Effective Concentration Values Research Articles

Spatial Trends of Cadmium and Zinc Concentrations in Water and Enrichments in Surficial Sediments within Nyanza (Winam) Gulf of Lake Victoria (East Africa)

Metal pollution contributes significantly to the environmental degradation of lake ecosystems. The study evaluated the spatial trends in cadmium and zinc concentrations in surface water, un-fractioned and the <63µm grain size fraction (silt and clay) of surficial sediments within Nyanza Gulf, from lake monitoring stations in 2010 and 2012 surveys. Significantly higher Zn total concentrations were found in surface lake water compared to earlier surveys, but cadmium levels were low and not detectable as in previous studies. Variable contents of Zn and Cd were found in un-fractioned and finer sediment fractions. “Much higher sediment Cd contents were found in 2010 compared to other surveys. Major areas under river and urban influences recorded much higher sediment Cd contents than offshore sediments. However, there were no significant differences between Cd and Zn contents between the gulf and main lake zones. Cd sediment enrichment factors were highly variable compared to Zn, which showed a more uniform trend in most of the gulf areas, but Cd sediment enrichment factors appear to increase when compared to previous data. The spatial distribution of Cd and Zn in the surficial sediments show unpolluted to moderate pollution levels, according to geo-accumulation index. Only 4% of Zn samples exceeded the sediment quality threshold effect concentration (TEC) values, but all were below the mid-range effect values. Cadmium is a recognized toxicant and there are potential ecological concerns regarding the variable sediment Cd contents since it has been found previously in bioavailable forms in surficial sediments and 2% of the samples contained Cd (un-fractioned sediment) above the threshold effect concentration during the 2012 survey compared to 51 % in 2010, but none exceeded the severe effect levels”. Continuous monitoring of priority heavy metals is of relevance on the understanding of potential long-term ecological impacts to the lake ecosystem.

Design, synthesis, X-ray crystal structure, and antifungal evaluation of new acetohydrazide derivatives containing a 4-thioquinazoline moiety.

To find efficient agricultural fungicides, 29 new 4-thioquinazoline-containing acetohydrazide derivatives were prepared and tested for their fungicidal properties. All of the target compounds were characterized by 1H and 13C nuclear magnetic resonance and high-resolution mass spectrometry techniques, and the molecular structure of compound A2 was verified by single-crystal X-ray diffraction measurement. The experimental results revealed that many compounds from this series had impressive inhibition efficacies in vitro against the tested fungi. For example, compound A25 was identified as the best fungicidal agent against Rhizoctonia solani with an EC50 (half-maximal effective concentration) value of 0.66 μg mL-1, superior to those of the commercial fungicides chlorothalonil, carbendazim and boscalid. Additionally, this compound displayed favorable protection and curative activities in vivo against rice sheath blight caused by R. solani. Antifungal mechanistic studies on compound A25 indicated that this compound exerted its strong anti-R. solani effects probably through an effective inhibition of fungal succinate dehydrogenase activity [half-maximal inhibitory concentration (IC50) = 4.88 μm] and the impairment of cell membrane integrity, based on the results from enzymatic bioassays, molecular docking studies, and scanning and transmission electron microscopy observations. Acetohydrazide derivatives containing the 4-thioquinazoline moiety had the potential to be employed as lead compounds for developing more efficient agricultural fungicides in the near future. © 2024 Society of Chemical Industry.

The actions of varenicline on alkaloids from Conium maculatum (poison hemlock), Lupinus sulphureus (sulphur lupine) and Nicotiana glauca (tree tobacco).

