggravation. Morphological observations of the site of damage at the base of the stem using SEM revealed that the vascular bundles and stomata were completely blocked by hyphae, resulting in a blockade of material exchange in the plant. It was subsequently found that most of the stomata in the leaves were closed, which caused the leaves to lose their ability to photosynthesize, then turned yellow, wilt, shed, and the plant died. Commercialized fungicide thifluzamide with excellent in vitro (EC50 = 0.1 µg/mL) and in vivo curative (EC50 = 29.2 µg/mL) antifungal activity was selected to control the stem rot disease in peppers. The results demonstrated that it was able to suppress the secretion of associated pathogenic factors and reduce the outbursts of reactive oxygen species, thus reducing the damage caused by S. rolfsii at the base of the plant's stem and also enhancing the root activity of the infected plant, thereby promoting root growth. It could also inhibit fungal growth, unblock the vascular bundles and stomata, maintain a balance of material and energy exchange within the plant, and thus restore the damaged plant to its normal growth capacity. All the results will provide an adequate reference for the prevention and control of stem rot disease on peppers with thifluzamide.

Microwave hyperthermia enhances radiosensitization by decreasing DNA repair efficiency and inducing oxidative stress in PC3 prostatic adenocarcinoma cells.

PURPOSE: Radiotherapy (RT) is the primary treatment for prostate cancer (PCa); however, the emergence of castration-resistant prostate cancer (CRPC) often leads to treatment failure and cancer-related deaths. In this study, we aimed to explore the use of microwave hyperthermia (MW-HT) to sensitize PCa to RT and investigate the underlying molecular mechanisms. METHODS: We developed a dedicated MW-HT heating setup, created an in vitro and in vivo MW-HT + RT treatment model for CRPC. We evaluated PC3 cell proliferation using CCK-8, colony experiments, DAPI staining, comet assay and ROS detection method. We also monitored nude mouse models of PCa during treatment, measured tumor weight, and calculated the tumor inhibition rate. Western blotting was used to detect DNA damage repair protein expression in PC3 cells and transplanted tumors. RESULTS: Compared to control, PC3 cell survival and clone formation rates decreased in RT + MW-HT group, demonstrating significant increase in apoptosis, ROS levels, and DNA damage. Lower tumor volumes and weights were observed in treatment groups. Ki-67 expression level was reduced in all treatment groups, with significant decrease in RT + MW-HT groups. The most significant apoptosis induction was confirmed in RT + MW-HT group by TUNEL staining. Protein expression levels of DNA-PKcs, ATM, ATR, and P53/P21 signaling pathways significantly decreased in RT + MW-HT groups. CONCLUSION: MW-HT + RT treatment significantly inhibited DNA damage repair by downregulating DNA-PKcs, ATM, ATR, and P53/P21 signaling pathways, leading to increased ROS levels, aggravate DNA damage, apoptosis, and necrosis in PC3 cells, a well-established model of CRPC.

Skin marker combined with surface-guided auto-positioning for breast DIBH radiotherapy daily initial patient setup: An optimal schedule for both accuracy and efficiency.

BACKGROUND AND PURPOSE: By employing three surface-guided radiotherapy (SGRT)-assisted positioning methods, we conducted a prospective study of patients undergoing SGRT-based deep inspiration breath-hold (DIBH) radiotherapy using a Sentine/Catalys system. The aim of this study was to optimize the initial positioning workflow of SGRT-DIBH radiotherapy for breast cancer. MATERIALS AND METHODS: A total of 124 patients were divided into three groups to conduct a prospective comparative study of the setup accuracy and efficiency for the daily initial setup of SGRT-DIBH breast radiotherapy. Group A was subjected to skin marker plus SGRT verification, Group B underwent SGRT optical feedback plus auto-positioning, and Group C was subjected to skin marker plus SGRT auto-positioning. We evaluated setup accuracy and efficiency using cone-beam computed tomography (CBCT) verification data and the total setup time. RESULTS: In groups A, B, and C, the mean and standard deviation of the translational setup-error vectors were small, with the highest values of the three directions observed in group A (2.4 ± 1.6, 2.9 ± 1.8, and 2.8 ± 2.1 mm). The rotational vectors in group B (1.8 ± 0.7°, 2.1 ± 0.8°, and 1.8 ± 0.7°) were significantly larger than those in groups A and C, and the Group C setup required the shortest amount of time, at 1.5 ± 0.3 min, while that of Group B took the longest time, at 2.6 ± 0.9 min. CONCLUSION: SGRT one-key calibration was found to be more suitable when followed by skin marker/tattoo and in-room laser positioning, establishing it as an optimal daily initial set-up protocol for breast DIBH radiotherapy. This modality also proved to be suitable for free-breathing breast cancer radiotherapy, and its widespread clinical use is recommended.

