• Bulletin of the Korean Chemical Society
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• 제31권6호
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• pp.1589-1595
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• 2010

In order to effective degradation of organic dye both under visible light or ultrasonic irradiation, the MWCNTs (multiwalled carbon nanotube) deposited with Fe and $TiO_2$ were prepared by a modified sol-gel method. The Fe/$TiO_2$-MWCNT catalyst was characterized by surface area of BET, scanning electron microscope (SEM), Transmission Electron Microscope (TEM), X-ray diffraction (XRD), and energy dispersive X-ray (EDX) and ultraviolet-visible (UV-vis) spectroscopy. The low intensity visible light and low power ultrasound was as an irradiation source and the methylene blue (MB) was choose as the model organic dye. Then degradation experiments were carried out in present of undoped $TiO_2$, Fe/$TiO_2$ and Fe/$TiO_2$-MWCNT catalysts. Through the degradation of MB solution, the results showed the feasible and potential use of Fe/$TiO_2$-MWCNT catalyst under visible light and ultrasonic irradiation due to the enhanced formation of reactive radicals as well as the possible visible light and the increase of ultrasound-induced active surface area of the catalyst. After addition of $H_2O_2$, the MB degradation rates have been accelerated, especially with Fe/$TiO_2$-MWCNT catalyst, in case of that the photo-Fenton reaction occurred. The sonophotocatalysis was always faster than the respective individual processes due to the more formation of reactive radicals as well as the increase of the active surface area of Fe/$TiO_2$-MWCNT catalyst.

• Preventive Nutrition and Food Science
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• 제7권1호
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• pp.67-71
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• 2002

Capsaicin (trans-8-methyl-N-vanillyl-6-nonenarnide), a major pungent component of hot pepper, is known to exert antioxidative properties. In this study, we investigated the protective effects of capsaicin against chemical carcinogen-induced oxidative damage in rats. Male Sprague Dawley rats weighting 230~250 g were treated with chemical carcinogens such as 2-nitropropane (2NP) or n-methyl-N'-nitro-N-nitrosoguanidine (MNNG) after (or before) the administration of capsaicin at doses of 0.5, 1,5 mg/kg. The level of lipid peroxidation in rat liver was estimated by measuring the amounts of thiobarbituric acid reactive substances. The degree of oxidative DNA damage was evacuated by measuring a DNA adduct, 8-hydroxydeoxyguanosine (8-OHdG), in urine. Antioxidative activities of capsaicin and its metabolites in vitro were determined by the measurement of DPPH (1,1-diphenyl-2-picrylhydrazyl), a radical quencher. Significant inhibition of 2-NP induced lipid peroxidation was observed in the liver of the rat when treated with capsaicin. MNNG-induced urinary excretion of 8-OHdG was decreased by capsaicin treatment. Capsaicin and its metabolites inhibited net only the formation of free radicals, but also lipid peroxidation in vitro. Our results show that capsaicin may function as a free radical scavenger against chemical carcinogen-induced oxidative cellular damage in vivo. The observed antioxidative activities of capsaicin may play an important role in the process of chemoprevention.

• Toxicological Research
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• 제28권4호
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• pp.241-248
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• 2012

Exposure of cells to ultraviolet B (UVB) radiation can induce production of free radicals and reactive oxygen species (ROS), which damage cellular components. In addition, these agents can stimulate the expression of matrix metalloproteinase (MMP) and decrease collagen synthesis in human skin cells. In this study, we examined the anti-photoaging effects of extracts of Tetraselmis suecica (W-TS). W-TS showed the strongest scavenging activity against 2,2-difenyl-1-picrylhydrazyl (DPPH) and peroxyl radicals, followed by superoxide anions from the xanthine/xanthine oxidase system. We observed that the levels of both intracellular ROS and lipid peroxidation significantly increased in UVB-irradiated human skin fibroblast cells. Furthermore, the activities of enzymatic antioxidants (e.g., superoxide dismutase) and the levels of non-enzymatic antioxidants (e.g., glutathione) significantly decreased in cells. However, W-TS pretreatment, at the maximum tested concentration, significantly decreased intracellular ROS and malondialdehyde (MDA) levels, and increased superoxide dismutase and glutathione levels in the cells. At this same concentration, W-TS did not show cytotoxicity. Type 1 procollagen and MMP-1 released were quantified using RT-PCR techniques. The results showed that W-TS protected type 1 procollagen against UVB-induced depletion in fibroblast cells in a dose-dependent manner via inhibition of UVB-induced MMP-1. Taken together, the results of the study suggest that W-TS effectively inhibits UVB-induced photoaging in skin fibroblasts by its strong anti-oxidant ability.

