• Natural Product Sciences
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• v.19 no.3
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• pp.206-214
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• 2013

The crocetin derivatives, crocin (1), gentiobiosyl glucosyl crocetin (3), and mono-gentiobiosyl crocetin (4) were isolated from the fruit of Gardenia jasminoides (Gj) and crocetin (2) from the processed fruit of Gj (PGj) by column chromatography. Their structures were determined on the basis of spectroscopic methods including IR, MS, and NMR (1D and 2D). These compounds were evaluated for their inhibition activity on melanin production in ${\alpha}$-MSH (melanocyte stimulating hormone) activated B16F10 cells. Compounds 1 - 4 reduced melanin content in a dose-dependent manner at concentrations of 20 - 60 uM. They also suppressed tyrosinase protein and m-RNA expressions dose dependently, assayed by western blot analysis, and RT-PCR experiment in B16F10 murine melanoma cells.

• Natural Product Sciences
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• v.19 no.3
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• pp.258-262
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• 2013

Three ergosterol derivatives, ergosta-4,6,8(14),22-tetraen-3-one (1), ergosta-7,24(28)-dien-3-ol (2), and 5,8-epidioxyergosta-6,22-dien-3-ol(3) were isolated from the fruit body of Phellinus pini. Their structures were based on spectroscopic methods including IR, MS, and NMR (1D and 2D). These compounds were evaluated for their activity to decrease melanin production in ${\alpha}$-MSH (melanocyte stimulating hormone) activated B16F10 cells. Compound 1, 2, and 3 reduced melanin content in a dose-dependent manner at concentrations of 5~15 uM. They also suppressed the tyrosinase expression of protein and m-RNA level dose dependently by western blot analysis and RT-PCR experiment in B16F10 murine melanoma cells.

• Journal of the Korean Wood Science and Technology
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• v.19 no.4
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• pp.73-79
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• 1991

The flavonoids from plants is very widly used as natural dye for food and medicine etc. In this study, red pine which is widespread in Korea was studied to find new chemicals which may use as raw material for the special purpose. The fIavonoids of red pine bark were separated with Sephadex LH-20 and Toyo pearl HW-40F as packed materials and the structure of separated f1avonoids was determined by $^1H$-and $^{13}C$-NMR spectroscopy. The (+) catechin which is widespread in nature and dihydroquercetin-3'-0-${\beta}$-galactoside were found in red pine bark. The dihydroquercetin-3'-0-${\beta}$-galactoside is newly found in this species.

• Journal of Magnetics
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• v.1 no.2
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• pp.57-59
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• 1996

The YBa$_2$Cu$_3$O6+xstructures have been fluorinated by a gas phase exchange technique, and 19F NMR was used to identify the structural fluorine. Magnetic susceptibility measurements showed that the fluorination turned a marginally nonsuperconducting sample into a 40 K superconductor, as well as that it raised the onset of the superconducting transition of the 60 K superconductor YBa$_2$Cu$_3$O6.7 to about 100 K.

• Journal of Magnetics
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• v.1 no.1
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• pp.1-3
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• 1996

The $YBa_2Cu_3O_{7-x}$ structure has been fluorinated by a gas phase exchange technique. The ${^19}F$NMR (nuclear magnetic resonance) spin-lattice relaxation rate (1/T1) measurements on a fluorinated sample gave superconducting energy gap of $2\Delta=4.6kT_c$.

• Bulletin of the Korean Chemical Society
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• v.29 no.12
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• pp.2355-2360
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• 2008

• Bulletin of the Korean Chemical Society
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• v.3 no.2
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• pp.66-70
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• 1982

The question of the bicyclohomoaromatic stabilization and destabilization is examined. The chemistry of bicyclo(3.2.1)octa-3,6-dienide anion has been studied on order to test these concepts. The bicyclooctadienide anion is shown to be stable delocalized ion which undergoes a facile proton-deuterium exchange reaction. The solvolysis of bicyclo(3.2.1)octa-3,6-dienyl p-nitrobenzoate is much slower than the monoene analog. We have made direct observation of the bicyclooctadienyl and octenyl cations by $^{19}F$-nmr spectroscopy, and were able to demonstrate that the bicyclooctadienyl cation was bishomoantiaromatic.

• Macromolecular Research
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• v.17 no.11
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• pp.870-873
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• 2009

In this study, 2-diglycidylether of benzotrifluoride (2-DGEBTF) and 4-diglycidylether of benzotrifluoride (4-DGEBTF) epoxy resins, which contained fluorine groups in the main chain, were synthesized. The resins were characterized by FTIR, $^1H$ NMR, $^{13}C$ NMR and $^{19}F$ NMR spectroscopy. The 2-DGEBTF and 4-DGEBTF epoxy resins were cured with triethylene tetramine (TETA), and the effect of the fluorine group on the synthesized epoxy resin on the cure behavior, thermal, and mechanical properties was investigated. The 2-DGEBTF/TETA system was more reactive than the 4-DGEBTF/TETA system, whereas the thermal stability factor i.e., the decomposition activation energy ($E_d$), of 4-DGEBTF/TETA was higher than that of 2-DGEBTF/TETA. These results can be explained by the decrease in cross-linking density and decomposition of the short side chains, resulting in the $CF_3$ group at the para position. However, the $K_{IC}$ value of 4-DGEBTF/TETA was higher than that of 2-DGEBTF/TETA. This was attributed to the increase in flexibility in the epoxy backbone, resulting in a difference in steric hindrance and polarlizability.

• Bulletin of the Korean Chemical Society
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• v.19 no.8
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• pp.847-851
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• 1998

13C, 15N, and 29Si NMR chemical shifts have been computed for selected X-substituted silatranes (X=Cl, F, H, CH3) using Gauge-Including Atomic Orbitals (GIAO) and Continuous Set of Gauge Transformations (CSGT) at the Hartree-Fock level of theory. The isotropic 13C chemical shifts are largely insensitive to substituent-induced structural changes. In this study, the isotropic 13C chemical shifts GIAO and CSGT calculations at the HF/6-31G and HF/6-31G* levels are sufficiently accurate to aid in experimental peak assignments. The isotropic 13C chemical shifts X-substituted silatranes at HF/6-31G* level are approximately 4 ppm different from the experimental values. In contrast, the isotropic 15N and 29Si chemical shifts and the chemical shielding tensors are quite sensitive to substituent-induced structural changes. These trends are consistent with those of the experiment. The 15N chemical shift parameters demonstrate a very clear correlation with Si-N distance, especially when we use the polarization function. Changes in anisotropy, 3a as well as in the 15N isotropic chemical shifts are due primarily to changes in the value of a.. But in case of "Si the correlations are not as clean as for the 15N chemical shift.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.3
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• pp.96-102
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• 2015

Traditional propellants emit toxic gases such as carbon dioxide and hydrogen chloride during combustion which are harmful to the environment. This study established a synthetic process of a high nitrogen containing derivative of tetrazine, 3,3-Azobis(6-Amino-1,2,4,5-Tetrazine) (DAAT), which can be applied as solid fuels for a solution to environmental concerns. Also, this paper described the detailed process and the analytic results of properties, which were not mentioned in previous reports. The compound was characterized by NMR, IR spectroscopy, and thermal, impact, and friction stability were measured. In addition, the heats of formation (${\Delta}H_f$) and detonation properties (pressure and velocity) of DAAT were calculated using Gaussian 09 and EXPLO5 programs.