| | 1 | Author
| DonaldE M Oreland, FrederickT. Corbin | Requires cookie* | | | Title
| Influence of Safeners on the in vivo and in vitro Metabolism of Bentazon and Metolachlor by Grain Sorghum Shoots: a Preliminary Report  | | | | Abstract
| Metabolism of bentazon and m etolachlor by excised shoots and a microsomal fraction iso lated from the shoots, of 3-day-old, dark-grown, grain sorghum (Sorghum bicolor cv. Funk G 522 DR) seedlings was studied. The effects of seed treatments, on the subsequent m etabo lism of the herbicides, with the safeners naphthalic anhydride, oxabetrinil, and CGA 133205 were compared against surface-sterilization and Captan-treatm ents. Bentazon was aryl hydroxylated in both in vivo and in vitro studies with the hydroxylated derivative undergoing glycosylation only under in vivo conditions. Both shoots and microsomes isolated from shoots of safener-treated seed showed enhanced metabolism of bentazon relative to the controls. In hibition by tetcyclacis, a potent inhibitor of plant cytochrome P-450 monooxygenases, in both the in vivo and in vitro studies, and a requirement for N A DPH in the in vitro studies suggested that the formation of hydroxybentazon was mediated by a cytochrome P-450 monooxygenase. Metolachlor was metabolized to polar material and O-desmethylmetolachlor under in vivo conditions. Only the demethylated product was formed in vitro. Shoots isolated from safener-treated seed showed enhanced form ation o f polar com pounds which were assumed to have arisen from conjugation with glutathione. Tetcyclacis did not affect the formation of the polar components. However, the form ation of O-desmethylmetolachlor was depressed in the shoots excised from safener-treated seed under both in vivo and in vitro conditions. Tetcyclacis com pletely prevented form ation of the demethylated metabolite. Hence, formation of this m eta bolite is considered to be P-450 mediated. The differential response obtained with the safeners, i.e., stimulation of aryl hydroxylation o f bentazon and depression of metolachlor demethyla-tion, suggests that the reactions are probably catalyzed by different cytochrome P-450 m ono oxygenases. | | | |
Reference
| Z. Naturforsch. 46c, 906—914 (1991); received M arch 26 1991 | | | |
Published
| 1991 | | | |
Keywords
| Microsomes, Metolachlor, Bentazon, Cytochrome P-450, Mixed Function Oxidase | | | |
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| default:Reihe_C/46/ZNC-1991-46c-0906.pdf | | | | Identifier
| ZNC-1991-46c-0906 | | | | Volume
| 46 | |
| 2 | Author
| DonaldE. Moreland, FrederickT. Corbin, WilliamP. Novitzky, CarolE. Parker, KennethB. Tomer | Requires cookie* | | | Title
| Metabolism of Metolachlor by a Microsomal Fraction Isolated from Grain Sorghum ( Sorghum bicolor) Shoots | | | | Abstract
| A microsomal fraction isolated from the shoots of 3-to 4-day-old, dark-grown, grain sor ghum (Sorghum bicolor cv. Funk G 522 D R) seedlings was characterized. The preparations had a cytochrome P-450 content that varied from approximately 90 to 150 pmol P-450/mg protein with cytochrome P-420 varying from 0 to 3% of the P-450 content. Type I difference spectra were formed with cinnamic acid and metolachlor, and a type II spectrum was formed with tetcyclacis. In short-term assays with [14C]metolachlor as substrate, the preparations produced a single time-dependent product that separated on silica gel TLC plates developed in benzene/ acetone (2:1, v/v). R F values for metolachlor and the metabolite were