Evidence-based therapies to manage the clinical signs of intoxication caused by toxic plants in livestock are lacking. For that reason, the aim of this work was to develop a drug-based intervention for the management of clinical signs of piperidine alkaloid intoxication in livestock. The actions of anabasine, coniine, γ-coniceine, and two total alkaloid extracts from Lupinus sulphureus were compared in the presence and absence of the nicotinic acetylcholine receptor partial agonist varenicline in RD cells, mice and goats. Pretreatment of RD cells with 10.0μM varenicline significantly shifted the anabasine fifty percent effective concentration (EC50) value to a greater concentration and blocked the response of the cells to coniine. γ-coniceine did not have any effect on RD cells as measured by membrane potential sensing dye. Swiss Webster mice median lethal dose (LD50) values for anabasine, coniine, γ-coniceine were 1.5, 5.5, and 3.7mg/kg respectively, and pretreatment with 10.0mg/kg i. p. dosed varenicline shifted the LD50 values to 4.2, 9.1, and 4.3mg/kg respectively. The rodent LD50 value of the Pendelton, WA L. sulphureus quinolizidine alkaloid extract was shifted to a lesser concentration by varenicline while the Ritzville, WA L. sulphureus piperidine alkaloid extract was shifted to a greater concentration by varenicline. The clinical signs of intoxication in goats orally dosed with Conium maculatum were exacerbated by 0.5, 1.0 and 10.0mg/kg i. v. dosed varenicline. These results suggest that varenicline was effective at shifting piperidine alkaloid EC50 values in RD cells and increasing piperidine but not quinolizidine alkaloid LD50 values in mice and was not useful at managing the clinical signs of poison hemlock intoxication in goats.

Design and synthesis of camphor-thiazole derivatives as potent antifungal agents: structure-activity relationship and preliminary mechanistic study.

Plant pathogenic fungi pose a severe threat to crop yield and food security. This study aims to investigate the potential antifungal activity and mechanism of action of camphor-thiazole derivatives against six plant pathogenic fungi. A novel series of camphor-thiazole derivatives were designed, synthesized and evaluated for their antifungal effects against Rhizoctonia solani, Fusarium graminearum, Valsa mali, Alternaria solani, Colletotrichum orbiculare and Botryitis cinerea. Most of the synthesized camphor-thiazole derivatives exhibited notable antifungal activity. Amongst them, compounds C5, C10 and C17 showed significant activity against R. solani with median effective concentrations (EC50) values in the range 3-4 μg mL-1, demonstrating superior antifungal efficacy to the control drug boscalid (EC50 = 1.23 μg mL-1). Structure-activity relationship and density functional theory analysis emphasized the critical role of substituent selection in optimizing the biological activity of these compounds. Moreover, preliminary mechanistic studies revealed that compound C5 induced abnormal mycelial and cellular morphology in R. solani as observed using scanning and transmission electron microscopy, and triggered the production and accumulation of reactive oxygen species. Additionally, the increased concentration of C5 resulted in enhanced cell membrane permeability. In this study, the designed and optimized compound C5 emerged as a promising candidate for potent antifungal agents. The results demonstrate that synthesized camphor-thiazole derivatives possess potent antifungal activity and can serve as lead compounds for further optimization in antifungal agent development. © 2024 Society of Chemical Industry.

Sulfone derivatives containing an oxazole moiety as potential antibacterial agents: design, synthesis, antibacterial activity, and mechanism.

Bacterial diseases in plants pose a serious threat to crop production, leading to substantial food loss every year. Prolonged and repeated use of a single antibacterial agent can promote resistance in pathogenic bacteria. Therefore, there is an urgent need to develop efficient antibacterial agents for the treatment of bacterial diseases. Sulfone derivatives containing an oxazole moiety were designed and synthesized. Subsequently, their biological activities were evaluated. The half-maximal effective concentration (EC50) value of compound F10 against Xanthomonas oryzae pv. oryzicola (Xoc) was 1.1 mg/L, which was higher than those of commercial antibacterial agents, thiodiazole-copper (91.5 mg/L) and bismerthiazol (76.0 mg/L). The curative and protective effects of compound F10 against bacterial leaf streak in rice were 43.8% and 48.4%, respectively, at 200 mg/L, which were significantly superior to those of thiodiazole-copper (25.0% and 25.8%, respectively) and bismerthiazol (31.3% and 38.7%, respectively). Compound F10 inhibits Xoc by increasing the permeability of the cell membrane, inhibiting the production of extracellular polysaccharides, and affecting flagellar movement on the cell membrane. In addition, F10 reduces the pathogenicity of pathogenic bacteria, induces the accumulation of reactive oxygen species (ROS) in pathogenic bacteria, and produces adverse reactions. Compound F10 weakens bacterial pathogenicity by affecting the signal transduction of plant hormones, programmed cell death, and enhancing the ability to resist infection through the autoimmune response of rice. Therefore, compound F10 can be used as a potential antibacterial agent in future applications. © 2024 Society of Chemical Industry.

