• Macromolecular Research
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• 제17권8호
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• pp.557-562
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• 2009

The free radical polymerization of styrene was initiated with azobis(isobutyronitrile) in the presence of benzene sulfonyl chloride. Analysis of the terminal structures of the obtained polystyrene with $^1H$ NMR spectroscopy revealed the presence of a phenyl sulfonyl group at the ${\alpha}$-end and a chlorine atom at the ${\omega}$-end of each polystyrene chain. The terminal chlorine atom in the polystyrene chains was further confirmed through atom transfer radical polymerization (ATRP) of styrene and methyl acrylate using the obtained polystyrenes as macroinitiators and CuCl/2,2'-bipyridine as the catalyst system. GPC traces of the products obtained in ATRP at different reaction times were clearly shifted to higher molecular weight direction, indicating that nearly all the macroinitiator chains initiated ATRP of the second monomers. In addition, the number-average molecular weights of the polystyrenes increased directly proportional to the monomer conversions, and agreed well with the theoretical ones.

• 대한화학회지
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• 제29권4호
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• pp.426-436
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• 1985

몇가지 벤즈아닐리드류를 합성하여 광반응시킨 후 생성물을 분리하고 그 구조를 결정하였다. 벤즈아닐리드 자체는 광고리화 안되고 Photo-Fries형 생성물을 주었지만 2-chlorobenzaniline, 2-bromobenzanilide, 및 2-methoxybenzanilide는 질소기류하에서 광고리화하여 모두 phenanthridone을 생성하였다. 2-chloro-2-nitrobenzanilide는 광고리화되지 않았다. 니트로기가 페닐고리에 도입되니 들뜬상태의 에너지가 낮아서 광고리화 안되었다. 2,2'-dichlorobenzanilide가 광고리화 되어 8-chlorophenanthridone이 되는 것으로 보아 들뜬 부분은 카르보닐쪽의 페닐 부분인것을 알 수 있었다. 2'-위치에 Cl이 있는 경우에도 광고리화 되었다. 2-chlorobenzanilide나 2'-chlorobenzanilide에 대하여 몇가지 용매중에서 광고리화 양자수득률을 구하였는데, 2-chlorobenzaniline는 효과적으로, 2'-chlorobenzanilide는 비효과적으로 광고리화 되었다. 대체로 비극성용매중에서 또 저점성용매중에서 양자수득률이 좋았다. 2-chlorobenzaniline가 광고리화 될때 산소의 영향을 시험하였는데, 산소가 존재하는 데서 광고리화가 잘 안되었다. 따라서 이때 삼중상태가 상관하는 것을 알았으며 전이상태는 염소원자가 떨어져 나가고 이때 이웃 페닐고리가 도우는 메카니즘을 제안한다. 삼중상태의 2-chlorobenzaniline에서 카르보닐쪽의 페닐과 N-페닐의 도움으로 카르보닐쪽의 페닐에 붙은 염소원자 떨어져나가 중간체인 컨쥬게이션된 라디칼이 된다. 이 라디칼에서 수소원자가 떨어져 나가 phenanthridone이 되는데, 이 단계는 속도결정단계가 아니다. 왜냐하면, 이 광고리화 반응에서 수소대신 중수소를 치환해도 속도에는 영향이 없기 때문이다. 2-methoxybenzanilide가 광고리화 될때는 산소가 존재하니 반응이 빨라졌다. 이는 단일 상태가 상관하는 것 같으며 산소가 중간체를 산화하여 반응을 촉진하는 것 같다.

• Natural Product Sciences
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• 제6권3호
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• pp.135-138
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• 2000

MeOH extract of Cuscuta chinensis seeds was fractionated with n-hexane, EtOAc and BuOH successively, and antioxidant activities were tested for all fractions using DPPH free radical scavenging method. In the tested fractions, EtOAc fraction showed high antioxidant activity$(EC_{50},\;50\;{\mu}g)$ From the EtOAc fraction, five compounds have been isolated. On the basis of spectral data, these compounds were identified as ${\beta}-sitosterol$, methyl 4-hydroxy-3,5-dimethoxycinnamate, ${\beta}-sitosterol-3-O-{\beta}-D-glucopyranoside$, caffeic acid, quercetin, kaempferol and calycopteretin. Among these compounds, ${\beta}-sitosterol$ and ${\beta}-sitosterol-3-O-{\beta}-D-glucopyranoside$ showed no antioxidant activity. $EC_{50}$ values of methyl 4-hydroxy-3,5-dimethoxycinnamate, caffeic acid, quercetin, kaempferol and calycopteretin were 0.6, 8, 19, 17 and $12\;{\mu}g$, respectively.

