Interaction of formamidines with octopamine-, dopamine-and 5-hydroxytryptamine-sensitive adenylate cyclase in the nerve cord of Periplaneta americana

The interaction of chlordimeform, N¹-demethylchlordimeform [N²-(4-chloro-o-tolyl)-N¹-methylformamidine], BTS-27271 [N¹-methyl-N²-(2,4-xylyl)formamidine, the 2,4-xylyl analogue of N¹-demethylformamidine], and amitraz with octopamine-, dopamine-, and 5-hydroxytryptamine-mediated enhancement of cyclic-AMP production was investigated in nerve cord homogenates of the American cockroach Periplaneta americana. N¹-Demethylchlordimeform, BTS-27271 and amitraz simulated the actions of the monoamines in enhancing cyclic-AMP production, whereas chlordimeform showed no such agonism. Additivity studies indicated that these formamidine derivatives were interacting with dopamine- and 5-hydroxytryptamine-sensitive sites, in addition to their known interaction with octopamine-sensitive adenylate cyclase. N¹-Demethylchlordimeform (Ki= 0.2μM) and amitraz (Ki=0.5μM) inhibited the dopamine-mediated response, but only N¹-demethylchlordimeform (Ki=2μM) effected appreciable inhibition of the octopamine-response. Pharmacological characterisation of the formamidineinduced elevation of cyclic-AMP production indicated that the agonistic effects of formamidines are expressed primarily through the octopamine-sensitive adenylate cyclase, rather than the dopamine- or 5-hydroxytryptamine-sensitive sites. The results are discussed in the light of the proposal that the behavioural changes, associated with formamidine poisoning, reflect the cumulative effects of octopamine-agonism, and antagonism of the dopamine- and 5-hydroxytryptaminemediated processes.     

Effects of U-40481 and formetanate on the isolated rabbit central ear artery

Formetanate, a formamidine-type pesticide, and U-40481 (N-methyl-N′-2,4-xylylformamidine), a metabolite of amitraz, also a formamidine pesticide, contract the rabbit central ear artery with their maximal contractions being 22 ± 8% and 49 ± 6% of norepinephrine contractions, respectively. Maximal contractions were obtained with 10^?3M formetanate and 10^?4M U-40481, and cumulatively added higher concentrations caused a decrease in tension from that maximum. Their contractions were antagonized by 10^?6M and 3 × 10^?6M phentolamine. U-40481 reversibly antagonized contractions induced by serotonin, norepinephrine, and histamine, and to some extent potassium. Formetanate had little antagonist activity. Neither compound altered the resting rate of washout of radioactivity from [³H]norepinephrine preloaded strips. Both reduced electrically induced release, which may be related to local anesthetic-like actions on sympathetic neurones. Thus both compounds are partial agonists at the α-adrenergic receptor, and reduce electrically induced norepinephrine release, and U-40481 antagonizes contractions induced by certain other vasoactive agents.     

Transformations of 4-chloro-o-toluidine in soil: Generation of coupling products by one-electron oxidation

Four coupling products formed by one-electron oxidation of 4-chloro-o-toluidine were isolated from soil samples after 90 days of incubation with [¹⁴C]chlordimeform (200 mg/kg). The metabolic compounds were identified as 4,4′-dichloro-2,2′-dimethyl-azobenzene, 4-chloro-6-nitro-o-toluidine, N-(4-chloro-o-tolyl)-2-methyl-p-benzoquin-one monoimine and 2-(4-chloro-o-toluidino)-N-(4-chloro-o-tolyl)-6-methyl-p-benzo-quinone monoimine, respectively. Mechanisms of formation and possible significance of these substances as indicators for metabolic pathways to mineralisation of aniline derivatives are discussed. The chlordimeform soil concentrations (70–100 mg/kg) necessary for the formation of the azobenzene and the benzoquinone monoimines are at least 10 times higher than those occurring after actual field application.     

