New conjugated metabolites of 3-phenoxybenzoic acid in plants

The metabolism of 3-phenoxybenzoic acid, a common plant metabolite of deltamethrin, cypermethrin and fenvalerate, has been studied in abscised leaves of cabbage, cotton, cucumber, kidney bean and tomato plants. The [¹⁴C]-acid was readily converted into more polar conjugates by esterification with glucose, 6-O-malonylglucose, gentiobiose, cellobiose, glucosylxylose and two types of triglucose with different isomerism. Other metabolites identified were the glucosyl ether of 3-(4-hydroxyphenoxy)benzoic acid, and a 3-(2-hydroxyphenoxy)benzoic acid derivative with a total of two molar equivalents of glucose linked to the carboxyl and phenolic -OH groups. The conjugation pathways were somewhat plant-specific. The glucosylxylose ester was found only in cotton, and the cellobiose and triglucose esters were found only in tomato. All of the conjugates except the glucose and glucosylxylose esters were plant metabolites that had not been identified previously. Furthermore, this is the first report to show the presence of cellobiose and triglucose conjugates in plants. However, neither of the acetyl derivatives of the [¹⁴C]-triglucoside was identical with the synthetic deca-acetyl derivative of [1→6]-triglucoside.     

The uptake of metabolites of permethrin by plants grown in soil treated with [14C]permethrin

Sugar beet, wheat, lettuce and cotton were grown in soil treated with [¹⁴C]permethrin, the crops being sown at intervals of 30, 60 and 120 days after treatment of the soil. The uptake of radioactive residues into these crops was measured. Low radioactive residues (up to 0.86 μg g^?1) were detected in the mature plants sown 30 days after soil treatment, and this uptake declined significantly as the interval between soil treatment and sowing increased. Metabolites derived from the acid moiety of the permethrin molecule were shown to constitute the greater part of the residue transferring from the soil to the crops. (1RS)-cis- and (1RS)-trans-3-(2,2-dichlorovinyl)- 2,2-dimethylcyclopropanecarboxylic acid and 3-(2,2-dichlorovinyl)-1-methylcyclopropane-1,2-dicarboxylic acid were identified as the major acidic metabolites. The latter compound is a metabolite of permethrin which has not previously been identified in soil or plants.     

The pyrethrins and related compounds. Part XXII. Preparation of isomeric cyano-substituted 3-phenoxybenzyl esters

Preparation of 3-phenoxybenzyl chrysanthemates and their dihalovinyl analogues substituted with a cyano group at the 2-, 6-, (R)-α-, or (S)-α- positions is described. The (R)- and (S)- isomers of α-cyano-3-phenoxybenzyl esters of 2,2-difluoro-, -dichloro-, and -dibromo-vinyl analogues of cis- and trans- chrysanthemic acid are separated chromatographically, as are the separate pairs of enantiomers of fenvalerate, (RS)-α- cyano-3-phenoxybenzyl (RS)-2-(4-chlorophenyl)-3-methylbutyrate. An optically active ester of α-cyano-3-phenoxybenzyl alcohol (obtained using D -oxynitrilase) with 2,2,3,3-tetramethylcyclopropanecarboxylic acid is synthesised.     

The pyrethrins and related compounds; Part XXIV: synthesis, 13C-nuclear magnetic resonance spectra and insecticidal activity of cycloalkyl analogues of fenvalerate

Close isosteres of fenvalerate [(RS)-α-cyano-3-phenoxybenzyl (RS)-2-(4-chlorophenyl)-3-methylbutyrate], in which cyclopropyl groups replace isopropyl have insecticidal activity close to or greater than the parent compounds, and diminished intravenous toxicity to rats. A direct toxicological relationship of these compounds to fenvalerate itself and to chrysanthemate esters is indicated by the consistently greater activity of esters from one of an enantiomeric pair of acids. Other esters with larger alkyl or cycloalkyl groups, or spiropentane analogues of chrysanthemates are less active insecticides. ¹³C-Nuclear magnetic resonance spectra suggest that in the α-cyanobenzyl esters there is an intramolecular through-space interaction in solution. The relationships between the chemical structures of the compounds synthesised and their relative activities to different insect species and toxicity to rats are discussed.     

Metabolism of DDT and related compounds in cell suspension cultures of soybean (Glycine max L.) and wheat (Triticum aestivum L.)

