• Title/Summary/Keyword: dimers

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Inhibition of Tyrosinase and Lipoxygenase Activities by Resveratrol and Its Derivatives from Seeds of Paeonia lactiflora

  • Kim, Hyo-Jin;Ha, Sang-Chul;Park, Sang-Won
    • Preventive Nutrition and Food Science
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    • v.7 no.4
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    • pp.447-450
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    • 2002
  • Previously, a methanol extract from seeds of Paeonia lactiflora was shown to have a potent inhibitory activities against tyrosinase and soybean lipoxygenase (SLO). Seven stilbenes, trans-resveratrol-4-Ο-$\beta$-D-glucoside, trans resveratrol, trans-$\varepsilon$-viniferin, cis-$\varepsilon$-viniferin, gnetin H, suffruticosol A and B were isolated from the seeds as active principles for inhibition of the enzymatic activity. Among them, the resveratrol trimer, gnetin H exhibited the most potent inhibitory activities against tyrosinase and SLO, respectively. Additionally, the resveratrol dimers, trans-$\varepsilon$-viniferin and cis-$\varepsilon$-viniferin exhibited significant inhibitory activity against the two oxidative enzymes. Meanwhile, three other stilbene derivatives, such as trans-resveratrol, suffruticosol A and suffruticosol B had also weak inhibition activity. The least inhibitory activity was observed in transresveratrol-4-Ο-$\beta$-D-glucoside. These results suggest that resveratrol dimers and trimer in the seeds of Paeonia lactiflora are potentially useful therapeutic agents against pathological disorders such as hyperpigmentation and inflammation.

The Infrared Absorption Spectra of Molecular Clusters of Acetonitrile and DMF Diluted by Matrices at 80K (매트릭스에 의해 희석된 ACETONITRILE과 DMF 분자클라스터의 80K에서 적외선 흡수 스펙트럼의 분석)

  • Kim, Wan Hee;Jeong, Jong Hak;Jeong, Gi Ho
    • Analytical Science and Technology
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    • v.5 no.3
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    • pp.285-294
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    • 1992
  • Structures of dimers of the acetonitrile and DMF diluted by carbon-tetrachloride and xenon matrices at 80K were studied with infrared absorption spectroscopy. Sample and matrix materials were codeposited onto a KBr cold trapping window. Infrared absorption spectra of pure samples and diluted samples were compared to explain the structures of dimers. The acetonitrile dimer showed the antiparallel shape and the DMF dimer showed the linear shape. After annealing, the infrared spectrum of the diluted sample showed the same shape with that of the pure sample.

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The Action Mode of $\beta$-glucosidase Purified from Trichoderma koningii (Trichoderma koningii에서 분리한 $\beta$-glucosidase의 작용양상)

  • 정춘수;최지영;이헌주;맹필재;한인섭;강사욱;하영칠
    • Korean Journal of Microbiology
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    • v.36 no.1
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    • pp.8-13
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    • 2000
  • We have examined the mode of transglycosylation, catalyzed by an extracellular $\beta$-glucosidase purified from Trichoderma koningii ATCC 26113, using cellobiose, sophorose, laminaribiose and gentiobiose as substrates. The dimers separated from the reaction mixture by HPLC were analyzed by $^(1)H$-NMR spectroscopy. When cellobiose was subjected to the action of the $\beta$-glucosidase, the products included laminaribiose, sophorose and gentiobiose. When laminaribiose, sophorose or gentiobiose was used as a substrate, the $\beta$-glucosidase accumulated transglycosylation products possessing different types of $\beta$-glycosidic linkages from the original one. The amount of dimers accumulated as reaction proceeded seemed to be dependent on the velocity of hydrolysis but not on that of formation.

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Structural Study of Antisense Dimers, Modified Adenosine-Thymidine Phosphorothioate

  • Jung, Kyeong-Eun;Yang, Mi-Rim;Lee, Kwang-Jun;Lim, Hong;Jung, Ji-Hyun;Lim, Yoon-Gho;Cho, Youl-Hee;Shin, Dong-Hoon;Lee, Chul-Hoon
    • Journal of Microbiology and Biotechnology
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    • v.10 no.6
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    • pp.889-892
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    • 2000
  • Antisense molecules are structurally simple linear oligomers of nucleotides. They can recognize a complementary sequence by base pairing, therefore, antisense drugs composed of 15-16 bases are potentially useful, unlike drugs such as protein agonists, antagonists, and inhibitors. Since antisense oligomers are classified as nucleotides, they are subject to attack by nucleases. In order to be antisense drugs resistant to degradation by nucleases, the structural modifications in the linkages, bases, and sugars to satisfy this requirement are considerable. We attempted in this study, to synthesize 16-mer antisenses with a modified linkage and adenosine. When studying on the three-dimensional structure of the oligomer, however, the existence of isomers may complicate the interpretation of the NMR data. Therefore, an attempt was made to eliminate the above problem, thus, two dimers were synthesized and their structural studies were carried out.