approximately 0.70 and 0.48, respectively. The microsomal reaction required N A D PH and oxygen, and was inhibited by carbon monoxide, with the inhibition being partially reversed by actinic light. Compounds known to inhibit the activity of cytochrome P-450 monooxygenases (piperonyl butoxide, tet cyclacis, and tridiphane) also prevented formation of the metabolite. Identity of the metabolite was confirmed by TLC and positive ion thermospray LC/MS to be 2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-hydroxy-l-methylethyl)acetamide. Hence, the reaction catalyzed by the sorghum microsomes involved O-demethylation of the methoxypropyl side chain of meto lachlor. | | | |
Reference
| Z. Naturforsch. 45c, 558—564 (1990); received November 9 1989 | | | |
Published
| 1990 | | | |
Keywords
| Microsomes, Metolachlor, Cytochrome P-450, Mixed Function Oxidase, Herbicide Metabolism | | | |
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| default:Reihe_C/45/ZNC-1990-45c-0558.pdf | | | | Identifier
| ZNC-1990-45c-0558 | | | | Volume
| 45 | |
| 3 | Author
| P. Eter, B. Öger, R. Osw, M. Iller | Requires cookie* | | | Title
| Protoporphyrin Accumulation Induced by Peroxidizing Herbicides is Counteracted by Safeners | | | | Abstract
| A number of safeners like naphthalene-1,8-dicarboxylic acid anhydride (naphthalic anhy dride) or dichloroacetyl-hexahydro-3,3,8-a-trimethylpyrrolo-[l ,2 a]-pyrimidine-6-(2 H)-one (BAS 145138) drastically decreased the accumulation of protoporphyrin IX induced by a peroxidative cyclic imide (chlorophthalim, N-(4-chlorophenyl)-3,4,5,6-tetrahydrophthal-imide), or p-nitrodiphenyl ether (acifluorfen methyl, 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoicmethylester). This effect was observed with etiolated maize and cress seedlings during a 16-h illumination period with these herbicides and 0.1 to 1 mM safener present. The safeners did not affect the inhibition of protoporphyrinogen oxidase, the target enzyme of peroxidative herbicides. Mixed function oxidase inhibitors did not influence this safening effect. A microsome preparation from safener-treated maize seedlings did neither degrade protoporphyrin IX nor protoporphyrinogen IX. | | | |
Reference
| Z. Naturforsch. 49c, 775—780 (1994); received October 13 1994 | | | |
Published
| 1994 | | | |
Keywords
| Peroxidizing Herbicides, Safeners, Protoporphyrin IX Accumulation, Protoporphyrinogen Oxidase, Mixed Function Oxidase | | | |
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| default:Reihe_C/49/ZNC-1994-49c-0775.pdf | | | | Identifier
| ZNC-1994-49c-0775 | | | | Volume
| 49 | |
| 4 | Author
| D. Onald, E. M. O Relan D, T. Hom, J. Fleischm, FrederickT C Orbina, JanisE M Cfarlandb | Requires cookie* | | | Title
| Differential Metabolism of the Sulfonylurea Herbicide Prosulfuron (CGA-152005) by Plant Microsomes | | | | Abstract
| Microsomes isolated from excised shoots of 3-day-old. dark grown, grain sorghum [Sor ghum bicolor (L.) Moench, Funk G522DR and DK 41Y] and corn seedlings [Zea mays (L.), Pioneer 3245] metabolized the sulfonylurea herbicide prosulfuron (CGA-152005). Corn microsomes predominantly formed a single major metabolite that resulted from hydroxyla-tion of the phenyl ring at the C5 position. However, sorghum microsomes formed two major metabolites in an approximate 1:1 ratio. One was the 5-hydroxyphenyl metabolite, whereas the second metabolite resulted from ö-demethylation at C4 of the triazine ring. Metabolite identity was established by mass spectrometry and