• Macromolecular Research
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• v.15 no.4
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• pp.324-329
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• 2007

An octa-functional alkoxyamine initiator, with the 2,2,6,6-tetramethyl-l-piperidinyloxy (TEMPO) free radical, was synthesized based on resorcinarene, with its efficiency to initiate the nitroxide-mediated free radical copolymerization of styrene and methyl methacrylate (MMA) described. A difunctional analogue of this initiator was also synthesized, using resorcinol as the core molecule. The structures of the resulting initiators were confirmed by homolysis studies based on electron spin resonance spectroscopy and molecular modeling. The polymerization behavior and characteristics of the polymers obtained using these two initiators were also compared. Well-defined star-shaped and linear random copolymers, with low polydispersities and controlled molecular weights, were prepared. The efficiencies of these initiators towards copolymerization, as well as the parameters permitting the formation of well-defined polymers, were also investigated. The reactivity ratios were $r_a=0.42(a=styrene)\;and\;r_b=0.33(b=MMA)$ for the octa-functional initiator system and $r_a=0.45\;and\;r_b=0.39$ for the difunctional initiator system.

• Preventive Nutrition and Food Science
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• v.16 no.1
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• pp.8-11
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• 2011

In this study, we assessed the free radical scavenging and xanthine oxidase inhibitory activities of extracts isolated from the dried roots and stems (including leaves) of Angelica dahurica. The irritation response from these extracts was also assessed to determine potential cosmetic use. Both sources of A. dahurica extracts exhibited radical scavenging properties to different extents. The free radical scavenging potency ($EC_{50}$) of the stems (including leaves) of A. dahurica was 243.33 ${\mu}g/mL$, which is significantly lower (p<0.01) than that observed of the roots (1,161.79 ${\mu}g/mL$). The inhibition values ($EC_{50}$) of xanthine oxidase were as follows: 435.19 ${\mu}g/mL$ (roots) and 434.66 ${\mu}g/mL$ (stems). We noted no significant differences between the two plant parts with regard to ability to inhibit xanthine oxidase activity. After the application of A. dahurica extracts to rabbits for skin and eye irritation tests, no negative effects were observed; therefore, the extracts are considered to be non-irritating to the skin and eye.

• Preventive Nutrition and Food Science
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• v.19 no.3
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• pp.129-135
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• 2014

The protective role of phloroglucinol against oxidative stress and stress-induced premature senescence (SIPS) was investigated in vitro and in cell culture. Phloroglucinol had strong and concentration-dependent radical scavenging effects against nitric oxide (NO), superoxide anions ($O_2{^-}$), and hydroxyl radicals. In this study, free radical generators were used to induce oxidative stress in LLC-PK1 renal epithelial cells. Treatment with phloroglucinol attenuated the oxidative stress induced by peroxyl radicals, NO, $O_2{^-}$, and peroxynitrite. Phloroglucinol also increased cell viability and decreased lipid peroxidation in a concentration-dependent manner. WI-38 human diploid fibroblast cells were used to investigate the protective effect of phloroglucinol against hydrogen peroxide ($H_2O_2$)-induced SIPS. Phloroglucinol treatment attenuated $H_2O_2$-induced SIPS by increasing cell viability and inhibited lipid peroxidation, suggesting that treatment with phloroglucinol should delay the aging process. The present study supports the promising role of phloroglucinol as an antioxidative agent against free radical-induced oxidative stress and SIPS.

• Korean Journal of Agricultural Science
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• v.38 no.4
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• pp.625-629
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• 2011

To investigate the protective effect of eggplant (Solanum melongena L.) and its active compound, delphinidin, we used in vitro and cellular system. The active fraction from eggplant, BuOH fraction, showed protective effect from hydrogen peroxide-induced oxidative stress in WI-38 fibroblast cells. It suggests that eggplant would have the protective activity from radical-induced oxidative damage and its BuOH fraction would play the crucial role with antioxidative activity. In addition, delphinidin, the active compound from eggplant, exerted the strong 1,1-diphenyl-2-picrylhydrazyl scavenging effect with $IC_{50}$ value of 6.59 ${\mu}g/mL$. Furthermore, the cellular oxidative stress was induced by 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH) in LLC-$PK_1$ cells, while treatment of delphinidin atteunated AAPH-induced oxidative stress as dose-dependent manner. The present study suggests the antioxidative activity of eggplant and delphinidin against free radical-induced oxidative stress.

• Journal of the Korean Chemical Society
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• v.15 no.1
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• pp.37-44
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• 1971

The reaction of amino acids and the reactive hydroxyl radical generated by $Ti^{3+}-H_2O_2$ system was studied using fast flow techniques coupled with ESR. Upon adding methionine to the 0.2M $H_2O_2$ solution (0.05M methionine after addition) and mixing with 0.01M $TiCl_3$, the low field component of the two incompletely resolved peaks, in the spectrum of $Ti^{3+}-H_2O_2$ system alone, vanished completely whereas the high field component remained almost constant and superimposed on the secondary spectrum of the methionine free radical. Similar results were obtained for other amino acids and proteins. The results strongly demonstrate that the $T^{3+}-H_2O_2$ flow system generates two different radical species, only one of which, giving rise to the low field component, is alone responsible for abstracting hydrogen atoms from substrate molecules. The effects of HCl, $H_2SO_4$ and NaOH on the system were also studied with widely varying results.