Cell suspension cultures of wheat and soybean were incubated with [¹⁴C]-1,1,1-trichloro-2,2-bis-(4-chlorophenyl)ethane (DDT), [¹⁴C]-1,1-dichloro-2,2-bis-(4-chlorophenyl)ethene (DDE), and [¹⁴C]-2,2-bis-(4-chlorophenyl)acetic acid (DDA) under standardized conditions. Polar metabolites were formed in yields of 1–2.5% in the cases of DDT and DDE, and of 56% in the case of DDA. A nonpolar metabolite was only observed in the case of DDT in soybean. This metabolite was identified as DDE on the basis of cochromatography and mass spectroscopy. By the same methods DDA was identified as a major polar DDT metabolite of both soybean and wheat. The further conversion of DDA to hexose esters was demonstrated by chromatographic and mass spectroscopic comparison with synthetic DDA-β-d-glucopyranosyl tetraacetate. These studies suggest the metabolic sequence, DDT → DDA → DDA-hexose ester.     

The metabolism of cypermethrin in plants: The conjugation of the cyclopropyl moiety

The metabolism of the pyrethroid insecticide cypermethrin ([S,R,]-α-cyano-3-phenoxybenzyl-(1R,1S,cis,trans)-2,2-dimethyl-3-(2′,2′-dichlorovinyl)cyclopropane carboxylate), I, has been examined in lettuce plants grown and treated twice under outdoor conditions with ¹⁴C-cyclopropyllabeled material. The application rate at each treatment was equivalent to 0.3 kg/ha. At harvest, 21 days after the last application, the plants contained mainly unchanged cypermethrin (33% of the total radiolabel present) and polar materials (54%) which were shown to be conjugates of trans-2(2′,2′-dichlorovinyl)-3,3-dimethylcyclopropane carboxylic acid (II). One of these was identified as the β,d-glucopyranose ester. In separate experiments the uptake and metabolism of the acid (II) in cotton leaves were examined in the laboratory and the acid was shown to be readily converted into a mixture of the β,d-glucopyranose ester, an acidic derivative of this, and disaccharide derivatives including the glucosylarabinose ester and the glycosylxylose ester. Subsequently, cotton leaves were exposed to solutions of these individual conjugates, and interconversions between these metabolites were observed.     

The pyrethrins and related compounds; Part XXIII:Kinetic control in the formation of pyrethroidal estersb

The unequal amounts of the two diastereomers of (RS)-1-(3-phenoxyphenyl)ethyl (RS)-2-(4-chlorophenyl)-3-methylbutyrate, obtained from equimolar proportions of the alcohol and acyl chloride under normal conditions, imply stereoselectivity in the reaction. The extent to which this depends on the nature of the α-substituent for arange of 3-phenoxybenzyl esters, on the nature of the acid, and on the method of esterification is investigated. Selectivity arises from kinetic, rather than thermodynamic control.     

烟粉虱成虫对不同寄主植物的选择性

选用棉花、烟草、番茄、甘蓝进行非选择性和选择性试验研究 ,探讨烟粉虱成虫对 4种寄主植物的嗜食性。结果表明 ,在 4种寄主作物共同存在时 ,烟粉虱成虫喜欢取食烟草 ,排列顺序为 :烟草 >番茄 >棉花、甘蓝 ;产卵量排列顺序为 :烟草、番茄 >甘蓝、棉花。当只有番茄和烟草两种寄主植物时 ,烟粉虱成虫趋向于取食烟草 ,但在番茄上产卵 ;只有烟草和甘蓝时 ,烟粉虱倾向于取食烟草并产卵 ;只有棉花和番茄时 ,烟粉虱对两种寄主没有明显的趋向 ;只有棉花和烟草时 ,烟粉虱显著的喜好在烟草上产卵 ;只有棉花和甘蓝时 ,烟粉虱趋向在棉花上取食产卵 ,但没有达到显著水平 ;同样只有番茄和甘蓝时 ,烟粉虱喜好在番茄上取食产卵 ,但没有达到显著水平。     

Stereochemical basis for the insecticidal activity of carbamoylated and acylated pyrazolines