• 생명과학회지
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• 제17권2호통권82호
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• pp.230-234
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• 2007

생체는 산소를 소비하는 대사 과정 중에 초산화물(superoxide, $O_{2}$), 과산화수소($H_2O_2$), 수산 라디칼(OH)과 같은 다양한 활성산소(reactive oxygen)들을 생성하게 되며, 그 중에서도 hydrogen peroxide ($H_2O_2$)는 biological membrane을 자유롭게 통과하며, 세포내에서 hydroxyl radical 등의 반응성이 큰 활성 산소종(reactive oxygen species, ROS)을 발생시키는 작용을 하는 강력한 산화제이다. 세포를 계대 배양 (5, 15, 25, 35 passage)하여 $H_2O_2$를 농도별(100 ${\mu}M$, 500 ${\mu}M$, 1 mM, 5 mM)로 처리하고, 또한 $H_2O_2$의 처리 시간(30 분, 1 시간)을 변화시킴으로써, Hepatoma 세포주에서 $H_2O_2$ 처리에 의한 Cu/Zn SOD의 발현을 Northern blot을 통하여 다음과 같이 분석하였다. 1)Hepatoma 세포주에서 시간별, 농도별로 산화제를 처리 했을 때 각각의 경우에서 발현양의 차이는 적었지만, 오랜 시간동안 고농도의 산화제에 노출시켰을 때 항산화 능력이 증가한다는 것을 확인할 수 있었다. 2)계대배양을 증가시키는 것은 노화가 진행된다는 것을 의미하므로, 산화제를 처리했을 때 25 passage에서 35 passage 단계에서 항산화 효소의 발현 정도가 급격히 감소되는 것으로 미루어 보아 이 단계에서 노화가 진행되었음을 추측할 수 있었다. 3)동일한 시간과 농도로 처리했을 때 각각의 passage의 발현 level에서 보이는 양상과는 다르게 35 passage에서는 500${\mu}M$이상의 농도를 1 시간동안 노출시켰을 경우에 Cu/Zn SOD가 거의 발현되지 않았으며, 30 분 동안 노출시켰을 때에는 500 ${\mu}M$의 농도까지 방어할 수 있는 능력을 가진 것으로 보인다.

• 고려인삼학회:학술대회논문집
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• 고려인삼학회 1990년도 Proceedings of International Symposium on Korean Ginseng, 1990, Seoul, Korea
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• pp.49-57
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• 1990

It has been well known that extended exposure to reactive oxygens causes severe damage to susceptible biomolecules. In this study, the effects of flavonoids including trifling and kaempferol from Ginseng leaves on single oxygen induced photohemolysis of erythrocytes and free radical scavenging activities were investigated . Each flavonoid aglycone (5-50UM) such as kaempferol, quercetin or baicalein exhibited a high protective effect against the photohemolysis. They protected the cells by scavenging 102 and free radicals. Although the free radical scavenging activities of the flavonoid glycosides were not much lower than those of their corresponding aglycones, their insolubility into lipid bilayers of membrane made them less effective in preventing the photohemolysis induced by 1O2. The 102 and free radical scavenging activities of flavonoids were estimated by the decomposition of the flavonoid by 1O2 and the bleaching of free radicals by the flavonoid, respectively. The solubilization of the flavonoid into micelle or erythrocytes was deduced from spectrophotometric and microscopic observations. The cooperation of L-ascorbic acid and a flavonoid, and a possible involvement of lipoxygenase or cyclooxygenase in the photohemolysis mechanism were discussed. Keywords Panax ginseng C.A Meyer, ginseng leaves, flavonoids, singe1 oxygen, Photohemolysis.

• 한국식품영양과학회지
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• 제23권5호
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• pp.867-878
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• 1994

A general overview of the lipid peroxidation and its nutritional significance are presented ,with emphasis on the reaction mechaisms, peroxidized products, further interaction and nutritional/biological deterioration in a series of oxidative process. Overall mechanism with various factors and elements for initiation , propagation and termination of free radical reaction is reviewed and the primary /secondary products of peroxidized lipids are defined. Since these products are potentially reactive substances that can cause deterioration of proteins /amino acids and vitamins (carotene, tocopherols and ascorbic acid etc), mechanism and actual damages of their deterioration in some foods and biological models are outlined. Especially , chemical changes caused by interaction of peroxidized products (related hydroperoxides, radicals and malonaldehye etc) and protein are emphasized here. And also, the detailed mechanisms on radical scavenging of the these vitamins which are the most prominent natural antioxidants are presented . Additionally , the possible roles of peroxidicaed lipids and their secondary products in the process of aging an carcinogenesis are briefly discussed . However, it is important to not that more detailed and integrated studies on the reaction kinetics, energetics of peroxidation, their decomposed products , biochemical interaction potential damaging/aging / carcinogenic effects, protection from their oxidative spoilage and novel antioxidants in food and heterogeneous biological systems will be essential in order to assessing the implication of lipid peroxidation to human nutrition and health.

