Biotransformations of photoheptachlor in the rat: I. Excretion,storage, and isolation of metabolites

Male and female rats injected with ¹⁴C-photoheptachlor (0.93 mg/kg, ip) voided 66.3 and 28.1% of the radioactivity, respectively, in 4 weeks. Fecal route of elimination was more important than the urinary in both sexes. Tissue distribution of the residues at the end of the 4-week period showed higher levels in females than in males and the main storage site was the adipose tissue. Eleven metabolites of photoheptachlor from feces and nine from the urine of treated rats were isolated, purified, and chromatographically characterized.     

The metabolism of chlorotoluron in the rat

The metabolic fate of ¹⁴C-labeled chlorotoluron, i.e., 1-(3-chloro-4-methyl[⁴C]-phenyl)-3,3-dimethyl urea, was followed in rats. After a single oral dose the radioactivity was preferably excreted with the urine. Nine of the eleven urinary metabolites isolated, were identified by spectroscopic and derivatization techniques, whereas the structure of the remaining two metabolites was only partially elucidated. N-Demethylation and stepwise oxidation of the ring methyl group to hydroxymethyl and carboxyl derivatives were found as the major metabolic mechanisms. Both mechanisms proceeded simultaneously so that the isolated metabolites showed all combinations of N-demethylation and ring methyl group oxidation in their structures. One of these metabolites was an N-formyl derivative, being probably an intermediate product of demethylation. In the urine of rats fed doses of [¹⁴C]chlorotoluron higher than 50 mg/kg three additional metabolites with different degrees of N-dealkylation were found, the ring methyl group of which was transformed to a methylthio methyl group. The metabolites identified in the faeces were of the same type as those found in the urine. Based on the structures of the metabolites elucidated, a metabolic pathway of chlorotoluron in the rat is presented.     

Mercapturic acid formation in the metabolism of propachlor,CDAA, and fluorodifen in the rat

When [¹⁴C]F₃-fluorodifen (2,4′-dinitro-4-trifluoromethyl diphenylether), carbonyl-[¹⁴C]CDAA (N,N-diallyl-2-chloroacetamide), and carbonyl-¹⁴C-propachlor (2-chloro-N-isopropylacetanilide) were fed to rats, 57 to 86% of the ¹⁴C was excreted via the urine within 48 hr. Although very little radioactivity was excreted in the feces of CDAA-treated rats, 15–22% of the ¹⁴C was excreted in the feces of propachlor- of fluorodifentreated rats and an average of 8% of the ¹⁴C remained in these rats 48 hr after treatment. Oxidation of the ¹⁴C label to [¹⁴C]O₂ was not a major process in the metabolism of these herbicides. The only major radioactive metabolite present in the 24-h urine of fluorodifen-treated rats, 2-nitro-4-trifluoromethylphenyl mercapturic acid, accounted for 41% of the administered dose of ¹⁴C. In the metabolism of CDAA, the corresponding mercapturic acid accounted for 76% of the dose; it was the only major metabolite present in the 24-h urine. In contrast, three major metabolites were detected in the 24-h urine of propachlortreated rats, and the mercapturic acid accounted for only 20% of the dose. The mercapturic acid of each herbicide was identified by mass spectrometry.     

The effect of impurities on the toxicokinetics of malathion in rats

The effect of the malathion impurities, isomalathion of O,S,S-trimethyl phosphorodithioate (OSS-Me), on the toxicokinetic behavior of [methoxy-¹⁴C]malathion in female rats was investigated. Malathion α- and β-monoacids and the diacid were the predominant metabolites in the blood of rats pretreated orally with corn oil followed 4 hr later with radiolabeled malathion. Pretreatment of rats with isomalathion or OSS-Me in corn oil followed by treatment with malathion resulted in a decrease of total radioactive metabolites in the blood. Moreover, a substantial reduction in the level of malathion β-monoacid and malathion diacid was observed in the blood of impurity pretreated animals. These results indicate that the impurities have a stronger effect in inhibiting carboxylesterases which preferentially hydrolyze the β-carboethoxy moiety of malathion. The major malathion metabolites excreted in the urine of pretreated and control rats generally matched those present in the blood. The potentiation of the acute toxicity of malathion by pretreatment with isomalathion or OSS-Me may be explained by the reduction in the rat's capacity to degrade malathion via carboxylesterase-catalyzed hydrolysis of the β-carboethoxy moiety.     

