Journal of Pesticide Science最新文献

A series of N-alkylated octopamine derivatives was synthesized, and the structure-activity relationships of these derivatives with the silkworm Bombyx mori octopamine receptor BmOAR1 were evaluated using a secreted placental alkaline phosphatase reporter assay system. The N-alkyl moiety on the ligand affected the intensity of the agonist activity in the order: CH₃>(H)>C₂H₅. Although linear alkyl chains of C3 or higher did not exhibit any activity, the fixed C3 alkyl group forming a pyrrolidine ring showed significant activity. These results suggest that BmOAR1 has a relatively small space around the amine-binding site, and the alkyl part constituting the cyclic amine could exert the same effect as the small alkyl group.

Flometoquin (FLO) is a novel quinoline-type insecticide that elicits a quick knock-down effect against target pests; however, its mode of action (MoA) remains unknown. In this study, we investigated its MoA systematically, using varying biochemical techniques. Since FLO-treated insects exhibited symptoms similar to those induced by respiratory inhibitors, we examined the effect of FLO on respiratory enzyme complexes using mitochondria isolated from different insects (housefly, diamondback moth, and western flower thrips). We found that FLO itself is not active; however, its deacylated metabolite, FloMet, specifically inhibits the activity of ubiquinol-cytochrome c oxidoreductase (complex III) in mitochondria at the nM level. Ligand binding assays and monitoring the reduction kinetics of cytochrome hemes b and c ₁ clearly revealed that FloMet inhibits complex III by binding to the Q_i site.

Our group previously identified MS-347a (1) as a new fungicide candidate from the culture broth of the mutant strain, Aspergillus sp. KTF-0058, which had the laeA gene inserted. This mutant strain was able to produce a sufficient supply of 1, allowing for its use to investigate the structure-activity relationship. To this end, we synthesized 11 derivatives and evaluated their antifungal activity. Among these derivatives, the aldehyde derivative exhibited superior antifungal potency as compared to 1, and some acyl derivatives were able to maintain the antifungal activity of 1 despite significant structural changes. From these results, it is found that the aldehyde derivative is one of the most promising fungicidal candidates, and the introduction of acyl groups could be utilized to create chemical probes for target-identification experiments.

The chemical synthesis of biologically active natural products has diverse objectives and missions, including 1) determining the structures of the natural products, 2) providing synthetic samples for studying the activity and function, 3) providing a basis for applied research on these compounds, etc. I have studied various biologically active natural products and conducted synthetic studies on these compounds with various objectives. In this review, I present the results of my research, focusing on natural products with potential as agrochemicals.

The enantiospecific anti-phytopathogenic fungal activity of a new type of coumarin bearing a phenylpropanoid unit at the 3-position was found. (S)-3-[1-Methoxy-3-(4-methoxyphenyl)prop-2-yl]coumarin ((S)-5: EC₅₀=16.5 µM) was 30 times more effective than the (R)-form against the Alternaria alternata Japanese pear pathotype. Derivatives bearing different substituents on the 7'-aromatic ring and the coumarin ring were synthesized to discover the more potent compounds. The 3'-CF₃ and 4'-CF₃ derivatives, 39 and 40, respectively, had the lowest EC₅₀ values (1-2 µM) in this project, suggesting that the size of the electron-withdrawing and hydrophobic substituents at these positions gave an advantage. On the coumarin ring, the presence of the OCH₃ or CH₃ group at the 5-position accelerated the activity, as the (4'-OCH₃, 5-OCH₃) derivative 41 and (4'-OCH₃, 5-CH₃) derivative 45 were, respectively, 4-5 times more potent than the 4'-OCH₃ derivative (S)-5.

The syntheses of stereoisomers of butane, butanediol, γ-butyrolactone, tri-substituted tetrahydrofuran (7,9'-epoxy), furofuran, tetra-substituted tetrahydrofuran (7,7'-epoxy and 7,8'-epoxy-8,7'-neolignan), benzylidene, coumarin, indan, and pyran type lignans were achieved. All the stereoisomers of the butane type lignans showed larvicidal activity and anti-phytopathogenic fungal activity. The γ-butyrolactone lignan showed stereospecific cytotoxicity against insect cells. Stereo/enantiospecific plant growth inhibitory activity was observed in tri-substituted tetrahydrofuran, tetra-substituted tetrahydrofuran (7,7'-epoxy), coumarin, and pyran type lignans. The furofuran lignan both inhibited and promoted growth in plants. Stereo/enantiospecific anti-phytopathogenic fungal activity was observed in tetra-substituted tetrahydrofuran (7,7'-epoxy) and E-benzylidene lignans.

The Cry1Fa insecticidal protein from Bacillus thuringiensis (Bt) was expressed on the surface of Bacillus subtilis (Bs) spores to create transgenic Bs spores referred to as Spore-Cry1Fa. Cry1Fa, along with its leader sequence, was connected to the carboxyl end of a Bs spore outercoat protein, CotC, through a flexible linker. The Arg-27 residue of the Cry1Fa protein was mutated to Leu to prevent detachment from the spores due to protease digestion. The expression of the Cry protein on the Bs spores was confirmed by fluorescence microscopy using an anti-Cry1Fa antibody. The Cry protein, tightly anchored to the spore surface, appeared to be functional in terms of receptor binding. Spore-Cry1Fa bound to Sf9 cells expressing Spodoptera frugiperda (Sf) ABCC2 transporter and killed the cells within 60 min. Additionally, nano-lipid particles of SfABCC2 were produced using styrene-maleic acid (SMA) to demonstrate the binding to Spore-Cry1Fa.

The biological properties of isofetamid, a new fungicide, were examined using pot tests in a greenhouse. In addition, we investigated the practical effects of isofetamid in field trials. In greenhouse pot tests, isofetamid exhibited high preventive efficacy against cucumber gray mold, powdery mildew, Corynespora leaf spot, and stem rot even at low concentrations. Isofetamid has excellent biological properties against cucumber gray mold and powdery mildew, such as rainfastness, residual activity, curative activity, translaminar activity, and transfer activity to undeveloped leaves, even at low concentrations. In field trials, isofetamid displayed high efficacy against tomato gray mold, cucumber powdery mildew, and lettuce stem rot. Therefore, the biological properties of isofetamid revealed in greenhouse tests contributed to its good performance in field trials.

The insecticide susceptibility of Helopeltis theivora Waterhouse (Hemiptera: Miridae) is being evaluated using shoot and glass-vial assay as described by IRAC. However, the reliability of the assay depends on feeding preference and contact toxicity. Hence, the cocoa pod was used as a substrate to test the susceptibility of H. theivora in comparison with existing methods. The experimental results revealed that the LC₅₀ value of all of the insecticides was relatively lower in the pod bioassay than the other two methods and exhibited maximum mortality within 6 hr of post-exposure. Among insecticides, fipronil was the most effective molecule followed by lambda-cyhalothrin. H. theivora, which prefers to feed on a pod due to more tissue turgidity, thus facilitated adequate sap ingestion; whereas, these were limited in shoot and glass-vial bioassays. Therefore, it could be used as a methodology to determine the susceptibility of H. theivora against a wide range of insecticide molecules.