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。     

Structural Effects of N-Arylcarbamoylpyrazolines on Calcium Uptake in Rat Brain Synaptosomes

N-Arylcarbamoylpyrazolines with various substituents at the para position of the carbamoyl benzene ring inhibited ATP-dependent Ca²⁺-uptake in synaptosomes prepared from the rat brain. The activity of these compounds was evaluated as log(1/I₅₀), the reciprocal logarithm of half inhibitory concentration, I₅₀ (m ), from the concentration–response curve for the inhibition of Ca²⁺-uptake. Among the compounds tested, methyl 3-(4-chlorophenyl)-4-methyl-1-[N-(4-trifluoromethylphenyl)carbamoyl]-2-pyrazoline-4-carboxylate was the most potent, the I₅₀ value of which as 9·12×10⁻⁷ m . Variations in the activity in terms of log(1/I₅₀) were quantitatively analysed using a substituent parameter, showing that the higher the electron-withdrawing effect of the substituent, the higher was the activity. The substituent effects were similar to those on insecticidal activity against the Americal cockroach. The higher the inhibitory activity against Ca²⁺ uptake, the higher seemed to be the insecticidal activity. Methyl(4S) - 3 - (4 - chlorophenyl) - 4 - methyl - 1 - [N - (4 - chlorophenyl)carbamoyl] - 2 - pyrazoline -4-carboxylate had higher inhibitory activity against Ca²⁺-uptake and higher in-secticidal activity than the R-isomer, but the difference was greater in theCa²⁺-uptake system.     

Stereochemistry and active conformation of a novel insecticide,acetamiprid

Acetamiprid, (NI-25; (E)-N¹-[(6-chloro-3-pyridyl)methyl]-N²-cyano-N¹-methylacetamidine), is a novel neonicotinoid insecticide having an N-cyanoacetamidine structure as its characteristic feature. The [¹H] and [¹³C]-NMR spectra indicated the existence of two different structures in acetamiprid at room temperature in solution. The measurement of CH-NOE and C–C coupling constants proved the E-configuration at the cyanoimino group in both existing structures. The [¹³C] chemical shifts of N-CH₃ and the long range C–H coupling in the formamidine analogue of acetamiprid suggested that there exist two conformers generated by the rotation of C–C single bond in the amidine moiety. Dynamic NMR spectra of acetamiprid and the computer simulation of the two-site exchange demonstrated that the two conformers change slowly to each other at room temperature. The conformational analysis by semi-empirical molecular orbital calculations using MNDO-PM3 method predicted four conformers as energy-minimum structures, among which two E-conformers were more stable than Z-conformers. One of the E-conformers in which two methyl groups are in cis configuration was superimposable onto the structure of imidacloprid, which is a known neonicotinoid insecticide having more rigid structure. This E-conformer was assumed as the active conformation of acetamiprid on the basis of the molecular similarity in terms of steric and electrostatic properties. © 1997 SCI     

Toxicology and metabolism of chloromethiuron in Boophilus microplus larvae

The toxicity of the acaricide chloromethiuron, 3-(4-chloro-o-tolyl)-1,1-dimethyl- (thiourea), and of nine related compounds to Boophilus microplus larvae was determined by a spray-tower method. Four of these compounds were toxic but only chloromethiuron and its N-demethyl derivative were of practical importance. Metabolism of [¹⁴C]chloromethiuron, in the formamidine-susceptible but organo-phosphorus-resistant Mt. Alford strain, was compared with that in a chlordimeform-selected Mt. Alford strain, which in laboratory tests was two to three times resistant to chloromethiuron, chlordimeform and amitraz. The latter strain produced smaller quantities of the toxic N-demethyl derivative than the Mt. Alford strain; this was the only resistance mechanism determined. Rates of degradation of chloromethiuron were the same in both strains. Piperonyl butoxide strongly antagonised the toxicity of chloromethiuron by 18 to 33 times and depressed the production of the N-demethyl derivative in both strains (0.3 times that of the control), while degradation rates of chloromethiuron itself were halved by piperonyl butoxide in both strains. These results indicated that the parent material was not toxic until oxidised to the N-demethyl derivative. As, in addition, some symptoms of chloromethiuron toxicosis in larvae were similar to those caused by formamidine acaricides, a common mode of lethal action is suggested.     