The toxicological significance of paraoxon deethylation

The in vivo formation of deethylation and hydrolytic products of paraoxon degradation after parathion or paraoxon administration was nearly equal in control male rats, and the relative abundance of metabolites was not appreciably altered by pretreatment of rats with enzymeinducing agents. However, pretreatment with inducers dramatically increased the oxidative paraoxon O-deethylase of male rat liver while having little effect on hydrolytic enzymes. Prior to induction, the hepatic O-deethylase activity was greatly inferior to the various hydrolytic enzymes, but nearly equal levels of both enzyme systems were found after induction. These results indicate that a large portion of the hepatic hydrolases detected in vitro is not active in vivo. It also appears that the majority of the induced hepatic deethylase was not involved in vivo at the dosage levels employed. The in vivo metabolism of monoethyl paraoxon was also demonstrated. The predominant metabolite of ethyl-[1-¹⁴C]monoethyl paraoxon is ¹⁴CO₂, while phenyl-[1-¹⁴C]monoethyl paraoxon yielded 4-nitro[1-¹⁴C]phenol. Paraoxon deethylation was also shown to be an important detoxication mechanism in female rats and male mice and must be considered in interpreting the toxicological properties of parathion and paraoxon.     

Metabolism of cisanilide (Cis-2,5-dimethyl-1-pyrrolidinecarboxanilide) by rat liver microsomes

Metabolism of [phenyl-¹⁴C] and [(2,5) pyrrolidine-¹⁴C] cisanilide was investigated in vitro with microsomal preparations from rat liver. Microsomal activity was associated with a mixed-function oxidase system that required O₂ and NADPH and was inhibited by CO. Two major ether-soluble metabolites were isolated. They were identified as primary oxidation products: 2-hydroxy-2,5-dimethyl-1-pyrrolidinecarboxanilide (A) and 4′-hydroxy-2,5-dimethyl-1-pyrrolidinecarboxanilide (B). Minor ether-soluble metabolites were also isolated. Precursor product studies and qualitative thin layer chromatography analysis of [pyrrolidine-¹⁴C] and methylated [phenyl-¹⁴C] hydrolysis products suggested that these metabolites were secondary oxidation products formed from metabolites A or B. One of these metabolites appeared to be the dihydroxy product 2,4′-dihydroxy-2,5-dimethyl-1-pyrrolidinecarboxanilide. Crude microsomal preparations (postmitochondrial supernatant fractions) also formed small quantities (<10%) of polar metabolites. Enzyme hydrolysis with β-glucuronidase (Escherichia coli) indicated that approximately 50% of these metabolites were glucuronides. Similarities and differences in cisanilide oxidation in vivo in plants and in vitro with rat liver microsomal preparations were discussed.     

Soybean shoot metabolism of isopropyl-3-chlorocarbanilate: Ortho and para aryl hydroxylation

This laboratory reported that isopropyl-3-chlorocarbanilate-phenyl-U-¹⁴C (chlorpropham-phenyl-¹⁴C) was absorbed, translocated, and metabolized by soybean plants. Both polar metabolites and insoluble residues were found in roots, whereas only polar metabolites were found in shoot tissues. In both roots and shoots the polar metabolites were shown to be the O-glucoside of isopropyl-2-hydroxy-5-chlorocarbanilate (2-hydroxy-chlorpropham). In shoot tissue there were other polar metabolites that were not identified. The experiments with soybeans have been repeated, but with new isolation and purification procedures. The plants were root treated with both chlorpropham-phenyl-¹⁴C and isopropyl-3-chlorocarbanilate-2-isopropyl-¹⁴C. The roots and shoots were extracted and separated into the polar, nonpolar, and insoluble metabolic components, using the Bligh-Dyer extraction method. The polar metabolites were separated by gel permeation chromatography. Further purification was accomplished on Amberlite XAD-2. The polar metabolites from the shoot and root tissues were hydrolyzed either by β-glucosidase or hesperidinase. The enzyme liberated aglycones were derivatized and separated by gas-liquid chromatography, and the components were characterized by mass spectrometry or NMR. The results of this study showed that the polar metabolites of soybean shoots were 2-hydroxy-chlorpropham and isopropyl-4-hydroxy-3-chlorocarbanilate (4-hydroxy-chlorpropham). These two hydroxy-chlorpropham metabolites were found in soybean shoots at a ratio of approximately 1:1. The only aglycone found in root tissue was 2-hydroxy-chlorpropham. Using the new procedures, no evidence was obtained for the presence of the unidentified polar metabolites that were previously observed in shoot tissues.     

