• Title/Summary/Keyword: 라디칼

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Preparation of Polyolefin Based Segmented Copolymers Through Controlled Radical Polymerization Technique (조절 라디칼 중합법에 의한 폴리올레핀 기반 분절 공중합체의 제조)

  • Hong, Sung-Chul;Lee, Seong-Hoon;Cho, Hyun-Chul
    • Elastomers and Composites
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    • v.44 no.3
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    • pp.209-221
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    • 2009
  • Polyolefins are important commodity polymers with the largest volume of business owing to their outstanding combination of cost performance and excellent physical properties. However, the lack of functional groups often has limited their end uses, such as compatibilizer, modifier and adhesive, where the interaction with other materials is especially important. The incorporation of functional groups as polymer segments to afford block or graft polyolefin copolymers has been extensively investigated in the context of the functional polyolefin hybrids. Living polymerization processes have been considered to be an efficient method to prepare the polyolefin hybrids with precisely controlled architecture and compositions. Among the living polymerization techniques, controlled/"living" radical polymerization (CRP) methods are very effective not only because of the controllability of polymerization but also because of the versatility of monomers and polymerization conditions. In this review paper, progresses on the preparations of polyolefin graft or block copolymers through CRP techniques are summarized. The commodity polymers such as polyisobutylene, polyethylene and polypropylene are combined with polar segments such as polyacrylate, polymethacrylate, polystyrene to yield functionalized polyolefins.

Change of Total Polyphenol Content of Fermented Gastrodia elata Blume and Radical Scavenging (발효천마의 총 폴리페놀 함량 변화 및 라디칼 소거능)

  • Park, Mi-Ran;Yoo, Chul;Chang, Young-Nam;Ahn, Byung-Yong
    • Korean Journal of Plant Resources
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    • v.25 no.4
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    • pp.379-386
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    • 2012
  • This study was conducted to compare and analyze change of content of polyphenol and p-hydroxybenzyl alcohol (HBA), which is an index-component, and antioxidant activity between fermented Gastrodia elata Blume and non-fermented G. elata Blume. The polyphenol contents before and after the fermentation were 108.65 and 389.99 mg/mL respectively, and the content of index-component HBA increased from 2.46 mg/g before fermentation to 7.94 mg/g after fermentation. In comparison between the non-fermented G. elata Blume extract (NFGE) and fermented G. elata Blume extract (FGE) in DPPH, ABTS, and superoxide radical scavenging assay, we found that FGE showed more activity than NFGE as the extract was more concentrated. Especially, the superoxide radical scavenging activity was increased more than twenty times in FGE. In conclusion, we confirmed increase in the electron donating ability and radical scavenging when the dried G. elata Blume is fermented, and its further feasibility as an antioxidant.

Degradation of Nafion Membrane by Oxygen Radical (산소 라디칼에 의한 Nafion 막의 열화)

  • Kim, Taehee;Lee, Junghun;Cho, Gyoujin;Park, Kwonpil
    • Korean Chemical Engineering Research
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    • v.44 no.6
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    • pp.597-601
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    • 2006
  • The degradation of the Nafion membrane by oxygen radical (OH, $HO_2$) was investigated in Polymer electrolyte membrane fuel cell (PEMFC). Nafion membrane was degraded in Fenton solution consisted with hydrogen peroxide (10-30%) and ferrous ion (1-4 ppm) at $80^{\circ}C$. After degradation in Fenton solution, C-F, S-O and C-O chemical bonds of membrane were broken by oxygen radical attack. Breaking of C-F bond reduced the mechanical strength of Nafion membrane, and hence induced pinholes, resulting in increase of $H_2$ crossover through the membrane. Decomposition of S-O and C-O bonds decreased the ion exchange capacity of the electrolyte membrane. The performance of unit cell composed the membrane, which was degraded in 30% $H_2O_2$ with 4ppm $Fe^{2+}$ solution for 48 hr, was about half times as low as one with normal membrane.

