• Polymer(Korea)
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• v.39 no.1
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• pp.56-63
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• 2015

The object of this study is to prepare microcapsules containing a diisocyanate compound, apply them to self-healing protective coating, and evaluate the self-healing capability of the coating by atmospheric moisture. Isophorone diisocyanate (IPDI) polymerized under humid atmosphere, indicating that IPDI can be used as a healing agent. Microencapsulations of IPDI were conducted via interfacial polymerization of a polyurethane prepolymer with diol compounds. The formation of microcapsules was confirmed by Fourier-transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy. The mean diameter, size distribution, morphology and shell wall thickness of microcapsules were investigated by optical microscopy and scanning electron microscopy (SEM). The properties of microcapsules were studied by varying agitation rates and diol structure. The self-healing coatings were prepared on test pieces of CRC board. When scratch was generated in the coatings, the core material flew out of the microcapsules and filled the scratch. The self-healing coatings were damaged and healed under atmosphere with 68~89% relative humidity for 48 h, and SEM and impermeability test for the specimens showed that the scratch could be healed by atmospheric moisture.

• Microbiology and Biotechnology Letters
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• v.37 no.2
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• pp.133-139
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• 2009

Yam (Dioscorea batatas Decne) has been recognized as healthy food due to its various biological activities, such as anti-obesity, anti-constipation, anti-proliferation, anti-mutagenic activity, and decrease of blood glucose and cholesterol level. In this study, the methanol extract and its organic solvent fractions were prepared from dried Dioscorea batatas Decne, and their antimicrobial, antithrombin, and antioxidant activity were evaluated, respectively. The 66.7% of methanol extract was fractioned into water residue, and most of total-polyphenol/total-flavonoids were found in ethylacetate fraction. This ethylacetate fraction at $500\;{\mu}g/disc$ concentration showed strong antibacterial activity against gram-negative and gram-positive bacteria, except Staphylococcus aureus. Antifungal activity was not observed in methanol extract and its fractions. But, strong antithrombin activity was found in methanol extract. At 4.8 mg/mL concentration, thrombin time was 99.5 sec, which is coincides with 30% activity of aspirin, a commercial available antithrombosis agent. The ethylacetate fraction showed strong DPPH scavenging activity ($IC_{50}$ of $80.5\;{\mu}g/mL$), compared to vitamin C ($IC_{50}$ of $15.2\;{\mu}g/mL$). Also, the ethylacetate fraction showed strong SOD-like activity and reducing power, which are coincide with 43% of vitamin C and 82.7% of butylated hydroxytoluene activity, respectively.

• Korean Journal of Food Science and Technology
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• v.47 no.5
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• pp.680-685
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• 2015

Phytochemicals in Codonopsis lanceolata leaves were saponins, triterpenes, tannins, and flavonoids, not alkaloids. The levels of total polyphenols and flavonoids in Codonopsis lanceolata leaves were measured to evaluate the antioxidant activity. C. lanceolata leaves showed strong 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and potent reducing power. In addition, C. lanceolata leaf extracts inhibited production of nitric oxide (NO) in lipopolysaccharide (LPS)-activated RAW 264.7 cells. To examine active phytochemical for antioxidant activity, aglycone fraction of C. lanceolata leaves was analyzed by high performance liquid chromatography (HPLC). Luteolin was identified as a main component of aglycone fraction and showed potent antioxidant activity as determined by a DPPH radical scavenging assay and reducing power test. These results suggest that C. lanceolata leaves are a good source of antioxidants.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.2
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• pp.634-643
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• 2020

In this study, the rheological and tribological properties of urea grease were studied according to the type and amount of polytetrafluoroethylene (PTFE) powders added to the urea grease, which is the most widely used among solid lubricants, to develop an optimal lubrication system. Urea grease was synthesized using 4,4'-methylenebis(phenyl isocyanate)(MDI), oleylamine, and cyclohexylamine, and PTFE powders prepared by dispersion or suspension polymerization process were then added. The basic rheological and tribological properties of the prepared greases were compared. The worked penetration numbers of urea grease decreased with increasing amount of PTFE powders, but both PTFE powders caused no significant changes in heat resistance and copper corrosion resistance. The shear viscosity increased with increasing PTFE powder content, and the dispersion-type PTFE powder was more effective in increasing the viscosity. In the value of the loss coefficient = 1, the shear stress was higher for the grease containing PTFE powders than the non-PTFE added grease, and the dispersion-type PTFE-added grease showed higher viscosity than the suspension-type PTFE-added grease. Finally, urea grease was found to have a low-performance improvement in terms of wear reduction effects by adding PTFE powders, but the load-bearing performance was up to 2.5 times higher for the dispersion-type PTFE and five times higher for the suspension-type PTFE.

