Design, synthesis and fungicidal evaluation of novel psoralen derivatives containing sulfonohydrazide or acylthiourea moiety.

To search a novel lead structure for antiphytopathogenic fungus agent, a series of novel psoralen derivatives possessing sulfonohydrazide or acylthiourea structure were designed and synthesized, and their fungicidal activity against seven phytopathogens was evaluated. Their structures were confirmed by melting points, 1H NMR, 13C NMR and HRMS, and the typical crystal structure was determined by X-ray diffraction for validation. Preliminary fungicidal activity showed that some of the title compounds exhibited certain-to-high fungicidal activity. Compound I-13 exhibited good fungicidal activity against Botrytis cinerea, Cercospora arachidicola and Physalospora piricola with EC50 values of 12.49, 13.22 and 12.12 µg/mL, respectively. Compounds II-9 and II-15 showed over 90% inhibition against B. cinerea at 50 µg/mL in vitro. In particular, II-9 exhibited significant higher fungicidal activity with a lower EC50 value of 9.09 µg/mL than the positive control YZK-C22 (13.41 µg/mL). Our studies found that sulfonohydrazide or acylthiourea-containing psoralen derivatives were promising fungicide leads deserve for further study.

Design, Synthesis and Fungicidal Activity of Ester Derivatives of 4-(3,4-Dichloroisothiazole) 7-Hydroxy Coumarin.

The development of new fungicides is vital for safeguarding crops and ensuring sustainable agriculture. Building on our previous finding that 4-(3,4-dichloroisothiazole)-7-hydroxy coumarins can be used as fungicidal leads, 44 novel coumarin ester derivatives were designed and synthesized to evaluate whether esterification could enhance their fungicidal activity. In vitro fungicidal bioassays indicated that compound 2ai displayed good activity against Alternaria solani, Botrytis cinereal, Cercospora arachidicola, Physalospora piricola and Sclerotinia sclerotiorum, with an EC50 value ranging from 2.90 to 5.56 µg/mL, comparable to the lead compound 1a, with its EC50 value ranging from 1.92 to 9.37 µg/mL. In vivo bioassays demonstrated that compounds 1a, 2ar and 2bg showed comparable, excellent efficacy against Pseudoperonospora cubensis at a dose of 25 µg/mL. Our research shows that the esterification of 4-(3,4-dichloroisothiazole) 7-hydroxycoumarins results in a fungicidal activity equivalent to that of its lead compounds. Furthermore, our density functional theory (DFT) calculations and 3D-QSAR modeling provide a rational explanation of the structure-activity relationship and offer valuable insights to guide further molecular design.

Improvement of Carotenoids' Production by Increasing the Activity of Beta-Carotene Ketolase with Different Strategies.

Canthaxanthin is an important antioxidant with wide application prospects, and ß-carotene ketolase is the key enzyme involved in the biosynthesis of canthaxanthin. However, the challenge for the soluble expression of ß-carotene ketolase is that it hinders the large-scale production of carotenoids such as canthaxanthin and astaxanthin. Hence, this study employed several strategies aiming to improve the soluble expression of ß-carotene ketolase and its activity, including selecting optimal expression vectors, screening induction temperatures, adding soluble expression tags, and adding a molecular chaperone. Results showed that all these strategies can improve the soluble expression and activity of ß-carotene ketolase in Escherichia coli. In particular, the production of soluble ß-carotene ketolase was increased 8 times, with a commercial molecular chaperon of pG-KJE8, leading to a 1.16-fold enhancement in the canthaxanthin production from ß-carotene. Interestingly, pG-KJE8 could also enhance the soluble expression of ß-carotene ketolase derived from eukaryotic microalgae. Further research showed that the production of canthaxanthin and echinenone was significantly improved by as many as 30.77 times when the pG-KJE8 was added, indicating the molecular chaperone performed differently among different ß-carotene ketolase. This study not only laid a foundation for further research on the improvement of ß-carotene ketolase activity but also provided new ideas for the improvement of carotenoid production.

Computation-Directed Molecular Design, Synthesis, and Fungicidal Activity of Succinate Dehydrogenase Inhibitors.

