Biological and Chemical Control of Sclerotinia sclerotiorum using Stachybotrys levispora and Its Secondary Metabolite Griseofulvin

Integrating morphology, physiology, and computer simulation to reveal the toxicity mechanism of eco-friendly rosin-based pesticides

To mitigate the impact of traditional chemical pesticides on environment, and achieve sustainable crop protection, 24 eco-friendly rosin-based sulfonamide derivatives were synthesized and developed. The in vitro activity assessment showed that compound 4X (Co. 4X) exhibited excellent fungicidal activity against V. mali (EC50 = 1.106 μg/mL), marginally surpassing the positive control carbendazim (EC50 = 1.353 μg/mL). In vivo investigations suggested that Co. 4X exhibited moderate efficacy in mitigating V. mali infection in both apple trees and apples. Physiological assessments revealed that Co. 4X induced severe ultrastructural damage to the mycelium, heightened cell membrane permeability, and inhibited SDH protein activity. Subsequent biosafety evaluations affirmed the environment-friendly of Co. 4X on Zebrafish (LC50(96h) = 25.176 μg/mL). Toxicological research revealed that Co. 4X caused damage to the cells of Zebrafish gills, liver, and intestines, resulting in impaired respiratory, detoxification, digestion, and absorption functions of Zebrafish. In summary, the findings of this study contribute to a deeper understanding of the toxicity mechanisms of novel pesticides, decreasing environmental risks caused by traditional chemical pesticides, and improving the effective management of novel pesticide applications.

Design, synthesis and biological activity evaluation of eco-friendly rosin-based fungicides for sustainable crop protection

BACKGROUND

Utilizing fungicides to protect crops from diseases is an effective method, and novel eco-friendly plant-derived fungicides with high efficiency and low toxicity are urgent requirements for sustainable crop protection.

RESULT

Two series of rosin-based fungicides (totally 35) were designed and synthesized. In vitro fungicidal activity revealed that Compound 6a (Co. 6a) effectively inhibited the growth of Valsa mali [median effective concentration (EC50) = 0.627 μg mL-1], and in vivo fungicidal activity suggested a significant protective efficacy of Co. 6a in protecting both apple branches (35.12% to 75.20%) and apples (75.86% to 90.82%). Quantum chemical calculations (via density functional theory) results indicated that the primary active site of Co. 6a lies in its amide structure. Mycelial morphology and physiology were investigated to elucidate the mode-of-action of Co. 6a, and suggested that Co. 6a produced significant cell membrane damage, accelerated electrolyte leakage, decreased succinate dehydrogenase (SDH) protein activity, and impaired physiological and biochemical functions, culminating in mycelial mortality. Molecular docking analysis revealed a robust binding energy (ΔE = -7.29 kcal mol-1) between Co. 6a and SDH. Subsequently, biosafety evaluations confirmed the environmentally-friendly nature of Co. 6a via the zebrafish model, yet toxicological results indicated that Co. 6a at median lethal concentration [LC50(96)] damaged the gills, liver and intestines of zebrafish.

CONCLUSION

The above research offers a theoretical foundation for exploiting eco-friendly rosin-based fungicidal candidates in sustainable crop protection. © 2024 Society of Chemical Industry.

Antitumor properties of griseofulvin and its toxicity

Griseofulvin (GF), which is mainly extracted from Penicillium griseofulvum, is a heat-resistant, chlorine-containing non-polyene antifungal antibiotic. Previous research shows that GF has a variety of pharmacological effects, such as anti-inflammatory, antifungal, antiviral, and antitumor effects. In recent years, GF has received extensive attention for its antitumor effects as a natural compound, offering a low price, a wide range of uses, and other beneficial characteristics. However, no comprehensive review of GF pharmacological activity in tumors has been published so far. In order to fully elucidate the antitumor activities of GF, this review focuses on the antitumor potential and toxicity of GF and its derivatives, based on a literature search using PubMed, Web of Science, and other databases, to lay a good foundation for further research of GF and the development of new drugs for antitumor activities.