Synthesis of Indol-3-yl Morpholino Derivatives Containing a Hydrazone Moiety as Potential Antiplant Virus Agents.

A series of indol-3-yl morpholino derivatives containing a hydrazone moiety were designed and synthesized using indole-3-carboxylic acid as the starting material. The antiviral activities of the synthesized compounds were systematically evaluated. Compound D35, optimized using the comparative molecular field analysis (CoMFA) model, exhibited the most potent inhibitory activity against Tobacco mosaic virus (TMV) in vivo with a 50% effective concentration (EC50) value of 69.9 mg/L and exceeded that of Ningnanmycin (142.4 mg/L). Molecular docking and molecular dynamics simulations revealed that compound D35 could form stable interactions with the TMV coat protein (CP), exhibiting a lower binding energy of -9.37 kcal/mol compared to that of Ningnanmycin (-8.55 kcal/mol). Microscale thermophoresis (MST) experiments further confirmed the stronger binding affinity of compound D35 for the TMV CP than Ningnanmycin. Additionally, transmission electron microscopy (TEM) demonstrated that compound D35 effectively disrupts the TMV particles and inhibits their spread. These collective findings strongly suggest that compound D35 has the potential to serve as a lead compound for the development of novel antiviral agents.

Novel Amanitin-based Antibody Drug Conjugates (ATAC®) targeting TROP2 for the treatment of Pancreatic Cancer.

Trophoblast cell surface antigen 2 (TROP2) exhibits aberrant expression in pancreatic cancer, correlating with metastasis, advanced tumor stage and poor prognosis of pancreatic ductal adenocarcinoma (PDAC) patients. TROP2 has been recognized as a promising therapeutic target for antibody drug conjugates (ADCs), as evidenced by the approval of the anti-TROP2 ADC Trodelvy® for the treatment of triple negative breast cancer. In this study we report the generation of novel second-generation amanitin based ADCs (ATAC®s) targeting TROP2, comprising the humanized RS7 antibody of Trodelvy® (hRS7) and the highly potent payload amanitin. The specific in vitro binding, efficient antigen internalization, and high cytotoxicity of hRS7 ATAC®s with half maximal effective concentration (EC50) values in the picomolar range in TROP2-expressing cells constituted the foundation for preclinical in vivo evaluation. The hRS7 ATAC®s demonstrated a significant reduction in tumor growth in vivo in subcutaneous xenograft mouse models of pancreatic cancer and triple negative breast cancer at well-tolerated doses. The antitumor efficacy correlated with the level of TROP2 expression on the tumors and the in vivo tumor uptake of the ATAC®s. The long half-life of 9.7-10.7 days of hRS7 ATAC®s without premature payload release in serum supported a high therapeutic index. Notably, the efficacy of the hRS7 ATAC®s was superior to that of Trodelvy® with complete tumor eradication in both, refractory pancreatic and triple negative breast cancer xenograft models. In summary, hRS7 ATAC®s represent a highly effective and well-tolerated targeted therapy, and our data support their development for pancreatic cancer and other TROP2-expressing tumors.

Chimeric peptides targeting the receptor-binding domain of SARS-CoV-2 variants inhibit ACE2 interaction.

