• The Korean Journal of Pesticide Science
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• v.9 no.1
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• pp.97-101
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• 2005

Flupyrazofos (O,O-diethyl O-1-phenyl-3-trifluoromethylpyrazo-5-yl phosphorothioate) is an organophosphorus insecticide with a pyrazole moiety which is newly developed and commercialized by SUNGBO chemical company and Korean Research Institute of Chemical Technology for effectively control against diamond back moth. This study was conducted to determine the composition and quantity of impurities in technical 1 (94.5%), technical 2 (97.6%) and purified (99.2%) flupyrazofos using GLC/MSD. Bimolecular inhibition rate constant($k_i$) with acethylcholinesterase (in vitro) and $I_{50}$ with mouse brain acetylcholinesterase (in vivo) were measured for comparing inhibitory patterns of two technicals and purified flupyrazofos. Impurities of flupyrazofos were identified as O,O,O-triethylthio-phosphoric acid (TEA), 1-phenyl-3-trifluoromethyl-5-ethoxy pyrazole(PTMEP), O,O-diethyl O-1-phenyl-3-trifluoromethylpyrazo-5-yl phosphoric acid ester(flupyrazofos oxen), O,S-diethyl O-1-phenyl-3-trifluoromethylpyrazo-5-yl phosphorothionate (S-ethyl flupyrazofos). In in vitro, technical 1 showed the fastest inhibition on AChE activity among them. And technical 1 and 2 showed 40% higher in vivo inhibition against mouse brian AChE than purified flupyrazofos did. These results could be caused by the impurities such as flupyrazofos oxen and S-methyl flupyrazofos contained in technical grades of flupyrazofos.

• The Korean Journal of Pesticide Science
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• v.6 no.3
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• pp.224-229
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• 2002

In vivo metabolism study was carried out to find out the biochemical or metabolic tolerance mechanism between Diamond backmoth (DBM), Plutella xylostella and Beet armywarm (BAW), Spodoptera exigua to flupyrazofos. They showed some differences between the DBM and BAW. About 20% of flupyrazofos applied to the 3rd instar larvae of DBM was metabolized within 1 h and about 50% of that was metabolized within 4 h. The metabolites of flupyrazofos-oxon in 3rd instar larvae of DBM were increased 10 times more at 4 h than 1 h after application. The amounts of flupyrazol were nearly same between at 1 h and 4 h. The amount of unknown and origin increased 2 and 3 times more at 1 h than 4 h after application, respectively. In the 4th instar BAW larva, about 50% of flupyrazofos was metabolized within 1 h and about 70% of that was metabolized within 4 h. As metabolites, the amounts of flupyrazofos-oxon increased 2 times more at 4 h than 1 h after application. The amounts of flupyrazol increased 4 times more at 4 h than 1 h after application. The amount of unknown and origin increased 2.5 and 2 times more at 4 h than 1 h after application, respectively. From the study, it is supposed that hydrolytic enzyme, esterase, cleave the alkyl bond of flupyrazofos and conjugates with flupyrazofos. This seems to be the main tolerance mechanism of BAW to flupyrazofos.

• The Korean Journal of Pesticide Science
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• v.2 no.3
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• pp.117-125
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• 1998

Flupyrazofos (O,O-diethyl-O-(1-phenyl-3-trifluoromethyl-5-pyrazoyl)thiophosphoric acid ester) is a new organo-phosphorous insecticide. Flupyrazofos has exhibited excellent activity against diamondback moth (Plutella xylostella, DBM), and it is highly activity against rice armyworm(Pseudaleta separata) and cotton caterpillar(Palpita indicae). Flupyrazofos has then revealed outstanding both rapidity and residual action for DBM, although no systemic actions were observed and no cross-resistances were found to the resistance strains (Op-R, Py-R, IGR-R). Also, susceptibilities of five local strains to flupyrazofos were similar to those of the susceptible strain. These results indicate that flupyrazofos has considerable potential for controlling diamondback moth, rice armyworm and cotton caterpillar in field.