Advances in nanotechnology-based targeted-contrast agents for computed tomography and magnetic resonance.

X-ray computed tomography (CT) and magnetic resonance (MR) imaging are essential tools in modern medical diagnosis and treatment. However, traditional contrast agents are inadequate in the diagnosis of various health conditions. Consequently, the development of targeted nano-contrast agents has become a crucial area of focus in the development of medical image-enhancing contrast agents. To fully understand the current development of nano-contrast agents, this review provides an overview of the preparation methods and research advancements in CT nano-contrast agents, MR nano-contrast agents, and CT/MR multimodal nano-contrast agents described in previous publications. Due to the physicochemical properties of nanomaterials, such as self-assembly and surface modifiability, these specific nano-contrast agents can greatly improve the targeting of lesions through various preparation methods and clearly highlight the distinction between lesions and normal tissues in both CT and MR. As a result, they have the potential to be used in the early stages of disease to improve diagnostic capacity and level in medical imaging.

Design, Synthesis, and Target Identification of Novel Phenylalanine Derivatives by Drug Affinity Responsive Target Stability (DARTS) in Xanthomonas oryzae pv Oryzae.

The increasing resistance displayed by plant phytopathogenic bacteria to conventional pesticides has heightened the urgency for the exploration of novel antibacterial agents possessing distinct modes of action (MOAs). In this study, a series of novel phenylalanine derivatives with the unique structure of acylhydrazone dithioether have been designed and synthesized. Bioassay results demonstrated that most target compounds exhibited excellent in vitro antibacterial activity against Xanthomonas oryzae pv oryzae (Xoo) and Xanthomonas axonopodis pv citri (Xac). Among them, the EC50 values of L3, L4, L6, L21, and L22 against Xoo were 7.4, 9.3, 6.7, 8.9, and 5.1 µg/mL, respectively, superior to that of bismerthiazol (BT) and thiodiazole copper (TC) (41.5 and >100 µg/mL); the EC50 values of L3, L4, L5, L6, L7, L8, L20, L21, and L22 against Xac were 5.6, 2.5, 6.2, 4.1, 4.2, 6.4, 6.3, 3.6, and 5.2 µg/mL, respectively, superior to that of BT and TC (43.3 and >100 µg/mL). An unmodified drug affinity responsive target stability (DARTS) technology was used to investigate the antibacterial MOAs of active compound L22, and the 50S ribosomal protein L2 (RL2) as an unprecedented target protein in Xoo cells was first discovered. The target protein RL2 was then expressed and purified. Furthermore, the in vitro interactions by microscale thermophoresis (Kd = 0.050 µM) and fluorescence titration (Ka = 1.4 × 105 M-1) experiments also demonstrated a strong binding force between compound L22 and RL2. Overall, these results not only facilitate the development of novel antibacterial agents but also establish a reliable method for exploring the targets of bactericides.

Identification of natural Rutaecarpine as a potent tobacco mosaic virus (TMV) helicase candidate for managing intractable plant viral diseases.