The receptor-binding domain (RBD) of the SARS-CoV-2 spike (S) protein is pivotal in facilitating viral entry and serves as a major target for vaccine development and therapeutics. Despite undergoing mutations aimed at evading host immunity, certain regions within the RBD remain conserved. This study aimed to identify peptides capable of interacting with these conserved regions of the RBD across various variants and assess their neutralization potential. The PhD-12 phage display library underwent screening to identify phages binding to the RBD. Selected phage clones were examined for binding to the RBD of multiple variants, including 2019-nCoV, Delta (B.1.617.2), Omicron (B.1.1.529), and XBB. Peptides, expressed as chimeric constructs, were tested for their binding to the RBD, the Omicron trimeric S, inactivated SARS-CoV-2 virus, and neutralizing activity. The binding sites were analyzed using Molecular Docking. Two selected phage clones displayed peptides binding to the RBD of multiple variants. Chimeric T hioredoxin-peptides (Trx-RB9 and Trx-RB10) exhibited binding to both inactivated SARS-CoV-2 and the Omicron trimeric S, with half-maximum effective concentrations (EC50 ) values of 111.9 and 360.2 nM, respectively. Molecular docking revealed distinct binding sites within the RBD of the Omicron trimeric S for both Trx-RB9 and Trx-RB10. A mixture of Trx-RB9 and Trx-RB10 inhibited 78% of the binding of recombinant human ACE2 to the Omicron trimeric S. The chimeric Trx-RB9 and Trx-RB10 peptides bind to the RBD of SARS-CoV-2 variants and inhibit the binding of ACE2 to the RBD of the Omicron trimeric S.

Combination of atmospheric and room temperature plasma and ribosome engineering techniques to enhance the antifungal activity of Bacillus megaterium L2 against Sclerotium rolfsii.

Sclerotium rolfsii is an extremely destructive phytopathogenic fungus that causes significant economic losses. Biocontrol strategies utilizing antagonistic microorganisms present a promising alternative for controlling plant pathogens. Bacillus megaterium L2 has been identified as a potential microbial biocontrol agent in our previous study; however, its efficacy in controlling pathogens has yet to meet current demands. This study aims to enhance the antifungal activity of strain L2 against S. rolfsii R-67 through a two-round mutagenesis strategy and to preliminarily investigate the mutagenesis mechanism of the high antifungal activity mutant. We obtained mutant Dr-77 with the strongest antifungal activity against R-67, and its cell-free supernatant significantly reduced the infection potential of R-67 to Amorphophallus konjac corms, which may be attributed to the antimicrobial compound phenylacetic acid (PAA), and PAA content in Dr-77 (5.78 mg/mL) was 28.90 times higher than original strain L2. This compound exhibited strong antifungal ability against R-67, with a half maximal effective concentration (EC50) value of 0.475 mg/mL, significantly inhibiting mycelial growth and destroying the ultrastructure of R-67 at EC50 value. Notably, PAA also exhibited broad-spectrum antifungal activity against six phytopathogens at EC50 value. Moreover, genome analysis revealed nine different gene mutations, including those involved in PAA biosynthesis, and the activities of prephenate dehydratase (PheA) and phenylacetaldehyde dehydrogenase (ALDH) in PAA biosynthesis pathway were significantly increased. These results suggest that the elevated PAA content is a primary factor contributing to the enhanced antifungal activity of Dr-77, and that this mutagenesis strategy offers valuable guidance for the breeding of functional microbial resources. © 2024 Society of Chemical Industry.

Antifungal activity of chalcone derivatives containing 1,2,3,4-tetrahydroquinoline and studies on them as potential SDH inhibitors.

A large number of pathogenic fungi have caused serious damage to the global crop yield, and drug resistance is always a topic that cannot be avoided for traditional fungicides. Therefore, finding efficient, green, and low-toxic fungicides is our primary task, which brings opportunities for the development of natural product green pesticides. Twenty chalcone derivatives containing 1,2,3,4-tetrahydroquinoline were designed and synthesized, and the compounds were tested for their fungicidal effects against eight plant pathogenic fungi in vitro. The results demonstrate that the original splicing did not have fungicidal activity, so a piperazine fragment was introduced; the test results revealed that H1-H10 all had good antifungal activity. Among them, H4 showed the highest inhibitory activity against Phytophthora capsici (Pc) with a median effect concentration (EC50) value of 5.2 μg/mL, which was higher than that of the control drugs Azoxystrobin (EC50 = 80.2 μg/mL) and Fluopyram (EC50 = 146.8 μg/mL). After the study, it was demonstrated that H4 mainly acted on the cell membrane against Phytophthora capsici and inhibited the activity of the marker enzyme of mitochondria (SDH) in the fungus. H4 has significant resistance to Phytophthora capsici and also plays a significant role in inhibiting SDH activity, providing a new direction for the development of green pesticides. © 2024 Society of Chemical Industry.

