• Bulletin of the Korean Chemical Society
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• 제33권4호
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• pp.1290-1296
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• 2012

Fenton reaction and iron autoxidation have been debated for the major process in ROS mediated DNA cleavage. We compared both processes on iron oxidation, DNA cleavage, and cyclic voltammetric experiment at different pHs. Both oxidation reactions were preferred at basic pH condition, unlike DNA cleavage. This indicates that iron oxidation and the following steps probably occur separately. The ROS generated from autoxidation seems to be superoxide radical since sod exerted the best inhibition on DNA cleavage when $H_2O_2$ was absent. In comparison of cyclic voltammograms of $Fe^{2+}$ in NaCl solution and phosphate buffer, DNA addition to phosphate buffer induced significant change in the redox cycle of iron, indicating that iron may bind DNA as a complex with phosphate. Different pulse voltammogram in the presence of ctDNA suggest that iron ions are recyclable at acidic pH, whereas they may form an electrically stable complex with DNA at high pH condition.

• Corrosion Science and Technology
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• 제21권5호
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• pp.412-417
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• 2022

Proton exchange membrane fuel cells (PEMFCs) provide zero emission power sources for electric vehicles and portable electronic devices. Although significant progresses for the widespread application of electrochemical energy technology have been achieved, some drawbacks such as catalytic activity, durability, and high cost of catalysts still remain. Pt-based catalysts are regarded as the most efficient catalysts for sluggish kinetics of oxygen reduction reaction (ORR). However, their prohibitive cost limits the commercialization of PEMFCs. Therefore, we proposed a NiCo@Au core shell structure as Pt-free ORR electrocatalyst in PEMFCs. NiCo alloy was synthesized as core to introduce ionization tendency and autoxidation reaction. Au as a shell was synthesized to prevent oxidation of core NiCo and increase catalytic activity for ORR. Herein, we report the synthesis, characterization, electrochemical properties, and PEMFCs performance of the novel NiCo@Au core-shell as a catalyst for ORR in PEMFCs application. Based on results of this study, possible mechanism for catalytic of autoxidation core@anti-oxidation shell in PEMFCs is suggested.

• 한국자동차공학회논문집
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• 제15권6호
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• pp.81-86
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• 2007

Biodiesel fuel that consists of saturated and unsaturated long-chain fatty acid alkyl esters is an alternative diesel fuel produced from vegetable oils or animal fats. However, air causes autoxidation of biodiesel fuel during storage, which can reduce fuel quality by adversely affecting its properties, such as the kinematic viscosity and acid value. One approach for improving the resistance of fatty derivatives to autoxidation is to mix them with antioxidants. This study investigated the effectiveness of five such antioxidants in mixtures with biodiesel fuels produced by three biodiesel manufacturers : tert-butylhydroquinone (TBHQ), butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), propyl gallate (PrG) and $\alpha$-tocopherol. Oxidation stability was determined using Rancimat equipment. The results show that TBHQ, BHA, and BHT were the most effective and $\alpha$-tocopherol was the least effective at increasing the oxidation stability of biodiesel. This study recommends that TBHQ and PrG be used for safeguarding biodiesel fuel from the effects of autoxidation during storage.

• 한국응용과학기술학회지
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• 제3권1호
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• pp.39-42
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• 1986

The antioxidant activity of petroleum ether extract of Panax ginseng roots in the oxidation of mixed methyl esters of unsaturated fatty acids(MEUFA) was investigated in vitro. The petroleum ether extract of panax ginseng roots showed the antioxidant activity and inhibited the weight gain in the autoxidation of MEUFA. And the induction periods in the autoxidation of MEUFA were related to te addition concentrations of petroleum ether extact. The antioxidant effect of petroleum ether extract on the autoxidation of MEUFA was caused by the protective formation of lipid peroxides and carbonyl compounds. From the results obtained, it was confirmed that petroleum ether extract of panax ginseng roots contained antioxidant substances.

