• 동력기계공학회지
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• 제18권6호
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• pp.133-139
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• 2014

In this research, the photocatalytic degradation of benzothiophene in $TiO_2$ aqueous suspension has been studied. $TiO_2$ photocatalysts are prepared by a sol-gel method. The dominant anatase-structure on $TiO_2$ particles is observed after calcining the $TiO_2$ gel at $500^{\circ}C$ for 1hr. Photocatalysts with various transition metals (Nd, Pd and Pt) loading are tested to evaluate the effect of transition metal impurities on photodegradation. The photocatalytic degradation in most cases follows first-order kinetics. The maximum photodegradation efficiency is obtained with $TiO_2$ dosage of 0.4g/L. The photodegradation efficiency with Pt-$TiO_2$ is higher than pure $TiO_2$ powder. The optimal content value of Pt is 0.5wt.%. Also we investigate the applicability of $H_2O_2$ to increase the efficiency of the $TiO_2$ photocatalytic degradation of benzothiophene. The optimal concentration of $H_2O_2$ is 0.05. The effect of pH is investigated; we obtain the maximum photodegradation efficiency at pH 9. Hydroxy-benzothiophenes and dihydroxy-benzothiophenes are identified as reaction intermediates. It is proposed that benzothiophene is oxidized by OH radical to sequentially form hydroxyl-benzothiophenes, dihydroxybenzothiophenes, and benzothiophenedione.

• 한국식품저장유통학회지
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• 제9권2호
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• pp.253-259
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• 2002

민들레 잎과 뿌리로부터 물추출물을 제조하여 항산화 활성 및 라디칼 소거활성을 분석하기 위하여 linoleic acid에 대한 과산화물 생성저해율, DPPH radical에 대한 소거활성, chemiluminescence를 이용한 hydroxyl radical에 대한 소거활성, EPR을 이용한 superoxide anion radical에 대한 소거활성및 hydrogen peroxide에 대한 소거활성을 측정하였다. 그 결과, 민들레 잎의 물추출물이 뿌리의 물추출물 보다 지방산에 대한 과산화물 생성 저해율이 높았고, DPPH radical, hydroxyl radical, superoxide anion radical 및 hydrogen peroxide에 대한 소거활성 역시 매우 높은 것으로 나타났다.

• 대한화학회지
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• 제16권2호
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• pp.80-83
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• 1972

The activity change of lysozyme resulted from its exposure to $Ti-H_2O_2$system in aqueous liquid at room temperature and to ${\gamma}$-irradiation in ice at $195^{\circ}K$ has been measured at room temperature with a Cary-14 spectrophotometer. The enzymatic activity of lysozyme which had been added to a previously flow-mixed solution of $TiCl_3$ and $H_2O_2$ (System I) was compared with the activity of a lysozyme-$H_2O_2$ solution after flow-mixing with $TiCl_3$ (System II), considering the differences between these two activity changes as the extent of the enzymatic inactivation by the involvement of OH radical reaction. The fraction of lysozyme inactivated by OH radical in the system containing 0.0025 M $TiCl_3-0.1M$ $H_2O_2$ (ph 3.5) was 13%, When the $TiCl_3$ concentration is double (pH 3.0), the fraction of enzyme inactivated increases to 36%. The activity of the system containing 0.025 M $TiCl_3-0.1$ M $H_2O_2$ (pH 1.5) was essentially zero. The results seem to support the previos view that the production of OH radical should be proportional to $TiCl_3$ concentration when $H_2O_2$ is present in excess. Increase in the extent of inactivation found in system I with increasing $TiCl_3$ concentration may be due to a pH effect. $H_2O_2$ seems to be less effective than $TiCl_3$ in the inactivation. 1% lysozyme solution, when ${\gamma}$-irradiated with a total dose of 3M rads, loses about 20% of its activity. Lowering of temperature also was found to yield a reduction in enzymatic activity.

