• Journal of the Korean Chemical Society
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• v.34 no.3
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• pp.239-247
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• 1990

The gas-phase S_N2$ reactions can be classified into neutral bimolecular, solvated, and ionic reactions; the neutral bimolecular reaction proceeds via retention mechanism whereas the ionic reaction produces inversion products. In the reaction of solvated nucleophile with one solvent molecule, a six-center transition state (TS) is formed and the two processes i.e., retention and inversion, are found to compete with a favored path depending on the electronic effect of the nucleophile and substituents in the substrate and on the steric requirement. In the ionic reaction, the difference in the energy barrier between the two processes reduces to a small value when the substrate methyl group is made bulky, leaving ability of the leaving group is improved and at the same time the negative charge of the nucleophile is dispersed. When the reaction center atom in the $S_N2$ reaction is changed to a larger sized second row elements, the activation barrier decreases since the steric crowding in the penta-coordinated TS is relieved. However within the same row, the barrier was found to increase as the atomic size decreased. For the boron, B, the barrier height was the least since in addition to the relatively large atomic size compared to C and N, it forms tetra-coordinated TS so that the steric crowding becomes nearly negligible.

• Food Science and Preservation
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• v.21 no.5
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• pp.727-734
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• 2014

To investigate anti-thrombosis and anti-oxidation activities of the root of Arctium lappa L (RALL), which has been used as foodstuff and oriental medicine in Korea, the ethanol extract and its subsequent organic solvent fractions of the RALL were prepared. The yield of ethanol extraction was 10.94%, and the content of total polyphenol and total sugar of ethanol extract were 5.01 and 694.53 mg/g, respectively. The fraction yields of n-hexane, ethylacetate (EA), butanol and water residue were 1.62, 0.42, 5.98 and 85.38%, respectively. In anticoagulation activity assay, the ethanol extract of RALL did not show significant changes in thrombin time (TT), prothrombin time (PT) and activated partial thromboplastin time (aPTT), whereas the EA fractions showed 13 folds extended TT, PT, and aPTT respectively. Interestingly, the water residue showed strong activation effect against blood clotting factors with shortened aPTT, which might provide the evidence of coagulation agent of RALL in folk remedy. In anti-platelet aggregation assay, the activity of the ethanol extract and its fractions were comparable to that of aspirin. Especially the EA fraction showed 2-folds higher inhibitory activity than aspirin. In anti-oxidation activity assay, the EA fraction also showed strong in DPPH, ABTS and nitrite scavenging activity, and reducing power activity. The extract and fractions of RALL have ignorable hemolytic activity against human RBC up to 0.5 mg/mL concentration. Our results suggest that the EA fraction of RALL have potentials as safe and novel anti-thrombosis agent.

• Food Science and Preservation
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• v.24 no.5
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• pp.673-679
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• 2017

In this study, the antimicrobial, antioxidant activities and ${\alpha}$-glucosidase inhibitory activities of Amphidinium carterae ethanol extract (AE) was evaluated for using as a functional food ingredient. Chlorella ethanol extract (CE) was used to the comparison as a control. Anticancer activities of the AE and CE were analyzed by HepG2 and HT-29 human cancer cell. The AE showed antimicrobial activities for all tested bacterial strains. Whereas, CE showed antimicrobial activities for several tested bacterial strains only. The CE showed higher total phenolics contents, DPPH and ABTS radical-scavenging activities (47.36 mg/g, 22.42% and 28.58%, respectively) than those of AE (8.88 mg/g, 20.16% and 17.69%, respectively). AE showed anti-diabetic effect on ${\alpha}$-glucosidase inhibitory activity with dose-dependantly manner. The cell viability of AE ($125{\mu}g/mL$) on HepG2 and HT-29 human cancer cells were 38.12% and 11.27%, respectively. It was demonstrated that ethanol was efficient solvent for extracting functional components from A. carterae. These results indicated that AE can be described as a good candidate for using as a functional food ingredient.