• 한국식품과학회지
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• 제32권6호
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• pp.1437-1441
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• 2000

Acycloretinal을 Tollens 시약으로 처리하여 acycloretinoic acid를 얻었다. 생성된 표준품 acycloretinoic acid는 Silica-HPLC 및 ODS-HPLC를 통하여 정제를 행하고 GC-MS에 의해 동정하였다. Lycopene을 toluene과 Tween 40 수용액에서 $37^{\circ}C$ 조건으로 자동산화시킨 결과, acidic 화합물이 생성되었다. Lycopene의 자동산화로부터 생성된 acidic 화합물은 그 HPLC상의 거동, 분광학적 특성 및 mass spectra의 특성이 acycloretinoic acid 표준품과 잘 일치하였다. 이러한 결과로 in vitro상의 산화적 조건하에서 lycopene의 자동산화에 의해 acycloretinoic acid가 생성됨을 알 수 있었다.

• 한국식품영양과학회지
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• 제19권3호
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• pp.239-247
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• 1990

The oxidation products from the mixture of a-tocopherol (a-Toc) and γ-tocopherol)(γ-Toc) during autoxidation of methyl linoleate were isolated and identified. The sturctures of the oxida-tion products were characterized by UV, IR, 1H and 13CNMR and mass spectrometry 5-[2-(a-tocopherol-5'-yl)ethyl]-a-tocopherylquinone 5-[2-(a-tocopherol-5'-yl)ethyl]-8a-hydroxy-a-tocopherone and O-[8-(5-ethoxymethyl-7-methyltocol) methyl] a-tocopherol were obained from the mixture as the oxidation products derived from γ-Toc However oxidation product composed of both a-ToC and γ-Toc was detected in oxidation products of the misture. These results support the facts that at first oxidation of a-Toc proceeds during autoxidation of lipids and then γ-Toc decomposes after approximate consumption of a-Toc.

• 한국식품과학회지
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• 제29권2호
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• pp.379-382
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• 1997

본 연구에서는 볶지않은 들깨와 볶은 들깨에서 착유한 들기름에 몇가지 산화방지제를 첨가하여 들기름의 산화안정성을 검토하였다. $190^{\circ}C$에서 20분동안 볶은 들깨와 볶지 않은 들깨에서 착유한 들기름에 ${\alpha}$-토코페롤, ${\delta}$-토코페롤을 100, 200, 300과 400 ppm, BHA, BHT와 TBHQ를 50, 100, 150과 200 ppm으로 농도별로 첨가하여 $50^{\circ}C$에서 저장하면서 과산화물가를 측정하였다. 측정한 과산화물가는 antioxidative index (항산화제를 첨가한 들기름의 유도기간/항산화제를 첨가안한 들기름의 유도기간)로 환산하여 산화적 안정성을 비교하였다. 볶지 않고 착유한 들기름보다 볶은 들깨에서 착유한 들기름의 산화안정성이 뛰어나, 볶음공정이 들기름의 산화안정성에 약 4배 정도 기여하는 것으로 나타났다. 첨가된 토코페롤류는 들기름의 산화를 촉진하였다. 합성산화방지제인 BHA는 산화방지 효과가 없었고, BHT는 미약한 산화방지 효과를 보였다. 그러나 TBHQ는 강한 산화방지 효과를 보였다. 이 결과로 미루어 볼때 TBHQ를 법적 허용 기준치인 200 ppm이내에서 첨가하였을때 들기름의 저장안정성을 약 5배 이상 향상시킬 수 있을 것으로 예상되며, TBHQ가 들기름의 산화 안정성 향상에 가장 적합한 산화방지제로 판단되었다. 또한 볶음조건을 조절함으로써 들기름의 산화안정성에도 기여할 것으로 판단되었다.