The fungicidal activity of substituted 1,4-naphthoquinones. Part III: Amino,anilino and acylamino derivatives

A variety of 2-amino-, 2-anilino- and 2-acylamino-1, 4-naphthoquinones, with hydrogen, chlorine, alkoxy, phenoxy, methylthio or phenylthio as the 3-substituent, have been synthesised and assayed against Botrytis cinerea, Cladosporium fulvum and Venturia inaequalis. With few exceptions, only the 2-acylamino compounds possessed appreciable fungicidal activity: this was of a high order in the cases of 2-prop-ionamido-, 2-N-methylacetamido-3-methylthio-, and 3-methoxy-2-N-methylacetamido-1, 4-naphthoquinones.     

Distribution and degradation of dinitroaniline herbicides in an aquatic ecosystem

The accumulation potential of six, structurally related, dinitroaniline herbicides was investigated in an aquatic ecosystem. The herbicides investigated were trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine), profluralin [N-(cyclopropylmethyl)-α,α,α-trifluoro-2,6-dinitro-N-propyl-p-toluidine], dinitramine [N³,N³-diethyl-2,4-dinitro-6-(trifluoromethyl)-m-phenylenediamine], chlornidine [N,N-bis(2-chloroethyl)-2,6-dinitro-p-toluidine], fluchloralin [N-(2-chloroethyl)-2,6-dinitro-N-propyl-4-(trifluoromethyl)aniline], and butralin [4-(1,1-dimethylethyl)-N-(1-methylpropyl)-2,6-dinitrobenzenamine]. The herbicide (0.1 mg) plus 1 μCi of ¹⁴C-labeled herbicide was adsorbed on 100 g of soil (1 ppm), added to individual aquariums, and flooded with 4 liters of water. Algae, snails, and daphnia were added, and ¹⁴C in water was monitored for 30 days. Fish were added on Day 30, and all components were harvested 3 days later. Bioaccumulation ratios (concentration in organism/concentration in water) for fish depended on the amount of their exposure to sunlight: Aquariums held in the dark had higher ratios for fish (235–755) than did those exposed to sunlight (32–83). Bioaccumulation ratios in the dark for fish based on ¹⁴C from bound soil residues of butralin and profluralin were 76 and 119, respectively. Direct repeated applications of profluralin (without soil) at 4-day intervals resulted in a rapid increase, then a decrease in bioaccumulation ratios for Gambusia, but a continuous increase for catfish.     

Formamidine structure and detachment of the cattle tick Boophilus microplus

Evaluation of the effectiveness of topically applied chlordimeform, 14 other formamidines, and 5 sulfur-containing related nonformamidine compounds in causing female Boophilus microplus ticks to detach from mice enabled activity to be related to structure. Five compounds were inactive and 15, including 2 sulfur-containing nonformamidines and 1 sulfur-containing formamidine were active at doses ranging from 0.0005 to 2.0 μg/tick. The most active compounds were the N-monomethyl formamidines, BTS-27271 [N′-(2,4-dimethylphenyl)-N-methylformamidine], and C-8520 (demethylchlordimeform). Among the analogs of chlordimeform tested, those with alkyl substitutions at the amino nitrogen decreased in effectiveness in the order, monomethyl (demethylchlordimeform), monoethyl, mono-n-butyl, mono-i-butyl, mono-i-propyl, dimethyl (chlordimeform), and di-n-propyl. Inactive compounds resulted from the replacement of the chlorine at ring position 4 of the aryl moiety of chlordimeform by bromine or hydrogen or by the conversion of the NCH amidino moiety to the NHCSN < thiourea moiety.Detachment due to chlordimeform was antagonized by piperonyl butoxide but that due to its N-monomethyl analog, a known metabolite of chlordimeform in ticks, was synergized by the same compound. These effects on the detaching response parallel those reported elsewhere concerning synergism and antagonism of toxic responses of B. microplus to formamidines.BTS-27271, which was the most effective formamidine in causing detachment after topical application to ticks was moderately effective when injected into mice but its potency relative to chlordimeform was considerably reduced; when sprayed onto cattle BTS-27271 was somewhat more effective in depressing percentage survival of ticks of all stages than chlordimeform.     

