Novel Design of Citral-Thiourea Derivatives for Enhancing Antifungal Potential against Colletotrichum gloeosporioides

Discovery of Potential Antifungal Agents: Chalcone Derivatives Containing Thiourea and Piperidine Moieties

Twenty-two chalcone derivatives containing thiourea and piperidine moieties were synthesized. The in vitro antifungal activities of these compounds against nine fungi were evaluated. The results demonstrated that a majority of these compounds exhibited exceptional antifungal activities. Especially, K2 displayed the most potent fungicidal activity against Phytophthora capsici (P. capsici), with a half-effective concentration (EC50) of 5.96 μg/mL, surpassing that of the control drug azoxystrobin (Az, 25.2 μg/mL). The in vivo antifungal experiments of K2 were conducted on pepper leaves and fruits. It exhibited significant protective efficacy against P. capsici in pepper leaves (95.3%) at 200 μg/mL, which surpassed that of Az (79.0%). Morphological investigations utilizing scanning electron microscopy (SEM) and fluorescence microscopy (FM) unveiled the disruptive impact of K2 on P. capsici mycelium. Moreover, mechanistic studies have demonstrated that K2 exhibited the capacity to disrupt the integrity of the cellular membrane in pathogenic fungi, influence lipid peroxidation processes within the membrane, and induce cellular content release. These experimental findings provided a new idea for effectively preventing plant fungal diseases and developing novel green chemical pesticide products.

Thiourea Derivatives in Agrochemical Discovery and Development

Thiourea, represented by the chemical formula (R1R2N)(R3R4N)C═S, is a significant organic sulfur compound characterized by the presence of a sulfur atom and two amino groups. Meanwhile, thiourea and isothiourea are reciprocal isomers. This structure facilitates the formation of a biologically active moiety, which is interconnected through double bonds between the sulfur atom and the nitrogen atoms. As a potent component in pesticide formulations, thiourea demonstrates efficacy in safeguarding crops against a variety of diseases by inhibiting the growth and reproduction of pathogens. This review aims to provide a comprehensive summary of thiourea derivatives exhibiting fungicidal, insecticidal, antiviral, herbicidal, and plant growth regulatory properties, with the objective of offering new perspectives for identifying innovative thiourea-based pesticides and elucidating their mechanisms of action.

Biological Activity of Monoterpene-Based Scaffolds: A Natural Toolbox for Drug Discovery

One of the most common strategies used in drug design is the molecular scaffold approach, which combines traditional medicine based on natural active compounds derived from plants with modern synthetic drug development. Designing new compounds based on natural skeletons enables extensive modifications of both bioavailability and biological activity. An excellent example of a natural molecular scaffold is the monoterpenes group, which serves as a core structure for building more complex molecules by attaching various chemical groups. Their ability to interact with biological targets, combined with structural versatility, makes them promising molecular scaffolds in pharmaceutical research and green chemistry applications. This review paper focuses on selected monoterpenes (carvacrol, carvone, citral, menthol, menthone, β-pinene, thymol, and verbenone), which are frequently used as molecular scaffolds. The newly designed derivatives exhibit various biological activities, including anticancer, antibacterial, antiviral, neuroprotective, and many others.

Design, Synthesis, and Antifungal Evaluation of Novel Cuminic Acid Derivatives as Potential Laccase Inhibitors

In search of novel natural product-based fungicides, 49 cuminic acid derivatives were designed, synthesized, and screened for their in vitro antifungal effects toward seven phytopathogenic fungi and oomycetes. Consequently, several derivatives exhibited strong antifungal activities toward Fusarium graminearum, Botryosphaeria dothidea, and Valsa mali. Among them, compound 2b exhibited the most potent antifungal activity toward B. dothidea (EC50 = 0.96 mg/L), more powerful than chlorothalonil. The in vivo assay against B. dothidea found that the protective and curative effects of 2b were comparable to chlorothalonil. Meanwhile, SEM and TEM observations indicated that 2b could ruin the integrity of mycelial morphology and organelles of B. dothidea. Preliminary mechanism research showed that 2b increased the cell membrane permeability and intracellular ROS level, as well as conspicuously decreased the mycelial dry weight and cell wall chitin contents of B. dothidea. The phytotoxicity test revealed that 2b showed good safety on seeds of mung bean and radish. The in vitro laccase inhibitory activity assay and molecular docking study demonstrated that 2b could be a promising laccase inhibitor. This type of cuminic acid hydrazide derivative would provide valuable inspiration for developing novel fungicides against B. dothidea.

