• Food Science and Biotechnology
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• 제17권5호
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• pp.1060-1065
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• 2008

A novel benzoyl glucoside (4) and 13 known phenolic compounds were isolated from the leaves of Camellia japonica by a guided 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay. The structure of 4 was determined to be 4-hydroxy-2-methoxyphenol 1-O-$\beta$-D-(6'-O-p-hydroxylbenzoyl)-glucopyranoside (camelliadiphenoside). The 13 known compounds were identified as (E)-coniferyl alcohol (1), (-)-epicatechin (2), 4-hydroxyphenol 1-O-$\beta$-D-(6-O-p-hydroxybenzoyl) glucopyranoside (3), naringenin 7-O-$\beta$-D-glucopyranoside (5), quercetin 3-O-$\beta$-L-rhamnopyranosyl(1$\rightarrow$6)-$\beta$-D-glucopyranoside (6), kaempferol 3-O-$\beta$-L-rhamnopyranosyl(1$\rightarrow$6)-$\beta$-D-glucopyranoside (7), (+)-catechin (8), 1,6-di-O-p-hydroxybenzoyl-$\beta$-D-glucopyranoside (9), phloretin 2'-O-$\beta$-D-glucopyranoside (10), quercetin 3-O-$\beta$-D-glucopyranoside (11), quercetin 3-O-$\beta$-D-galactopyranoside (12), kaempferol 3-O-$\beta$-D-galactopyranoside (13), and kaempferol 3-O-$\beta$-D-glucopyranoside (14). Their chemical structures were determined by the spectroscopic data of fast atom bondardment mass spectrometry (FABMS) and nuclear magnetic resonance (NMR). Flavonoids having the catechol moiety showed significantly higher DPPH radical scavenging activity than other isolated compounds having monohydroxy phenyl group.

• Bulletin of the Korean Chemical Society
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• 제35권3호
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• pp.839-844
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• 2014

The gas-phase radical-radical reaction $O(^3P)$ + $C_2H_5$ (ethyl) ${\rightarrow}$ $H(^2S)$ + $CH_3CHO$(acetaldehyde) was investigated by applying a combination of vacuum-ultraviolet laser-induced fluorescence spectroscopy in a crossed beam configuration and ab initio calculations. The two radical reactants $O(^3P)$ and $C_2H_5$ were respectively produced by photolysis of $NO_2$ and supersonic flash pyrolysis of the synthesized precursor azoethane. Doppler profile analysis of the nascent H-atom products in the Lyman-${\alpha}$ region revealed that the average translational energy of the products and the average fraction of the total available energy released as translational energy were $5.01{\pm}0.72kcalmol^{-1}$ and 6.1%, respectively. The empirical data combined with CBS-QB3 level ab initio theory and statistical calculations demonstrated that the title exchange reaction is a major channel and proceeds via an addition-elimination mechanism through the formation of a short-lived, dynamical addition complex on the doublet potential energy surface. On the basis of systematic comparison with several exchange reactions of hydrocarbon radicals, the observed small kinetic energy release can be explained in terms of the loose transition state with a product-like geometry and a small reverse activation barrier along the reaction coordinate.

• 대한화학회지
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• 제54권3호
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• pp.275-282
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• 2010

분자 내 수소결합 가능성을 가지고 있는 2-fluorocyclopropanemethanol과 2-chlorocyclopropanemethanol에 대하여 MP2/6-311++G(d,p) 방법과 B3LYP/6-311++G(d,p) 방법으로 최적화 계산을 수행하였다. 두 분자 모두 가장 안정한 conformer에서 O-H의 수소가 F나 Cl을 향하고 있어 수소결합 가능성을 보이기는 하나 $H{\cdots}F$, $H{\cdots}Cl$ 거리가 van der Waals radii보다 커서 강한 수소결합이라 보기 힘들고 두 번째 안정한 conformer의 경우가 가까운 $H{\cdots}F$, $H{\cdots}Cl$ 거리를 보이며 더 강한 수소결합 가능성을 보였다. 그러나 에너지가 5 ~ 7 kJ 더 높게 나타났다. Methanol group과 F나 Cl이 서로 반대 방향을 향할 때 일반적으로 안정하나 앞의 가장 안정한 conformer보다는 에너지가 높다.