• Journal of Ginseng Research
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• 제14권2호
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• pp.191-199
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• 1990

It has been well known that extended exposure to reactive oxygens causes severe damage to susceptible biomolecules. In this study, the effects of flavonoids including trifolin and kaempferol from Ginseng leaves on singlet oxygen induced photohemolysis of erythrocytes and free radical scavenging activities were investigated. Each flavonoid aglycone (5-50$\mu$M) such as kaempferol, quercetin or baicalein exhibited a high protective effect against the photohemolysis. They protected the cells by scavenging $^1O_2$ and free radicals Although the free radical scavenging activities of the flavonoid glycosides were not much lower than those of their corresponding aglycones, their insolubility into lipid bilayers of membrane made them less effective in preventing the photohemolysis induced by $^1O_2$. The $^1O_2$ and free radical scavenging activities of flavonoids were estimated by the decomposition of the flavonoid by $^1O_2$ and the bleaching of free radicals by the flavonoid, respectively. The solubilization of the flavonoid into micells or erythrocytes was deduced from spectrophotometric and microscopic observations. The cooperation of L-ascorbic acid and a flavonoid, and a possible involvement of lipoxygenase or cyclooxygenase in the photohemolysis mechanism were discussed.

• Nutrition Research and Practice
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• 제5권6호
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• pp.495-502
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• 2011

In this study, antioxidant and free radical scavenging activities of the natural antioxidative compound, pyrogallol-phloroglucinol-6,6'-bieckol (PPB) isolated from brown algae, Ecklonia cava was assessed in vitro by measuring the radical scavenging activities (DPPH, alkyl, hydroxyl, and superoxide) using electron spin resonance (ESR) spectrometry, intracellular reactive oxygen species (ROS) scavenging activity, and DNA damage assay. According to the results of these experiments, the scavenging activity PPB against difference radicals was in the following order: DPPH, alkyl, hydroxyl, and superoxide radicals ($IC_{50}$; 0.90, 2.54, 62.93 and $109.05{\mu}M$). The antioxidant activities of PPB were higher than that of the commercial antioxidant, ascorbic acid. Furthermore, PPB effectively inhibited DNA damage induced by $H_2O_2$. These results suggest that the natural antioxidative compound, PPB, can be used by the natural food industry.

• 한국자기공명학회논문지
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• 제24권2호
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• pp.53-58
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• 2020

Free radicals including reactive oxygen species (ROS) are important chemicals in the research area of biology, pharmaceutical, medical, and environmental science as well as human health risk assessment as they are highly involved in diverse metabolism and toxicity mechanisms through chemical reactions with various components of living bodies. Electron spin resonance (ESR) spectroscopy is a powerful tool for detecting and quantifying those radicals in biological environments. In this work we observed the ESR signal of 2,2,6,6-Tetra-methyl piperidine 1-oxyl (TEMPO) in aqueous solution at various concentrations to estimate the uncertainty factors arising from the experimental conditions and signal treatment methods. As the sample position highly influences the signal intensity, dual ESR tube geometry (consists of a detachable sample tube and a position fixed external tube) was adopted. This type of measurement geometry allowed to get the relative uncertainty of signal intensity lower than 1% when triple measurements are averaged. Linear dependence of signal intensity on the TEMPO concentration, which is required for the quantification of unknown sample, could be obtained over a concentration range of ~10³ by optimizing the signal treatment method depending on the concentration range.

• JSTS:Journal of Semiconductor Technology and Science
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• 제13권4호
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• pp.387-394
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• 2013

As the feature size of integrated circuits continues to decrease, the challenge of achieving an oxidation-free exposed layer after photoresist (PR) stripping is becoming a critical issue for semiconductor device fabrication. In this article, the hydrogen plasma characteristics in direct plasma and the PR stripping rate in remote plasma were studied using a $120{\Phi}$ cylindrical inductively coupled plasma source. E mode, H mode and E-H mode transitions were observed, which were defined by matching the $V_{rms}$ and total impedance. In addition, the dependence of the E-H mode transition on pressure was examined and the corresponding plasma instability regions were identified. The plasma density and electron temperature increased gradually under the same process conditions. In contrast, the PR stripping rate decreased with increasing proportion of $H_2$ gas in mixed $H_2/N_2$ plasma. The decrease in concentration of reactive radicals for the removal of PR with increasing $H_2$ gas flow rate suggests that NH radicals have a dominant effect as the main volatile product.