Methyl 3-(4-chlorophenyl)-1-[N-(4-chlorophenyl)carbamoyl]-4-methyl-2-pyrazoline-4-carboxylate was converted to corresponding (1R)- and (1S)-phenethyl esters via its carboxylic acid and acid chloride at the C-4 atom to separate the diastereomers. Their configurations were confirmed by X-ray analysis. Both isomers of the (1R)methylbenzyl ester were subjected to transesterification with sodium methoxide to obtain enantiomers of the starting methyl ester. Their insecticidal activity was measured against American cockroaches (Periplaneta americana (L.)) by injection and against house flies (Musca domestica L.) by topical application under various synergistic conditions with metabolic inhibitors. The activity values of the four α-methylbenzyl esters and the R-isomer of the starting methyl ester were similar. The S-enantiomer of the methyl ester was about 10 and 100 times more active than the R-isomer against the cockroach and the fly, respectively. Some N-arylacetyl and N-aryloxyacetyl derivatives of the starting N-(4-chlorophenyl)carbamoyl compound gave very low activity. Conformation-energy profiles for some compounds suggested that the conformation of substituents on the N-1 atom in the pyrazoline ring has a specific role for the potential insecticidal effects.     

Metabolism of the cis- and trans-isomers of cypermethrin in mice

Metabolism in mice of the separated cis- and trans-isomers of the pyrethroid insecticide cypermethrin (NRDC 149), (RS)-α-cyano-3-phenoxybenzyl (1RS)-cis, trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate, was investigated in each case with preparations that were ¹⁴C-labelled in the benzyl and cyclopropyl moieties. Radioactivity from the trans-isomer was mainly excreted in the urine and that from the cis-isomer in the faeces. Elimination of both isomers was rapid except for a small portion (approximately 2%) of the cis-isomer which was released from the fat with a half-life of approximately 13 days. Metabolism of cypermethrin occurred mainly by ester cleavage and elimination of the cis- and trans-3-(2,2-dichlorovinyl)-2,2-dimethyl- cyclopropanecarboxylic acid moieties as glucuronide conjugates. The α-cyano-3-phenoxybenzyl alcohol released by ester cleavage was mainly converted to 3-phenoxy-benzoic acid which was partly eliminated unchanged, partly conjugated with aminoacids (mainly taurine) and glucuronic acid, and partly oxidised to 3-(4-hydroxyphenoxy) benzoic acid which was excreted as the sulphate conjugate. Metabolites retaining the ester linkage were formed by hydroxylation at various sites in the molecule with more hydroxylation of the cis- than of the trans-isomer occurring.     

The metabolism of 3-phenoxybenzyl alcohol,a pyrethroid metabolite,in plants

The metabolism and conjugation of 3-phenoxybenzyl alcohol, a plant metabolite of permethrin and cypermethrin, have been examined in abscised cotton leaves. Mature cotton leaves were treated by petiole uptake of an aqueous solution of [α-¹⁴C]-3-phenoxybenzyl alcohol. Initially there was rapid formation of a compound identified as the glucosyl 3-phenoxybenzyl ether. Subsequently more polar compounds were formed and these were shown to be disaccharide conjugates of the alcohol with glucose and pentose sugars. The alcohol and its mono- and disaccharide conjugates were shown to undergo interconversion in cotton leaves, and evidence was obtained from experiments with [¹⁴C]glucose for the ready exchange of the glucose units on the conjugates with free glucose in the leaves. No larger carbohydrate conjugates of 3-phenoxybenzyl alcohol were detected under the conditions used.     

Studies of the metabolism of 3-phenoxybenzoic acid in plants

The metabolism of ¹⁴C-labeled 3-phenoxybenzoic acid, PBA, has been studied in cotton, vine, broad bean, soya bean, pea, lettuce, and tomato, using abscised leaves. PBA was converted into a range of polar products by esterification with glucose (in cotton and other species) and with glucosylarabinose and glucosylxylose (especially in vine leaves). Uptake of the glucose ester itself by cotton leaves also led to conversion into a more polar conjugate, probably the glucosylarabinose ester, which was not detectable following uptake of PBA. When PBA was applied to the surface of intact cotton leaves, it was slowly converted into products similar to those above.     

Photodegradation of the pyrethroid insecticide fenpropathrin in water,on soil and on plant foliage