Antioxidant activity, enzyme inhibition, photoprotection, cytotoxicity, and phytochemical profiling of sea lavender (Limonium algarvense Erben) seed extracts for dermo-cosmetic use

BackgroundDespite sea lavender being a medicinal species, research on its seeds’ biological properties and chemical composition is unexplored. Thus, this study evaluated the effect of different extraction solvents on the biological activities and chemical profile of greenhouse-cultivated sea lavender seeds, aiming at their potential use as a dermo-cosmetic ingredient. Therefore, ethyl acetate, acetone, ethanol, and water extracts were examined for their antioxidant activity, enzyme inhibition, photoprotection, and cytotoxicity, followed by phytochemical analysis through spectrophotometric methods, further detailed by Ultrahigh-Performance Liquid Chromatography Coupled with Electrospray Ionization Mass/Mass Spectrometry (UHPLC-Esi-MS/MS).ResultsThe water extract demonstrated significant antioxidant activity, evidenced by low half maximal effective concentration (EC50) values in scavenging 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radicals, reducing iron and chelating copper (296, 478, 230 and 678 µg/mL, respectively). The ethanol extract was more effective in inhibiting cosmetic-related enzymes, particularly elastase and hyaluronidase (2.18 and 3.21 µg/mL, respectively). The water and acetone extracts had the highest sun protection factors (23.2 and 18.9, respectively). All the extracts had nil to weak cytotoxicity (70–120% cell viability) towards mammalian cell lines. The water extract had the highest phenolics and condensed tannins (115 and 78.30 mg/g extract, respectively), while the ethanol contained the most flavonoids (62.73 mg/g extract). UHPLC-ESI–MS/MS analysis identified ethyl gallate, myricetin, rutin, and quercetin as major components of the ethanol extract, whereas myricetin-O-rutinoside isomers are predominant in the water extract.ConclusionsThese findings highlight the potential of greenhouse-cultivated sea lavender seeds as potential dermo-cosmetic ingredients, with ethanol and water extracts demonstrating superior biological activities and chemical profiles, significantly contributing to general skin health and protection.

Potential PDE4A inhibition-mediated neuroprotective effects of psoralidin.

This study aimed to investigate the effect of psoralidin, a natural phenolic coumarin compound, on MK-801-induced neurotoxicity that may cause Alzheimer's disease and to determine the phosphodiesterase(PDE)-related molecular mechanism of action. In this study, neurotoxicity was performed using the MK-801 in the HT-22 cell line. The effects of compounds on the proliferation of HT-22 cells were determined by Real-Time Cell Analysis (RTCA). After measuring the total protein concentration, the PDE4A protein level was determined using the Western blot method. Psoralidin (100, 200, 400 µM) has been shown to have a neuroprotective effect against MK-801-induced neurotoxicity, as indicated by Real-Time Cell Analysis. In HT-22 cells, the half maximal effective concentration (EC50) value of psoralidin was calculated to be 230.4 µM, IC50 value of MK-801 was calculated to be 62.4 µM at 24 hours. It has been determined that psoralidin (200, 400 µM) inhibits PDE4A by using the Western blot method. This research uncovers that psoralidin has neuroprotective effects in MK801-associated accumulation of the excitatory amino acid glutamate neurodegeneration and Alzheimer's disease.