Discovery of novel natural cardiomyocyte protectants from a toxigenic fungus Stachybotrys chartarum

Stachybatranones A-F (1a/1b and 2-6) and three known analogues, namely methylatranones A and B (7 and 8) and atranone B (9), were isolated and identified from a toxigenic fungus Stachybotrys chartarum. Their structures and absolute configurations were elucidated via the extensive spectroscopic data, comparison of the experimental electronic circular dichroism (ECD) data, and single-crystal X-ray diffraction analyses. Structurally, compounds 2-6 belonged to a rare class of C-alkylated dolabellanes, featuring a unique five-membered hemiketal ring and a γ-butyrolactone moiety both fused to an 11-membered carbocyclic system, while compound 1 (1a/1b) represented the first example of a 5-11-6-fused atranone possessing a 2,3-butanediol moiety. The cardiomyocyte protective activity assay revealed that compounds 1-9 ameliorated cold ischemic injury at 24 h post cold ischemia (CI), with compounds 1 and 4 acting in a dose-dependent manner. Moreover, compound 1 prevented cold ischemia induced dephosphorylation of PI3K and AKT acting in a dose-dependent manner. In this study, a new class of natural products were found to protect cardiomyocytes against cold ischemic injury, providing a potential option for the development of novel cardioprotectants in heart transplant medicine.

Discovery of Potential Rosin-Based Triazole Antifungal Candidates to Control Valsa mali for Sustainable Crop Protection

To investigate the potential application value of dehydroabietic acid, 27 novel dehydroabietyl-1,2,4-triazole-5-thioether-based derivatives were designed and characterized by IR, 1H NMR, 13C NMR, and LC-MS. Their antifungal activities were evaluated against five plant fungi, namely, Valsa mali, Colletotrichum orbiculare, Fusarium graminearum, Sclerotinia sclerotiorum, and Gaeumannomyces graminis; the results showed that compound 5h-1 (Co. 5h-1) exhibited a considerable inhibitory effect against V. mali. Moreover, in vivo experiments indicated that Co. 5h-1 had a certain protective effect on apple branches. The preliminary structure-activity relationship analysis suggested that the electron-withdrawing group on the benzyl group was significantly better than that of other substituent derivatives. Through electron microscopy analysis, it was found that Co. 5h-1 hindered the growth of mycelia, damaged their cell structure, and caused the large accumulation of reactive oxygen species (ROS). Preliminary research on the mode of action indicated that Co. 5h-1 could affect the activity of CAT by increasing the α-helix (0.790%), decreasing the β-sheet (0.170%), which led to the accumulation of ROS. In addition, Co. 5h-1 also affected the activity of CYP51, hindered the biosynthesis of ergosterol, and increased cell membrane permeability. Overall, this above research proposed that Co. 5h-1 can be a novel leading structure for development of a fungicide agent.

Lewis Acid-Catalyzed Benzannulation of Vinyloxiranes with 3-Formylchromones or 1,4-Quinones for Diversely Functionalized 2-Hydroxybenzophenones, 1,4-Naphthoquinones, and Anthraquinones

A facile and convenient protocol for the regioselective construction of functionalized 2-hydroxybenzophenones is described. This protocol involves the Sc(OTf)3/BF3·OEt2-catalyzed benzannulation of 2-vinyloxirans with 3-formylchromone, which involves cascade in situ diene formation, [4 + 2] cycloaddition, elimination, and ring-opening strategies. Moreover, it provides an expedited synthetic pathway to access biologically intriguing 1,4-naphthoquinones and anthraquinones including vitamin K3 and tectoquinone. The synthesized compounds also hold potential for use as UV filters and show promise as chemosensors for Cu2+ and Mg2+ ions.

