Background: Taking into account the improvement in insecticidal activity by the inclusion of fluorine in the hydrazone moiety, the authors synthesized new 4-fluorobenzoic acid hydrazides and 3-acetyl-2,5-disubstituted-2,3-dihydro-1,3,4-oxadiazoles, substituting a phenyl group or a heteroaryl ring carrying one or two atoms of F, Cl and Br, and investigated their biting deterrent and larvicidal activities against Aedes aegypti for the first time.
Results: The compound 3-acetyl-5-(4-fluorophenyl)-2-[4-(dimethylamino)phenyl]-2,3-dihydro-1,3,4-oxadiazole (17) produced the highest biting deterrent activity (BDI = 1.025) against Ae. Aegypti, followed by 4-fluorobenzoic acid [(phenyl)methylene] hydrazide (1). These activity results were similar to those of N,N-diethyl-meta-toluamide (DEET), which showed a proportion not biting of 0.8-0.92. When compounds 1 and 17 were tested on cloth worn on human volunteers, compound 1 was not repellent for some volunteers until present in excess of 500 nmol cm(-2) , while compound 17 was not repellent at the highest concentration tested (1685 nmol cm(-2) ). In the larvicidal screening bioassays, only compounds 10, 11, 12 and 17 showed 100% mortality at the highest screening dose of 100 ppm against Ae. aegypti larvae. Compounds 11 and 12 with LD50 values of 24.1 and 30.9 ppm showed significantly higher mortality than 10 (80.3 ppm) and 17 (58.7 ppm) at 24-h post-treatment.
Conclusion: The insecticidal and biting deterrent activities were correlated with the presence of a halogen atom on the phenyl or heteroaryl substituent of the hydrazone moiety.
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Curr Biol
December 2024
School of Natural Sciences, Macquarie University, North Ryde, NSW 2109, Australia. Electronic address:
In the open ocean, achieving camouflage is complicated by the fact that the downwelling light is generally much brighter than the upwelling light, which means that any object, even if its ventral surface is white due to countershading, will appear as a dark silhouette when viewed from below. To overcome this, many marine species employ counterillumination, whereby light is emitted from photophores on their ventral surface to replace the downwelling light blocked by their body. However, only a single behavioral study has tested the efficacy of counterillumination as an anti-predation strategy.
View Article and Find Full Text PDFActa Trop
December 2024
National Center for Natural Products Research, The University of Mississippi, University, MS 38677, USA.
In our program of screening natural products against the pests of medical and veterinary importance, ethanolic extract of the roots of Ligusticum porteri J.M.Coult.
View Article and Find Full Text PDFSci Rep
July 2024
Southern Shark Ecology Group, College of Science and Engineering, Flinders University, Adelaide, SA, 5042, Australia.
The frequency of unprovoked shark bites is increasing worldwide, leading to a growing pressure for mitigation measures to reduce shark-bite risk while maintaining conservation objectives. Personal shark deterrents are a promising and non-lethal strategy that can protect ocean users, but few have been independently and scientifically tested. In Australia, bull (Carcharhinus leucas), tiger (Galeocerdo cuvier), and white sharks (Carcharodon carcharias) are responsible for the highest number of bites and fatalities.
View Article and Find Full Text PDFJ Fungi (Basel)
June 2024
Instituto de Investigaciones Químico Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Edificio B3, Ciudad Universitaria, Morelia C.P. 58030, Mexico.
is an entomopathogenic fungus that parasitizes and kills insects. The role of volatile organic compounds (VOCs) emitted by acting as semiochemicals during its interaction with lepidopterans is poorly explored. Here, we studied the effect of VOCs from and 3-methylbutanol (as a single compound) on the feeding behavior of L2 larvae of in sorghum plants.
View Article and Find Full Text PDFMolecules
June 2024
Laboratory of Insect Chemical Ecology, Department of Entomology, Faculty of Agricultural Sciences and Technology, Bahauddin Zakariya University, Multan 60800, Pakistan.
In this study, the chemical composition, repellent, and oviposition deterrent effects of five plant essential oils (EOs) extracted from (Verbenaceae), (Anacardiaceae), (Myrtaceae), (Asteraceae), and (Lamiaceae) were evaluated against , , and . When tested at 33.3 µg/cm, , , , and were effective repellents against (89%, 91%, 90%, and 51% repellency, respectively), but they were less repellent against (66%, 86%, 59%, and 49% repellency, respectively).
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