• 대한화학회지
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• 제35권6호
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• pp.659-666
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• 1991

질소를 함유한 흥분제와 마약성 진통제 18종류의 약물들을 gas chromatography-nitrogen phosphorus detector(GC-NPD)를 사용하여 human urine으로부터 동시에 신속하게 분석할 수 있는 최적조건을 찾기 위하여 pH 변화와 추출용매 변화에 따른 회수율을 조사하였다. pH 8.5에서 에테르를 추출용매로 사용하였을 때 가장 적은 방해영향과 가장 좋은 회수율을 나타냈다. NPD에 대한 각 약물들의 상대 감응인자를 구하였고, 이 상대감응인자는 약물이 가지고 있는 질소원자의 갯수가 증가할수록 작은 값을 나타냈다. 생체시료 중의 약물들을 신속하게 검정하기 위하여 내부표준물질인 diphenylamine에 대한 relative retention time(RRT)을 작성하였다. 상대머무름 시간은 0.1% 이하의 정밀도를 나타냈다.

• 대한치과기공학회지
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• 제22권1호
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• pp.69-78
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• 2000

The microstructure and corrosion behavior of commercially dental casting gold alloys were investigated to clarify the effect of burn-out temperature and cooling rate. In the case of water quenching after casting, only the αphase, which is typical dendritic microstructure of golda alloy, was detected. However, the precipitates along the grain boundary were detected only at the slow cooling rate and they increased inversely proportional to the burn-out temperature. This might be due to the time difference which solute atom could diffuse. EPMA and SEM results also demonstrated that the precipitate should be lamellar structure consisted of Ag rich phase(${\alpha}_1$) and Cu rich phase (${\alpha}_2$). In terms of corrosion, the galvanic coupling was formed due to the difference of composition between precipitates and matrix at the slow cooling rate. In the case of water quenching, the critical current density($i_p$) which indicate the degree of corrosion was lowest at $650^{\circ}C$ and below the burnout temperature, $i_p$ increased with it because of the effect of grain boundary segregation. But above the temperature, $i_p$ increased with it. This may be due to the strain field effect by residual thermal stress.

• Journal of Ginseng Research
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• 제41권4호
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• pp.602-607
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• 2017

Background: Panax ginseng is a traditional herb used for medicinal purposes in eastern Asia. P. ginseng contains various ginsenosides with pharmacological effects. In this study, floralginsenoside A (FGA), ginsenoside Rd (GRD), and ginsenoside Re (GRE) were purified from P. ginseng berry. Methods: Chemical structures of FGA, GRD, and GRE were determined based on spectroscopic methods, including fast atom bombardment mass spectroscopy, ID-nuclear magnetic resonance, and infrared spectroscopy. Inhibitory activities of these compounds on melanogenesis were studied by measuring the expression of protein and melanin content in the melan-a cell line. This inhibitory activity was confirmed by observing pigmentation and tyrosinase activities of zebrafish. Results: GRD, GRE, and FGA were not cytotoxic at concentrations less than $20{\mu}M$, $80{\mu}M$, and $160{\mu}M$ in melan-a cells, respectively. GRD, GRE, and FGA inhibited melanin biosynthesis in melan-a cells by 15.2%, 22.9%, and 23.9% at $20{\mu}M$, $80{\mu}M$, and $160{\mu}M$, respectively. FGA was observed to display the most potent inhibitory effect. In addition, FGA decreased microphthalmia-associated transcription factor protein expression in a dose-dependent manner. Moreover, FGA induced extracellular signal-regulated kinase phosphorylation level in melan-a cells. In addition, melanin pigment content and tyrosinase activity in zebrafish treated with FGA at $160{\mu}M$ were reduced. Conclusion: FGA showed the most potent inhibition of melanogenesis in both in vitro and in vivo studies. This study suggests that FGA purified from P. ginseng may be an effective melanogenesis inhibitor.

• 대한화학회지
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• 제32권4호
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• pp.297-300
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• 1988

암모늄 파라-메칠벤젠슬폰네이트$(C_7H_11NO_3S)$의 결정 및 분자구조를 실온에서 X-선회절방법으로 결정하였으며 이 화합물의 결정은 사방정계인 $P_{na}2_1$에 속하며 a = 20.406(4), b = 6.271(1), c = 7.067(2)${\AA}$, V = 904.19 ${\AA}^3$, Z = 4, $D_x$ = 1.39, $D_m=1.38g{\cdot}cm^{-3}$, ${\lambda}(M_o K_{\alpha})$ = 0. 71069 ${\AA}$, ${\mu}=3.1 cm^{-1}$, T = 298K, F(000) = 400이다. 구조결정은 직접법을 이용하여 풀어 최소자승법으로 정밀화하였다. 최종 R값은 994개의 I > $16{\sigma}(I)$인 값에 대하여 0.057이다. 메칠벤젠과 황원자는 거의 같은 평면에 있고, $SO_3$와 암모늄이온간에는 3개의 수소결합으로 연결되어 있다. 그 중 둘은 음이온을 c축방향으로, 나머지 하나는 b축 방향으로 연결하여 2차원적인 친수성분자층을 형성하였다. 이들 분자층간에는 메칠벤젠기들이 모여 있어 소수성 분자층을 형성하고 있다.