Evaluation of Hydroxyl radical Formation and Energy Distribution in Photolysis Reactor (광반응 반응기 내부의 에너지 분포와 라디칼 생성에 대한 연구)

  • Nam, Sang-Geon;Hwang, An-Na;Cho, Sang-Hyun;Lim, Myung-Hee;Kim, Jee-Hyeong
    • Journal of the Korean Society of Hazard Mitigation
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    • v.11 no.2
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    • pp.179-183
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    • 2011
  • In this study, photochemical effects (OH radical formation) in the photoreactor was investigated to analyze UV-C intensity distribution. In addition, The influence radius of the UV-C lamp was measured at various dose of $TiO_2$ (Degussa P-25). The photoreactor used in this study was bath type reactor which is made by acrylic and the UV-C lamp (SANKYO DENKI, wavelength : 254 nm, Diameter : 2.2 cm, Length : 18.5 cm) was used as photo source. The maximum electric power consumption of the UV lamp was 10.5 W. The OH radical formation by UV-C was measured by KI dosimetry methods. From the results, the effective OH radical formation was occurred under the following condition. The reasonable distance of UV-C lamp is within 13 cm and the intensity of UV-C lamp should be more than 0.367 mW/$cm^2$. Moreover, the concentration of catalyst affects on the influence radius of the UV lamp.

In vitro antioxidant activity of black tea (Camellia sinensis L.) residue extract (홍차박 추출물의 in vitro 항산화 활성)

  • Kim, Dong Chung
    • Journal of Applied Biological Chemistry
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    • v.62 no.3
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    • pp.281-286
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    • 2019
  • A black tea (Camellia sinensis L.) residue extract (BTRE) was prepared by 30% ethanol extraction to evaluate its in vitro antioxidant activity. The yield and polyphenol content of BTRE were $22.4{\pm}1.18%$ and $23.2{\pm}1.02{\mu}g$ gallic acid equivalents/mg-extract, respectively. Antioxidant activity of BTRE proportionally increased as BTRE concentration increased. $IC_{50}$ values of BTRE for cation radical, free radical and nitrite scavenging were 141.8, 108.1, and $397.2{\mu}g/mL$, respectively. Also $IC_{50}$ value of BTRE for ferric reducing anti-oxidant power was $97.8{\mu}g/mL$. BTRE effectively inhibited linoleic acid peroxidation. These results imply that BTRE possessed potent antioxidant activity, thus being utilized as a physiologically active material.

Comparison of Degradation due to Fenton Reaction between Reinforced and Non-reinforced Membranes Used in PEMFC (PEMFC에 사용되는 강화막과 비강화막의 Fenton 반응에 의한 열화 비교)

  • Oh, Sohyeong;Yoo, Donggeun;Lee, Mihwa;Park, Jisang;Park, Kwon-Pil
    • Korean Chemical Engineering Research
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    • v.59 no.4
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    • pp.508-513
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    • 2021
  • In order to improve the durability of a proton exchange membrane fuel cells (PEMFC), it is essential to improve the durability of the polymer membrane. In order to improve the durability of the membrane, an e-PTFE support and a radical scavenger are added. In this study, the chemical durability of the reinforced membrane with ePTFE support and the non-reinforced membrane was compared by Fenton reaction. In the Fenton experiment of the polymer membrane without the addition of a radical scavenger, the absorption rate of hydrogen peroxide solution and iron ions through the cross section of the specimen cut into small pieces was higher in the reinforced membrane, so that the fluorine outflow concentration was higher. According to the type and amount of radical scavenger added, the fluorine outflow concentration of the reinforced membrane has a large difference of more than 3 times, indicating that the effect of the radical scavenger was stronger than that of the support.