co-chromatography with authentic stan dards. Metabolism in both corn and sorghum was greatly enhanced by pretreatment of the seed with naphthalic anhydride and by subirrigation with 2.5% ethanol 24 h prior to harvest. Metabolism required a reduced pyridine nucleotide and was affected by several cytochrome P450 monooxygenase inhibitors (carbon monoxide, tetcyclacis, piperonyl butoxide, 1 amino-benzotriazole, and SKF-525A). The inhibitors differentially affected metabolism of prosul furon. Microsomal oxidations from both untreated and inducer-treated tissue responded simi larly to the inhibitors. In exploratory studies, microsomes isolated from shoots of wheat [Triticum aestivum L., Pioneer 2548], barley [Hordeum vulgare L., Boone], oats [Avena sativa L., Southern States 76-30-P242] and rice [Oryza sativa L" Gulfmont], and room ripened avocado [Persea americana, Mill., Hass] mesocarp tissue also primarily formed the 5-hydroxy-phenyl metabolite. Titration of seven different avocado microsomal preparations with prosul furon provided typical type I difference spectra from which an average binding constant (/Cs) of 187 ± 35 [.im was obtained. Abbreviations: 1-ABT, 1-aminobenzotriazole; alachlor, 2-chloro-.'V-(2.6diethylphenyl)-/V-(methoxymethyl)acet-amide; ALS, acetolactate synthase; CG A 24704, 2-chloro-N-(2,6-dimethylphenyl)-/V-(2-methoxy-l-methylethyl)acet-amide; CGA-150829. 2-amino-4-methoxy-6-methyl-l,3,5-triazine; CGA-152005, prosulfuron, N-[[(4-methoxy-6-methyl-l,3,5-triazin-2-yl) amino]carbonyl]-2-(3,3,3-trifluoropropyl)benzenesulfonamide; CGA -l59902, 2-(3,3,3-tri-fluoropropyl)benzenesulfonamide; CGA-300406, 0-desmethyl prosulfuron, N[[(4-hydroxy-6-methyl-l,3,5-triazin-2-yl)amino]carbonyl]-2-(3,3,3-trifluoropropyl)benzenesulfonamide; CGA-300408, 5-hydroxy prosulfuron, N-[[(4me-thoxy-6-methyl-l,3,5-triazin-2-yl)amino]carbonyl]-2-(3,3,3-trifluoropropyI)-5-hydroxybenzenesulfonamide; chlorsul-furon, l-(2-chlorophenylsulfonyl)-3-(4-methoxy-6-methyl-l,3.5-triazin-2-yl)urea; pCMA, /?-chloro-./V-methylaniline: DMA, /V,/V-dimethylaniline; DMSO. dimethyl sulfoxide; DTT, dithiothreitol; G6P. glucose-6-phosphate; HPLC, high-performance liquid chromatography; LC/ESI/MS. liquid chromatography/ electrospray ionization/mass spectrome try; metolachlor, 2-chloro-/V-(2-ethyl-6-methylphenyl)-/V-(2-methoxy-l-methylethyl)acetamide; NA. 1,8-naphthalic anhydride; nicosulfuron, 2-[[(4.6-dimethoxypyrimidin-2-yl)aminocarbonyl]aminosulfonyl]-./V,/V-dimethyl-3-pyridinec-arboxamide; PBO. piperonyl butoxide; primisulfuron. 2-[[[[[4.6-bis(difluoromethoxy)-2pyrimidinyl]amino]carbony-l]amino]sulfonyl]benzoic acid: PVPP. polyvinylpolypyrrolidone; SKF-525A. 2-(diethylamino)ethyl-2.2-diphenylpen-tanoate; tetcyclacis, 5-(4-chlorophenyl)-3,4.5.9,10-pentaazatetracyclo[5.4.102-6,0811] dodeca-3.9-diene; TLC. thin layer chromatography: triasulfuron, l-(2-chloroethoxyphenylsulfonyl)-3-(6-methoxy-4-methyl-l,3.5-triazin-2-yl)urea. Reprint requests to Dr. D. E. Moreland. Telefax: (001) 919-515-7959. 0939-5075/96/0900-0698 $ 06.00 © 1996 Verlag der Zeitschrift für Naturforschung. All rights reserved. D D. E. Moreland et al. ■ M etabolism of Prosulfuron by Plant Microsomes 699 | | | |
Reference
| Z. Naturforsch. 51c, 698—710 (1996); received May 14/June 17 1996 | | | |
Published
| 1996 | | | |
Keywords
| Microsomes, Prosulfuron, Cytochrome P450, Mixed Function Oxidases, Herbicide Metabolism | | | |
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| 51 | |
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