• 한국물환경학회지
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• 제28권3호
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• pp.401-408
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• 2012

High-voltage dielectric discharges are an emerging technique in environmental pollutant degradation, which that are characterized by the production of hydroxyl radicals as the primary degradation species. The initiation and propagation of the electrical discharges depends on several physical, chemical, and electrical parameters such as 1st and 2nd voltage of power, gas supply, conductivity and pH. These parameters also influence the physical and chemical characteristics of the discharges, including the production of reactive species such as OH, $H_2O_2$ and $O_3$. The experimental results showed that the optimum 1st voltage and air flow rate for RNO (N-Dimethyl-4-nitrosoaniline, indicator of the generation of OH radical) degradation were 160 V (2nd voltage of is 15 kV) and 4 L/min, respectively. As the increased of the 2nd voltage (4 kV to 15 kV), RNO degradation, $H_2O_2$ and $O_3$ generation were increased. The conductivity of the solution was not influencing the RNO degradation and $H_2O_2$ and $O_3$ generation. The effects pH was not high on RNO degradation. However, the lower pH and the conductivity, the higher $H_2O_2$ and $O_3$ generation were observed.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2003년도 생물공학의 동향(XII)
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• pp.668-672
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• 2003

An antioxidative activity of Portulaca oleracea was tested by in vitro experimental models. The antioxidative activities were determined by evaluation the DPPH radical scavenging activity and by measuring lipid peroxide using 2-thiobarbituric acid (TBA). The crude extract was sequentially partitioned with n-hexane, 15% aq. MeOH, EtOAc, n-BuOH, $H_2O$. Among them, a remarkable antioxidative effect was observed in the fractions of EtOAc and n-BuOH. The DPPH radical scavenging effect $(IC_{50}=17.90{\mu}g/ml)$ of the n-BuOH soluble fraction was comparable with that of natural antioxidant, ${\alpha}-tocopherol(IC_{50}=\;6.99{\mu}g/ml)$ and the inhibitory effect of lipid peroxidation in mouse liver homogenate was similar to that of natural antioxidant, L-ascorbic acid at a concentration of 0.1mg/ml to 5mg/ml. From the BuOH soluble fraction yielded two biophenolic glycosides, 3-hydroxy-1-(2-hydroxyethyl)phenyl-4-O-${\beta}$-D-glucopyranoside(1) and 2-(3,4-dihydroxyphenyl)ethyl-O-${\beta}$-D-glucopyranoside(2) using column chromatography and revered-phase HPLC. In particular, the DPPH radical scavenging activity of 2 was comparable to that tocopherol$(IC_{50}=6.59{\mu}g/ml)$.

• 한국약용작물학회지
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• 제19권2호
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• pp.77-82
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• 2011

The antioxidative activity of various enzymatic extracts from Sarcodon aspratus (S. aspratus) was evaluated by measuring 1,1-diphenyl-2-picrylhydrazyl (DPPH), and alkyl radical scavenging activity using an electron spin resonance (ESR) spectrometer. For this study, the S. aspratus were enzymatically hydrolyzed by seven carbohydrases (Viscozyme, Celluclast, Dextrozyme, AMG, Promozyme, Maltogenase, and Termamyl) and eight proteases (${\alpha}$-chymotrypsin, Alcalase, Flavourzyme, Neutrase, papain, pepsin, Protamax, and trypsin). The DPPH radical scavenging activities of Viscozyme and pepsin extracts were the highest, and the half maximal inhibitory concentration ($IC_{50}$) values were 0.896 and 0.734mg/mL, respectively. The Celluclast and trypsin extracts showed the highest scavenging activities on alkyl radical, and their $IC_{50}$ values were 0.278 and 0.575mg/mL, respectively. The Celluclast extracts was decreased cell apoptosis in PC-12 cells against $H_2O_2$-induced oxidative damage. The findings of the present study suggest that enzymatic extracts of S. aspratus exhibit antioxidative activity against oxidative stress on PC-12 cells.