Metabolism of N-hydroxymethyl dimethoate and N-desmethyl dimethoate in bean plants

N-Hydroxymethyl [carbonyl-¹⁴C] dimethoate (0.43 ppm) and N-desmethyl [carbonyl-¹⁴C] dimethoate (0.50 ppm) were stem-injected into bean plants (Phaseolus vulgaris) in two separate experiments. Plants were harvested periodically, extracted, fractionated, and analyzed for metabolites. The resulting pattern of metabolites formed from the administration of these two compounds was different. Radioactivity was not detected in the organic fraction 2 days after N-desmethyl dimethoate administration. N-Desmethyl dimethoate was rapidly broken down to dimethoate carboxylic acid and other polar metabolites, then further degraded into materials which became part of the plant constituents. N-Hydroxymethyl dimethoate was quite stable in the plant. Most of the material not remaining as parent became rapidly conjugated and constant levels of conjugate were maintained. Very little radioactivity was bound in the plant marc. The metabolic pathway of these compounds is as follows: N-hydroxymethyl to the glucoside or N-desmethyl derivative; the N-desmethyl metabolite degrades primarily to the carboxylic acid but also to N-desmethyl dimethoxon, either of which in turn may be degraded to dimethoxon carboxylic acid. The conversion of -NHCH₂OH to -NH₂ is a slow reaction so that conjugation becomes the route of choice when the plant is treated with N-hydroxymethyl dimethoate.     

Structure assignment to biologically produced malathion monocarboxylic acid isomers with 13C-nuclear magnetic resonance

Chemical synthesis of malathion α- and β-monocarboxylic acid yields a mixture of the two structural isomers. These two isomers were separated by preparative anion-exchange chromatography on QAE-Sephadex. ¹³C-Nuclear magnetic resonance of the pure components shows that the main product is the β-isomer, with the α-isomer being present in much smaller quantities. This result was used for identification of hydrolytic malathion metabolites produced by rat tissues. On incubation of malathion with rat liver fractions in vitro it was found that α- and β-monoacid are formed in a ratio of 3:2, whereas this ratio is 9:2 for the metabolites excreted into the urine after intraperitoneal injection of malathion in rats.     

The metabolism of p,p′-DDT by the feral pigeon (Columba livia)

Male feral pigeons were dosed with ring-labeled $\text{[}{}^{14}\text{C}\text{]p,p′-}\text{DDT}$ and the tissues and droppings analyzed for total ¹⁴C, extractable ¹⁴C, and metabolites. Only 16% of an intraperitoneal dose of 1.5–2.2 mg kg^?1 was voided in the droppings over 28 days; the rate of loss reached a maximum on the 14th day and then fell quickly away. The rate of removal of ¹⁴C in droppings was low in comparison to that found in the rat and the Japanese quail. When pigeons were dosed with 32–38 mg kg^?1 DDT per bird, and killed after 77 days, 5.4% of the dose was eliminated in droppings and 87% was recovered in the body. The tissues and droppings from this experiment were analyzed for DDT and its metabolites. Of the ¹⁴C remaining in tissues 88% was accounted for as the apolar compounds DDE, DDT, and DDD. Approximately half of the ¹⁴C in droppings was present as DDE, DDT, and DDD, whereas 27–35% was apparently in conjugated form, extractable from aqueous solutions by ethyl acetate after prolonged acid hydrolysis. Two polar metabolites were isolated from the acid-released material. One was p,p′-DDA; the other was extractable from aqueous solution at pH 8 and was tentatively identified as a monohydroxy derivative of p,p′-DDT. DDE accounted for 93% of the ¹⁴C present as metabolites in tissues and droppings, clearly indicating the importance of this intermediate in this study. The metabolism of DDT in the feral pigeon is discussed in relation to its metabolism by other species.     