BACKGROUND: Naturally occurring alkaloids are particularly suitable for use as pesticide precursors and further modifications due to their cost-effectiveness, unique mechanism of action, tolerable degradation, and environmental friendliness. The famous tobacco mosaic virus (TMV) is a persistent plant pathogenic virus that can parasitize many plants and severely reduce crop production. To treat TMV disease, TMV helicase acts as a crucial target by hydrolyzing adenosine triphosphate (ATP) to provide energy for double-stranded RNA unwinding. RESULTS: To seek novel framework alkaloid leads targeting TMV helicase, this work successfully established an efficient screening platform for TMV helicase inhibitors based on natural alkaloids. In vivo activity screening, enzyme activity detection, and binding assays showed that Rutaecarpine from Evodia rutaecarpa (Juss.) Benth exhibited excellent TMV helicase inhibitory properties [dissociation constant (Kd ) = 1.1 µm, half maximal inhibitory concentration (IC50 ) = 227.24 µm] and excellent anti-TMV ability. Molecular docking and dynamic simulations depicted that Rutaecarpine could stably bind in active pockets of helicase with low binding energy (ΔGbind = -17.8 kcal/mol) driven by hydrogen bonding and hydrophobic interactions. CONCLUSION: Given Rutaecarpine's laudable bioactivity and structural modifiability, it can serve as a privileged building block for further pesticide discovery.

Engineering Phenothiazine-Based Functional Mimics of Host Defense Peptides as New Agrochemical Candidates: Design, Synthesis, and Antibacterial Evaluation.

In the protracted "arms race" between host and plant pathogenic bacteria, host organisms have evolved powerful weapons known as host defense peptides (HDPs). However, natural HDPs are not suitable for large-scale applications; therefore, researchers have chosen to develop bespoke small-molecule functional mimics. Phenothiazine derivatives were developed as functional HDPs mimics, owing to their broad biological activity and high lipophilicity. The phenothiazine analogues designed in this study exhibited excellent in vitro bioactivity against the three Gram-negative bacteria Xanthomonas oryzae pv oryzae, Xanthomonas axonopodis pv citri, and Pseudomonas syringae pv actinidiae, with optimal EC50 values of 0.80, 0.31, and 1.91 µg/mL, respectively. Preliminary evidence suggests that compound C2 may act on bacterial cell membranes and interact with bacterial Deoxyribonucleic acid in the groove binding mode. In vivo trials showed that compound C2 was highly effective against rice leaf blight (51.97-56.69%), with activity superior to those of bismerthiazol (40.7-43.4%) and thiodiazole copper (30.2-37.1%). Our study provides strong evidence to support the development of phenothiazine derivatives into pesticide candidates.

Insights into a class of natural eugenol and its optimized derivatives as potential tobacco mosaic virus helicase inhibitors by structure-based virtual screening.

Plant diseases caused by malignant and refractory phytopathogenic viruses have considerably restricted crop yields and quality. To date, drug design targeting functional proteins or enzymes of viruses is an efficient and viable strategy to guide the development of new pesticides. Herein, a series of novel eugenol derivatives targeting the tobacco mosaic virus (TMV) helicase have been designed using structure-based virtual screening (SBVS). Structure-activity relationship indicated that 2 t displayed the most powerful bonding capability (Kd = 0.2 µM) along with brilliant TMV helicase ATPase inhibitory potency (IC50 = 141.9 µM) and applausive anti-TMV capability (EC50 = 315.7 µg/mL), ostentatiously outperforming that of commercial Acyclovir (Kd = 23.0 µM, IC50 = 183.7 µM) and Ribavirin (EC50 = 624.3 µg/mL). Molecular dynamics simulations and docking suggested ligand 2 t was stable and bound in the active pocket of the TMV helicase by multiple interactions. Given these superior properties, eugenol-based derivatives could be considered as the novel potential plant viral helicase inhibitors. Furthermore, this effective and feasible SBVS strategy established a valuable screening platform for helicase-targeted drug development.

Novel mandelic acid derivatives suppress virulence of Ralstonia solanacearum via type III secretion system.

BACKGROUND: Bacterial wilt induced by Ralstonia solanacearum is regarded as one of the most devastating diseases. However, excessive and repeated use of the same bactericides has resulted in development of bacterial resistance. Targeting bacterial virulence factors, such as type III secretion system (T3SS), without inhibiting bacterial growth is a possible assay to discover new antimicrobial agents. RESULTS: In this work, identifying new T3SS inhibitors, a series of mandelic acid derivatives with 2-mercapto-1,3,4-thiazole moiety was synthesized. One of them, F-24, inhibited the transcription of hrpY gene significantly. The presence of this compound obviously attenuated hypersensitive response (HR) without inhibiting bacterial growth of R. solanacearum. The transcription levels of those typical T3SS genes were reduced to various degrees. The test of the ability of F-24 in protecting plants demonstrated that F-24 protected tomato plants against bacterial wilt without restricting the multiplication of R. solanacearum. The mechanism of this T3SS inhibition is through the PhcR-PhcA-PrhG-HrpB pathway. CONCULSION: The screened F-24 could inhibit R. solanacearum T3SS and showed better inhibitory activity than previously reported inhibitors without affecting the growth of the strain, and F-24 is a compound with good potential in the control of R. solanacearum. © 2023 Society of Chemical Industry.