• Korean Journal of Plant Resources
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• v.25 no.2
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• pp.271-276
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• 2012

To develop antiobese food materials from medicinal plants, isolation of antiobese active compounds in $Yukeuigambitang$ of which activity was already proved in the previous study by animal experiments was performed. Antiobese effect of stepwise solvent fractions from 70% ethanol extract of $Yukeuigambitang$ was determined by the differentiation inhibition activity on 3T3-L1 preadipocytes. CH2Cl2 fraction had significant antiobese activity, and n-Hexane and EtOAc fractions were the next. Three phenolic compounds from $CH_2Cl_2$ fraction were identified by GC/MS analysis and one compound was finally isolated by HPLC. It was revealed as a new compound presumed to be one of the derivatives produced from the medicinal plants mixture in $Yukeuigambitang$.

• Polymer(Korea)
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• v.32 no.1
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• pp.26-30
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• 2008

This study was designed to investigate the effect of hybridization of synthetic/natural materials for annulus fibrosus (AF) tissue regeneration in vitro and in vivo. The synthetic/natural hybrid scaffolds were prepared using PLGA (poly (lactic-co-glycolic) acid), SIS (small intestinal submucosa) and DBP (demineralized bone particles). PLGA, PLGA/SIS(20%), PLGA/DBP(20%) and PLGA/SIS (10%)/DBP (10%) scaffold were manufactured by solvent casting/salt leaching method. Compressive strength was measured. Rabbit AF cells were isolated, cultured and seeded into experimental groups. Hydroxyproline production and DNA quantity of AP cells on each scaffold was measured at 2, 4 and 6 weeks after in vitro culture. Cell-scaffold composites were implanted subcutaneously into athymic mice. After 1,4 and 6 weeks postoperatively, specimens were taken and H&E, Safranin-O and type I collagen staining were carried out concerning formation of cartilagenous tissue. In vitro PLGA/SIS scaffold was evaluated for total collagen content (bydroryproline/DNA content) and PLGA scaffold was evaluated for compressive strength.

• Polymer(Korea)
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• v.31 no.3
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• pp.189-193
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• 2007

We developed the doxorubicin-loaded PLGA double-layered microspheres using relatively simple oil-in-water (O/W) solvent evaporation method for sustained release of doxorubicin and investigated the release behavior according to PLGA molecular weight and initial drug loading. The double-layered microsphere was characterized on the surface, the cross-section morphology, the behavior of doxorubicin release for 5 weeks by SEM and fluorescence spectrophotometer. Double-layered microspheres showed smooth surfaces and clear difference between core and outer-shell. As the PLGA molecular weight increased, the release rate of doxorubicin-loaded, double-layered microspheres decreased. These results showed that the release behaviors can be controlled by the variation of molecular weight of PLGA.

• Journal of Life Science
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• v.26 no.9
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• pp.1074-1081
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• 2016

Mistletoes are hemi-parasitic plant growing on different host tree and shrubs. They are traditionally used in folkloric medicine for the treatment of diarrhea, cough, diabetes, hypertension, cancer and skin infection. The purpose of this study was to determine the contents of phenolics and antioxidant activity of 70% ethanol, 100% methanol and hot water extracts of Jeju camellia mistletoe (Korthalsella japonica Engl.). Ethanol was most effective in extracting total phenols (7,427 mg gallic acid equivalent (GAE)/100 g) and flavonoid (1,777 mg rutin equivalent (RE)/100 g). The free radical scavenging activity, 1,1-diphenyl-2-picryl hydrazyl (DPPH) (EC₅₀ = 7.8 mg/ml) and hydrogen peroxide (H₂O₂) (EC₅₀ = 1.4 mg/ml), and the capacity for chelating metal ions (EC₅₀ = 8.0 mg/ml) and reducing power (EC₅₀ = 14.9 mg/ml) of the samples also higher in ethanolic extracts. The strong correlation (r² = −0.996～−0.881) between antioxidant capacities and the phenolic contents implied that phenolic compounds are a major contributor to the antioxidant activity of the ethanolic extracts of Jeju camellia mistletoe. As conclusions, Jeju camellia mistletoe contains bioactive substances with a potential for reducing the physiological as well as oxidative stress and this could explain the suggested cancer preventive effect of these plants as well as their protective role on other major diseases.

