• Toxicological Research
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• 제15권1호
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• pp.95-101
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• 1999

Cytochrome P450 (CYP) 3A4 metabolizes aflatoxin B1 (AFB1) to AFB1-exo-8,9-epoxide (8,9-epoxidation) and aflatoxin Q1 (AFQ1; 3$\alpha$-hydroxylation) simultaneously. We investigated whether each metabolite was formed via its own binding site of CAP3A4 active site. Kinetics of the formation of the two metabolites were sigmoidal and consistent with the kinetics of substrate activation. The HIll model predicted that two substrate binding wites are involved in the oxidationof AFB1 by CYP3A4. Dehydronifedipine, a metabolite of nifedipine generated by CYP3A4, inhibited the formation of AFQ1 without any inhibition in the formation of AFB1-exo-8,9-epoxidation. Dehydronifedipine was found to act as a reversible competitive inhibitor against 3$\alpha$-hydroxylation of AFB1. Vmax and S0.5 of the 8,9-epoxidation were not changed in the presence of 0, 50, or 100 $\mu\textrm{M}$ dehydronifedipine. S0.5 of 3$\alpha$-hydroxylation was increased from 58$\pm$4 $\mu\textrm{M}$ to 111$\pm$8 $\mu\textrm{M}$ in the presence of 100 $\mu\textrm{M}$ nifedipine whereas Vmax was not changed. These results suggest that there exist two independent binding sites in the active site of CAP3A4 . One binding site is responsible for AFB1-exo-8,9-epoxidation and the other is involved in 3$\alpha$-hydroxylation of AFB1. Dehydronifedipine might selectively bind to the site which is responsible for the formation of AFQ1 in the active site of CYP3A4.

• Bulletin of the Korean Chemical Society
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• 제26권3호
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• pp.433-439
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• 2005

To gain further insight on the relationship between structure and functions of glutathione S-transferase (GST), the three tyrosine 108 mutants, Y108A, Y108F, and Y108W, of human GST P1-1 were expressed in Escherichia coli and purified to electrophoretic homogeneity by affinity chromatography on immobilized GSH. The substitution of Tyr 108 with alanine resulted in significant decrease of the GSH-conjugation activity and the GSH peroxidase activity, but approximately 63% increase of steroid isomerase activity toward ${\Delta}^5$–[androstene 3,17-dione. On the other hand, the substitution of Tyr 108 with phenylalanine resulted in decreases of $k_{cat}\;and\;k_{cat}/K_m{^{EPNP}}$ by 2 orders of magnitude, suggesting that Tyr 108 residue of hGSTP1-1 are considered to be important for the catalysis and the binding of the epoxide substrates. The substitution of Tyr 108 with tryptophan resulted in significant decreases of the specific activities toward EPNP, cumene hydroperoxide and ${\Delta}^5$–ndrostene 3,17-dione, but approximately 2-fold increase on the enzyme-catalyzed addition of GSH to DCNB. We conclude from these results that Tyr 108 in hGST P1-1 plays very different roles depending upon the nature of the electrophilic substrates.

• 한국환경농학회지
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• 제31권3호
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• pp.255-263
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• 2012

BACKGROUND: The analysis for the concentration and enantiomeric ratio of OCPs have been performed to confirm the distribution and to emonstrate the pollution characteristics of chiral OCPs in ambient air. METHODS AND RESULTS: In ambient air at coastal and inland sites, concentrations and enantiomer fractions (EFs) of heptachlor (HEPT), eptachlor epoxide (HEPX), trans-chlordane (TC), cis-chlordane (CC), xychlordane (OXY), 2,4'-DDT, 2,4'-DDD with HRGC/HRMS were investigated to understand source and distribution of chiral organochlorine pesticides (OCPs) in ambient air. The mean concentrations of OCPs in ambient air were at the range of 0.027(heptachlor)~1.279 (4,4'-DDT) pg/m3 and 0.0005 (heptachlor)~0.1043 ng/g d.w. (TC), respectively. The mean EFs of OCPs in ambient air were at the range of 0.73 (HEPX)~0.45 (CC). Both preferential depletions of (+) and (-) enantiomer were observed for CC, indicated by EFs either <0.5 or >0.5, while preferential depletions of (-) enantiomer which mean EFs <0.5 were observed for chiral OCPs except TC and MC-5. CONCLUSION: OCPs in ambient air have been distributed from soil, but some of them such as chlordane, DDT etc. might have been introduced by long-range atmospheric transport, considering EFs by chiral analysis and trajectory analysis.

