• Korean Journal of Environmental Agriculture
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• v.21 no.1
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• pp.57-68
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• 2002

In order to elucidate the effect of phenobarbital sodium (PB) and 3-methylcholanthrene (3-MC) on metabolism of insecticide carbofuran in rat. Carbofuran metabolites and its formation rates were determined when orally administered $^{14}C$-carbofuran alone and its combination with PB or 3-MC to rat. $^{14}C$-carbofuran administered orally, alone or in combination with PB or 3-MC, was secreted rapidly within 48 hrs. That is, 79.9 to 81.1% of the original radioactivity was secreted into the urine and 5.7 to 6.5% into the feces. The secretion rate was faster in the combined administration than that in carbofuran alone. Metabolites of carbofuran in main organs, urine, feces and blood of rat were largely 3-hydroxycarbofuran, 3-ketocarbofuran, 3-hydroxycarbofuran phenol, 3-ketocarbofuran phenol, and carbofuran phenol, the major ones being 3-hydroxycarbofuran and 3-ketocarbofuran, respectively, in all administrations of carbofuran alone, carbofuran+PB and carbofuran+3-MC. In addition, formation rate of the two major metabolites detected in the urine was 17.4% and 12.8%, respectively, when carbofuran alone was administered. Meanwhile, when carbofuran was administered with PB or 3-MC, they were 8.6% and 23.5, repectively. These results indicate that the oral administration of PB or 3-MC can reduce carbofuran toxicity by fastening and stimulating the carbofuran metabolism in rat.

• The Korean Journal of Pesticide Science
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• v.3 no.2
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• pp.37-46
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• 1999

In order to ascertain the safety of the systemic insecticide carbofuran-treated crops, samples of garlic, peanut and potato were collected randomly from markets located in the main producing areas and analyzed for the residue of carbofuran and its main metabolite, 3-hydroxycarbofuran. The in vitro metabolism of carbofuran in phosphate buffer extracts of the crops was investigated. Two (M-12 and M-16) out of 20 mature garlic samples contained 0.13 and 0.07 mg/kg of carbohran, respectively, showing a detection incidence of 10%. The residue levels were less than the maximum residue limit (0.5 ppm) set by Korean Food and Drug Administration. Only one sample of mature garlic (M-12) out of 20 contained 0.13 mg/kg of 3-hydroxycarbofuran. The residues of carbofuran and 3-hydroxycarbofuran in the immature garlic, peanut and potato samples were less than the detection limits, 0.02 mg/kg for carbofuran and 0.06 mg/kg for 3-hydroxycarbofuran. The application of carbofuran to the fields of garlic, peanut and potato would be safe, considering that the estimated maximum acceptable daily intake of carbofuran from garlic was 0.0013 mg which is 0.24% of the maximum acceptable daily intake (0.55 mg). Carbofuran was hydrolyzed in vitro mainly to carbofuran phenol (m/z 164) in the respective phosphate buffer extracts of the three crops in contrast to the major oxidative metabolism in situ. The amount of the metabolite increased with the incubation time.

• The Korean Journal of Pesticide Science
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• v.2 no.2
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• pp.75-82
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• 1998

This study was conducted to find out the biochemical or metabolic resistance mechanism of brown planthopper (BPH) to carbofuran. Differences between resistant ($LD_{50};\;20.3{\mu}g/g$) and susceptible strains($LD_{50};\;0.3{\mu}g/g$) were shown. The amounts of carbofuran metabolite, benzofuranol, and the origin, not developed by Thin Layer Chromatography, were much more in the susceptible strain. But the mother compound, carbofuran, was much more in the resistant strain. The tendencies of metabolism one and three hours after treatment were similar in both strains except for the amounts of metabolites described above. From the study, it is supposed that hydrolytic enzyme, esterase, changes its role from cleaving the esteric bond of carbofuran to making conjugates with carbofuran. This seems to be the main resistance mechanism of BPH to carbofuran. Oxidase and transferase may play little or no role in resistance mechanism. Oxidative and transferring enzymes gave no effects on the metabolism of carbofuran in the resistant strain compared with the susceptible strain.