Novel Essential Oil-Based Thiosemicarbazone Compounds as Potential Fungicides in Controlling Postharvest Diseases of Citrus Fruit

To develop novel fungicides for controlling postharvest fungal diseases in citrus fruits, 12 essential oil (EO)-based thiosemicarbazones compounds, termed hydrazine-carbothioamide, were prepared according to the condensation method. In vitro assays showed that compound 13j exhibited the strongest antifungal activity (minimum inhibitory concentration [MIC] = minimum fungicidal concentration [MFC] = 0.0125 mg/mL) against Penicillium digitatum. An in vivo study revealed that 5 × MFC of compound 13j can effectively mitigate the green mold incidence of citrus fruit inoculated with P. digitatum, as well as fruit rot during natural storage, at a level comparable to that of the chemical fungicide prochloraz. Throughout this process, fruit quality was maintained. The hemolysis assay showed that these thiosemicarbazone compounds have good biocompatibility and that their safety is comparable to that of prochloraz. The antifungal activity of compound 13j was attributed to membrane damage, as confirmed using scanning electron microscopy (SEM), Calcofluor white (CFW) staining, propidium iodide (PI) staining, Fourier transform-infrared (FT-IR) spectroscopy, optical density (OD)260, and relative conductivity assays. Collectively, our results indicate that compound 13j can be used as an antifungal agent to control the postharvest decay of citrus fruits.

Pinonic Acid Derivatives Containing Thiourea Motif: Promising Antifungal Lead Compound Targeting Cellular Barrier of Colletotrichum fructicola

In order to explore novel antifungal lead compounds from plant essential oil, thirty-two pinonic acid derivatives containing thiourea groups were designed and synthesized using α-pinene as a raw material. One of these pinonic acid derivatives compound 3a exhibited noteworthy in vitro antifungal activity against Colletotrichum fructicola (EC50 = 9.22 mg/L), which was comparable to that of the positive control kresoxim-methyl (EC50 = 9.69 mg/L). Structure-activity relationship (SAR) studies demonstrated that the introduction of thiourea groups, F atoms, and Cl atoms into the structure of pinonic acid derivatives significantly improved their antifungal activity. The in vivo antifungal test revealed that compound 3a could effectively control pear anthracnose. It also proved that compound 3a showed low acute oral toxicity to honeybees (LD50 > 100 μg/bee) and low or no cytotoxicity to LO2 and HEK293 cell lines. The preliminary mechanism of action studies revealed that compound 3a caused mycelium deformity, increased cell membrane permeability, blocked the normal process of phospholipase C on the cell membrane, and reduced mycelium protein content. The results of molecular docking studies demonstrated the stable binding of compound 3a to phospholipase C and chitin synthetase. This study suggested that compound 3a could be used as a promising lead compound for the development of novel antifungal agents targeting the cellular barrier of C. fructicola.

Chitosan stabilized lemon essential oil nanoemulsion controls black mold rot and maintains quality of table grapes

Aspergillus carbonarius infection leads to black mold rot in table grapes, causes grape decay, reduces fruit quality and marketability, which produces significant economic losses. This study investigated the antifungal efficacy of chitosan-stabilized lemon essential oil nanoemulsion (LO-CNE) against A. carbonarius and black mold rot of table grapes. LO-CNE was prepared with a mean diameter of 130.01 ± 8.34 nm. LO-CNE exhibited superior antifungal activity, reduced spore germination and germ tube elongation, decreased the antioxidant enzyme activities in A. carbonarius; the minimal inhibitory concentration of LO-CNE was determined to be 30 mg/mL. LO-CNE reduced the occurrence of black mold rot by 63 % and lesion diameter by 56.78 % in table grapes compared to the control. At their peak activity level, the grapes treated with LO-CNE exhibited significantly enhanced antioxidant and defense-related enzyme activities. Specifically, polyphenol oxidase activity increased by 2.27-fold, peroxidase activity by 2.22-fold, superoxide dismutase activity by 0.68-fold, catalase activity by 1.61-fold, phenylalanine ammonia-lyase activity by 3.38-fold, and ascorbate peroxidase activity by 2.36-fold. The LO-CNE application reduced natural decay by 95 %, weight loss by 15 % compared to the control, and effectively maintained the quality parameters of table grapes. Therefore, LO-CNE can be considered an alternative disease-control agent for grape preservation.

