Metabolism-related assays and their application to agrochemical research: reactivity of pesticides with glutathione and glutathione transferases†

Clarke, Eric D.; Greenhow, Daren T; Adams, D. L.

doi:10.1002/(sici)1096-9063(199812)54:4<385::aid-ps842>3.0.co;2-c

Cited by 38 publications

(28 citation statements)

References 14 publications

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“…In the molecules 15 and 16 the close proximity of ethereal oxygen to the carbonyl oxygen due to the single methylene group inserted between N and O atoms favours the sterically more stable form IV which is a more potent alkylating agent, whereas the longer alkyl chain in the structure of 17 and 18 reduces the anchimeric effect of the ether oxygen. Also, metolachlor was found to be 13‐fold less active in non‐enzymatic GSH conjugation than alachlor 19. In addition, the methyl group at the C‐chiral centre of 18 can further lower the reactivity of the molecule by hindering the reaction centre.…”

Section: Resultsmentioning

confidence: 99%

Alkylating reactivity and herbicidal activity of chloroacetamides

Jablonkai

2003

Pest Management Science

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The relationship between S- and N-alkylating reactivity and herbicidal activity within a series of chloroacetamides, including several commercial herbicides and newly synthesised analogues was studied. The S-alkylating reactivity of selected chloroacetamides, as well as those of atrazine and chlorfenprop-methyl, was determined by in vitro GSH conjugation at a ratio of GSH to alkylating agent of 25:1. A spectrophotometric reaction using 4-(4-nitrobenzyl)pyridine was used to characterise the N-alkylating reactivity of the chemicals. Our results indicate that a reduced level of N-alkylating reactivity correlates with an improved herbicidal efficacy at a practical rate. However, the phytoxicity of the molecules is not simply dependent on chemical reactivities, but strictly related to the molecular structure, indicating that lipophilicity, uptake, mobility and induction of detoxifying enzymes may also be decisive factors in the mode of action.

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Section: Resultsmentioning

confidence: 99%

Alkylating reactivity and herbicidal activity of chloroacetamides

Jablonkai

2003

Pest Management Science

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“…GSTs have a wide and overlapping ability to bind compounds of diverse structures and physical properties, though the specificity for xenobiotics is very low (Clarke et al, 1998). GST transcriptome-level responses of AtGSTF2, AtGSTU1, and AtGSTU24 in Arabidopsis exposed to TNT and RDX were significantly induced.…”

Section: Discussionmentioning

confidence: 99%

Gene Expression and Microscopic Analysis of Arabidopsis Exposed to Chloroacetanilide Herbicides and Explosive Compounds. A Phytoremediation Approach

et al. 2005

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Understanding the function of detoxifying enzymes in plants toward xenobiotics is of major importance for phytoremediation applications. In this work, Arabidopsis (Arabidopsis thaliana; ecotype Columbia) seedlings were exposed to 0.6 mM acetochlor (AOC), 2 mM metolachlor (MOC), 0.6 mM 2,4,6-trinitrotoluene (TNT), and 0.3 mM hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). In vivo glutathione (GSH) conjugation reactions of AOC, MOC, RDX, and TNT were studied in root cells using a multiphoton microscope. In situ labeling with monochlorobimane, used as a competitive compound for conjugation reactions with GSH, confirmed that AOC and MOC are conjugated in Arabidopsis cells. Reverse transcription-PCR established the expression profile of glutathione S-transferases (GSTs) and nitroreductases enzymes. Genes selected for this study were AtGSTF2, AtGSTU1, AtGSTU24, and two isoforms of 12-oxophytodienoate reductase (OPR1 and OPR2). The five transcripts tested were induced by all treatments, but RDX resulted in low induction. The mRNA level of AtGSTU24 showed substantial increase for all chemicals (23-fold induction for AOC, 18-fold for MOC, 5-fold for RDX, and 40-fold for TNT). It appears that GSTs are also involved in the conjugation reactions with metabolites of TNT, and to a lesser extent with RDX. Results indicate that OPR2 is involved in plant metabolism of TNT (11-fold induction), and in oxidative stress when exposed to AOC (7-fold), MOC (9-fold), and RDX (2-fold). This study comprises gene expression analysis of Arabidopsis exposed to RDX and AOC, which are considered significant environmental contaminants, and demonstrates the importance of microscopy methods for phytoremediation investigations.Uptake is a necessary prerequisite for close contact between the pollutant and the detoxifying enzymes of plants that are localized in the cytosol of living cells. The presence and activity of this complex array of enzymes is crucial for degradation of chemicals under consideration for phytoremediation (Coleman et al., 1997a). However, very little is known about the exact number of plant enzymes potentially involved in the metabolism of xenobiotic compounds and their capacity to bind and metabolize them (Schalk et al., 1997;Scwitzguebel and Vanek, 2003).The sequential metabolic steps of xenobiotics in plant metabolism are grouped in three main phases known as phase I (conversion), phase II (conjugation), and phase III (compartmentation;Sandermann, 1994;Ohkawa et al., 1999). Initial transformations in phase I include a number of oxidation, reduction, and hydrolysis reactions. Oxidation is the most often observed, while certain organics, such as nitroaromatics, tend to favor reduction processes (Hannink et al., 2002). Conjugations of xenobiotics represent phase II transformation reactions, which are usually mediated by a sugar moiety or tripeptide, such as malonic acid, D-Glc, glutathione, Cys, and other amino acids (Sandermann, 1994). Conjugation reactions result in the formation of products that are generally much less toxic,...

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“…Compound stock solution (20 µl) was added to buffer solution (2 ml) at 25 or 40 °C in HPLC vials for direct measurement of compound loss versus time by HPLC, as previously reported 6. A similar procedure was used to investigate the reactivity of selected indolizinediones with glutathione (GSH, 5 m M ) at different pH values, full details of which have also been reported 30…”

Section: Experimental Methodsmentioning

confidence: 99%

Herbicidal indolizine‐5,8‐diones: photosystem I redox mediators

Smith

Clarke

Ridley

et al. 2004

Pest Management Science

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6,7-Disubstituted indolizine-5,8-diones showed activity as herbicides, giving rapid desiccation symptomology in whole-plant tests and bleaching in leaf-disc assays. In isolated chloroplasts, such compounds initiated rapid uptake of oxygen in Photosystem I. A redox mediator mode of action was further supported by electrochemical studies. Several compounds described had low photostability, high volatility, hydrolytic instability or reactivity with glutathione. The detrimental effects that these factors may have had on expression of herbicidal activity are discussed.

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Metabolism-related assays and their application to agrochemical research: reactivity of pesticides with glutathione and glutathione transferases†

Cited by 38 publications

References 14 publications

Alkylating reactivity and herbicidal activity of chloroacetamides

Alkylating reactivity and herbicidal activity of chloroacetamides

Gene Expression and Microscopic Analysis of Arabidopsis Exposed to Chloroacetanilide Herbicides and Explosive Compounds. A Phytoremediation Approach

Herbicidal indolizine‐5,8‐diones: photosystem I redox mediators

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