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Relative Reactivity of Various Al-substituted-dialkylalans in Reduction of Carbonyl Compounds: A Theoretical Study on Substituent Effect

  • Nahm, Keepyung;Cha, Jin Soon
    • Bulletin of the Korean Chemical Society
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    • v.34 no.8
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    • pp.2335-2339
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    • 2013
  • Relative reactivity of various Al-substituted dialkylalans ($AlR_2(X)$) in reduction of acetone has been studied with density functional theory and MP2 method. Formation of the alan dimers and the alan-acetone adduct, and the transition state for the Meerwein-Ponndorf-Verley (MPV) type reduction of the adduct were calculated to figure out the energy profile. Formation of dimeric alans is highly exothermic. Both the relative free energies for acetone-alan adduct formation and the TS barriers for the MPV type reduction with respect to alan dimers and acetone were calculated and they show the same trend. Based on these energetic data, relative reactivity of alans is expected to be; $AlR_2(Cl)$ > $AlR_2(OTf)$ > $AlR_2(O_2CCF_3)$ > $AlR_2(F)$ > $AlR_2(OMs)$ > $AlR_2(OAc)$ > $AlR_2(OMe)$ > $AlR_2(NMe_2)$. The energy profile is relatively well correlated with the experimental order of the reactivity of Al-substituted dialkylalans. It is noted that the substituents of alans have initial effects on the relative free energies for the carbonyl-adduct formation. Therefore, an $AlR_2(X)$ which forms a more stable carbonyl-adduct is more reactive in carbonyl reduction.

Excited State Intramolecular Proton Transfer and Physical Properties of 7-Hydroxyquinoline

  • Kang Wee-Kyeong;Cho Sung-June;Lee Minyung;Kim Dong-Ho;Ryoo Ryong;Jung Kyung-Hoon;Jang Du-Jeon
    • Bulletin of the Korean Chemical Society
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    • v.13 no.2
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    • pp.140-145
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    • 1992
  • The excited state intramolecular proton transfer and physical properties of 7-hydroxyquinoline are studied in various solutions and heterogeneous systems by measuring steady state and time-resolved fluorescence, reflection and NMR spectra. Proton transfer is observed only in protic solvents owing to its requirement of hydrogen-bonded solvent bridge for proton relay transfer. The activation energies of the proton transfer are 2.3 and 5.4 kJ/mol in $CH_3OH$ and in $CH_3OD$, respectively. Dimers of normal molecules are stable in microcrystalline powder form and undergo an extremely fast concerted double proton transfer upon absorption of a photon, consequently forming dimers of tautomer molecules. In the supercage of zeolite NaY, its tautomeric form is stable in the ground state and does not show any proton transfer.

Synthesis of Liquid-Crystalline Polymer Containing Coumarin Moieties by Photopolymerization (Coumarin이 함유된 액정고분자의 광중합)

  • Lee, Jong-Back;Lee, Kwang-Hyun;Kang, Byung-Chul
    • Elastomers and Composites
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    • v.45 no.4
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    • pp.286-290
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    • 2010
  • Liquid-crystalline (LC) monomer, which was functionalized with a coumarin group on their extremity, was synthesized by UV light irradiation in their LC phases. LC monomer was converted into the dimers by the cycloaddition reaction of the coumarin group, and the LC phases were maintained after photodimerization reaction. The dimers showed LC phases in the wider temperature range than those of the corresponding monomer. Structures of the compound were identified by FT IR and $^1H$ NMR spectroscopies. Their phase transition temperatures and thermal stability were also investigated by differential scanning calorimetry (DSC), gel permeating chromatography (GPC) and polarized optical microscopy (POM). From optical polarizing microscopy, the prepared polymer shows enantiotropic liquid crystallinity with smectic and nematic textures.