High FAAP24 expression reveals poor prognosis and an immunosuppressive microenvironment shaping in AML.

BACKGROUND: As a core member of the FA complex, in the Fanconi anemia pathway, FAAP24 plays an important role in DNA damage repair. However, the association between FAAP24 and patient prognosis in AML and immune infiltration remains unclear. The purpose of this study was to explore its expression characteristics, immune infiltration pattern, prognostic value and biological function using TCGA-AML and to verify it in the Beat AML cohort. METHODS: In this study, we examined the expression and prognostic value of FAAP24 across cancers using data from TCGA, TARGET, GTEx, and GEPIA2. To further investigate the prognosis in AML, development and validation of a nomogram containing FAAP24 were performed. GO/KEGG, ssGSEA, GSVA and xCell were utilized to explore the functional enrichment and immunological features of FAAP24 in AML. Drug sensitivity analysis used data from the CellMiner website, and the results were confirmed in vitro. RESULTS: Integrated analysis of the TCGA, TARGET and GTEx databases showed that FAAP24 is upregulated in AML; meanwhile, high FAAP24 expression was associated with poor prognosis according to GEPIA2. Gene set enrichment analysis revealed that FAAP24 is implicated in pathways involved in DNA damage repair, the cell cycle and cancer. Components of the immune microenvironment using xCell indicate that FAAP24 shapes an immunosuppressive tumor microenvironment (TME) in AML, which helps to promote AML progression. Drug sensitivity analysis showed a significant correlation between high FAAP24 expression and chelerythrine resistance. In conclusion, FAAP24 could serve as a novel prognostic biomarker and play an immunomodulatory role in AML. CONCLUSIONS: In summary, FAAP24 is a promising prognostic biomarker in AML that requires further exploration and confirmation.

Artificial intelligence predicts lung cancer radiotherapy response: A meta-analysis.

BACKGROUND: Artificial intelligence (AI) technology has clustered patients based on clinical features into sub-clusters to stratify high-risk and low-risk groups to predict outcomes in lung cancer after radiotherapy and has gained much more attention in recent years. Given that the conclusions vary considerably, this meta-analysis was conducted to investigate the combined predictive effect of AI models on lung cancer. METHODS: This study was performed according to PRISMA guidelines. PubMed, ISI Web of Science, and Embase databases were searched for relevant literature. Outcomes, including overall survival (OS), disease-free survival (DFS), progression-free survival (PFS), and local control (LC), were predicted using AI models in patients with lung cancer after radiotherapy, and were used to calculate the pooled effect. Quality, heterogeneity, and publication bias of the included studies were also evaluated. RESULTS: Eighteen articles with 4719 patients were eligible for this meta-analysis. The combined hazard ratios (HRs) of the included studies for OS, LC, PFS, and DFS of lung cancer patients were 2.55 (95 % confidence interval (CI) = 1.73-3.76), 2.45 (95 % CI = 0.78-7.64), 3.84 (95 % CI = 2.20-6.68), and 2.66 (95 % CI = 0.96-7.34), respectively. The combined area under the receiver operating characteristics curve (AUC) of the included articles on OS and LC in patients with lung cancer was 0.75 (95 % CI = 0.67-0.84), and 0.80 (95%CI = 0.0.68-0.95), respectively. CONCLUSION: The clinical feasibility of predicting outcomes using AI models after radiotherapy in patients with lung cancer was demonstrated. Large-scale, prospective, multicenter studies should be conducted to more accurately predict the outcomes in patients with lung cancer.

Phase separation in gene transcription control.