Design and Synthesis of Antifungal Candidates Containing Triazole Scaffold from Natural Rosin against Valsa mali for Crop Protection

Two series of dehydroabietyl-1,2,4-triazole-4-Schiff-based derivatives were synthesized from rosin to control plant fungal diseases. In vitro evaluation and screening of the antifungal activity were performed using Valsa mali, Colletotrichum orbiculare, Fusarium graminearum, Sclerotinia sclerotiorum, and Gaeumannomyces graminis. Compound 3f showed excellent fungicidal activity against V. mali (EC₅₀ = 0.537 μg/mL), which was significantly more effective than the positive control fluconazole (EC₅₀ = 4.707 μg/mL). Compound 3f also had a considerable protective effect against V. mali (61.57%-92.16%), which was slightly lower than that of fluconazole (85.17-100%) at 25-100 μg/mL. Through physiological and biochemical analyses, the preliminary mode of action of compound 3f against V. mali was explored. Ultrastructural observation of mycelia showed that compound 3f hindered the growth of the mycelium and destroyed the ultrastructure of V. mali seriously. Conductivity analysis and laser scanning confocal microscope staining showed that compound 3f changed cell-membrane permeability and caused accumulation of reactive oxygen species. The enzyme activity results showed that compound 3f significantly inhibited the activity of CYP51 (59.70%), SOD (76.9%), and CAT (67.86%). Molecular docking identified strong interaction energy between compound 3f and crystal structures of CYP51 (-11.18 kcal/mol), SOD (-9.25 kcal/mol), and CAT (-8.79 kcal/mol). These results provide guidance for the discovery of natural product-based antifungal pesticide candidates.

In Silico Exploration of Microtubule Agent Griseofulvin and Its Derivatives Interactions with Different Human β-Tubulin Isotypes

Tubulin isotypes are known to regulate microtubule stability and dynamics, as well as to play a role in the development of resistance to microtubule-targeted cancer drugs. Griseofulvin is known to disrupt cell microtubule dynamics and cause cell death in cancer cells through binding to tubulin protein at the taxol site. However, the detailed binding mode involved molecular interactions, and binding affinities with different human β-tubulin isotypes are not well understood. Here, the binding affinities of human β-tubulin isotypes with griseofulvin and its derivatives were investigated using molecular docking, molecular dynamics simulation, and binding energy calculations. Multiple sequence analysis shows that the amino acid sequences are different in the griseofulvin binding pocket of βI isotypes. However, no differences were observed at the griseofulvin binding pocket of other β-tubulin isotypes. Our molecular docking results show the favorable interaction and significant affinity of griseofulvin and its derivatives toward human β-tubulin isotypes. Further, molecular dynamics simulation results show the structural stability of most β-tubulin isotypes upon binding to the G1 derivative. Taxol is an effective drug in breast cancer, but resistance to it is known. Modern anticancer treatments use a combination of multiple drugs to alleviate the problem of cancer cells resistance to chemotherapy. Our study provides a significant understanding of the involved molecular interactions of griseofulvin and its derivatives with β-tubulin isotypes, which may help to design potent griseofulvin analogues for specific tubulin isotypes in multidrug-resistance cancer cells in future.

Polyketides with antimicrobial activities from Penicillium canescens DJJ-1

Two undescribed polyketides canecines A-B, one unreported cyclopentenone canecine C, together with 12 known compounds were isolated from an extract of the fungus Penicillium canescens DJJ-1. Their structures were elucidated by detailed analysis of spectroscopic data, NMR calculations with dJ-DP4 or DP4+, and their absolute configurations were further determined by quantum chemical calculations of ECD spectra or X-crystallography. Canecine A was a grisan polyketide featuring a dimethyltetrahydro-4H-furo[2,3-b]pyran. Canecine A exhibited significant inhibitory activity against Candida albicans with an MIC value of 1 μg/mL and showed inhibitory effect on nitric oxide production in LPS-activated RAW264.7 macrophages. These results enrich the structural diversities of polyketides from endophytic fungi.