• 한국식품영양학회지
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• 제27권2호
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• pp.194-202
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• 2014

This study investigates the chemical compositions of Aster koraiensis Nakai essential oils and the quantitative changes of major terpene compounds according to various harvesting times. The essential oils obtained by hydrodistillation from the aerial parts of Aster koraiensis Nakai are being analyzed by GC and GC-MS. The essential oil compositions of Aster koraiensis Nakai are characterized byhigher contents of sesquiterpene compounds. Ninety-seven volatile flavor compounds are being identified in the essential oils from Aster koraiensis Nakai harvested in 2010, and caryophyllene oxide (8.38%), aristolene (7.08%), epiglobulol (5.57%), and ethyl furanone (4.73%) are the most abundant compounds. Ninety-five compounds are identified in the essential oils from the plants harvested in 2011, and aristolene (11.56%), calarene (9.33%), phytol (8.28%), ethyl furanone (7.63%), and epiglobulol (7.18%) are the most abundant compounds. Ninety-five compounds are being identified in the essential oils from the plants harvested in 2012, and calarene (15.3%), aristolene (14.24%), ethyl furanone (7.21%), phytol (6.98%) are the major compounds. The contents of aristolene, ${\alpha}$-caryophyllene, ${\alpha}$-muurolene, ${\alpha}$-calacorene, aromadendrene oxide, and calarene increase significantly from 2010 to 2012. The contents of ${\alpha}$-cubebene, isocaryophyllene, and diepi-${\alpha}$-cedrene epoxide decrease significantly from 2010 to 2012. The quantitative changes of aristolene and calarene according to harvesting time can be served as a quality index of the Aster koraiensis Nakai essential oils.

• 한국환경보건학회지
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• 제40권6호
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• pp.442-453
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• 2014

Objectives: Persistent organic pollutants (POPs) are known to be the detrimental chemicals in the body, even at low levels, and are stored in adipose tissue. Recently, POPs have been reported to be associated with chronic diseases, including cancer and cardiovascular disease, and aging and obesity are reported as common factors in chronic disease. However, there have been only a few studies on the associations of POPs with age and body mass index (BMI) in Korea. Therefore, we analyzed the associations of serum POPs levels with age and BMI in Korea. Methods: This cross-sectional study includes 444 subjects (253 men and 191 women) from the Korean Cancer Prevention Study-II (2004-2011). Serum levels of 33 polychlorinated biphenyls (PCBs) and 19 organochlorine pesticides (OCPs) were measured by a gas chromatographer (Agilent 6890) coupled to high resolution mass spectrometer (JEOL JMS-800D). Results: Concentrations of PCB 153 (men: 12.26 ng/g lipid, women: 10.50 ng/g lipid) and p,p'-DDE (men: 94.66 ng/g lipid, women: 96.66 ng/g lipid) were the highest among serum PCBs and OCPs, respectively. PCBs and OCPs were significantly positively correlated with age in both sexes. After adjustment for age, non-dioxin like PCBs were significantly negatively correlated with body mass in women. However, cis-heptachlor epoxide was significantly positively correlated with body mass index in both sexes. When analyzed by sex, stronger associations were shown between POPs and age in men and POPs and BMI in women. Conclusion: These results may provide baseline data for the study of POPs and for the health management field in Korea.

• 보존과학회지
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• 제28권2호
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• pp.131-139
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• 2012

석조문화재의 보존 복원 과정에 적용되는 에폭시 수지에 경화제의 혼합을 통하여 경화 시 발열 반응을 제어할 수 있는 접착 시스템을 연구하였다. 사용된 에폭시 주제는 hydrogenated bisphenol A (HBA), 경화제로는 속경화형 경화제 FH와 poly(propyleneglycol)bis(2-aminopropylether) (SH)를 사용하였으며, 무기 첨가물은 탈크를 사용하였다. 에폭시 수지와 경화제의 혼합비에 따라 경화 시 온도를 측정하고, differental scanning calorimeter (DSC)를 이용하여 경화동력학을 확인하였으며, 기계적 특성을 파악하기 위해 무기 첨가물의 함량에 따른 인장강도, 전단강도를 측정하였다. 연구 결과, 에폭시 수지의 경화제 혼합을 통하여 경화 시 반응열 상승폭 제어 및 경화 거동 제어의 가능성을 확인하였으며, 무기 첨가물 첨가를 통해 적절한 강도 조절이 가능하여 석조문화재에 적용 가능한 새로운 접착 시스템을 개발하였다.

• 공업화학
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• 제18권4호
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• pp.330-336
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• 2007

본 연구에서는 $BF_3$를 함유한 키랄성 코발트 살렌 촉매를 합성하고 비대칭촉매특성을 평가하였다. 촉매의 구조를 결정하기 위하여 NMR, UV 및 ESCA분석을 수행하였다. 합성한 촉매는 여러 종류의 에폭사이드 유도체의 가수분해 속도차에 의한 비대칭 고리열림반응에 적용하여 그 활성과 선택성을 조사하였다. 살렌과 $BF_3$의 비를 다르게 하여 합성한 촉매는 전혀 다른 촉매 활성을 나타내었으며, 그 비를 2 : 1로 하여 합성한 2분자구조의 살렌착체 촉매는 물을 친핵체로 하는 라세믹 에폭사이드의 고리 열림을 통하여 99 %ee 이상의 매우 높은 광학선택성을 보였다. 특히 2분자형의 살렌 촉매는 단분자형의 촉매에 비하여 촉매량을 적게 첨가하여도 현저히 향상된 촉매활성을 나타내었고 얻어진 생성물의 분리과정에서 라세믹화를 유발시키지 않았다. 본 연구에서 적용한 촉매시스템은 키랄 에폭사이드 및 1,2-디올 중간체의 제조에 매우 효과적이었다.