Design, synthesis, antifungal evaluation and mechanism study of novel norbornene derivatives as potential laccase inhibitors

BACKGROUND

To discover novel fungicide candidates, five series of novel norbornene hydrazide, bishydrazide, oxadiazole, carboxamide and acylthiourea derivatives (2a-2t, 3a-3f, 4a-4f, 5a-5f and 7a-7f) were designed, synthesized and assayed for their antifungal activity toward seven representative plant fungal pathogens.

RESULTS

In the in vitro antifungal assay, some title norbornene derivatives presented good antifungal activity against Botryosphaeria dothidea, Sclerotinia sclerotiorum and Fusarium graminearum. Especially, compound 2b exhibited the best inhibitory activity toward B. dothidea with the median effective concentration (EC50) of 0.17 mg L-1, substantially stronger than those of the reference fungicides boscalid and carbendazim. The in vivo antifungal assay on apples revealed that 2b had significant curative and protective effects, both of which were superior to boscalid. In the preliminary antifungal mechanism study, 2b was able to injure the surface morphology of hyphae, destroy the cell membrane integrity and increase the intracellular reactive oxygen species (ROS) level of B. dothidea. In addition, 2b could considerably inhibit the laccase activity with the median inhibitory concentration (IC50) of 1.02 μM, much stronger than that of positive control cysteine (IC50 = 35.50 μM). The binding affinity and interaction mode of 2b with laccase were also confirmed by molecular docking.

CONCLUSION

This study presented a promising lead compound for the study of novel laccase inhibitors as fungicidal agrochemicals, which demonstrate significant anti-B. dothidea activity and laccase inhibitory activity. © 2024 Society of Chemical Industry.

Exploring the latest trends in chemistry, structure, coordination, and diverse applications of 1-acyl-3-substituted thioureas: a comprehensive review

Acyl thioureas represent a privileged moiety with vast potential applicability across diverse fields, making them the subject of extensive research efforts. The inherent flexibility of thiourea facilitates the synthesis of a wide range of core structures with diverse functionalities and properties. The distinctive presence of hard and soft donor sites renders acyl thioureas inclined to act as versatile ligands, thereby engendering a diverse array of metal complexes incorporating acyl thiourea as a pivotal ligand. Extensive investigations into the synthesized acyl thioureas and their derivatives have culminated in the elucidation of their substantial potential across a spectrum of applications, spanning biological activities, materials chemistry, catalysis, and beyond. This literature review represents a continuation of our ongoing endeavor to compile comprehensive data on research endeavors concerning acyl thioureas over the past two years.

Screening for a Fenpropidin Enantiomer with High Activity and Low Toxicity

Fenpropidin has been extensively used for managing fungal diseases in different crops. There is a lack of literature on the enantioselective bioactivity and toxicity of fenpropidin. This study aims to explore the enantioselective bioactivity and toxicity of fenpropidin. R-Fenpropidin exhibited more potent bioactivity against seven plant pathogens than S-fenpropidin. R-Fenpropidin was more effective than S-fenpropidin in inhibiting sclerotial production, affecting mycelial growth and morphology, increasing cell membrane permeability, and decreasing the ergosterol content of Rhizoctonia solani. R-Fenpropidin exhibited a tighter binding affinity and formed hydrogen bonds with two target proteins. Fenpropidin also has enantioselective toxicity to Selenastrum capricornutum, with the toxicity of S-fenpropidin being seven times that of R-fenpropidin. S-Fenpropidin significantly reduced the content of the photosynthetic pigments. The results showed that R-fenpropidin was a highly active enantiomer with low toxicity. This study can provide a basis for the development of enantiomers with high activity and low toxicity.