Antioxidant activities of phenolic compounds from Ziziphus jujuba Mill extract using subcritical water (대추 아임계수 추출물의 폴리페놀 함량 및 산화방지 평가)

  • Ko, Min-Jung;Kwon, Mi-Ri;Chung, Myong-Soo
    • Korean Journal of Food Science and Technology
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    • v.53 no.3
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    • pp.329-333
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    • 2021
  • Subcritical water extraction (SWE) is an eco-friendly extraction method that uses only purified water as a solvent under high temperature and high pressure conditions. In this study, total phenolics, and antioxidant activity were evaluated in Ziziphus jujuba Mill extracts from subcritical water obtained by varying the extraction temperature (110-190℃) and extraction time (1-20 min). Total phenolics was maximized with extraction at 190℃ for 15 min (67.79±3.45 mg gallic acid equivalent/g jujube). The 2,2-diphenyl-1-picrylhydrazyl free radical scavenging activity (48.84±4.74%) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) free radical scavenging activity (84.75±1.15%) were maximal at extraction conditions of 190℃, for 20 min. All jujube extracts prepared using SWE had higher total phenolics and antioxidant activities than extracts prepared using organic solvent extraction (60℃, 120 min), including methanol and ethanol. SWE could be an excellent alternative to organic solvents for extracting phenolics and antioxidant compounds.

Inhibitory effects of advanced glycation end products formation and free radical scavenging activity of Cirsium setidens (곤드레 추출물의 최종당화산물의 생성저해 및 라디칼소거 활성)

  • Kim, Taewan;Lee, Jaemin;Jeong, Gyeong Han;Kim, Tae Hoon
    • Food Science and Preservation
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    • v.23 no.2
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    • pp.283-289
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    • 2016
  • Naturally occurring antioxidants, such as polyphenols are widely found in fruits, vegetables, wines, juices, and other plant-based dietary sources and are divided into several sub classes, including phenylpropanoids, flavonoids, stilbenoids, and lignans. As part of the our ongoing search for bioactive food ingredients, the antioxidant and advanced glycation end products (AGEs) formation inhibitory activities of the methanolic extract of the aerial parts of Cirsium setidens were investigated in vitro bioassay system. The antioxidant properties were evaluated through radical scavenging assays using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) ($ABTS^+$) radicals. In addition, the activity of C. setidens against diabetes complications was also tested via AGEs formation inhibition assay. The total phenolic contents were determined using a UV-VIS spectrophotometric method. All tested samples showed a dose-dependent radical scavenging and AGEs inhibitory activities. In particular, the n-butanol (BuOH)-soluble portion showed the most potent radical scavenging activities against DPPH and $ABTS^+$ radicals with $IC_{50}$ values of $24.3{\pm}1.7$ and $25.0{\pm}3.3{\mu}g/mL$, respectively. Futhermore, the inhibition of AGEs formation by the n-BuOH-soluble portion ($IC_{50}$ value; $46.0{\pm}1.5{\mu}g/mL$) was higher than that those of the soluble portions for the other solvent. The results showed that C. setidens could be considered as an effective source of natural antioxidants and other ingredients.

Anti-oxidative Activities of Commercial Edible Plant Extracts Distributed in Korea (국내 유통 중인 식용식물 추출물의 항산화효과)

