Discovery of zeylenone from Uvaria grandiflora as a potential botanical fungicide

Discovery and Development of Luvangetin from Zanthoxylum avicennae as a New Fungicide Candidate for Fusarium verticillioides

Pathogenic fungi pose a significant threat to crop yields and human healthy, and the subsequent fungicide resistance has greatly aggravated these agricultural and medical challenges. Hence, the development of new fungicides with higher efficiency and greater environmental friendliness is urgently required. In this study, luvangetin, isolated and identified from the root of Zanthoxylum avicennae, exhibited wide-spectrum antifungal activity in vivo and in vitro. Integrated omics and in vitro and in vivo transcriptional analyses revealed that luvangetin inhibited GAL4-like Zn(II)2Cys6 transcriptional factor-mediated transcription, particularly the FvFUM21-mediated FUM cluster gene expression, and decreased the biosynthesis of fumonisins inFusarium verticillioides. Moreover, luvangetin binds to the double-stranded DNA helix in vitro in the groove mode. We isolated and identified luvangetin, a natural metabolite from a traditional Chinese edible medicinal plant and uncovered its multipathogen resistance mechanism. This study is the first to reveal the mechanism underlying the antifungal activity of luvangetin and provides a promising direction for the future use of plant-derived natural products to prevent and control plant and animal pathogenic fungi.

Synthesis of Acrylopimaric Acid Triazole Derivatives and Their Antioomycete Activity against Phytophthora capsici

To develop new antioomycete agents against plant pathogens, two series of acrylopimaric acid triazole derivatives from rosin were synthesized. The in vitro antioomycete activity of these derivatives was evaluated and screened against Pseudoperonospora cubensisi, Plasmopara viticola, Phytophthora sojae, Phytophthora infestans, and Phytophthora capsici. Compound 5m showed the highest antioomycete activity against P. capsici, with a half-maximal effective concentration (EC50) value that was lower than that of the positive control metalaxyl (1.391 and 1.815 mg/L, respectively). Compound 5m demonstrated satisfactory protective and curative efficacy against P. capsici in pepper in in vivo antioomycete activity studies. Physiological and biochemical testing showed that the action mechanism of compound 5m on P. capsici involved altering the morphology and ultrastructure of the mycelium, increasing cell membrane permeability, inducing dysfunction of the nucleus and mitochondria, and ultimately causing cell necrosis. In addition, the analysis of three-dimensional quantitative structure-activity relationship (3D-QSAR) revealed the significance of the molecular structure and charge distribution in the interaction between compound 5m and its target. Collectively, these findings indicate that compound 5m has the potential as an antioomycete candidate.

Cyclohexene oxide CA, a derivative of zeylenone, exhibits anti-cancer activity in glioblastoma by inducing G0/G1 phase arrest through interference with EZH2

Introduction: Due to its highly aggressiveness and malignancy, glioblastoma (GBM) urgently requires a safe and effective treatment strategy. Zeylenone, a natural polyoxygenated cyclohexenes compound isolated from Uvaria grandiflora, has exhibited potential biological activities in various human diseases, including tumors. Methods: We designed and synthesized a series of (+)-Zeylenone analogues and evaluated their anti-GBM roles through structural-activity analysis. Cell Counting Kit-8, TUNEL, transwell and flow cytometry were employed for investigating the anticancer effects of CA on GBM cells. Western blotting, molecular docking, qRT-PCR and ChIP assays were performed to reveal the underlying mechanisms by which CA regulates the GBM cell cycle. The nude mouse xenograft model, HE staining, immunohistochemistry and was used to evaluate the anticancer effect of CA in vivo. Results: We identified CA ((1R, 2R, 3S)-3-p-fluorobenzoyl-zeylenone) as having the lowest IC50 value in GBM cells. CA treatment significantly inhibited the malignant behaviors of GBM cells and induced G0/G1 phase arrest in vitro. Furthermore, we validated the molecular mechanism by which CA interferes with EZH2, attenuating the down-regulation of cyclin-dependent kinase inhibitors p27 and p16 by the PRC2 complex. By establishing orthotopic nude mice models, we further validated the inhibitory role of CA on tumorigenesis of GBM cells in vivo and its potential values to synergistically potentiate the anti-tumor effects of EZH2 inhibitors. Conclusion: Overall, this paper elucidated the anti-GBM effects and potential mechanisms of CA, and may provide a therapeutic drug candidate for GBM treatment.

Antifungal activity of Ligusticum chuanxiong essential oil and its active composition butylidenephthalide against Sclerotium rolfsii

BACKGROUND

Peanut stem rot caused by Sclerotium rolfsii is an epidemic disastrous soil-borne disease. Recently, natural products tend to be safe alternative antifungal agents to combat pathogens.