Phase separation provides a general mechanism for the formation of biomolecular condensates, and it plays a vital role in regulating diverse cellular processes, including gene expression. Although the role of transcription factors and coactivators in regulating transcription has long been understood, how phase separation is involved in this process is just beginning to be explored. In this review, we highlight recent advance in elucidating the molecular mechanisms and functions of transcriptional condensates in gene expression control. We discuss the different condensates formed at each stage of the transcription cycle and how they are dynamically regulated in response to diverse cellular and extracellular cues that cause rapid changes in gene expression. Furthermore, we present new findings regarding the dysregulation of transcription condensates and their implications in human diseases.

Effectiveness and Safety of Bu Shen Kai Qiao Fang in the Treatment of Alzheimer's Disease: Study Protocol for a Multicenter, Prospective, Real-World Clinical Trial.

Background: Alzheimer's disease (AD) is a common degenerative disease of the nervous system with serious impact on quality of life of patients and their families. With an aging population, AD has become a major public health problem in China and worldwide. However, the physiological and pathological mechanisms of AD have not been fully elucidated, and there is a lack of effective prevention and clinical treatment methods. Many studies have found that traditional Chinese medicine (TCM) has a good therapeutic effect on cognitive function in AD patients. Bu Shen Kai Qiao Fang (BSKQF) is one such Chinese herbal preparation used in the treatment of AD. We designed a protocol for a real-world clinical study of BSKQF combined with Donepezil hydrochloride (DH) to evaluate the efficacy and safety of this approach in the treatment of AD patients. Methods: This is a protocol for a real-world, multicenter, prospective, observational cohort study. The study will recruit 860 AD patients from four hospitals across China. Equal numbers of patients will be treated with BSKQF and DH or with DH only. The criteria for grouping are based primarily on patient preference. Outcome measures include scores on the Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment Scale (MOCA) and will be recorded at baseline, and at one, two and three months after enrollment. The plasma Aß42 and plasma Tau levels of participating patients will also be measured by ELISA at baseline and after 3 months of treatment. Safety metrics and adverse events (AEs) of participating patients will be monitored and recorded. Discussion: This study will evaluate the clinical efficacy and safety of BSKQF in the treatment of AD. The results will provide reliable evidence for the clinical application of BSKQF in the treatment of AD. Study Registration: Trial registration: Chinese Clinical Trial Registry, NO. ChiCTR2000039670, Registered 5 November 2020 https://www.chictr.org.cn/showprojEN.html?proj=63800.

Novel 1,3,4-Thiadiazole Derivatives: Synthesis, Antiviral Bioassay and Regulation the Photosynthetic Pathway of Tobacco against TMV Infection.

Tobacco mosaic virus (TMV) is a systemic virus that poses a serious threat to crops worldwide. In the present study, a series of novel 1-phenyl-4-(1,3,4-thiadiazole-5-thioether)-1H-pyrazole-5-amine derivatives was designed and synthesized. In vivo antiviral bioassay results indicated that some of these compounds exhibited excellent protective activity against TMV. Among the compounds, E2 (EC50 = 203.5 µg/mL) was superior to the commercial agent ningnanmycin (EC50 = 261.4 µg/mL). Observation of tobacco leaves infected with TMV-GFP revealed that E2 could effectively inhibit the spread of TMV in the host. Further plant tissue morphological observation indicated that E2 could induce the tight arrangement and alignment of the spongy mesophyll and palisade cells while causing stomatal closure to form a defensive barrier to prevent viral infection in the leaves. In addition, the chlorophyll content of tobacco leaves was significantly increased after treatment with E2, and the net photosynthesis (Pn) value was also increased, which demonstrated that the active compound could improve the photosynthetic efficiency of TMV-infected tobacco leaves by maintaining stable chlorophyll content in the leaves, thereby protecting host plants from viral infection. The results of MDA and H2O2 content determination revealed that E2 could effectively reduce the content of peroxides in the infected plants, reducing the damage to the plants caused by oxidation. This work provides an important support for the research and development of antiviral agents in crop protection.

Design, Synthesis, In Vitro Antifungal Activity and Mechanism Study of the Novel 4-Substituted Mandelic Acid Derivatives.