• Microbiology and Biotechnology Letters
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• v.37 no.3
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• pp.266-272
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• 2009

The annual productions of yam and its aerial bulbils are estimated to 5,000 and 2,500 ton, respectively. But the majority of bulbils had been discarded without specific use. In this study, methanol extract and its organic solvent fractions were prepared from bulbils of Dioscorea batatas Decne, and their antimicrobial, antithrombin, and antioxidant activities were evaluated, respectively. The methanol extract contained 58.98% of water-soluble materials as like yam's extract. But the bulbils's extract contained 12-folds of total polyphenol and 3.4-folds of total flavonoids compared than yam's extract, respectively. For antimicrobial activity the hexane and ethyl acetate fraction showed strong antibacterial activity at $500{\mu}g/disc$ concentration against gram-negative and gram-positive bacteria. Antifungal activity was not observed in any fractions. Strong antithrombin activity was found in the hexane fractions. At 4.8 mg/mL concentration thrombin time (TT) was over 300 sec, which is 4-folds extended than the TT of yam. In a while, the ethyl acetate fraction showed strong DPPH scavenging activity ($IC_{50}$ of $38.1{\mu}g/mL$), SOD-like activity and reducing power, which are comparable to vitamin C or BHT. Our results suggest that the bulbils of yam as yam tuber have useful bio-activities, such as antibacterial, antithrombosis, and antioxidant activity.

• Journal of the Korean Chemical Society
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• v.54 no.3
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• pp.261-268
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• 2010

In this account, three synthetic methodologies that serve as the basis for new strategies for the preparation of selected natural products are briefly introduced. One process, involving ruthenium carbene catalyzed ring rearrangement metathesis developed by Grubbs and his coworkers, transforms alkene-tethered cycloalkenes to thermodynamically more favored alkene-tethered cycloalkenes. Another ruthenium carbene promoted reaction, referred to as dienyne metathesis, was uncovered in early studies by Grubbs and his collaborators. This process converts dienynes to fused bicyclic conjugated dienes. Finally, a novel photo-electrocyclization reaction of pyridinium salts, which leads to the formation of 4-aminocyclopenten-3,5-diol derivatives, is discussed. Examples are provided to show the utility of these methodologies in natural product synthesis. Emphasis is given to studies in which pyridinium salt photochemistry is coupled with ring rearrangement and dienyne metathesis in routes for the synthesis of polyhydroxyalted indolizidine alkaloids and the construction of the tricyclic core of the lepadiformine and cylindricine alkaloids.

• Polymer(Korea)
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• v.31 no.2
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• pp.98-104
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• 2007

The expansion behavior of polystyrene (PS) chains with various molecular weights has been investigated above Flory $\Theta$temperature by viscometry after dissolving in the three different mixed solvents systems such as benzene/n-heptane, 1,4-dioxane/isopropanol, and 1,4-dioxane/n-heptane. Two different regimes are observed as increasing temperature: one regime is for the expansion of chain and the other is for the contraction. For the higher molecular weight sample of PS, the higher peak temperature showing its maximum expansion is obtained. Within a certain system of Ps/mixed solvents, the $\tau/\tau_c$ parameter shows universality for the variation of molecular weight. But while each system of Ps/mixed solvents has shown its own different slope, the universality breaks down in the overall system of mixed solvents. However after introducing a new empirical $b^{2/3}\tau/\tau_c$ parameter, all data points of three different systems have dropt on one master curve and the universality of chain expansion has recovered again. Here $\tau$ and $\tau_c$ are defined as $(T-\Theta)/\Theta$ and $(\Theta-T_c)/T_c$, respectively and $T_c$ is the critical solution temperature, and b of Schultz-Flory equation is corresponding to the effective slope in the plot of $1/T_c$ against $1/M_w^{1/2}$.