Effects of benomyl,carbendazim and thiophanates on respiration and oxidative phosphorylation of Fusarium oxysporum and Saccharomyces cerevisiae

Benomyl [methyl 1-(butylcarbamoyl)-benzimidazol-2-ylcarbamate] (350 × 10^?6 M) decreased the respiration rate of Fusarium oxysporum conidia by 50% during germination. This inhibition was maintained at least 24 h after the treatment had begun. The treatment did not modify the relation between incubation time and respiration rate. Carbendazim [methyl benzimidazol-2-ylcarbamate], thiabendazole[2-(thiazol-4-yl)benzimidazole], thiophanate [1,2-di-(3-ethoxycarbonyl-2-thioureido)benzene] and thiophanate-methyl [1,2-di-(3-methoxycarbonyl-2-thioureido)benzene] were assayed using isolated mitochondria of Saccharomyces cerevisiae. These four compounds decreased mitochondrial respiration and oxidative phosphorylation rates to different extents when they were applied at a concentration of 250 × 10^?6 M . Thiophanate-methyl was the most effective since it completely suppressed the mitochondrial respiratory control at 75 × 10^?6 M .     

The fate of imidacloprid in tobacco smoke of cigarettes made from imidacloprid-treated tobacco

The residues and metabolites of radiolabelled imidacloprid [1-(6-chloropyridin-3-ylmethyl)-N-nitroimidazolidin-2-ylideneamine], formulated as a wettable powder containing 250 g kg^-1 active ingredient diluted with water and administered to tobacco plants, were studied in sidestream and mainstream smoke, in the ash and butts after smoking cigarettes. An almost complete recovery of radioactivity (93·5%) was achieved. The highest amounts of radioactivity were found in the butts and sidestream smoke. The two dominant compounds identified after smoking were unchanged parent compound and carbon dioxide. A total of 76% of the recovered radioactivity was identified. © 1998 SCI.     

The metabolism of [14C] cymoxanil in the rat

A rat, given a single oral dose of [¹⁴C] cymoxanil, 1-(2-cyano-2-methoxyimino-[2-¹⁴C]-acetyl)-3-ethylurea, eliminated 91% of the radioactivity within 72 h. The urine contained 71%, the faeces 11%, and the expired air about 7% of the radiolabel; no ¹⁴C residue was found in the internal organs. Greater than 70% of the radioactivity in the urine was identified. The major metabolite was characterised as glycine, both free and conjugated, as hippuric acid and phenylaceturic acid [N-(phenylacetyl)-glycine], and probably in the form of polypeptides of low molecular weight. The other metabolites identified included 2-cyano-2-methoxyiminoacetic acid, 2-cyano-2-hydroxyiminoacetic acid and 1-ethylimidazolidine-2, 4, 5-trione. The minor metabolites included succinic acid and 2-oxoglutaric acid which indicated reincorporation of metabolic ¹⁴C. Cymoxanil, as such, was not detected in the urine.     

Biological Activity of Two Stereoisomers of the N-Thienyl Chloroacetamide Herbicide Dimethenamid

Due to the presence of an asymmetrically substituted C atom, dimethenamid [2-chloro-N-(2,4-dimethyl-3-thienyl)-N-(2-methoxy-1-methylethyl)acetamide], a recently introduced N-thienyl chloroacetamide herbicide, exists as two stereoisomers (S and R) having differing herbicidal activities as demonstrated with a selection of weeds and Lemna minor. The activity of the two isomers was investigated in greater detail with the green alga Scenedesmus acutus and compared to that of alachlor [2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide]. As with alachlor, the S isomer (5 μM ) strongly inhibited algal growth and fatty acid desaturation while the R isomer had no effect. In short-term experiments (up to 5·5 h), the S isomer and alachlor (100 μM ) inhibited [¹⁴C]acetate uptake and its incorporation into fatty acids in the same manner, while the R isomer did not. Incorporation of [¹⁴C]acetate into a non-lipid fraction of the algae was strongly inhibited by alachlor and the S isomer (100 μM ) and only slightly by the R isomer. A 50% inhibition of incorporation of [¹⁴C]oleic acid into the same non-lipid fraction was attained with less than 10^-7 M of the S isomer while 10^-5 M of the R form of dimethenamid achieved only a 40% inhibition. The same stereospecificity of the compound on growth, fatty acid desaturation, acetate uptake and oleic acid incorporation provides strong evidence that dimethenamid may act upon a primary, specific target in lipid metabolism. Furthermore, the comparable biological activities of dimethenamid and alachlor indicate that this target is common to both N-phenyl and N-thienyl chloroacetamide herbicides. © 1997 SCI.     