Fate of endosulfan in rats and toxicological considerations of apolar metabolites

[¹⁴C]Endosulfan, α or β isomers separately, was administered to rats as a single oral dose and as a dietary supplement for 14 days. No appreciable differences were observed in the fate of the two isomers. Five days after the single dose, 75% of the dose had been voided in the feces and 13% in the urine. Of the total radiocarbon consumed in the diet after 14 days, 56% had been eliminated in the feces and 8% in the urine. Bile collection studies showed that up to 47% of a single oral dose was eliminated from the liver via this route; enterohepatic circulation was not apparent. Maximum [¹⁴C]endosulfan equivalents in body tissue occurred in the kidney and liver, 3 and 1 ppm, respectively, after 14 days of feeding 5 ppm of endosulfan. Apolar metabolites in the excreta and/or tissues were a minor portion of the total residues and consisted of the sulfate, diol, α-hydroxy ether, lactone, and ether derivatives of endosulfan. The sulfate was slightly more toxic to mice than endosulfan, while the other products were less toxic. Neither endosulfan nor its metabolites were active in the Salmonella mutagenicity test. Endosulfan in the diet of rats for 28 days at 50 ppm did not induce liver oxidase enzymes, alter liver or kidney weights, or influence the rate of weight gain of the animals.     

The metabolism of DDT in vivo by the Japanese quail (Coturnix coturnix japonica)

Male and female Japanese quail (Coturnix coturnix japonica) were given intraperitoneal injections of [¹⁴C]DDT in ethanol at a rate of 13.4 mg/kg body wt. Fifty-six days later the tissues and droppings were analysed for total ¹⁴C and metabolites. The rate of loss of ¹⁴C in droppings was very similar in males and females. The maximal rate was reached on the third day, and 65–66% of the injected dose was voided by the fifty-sixth day. Ninety-three to ninety-four percent of the ¹⁴C in droppings and 83–90% of the ¹⁴C in tissues were extracted by solvents. Combined extracts from males and females were used for determination of DDT and its metabolites. Expressing all results as percentages of injected dose, the following were isolated from droppings: DDA (24%), DDT (3%), DDD (5.1%), DDE (11%), and uncharacterised polar metabolites (17%). Twenty-five percent of the dose was retained in the tissues and this was largely accounted for as DDT (10.4%) and DDE (10.5%). Of the total metabolites found 31% was DDE (almost equally divided between tissues and droppings) and 35% was DDA (almost entirely in droppings). Since DDD was not found in significant quantities in tissues, the substantial quantities in droppings were probably produced from DDT by the action of microorganisms.     

Metabolism of methfuroxam (2,4,5-trimethyl-N-phenyl-3-furancarboxamide) in the rat and isolated rat hepatocytes

Isolated rat hepatocytes were incubated for 4 hr with [phenyl-U-¹⁴C]2,4,5-trimethyl-N-phenyl-3-furancarboxamide ([¹⁴C]methfuroxam). ¹⁴C-Labeled metabolites were isolated by solvent extraction, column chromatography, and high-pressure liquid chromatography, and were then characterized by analysis of infrared and mass spectra. Metabolism of [¹⁴C]methfuroxam by isolated hepatocytes included: (1) hydroxylation of the 2-, 4-, and 5-methyl groups on the furan ring; (2) hydroxylation at the para position of the benzene ring; (3) combinations of 1 and 2; (4) the addition of a sulfur-containing adjunct to the methylfuran moiety; and (5) conjugation of 1–4. Rats given a single intragastric dose of [¹⁴C]methfuroxam excreted 56% of the ¹⁴C in the urine and 42% in the feces within 54 hr. Metabolism of [¹⁴C]methfuroxam by the intact rats included: (1) hydroxylation of the methylfuran moiety; (2) hydroxylation of the benzene ring; (3) the addition of S-methyl, methyl sulfoxide, and other sulfur-containing groups to methfuroxam; (4) combinations of 1–3; and (5) conjugation of 1–4.     

Herbicide perfluidone (1,1,1-trifluoro-N-[2-methyl-4-(phenylsulfonyl)phenyl]methanesulfonamide): Its metabolism in rats and chickens