Succinate dehydrogenase inhibitors (SDHIs) are a class of fungicides targeting the pathogenic fungi mitochondrial SDH. Here, molecular docking, three-dimensional quantitative structure-activity relationship (3D-QSAR), and molecular dynamics (MD) simulations were used to guide SDHI innovation. Molecular docking was performed to explore the binding modes of SDH and its inhibitors. 3D-QSAR models were carried out on 33 compounds with activity against Rhizoctonia cerealis (R. cerealis); their structure-activity relationships were analyzed using comparative molecular field analysis and comparative molecular similarity indices analysis. MD simulations were used to assess the stability of the complexes under physiological conditions, and the results were consistent with molecular docking. Binding free energy was calculated through the molecular mechanics generalized born surface area method, and the binding free energy was decomposed. The results are consistent with the activity of bioassay and indicate that van der Waals and lipophilic interactions contribute the most in the molecular binding process. Afterward, we designed and synthesized 12 compounds under the guidance of the above-mentioned analyses, bioassay found that F9 was active against R. cerealis with the EC50 value of 9.43 µg/mL, and F4, F5, and F9 were active against Botrytis cinerea with an EC50 values of 5.80, 3.17, and 1.63 µg/mL, respectively. They all showed good activity between positive controls of pydiflumetofen and thifluzamide. Our study provides new considerations for effective SDHIs discovery.

3D-QSAR Combination with Molecular Dynamics Simulations to Effectively Design the Active Ryanodine Receptor Agonists against Spodoptera frugiperda.

Computer-aided molecular modeling was applied to design a series of Spodoptera frugiperda RyR agonists. Comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) were used to generate 3D-QSAR models. MD simulations in the complex with S. frugiperda native, mutant RyR, and mammalian RyR1 under physiological conditions were used to validate the detailed binding mechanism. Binding free energy calculation by molecular mechanics generalized surface area (MM-GBSA) explained the role of key amino acid residues in ligand-receptor binding. Therefore, 14 new compounds were effectively designed and synthesized, and a bioassay indicated that compounds A-2 and A-3 showed comparable activity to that of chloranthraniliprole with LC50 values of 0.27, 0.18, and 0.20 mg L-1, respectively, against S. frugiperda. Most target compounds also displayed good activity against Mythinma separata at 0.1 mg L-1. Molecular docking and MM-GBSA calculations demonstrated that A-3 had a better binding capacity with native and mutant S. frugiperda RyRs.

Design, Synthesis, and Biological Evaluation of Novel Psoralen-Based 1,3,4-Oxadiazoles as Potent Fungicide Candidates Targeting Pyruvate Kinase.

Pyruvate kinase (PK) has been considered as a promising fungicide target discovered in our previous studies. Natural compounds are important sources for discovery and development of new pesticides. To continue our ongoing studies on the discovery of novel PK-targeted fungicides, a series of novel psoralen derivatives including a 1,3,4-oxadiazole moiety were designed by a computer-aided pesticide molecular design method, synthesized, and evaluated for their fungicidal activity. The bioassay results indicated that compounds 11d, 11e, 11g, 11i, and 12a showed excellent in vitro fungicidal activity against Botrytis cinerea with EC50 values of 4.8, 3.3, 6.3, 5.4, and 3.9 µg/mL, respectively. They were more active than the corresponding positive control YZK-C22 [3-(4-methyl-1,2,3-thiadiazol-5-yl)-6-(trichloromethyl)-[1,2,4]-triazolo-[3,4-b][1,3,4]-thiadiazole] (with an EC50 value of 13.4 µg/mL). Compounds 11g and 11i displayed promising in vivo fungicidal activity against B. cinerea with 80 and 70% inhibition at a concentration of 200 µg/mL, respectively. They possessed much higher fungicidal activity than the positive control psoralen and comparable activity with the positive control pyrisoxazole. Enzymatic assays indicated that 11i showed good BcPK inhibition with an IC50 value of 39.6 µmol/L, comparable to the positive control YZK-C22 (32.4 µmol/L). Molecular docking provided a possible binding mode of 11i in the BcPK active site. Our studies suggested that the psoralen-based 1,3,4-oxadiazole 11i could be used as a new fungicidal lead targeting PK for further structural optimization.