  • Kim, Kyung-Bum;Yoo, Ki-Hwan;Park, Ha-Yan;Jeong, Jong-Moon
    • Applied Biological Chemistry
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    • v.49 no.4
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    • pp.328-333
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    • 2006
  • Many plant extracts are known to have antioxidative effects. However, their activities can be reduced or disappeared during mass production process. The purpose of this study is to compare antioxidative effects of edible plant extracts distributed in Korea. forty three kinds of edible plant extracts commercially available in Korea were selected and investigated for their total phenolics contents and antioxidative potentials(DPPH radical and superoxide anion radical scavenging activities). In contents of total phenolics, the commercial plant extracts from Artemisia annua(whole plant), Ilex paraguariensis(leaf, Silybum marianum(fruit and leaf, Ulmus pumila(bark), Coliolus versicolor(fruit), and Curcuma longa(root and stem) contained over 70 mg/g of powder, DPPH radical scavenging activities($SC_{50}$, 50% scavenging concentration) of A. annua, I. paraguariensis, Pinus densiflora(leaf),S. marianum, U. pumila, and C. longa were $53.96{\pm}0.81\;ppm,\;24.61{\pm}2.12\;ppm,\;35.96{\pm}1.11\;ppm,\;57.46{\pm}2.13\;ppm,\;55.25{\pm}1.65\;ppm\;and\;12.99{\pm}1.67ppm$, respectively, while that of positive control(vitamin C) was $3.86{\pm}0.81\;ppm$. $SC_{50}$ values against superoxide anion radical of A. annua, Cinnamomum zeylanicum(bark), I. paraguariensis, Rubus coreanus(fruit and leaf), Morus alba(leaf), P. densiflora, S. marianum, U. pumila, C. versicolor, C. longa, Perilla frutescens var. acuta(leaf), and H. sabdariffa(leaf and newer) were $53.21{\pm}1.83ppm,\;50.12{\pm}2.12ppm,\;5.59{\pm}0.84ppm,\;41.60{\pm}8.93ppm,\;20.19{\pm}0.97ppm,\;15.19{\pm}1.66ppm,\;21.20{\pm}1.88ppm,\;15.71{\pm}0.91ppm,\;55.48{\pm}2.42ppm,\;52.12{\pm}2.44ppm,\;23.80{\pm}1.98ppm\;and\;11.14{\pm}0.51ppm$, respectively($SC_{50}$ value of vitamin C: $9.61{\pm}0.93ppm$). In particular, both 1 paraguariensis and P. densiflora had high content of phenolics as well as high scavenging activities of DPPH radical and superoxide anion radical. Consequently, above two commercial extracts may be useful as a source of antioxidative nutraceutics.

Investigation of DPPH Radical Scavenging and Pyolyl Endopeptidase Inhibitory Activities of Plant Extracts (천연 식물자원에서 DPPH 라디칼 제거능과 Prolyl Endopeptidase 활성 저해능 탐색)

  • Lee Young Min;Kim Dae Ik;Lee Sung Hyeon;Cho Soo Muk;Chun Hye Kyung;Park Hong Ju;Lee Yeon Sook
    • The Korean Journal of Community Living Science
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    • v.16 no.4
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    • pp.95-102
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    • 2005
  • The present study was performed to investigate the 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical scavenging and Proly1 endopeptidase (PEP) inhibitory activities of plant extracts. The whole extract of Fragaria yezoensis inhibited the DPPH radical by $90.4\%$ and the stem of Gingko biloba, Gardenia jasminoides for. grandiflora and Rhododendron yedoensa var. poukhanene, the loaves of Rhododendron mucronulatum var. ciliatum, Gardenia jasminoides for. grandiflora and Corylus sieboldiana var. mandshurice, the fruit of Cornus officinalis, and the root of Gingko biloba showed high DPPH radical scavenging activities. In the case of PEP inhibitory activities, high inhibition was observed in the whole Plant of Fragaria ananassa, Fragaria yezoensis and Hypericum erectum, the stem of Actinidia arguta and Rhododendron yedoensa var. poukhanese, the leaves of Rhododendron yedoensa var. poukhanense and Rosa davurica, the fruit of Cornus officinalis. and the root of Acer okamotoanum. There was significant correlation (P=0.000) between DPPH radical scavenging and prolyl endopeptidase inhibitory activities, thus some of plant extracts such as whole Fragaria yezoensis, fruit of Cornus officinalis had high activities in both DPPH-scavenging and prolyl endopeptidase inhibition. Therefore, it is required to examine the mechanical interaction between DPPH-scavenging and prolyl endopeptidase inhibitory activities and further studying plant extracts with both these activities is desired to develop agents for preventing and treating of Alzheimer's disease.

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