• Macromolecular Research
• /
• 제13권3호
• /
• pp.229-235
• /
• 2005

Various alkoxyamine initiators for nitroxide mediated radical polymerization (NMRP) were prepared in high yields by a simple substitution reaction of nitroxide anions with benzyl bromide. The required nitroxide anions were easily generated by treating either nitroxide free radicals or hydroxy amine with an alkali metal such as sodium or potassium in THF. This method is both practical and efficient, since the ionic conditions prevent other side reactions from occurring, such as the self-coupling or oligomerization reactions that are observed in the case of radical trapping conditions. To demonstrate the utility of the resulting alkoxyamine initiators, end- and telechelic-alkoxyamine PEG macroinitiators derived from the alkoxyamines were synthesized by a simple chemical modification, and used for the preparation of PEG-b-PS and PS-b-PEG-b-PS block copolymers by NMRP.

• Archives of Pharmacal Research
• /
• 제28권5호
• /
• pp.534-540
• /
• 2005

Activity-guided fractionation of the CH$_2Cl_2$-soluble fraction of the roots of Sophora flavescens furnished five 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scaveng ers: trans-hexadecyl ferulic acid (1) cis-octadecyl ferulic acid (2), trans-hexadecyl sinapic acid (3), (-)-4-hydroxy-3-methoxy-(6aR,11aR)-8, 9-methylenedioxypterocarpan (4) and desmethylanhydroicaritin (8), along with nine known inactive compounds: (-)-maackiain (5), xanthohumol (6), formononetin (7), (2S)-2'-methoxykurarinone (9), (2S)-3${\beta}$,7,4'-trihydroxy-5-methoxy-8-(${\gamma},{\gamma}$- imethylallyl )-flavanone (10), (2S)-7,4'-dihydroxy-5-methoxy-8- (${\gamma},{\gamma}$-dimethylallyl ) -flavanone (11), umbelliferone (12), kuraridin (13), and trifolirhizin (14). Compounds 1-4 and 8 exhibited DPPH free radical scavenging effects at IC$_{50}$ values of 33.01 ${\pm}$ 0.20, 57.06 ${\pm}$ 0.16, 39.84 ${\pm}$ 0.36, 35.83 ${\pm}$ 0.47, and 18.11 ${\pm}$ 0.04${\mu}$M, respectively. L-Ascorbic acid, when used as a positive control, exhibited an IC$_{50}$ value of 7.39 ${\pm}$ 0.01 ${\mu}$M. Compounds 1-4 and 8 also appeared to exert significant scavenging effects on authentic ONOO-, with IC$_{50}$ values of 5.76 ${\pm}$ 1.19, 15.06 ${\pm}$ 1.64, 8.17 ${\pm}$ 4.97, 1.95 ${\pm}$ 0.29 and 4.06 ${\pm}$ 2.41 ${\mu}$M, respectively. Penicillamine (IC$_{50}$= 2.36 ${\pm}$ 0.79${\mu}$M) was used as a positive control. In addition, compounds 2,4,6,8, and 10 were isolated from this plant for the first time.

• 한국식품과학회지
• /
• 제34권6호
• /
• pp.1115-1122
• /
• 2002

시판되고 있는 두류 22 종류의 70% 에탄올 추출물을 제조하여, 이들의 항산화 활성, 화학적 변이원 mitomycin C에 대한 항변이원성, 세포독성, 변이원성 등을 포함하는 생리활성 효과를 비교 검정하였다. DPPH radical에 대한 전자공여능, hydroxy radical 소거능 및 지질 자동산화 억제효과 등은 모든 두류 품종이 거의 유사한 효과를 나타내었다. 예팔, 완두, 녹두, 백편두 등은 변이원 mitomycin C에 대해 유의할만한 수준의 항변이원성을 보였으며, 녹색나물콩, 녹두, 속피리 등은 지시 세포의 성장을 촉진하는 효과가 있었고, 속청과 청태는 변이원성을 억제하는 특성이 있었다. 백편두는 세포 성장과 돌연변이 유발 모두를 억제하는 것으로 나타나 추출물 자체가 독성을 가질 수도 있을 것으로 생각되었다. 결과적으로 본 연구의 목적이었던 기능성 밥 및 떡 제조를 위한 부재료로서의 두류 이용을 위해서는 예팥, 녹두 등을 이용하는 것이 바람직하리라고 생각된다.

• Food Science and Biotechnology
• /
• 제16권3호
• /
• pp.349-354
• /
• 2007

The objectives of this study were to systemically identify phenolic compounds in roasted wild ginseng (Panax ginseng C.A. Meyer) leaves and investigate their radical scavenging activities. Seven phenolic compounds were identified by NMR (H, C, COSY, HMQC, HMBC) and mass (EI-MS, FAB-MS) analyses: 5-caffeoylquinic acid, kaempferol, quercetin, 3,4-dihydroxy-benzoic acid, 4-hydroxy-benzoic acid, 3-(3,4-dihydroxyphenyl)-2-propenoic acid, and 3-(4-hydroxy-3-methoxyphenyl)-2-propenoic acid. Their concentrations ranged from 0.4 (3,4-dihydroxy-benzoic acid) to 7.5 mg (kaempferol) per 100 g of roasted leaves. Among these compounds, 5-caffeoylquinic acid, kaempferol, and quercetin were found exclusively in the leaf portions of the ginseng plants. When their antioxidant activities were measured by DPPH and superoxide anion radical scavenging activity, quercetin, and kaempferol were most effective.