Plant diseases caused by phytopathogenic fungi are a serious threat in the process of crop production and cause large economic losses to global agriculture. To obtain high-antifungal-activity compounds with novel action mechanisms, a series of 4-substituted mandelic acid derivatives containing a 1,3,4-oxadiazole moiety were designed and synthesized. In vitro bioassay results revealed that some compounds exhibited excellent activity against the tested fungi. Among them, the EC50 values of E13 against Gibberella saubinetii (G. saubinetii), E6 against Verticillium dahlia (V. dahlia), and E18 against Sclerotinia sclerotiorum (S. sclerotiorum) were 20.4, 12.7, and 8.0 mg/L, respectively, which were highly superior to that of the commercialized fungicide mandipropamid. The morphological studies of G. saubinetii with a fluorescence microscope (FM) and scanning electron microscope (SEM) indicated that E13 broke the surface of the hyphae and destroyed cell membrane integrity with increased concentration, thereby inhibiting fungal reproduction. Further cytoplasmic content leakage determination results showed a dramatic increase of the nucleic acid and protein concentrations in mycelia with E13 treatment, which also indicated that the title compound E13 could destroy cell membrane integrity and affect the growth of fungi. These results provide important information for further study of the mechanism of action of mandelic acid derivatives and their structural derivatization.

Design, Synthesis, and Study of the Dual Action Mode of Novel N-Thienyl-1,5-disubstituted-4-pyrazole Carboxamides against Nigrospora oryzae.

Due to the single target but extensive application of commercialized succinate dehydrogenase inhibitors (SDHIs), resistance problems have gradually become apparent in recent years. To solve this problem, a series of novel N-thienyl-1,5-disubstituted-1H-4-pyrazole carboxamide derivatives were designed and synthesized in this work based on the active skeleton 5-trifluoromethyl-4-pyrazole carboxamide. The bioassay results indicated that some target compounds exhibited excellent in vitro antifungal activities against the eight phytopathogenic fungi tested. Among them, the EC50 values of T4, T6, and T9 against Nigrospora oryzae were 5.8, 1.9, and 5.5 mg/L, respectively. The in vivo protective and curative activities of 40 mg/L T6 against rice infected with N. oryzae were 81.5% and 43.0%, respectively. Further studies revealed that T6 not only significantly inhibited the growth of N. oryzae mycelia but also effectively hindered spore germination and germ tube elongation. Morphological studies using scanning electron microscopy (SEM), fluorescence microscopy (FM), and transmission electron microscopy (TEM) found that T6 could affect the mycelium membrane integrity by increasing cell membrane permeability and causing peroxidation of cellular lipids, and these results were further verified by measuring the malondialdehyde (MDA) content. The IC50 value of T6 against succinate dehydrogenase (SDH) was 7.2 mg/L, lower than that of the commercialized SDHI penthiopyrad (3.4 mg/L). Further, ATP content detection and the results after docking T6 and penthiopyrad suggested that T6 was a potential SDHI. These studies demonstrated that active compound T6 could both inhibit the activity of SDH and affect the integrity of the cell membrane at the same time via a dual action mode, which is different from the mode of action of penthiopyrad. Thus, this study provides a new idea for a strategy to delay resistance and diversify the structures of SDHIs.

Synthesis, Antifungal Evaluation, 3D-QSAR, and Preliminarily Mechanism Study of Novel Chiral Mandelic Acid Derivatives.

To investigate the effect of spatial configuration on the biological activity of the compounds, a series of chiral mandelic acid derivatives with a moiety of 1,3,4-oxadiazole thioether have been designed and synthesized. Bioassay results demonstrated that most title compounds with the S-configuration exhibited better in vitro antifungal activity against three plant fungi, such as H3' (EC50 = 19.3 µg/mL) against Gibberella saubinetii, which was approximately 16 times higher than that of H3 (EC50 = 317.0 µg/mL). CoMFA and CoMSIA models were established for 3D-QSAR analysis and provided an important support for further optimization of this series of compounds. Comparing the preliminary mechanism studies between enantiomers (H3 and H3') found that the S-configuration compound (H3') exhibited a stronger ability to destroy the surface structure of G. saubinetii mycelia, causing the leakage of intracellular substances to accelerate and the growth of the hyphae to be inhibited. The results provided a novel view for the further optimization of this series of active compounds and deep mechanism study of chiral pesticides.