• Korean Journal of Food Science and Technology
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• v.45 no.3
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• pp.285-292
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• 2013

This study was carried out to validate the safety of ametoctradin residues in agricultural commodities by developing an official analysis method. An analytical method was developed and validated using HPLC-PDA detectors. The samples were extracted with methanol, subsequently partitioned with dichloromethane and purified with florisil column chromatograph using acetone/hexane (30/70, v/v) as solvent. The method was validated by using grape, hulled rice, mandarin, and potato spiked with ametoctradin at 0.05 and 5.0 mg/kg, and pepper at 0.05 and 2.0 mg/kg. Average recoveries were 76-114.8% with relative standard deviation less than 10%, and the limit of detection and limit of quantification were 0.0125 and 0.05 mg/kg, respectively. The result of recoveries and overall coefficient of variation of the laboratory results from Gwangju regional Food and Drug Administration (FDA) and Daejeon regional FDA was accorded with Codex Alimentarius Commission Guideline (CAC/GL 40). Based on these results, this method was found to be appropriate for ametoctradin residue determination and can be used as the official method of analysis.

• Analytical Science and Technology
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• v.26 no.3
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• pp.174-181
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• 2013

Pyrifluquinazon is classified with a quinazoline insecticide that regulates food intake by controling the feeding behavior acting on the endocrine or nervous system of pests such as aphids and white fly. To keep safety on pyrifluquinazon residues in agricultural commodities a simple, accurate and rapid analytical method was developed and validated using high performance liquid chromatograph (HPLC-UVD). The pyrifluquinazon residues acidified with 1% formic acid in samples were extracted with acetonitrile and partitioned with hexane subsequently to dichloromethane then purified with silica solid phase extraction (SPE) cartridge. The purified samples were detected using HPLC-UVD. The method was validated using apple and pear spiked with pyrifluquinazon at 0.02, 0.05 and 0.1 mg/kg and hulled rice, pepper, soybean at 0.05 and 0.1 mg/kg. Average recoveries were 70.5~107.9% with relative standard deviation less than 10%. The result of recoveries and overall coefficient of variation of a laboratory results in Gwangju regional FDA and Daejeon regional FDA was followed with Codex guideline (CODEX CAC/GL 40). This method is appropriated at pyrifluquinazon residues determination and will be used as official method of analysis.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1998.11a
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• pp.136-136
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• 1998

L-asparaginyl and L- aspartyl residues in proteins are subject to spontaneous degradation reactions generating isomerized and racemized aspartyl derivatives. Proteins containing L-isoaspartyl and D-aspartyl residues usually have altered structures and diminished biological activities. These residues can be recognized and be repaired to normal L-aspartyl residues by protein L-isoaspartyl methyltransferase(PIMT), which is present at high levels in testis. Although testicular PIMT have been shown to be involved in either sperm motility or sperm maturation, it may play an important role in the repair of damaged sperm proteins during the prolonged period of epididymal transport and storage. In the present study, as a initial step toward elucidating the function of protein carboxylmethylation in testis, we purified PIMT from porcine testicular cytosol as a momeric 27,000 Da species by ammonium sulfate precipitation, DEAE-sephacel chromatography, SAH-liganded affinity chromatography, and gel filtration chromatography. The optimum pH for the reaction was 6.0. $K_{m}$ values of the enzyme for the S-adenosyl-L-methionine (SAM), synthetic oligopeptide(VYP-L-isoD-HA) and histone type II-As were 1.0 ${\mu}$M, 33.2 ${\mu}$M and 276 ${\mu}$M respectively. Consequently, properties of the porcine testicular PIMT is similar to that of other mammalian PIMTs.

• Journal of Food Hygiene and Safety
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• v.33 no.3
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• pp.176-184
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• 2018

The aim of the present work was to develop simultaneous methods of quantification of carazolol, azaperone, and azaperol residues in livestock and fishery products using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Samples were extracted from beef, pork, chicken, egg, milk and shrimp using acetonitrile (ACN); while flat fish and eel were extracted using 80% ACN. For purification, ACN saturated n-hexane was used to remove fat composition. The standard calibration curves showed good linearity as correlation coefficients; $r^2$ was > 0.99. Average recoveries expressed were within the range of 67.9-105% for samples fortified at three different levels ($0.5{\times}MRL$, $1{\times}MRL$ and $2{\times}MRL$). The correlation coefficient expressed as precision was within the range of 0.55-7.93%. The limit of quantification (LOQ) was 0.0002-0.002 mg/kg. The proposed analytical method showed high accuracy and acceptable sensitivity based on Codex guideline requirements (CAC/GL71-2009). This method can be used to analyze the residue of carazolol, azaperone, and azaperol in livestock and fishery products.

• Korean Journal of Veterinary Research
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• v.38 no.3
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• pp.544-552
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• 1998

A random study of 574 dairy farms in Gyeongnam area was designed to determine 1) management factors that may be associated with the occurrence of drug residues; 2) the dairy farmer's attitudes and knowledge about residues; 3) how these variables influence the occurrence of residues in dairy cattle. Management factors perceived as having the greatest influence on drug residues in milk were insufficient knowledge about withdrawal periods, errors due to hired help, insufficient identification and record of animals treated for mastitis, dry cow treatment for mastitis, and metritis treatment. Seventy-one percent of farms with residues problem used mixed own feeds compared with twenty-nine percent of farms with premedicated feeds. Factors significantly associated with the occurrence of residues were herd size, increased number of hired persons, increased frequency of use of mixed-own feeds, category of medicated feed, and producer's attitude toward the public health significance of residues. Our findings suggest that residue occurrence was mainly associated with errors due to hired help, insufficient knowledge about withdrawal periods, poor animal identification and records of treatment animals and use of medicated feeds. Any residue avodiance educational program needs to stress how to deal with these factors. This educational program should be directed to dairy farmers and employees, especially temporary employees. In addition, Dairy farmer's attitudes and knowledge about drug residues need to be improved. More evidence on the public healths significance of residues should be available to them. Because belife in importance of public healths concerns was related to successful residue avidance and because 81.3% of the dairy farmers with residue problem thought public healths concerns were less important than economic ones, it would be helpful to provide educational programs specifically directed to this issue. it may be useful to provide programs not only for the dairy farmers but also change of their concerns about on the public healths.