Griseofulvin: An Updated Overview of Old and Current Knowledge

Griseofulvin is an antifungal polyketide metabolite produced mainly by ascomycetes. Since it was commercially introduced in 1959, griseofulvin has been used in treating dermatophyte infections. This fungistatic has gained increasing interest for multifunctional applications in the last decades due to its potential to disrupt mitosis and cell division in human cancer cells and arrest hepatitis C virus replication. In addition to these inhibitory effects, we and others found griseofulvin may enhance ACE2 function, contribute to vascular vasodilation, and improve capillary blood flow. Furthermore, molecular docking analysis revealed that griseofulvin and its derivatives have good binding potential with SARS-CoV-2 main protease, RNA-dependent RNA polymerase (RdRp), and spike protein receptor-binding domain (RBD), suggesting its inhibitory effects on SARS-CoV-2 entry and viral replication. These findings imply the repurposing potentials of the FDA-approved drug griseofulvin in designing and developing novel therapeutic interventions. In this review, we have summarized the available information from its discovery to recent progress in this growing field. Additionally, explored is the possible mechanism leading to rare hepatitis induced by griseofulvin. We found that griseofulvin and its metabolites, including 6-desmethylgriseofulvin (6-DMG) and 4- desmethylgriseofulvin (4-DMG), have favorable interactions with cytokeratin intermediate filament proteins (K8 and K18), ranging from -3.34 to -5.61 kcal mol-1. Therefore, they could be responsible for liver injury and Mallory body (MB) formation in hepatocytes of human, mouse, and rat treated with griseofulvin. Moreover, the stronger binding of griseofulvin to K18 in rodents than in human may explain the observed difference in the severity of hepatitis between rodents and human.

Antifungal Mechanism and Efficacy of Kojic Acid for the Control of Sclerotinia sclerotiorum in Soybean

Sclerotinia stem rot, which is caused by the fungal pathogen Sclerotinia sclerotiorum, is a soybean disease that results in enormous economic losses worldwide. The control of S. sclerotiorum is a difficult task due to the pathogen's wide host range and its persistent structures, called sclerotia. In addition, there is lack of soybean cultivars with medium to high levels of resistance to S. sclerotiorum. In this work, kojic acid (KA), a natural bioactive compound commonly used in cosmetic industry, was evaluated for the management of Sclerotinia stem rot. Interestingly, KA showed strong antifungal activity against S. sclerotiorum by inhibiting chitin and melanin syntheses and, subsequently, sclerotia formation. The antifungal activity of KA was not obviously affected by pH, but was reduced in the presence of metal ions. Treatment with KA reduced the content of virulence factor oxalic acid in S. sclerotiorum secretions. Preventive applications of 50 mM KA (7.1 mg/ml) completely inhibited S. sclerotiorum symptoms in soybean; whereas, in curative applications, the combination of KA with prochloraz and carbendazim improved the efficacy of these commercial fungicides. Taken together, the antifungal activity of KA against S. sclerotiorum was studied for the first time, revealing new insights on the potential application of KA for the control of Sclerotinia stem rot in soybean.

Impacts of the Biocontrol Strain Pseudomonas simiae PICF7 on the Banana Holobiont: Alteration of Root Microbial Co-occurrence Networks and Effect on Host Defense Responses

The impact of the versatile biocontrol and plant-growth-promoting rhizobacteria Pseudomonas simiae PICF7 on the banana holobiont under controlled conditions was investigated. We examine the fate of this biological control agent (BCA) upon introduction in the soil, the effect on the banana root microbiota, and the influence on specific host genetic defense responses. While the presence of strain PICF7 significantly altered neither the composition nor the structure of the root microbiota, a significant shift in microbial community interactions through co-occurrence network analysis was observed. Despite the fact that PICF7 did not constitute a keystone, the topology of this network was significantly modified-the BCA being identified as a constituent of one of the main network modules in bacterized plants. Gene expression analysis showed the early suppression of several systemic acquired resistance and induced systemic resistance (ISR) markers. This outcome occurred at the time in which the highest relative abundance of PICF7 was detected. The absence of major and permanent changes on the banana holobiont upon PICF7 introduction poses advantages regarding the use of this beneficial rhizobacteria under field conditions. Indeed a BCA able to control the target pathogen while altering as little as possible the natural host-associated microbiome should be a requisite when developing effective bio-inoculants.