• 대한화학회지
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• 제18권5호
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• pp.341-353
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• 1974

Triphenylphosphine phenylimide의 비수용액에서의 전기화학적인 환원반응을 polarography, cyclic voltammetry, controlled-potential coulometry 및 electron spin resonance 법을 써서 고찰하였다. 이 유기인화합물은 one-electon transfer에 따라서 anion radical이 형성되나 순간일 뿐이고 protonation과 재차 one-electon reduction 결과 인과 질소사이의 이중결합이 끊어진다. 그 결과 아닐린이 주요 반응생성물로서 발견되었다. 또 한편 동반하는 화학반응결과 생긴 주산물의 하나인 triphenylposphine oxide의 환원결과 인과 페닐 사이의 단일결합이 끊어지는 것도 관찰할 수 있었다.

• Archives of Pharmacal Research
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• 제28권5호
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• pp.518-528
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• 2005

In the present study, the antioxidative and inhibitory activity of Zingiber officinale Rosc. Rhizomes-derived materials (on mushroom tyrosinase) were evaluated. The bioactive co mponents of Z. officinale rhizomes were characterized by spectroscopic analysis as zingerone and dehydrozingerone, which exhibited potent antioxidant and tyrosinase inhibition activities. A series of substituted dehydrozingerones [(E)-4-phenyl-3-buten-2-ones] were prepared in admirable yields by the reaction of appropriate benzaldehydes with acetone and the products were evaluated in terms of variation in the dehydrozingerone structure. The synthetic analogues were examined for their antioxidant and antityrosinase activities to probe the most potent analogue. Compound 26 inhibited Fe$^{2+}$-induced lipid peroxidation in rat brain homogenate with an IC$_{50}$ = 6.3${\pm}$0.4 ${\mu}$M. In the 1,1-diphenyl- 2-picrylhydrazyl (DPPH) radical quencher assay, compounds 2, 7, 17, 26, 28, and 29 showed radical scavenging activity equal to or higher than those of the standard antioxidants, like ${\alpha}$-tocopherol and ascorbic acid. Compound 27 displayed superior inhibition of tyrosinase activity relative to other examined analogues. Compounds 2, 17, and 26 exhibited non-competitive inhibition against oxidation of 3,4- dihydroxyphenylalanine (L-DOPA). From the present study, it was observed that both number and position of hydroxyl groups on aromatic ring and a double bond between C-3 and C-4 played a critical role in exerting the antioxidant and antityrosinase activity.

• 대한화학회지
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• 제25권6호
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• pp.383-389
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• 1981

티안트렌 양이온 자유라디칼 과염소산염은 p-톨루엔술포아니리드, 벤젠술폰아니리드, N-(2-메틸페닐)벤젠술폰아미드, N-페닐-p-톨루엔술폰아닐리드와 같은 N-아릴술폰아미드와 반응하여 각각 5-(p-N-p-톨루엔술폰아미도페닐)티안트렌이움 과염소산염(1a), 5-(p-N-벤젠술폰아미도페닐)티안트렌이움 과연소산염(1b), 5-(4-N-벤젠술폰아미도-3-메틸페닐)티안트렌이움 과염소산염(1c), 5-(p-N-페닐-N-p-톨루엔술폰아미도페닐)티안트렌이움 과염소산염(1d)을 준다. 한편 1d는 티안트렌 양이온 자유라디칼과 다시 반응하여 이과염소산염(1e)을 생성한다. 1a∼1e의 구조는 아세트아니리드와의 반응생성물인 5-(p-아세트아미도페닐)티안트렌이움 과염소산염과 매우 비슷하다. 그러나 두 반응의 양 관계에서 상이한 점은 술폰아미드와의 반응이 단일 메카니즘으로 진행되지 않음을 암시한다.