• 한국식생활문화학회지
• /
• 제28권3호
• /
• pp.320-327
• /
• 2013

The quality characteristics of Omija (Schizandra chinesis Baillon) extracts under various extraction temperatures and times were examined. The pH level of the extracts ranged from 3.35-3.47. The sugar and solid content of the samples significantly increased with increasing extraction temperatures and times (p<0.01). In contrast, the lightness of the extracts decreased with increasing extraction temperatures and times (p<0.001). In a palatability test, extracts boiled at $80^{\circ}C$ for 30 minutes scored high in terms of color, flavor, turbidity, sourness, and overall acceptability. Hydroxy radical scavenging activity and polyphenol content of the extracts significantly increased with increasing extraction temperatures and times (p<0.01). Furthermore, direct correlations between hydroxy radical scavenging activity and polyphenol content (or flavonoid content) were established through simple regression (r>0.9) for different extraction temperatures and times. From these results, extracts boiled at $80^{\circ}C$ for 120 minutes is the best to product omija beverage considering functionality and sensory evaluation as well.

• Journal of Life Science
• /
• 제12권2호
• /
• pp.75-79
• /
• 2002

Tea catechins, the most important compounds in tea polyphenols, can efficiently scavenge superoxide anion free-radical ($O_2$.), hydroxyl radical. (.OH) The mechanism of scavenging active oxygen free radicals was investigated by ESR spin trapping technique and Chemiluminescence. Results showed that various tea catechins constitute an antioxidant cycle in accordance with the decreasing order of the first reductive potential, and produce the effect of cooperative strength each other. Esterificated catechins could scavenge active oxygen free radicals more effectively than the non-esterificated ones. When.OH and $O_2$.- were scavenged by (-)-epigallocatechin gallate [(-)- EGCG], the stoichiometric factors were 6, and the rate constants of scavenging reaction reached $7.71{\times}10^6$ and $3.52{\times}10^{11}$ L $mmol^{-1}s^{-1}$, respectively. In the mean time, tea catechins could scavenge superoxide anion fiee radical ($O_2$-.) and hydroxyl radical (.OH) in a dose dependent manner. But at higher concentration or pH value, tea catechins can induce the prooxidant.

• Archives of Pharmacal Research
• /
• 제26권1호
• /
• pp.24-27
• /
• 2003

A furanofuranoid lignan glycoside, with radical scavenging on peroxynitrite, total reactive oxygen species (ROS) and 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical, was isolated from the rhizome of Salvia miltiorrhiza and characterized as (+)-1-hydroxypinoresinol-1-Ο-$\beta$-D-glucoside based on spectroscopic evidence. The compound exhibited peroxynitrite, total ROS and DPPH radical scavenging activities with $IC_{50}$ values of 3.23$\pm$0.04, 2.26$\pm$0.07 and 32.3$\pm$0.13 $\mu$M, respectively. Penicillamine, Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid) and L-ascorbic acid, acting as positive controls, showed radical scavenging activities with $IC_{50}$ values of 6.72$\pm$0.25, 1.43$\pm$0.04 and 11.4$\pm$0.07 $\mu$M, respectively.

• Archives of Pharmacal Research
• /
• 제29권3호
• /
• pp.199-202
• /
• 2006

From the leaves of Goniothalamus tenuifolius, a new natural product namely 3'-hydroxy-3,5,7,4'-tetramethoxyflavone (1) was isolated, along with seven other known compounds (2-8). Each of these isolates was evaluated for free radical scavenging activity on the DPPH decoloration test. The data obtained in this study suggested that the ortho 3',4'-diphenolic structure was essential for the activity of these flavonol derivatives.

• Natural Product Sciences
• /
• 제8권1호
• /
• pp.26-29
• /
• 2002

The MeOH extract of Sorbus commixta (Rosaceae) exhibited strong DPPH radical scavenging activity, and through activity-guided fractionation two antioxidant compounds were isolated and identified as $catechin-7-O-{\beta}-D-xylopyranoside$ (1) and $catechin-7-O-\;{\beta}-D-apiofuranoside$ (2) by physicochemical and spectrometric methods. To evaluate the antioxidant effect of these compounds, some in vitro tests, such as the DPPH radical scavenging activity test, the superoxide radical scavenging activity test and the lipid peroxidation inhibitory activity test, were performed. Compounds 1 and 2 showed stronger activities than both a-tocopherol and butylated hydroxy anisole (BHA) in each assay.

• Environmental Analysis Health and Toxicology
• /
• 제18권3호
• /
• pp.165-174
• /
• 2003

Cr (Ⅵ) - containing compounds are well-established carcinogens, although the mechanism for chromium - induced carcinogenesis is still not well understood. The reduction of Cr (Ⅵ) to its lower oxidation states, par ticularly Cr (V) and Cr (IV), is an important step for the production of chromium-mediated reactive oxygen species (ROS). The persistent oxidative stress during the reduction process may play a key role in the mechanism of Cr (Ⅵ) -induced carcinogenesis. This paper summarizes recent studies on (1) the reduction of Cr (Ⅵ) to Cr (III) occur by a multiplicity of mechanisms depending on the nature of reducing agents including ascorbate, diol-and thiol-containing molecules, certain flavoenzymes, cell organelles, intact cells, and whole animals; (2) free-radical production with emphasis on hydroxy radical generation via Fenton or Haber-Weiss type reactions; and (3) free radical - induced cellular damage, such at DNA strand breaks, hydroxylation of 2'-deoxyguanosine, and activation of nuclear transcription factor kB.