• Applied Biological Chemistry
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• v.43 no.2
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• pp.130-135
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• 2000

Photodegradation rate of flupyrazofos in aqueous solution were measured under various test conditions mainly following the guidelines of U.S. EPA and OECD. It was observed that the flupyrazofos was degraded by simple hydrolysis but not degraded by light in pure water. Using acetone as a known photosensitizer, the minimal concentration of acetone needed to photo-degrade the flupyrazofos in % and molar terms were 0.047% and 0.006, respectively. When treated with acetone, it was also found that the ringlet oxygen is a very effective photo oxidant in the degradation of flupyrazofos, but the effect of hydroxyl radical was not observed at the treatment level of hydroxyl radical, isopropylbenzene. In an actinometer experiment, quantum yield of flupyrazofos (0.4 ppm with 2% acetone) was $17.66{\times}10^{-5}$ and degradation rate and half-life were 0.038/hr and 18.2 hours, respectively.

• The Korean Journal of Pesticide Science
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• v.7 no.1
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• pp.18-24
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• 2003

The activities of esterase and acetylcholinesterase(AChE) on the Diamond backmoth (DBM), Plutella xylostella (Lepidoptera: Yponomeutidae) and Beet armywarm (BAW), Spodoptera exigua (Lepidoptera: Noctuidae) and inhibitions of AChE with flupyrazofos were clarified from the results of a series of experiments. These findings are described in brief as follows. The AChE activities of DBM and BAW in heads were $1.5{\sim}11.1{\mu}$mol/g/min in $1st{\sim}4th$ instar larvae of DBM and $1.7{\sim}45.2{\mu}$mol/g/min in $1st{\sim}6th$ instar larvae of BAW, respectively. Those were $25{\sim}30$ times higher in above 4th instar larvae of BAW than that of the 1st instar larvae of DBM. The activities of aliesterase in heads were $1.7{\sim}4.7$ times higher in $2nd{\sim}4th$ instar larvae of DBM and $8{\sim}55$ times higher in $3rd{\sim}6th$ instar larvae of BAW than 1st instar larvae of DBM. In abdomens, those were $3{\sim}17$ times higher in $2nd{\sim}4th$ instar larvae of DBM and $12{\sim}30$ times higher in $3rd{\sim}6th$ instar larvae of BAW than 1st instar larvae of DBM. Median AChE inhibition concentration $(I_{50})$ of flupyrazofos to the 2nd instar larvae of DBM and BAW were 92 nM and $15{\mu}M$, respectively, and those to the 4th instar larvae of DBM and BAW were $1.8{\mu}M$ and 3.1 mM, respectively. Insensitivity ratio of flupyrazofos in the 2nd instar BAW larvae showed ca. 162 times higher than that in the 2nd instar larvae of DBM, and that of the 4th instar BAW larvae showed ca. 1,720 times higher insensitivity to flupyrazofos than that of the 4th instar DBM larvae. AChE activities in the 2nd instar larvae of DBM and BAW at 32 h after applicaton of flupyrazofos decreased from 67.6% to 32.4% of the activity of the untreated control. That of the 4th instar larvae of DBM increased for 0.5 h after application flupyrazofos up to 75% of the untreated control, and after that it decreased to 34.5% of the untreated control at 32 h. In contrast, in the 4th instar larvae of BAW AChE activities increased for 8 h gradually up to 102 % of the activity of the untreated control, and then the activity decreased to 97% of the untreated control at 16 h after treatment.

• The Korean Journal of Pesticide Science
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• v.4 no.1
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• pp.44-50
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• 2000

Tolerance mechanism to flupyrazofos was examined with Plutella xylostella (L.) and Spodoptera exigua by investigating the penetration rate of flupyrazofos into larvae body. On determining effective washing of $^{14}C$-flupyrazofos, the washing volume to recover over 98% of $^{14}C$-flupyrazofos was observed at three times (each time: 1 mL). To select a suitable solvent, the recovery rates of each solvent in 3rd instar larvae of DBM were above 98%, but the washing rates of acetone, hexane and ethyl-acetate were 85.1%, 67.2% and 68.4%, respectively. In the BAW larvae, although the recovery rates of each solvent were above 99%, the washing rates of acetone, hexane and ethyl-acetate were 83.5%, 65.9% and 71.7%, respectively. The $PT_{50}$ values of $^{14}C$-flupyrazofos were 0.731 h (44 min) in the DBM larva and 0.504 h (30 min) in the BAW larva. Radiocarbon in acetone washing (external fraction) decreased more quickly in the BAW larva than in the DBM larva, and amount of radiocarbon in larvae body increased more quickly with time in the DBM larva than in the BAW larva. In contrast, amount of radiocarbon in excreta increased more rapidly with time in the BAW larva than in the DBM larva.