• The Korean Journal of Pesticide Science
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• v.2 no.2
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• pp.29-38
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• 1998

In order to elucidate the effect of phenobarbital sodium(PB) and 3-methylcholanthrene(3-MC) on metabolism in vitro and toxicity of $^{14}C$-carbofuran in rat, they were administered by the chemicals, alone or in combination, and their survival ratios and metabolites were investigated. The $LD_{50}$(96 hrs) value of carbofuran to rats was 6.9 mg/kg. The toxicities of the major metabolites were in the decreasing order of 3-hydroxycarbofuran, 3-ketocarbofuran, 3-hydroxycarbofuran phenol and were much lower than that of the parent compound. When the rats were orally administered by the dose of carbofuran alone, 8.4 mg/kg, the survival ratio was 0%, whereas that was raised up to $60{\sim}80%$ with 20 mg/kg of PB or 3-MC, and 100% with 60 mg/kg of PB or 3-MC. Their metabolism in vitro occurred in the microsomal fraction. In case of carbofuran alone, the major metabolite was 3-hydroxycarbofuran. When carbofuran with PB or 3-MC, on the other hand, was treated, it was 3-ketocarbofuran. In addition, when the co-factor(NADP+G-6-P+G-6-P-DG) was added to the microsomal fraction(phase I system), and a mixture of NADPH+GSH to the 105,000g supernatant(phase II system) taken by carbofuran alone, each metabolites were produced by the maximum levels, respectively. In case of the carbofuran treatment with PB or 3-MC, the microsomal fraction of phase I system produced the maximum levels of metabolites, as in the treatment of carbofuran alone, whereas the 105,000g supernatant supplemented with the co-factor NADPH+FAD(phase II system) was brought about the maximum production of metabolites. The ratio of the formation of metabolites was 2 to 3 times higher in the combined treatment of carbofuran with PB or 3-MC than in the treatment of carbofuran alone.

• Korean Journal of Environmental Agriculture
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• v.5 no.2
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• pp.85-94
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• 1986

To study fate of carbofuran in paddy system, C-14 labelled carbofuran was applied to paddy water containing rice seedlings and time course study was made on the distribution, metabolism and chemical transformation of the systemic insecticide. Carbofuran was readily absorbed by plant root and translocated to shoots where most of the radioactivities were confined to leaf tips. The fact that gradual increases in radioactivities of both aqueous phase extracts and non-extractable fractions of plants (shoots and root) increased with incubation is taken as an evidence that reactions (phase I and II) proceed in rice plants. Carbofuran and its five metabolites were all detected by TLC in organic phase extracts of paddy plants or soil. Evidence was put forward that carbofuran and its five metabolites were all identified as aglycones of conjugates. 7-benzofuranol and 3-hydroxycarbofuran were the most abundant aglycones. Soil microbes appears to have little effects on the metabolism of carbofuran. They increased radioactivity of non-extractable fraction and reduced that of organic phase extracts of paddy soil.

• Korean Journal of Environmental Agriculture
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• v.16 no.1
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• pp.25-30
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• 1997

Absorption, distribution, metabolism and excretion of $^{14}C-carbofuran$(2,3-dihydro-2,2-dimethyl-7-benzofuranyl methylcarbamte) were studied in carp(Cyprinus carpio L.) after the treatment of carbofuran at the dose level of 43 parts per billion. Maximum radioactivities in tissues(liver, kidney, gut, gall bladder) and blood of carp were shown 12hrs after the treatment of $^{14}C-carbofuran$. Carbofuran was metabolized to 3-hydroxycarbofuran and 3-ketocarbofuran in liver and kindney of carp, and the major metabolite was 3-hydroxycarbofuran. Most radioactivity absorbed into the carp tissues was eliminated 3hrs after transfer of the carp to fresh water. The excretory metabolites were 3-ketocarbofuran(32.3%), 3-hydroxycarbofuran(52.8%) and an unknown metabolite(2.6%) during the period of 3hrs of the excretory experiment.