The photodegradation of fenpropathrin [(RS)-α-cyano-3-phenoxybenzyl 2,2,3,3-tetramethylcyclopropanecarboxylate] ( I ), in water, on soil and on plant foliage, was investigated using ¹⁴C-preparations labelled separately at the cyano group, cyclopropyl-C₁ or in the benzyl ring. On exposure to sunlight, I was photodecomposed with initial half-lives of >6 weeks in distilled water, 6.0 weeks in humic acid aqueous solution, 2.7 weeks in river water, 1.6 weeks in sea water and 0.5 of a day in 2% aqueous acetone. A triplet photosensitiser, acetone, together with naturally occurring substances in river and sea water, including humic acid, enhanced the photodegradation of I . On three kinds of soil, I was rapidly photodegraded with initial half-lives of 1–5 days, whereas it was fairly photostable on a mandarin orange leaf. The photoreactions involved were: decarboxylation, hydration of the cyano group to carboxamide, cleavage of the ester or the diphenyl ether linkage, hydrolysis of the carboxamide group to carboxyl, and hydroxylation at either or both of the gem dimethyl groups. The predominant reactions in water were decarboxylation, ester bond cleavage and photo-induced evolution of [¹⁴C] carbon dioxide from the [¹⁴C] cyano label; on soil, hydration or ester bond cleavage predominated. The hydration was also of importance in river and sea water. Decarboxylation did not occur on soil and plant foliage.     

The elimination of (N-[[(4-chlorophenyl)amino]carbonyl]-2,6-difluorobenzamide) by the boll weevil

Boll weevils, Anthonomus grandis Boheman, were either dipped in or injected with a solution of [¹⁴C]diflubenzuron (N-[[(4-chlorophenyl)amino]carbonyl]-2,6-difluorobenzamide) or fed on cotton squares that had been treated with the chemical to determine its turnover time and metabolic fate. No significant differences were observed between male and female weevils in their ability to eliminate [¹⁴C]diflubenzuron. Only minor differences were observed when immersion and injection treatments were compared. When weevils were treated with 66.3 ng of [¹⁴C]deflubenzuron per weevil by injection, the insects contained 13 to 15% of the radiolabel after 6 days and 4 to 6% after 13 days. The remainder of the radiolabel was in the frass. When weevils fed for 66 hr on cotton squares that had been treated with a wettable [¹⁴C]diflubenzuron preparation (Dimilin W-25), the insects averaged 120 ng of diflubenzuron per weevil. Forty-four hours after removing insects from the treated squares, 50% of the radiolabel had been excreted. In all cases, the radiolabel found in the frass or in the weevil was unchanged diflubenzuron. There were no data to indicate that the boll weevil could metabolize appreciable amounts of diflubenzuron.     

Analysis of soils for diclofop-methyl and diclofop

A method is described for the analysis of soils for residues of the herbicide diclofop-methyl, methyl (RS)-2-[4-(2,4-dichlorophenoxy)phenoxy]propionate, and its breakdown product diclofop, (RS)-2-[4-(2,4-dichlorophenoxy)phenoxy]propionic acid. Diclofop-methyl undergoes hydrolysis in the soil to diclofop, which also has herbicidal activity. A procedure, using a 1% phosphoric acid solution for extraction purposes, has been developed and gives good recoveries of both diclofop-methyl and diclofop at the 0.5 and 0.05 mg kg^?1 levels. After methylation, gas-liquid chromatography with electron-capture detection is used to determine total residue concentrations.     

The metabolism of the herbicide flamprop-methyl in wheat

The metabolism of the wild oat herbicide flamprop-methyl, methyl (±)-2-[N-(3-chloro-4-fluorophenyl)benzamido]propionate, in spring wheat grown to maturity has been studied under glasshouse and outdoor conditions. [¹⁴C]-Flamprop-methyl labelled separately in the halophenyl ring and the carbonyl of the benzoyl group was used. The major metabolite formed in plants was the corresponding carboxylic acid, II, which also occurred as conjugates. Other minor metabolites detected under glasshouse conditions only were the 3- and 4-hydroxybenzoyl analogues of flamprop-methyl and 3′-chloro-4′-fluorobenzanilide. The soil in which the plants were grown contained residues comprising mainly flamprop-methyl and II together with smaller amounts of unidentified polar material.     

Metabolism of cisanilide (cis-2,5-dimethyl-1-pyrrolidinecarboxanilide) by excised leaves and cell suspension cultures of carrot and cotton

Major methanol-soluble metabolites of cisanilide (cis-2,5-dimethyl-1-pyrrolidinecarboxanilide) were isolated from excised, pulse-treated carrot and cotton leaves. They were identified as O-glucoside conjugates of primary aryl and alkyl oxidation products, 2,5-dimethyl-1-pyrrolidine-4-hydroxycarboxanilide and 2,5-dimethyl-3-hydroxy-1-pyrrolidinecarboxanilide. Comparative studies with carrot and cotton cell cultures showed similar initial pathways of cisanilide metabolism. Time-course studies with [¹⁴C-pyrrolidine]- and [¹⁴C-phenyl]cisanilide showed little, if any, cleavage of the herbicide molecule in either excised leaves or cell cultures. Quantitative differences in the metabolism of cisanilide by cell cultures and excised leaves included; a reduced capacity of cell cultures to form secondary glycoside conjugates and an increased ability of cell cultures to form methanol-insoluble residues.     