Design, synthesis, and structure–activity relationships of xanthine derivatives as broad-spectrum inhibitors of coronavirus replication

Illuminated by insights into the hijacking of host cellular metabolism by coronaviruses, we identified an initial hit compound 7030B-C5, characterized by a xanthine scaffold, via a cellular-level phenotypic screening from a domestic repertoire of lipid-modulating agents. A series of derivatives were synthesized and optimized through comprehensive structure–activity relationship (SAR) studies focusing on the N-1, C-8, and N-7 positions of xanthine and preliminary exploration on the N-3 position and parent nucleus. Compounds 10e, 10f and 10o, featuring modifications at the N-7 position, showed inhibitory activity with half maximal effective concentration (EC50) values in the three-digit nanomolar range against human coronavirus-229E (HCoV-229E). In particular, compound 10o exerted superior potency across various coronavirus strains, including HCoV-229E, HCoV-OC43, and the Omicron variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Further investigations revealed that 10o acted on the post-entry stages of virus replication and exhibited a distinctive antiviral mechanism from that of clinically approved nirmatrelvir and molnupiravir. Moreover, drug combination study indicates that 10o operates additively with nirmatrelvir, molnupiravir or omicsynin B4, a dual inhibitor of host proteases for S protein priming. Additionally, in vivo assessments show that 10o has favorable pharmacokinetic and safety profiles compared to its parent compound 7030B-C5. These findings underscore the potential of 10o as a promising antiviral candidate for the treatment of current and potential future coronavirus infections.

Baseline Sensitivity and Toxicity Mechanisms of Prochloraz to Alternaria alternata Strains Associated with Maize Leaf Blight in Heilongjiang Province in China.

Alternaria species are fungal pathogens that can infect maize, causing leaf blight disease and significant economic losses. This study aimed to determine the baseline sensitivity to prochloraz of A. alternata isolates obtained from diseased maize leaves collected from Heilongjiang Province by assessing the half-maximal effective concentration (EC50) values. The EC50 values of prochloraz ranged from 0.0550 to 2.3258 μg/ml, with an average of 0.9995 ± 0.5192 μg/ml. At EC50 (1.2495 μg/ml) and 2EC50 (2.4990 μg/ml), prochloraz increased the number of mycelial offshoots, disrupted the cell membrane integrity of conidia and mycelia, and resulted in a reduced ergosterol content in the mycelia. Prochloraz significantly affected the mycelial cell membrane permeability and increased the malondialdehyde content and superoxide dismutase activity. No cross-resistance was detected between prochloraz and other fungicides. These data demonstrate that prochloraz is a promising fungicide for managing maize leaf blight caused by A. alternata and provide novel insights into understanding the mechanism of prochloraz toxicity against A. alternata isolates.

Phenazine-1-carboxamide Regulates Pyruvate Dehydrogenase of Phytopathogenic Fungi to Control Tea Leaf Spot Caused by Didymella segeticola.

Due to a lack of understanding of the disease epidemiology and comprehensive control measures, tea leaf spot caused by Didymella segeticola has a significant negative impact on tea yield and quality in the tea plantations of Southwest China. Phenazine-1-carboxamide (PCN) is a phenazine compound derived from Pseudomonas species, which exhibits antimicrobial activity against various pathogens. However, its inhibitory mechanism is not yet clear. The current study evaluated the inhibitory activity of PCN against various phytopathogenic fungi and found that PCN has inhibitory activity against multiple pathogens, with a half-maximal effective concentration (EC50) value for D. segeticola of 16.11 μg/mL in vitro and a maximum in-vivo curative activity of 72.28% toward tea leaf spot. Morphological changes in the hyphae after exposure to PCN were observed through microstructure and ultrastructure analysis, and indicated that PCN causes abnormalities in the hyphae, such as cytoplasmic coagulation, shortened hyphal inter-septum distances, and unclear boundaries of organelles. Transcriptomic analysis revealed that PCN upregulated the expression of genes related with energy metabolism. PCN significantly reduced the ATP concentration in the hyphae and decreased mitochondrial membrane potential. Molecular docking analysis indicated that PCN binds to one of the candidate target proteins, pyruvate dehydrogenase, with lower free energy of -10.7 kcal/mol. This study indicated that PCN can interfere with energy metabolism, reducing ATP generation, ultimately affecting hyphal growth. Overall, PCN shows potential for future application in the control of tea leaf spot due to its excellent antifungal activity and unique mode of action.

