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Determination of fungicide residues in fruits by coupled-column liquid chromatography.

Coupled-column liquid chromatography with fluorescence detection was applied to the determination of o-phenylphenol and bitertanol residues in orange and banana fruits. After extraction with a mixture of acetone, dichloromethane-petroleum ether, and ethyl acetate, an extract aliquot of 100 microL was injected directly without any additional clean-up into the chromatographic system using two reversed phase C18 coupled columns. The LC-LC approach allowed automated sample clean up of the vegetal extracts, leading to a simple and rapid analytical procedure, with limits of quantification between 0.01 and 0.05 mg kg(-1). Recovery experiments performed on orange and banana samples fortified at different concentrations (0.01 - 4 mg kg(-1)) gave average recoveries between 70 and 113% with relative standard deviations lower than 15%. The procedure developed was finally applied to orange and banana samples from different geographical locations and the results were confirmed by GC-MS.

Biphenyl Compounds↗

Discrimination of enantiomers by means of NMR spectroscopy using chiral liquid crystalline solution: application to triazole fungicides, uniconazole and diniconazole.

An NMR method for discriminating among enantiomers by using a chiral liquid crystalline solution was applied to chiral triazole compounds, uniconazole (1) and diniconazole (2), which exhibit antifungal and plant growth regulating activities. These chiral compounds were dissolved in PBLG (poly-gamma-benzyl-L-glutamate)--CDCl3 chiral liquid crystalline solvent for measurements of 13C NMR. The enantiomeric separations were primarily observed in the signals of aromatic carbons owing to differences in chemical shift anisotropies. The enantiomeric excess (ee) was determined from the integral scale of the separated peaks. The resulting ee values are in fair agreement with the actual values. The extrasplittings due to residual dipolar couplings were also measured using Het2DJ spectra for 1S and R, and 2R, and the results are discussed.

Anisotropy↗

In vivo effects of the fungicide ethaboxam on microtubule integrity in Phytophthora infestans.

The effects of ethaboxam (LGC-30473), a novel thiazole carboxamide, on microtubule organization was investigated in Phytophthora infestans (Mont) de Bary (Oomycota) at the light microscope level using standard immunofluorescence and laser scanning confocal microscopy. Hyphal cells were exposed to various concentrations ranging from 0.01 to 1.0 microg ml(-1) of ethaboxam at incubation times of 30, 60 and 120 min. Microtubules were disrupted after exposure to ethaboxam for 30 min at 0.01 microg ml(-1). Similar experimental conditions were used to document the effects of ethaboxam on microtubule integrity in the model fungus Aspergillus nidulans (Eidam) Winter (Ascomycota) and in mammalian mouse 17 clone 1 cells. Under these conditions, there was no evidence to suggest that microtubules in A. nidulans and mouse culture cells were affected by the ethaboxam. These results indicate that ethaboxam is specific for the targeting of microtubule disruption in P. infestans.

Animals↗

Synthesis and fungicidal activity of N-2-(3-methoxy-4-propargyloxy)phenethyl amides. Part II: anti-oomycetic mandelamides.

Novel types of anti-oomycetic compounds have been designed and prepared. The synthetic approach to these mandelamides is outlined. Biological data demonstrate their high efficacy against important plant diseases such as tomato and potato late blight (Phytophthora infestans De Bary) and grape downy mildew (Plasmopara viticola Berliner & de Toni). Structure-activity relationship studies are discussed. The new development product mandipropamid is presented.

Benzeneacetamides↗

Synthesis and fungicidal activity of N-2-(3-methoxy-4-propargyloxy) phenethyl amides. Part 3: stretched and heterocyclic mandelamide oomyceticides.

Novel analogues of mandipropamid have been designed and prepared. The synthetic approach to these stretched and heterocyclic mandelamides is outlined. Biological data demonstrate their high efficacy against important plant diseases like tomato and potato late blight (Phytophthora infestans De Bary) and grape downy mildew (Plasmopara viticola Berliner & de Toni). Structure-activity relationship studies are discussed.

Amides↗

The hydroxyanilide fenhexamid, a new sterol biosynthesis inhibitor fungicide efficient against the plant pathogenic fungus Botryotinia fuckeliana (Botrytis cinerea).