• Journal of Food Hygiene and Safety
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• v.32 no.4
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• pp.298-305
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• 2017

Benzovindiflupyr is a new pyrazole carboxamide fungicide that inhibits succinate dehydrogenase of mitochondrial respiratory chain. This study was carried out to develop an analytical method for the determination of benzovindiflupyr residues in agricultural commodities using LC-MS/MS. The benzovindiflupyr residues in samples were extracted by using acetonitrile, partitioned with dichloromethane, and then purified with silica solid phase extraction (SPE) cartridge. Correlation coefficient ($r^2$) of benzovindiflupyr standard solution was 0.99 over the calibration ranges ($0.001{\sim}0.5{\mu}g/mL$). Recovery tests were conducted on 5 representative agricultural commodities (mandarin, green pepper, potato, soybean, and hulled rice) to validate the analytical method. The recoveries ranged from 79.3% to 110.0% and then relative standard deviation (RSD) was less than 9.1%. Also the limit of detection (LOD) and limit of quantification (LOQ) were 0.0005 and 0.005 mg/kg, respectively. The recoveries of interlaboratory validation ranged from 83.4% to 117.3% and the coefficient of variation (CV) was 9.0%. All results were followed with Codex guideline (CAC/GL 40) and Ministry of Food and Safety guideline (MFDS, 2016). The proposed new analytical method proved to be accurate, effective, and sensitive for benzovindiflupyr determination and would be used as an official analytical method.

• Analytical Science and Technology
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• v.21 no.6
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• pp.535-542
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• 2008

A liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI/MS/MS) method was developed for the determination and confirmation of clenbuterol in bovine muscle and milk. Clenbuterol and clenbuterol-D9 using as an internal standard in samples were extracted with ethyl acetate after hydrolysis and evaporated to dryness. The extracts were dissolved in 20% methanol and cleaned using HLB solid-phase extraction cartridge. The analytes were detected by LC-ESI/MS/MS on a $C_{18}$ column. Mass spectral acquisition was done in selected reaction monitoring (SRM) in positive ion mode to provide a high degree of sensitivity. Using MS/MS with SRM mode, the transitions (precursor to product) monitored were m/z 277${\rightarrow}$203 for clenbuterol, and m/z 286${\rightarrow}$204 for internal standard. The limits of quantitation (LOQ) and mean recoveries of clenbuterol in bovine muscle were $0.2{\mu}g/kg$ and 84.3~91.1%, respectively. The LOQ and mean recoveries in milk were $0.05{\mu}g/kg$ and 87.7~98.3%, respectively.

• Journal of Food Hygiene and Safety
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• v.27 no.4
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• pp.332-338
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• 2012

A simple and sensitive analytical method was developed using gas chromatography with electron capture detector (GC-ECD) and gas chromatography-mass spectrometry (GC-MS) for determination of Picoxystrobin in agricultural products (apple, hulled rice, mushroom, pepper, soybean, and mandarin). Picoxystrobin residues were extracted with acetonitrile, partitioned with saline water, and then they were cleaned up on a florisil solid-phase extraction (SPE) cartridge to obtain an extract suitable for analysis by GC-ECD and GC-MS. The method was validated using 6 agricultural product samples spiked with Picoxystrobin at different concentration levels (0.02, 0.05 and 0.5 mg/L). Average recoveries of Picoxystrobin (using each concentration three replicates) ranged 64.0~98.3% with relative standard deviations less than 10%, calibration solutions concentration in the range 0.1~5 mg/L, and limit of detection (LOD) and limit of quantification (LOQ) were 0.005 and 0.02 mg/L, respectively. The result showed that the developed analytical method is suitable for Picoxystrobin determination in agricultural products.

• Bulletin of the Korean Chemical Society
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• v.35 no.8
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• pp.2317-2325
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• 2014

P-glycoprotein (P-gp) is a member of the ATP-Binding Cassette transporter superfamily and mediates transmembrane efflux of many drugs. Since it is involved in multi-drug resistance activity in various cancer cells, the development of P-gp inhibitor is one of the major concerns in anticancer therapy. Human P-gp protein has at least two "functional" drug binding sites that are called "H" site and "R" site, hence it has multi-binding-specificities. Though the amino acid residues that constitute in drug binding pockets have been proposed by previous experimental evidences, the shapes and the binding poses are not revealed clearly yet. In this study, human P-gp structure was built by homology modeling with available crystal structure of mouse P-gp as a template and docking simulations were performed with inhibitors such as verapamil, hoechst33342, and rhodamine123 to construct the interaction between human P-gp and its inhibitors. The docking simulations were performed 500 times for each inhibitor, and then the interaction frequency of the amino acids at the binding poses was analyzed. With the analysis results, we proposed highly contributing residues that constitute binding pockets of the human P-gp for the inhibitors. Using the highly contributing residues, we proposed the locations and the shapes of verapamil binding site and "R" site, and suggested the possible position of "H" site.

• 한국환경농학회:학술대회논문집
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• 2011.07a
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• pp.469-470
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• 2011