Evaluation of Urbanization Influences on Beach Sediment Contamination with Heavy Metals Along the Littoral Zone of Alexandria City, Egypt

The western coastal area of Alexandria City, Egypt, faces significant environmental challenges due to heavy metal (HM) contamination in beach sediments, driven by intensive urbanization, tourism, commercial harbors, and industrial activities. Therefore, this study focuses on geochemically assessing HM levels in sediment samples from 28 sites and employed various descriptive and multivariate statistical approaches, pollution indices, and sediment quality guidelines (SQGs) to identify pollution hotspots, define contamination grades, and assess the quality of beach sediments. The average concentrations of Cd, Co, Cr, Cu, Pb, and Zn were 25.7, 30, 2.2, 7.5, 2.9, and 8.0 times, respectively, compared to the geochemical background (carbonate sedimentary rocks). et al.-Hanuvil Beach, relatively elevated contents of these metals were recorded. In addition, samples showed Zn levels higher than the corresponding probable effect concentration (PEC) and effect range medium (ERM) values, suggesting adverse impacts on biota. The principal component (PC) analysis revealed the anthropogenic origin of Cd, Co, and Pb in PC1, the mixed origin of Cr, Cu, Mn, and Zn in PC2, and the natural source of Fe in PC3. According to the applied single pollution indices, HM contamination grades were ranked in ascending order of Mn < Fe < Cr < Cd < Cu < Pb < Zn < Co. In conclusion, the HMs (Cu, Zn, Cd, Co, Pb, and Cr) in the study area are anthropogenic, attributed mainly to untreated discharge of municipal and industrial wastewater and solid wastes, atmospheric deposition of air pollutants, and tourism activities.

Resistance risk assessment of Rhizoctonia solani to four fungicides.

Hexaconazole, thifluzamide, difenoconazole and azoxystrobin are widely used fungicides for the control of Rhizoctonia solani in China. However, few studies have assessed the sensitivity and resistance risk of R. solani to these four fungicides. The sensitivities of 126 R. solani isolates to hexaconazole, thifluzamide, difenoconazole and azoxystrobin were determined, with average half maximal effective concentration (EC50) values of 0.0386, 0.0659, 0.663 and 1.508 μg mL-1, respectively. Field resistance monitoring of the four fungicides showed that the three isolates had moderate resistance to difenoconazole. Resistant mutants to the four fungicides were obtained by fungicide adaptation, and resistance could be stably inherited by most mutants. Compared with those of the parent isolates, the biological characteristics of hexaconazole-resistant mutants exhibited enhanced or similar compound fitness index (CFI), whereas most of the other mutants displayed reduced or comparable CFI. There was evidence of positive cross-resistance between hexaconazole and difenoconazole. In the presence of fungicides, the expression of the CYP51 genes in hexaconazole- and difenoconazole-resistant mutants significantly increased, the expression of SDH genes in thifluzamide-resistant mutants significantly decreased, and the expression of the Cyt b gene in azoxystrobin-resistant mutants did not significantly change. Based on these data, we speculated that R. solani had a low-to-medium resistance risk to four fungicides. The change of target gene expression may be one of the reasons for fungicide resistance in R. solani. This study provides a theoretical basis for monitoring resistance emergence and developing resistance management strategies to control R. solani. © 2024 Society of Chemical Industry.

Rational design and discovery of novel hydrazide derivatives as potent succinate dehydrogenase inhibitors inspired by natural d/l-camphor.