Fenhexamid, a recently developed botryticide, is shown here to inhibit sterol biosynthesis. When the fungus Botryotinia fuckeliana was grown in the presence of fenhexamid, the ergosterol content was reduced, and three 3-keto compounds, 4 alpha-methylfecosterone, fecosterone and episterone, accumulated, suggesting an inhibition of the 3-keto reductase involved in C-4 demethylation. Thus, fenhexamid belongs to a new, promising class of sterol biosynthesis inhibitors not previously used in agriculture or in medicine.

Amides↗

Fungicidal potential of methoxylated flavones from citrus for in vitro control of Colletotrichum gloeosporioides, causal agent of anthracnose disease in tropical fruits.

Four polymethoxylated flavones (3,5,6,7,3',4'-hexamethoxyflavone, 3,5,6,7,8,3',4'-heptamethoxyflavone, 5,6,7,8,4'-pentamethoxyflavone and 5,6,7,8,3',4'-hexamethoxyflavone) were isolated and characterized from cold-pressed orange oil. Their antifungal activities were evaluated against Colletotrichum gloeosporioides (Penz) Penz & Sacc, a major plant pathogen of fruits that causes significant damage to crops in tropical, sub-tropical and temperate regions. Methoxylated flavones were effective in inhibiting mycelial growth of the fungus. As flavone concentration increased, mycelial growth decreased. 5,6,7,8,3',4'-Hexamethoxyflavone completely inhibited the growth of Cgloeosporioides at a concentration of 100 microg ml(-1).

Citrus↗

Screening study for potential lead compounds for natural product-based fungicides: I. Synthesis and in vitro evaluation of coumarins against Botrytis cinerea.

An efficient, one-pot synthesis of angular and linear dihydropyranocoumarins, along with C-6 and C-8 prenylated coumarins is reported. These compounds, together with single- and furanocoumarins, were tested for their potential antifungal activity against the phytopathogen Botrytis cinerea Pers ex Fr. The results show that furanocoumarins may be able to control the fungus B cinerea.

Biological Factors↗

The fungicide benomyl inhibits differentiation of neural tissue in the Xenopus embryo and animal cap explants.

The toxic effect of benomyl on the embryogenesis of Xenopus laevis was investigated, and the tissues most affected by benomyl were identified. The toxicity of benomyl at various concentrations (5-20 microM) was tested with the Xenopus frog embryo teratogenesis assay (FETAX), used with slight modification. All test embryos subjected to 20 microM of benomyl died, and exposure to 10 and 15 microM benomyl produced growth inhibition and 11 types of severe external malformations. Histological examination of the test embryos showed dysplasia of the brain, eyes, intestine, otic vesicle, and muscle and swelling of the pronephric ducts and integuments. Among the tissues and organs affected, malformation of neural tissue was the most severe. The presumptive ectoderm isolated from st. 9 embryo was cultured in 10 ng/mL of activin A to induce neural tissue and mesoderm. When it was cultured with 10 ng/mL of activin A in the presence of 1 and 10 microM of benomyl, neural tissue induction was inhibited more severely than that of any other tissue. The gene expression of cultivated explants was investigated by reverse transcription-polymerase chain reaction (RT-PCR) assay in order to study the inhibition of neural tissue by benomyl. The results showed that with increasing benomyl concentration, the expression of the neural-specific marker NCAM (neural cell adhesion molecule), was more strongly inhibited than the muscle-specific marker muscle actin. Electron micrographs of test explants showed many residual yolk platelets and mitochondrial degeneration. In the present investigation the most severe toxic effects of benomyl were seen in the nerve tissues of the Xenopus embryo. This inhibition of neural development may have been caused by the inhibition of the assembly of neural microtubules and by the effect of benomyl on neuronal proliferation and migration.

Animals↗

Immunotoxicity of cupravit and previcur fungicides in mice.