Rats and chickens were each given a single oral dose (10 or 100 mg/kg body wt) of 1,1,1-trifluoro-N-[2-methyl-4-(phenylsulfonyl)phenyl-¹⁴C(U)]methanesulfonamide ([¹⁴C]perfluidone). Depending on the size of the dose, from 8.4 to 36.2% of the [¹⁴C] was eliminated in the urine and from 36.4 to 85.4% was eliminated in the feces within 48 hr after dosing. Less than 1% of the [¹⁴C] given to laying hens as [¹⁴C]perfluidone was present in the eggs produced during the first 96 hr after dosing. The percentage of the administered [¹⁴C] that remained in these animals (body with G.I. tract and contents removed) varied from 0.34 (96 hr after dosing) to 1.68% (48 hr after dosing). ¹⁴C-labeled compunds in the urine and feces from the rats and chickens were purified by solvent extraction, column chromatography, and gas-liquid chromatography, and then identified by infrared and mass spectrometry. The parent compound was the major ¹⁴C-labeled component in the urine and feces of both animals. 1,1,1-Trifluoro-N-[2-methyl-4-(3-hydroxyphenylsulfonyl)phenyl]methanesulfonamide was present in the feces of both animals. The proposed structures of other metabolites were 1,1,1-trifluoro-N-hydroxy-N-[2-methyl-4-(phenylsulfonyl)phenyl]methanesulfonamide (rat urine) and 1,1,1-trifluoro-N-{2-methyl-4-[(methylsulfonyl)-phenylsulfonyl]phenyl}methanesulfonamide (chicken urine).     

Biliary secretion of 14C and identification of 5,6-dihydro-5,6-dihydroxycarbaryl glucuronide as a biliary metabolite of [14C]carbaryl in the rat

The biliary secretion of ¹⁴C was observed in conscious, bile-fistulated rats given single oral doses of [¹⁴C]carbaryl (1.5, 30, and 300 mg/kg). Over 94% of the ¹⁴C was absorbed after 12 hr. From 15 to 46% of the ¹⁴C was secreted in bile, 10–40% in urine, and less than 1% in feces 12 hr after dosing. Three metabolites were isolated from bile and identified by mass and/or NMR spectrometric methods. These metabolites were: 5,6-dihydro-5,6-dihydroxycarbaryl glucuronide (12–18% of the biliary ¹⁴C), a conjugate(s) of carbaryl (12% of the biliary ¹⁴C), and conjugated isomers of hydroxy-carbaryl (2% of the biliary ¹⁴C). The majority of the biliary ¹⁴C remains to be identified.     

Conversion of the aldrin/dieldrin metabolite dihydrochlordene dicarboxylic acid-14C in rats

Upon intravenous application of dihydrochlordene dicarboxylic acid-¹⁴C to rats, the radioactivity is quickly excreted, and 44% of the excreted radioactivity consists of metabolites. Nine metabolites have been isolated from feces and urine extracts. Three metabolites could be identified by means of authentic samples by thin layer chromatography, gas chromatography, and mass spectrometry: two isomers of dechlorodihydrochlordene-dicarboxylic acid (metabolites I and II, total 22.5%) and dihydrochlordene-dicarboxylic acid-dimethyl-ester (metabolite III, 11.3%).     

Mechanism of resistance to fenarimol in Aspergillus nidulans

Mycelial uptake of [¹⁴C]fenarimol (10 μg/ml) by 20 fenarimol-resistant mutants of Aspergillus nidulans was compared with uptake by wild-type strain 003. Uptake of the fungicide during the initial 10 min of incubation was significantly lower in all mutant strains than in the wild-type strain indicating that resistance is related with reduced uptake. Upon prolonged incubation a gradual decrease of accumulated radioactivity in the wild-type strain was observed. A few mutants displayed resistance to unrelated chemicals such as p-fluorophenylalanine or d-serine; this phenomenon appeared not to be due to a decreased uptake of the corresponding natural amino acids. Incorporation of [³H]adenine and [¹⁴C]leucine by mycelium of mutant M193 was hardly inhibited after 5 hr of incubation with the fungicide, whereas a distinct effect was found with the wild-type strain. At this time also fungitoxicity to the wild-type strain became apparent. Probably, this effect is indirectly caused by inhibition of ergosterol biosynthesis. Mycelium of mutant M193 incorporated [¹⁴C]acetate slightly less effectively than the wild-type strain. After 2 hr of incubation with this radiochemical leakage of [¹⁴C]acetate metabolites from mycelium of the mutant strain was observed. This indicates that resistance might be correlated with increased excretion of fungal metabolites, which in turn may be related with reduced fitness of fenarimol-resistant mutants.     