• 한국축산식품학회지
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• 제23권4호
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• pp.309-314
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• 2003

Color and its stability in venison, longissumus dorsi (LD) and quadriceps femoris (QF) muscles, from 8 wild Cervus nippon yesoensis (Japanese Yeso Deer) were investigated by means of the CIE L$^{*}a{*}b{*}$ measurement and autoxidation rate recorded using partially purified myoglobin. It was observed a common feature of the change of three mean values($L^{*}$, $a^{*}$ and $b^{*}$) in both LD and QF that mean value increased at 1 or 2 day post-mortem and then decreased during storage. The differences between 1 and 7 days was the largest in $a^{*}$ value than those in $L^{*}$ and $b^{*}$ values. The mean differences among storage days were only significant in $a^{*}$ except for $b^{*}$ of LD. It was same tendency that the mean difference of CIE $L^{*}$, $a^{*}$ and $b^{*}$ values during refrigerator storage was larger in $a^{*}$ than both in $L^{*}$ and $b^{*}$ reported in beef(Sekikawa et al., 1995) and venison(Stevenson et al., 1989) during storage. The smaller $a^{*}$ value was indicated that bright red of meat changed to dull red, brown red causing met-Mb formation. To compare of color stability with respects to the Mb autoxidation rate, we measured this rate of deer and horse muscles, because horse Mb was considered to have the fastest autoxidation rate among domestic animals, and we used crude Mb and pH 6.0, which might be reflected to the intact meat. Mean value of the autoxidation rate measured in this study in deer was 0.037 and that was 0.026 in horse(sigma). Although there was no significant mean difference and were different Mb purity between deer(A409/A 280 nm = 4.0) and horse(5.6), in generally Mb purity was the higher and the faster autoxidation rate, but this rate in deer was faster than in horse. These results might indicate that venison meat discolors at faster rate compared with beef.

• 한국식품과학회지
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• 제14권2호
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• pp.130-135
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• 1982

인삼중에 함유되어 있는 항산화물질의 본태를 파악하기 위하여 인삼의 각종 용매(petroleum ether, chleroform, chleroform-methanol, methanol 및 methanol-water)추출물들이 혼합 불포화지방산 메틸에스테르(MEUFA)의 자동산화에 미치는 영향을 in vitro에서 검토한 결과는 다음과 같다. 1. 인삼의 각종 용매 추출물들은 모두 항산화작용을 나타내어 MEUFA의 자동산화에 의한 지질 과산화물의 형성을 억제하였다. 그 중에서도 클로로포름 및 클로로포름-메탄올(2 : 1, v/v)추출물들이 보다 강한 항산화작용을 나타내었다. 2. Olcotte 등의 oven test에 의한 무게의 증가는 MEUFA의 자동산화에 의한 과산화물의 형성에 기인함이 확인되었다. 3. 인삼의 각 추출물들은 MEUFA의 지질 과산화물형성의 유도기간을 연장시켰다. 4. 각 추출물들의 항산화작용에 있어서 Olcott 등의 oven test에 의한 무게의 측정 Lea법과 Rhodan 철법에 의한 POV 측정 등의 결과에서 추정되는 작용은 상호간 잘 일치되었다. 이상의 결과로부터 인삼중에는 항산화물질들이 인삼성분으로서 함유되어 있음이 in vitro에서 확인되었다.

• 한국식품영양과학회지
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• 제22권1호
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• pp.96-100
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• 1993

잣 지방질을 정제 단계를 달리하여 자동산화 시키면서 토코페롤 및 카로티노이드의 변화를 살펴 보았다. 정제 단계를 거칠수록 산화 안정성이 감소되었으며 총 토코페롤의 함량은 조지방의 경우 55.51mg/100g oil이었으며 이 중 $\alpha$-토코페를 25.48mg, ${\gamma}$-토코페를 23.94mg, $\beta$-토코페를 6.99mg순으로 함유되어 있었으며 $\delta$-토코페롤은 흔적량 존재하였다. 탈검된 지방질 및 탄산된 지방질에서도 $\alpha$-토코페를이 23.85mg, 24.08mg, ${\gamma}$-토코페롤이 19.79mg, 20.04mg, 그리고 $\beta$-토코페롤은 6.12mg, 5.33mg함유되어 있었다. 카로티노이드 중 $\beta$-카로틴은 비 비누화물질 중의 0.63%이었으며 리코펜은 미량 함유되어 있었다. 지방질의 자동산화가 진행되는 동안 카로티노이드와 토코페롤은 감소되었으며, 특히 자동산화의 초기과정에서 항산화제로 작용하여 상당량이 감소된 것으로 여겨졌으며 그 감소속도는 $\alpha$-토코페롤, ${\gamma}$-토코페롤 순이었다.