• Korean Chemical Engineering Research
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• 제43권4호
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• pp.495-502
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• 2005

무전해 도금 용액을 이용하여 구리를 직접 텅스텐(Tungsten, W) 기판 위에 도금하였다. 도금 용액의 농도는 각각 $CuSO_4$ 7.615 g/L, EDTA 10.258 g/L, glyoxylic acid 7 g/L로 하였다. 도금 용액의 pH는 11.0에서 12.8까지 변화시켰으며, 용액의 온도는 $60^{\circ}C$로 유지하였다. 도금된 필름의 특성을 조사하기 위하여 X선 회절분석기, 전계 방출 주사 전자 현미경, 주사형 원자력 현미경, X선 광전자 분석기 및 Rutherford backscattering spectroscope(RBS)를 사용하였다. 구리 도금을 위한 가장 좋은 pH 조건은 11.8이였다. 이 용액에서 10분 동안 도금한 경우 둥근 모양의 구리 입자가 균일하게 도금되었으며, 불순물 peak이 없는 순수 구리 peak이였고, 근평균 제곱 표면 거칠기는 약 11 nm가 되었다. 또한, pH 11.8에서 12분 동안 도금한 필름의 두께는 140 nm이었고 도금속도는 약 12 nm/min였다. 무전해 도금 용액의 pH를 12.8로 증가시키면 도금된 구리 필름은 Cu peak 이외에 불순물 peak인 $Cu_2O$가 나타나고 구리 입자 모양도 기다란 직사각형 모양으로 변하였다. 순수 구리의 도금을 위해서는 도금 용액에서 적당한 pH를 유지하여야 한다. 도금된 구리의 농도는 RBS로 측정한 결과 99 atom％였다. 또한, Cu/W 필름은 전기 도금하는 동안 합금 형태를 이루기 때문에 접착성도 좋았다.

• 한국결정학회지
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• 제16권2호
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• pp.102-106
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• 2005

The crystal structure of the title compound has been analyzed by single crystal X-ray diffraction method. The compound crystallized in the triclinic space group $P\bar{1}$ with a=11.300(6) ${\AA}$, c=18.716(10) ${\AA}$, ${\alpha}=82.833(10)^{\circ}$, ${\beta}=83.042(11)^{\circ}$, ${\gamma}=66.139(10)^{\circ}$, $V=2162(2)\;{\AA}^{3}$, Z=2 and R1=0.661 for 10578 unique reflections. The four $C_{5}Me_{5}$ planar groups from a tetrahedron with a mean dihedral angle $70.92(9)^{\circ}$ among them and the $Ti_{4}O_{6}$ cage sits at the center of the tetrahedron. Each Ti atom in the $Ti_{4}O_{6}$ cage is bonded by three bridging oxygen atoms and coordinated by a $C_{5}Me_{5}$ ligand with a mean distance $2.067{\AA}$ from Ti atoms to the centroids of the four five-membered rings. Two oxygen atoms facing each other in $Ti_{4}O_{6}$ cage are $4.051(3){\AA}$ away in average.

• Bulletin of the Korean Chemical Society
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• 제34권9호
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• pp.2774-2780
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• 2013

Two new isostructural dinuclear complexes, $Ln_2(4-cpa)_6(bpy)_2$ (Ln = Eu (1); Tb (2), 4-cpa = 4-chlorophenylacetate, bpy = 2,2'-bipyridine), have been hydrothermally synthesized and characterized by IR spectroscopy, elemental analysis, thermogravimetric analysis (TGA), powder X-ray diffraction and single-crystal X-ray diffraction. The lanthanide ions are bridged by two bidentate and two terdentate carboxylate groups to give centrosymmetric dimers with $Ln{\cdots}Ln$ separations of 3.967(2) and 3.956(3) ${\AA}$, respectively. Each metal atom is nine-coordinate and exhibits a distorted tricapped trigonal prismatic geometry. Three-dimensional fluorescence spectra show that both 1 and 2 emit bright red and green luminescence at room temperature, with long lifetimes of up to 0.369 ms (at 614 nm) and 0.432 ms (at 543 nm), respectively. Moreover, poor luminescence efficiency has been noted for complex 2. The 4-Hcpa ligand and complexes 1-2 have been screened for their phytogrowth-inhibitory activities against Brassica napus L. and Echinochloa crusgalli L., and the results are compared with the activity of quizalofop-P-ethyl.