• 한국축산식품학회지
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• 제38권3호
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• pp.433-441
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• 2018

The objective of present study was to investigate the effect of cooking and their combinations with re-heating methods on the formation of cholesterol oxidation products (COPs) in stored chicken thigh meat. Pan roasting, steaming, oven grilling, charcoal grilling, and microwaving were used for cooking. Re-heating of samples was done using the same cooking methods or microwaving after 3 and 6 d of refrigerated storage. Cooking and re-heating resulted in reduction of crude fat and cholesterol contents of chicken thigh meat depending on storage period before re-heating. Cooking and storage period had no influence on the total amount of COPs. The highest total amount of COPs was observed in meat samples cooked by steaming and reheated by microwaving after 6 d of storage, which showed similar value to raw chicken meat stored for 6 days. However, different re-heating methods formed different types of COPs depending on storage period before re-heating. The high amount (p<0.05) of 25-hydroxycholesterol or ${\alpha}-epoxide$ was detected in meat samples reheated by steaming or microwaving at 3 or 6 d of storage after steamed cooking, respectively. As a result, the combination of steaming and re-heating with microwaving could increase the total amount of COPs in chicken thigh meat and different cooking/re-heating methods could form different types of COPs, even though no significant difference in the total amount of COPs depending on storage period.

• Journal of Preventive Medicine and Public Health
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• 제28권1호
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• pp.141-152
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• 1995

This study was performed to find out the influences of ethanol on the metabolism of trichloroethylene(TRI) in rats. TRI in corn oil at the dosage of 150, 300, 600 mg/kg was injected peritoneally once a day for two days to two groups. In one group ethanol(4 g/kg) was taken orally 30 minutes before TRI injection, and the other group ethanol was not. The results of experiments are as follows: 1. The contents of cytochrome P-450 and $b_5$ had inverse relationship with in-jected TRI amounts in both groups. 2. The activity of NADPH P-450 reductase was decreased slowly in TRI injected group related with TRI amount, but decreased drastically in the group pretreated with ethanol. 3. The activity of NADH $b_5$ reductase had relationship with injected nt amount , but the statistical significance was found only in the groups of 300 and 600 mg/kg of TRI injected without relevance to ethanol when compared with the group that was not injected. 4. The activity of ADH was more decreased and ALDH activity was more increased in groups that TRI injected and ethanol was pretreated with ethanol groups than in group without any treatment. These results suggest that ethanol may inhibit epoxide formulation, the first step of TRI metabolism, and change from TCE-OH to TCA also.

• Toxicological Research
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• 제6권2호
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• pp.167-182
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• 1990

Dietary restriction (caloric restriction) is the only intervention which has been reliably shown to extend the maximum life span of warm-blooded animals and delay the many phenomena associated with aging. It is also one of the most effective modulators of toxicity, especially cancer endpoints. In spite of the known modulator effects of caloric restriction, the biological mechanisms responsible for these effects had not been in vestigated until recently. The National Center for Toxicological Research (NCTR), in a collaborative effort with the National Institute of Aging (NIA), initiated a project whereby nine (9) combinations of rodent species/strains and diets were fed both restricted and ad libitum. The NIA's initiative was to identify biomarkers of aging whereas NCTR's initiative was to identify the biological effects associated with the profound effects caloric restriction has in protecting against both spontaneous (age-related) and chemically-induced toxic endpoints. Independent of sex or species, caloric restriction has similar effects on body temperature, oxygen consumption and $CO_2$production. Caloric restriction also decreased lipid glycolysis and metabolism in rats and mice, which suggest decreased production of metabolites which could lead to fatty acid epoxide formation. The age-associated loss of ciradian regulation of intermediate enzymes is also significantly reduced. Moreover, caloric restriction reduced the age-associated feminization of sexually dimorphic liver isozymes, increased several glucocorticoid responsive isozymes, elevated glucagon/insulin ratios, produced less microsomal superoxide and enhanced the capacity for utilzing detoxicating metabolic pathways. Calorically restricted rats have less than half the number of aflatoxin ($AFB_1$)-DNA adducts than ad libitum animals and urinary excretion of $AFB_1$ was increased significantly. Finally, DNA repair mechanisms are enhanced and oncogene expression is decreased in calorically restricted animals.