Succinate dehydrogenase inhibitors (SDHIs) have rapidly become one of the fastest-growing categories of fungicides used against plant pathogenic fungi. Recent research advancements have emphasized that structural modifications of SDHIs using naturally sourced scaffolds represent an innovative strategy for developing new, highly effective, broad-spectrum fungicides. A novel series of d/l-camphorhydrazide derivatives potentially targeting fungal succinate dehydrogenase (SDH) were designed, synthesized and evaluated for their antifungal effects against Rhizoctonia solani, Fusarium graminearum, Valsa mali and Botrytis cinerea. Amongst them, compounds A1-7 (d-camphor) and A2-7 (l-camphor) displayed excellent in vitro activity against R. solani with median effective concentration (EC50) values of 0.38 and 0.48 μg mL-1, which were obviously superior to that of boscalid (0.87 μg mL-1). A2-5 (l-camphor, EC50 = 3.27 μg mL-1) exhibited good activity against V. mali. A2-7 (2.13 μg mL-1), A2-21 (5.2 μg mL-1) and A1-5 (5.15 μg mL-1) showed good antifungal activity against F. graminearum with EC50 values below that of boscalid (5.85 μg mL-1). Preliminary mechanistic studies, using scanning and transmission electron microscopy, indicated that compound A1-7 induced disordered entanglement of hyphae, shrinkage of hyphal surfaces, and vacuole swelling and rupture, which disrupted normal hyphal growth. Additionally, compound A1-7 induced the production and accumulation of reactive oxygen species, disrupted mitochondrial membrane potential, and effectively inhibited the germination and formation of sclerotia in R. solani. Moreover, the molecular docking results and SDH enzyme assays yielded promising outcomes. In this study, the designed and optimized compounds A1-7 and A2-7 emerged as promising candidates for SDH-targeting fungicides, demonstrating strong antifungal activity. These compounds hold potential as new antifungal agents for further research. © 2024 Society of Chemical Industry.

Novel Flavonol Derivatives Containing Quinoxaline: Insights into the Antifungal Mechanism against Sclerotinia sclerotiorum.

In this study, 12 pairs of tautomeric flavonol derivatives containing quinoxaline were synthesized. The results of antifungal activity showed that in the enol-keto tautomerism, the target compounds containing keto (YB series) had better inhibitory activity against Sclerotinia sclerotiorum (S.s.) than compounds containing enol (YA series). YB9 showed the strongest antifungal activity against S.s., and the median effective concentration (EC50) value was 1.0 μg/mL, which was better than azoxystrobin (Az, 35.3 μg/mL). In vivo fungal inhibition experiments showed that the protective activity of YB9 against rape leaves was 83.4% at 200 μg/mL, which was superior to that of Az (70.2%). The activity of succinate dehydrogenase and molecular docking results showed that YB9 had a stronger antifungal effect than YA9. The results of oxalic acid content determination showed that YB9 could reduce the pathogenic ability of S.s. Then, the inhibitory effect of YB9 against S.s. was further verified by scanning electron microscopy, fluorescence microscopy, cell membrane permeability, cell content leakage, and malondialdehyde content.

Pyriofenone Interacts with the Major Facilitator Superfamily Transporter of Phytopathogenic Fungi to Potentially Control Tea Leaf Spot Caused by Lasiodiplodia theobromae.

Tea leaf spot caused by Lasiodiplodia theobromae is a newly discovered fungal disease in southwest China. Due to a lack of knowledge of its epidemiology and control strategies, the disease has a marked impact on tea yield and quality. Pyriofenone is a new fungicide belonging to the aryl phenyl ketone fungicide group, which has shown marked efficacy in controlling various fungal diseases. However, its mechanism of action is not yet understood. This study found that pyriofenone exhibits strong in vitro inhibitory activity against various phytopathogenic fungi. Specifically, it showed strong inhibitory activity against L. theobromae, with a half-maximal effective concentration (EC50) value of 0.428 μg/ml determined by measuring mycelial growth rate. Morphological observations, using optical, scanning electron, and transmission electron microscopy, revealed that pyriofenone induces morphological abnormalities in L. theobromae hyphae. At lower doses, the hyphae became swollen, the distance between septa decreased, and the hyphal growth rate slowed. At higher doses and longer exposures, the hyphae collapsed. Transcriptomic and bioinformatic analyses indicated that pyriofenone can affect the expression of genes related to membrane transporters. Homology modeling suggested that pyriofenone may bind to a candidate target protein of the major facilitator superfamily (MFS) transporter, with a free binding energy of -7.1 kcal/mol. This study suggests that pyriofenone may potentially regulate the transport of metabolites in L. theobromae, thus affecting hyphal metabolism and interfering with hyphal growth. Pyriofenone exhibits in vitro inhibitory activity against various tea foliar pathogens and holds promise for future applications to the control of tea foliar diseases.