• 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$(IC_{50}=6.59{\mu}g/ml)$.

• 약학회지
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• 제47권4호
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• pp.224-229
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• 2003

We have investigated the transport characteristics of synthetic antioxidant and free radical scavenger, $\alpha$-phenyl-n-tert-butyl nitrone (PBN) at the blood-brain barrier (BBB) by in vitro uptake study in conditionally immortalized rat brain capillary endothelial cell line (TR-BBB). Also, the efflux of PBN from brain to blood is estimated using the brain efflux index (BEI) method. Choline is a charged organic cation, including nitrogen-methyl group and shows the carrier-mediated distribution to the brain. [$^3$H]Choline uptake by TR-BBB cells was significantly inhibited by PBN with $IC_{50}$/ of 1.2 mM, which appears to be due to similar structures between choline and PBN. And, PBN was microinjected into Par2 of the rat brain by BEI method, and was eliminated from the brain with an apparent elimination half-life of about 2 min. Also, [$^3$H]choline efflux was significantly inhibited by PBN using BEI method. In conclusion, the efflux transport of PBN takes place across the BBB and PBN may be transported into the brain and eliminated from the brain by BBB choline transporter.

• Food Science and Biotechnology
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• 제17권6호
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• pp.1376-1378
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• 2008

Tachioside (4-hydroxy-3-methoxy-phenyl-1-O-glucoside), a known phenolic glycoside, was isolated from various bamboo species. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity and Trolox equivalent antioxidant capacity determined a significant antioxidant activity of tachioside which was comparable to L-ascorbic acid. Each culm and leaf extracts were tested and the culm of Phyllostachys bambusoides appeared to contain the highest amount of tachioside.

• 대한화학회지
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• 제43권1호
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• pp.74-84
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• 1999

벤조트리아졸을 보조체로 사용하는 유기합성법은 거의 대부분 이온성 반응 메카니즘으로 설명되며 라디칼 반응을 이용한 벤조트리아졸의 응용은 거의 없었다. 벤조트리아졸의 N-1의 ${\alpha}$위치 탄소 원자에 라디칼 중심을 만든 후 벤조트리아졸의 다섯고리를 형성하는 질소 원자중에서 질소 분자가 빠져나감으로서 생성되는 페닐 라디칼의 반응을 연구하기위해 1[(aryl)(phenylseleno)methyl]benzotriazole, AIBN, 그리고 $Bu_3$SnH을 벤젠에 용해시키고 환류시켜 주었다. 이 반응 혼합물로 부터 2-aminodiphenyl selenide (16∼29%), 2-aminobiphenyl (9∼15%), diphenyl diselenide (30∼93%), 1-(arylmethyl)benzotriazole (9∼39%), 그리고 tributyltinphenyl selenide (10∼36%)을 얻었으며, AIBN없이 과량의 $Bu_3$SnH 존재하에 같은 조건하에서 반응시키는 경우,diphenyl diselenide (53∼100%), benzotriazole (27∼35%) 그리고 1-(arylmethyl)-benzotriazole (16∼33%)와 함께 arylmethylidenaniline이 과량의 $Bu_3S_nH$에 의해 환원된 N-(arylmethyl)anilines (44∼66%)이 생성되었다. 같은 조건 하에서 6-aryl-6-(benzotriazol-1-yl)-1-hexenyl phenyl selenides, AIBN, 그리고 $Bu_3$SnH의 반응으로부터 6-aryl-6-phenylamino-1-hexene(9∼31%)과 1-aryl-1-oxo-5-pentene (15∼44%)을 얻었다. 이들 생성물의 생성 메카니즘을 제시하였으며 벤조트리아졸이 합성 보조체로 이용된 경우 $Bu_3$SnH에 의해 벤조트리아졸의 세개의 질소 원자를 포함하는 다섯원자고리로 부터 라디칼 반응에 의해 질소 분자가 빠져나가는 것을 보여준 새로운 예이다.