RESULTS

This work determined the preliminary antifungal activity of 29 essential oils against S. rolfsii and found that Ligusticum chuanxiong essential oil (LCEO) showed the best antifungal activity, with an EC50 value of 81.79 mg L-1 . Sixteen components (98.78%) were identified in LCEO by gas chromatography-mass spectrometry analysis, the majority by volume comprising five phthalides (93.14%). Among these five phthalides, butylidenephthalide was the most effective compound against S. rolfsii. Butylidenephthalide not only exhibited favorable in vitro antifungal activity against the mycelial growth, sclerotia production and germination of S. rolfsi, but also presented efficient in vivo efficacy in the control of peanut stem rot. Seven days after application in the glasshouse, the protective and curative efficacy of butylidenephthalide at 300 mg L-1 (52.02%, 44.88%) and LCEO at 1000 mg L-1 (49.60%, 44.29%) against S. rolfsii were similar to that of the reference fungicide polyoxin at 300 mg L-1 (54.61%, 48.28%). Butylidenephthalide also significantly decreased the oxalic acid and polygalacturonase content of S. rolfsii, suggesting a decreased infection ability on plants. Results of biochemical actions indicated that butylidenephthalide did not have any effect on the cell membrane integrity and permeability but significantly decreased nutrient contents, disrupted the mitochondrial membrane, inhibited energy metabolism and induced reactive oxygen species (ROS) accumulation of S. rolfsii.

CONCLUSION

Our results could provide an important reference for understanding the application potential and mechanisms of butylidenephthalide in the control of S. rolfsii. © 2023 Society of Chemical Industry.

A review of biocontrol agents in controlling late blight of potatoes and tomatoes caused by Phytophthora infestans and the underlying mechanisms

Phytophthora infestans causes late blight on potatoes and tomatoes, which has a significant economic impact on agriculture. The management of late blight has been largely dependent on the application of synthetic fungicides, which is not an ultimate solution for sustainable agriculture and environmental safety. Biocontrol strategies are expected to be alternative methods to the conventional chemicals in controlling plant diseases in the integrated pest management (IPM) programs. Well-studied biocontrol agents against Phytophthora infestans include fungi, oomycetes, bacteria, and compounds produced by these antagonists, in addition to certain bioactive metabolites produced by plants. Laboratory and glasshouse experiments suggest a potential for using biocontrol in practical late blight disease management. However, the transition of biocontrol to field applications is problematic for the moment, due to low and variable efficacies. In this review, we provide a comprehensive summary on these biocontrol strategies and the underlying corresponding mechanisms. To give a more intuitive understanding of the promising biocontrol agents against Phytophthora infestans in agricultural systems, we discuss the utilizations, modes of action and future potentials of these antagonists based on their taxonomic classifications. To achieve a goal of best possible results produced by biocontrol agents, it is suggested to work on field trials, strain modifications, formulations, regulations, and optimizations of application. Combined biocontrol agents having different modes of action or biological adaptation traits may be used to strengthen the biocontrol efficacy. More importantly, biological control agents should be applied in the coordination of other existing and forthcoming methods in the IPM programs. © 2023 Society of Chemical Industry.

Inhibitory Effect of Tea Saponin on Major Apple-Disease-Inducing Fungi

Plant secondary metabolites are well known for their biological functions in defending against pathogenic microorganisms. Tea saponin (TS), one type of secondary metabolite of the tea plant (Camellia sinensis), has been shown to be a valuable botanical pesticide. However, its antifungal activity in controlling the fungi Valsa mali, Botryosphaeria dothidea, and Alternaria alternata, which induce major diseases in apple (Malus domestica), has not been determined. In this study, we first determined that TS has higher inhibitory activity than catechins against the three types of fungi. We further utilized in vitro and in vivo assays to confirm that TS showed high antifungal activity against the three types of fungi, especially for V. mali and B. dothidea. In the in vivo assay, application of a 0.5% TS solution was able to restrain the fungus-induced necrotic area in detached apple leaves efficiently. Moreover, a greenhouse infection assay also confirmed that TS treatment significantly inhibited V. mali infection in leaves of apple seedlings. In addition, TS treatment activated plant immune responses by decreasing accumulation of reactive oxygen species and promoting the activity of pathogenesis-related proteins, including chitinase and β-1,3-glucanase. This indicated that TS might serve as a plant defense inducer to activate innate immunity to fight against fungal pathogen invasion. Therefore, our data indicated that TS might restrain fungal infection in two ways, by directly inhibiting the growth of fungi and by activating plant innate defense responses as a plant defense inducer.