• Korean Journal of Food Science and Technology
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• v.29 no.4
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• pp.641-647
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• 1997

Volatile flavor components in whole edible portion, stem and leaf of fresh angelica (Angelica keiskei Koidz) were extracted by SDE (simultaneous steam distillation and extraction) method using the mixture of n-pentane and diethylether (1:1, v/v) as an extract solvent and analyzed by GC-FID and GC/MS. Identification of the volatile flavor components in aroma concentrate was mostly based on the RI of GC and mass spectrum of GC/MS. Twenty five hydrocarbons, 15 alcohols, 3 aldehydes, 6 esters, 2 ketones and 1 acid were identified in the whole edible portion of angelica. Twenty hydrocarbons, 13 alcohols, 4 esters and 1 acid were identified in the stem sample of angelica. Nineteen hydrocarbons, 11 alcohols, 4 aldehydes, 6 esters, 2 ketones and 1 acid were identified in the leaf sample of angelica. ${\gamma}-Terpinene$, germacrene B, ${\delta}-3-carene$, cis-3-hexen-1-ol, ${\gamma}-muurolene$ and ${\gamma}-elemene$ were the main components in each edible portions of angelica. The terpenoid compounds in volatile flavor components identified from whole edible portion, stem and leaf samples were confirmed as 75.76%, 86.42% and 78.21%, respectively. These results suggest that terpenoid compounds have a great effect on the flavor characteristics of angelica.

• Membrane Journal
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• v.26 no.3
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• pp.220-228
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• 2016

Carbon molecular sieve (CMS) hollow fiber membranes were prepared by carbonizing a polyimide precursor manufactured by non-solvent induced phase separation process. Gas separation performance of CMS hollow fiber membrane was investigated on the effect of three carbonization conditions. CMS membrane with the highest gas separation performance was obtained at the pyrolysis temperature of $250-450^{\circ}C$: $N_2$, $SF_6$, and $CF_4$ permeance were 20, 0.32, 0.48 GPU, respectively, and $N_2/SF_6$ and $N_2/CF_4$ selectivities were 62 and 42, respectively. In the $SF_6/CF_4/N_2$ mixture gas test, when the stage cut was 0.2, the recovery ratio of $SF_6$ and $CF_4$ was over 99% and 98%. $SF_6$ concentration ratio was 4.5 times higher than the $SF_6$ concentration at the feed side. From the results, it was concluded that CMS membrane was one of the promising membranes for recovery Perfluorocompound gases process.

• Membrane Journal
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• v.22 no.3
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• pp.224-233
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• 2012

To improve permeation performance of gas separation membrane, polysulfone hollow fiber membrane was prepared by wet-dry phase inversion method using Triton X-100 as non-ionic additive. And variation of gas permeation behavior by additive was investigated. Various spinning conditions such as air gap, concentration of polymer, dope tank temperature were controlled and these effects were studied. The morphology and gas permeation property of hollow fiber membranes were investigated using scanning electron microscope (SEM) and bubble flow meter respectively. We confirmed that the membranes added with Triton X-100 had a smooth external skin at various air gap length conditions. The macrovoids of these hollow fiber membranes were more developed with increase of air-gap from 4 to 90 cm and that induced higher permeance. The permeance of polysulfone membranes has the higher value at comparatively lower concentration polymer (30 wt% polysulfone) and lower concentration of additive (15 wt% Triton X-100). When temperature in dope tank was controlled, the membranes prepared at $100^{\circ}C$ showed low permeance because of volatilization of additive and solvent.