Neuroprotective Effects of N-Acetyldopamine Dimers from Cicadidae Periostracum

  • Thapa, Punam;Katila, Nikita;Choi, Hyukjae;Han, Ah-Reum;Choi, Dong-Young;Nam, Joo-Won
    • Natural Product Sciences
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    • v.27 no.3
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    • pp.161-168
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    • 2021
  • The chemical investigation of the 90% EtOH extract from Cicadidae Periostracum led to the isolation and identification of seven known N-acetyldopamine dimers (1-7). These compounds were identified by comparing mass spectrometry data and NMR spectroscopic data with those previously reported. In this study, complete interpretation of 1D and 2D NMR data of 1 and 2 were reported for the first time. In addition, compounds 3 and 4 were isolated from this material for the first time. All isolates were obtained as racemic mixtures, as confirmed by chiral HPLC. Furthermore, we evaluated the neuroprotective activities of compounds 1-7 and found that compounds 1, 5, and 6 significantly attenuated rotenone-induced death of SH-SY5Y neuroblastoma cells at a concentration of 100 μM. Parallel to this result, compounds 3 and 6 displayed antioxidant effects in the cytoplasm, as determined by CM-H2DCFDA fluorescence intensity, while compounds 1 and 5 showed antioxidant effects in the mitochondria, as assessed by MitoSox fluorescence intensity. Overall, these results suggest that some of these compounds protect neuroblastoma cells by ameliorating the release of reactive oxygen species. Further studies are warranted to elucidate the underlying mechanisms by which these compounds exhibit antioxidant and neuroprotective actions.

Thermotropic Liquid Crystalline Behavior of α,ω-Bis(4-nitroazobenzene-4'-carbonyloxy)alkanes (α,ω-비스(4-니트로아조벤젠-4'-카보닐옥시)알칸들의 열방성 액정 거동)

  • Jeong, Seung Yong;Hwang, Dong Jun;Ma, Yung Dae
    • Applied Chemistry for Engineering
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    • v.21 no.2
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    • pp.230-237
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    • 2010
  • A homologous series of linear liquid crystal dimers, ${\alpha},{\omega}$-bis(4-nitroazobenzene-4'-carbonyloxy)alkanes (NATWESn, n = 2~8, 10, the number of methylene units in the spacer) have been synthesized, and the thermal behavior of the series has been investigated. All the dimers formed enantiotropic nematic phases. The nematic-isotropic transition temperatures of the dimers and their entropy variation at the phase transition showed a large odd-even effect as a function of n. This behavior was rationalized in terms of the change in the average shape of the spacer on varing the parity of the spacer. The thermal stability and degree of order in the nematic phase and the magnitude of the odd-even effect of NATWESn were very similar to those of the corresponding ether compounds, while they were significantly different from those of the monomesogenic compounds, 4-{4'-(nitrophenylazo)phenoxy}alkanoyl chlorides and the side-chain liquid-crystalline polymers, the poly[1-{4-(4'-nitrophenylazo) phenoxycarbonylalkanoyloxy}ethylene]s. The results were discussed in terms of the 'irtual trimer model'by Imrie.

Thermotropic Liquid Crystalline Properties of α,ω-Bis(4-cyanoazobenzene-4'-oxy)alkanes (α,ω-비스(4-사이아노아조벤젠-4'-옥시)알케인들의 열방성 액정 특성)

  • Jeong, Seung Yong;Kim, Hyo Gap;Ma, Yung Dae
    • Applied Chemistry for Engineering
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    • v.22 no.4
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    • pp.358-366
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    • 2011
  • A homologous series of linear liquid crystal dimers, the ${\alpha},{\omega}$-bis(4-cyano-azobenzene-4'-oxy)alkanes (CATWETn, where n, the number of methylene units in the spacer, is 2~10) were synthesized, and their thermotropic liquid crystalline phase behavior were investigated. The CATWETn with n of 3 and 6 exhibited monotropic nematic phases, whereas other derivatives showed enantiotropic nematic phases. The nematic-isotropic transition temperatures of the dimers and their entropy variation at the phase transition showed a large odd-even effect as a function of n. This phase transition behavior was rationalized in terms of the change in the average shape of the spacer on varying the parity of the spacer. The thermal stability and degree of order in the nematic phase and the magnitude of the odd-even effect of CATWETn were similar to those for the methoxy-, nitro-, and pentyl-substituted dimers, while they were significantly different from those for the monomesogenic compounds, 1-{4-(4'-cyanophenylazo)phenoxy}alkylbromides and the side-chain liquid-crystalline polymers, the poly[1-{4-(4'-cyanophenylazo)phenoxyalkyloxy}ethylene]s. The results were discussed in terms of 'virtual trimer model' by Imrie.