Anti-inflammatory polyoxygenated cyclohexene derivatives from Uvaria macclurei

Two undescribed polyoxygenated seco-cyclohexene derivatives named macclureins A and B, and three undescribed polyoxygenated cyclohexene derivatives macclureins C-E, together with 15 known analogues were isolated from the twigs and leaves of Uvaria macclurei. Their structures were established by extensive spectroscopic and circular dichroism analyses. Macclurein C is a chlorinated polyoxygenated cyclohexene. All isolates were evaluated for their anti-inflammatory activities on NO generation in the LPS-stimulated RAW 264.7 cells. (-)-Zeylenone showed the most potent effect against NO production with the IC50 value of 20.18 μM. Meanwhile, (-)-zeylenone also decreased the mRNA expression of pro-inflammatory factors IFN-γ, iNOS, IL-6 and TNF-α via downregulating NF-κB signaling pathway. Further in vivo experiments using a mouse model of sepsis showed that (-)-zeylenone significantly alleviated sepsis severity by measuring weight, murine sepsis score, survival rate and the serum levels of pro-inflammatory factors TNF-α and IL-6.

Antifungal alkaloids from the branch-leaves of Clausena lansium Lour. Skeels (Rutaceae)

BACKGROUND

The rational utilization of botanical secondary metabolites is one of the strategies to reduce the application of chemical fungicides. The extensive biological activities of Clausena lansium indicate that it has the potential to develop botanical fungicides.

RESULTS

A systematic investigation on the antifungal alkaloids from C. lansium branch-leaves following bioassay-guided isolation was implemented. Sixteen alkaloids, including two new and nine known carbazole alkaloids, one known quinoline alkaloid and four known amides, were isolated. Compounds 4, 7, 12 and 14 showed strong antifungal activity on Phytophthora capsiciwith EC₅₀ values ranging from 50.67 to 70.82 μg mL^-1 . Compounds 1, 3, 8, 10, 11, 12 and 16 displayed different degrees of antifungal activity against Botryosphaeria dothidea with EC₅₀ values ranging from 54.18 to 129.83 μg mL^-1 . It was reported for the first time that these alkaloids had antifungal effects on P. capsici or B. dothidea, and their structure-activity relationships were further discussed systematically. Additionally, among all alkaloids, dictamine (12) had the strongest antifungal activities against P. capsici (EC₅₀  = 50.67 μg mL^-1 ) and B. dothidea (EC₅₀  = 54.18 μg mL^-1 ), and its physiological effects on P. capsici and B. dothidea also were further evaluated.

CONCLUSION

Capsicum lansium is a potential source of antifungal alkaloids, and C. lansium alkaloids had the potential as lead compounds of botanical fungicides in the development of new fungicides with novel action mechanism. © 2023 Society of Chemical Industry.

Genome Mining and Heterologous Expression Guided the Discovery of Antimicrobial Naphthocyclinones from Streptomyces eurocidicus CGMCC 4.1086

A type II polyketide synthase biosynthetic gene cluster (nap) was identified in Streptomyces eurocidicus CGMCC 4.1086 via genome mining. The heterologous expression of the cryptic nap gene cluster in Streptomyces albus J1074 generated dimerized aromatic polyketide naphthocyclinones (1-3), whose structures were determined via extensive analysis using nuclear magnetic resonance and high-resolution electrospray ionization mass spectroscopy. The biological pathway of naphthocyclinone synthesis was revealed via in vivo gene deletion, in vitro biochemical reactions, and comparative genomics. Remarkably, 3 played a crucial role in inhibiting Phytophthora capsici and Phytophthora sojae, with EC₅₀ values of 6.1 and 20.2 μg/mL, respectively. Furthermore, 3 exhibited a potent protective effect against P. capsici and P. sojae in greenhouse tests.

Discovery of Tropolone Stipitaldehyde as a Potential Agent for Controlling Phytophthora Blight and Its Action Mechanism Research

The fermentation of endophytic Nigrospora chinensis GGY-3 resulted in the isolation of tropolone stipitaldehyde (1), which exhibited broad-spectrum inhibition activity against fungi and bacteria, especially against Phytophthora capsici, with an EC₅₀ value of 0.83 μg/mL and Xanthomonas oryzae pv. oryzicola, with a minimum inhibitory concentration value of 4.0 μg/mL. The in vitro and in vivo assays demonstrated that 1 had a significant protective effect on P. capsici. Furthermore, 1 inhibited the spore germination of P. capsici and damaged the plasma membrane structure. As observed by SEM and TEM, after exposure to 1, mycelia exhibited swelling, shrunken, branch-increasing phenomena, cell wall and membrane damage, and disordered content. Transcriptome analysis revealed that 1 might affect starch and sucrose metabolism and fatty acid biosynthesis by suppressing the expression of genes relevant to cell wall synthetases and cell membrane-associated genes. These findings indicate that 1 may be a potential agrochemical fungicide for controlling phytophthora blight.