Conservation of griseofulvin genes in the gsf gene cluster among fungal genomes

The polyketide griseofulvin is a natural antifungal compound and research in griseofulvin has been key in establishing our current understanding of polyketide biosynthesis. Nevertheless, the griseofulvin gsf biosynthetic gene cluster (BGC) remains poorly understood in most fungal species, including Penicillium griseofulvum where griseofulvin was first isolated. To elucidate essential genes involved in griseofulvin biosynthesis, we performed third-generation sequencing to obtain the genome of P. griseofulvum strain D-756. Furthermore, we gathered publicly available genome of 11 other fungal species in which gsf gene cluster was identified. In a comparative genome analysis, we annotated and compared the gsf BGC of all 12 fungal genomes. Our findings show no gene rearrangements at the gsf BGC. Furthermore, seven gsf genes are conserved by most genomes surveyed whereas the remaining six were poorly conserved. This study provides new insights into differences between gsf BGC and suggests that seven gsf genes are essential in griseofulvin production.

Elaborated regulation of griseofulvin biosynthesis in Penicillium griseofulvum and its role on conidiation and virulence

Penicilium griseofulvum, the causal agent of apple blue mold, is able to produce in vitro and on apple a broad spectrum of secondary metabolites (SM), including patulin, roquefortine C and griseofulvin. Among them, griseofulvin is known for its antifungal and antiproliferative activity, and has received interest in many sectors, from medicine to agriculture. The biosynthesis of SM is finely regulated by filamentous fungi and can involve global regulators and pathway specific regulators, which are usually encoded by genes present in the same gene cluster as the backbone gene and tailoring enzymes. In the griseofulvin gene cluster, two putative transcription factors were previously identified, encoded by genes gsfR1 and gsfR2, and their role has been investigated in the present work. Analysis of P. griseofulvum knockout mutants lacking either gene suggest that gsfR2 forms part of a different pathway and gsfR1 exhibits many spectra of action, acting as regulator of griseofulvin and patulin biosynthesis and influencing conidia production and virulence on apple. The analysis of gsfR1 promoter revealed that the regulation of griseofulvin biosynthesis is also controlled by global regulators in response to many environmental stimuli, such as carbon and nitrogen. The influence of carbon and nitrogen on griseofulvin production was further investigated and verified, revealing a complex network of response and confirming the central role of gsfR1 in many processes in P. griseofulvum.

Biocontrol effects of Penicillium griseofulvum against monkshood (Aconitum carmichaelii Debx.) root diseases caused by Sclerotium rolfsiii and Fusarium spp

AIMS

The aims of this study were to investigate the biocontrol effects of Penicillium griseofulvum strain CF3 and its mechanisms against soil-borne root pathogens (Fusarium oxysporum and Sclerotium rolfsii) of the medical plant Aconitum carmichaelii Debx.

METHODS AND RESULTS

The effects of P. griseofulvum strain CF3 were evaluated with regard to the hyphal growth of S. rolfsii and F. oxysporum, the sclerotial formation and germination of S. rolfsii and its expression of sclerotia-formation-related genes. A field experiment was conducted to explore how strain CF3 controls the severity of soil-borne diseases, promotes the growth of A. carmichaelii plants and mediates shifts in the culturable rhizosphere microbial populations. The results showed that treatment with a cell-free culture filtrate of strain CF3 considerably inhibited the hyphal growth of both S. rolfsii and F. oxysporum, in addition to limiting the sclerotial formation and germination of S. rolfsii. Three genes related to sclerotial formation (ArsclR, ArnsdD1 and ArnsdD2) were predicted in S. rolfsii and their expression was found suppressed by the CF3 treatment. Field application of the CF3 biocontrol agent in a powder form (1·9 × 10¹⁰ conidia per gram of substrate) reduced soil-borne disease severity by 15·0%. The shoot and root growth of A. carmichaelii plants was promoted by 61·6 and 83·1% respectively, as the biocontrol strain massively colonized the rhizosphere soil. The CF3 treatment also markedly reduced the density of some known species harmful to plants while increasing the density of some beneficial species in the rhizosphere soil.

SIGNIFICANCE AND IMPACT OF THE STUDY

Genes related to sclerotia formation of S. rolfsii are predicted for the first time and their expression patterns in the presence of P. griseofulvum strain CF3 are evaluated. This comprehensive study provides a candidate fungal biocontrol strain and reveals its potential mechanisms against S. rolfsii and F. oxysporum in A. carmichaelii plants.