• Korean Journal of Pharmacognosy
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• v.41 no.3
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• pp.180-184
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• 2010

The antioxidant activity of Desmodium oldhami (Leguminosae) was determined by measuring the radical scavenging effect on DPPH (1,1-diphenyl-2-picrylhydrazyl). The methanolic extract of D. oldhami showed the strong antioxidant activity. Five compounds, kaempferol-3-O-rhamnopyranoside (afzeline) (1), quercetin-3-O-[$\alpha$-L-rhamnopyranosyl($1{\rightarrow}6$)-$\beta$-Dglucopyranoside] (rutin) (2), kaempferol-3-O-glucopyranoside (astragalin) (3), genistein-7-O-$\beta$-D-glucopyranoside (genistin) (4), kaempferol-3-O-rutinoside (5) were isolated from the active ethyl acetate soluble fraction of D. oldhami through repeated silica gel and Sephadex LH-20 column chromatography. Among them, compound 2 showed the most significant antioxidative effect on DPPH free radical scavenging test. Compounds 1-5 are reported for the first time from this plant.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.26 no.1
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• pp.199-212
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• 2000

A series of novel ascorbic acid derivatives, polyethoxylated ascorbic acid (PEAA) were synthesized by coupling ascorbic acid with polyethylene glycol (PEG) of two molecular weights (MW: 350 and 550) at the C-2 or C-3 hydroxyl group (2PEAA350, 3PEAA350, 2PEAA550, 3PEAA550) to increase the stability and retain the activity, as a skin whitening agent. Their stability, scavenging activity against free radical, inhibitory activity against tyroxinase and inhibitory activity of melanin synthesis in Bl6 melanoma cell of PEAAs were evaluated in viかo and compared with those of ascorbic acid and 3-O-ethyl ascorbic acid (3OEAA), a Con stable vitamin C derivative. Among PEAAs, 2PEAA350 and 2PEAA550 tad high scaveniging activity against See radical, inhibitory activity against tyrosinase and inhibitory activity if melanogenesis but low stability, 3PEAA350 had high stability and moderate scavenging activity against free radical, infibitory activity against tyrosinase and inhibitory activity of melanogenesis. The stability, scavenging activity against free radical and inhibitory activity of melanogenesis of 3PEAA350 were higher than those of 30EAA. The most stable 3PEAA350 among PEAAs was nontoxic in various toxicological tests. These results suggest that PEAA would be a good whitening agent far enhancing stability and bioavailability.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2022.09a
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• pp.31-31
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• 2022

Plant-derived antioxidants are used as a healthy diet and are known to inhibit various human diseases. In this study, we investigated free radical scavenging and antioxidant activity of extracts from three plants (Ammannia multiflora, Ammannia coccinea and Salix gracilistyla) with the most DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity from 196 plant extracts inhabiting along Nakdong River in Republic of Korea. The three extracts also have strong total antioxidant activity. Moreover, the extracts inhibited hydrogen peroxide (H₂O₂)-induced reactive oxygen species production and depolarized mitochondrial membrane potential in RAW264.7 macrophages. In zebrafish larvae, 2',7'-dichlorodihydrofluorescein diacetate (DCFDA) fluorescent intensity, induced by H₂O₂, was markedly reduced by the extracts of A. multiflora, A. coccinea and S. gracilistyla. Meanwhile, the extracts were upregulated Nrf2 and HO-1 expression, and an HO-1 inhibitor reversed the extract-induced oxidative responses both in vivo and in vitro. The data suggest that the extracts of A. multiflora, A. coccinea, and S. gracilistyla exert potential free radical scavenging and antioxidant capacities both in vivo and in vitro by activating the Nrf2/HO-1 signaling pathway.

• The Korean Journal of Food And Nutrition
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• v.26 no.4
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• pp.857-864
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• 2013

This study was investigated the effects of heat treatment on polyphenolic compounds and antioxidant activities of yacon. Raw yacon was heated at $100^{\circ}C$ and $121^{\circ}C$ for 15, 30, or 60 min by using an autoclave. The browning intensity, levels of free and bound phenolic and flavonoid compounds, and 1,1-diphenyl-2-picrylhydrazyl(DPPH) and 2,2-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid)(ABTS) radical-scavenging activity of yacon extracts following heat treatment were measured. The browning index, free polyphenolic content, and antioxidant activities in the extracts were significantly increased (p<0.05) with both increased heating temperature and time, while bound polyphenolic levels were decreased. The levels of free phenolic and flavonoid compounds in the yacon extract heated to $121^{\circ}C$ for 60 min were increased by 1.2 and 1.1 folds compared to raw yacon respectively. Moreover, DPPH and ABTS radical-scavenging activities of the yacon heated to $121^{\circ}C$ for 60 min were 1.7 fold and 2.0 fold higher, respectively, than those of raw yacon. A significant (p<0.01) correlation was observed among browning intensity, free and bound phenolic and flavonoid levels, and DPPH and ABTS radical-scavenging activities in heated yacon extract. Thus, heat treatment can be used as a method to enhance the antioxidant compound content in and the antioxidant activity of yacon.

• The Korean Journal of Zoology
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• v.7 no.2
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• pp.1-5
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• 1964

Carbonyl compounds, glycine, ammonia, carbon dioxide and hydrogen have been identified in gamma-irradiated oxygenated aqueous solutions of triglycine. The reactions occurring in this system are postulated only by representing the initial process and the final products. The triglycine molecule undergoes a reaction to form an intermediate giving rise to carbonyl compounds and acid amides. These compounds are decomposed to acetamide, glycine, glyoxylic acid, formic acid, oxalic acid, ammonia, and carbon dioxide by free radical attack in the primary and/or secondary reactions. It is also possible that the unrecognized reactions may give rise to products formed by radical-radical combinations. Satisfactory material balance for all the products have to wait until the completion of a study now in progress.ogress.