Relation between volatility rating and composition of phenoxy herbicide ester formulations

A CIPAC/AOAC test with tomato plants is used to specify the volatility ratings of herbicide ester formulations. This work compares the tomato plant test with an alternative chemical one. The concentrations of esters and the effective molecular weight and density of each formulation were used with the ester vapour pressures to calculate its herbicide vapour pressure as complete, and evaporated formulations. The range was from 28.8 mPa (at 257deg;C) for a mixture of 2,4–D esters to 0–07 mPa (at 25°C) for a 2,4,5–T-(iso-octyl) formulation, as complete formulations, and 35-5 and 0–16 mPa (at 25°C) as evaporated ones. A value of 0–6 mPa (at 25°C) was selected on the basis of the tomato plant test as the cut-off area for low-volatile esters and is recommended to be included in specifications for herbicide esters. Formulations with a herbicide vapour pressure above 3.3 mPa (at 25°C) are high-volatile ones according to the tomato plant test, while between 0–6–3.3 mPa (at 25°C) is a borderline region where the test gives mixed results. Levels of 2,4–D-ethyl and methyl were added to pure 2–ethylhexyl esters of 2,4–D and a 2,4,5–T-(iso-octyl) formulation to find what level of contamination would change the rating of these esters from low to high volatile. Formulations of 2,4–D-(iso-octyl) should not contain more than 11 g litre^?1 2,4–D as methyl ester or 2.0 g litre^?1 2,4–D as ethyl ester. Formulations of 2,4,5–T-(iso-octyl) should not contain more than 26 g litre^?1 2,4–D as methyl ester or 4.7g litre^?1 2,4–D as ethyl ester.     

嘧啶联吡唑甲酰胺类化合物的合成及除草活性

设计合成了一系列结构新颖的嘧啶联吡唑甲酰胺类化合物5a~5o,其结构均经过1H NM R和MS分析确证。初步生物活性测试结果表明:在有效成分150 g/hm2剂量下苗后茎叶喷雾处理时,化合物(R)-N-[1-(4-氯苯基)乙基]-3-二氟甲基-1-(4,6-二甲氧基嘧啶-2-基)-1H-吡唑-4-甲酰胺(5c)、N-[1-(4-氯苯基)乙基]-1-(4,6-二甲氧基嘧啶-2-基)-N-甲基-3-三氟甲基-1H-吡唑-4-甲酰胺(5i)和N-[1-(4-氯苯基)乙基]-1-(4,6-二甲氧基嘧啶-2-基)-3-三氟甲基-1H-吡唑-4-甲酰胺(5k)对繁缕Stellaria media的抑制率高达90%以上;而同样剂量下苗前土壤喷雾处理时,化合物N-[1-(4-氯苯基)乙基]-3-二氟甲基-1-(4,6-二甲氧基嘧啶-2-基)-1H-吡唑-4-甲酰胺(5b)和5c对繁缕的抑制率达100%。该类结构化合物有望作为除草先导化合物进行开发。     

Inhibition of fatty acid biosynthesis in isolated bean and maize chloroplasts by herbicidal phenoxy-phenoxypropionic acid derivatives and structurally related compounds

The effects of nine phenoxy-phenoxypropionic acid derivatives and structurally related compounds on the incorporation of [¹⁴C]-acetate into free fatty acids in isolated bean and maize chloroplasts were studied. The compounds tested were esters and the corresponding free acids, OH-diclofop, a nonherbicidal metabolite of diclofop in plants, and d and l enantiomers of diclofop. Fatty acid biosynthesis in bean chloroplasts was not affected by all compounds. OH-Diclofop had a weak inhibitory effect on fatty acid synthesis in maize chloroplasts, while free acids were stronger inhibitors than the corresponding esters in the same system. Uptake studies with diclofop-methyl and diclofop indicated that the esters showed higher uptake rates in chloroplasts suspension. d-Diclofop (I₅₀, 9 × 10^?8M) was a more potent inhibitor than l-diclofop (I₅₀, 4 × 10^?6M). This agrees with the low herbicidal activity of the l enantiomer in vivo. The results suggest that the mode of action in this type of herbicide may be closely linked with the inhibition of fatty acid biosynthesis. The tolerance of beans could be based on an insensitivity of the target site.