Metabolism is one of the most important factors in controlling the toxicity and bioaccumulation of pesticides in fish. In vitro systems using subcellular fractions, cell lines, hepatocytes and tissues of a specific organ, each of which is characterized by usability, enzyme activity and chemical transport via membrane, have been applied to investigate the metabolic profiles of pesticides. Not only species and organs but also the fishkeeping conditions are known to greatly affect the in vitro metabolism of pesticides. A comparison of the metabolic profiles of pesticides and industrial chemicals taken under similar conditions has shown that in vitro systems using a subcellular S9 fraction and hepatocytes qualitatively reproduce many in vivo metabolic reactions. More investigation of these in vitro systems for pesticides is necessary to verify their applicability to the estimation of pesticide metabolism in fish.
Spraying a calcium carbonate suspension “White Coat” on the fruit of apples significantly suppresses the oviposition of the peach fruit moth, Carposina sasakii. In gas chromatography (GC) with an electroantennographic detector analysis, adult female antennae showed responses to three compounds that were identified as 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (TXIB) and its two mono-hydrolyzed analogs, texanols (1- and 3-isobutyrates), all added as a plasticizer to the agents. An oviposition-choice test using adult moths revealed that TXIB has clear deterrent properties when applied to young apple fruits. Video recording analysis showed that female moths spent longer on self-grooming and searching around TXIB-treated fruits. In the same assay, pure calcium carbonate treatment prevented the moths from climbing up or landing on the fruits, while such was not the case with White Coat-treated fruits. TXIB, an adjuvant aimed to provide rain/wind resistance, weakened the slipperiness of the calcium carbonate coating but, coincidentally, maintained the oviposition inhibitory activity of the White Coat by its deterrent odorant.
Imidacloprid is a pesticide used to control aphid infestations of cotton plants. However, poisoned aphids also serve as food for the ladybird natural predator Hippodamia variegata. We investigated whether imidacloprid-treated eggs, pupae, and adults of H. variegata and poisoned aphids altered ladybird predatory behavior. Laboratory bioassay results demonstrated that 0.72 g/L imidacloprid was lethal to ladybirds. Imidacloprid significantly reduced the hatching and emergence rates of H. variegata, and these effects were time and dose dependent. Predation was most adversely affected when the ladybirds directly consumed poisoned aphids and less so when directly exposed to the insecticide at sublethal concentrations. Imidacloprid use in cotton fields should be restricted to the initial stages of aphid infestation to avoid the period when adult ladybirds are present.
This study proposes a practical and precise method for the simultaneous analysis of seven neonicotinoid pesticides in agricultural products using liquid chromatography-tandem mass spectrometry from two different approaches. First, the applicability of a cleanup cartridge, comprised of a polymer sorbent consisting of a styrene-divinylbenzene copolymer with N-containing polar groups and methacrylate, in food samples was demonstrated for the first time. Second, applying an internal standard (IS) calibration method at a lower cost was considered by changing the timing of the IS addition and selecting the minimum number of ISs by referring on the matrix effect. The proposed method resulted in excellent recoveries in all tested matrices (brown rice, grapes, and peanuts) at a spiked concentration of 0.01 mg/kg. Subsequently, a residue analysis of hagobou (young burdock) was conducted. Imidacloprid was detected at 0.02 mg/kg, and the recoveries calculated in parallel with the analysis were satisfactory.
Six novel nicotinamide derivatives bearing a diarylamine-modified scaffold with flexible heterocyclic patterns were designed, synthesized, and characterized in detail via Hydrogen nuclear magnetic resonance (1H-NMR), Carbon nuclear magnetic resonance (13C-NMR), and Electrospray ionization mass spectrometry (ESI-MS). Their fungicidal activities and succinate dehydrogenase (SDH) enzymatic inhibitory abilities were evaluated. Preliminary fungicidal bioassay results showed that some of the target compounds exhibited moderate fungicidal activity. Among them, compound 4a showed 40.54% inhibition against Botrytis cinerea fungi. An SDH enzymatic inhibition assay revealed that the IC50 of compound 4b was 3.18 µM. This result indicated that the enzymatic inhibition level of 4b was similar to that of boscalid. Compound 4f exhibited superior comprehensive fungicidal and SDH enzymatic inhibitory activities. Molecular docking results suggested that 4f could bind well to the substrate cavity and the entrance cavity of SDH (1YQ3). In particular, 4f could react with the key catalytic site Arg 297. This phenomenon implied that 4f could act as the lead compound for further optimization.