The metabolism of the herbicide flamprop-isopropyl in barley

The metabolism of the wild oat herbicide, flamprop-isopropyl, [Barnon, isopropyl (±) N-benzoyl-N-(3-chloro-4-fluorophenyl)-2-aminopropionate] in barley grown to maturity has been examined under glass-house and outdoor conditions. [¹⁴C]Flamprop-isopropyl labeled separately in two positions was used. The major metabolic route of the herbicide was by hydrolysis to the corresponding carboxylic acid, II, which occurred in free and conjugated forms. Flamprop-isopropyl also underwent hydroxylation in the 3 and 4 positions of the benzoyl group, and the 3-hydroxybenzoyl analogue of II was detected. The hydroxylated metabolites were also present in the plants as conjugates. Additional minor metabolites detected only in glass-house samples were N-benzoyl-3-chloro-4-fluoroaniline, 2-[3-chloro-4-fluorophenylamino]-propionic acid, and benzoic acid. The soil in which the plants were grown received part of the spray application of the herbicide. Residues in the 0–10-cm layer at barley harvest comprised the unchanged herbicide, the carboxylic acid II, and unidentified polar material.     

The degradation of the herbicide benzoylprop-ethyl following its application to wheat

The herbicide benzoylprop-ethyl [SUFFIX,^a ethyl (±)-2-(N-benzoyl-N-3,4-di-chloroanilino) propionate] has been applied in a radiolabelled form to spring wheat and winter wheat growing both indoors and outdoors. During the application the compound also fell onto the soil. The plants and corresponding soils were examined at harvest at 71-98 days from treatment. Conversion of the herbicide occurred in plants and soil predominantly by a hydrolytic reaction to form benzoylprop^b followed in plants by its conjugation with sugars. Small amounts of N-benzoyl-3,4-dichloroaniline and benzoic acid were also detected in plants. There was no evidence for the presence of 3,4-dichloroaniline in the crops or soils nor was there evidence for 3,4,3′,4′-tetra-chloroazobenzene which has been implicated as a degradation product of some 3,4-dichloroaniline herbicides in soils. Residues on plants were greatest in the straw and consisted mainly of benzoylprop-ethyl and benzoylprop in free and conjugated forms. There was no evidence for appreciable movement of the compound within the plant from the treated foliage. Residues were particularly low in the grain and were not detected in the crop grown outdoors (limit of detectability 0.01 mg/kg). Residues in the soils were mainly in the 0-7.5 cm layer and there was no evidence for leaching below 15 cm.     

Degradation of the herbicide flamprop-isopropyl in soil under laboratory conditions

The degradation of the wild-oat herbicide flamprop-isopropyl, [isopropyl (±)-N-benzoyl-N-(3-chloro-4-fluorophenyl)alaninate], in four soils has been examined under laboratory conditions with sampling times of up to 45 weeks after treatment. The major degradation product of [¹⁴C]flamprop-isopropyl in all soils at up to 10 weeks after treatment was the carboxylic acid (±)-N-benzoyl-N-(3-chloro-4-fluorophenyl)alanine. This compound in turn underwent degradation by loss of the benzoyl group and the propionic acid moiety, with evolution of [¹⁴C]carbon dioxide to form 3-chloro-4-fluoroaniline (CFA). The CFA was formed slowly in soil and occurred mainly as a bound form. There was evidence to show that the CFA was subsequently converted into other polar products. The time for depletion of 50% of the applied herbicide was approximately 10 weeks in sandy loam and medium loam soils, 11 weeks in a clay loam soil and 23 weeks in a peat soil.     