Metabolism of EPTC in germinating corn: Sulfone as the true carbamoylating agent

Corn (Zea mays L. single cross hybrid Mv 620) was germinated in a petri dish with addition of carbonyl[¹⁴C]EPTC (S-ethyl-N,N-dipropylthiocarbamate). The shoots and roots of 4-day-old seedlings were crushed and extracted in 80% methanol. On the chromatogram of the extract three radioactive peaks were found. The main peak was identified as S-(N,N-dipropylcarbamoyl)-glutathione. For the comparison of carbamoylating ability [¹⁴C]EPTC, [¹⁴C]EPTC-sulfoxide, and [¹⁴C]EPTC-sulfone were incubated with glutathione. Only EPTC-sulfone reacted in the 10-day incubation time. In aquatic solutions EPTC and EPTC-sulfoxide proved to be stable during the 10 days compared to EPTC-sulfone which quickly degraded, S-(N,N-Dipropylcarbamoyl)-glutathione was converted to S-(N,N-dipropylcarbamoyl)-cysteine in corn shoot homogenate. [¹⁴C]EPTC, [¹⁴C]EPTC-sulfoxide and [¹⁴C]EPTC-sulfone were added to corn shoot homogeneates and each of the three mixtures were analyzed by chromatography after 1 day incubation. EPTC was partly oxidized to EPTC-sulfoxide. EPTC-sulfoxide did not change and EPTC-sulfone produced similar metabolites as had been found in the germination experiment.     

Animal metabolism of propham (isopropyl carbanilate): The fate of residues in alfalfa when consumed by the rat and sheep

Alfalfa was root-treated with [¹⁴C]propham (isopropyl carbanilate[¹⁴C-phenyl(U)]) for 7 days and then harvested and freeze-dried. Rats and sheep were orally given either ¹⁴C-labeled alfalfa roots ([¹⁴C]root) or ¹⁴C-labeled alfalfa shoots ([¹⁴C]shoot). When the [¹⁴C]root was given, 6.5–11.0% of the ¹⁴C was excreted in the urine and 84.6–89.4% was excreted in the feces within 96 h after treatment. Less than 3% of the ¹⁴C remained in the carcass (total body—gastrointestinal tract and contents) 96 h after treatment. When [¹⁴C]shoot was given, 53.2–55.2% of the ¹⁴C was excreted in the urine, 32.1–43.4% was excreted in the feces, and the carcass contained 0.2–1.1% of the ¹⁴C 96 h after treatment. When the insoluble fraction (not extracted by a mixture of CHCl₃, CH₃OH, and H₂O) of both alfalfa roots and shoots was fed to rats, more than 86% of the ¹⁴C was excreted in the feces and less than 3% remained in the carcass 96 h after treatment. The major radiolabeled metabolites in the urine of the sheep fed ¹⁴C shoot were purified by chromatography and identified as the sulfate ester and the glucuronic acid conjugates of isopropyl 4-hydroxycarbanilate. Metabolites in the urine of the sheep treated with [¹⁴C]root were tentatively identified as conjugated forms of isopropyl 4-hydroxycarbanilate, isopropyl 2-hydroxycarbanilate, and 4-hydroxyaniline. The combined urine of rats dosed with [¹⁴C]shoot and [¹⁴C]root contained metabolites tentatively identified as conjugated forms of isopropyl 4-hydroxycarbanilate, isopropyl 2-hydroxycarbanilate, and 4-hydroxyaniline.     

Metabolism of dibutyl-14C-labeled dibutylaminosulfenyl derivative of carbofuran in the cotton plant

The fate of the di-n-butylaminosulfenyl moiety in 2,3-dihydro-2,2-dimethyl-7-benzofuranyl (di-n-butylaminosulfenyl)(methyl)carbamate (DBSC or Marshal) was studied in the cotton plant at 1, 3, 6, and 10 days following foliage treatment with [di-n-butylamino-¹⁴C]DBSC. Dibutylamine and two major radioactive metabolites were obtained following extraction of the plant tissue with a methanol-buffer containing N-ethylmaleimide (NEM), a sulfhydryl scavenger which was added to prevent the cleavage of the NS bond during the workup procedure. The most adundant radioactive material recovered from plants was identified as a product arising from the reaction between NEM and dibutylamine. Extraction of plant tissue with straight methanol-buffer solution or with methol-buffer containing other sulfhydryl scavengers resulted in 57–86% of the applied radioactivity being recovered as dibutylamine in the organosoluble fraction. When [¹⁴C]dibutylamine was applied to cotton leaves, most of the radioactivity, i.e., 96% of the total recovered radioactivity, was found in the organosoluble fraction as dibutylamine. Dibutylamine is the major metabolite of [di-n-butylamino-¹⁴C]DBSC in the cotton plant.