• Korean journal of applied entomology
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• v.30 no.1
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• pp.10-17
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• 1991

Cuticular penetration and detoxication as mechanisms of resistance to the carbamate insecticides in fenobucarb-selected($R_{f}$) and carbofuran-selected($R_{c}$) strains of the brown planthopper (N. lugens Stal) were investigated. Rates of penetration were not significantly different in the susceptible and resistant strains. However, total amount of excretion of the $R_{f}$ and $R_{c}$ strains were much larger than that of the susceptible strain. Fenovucarb and carbofuran were in vivo metabolizd much faster in the $R_{f}$ strain than in the susceptible strain. OSBP(o-sec-butyl phenol) and 3-ketocarbofuran phenol were invitro the major metabolites of fenobucarb and carbofuran in the brown planthopper, respectively. Total amount of the two major metabolites were produced abotu 2 times larger in the $R_{f}$ and $R_{c}$ strains compared to the susceptible strain. OSBP and 3-ketocarbofuran phenol were not so toxic to the brown planthopper ($LD_{50}$ >100 $\mu\textrm{g}$/g hopper). Based on our data, detoxication plays a large role in resistance to fenobucarb and carbofuran in the resistant strain of BPH, although several resistance factors maybe involved.

• Korean Journal of Environmental Agriculture
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• v.6 no.1
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• pp.7-16
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• 1987

A study was undertaken to investigate the absorption, translocation and metabolism of carbofuran in rice paddies. Ring-3-$^{14}C-carbofuran$ applied onto the paddy soil surface was rapidly absorbed and translocated into rice plants. Within 2 days after treatment, it was observed that carbofuran reached shoot tips and accumulated. More than 15% of total radioactivity was recovered in rice plant from 3 to 20 days after treatment. In organic soluble fraction of rice plant extract, 3-hydroxycarbofuran was the major metabolite recording 43% and 4% of total organic soluble radioactivity in shoot and root at 20 days respectively. 3-Ketocarbofuran and phenolic metabolites including carbofuran phenol, 3-hydroxycarbofuran phenol and 3-ketocarbofuran phenol were also detected in the organic soluble fractions. Some glycosidic conjugates of carbofuran metabolites were found in water soluble fraction of rice plant extract and 3-hydroxycarbofuran was the most abundant aglycone. Radioactivity in paddy soil was rapidly decreased until 3 days after treatment and then maintained almost constant level. A significant portion (42∼56 %) of the total radioactivity remained in soil as nonextractable residue from 5 to 20 days after treatment. The nonextractable radioactivity was mainly located in soil organic matter distributing in humin, fulvic acid and humic acid fractions with the decreasing order. Evolution of $^{14}CO_2$ from ring cleavage of $3-^{14}C-carbofuran$ was negligible recording only 1.8% of total radioactivity during 20 days after treatment.

• The Korean Journal of Pesticide Science
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• v.11 no.3
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• pp.179-185
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• 2007

Esterase isozymes were investigated from digestive juice of M. saltuarius adults after pesticide treatment. Twelve esterase isozymes were separated on 12% native-PAGE gel and stained with three different substrates(${\alpha}$-naphthyl acetate, ${\beta}$-naphthyl acetate, and ${\alpha}$-naphthyl butyrate). Interestingly, the isozyme of Est1(${\alpha}$-naphthyl acetate) was strongly inhibited by the carbofuran and methomyl. The Est1 activity was completely inhibited by the chlorpyrifos and partially inhibited by methidation about 70 %. In addition, eserine suppressed esterase isozyme activities of Est1 about 70% and isozyme activities of Est2, Est3, and Est4 were weakly inhibited. ${\alpha}$-pinene did not suppressed esterase isozyme activities but activities of esterases were very weakly inhibited in camphor and bornyl acetate.

• Korean Journal of Environmental Agriculture
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• v.26 no.4
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• pp.351-363
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• 2007

The scientific articles using radio labelled insecticides performed by Korean researchers were reviewed. The research works were divided into 4 categories such as soil, plant, animal and insect. All researches used $^{14}C$-labelled chemicals, and the $^{14}C$-carbofuran was widely used among them. Fate of insecticides, bound-residues and metabolic process were staple concerning area in soil study. And the uptake and translocation, metabolism and metabolites also a major interests in plant study. As well as the degradation, metabolic pathway and metabolites, and distribution of chemicals in animal tissue were another point of consideration in animal study. And finally, the penetration ratio into body and resistant mechanism were the major concerning views of study with insects.