The antifungal activity of some sulphonyl derivatives of isoxazole,pyrazole, thiazole and thiophene

Fifty-three heterocyclic sulphonyl derivatives including eight sulphonamides, three sulphonyl azides, nine sulphonohydrazides and twenty sulphonohydrazones of substituted thiophenes, and a smaller range of analogous isoxazoles pryazoles and thiazoles, were tested as potential fungicides in a simple screening procedure against Mucor mucedo, Septoria nodorum, Trichoderma viride, Chaetomium globosum and Aspergillus niger. Several thiophene-2-sulphonyl based compounds exhibited a high level of antifungal activity at 100 mg litre^?1 against the five test species, especially the mono-halogen-substituted sulphonamides and sulphonohydrazines, in which a single chlorine or bromine atom was substituted in the para position of an attached phenyl ring. The most active compound, against all five species of fungus was N-(4-chlorophenyl)-N-(trichloromethylthio) thiophene-2-sulphonamide which had average MIC₅₀ and MIC₁₀₀ values of 86 and 180 μmol respectively. (MIC₅₀ and MIC₁₀₀ values are, respectively, the concentrations required to inhibit fungal growth by 50% and to inhibit it totally.) In general, the isoxazole analogues of the thiophene-2-sulphonyl compounds exhibited a much lower fungitoxic activity, whilst the pyrazole and thiazole based compounds had little or no activity. Compared with the other results, the considerable activity shown by 4-[2′-(3,4-dichlorobenzylidene)hydrazinosulphonyl]thiophene-2-carboxylic acid was unexpected.     

新型含吡唑杂环邻氨基苯甲酰胺类化合物的合成与杀螨活性

以氯虫苯甲酰胺和氟虫腈的结构为基础,通过活性亚结构拼接的方法,设计合成了24个新型含吡唑杂环邻氨基苯甲酰胺类化合物,其结构经1H NM R、IR及APCI-M S表征。初步生物活性测试结果表明:化合物5-溴-N-[4-氯-2-甲基-6-(甲氨基甲酰基)苯基]-1-1-[2,6-二氯-4-(三氟甲基)苯基]-4-三氟甲基亚磺酰基-1H-吡唑-3-甲酰胺(5k)和5-溴-N-[4-溴-2-甲基-6-(甲氨基甲酰基)苯基]-1-[2,6-二氯-4-(三氟甲基)苯基]-4-三氟甲基亚磺酰基-1H-吡唑-3-甲酰胺(5l)在500 mg/L下对朱砂叶螨Tetranychus cinnabarinus的致死率为100%,但在100 mg/L下其致死率则分别降至30%和50%。所得结果可为邻氨基苯甲酰胺类化合物构效关系研究提供参考。     

Comparative effects of three isoxazole-urea herbicidal derivatives on the metabolism of enzymatically isolated soybean leaf cells*

The effects of the herbicide isouron and of its plant degradation products designated as metabolite l {N-[5-(1,1-dimethylethyl)-3-isoxazolyl]-N-methylurea} and metabolite 2 {N-[5-(1,1-dimethylethyl)-3-isoxazolyl]-urea} on the metabolism of enzymatically isolated leaf cells of soybean [Glycine max (L.) Merr., cv. Essex] were compared under laboratory conditions. Photosynthesis, protein synthesis, ribonucleic acid synthesis, and lipid synthesis were assayed by the incorporation of NaH¹⁴CO₃, [¹⁴C]-leucine, [¹⁴C]-uracil, and [¹⁴C]-acetate, respectively, into the isolated cells. Time-course and concentration studies included incubation periods of 30, 60, and 120 min and concentrations of 0.1, 1, 10 and 100 μM of the three herbicides. The urea derivative of isouron (metabolite 2) was the least active of the three compounds. The activity of the mono-methylated derivative of isouron (metabolite 1) was comparable to that of isouron and the sensitivity of the four processes to both chemicals decreased in the order: photosynthesis > ribonucleic acid synthesis > lipid synthesis > protein synthesis. The concentration of isouron that caused a 50% inhibition of photosynthesis of the isolated soybean leaf cells was calculated at 0.51 μM. The effects of isouron and metabolite 1 on photosynthesis, lipid and RNA synthesis appeared to be independent of incubation lime as maximal inhibition occurred within 30 min. Inhibition of protein synthesis by both chemicals was time-dependent, increasing in magnitude with concomitant increases in incubation time.