• The Korean Journal of Pesticide Science
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• v.6 no.3
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• pp.218-223
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• 2002

The rate of hydrolysis of insecticide, O,O-diethyl-O-(1-phenyl-3-trifluoromethylpyrazol-5-yl)phosphorothioate (Flupyrazofos) have been investigated in 25% (v/v) aqueous dioxane (${\mu}=0.1M$) at $45^{\circ}C$. The hydrolysis mechanism of flupyrazofos proceeds through the specific acid ($A_{AC}2$) catalysis below pH 4.0, specific base ($B_{AC}2$) catalysis above pH 11.0 and general acid & base ($B_{AC}2$) catalysis between pH 5.0 and pH 10.0 via trigonal-bipyramidal ($d^2sp^3$) intermediate as evidence by solvent effect ($|m|{\ll}|{\ell}|$), rate equation ($kt=ko+k_H+ [H_3O^+]+k_{OH}[OH^-]$) and product analysis. The half-life ($T\frac{1}{2}$) of hydrolytic degradation in neutral media at $45^{\circ}C$ was ca. 3 months.

• Proceedings of the Korean Society of Toxicology Conference
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• 2001.05a
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• pp.122-122
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• 2001

Flupyrazofos is a new type of pyrazole organophosporus insecticide, which has a high activity against the diamond-back moth (Plutella xylostella). The potential of this agent to induce developmental toxicity was investigated in the Sprague-Dawley rat.(omitted)

• Toxicological Research
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• v.14 no.2
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• pp.227-235
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• 1998

KH-502 (Flupyrazofos), a new organophosphorus insecticide synthesized by Korea Re-search Institute of Chemical Technology, was found to be effective against diamond-back moth(Plutella xylostella). This study was carried out to determine the acute toxicity of KH-502 in Sprague-Dawley rats and ICR mice. The test article was orally or dermally administered to the animals. Death, tremors, salivation, lacrimation, abnormal gait and corneal opacity were observed. Decrease in body weight gain was observed in all treatment groups. At necropsy, dark red coloration of lung, enlargement of adrenal glands and atrophy of spleen were observed. The oral $LD_{50}$ value was 372 mg/kg in male rats, 605 mg/kg in female rats, 186 mg/kg in male mice, and 115 mg/kg in female mice. And the dermal $LD_{50}$ was 4086 mg/kg in male and 3881 mg/kg in female rats.

• Applied Biological Chemistry
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• v.40 no.1
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• pp.76-79
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• 1997

Several physicochemical properties such as water solubility, vapor pressure, hydrolysis and octanol/water partition coefficient(Kow) of flupyrazofos, the first organophosphorus insecticide developed in Korea, were measured based on EPA and OECD methods. Water solubility was low showing 0.80 ppm at $25^{\circ}C$ and in hydrolysis study, half-life at $25^{\circ}C$ was 266.5 hr(pH 4.0), 180.0 hr(pH 7.0) and 120.9 hr(pH 9.0) demonstrating instability in alkaline solution. At $40^{\circ}C$ hydrolysis rate was $2{\sim}4$ times higher than that at $25^{\circ}C$. The equation log P=0.673-(1565.4/T) was obtained from vapor pressure experiments at three different temperatures (25, 35, $45^{\circ}C$) and $2.81{\times}10^{-5}$ torr was obtained at $25^{\circ}C$. This value is similar to that of diazinon and 1,000 times lower than that of DDVP suggesting it would not give environmental contamination by volatilization. High log Kow(5.24) was observed and this might result in bioconcentration through food chain. However, its possibility is not likely to be high due to its relatively rapid hydrolysis.