• Journal of the Korean Applied Science and Technology
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• v.38 no.3
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• pp.651-661
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• 2021

Eruca sativa, called arugula, is a perennial plant in the Brassicaceae family, an edible plant commonly used in Italian cuisine. To study as a cosmetic material application E. sativa was extracted with 70% ethanol (ES). Then ES was fractionated using n-hexane, chloroform, ethyl acetate, n-butyl alcohol and water (EHex, EEA, ECHCl₃, EBuOH and EDW). EEA showed mushroom tyrosinase inhibitory activity. ES, EEA and EBuOH showed inhibition of tyrosinase activity. As a result, ES is expected to have skin whitening efficacy. ES was applied to 0.05, 0.1% the toner and emulsion formulation to test the stability. The anti-microbial activity of eight bacteria and fungi including Staphylococcus aureus and Propionibacterium acnes which cause dermatitis and acne was evaluated. EEA showed effects in all of microorganisms. The toner and emulsion containing ES with 0.05, 0.1% were passed in the challenge test. At -20, 4, 25, 55 ℃ and daylight, there was no significant change on pH, viscosity for 4 months. However, emulsions had phase separation phenomenon at 55 ℃, so the base formulation needs improvement. In addition, through the skin penetration test, EEA penetrated 0.058% in 6 hr, predicting the clinical efficacy. This means that E. sativa can contribute whitening agent and the synergistic effect of preservatives.

• Journal of Life Science
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• v.33 no.1
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• pp.43-49
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• 2023

Houttuynia cordata belongs to the Saururacease family and its leaves, stems, and roots have been used as oriental medicines to treat pneumonia, acute or chronic bronchitis, enteritis, and abscesses and to remove extravasated blood. Recently, the antioxidant, anti-inflammation, antibacterial, and anti-proliferation activities and protection abilities of H. cordata against liver and neuron cell damage have been reported. In this study, ethanol extract and its solvent fractions (fractions of hexane, ethyl acetate, butanol, and water residue) were prepared, and their antithrombosis, antidiabetes, antioxidant, and hemolysis activities were evaluated. The ethyl-acetate fraction of H. cordata (EF-HC) showed the highest polyphenol and flavonoids contents among the fractions and exhibited strong antithrombosis and antioxidant activities. The EF-HC at 5 mg/ml showed 2.09-folds of thrombin time, 2.19-folds of prothrombin time, and 1.69-folds of activated partial thromboplastin time compared to the their solvent control and 30.9, 19.9, and 49.6 ㎍/ml of RC₅₀ against DPPH, ABTS, and nitrite radicals, respectively. Furthermore, the EF-HC did not show any hemolytic activity up to 1 mg/ml, whereas the hexane fraction of H. cordata showed 55% hemolysis at 1 mg/ml. This is the first report of the antithrombosis activity of H. cordata. Our results suggest that quercitirin, hyperoside, orientin, and isoquercitrin in EF-HC are related to its antithrombosis and antioxidant activities and that the EF-HC could be developed as a promising antithrombosis agent.

• Journal of Applied Biological Chemistry
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• v.66
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• pp.503-511
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• 2023

The aim of this study was to investigate in vitro antioxidant activities of defatted Camellia japonica L. seeds (DCJS). The DCJS were extracted using ethanol and then fractionated with butanol (BuOH), ethyl acetate (EtOAc), chloroform, and hexane. To evaluate antioxidant activity of extract and fractions from DCJS, we investigated free radical scavenging activities such as 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS⁺), hydroxyl radical (^•OH), and superoxide anion (O₂^-) radicals. The five extract and fractions of DCJS dose-dependently increased DPPH, ABTS⁺ and O₂^- radical scavenging activities. The BuOH fraction of DCJS showed the highest free radical scavenging activities among other extract and fractions. The contents of total polyphenol and flavonoid in BuOH fraction of DCJS were 23.26 mg GAE/g and 32.39 mg QE/g, respectively. The polyphenol and flavonoids contents of BuOH fraction has highest than other extract and fractions. In addition, BuOH and EtOAc fraction of DCJS contained 102.37 and 165.05 ㎍/g of camelliaside B, respectively. Therefore, DCJS has higher antioxidant activity and may be useful as a natural antioxidant material.