• Preventive Nutrition and Food Science
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• 제14권1호
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• pp.86-89
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• 2009

In this study, we investigated the free radical [1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl radical (${\cdot}OH$) and superoxide anion (${O_2}^-$)] scavenging activity of MeOH extract and 3 fractions of Citrus junos. Of the tested fractions, the BuOH fraction showed the strongest DPPH scavenging activity, showing the $IC_{50}$ values of 63.4 mg/mL. Therefore, we continuously carried out DPPH, ${\cdot}OH$ and ${O_2}^-$ scavenging activity tests of BuOH fraction of Citrus junos. The BuOH fraction of Citrus junos inhibited DPPH radical to 97.5% at a concentration of 1000 mg/mL and the scavenging activities were increased concentration-dependently. In addition, BuOH fraction from Citrus junos also scavenged ${\cdot}OH$ in a concentration dependent manner from 5 to 1000 mg/mL. Furthermore, BuOH fraction showed about 56% ${O_2}^-$-scavengimg activity at 25 mg/mL concentration but, the scavenging activities were not enhanced in a dose dependent manner. The present results suggest that BuOH fraction of Citrus junos would have the protective potential from oxidative stress induced by free radicals.

• 대한화학회지
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• 제24권3호
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• pp.250-258
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• 1980

여러종류의 자유라디칼들이 이소니트릴에 첨가되어 중간체인 imidoyl 자유라디칼 RN=CR'을 형성한다. 이것은 또한 imine으로부터 imidoyl hydrogen 을 떼어 내는 다음과 같은 반응에 의해서도 생성될 수 있다. RN=C(H)R' ＋ R"${\cdot}{\rightarrow}$ RN=CR' ＋ R"-H 중간체인 imidoyl 자유라디칼은 ${\beta}$-cleavage 및 aton transfer 반응을 통해서 안정된 분자를 형성한다. ${\beta}$-cleavage는 imidoyl 자유라디칼의 구조에 따라서 두개의 다른 방향으로의 반응이 가능하다. Cyanide transfer와 소위 말하는 정상적인 ${\beta}$-cleavage가 그러한 반응들이다. t-Butoxy 자유라디칼이 t-butylisonitrile 7에 첨가되면 중간체인 t-Bu-N=C-O-Bu-t가 생성되는데, 이것은 ${\beta}$-cleavage반응을 통해서 t-butylisocyanate와 t-butyl 자유라디칼을 형성한다. Phenyl 자유라디칼은 7에 첨가되어 중간체인 t-Bu-N=$C-C_6H_5$를 형성하는데 이것은 cyanide transfer 반응을 통해서 benzonitrile과 t-butyl 자유라디칼로 분해된다. 여기서 생성되는 t-butyl 자유라디칼은 다시 7에 첨가하여 intermediate인 자유라디칼 t-Bu-N=C-Bu-t을 형성하고, 이것은 다시 pivalonlonitrile과 t-butyl 자유라디칼로 분해되는데 이러한 반응이 반복되므로 radical chain isomerization을 일으킨다. Silyl 자유라디칼은 7에 첨가되어 t-Bu-N=$C-Si(CH_3)_3$를 형성하고, 이것은 cyanide transfer 반응을 거쳐서 다시 $(CH_3)_3$SiCN과 t-butyl 자유라디칼로 분해된다.

• Bulletin of the Korean Chemical Society
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• 제20권6호
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• pp.734-736
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• 1999

• BMB Reports
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• 제44권3호
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• pp.165-169
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• 2011

Excess free iron generates oxidative stress that may contribute to the pathogenesis of various causes of neurodegenerative diseases. In this study, we assessed the modification of ferritin induced by $H_2O_2$. When ferritin was incubated with $H_2O_2$, the degradation of ferritin L-chain increased with the $H_2O_2$ concentration whereas ferritin H-chain was remained. Free radical scavengers, azide, thiourea, and N-acetyl-$_L$-cysteine suppressed the $H_2O_2$-mediated ferritin modification. The iron specific chelator, deferoxamine, effectively prevented $H_2O_2$-mediated ferritin degradation in modified ferritin. The release of iron ions from ferritin was increased in $H_2O_2$ concentration-dependent manner. The present results suggest that free radicals may play a role in the modification and iron releasing of ferritin by $H_2O_2$. It is assumed that oxidative damage of ferritin by $H_2O_2$ may induce the increase of iron content in cells and subsequently lead to the deleterious condition.