Female mice received either cupravit or previcur at dose levels of 300 ppm and 1000 ppm, respectively, for 8 weeks. Humoral immune response was evaluated by measuring the plaque-forming cell (PFC) response and hemolysing antibody titers against sheep red blood cells (SRBCs), a T lymphocyte-dependent antigen. In addition, the hemagglutinating antibody titers against Escherichia coli lipopolysaccharide (LPS), a T cell-independent antigen, were determined. Both cupravit and previcur suppressed the PFC response by 74% and 78% of control values, respectively. The primary hemolysin antibody titers were reduced to 62% and 76% of control values, respectively. The hemagglutinating antibody titers were decreased to 66% and 77% of control values, respectively. Memory function was reduced as evidenced by inhibition of secondary hemolysin titers to SRBCs. Cell-mediated immunity was inhibited by both cupravit and previcur as evidenced by reduced delayed-type hypersensitivity (DTH) reaction to tuberculin to 77% and 76% of control values, respectively. Decreases in total leukocytic and lymphocytic counts were recorded together with histopathological changes in spleen and thymus gland of intoxicated animals.

Animals↗

Mepanipyrim, a new fungicide, inhibits intracellular transport of very low density lipoprotein in rat hepatocytes.

We have previously reported that ingestion of mepanipyrim induces fatty liver in rats due to the inhibitory effect on the synthesis or secretion of hepatocytic very low density lipoproteins (VLDL). To clarify the mechanism by which mepanipyrim induces fatty liver, morphological and biochemical effects of mepanipyrim on the movement of VLDL in rat liver and in the primary culture of rat hepatocytes were investigated. In in vivo experiments, rats were fed for 4 days a diet containing mepanipyrim at 4,000 ppm. VLDL accumulation in the Golgi apparatus of the liver, especially in the secretory vacuoles, was observed in the treated rats and in the hepatocytes treated for 2 hr with 25 micrograms/ml mepanipyrim. Using 6-[N-(7-nitrobenz-2-oxa-1, 3-diazol-4-yl)amino]caproyl-sphingosine (C6-NBD-ceramide), a selective staining agent for the Golgi apparatus, it was found that mepanipyrim inhibited C6-NBD-ceramide transport from the Golgi to the cell surface of cultured hepatocytes. The density of the VLDL-loaded secretory vacuoles isolated from the Golgi fractions was greater in mepanipyrim-treated rat livers compared with that in the control. Immunofluorescence micrograph of rat hepatocytes stained with anti-alpha-tubulin monoclonal antibody demonstrated that mepanipyrim neither affected microtubule network nor changed the intracellular ATP level. These results together suggested that fatty liver induced by mepanipyrim results mainly from the inhibition of the transport of hepatic VLDL from the Golgi to the cell surface. The inhibition of the transport of hepatic VLDL appears to result from qualitative changes in VLDL such as alteration of the apoprotein composition and/or insufficient lipidation of VLDL.

Adenosine Triphosphate↗

Effect of dithiocarbamate fungicides and thiurams on 3H-haloperidol binding in rat brain.

Dithiocarbamates and disulfiram have been shown to be neurotoxic. As one biochemical indicator of the toxicity, dopamine-beta-hydroxylase is inhibited in the brain. Consequently, noradrenaline synthesis is decreased and dopamine tends to accumulate in the brain. It was decided to examine whether cerebral dopaminergic D2-receptor binding is affected by these agents after their short-term administration to rats. It appeared that ferbam, maneb, nabam, zineb, disulfiram, thiram and ethylene thiourea did not change significantly D2-receptor binding at doses which were already overtly toxic.

Animals↗

Identification of the yeast ACC1 gene product (acetyl-CoA carboxylase) as the target of the polyketide fungicide soraphen A.

Soraphen A, a polyketide isolated from the myxobacterium Sorangium cellulosum, is a potent inhibitor of fungal growth. We have used a genetic approach to localize the target of this drug, employing Saccharomyces cerevisiae as a model organism. we have isolated soraphen A-resistant mutants and found that all of them map at the same genetic locus and exhibit a broad range of semidominant phenotypes. Data from genetic crosses of soraphen A-resistant clones with an acc1 mutant revealed that ACC1, coding for acetyl-CoA carboxylase (E.C. 6.4.1.2), is tightly linked to soraphen A resistance. Partially-purified enzyme extracts containing acetyl-CoA carboxylase were prepared and assayed for their soraphen A sensitivity. Our experiments showed that the catalytic activity of the wild-type enzyme is inhibited in vitro by soraphen A while the mutant enzyme remains catalytically active. Taken together these data strongly suggest that the ACC1 gene product is the primary target for soraphen A in vivo.

Acetyl-CoA Carboxylase↗