• Journal of Marine Bioscience and Biotechnology
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• v.7 no.1
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• pp.19-27
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• 2015

The objective of the current study was to evaluate the inhibitory and antioxidant activities of powdered katsuobushi (dried bonito) protein hydrolysates and their corresponding fractions. The powdered katsuobushi (dried bonito) hydrolysates were obtained by enzymatic hydrolysis using Alcalase, ${\alpha}$-chymotrypsin, Neutrase, pepsin, papain, and trypsin. The antioxidant efficacy of the respective hydrolysates were evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl, superoxide, and alkyl radical-scavenging activities. Among the hydrolysates, the peptic-derived hydrolysate exhibited the highest antioxidant activity compared to other enzymatic hydrolysates. Therefore, the peptic-derived hydrolysate was further analyzed, and was found to contain an active peptide with an amino acid sequence identified as Pro-Met-Pro-Leu-Asn-Ser-Cys (756 Da). The purified peptides from powdered katsuobushi (dried bonito) had an $EC_{50}$ value of $105.82{\mu}M$, and exhibited an inhibitory effect against DNA oxidation induced by hydroxyl radicals. Taken together, these results suggests that powdered katsuobushi (dried bonito) could be used as a natural antioxidant in functional foods and prevent oxidation reactions in food processing.

• Preventive Nutrition and Food Science
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• v.17 no.4
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• pp.261-268
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• 2012

Ribes diacanthum Pall (RDP) is a member of the Saxifragaceae family. The plant is traditionally used in Mongolia for the treatment of various ailments associated with kidney and bladder's diseases, cystitis, kidney stone, and edema. This study was aimed to investigate antioxidant activities of different solvent extracts of whole Pall plants, based on ferric-reducing antioxidant potential (FRAP), 2,2'-azinobis(3-ethybenzothiazoline-6-sulfonic acid) ($ABTS{\cdot}+$) radical scavenging activity, 1,1-diphenyl-2-picrydrazyl ($DPPH{\cdot}$), and hydroxyl (${\cdot}OH$) radical scavenging activities. Additionally, total flavonoids and phenolic contents (TPC) were also determined. The ethyl acetate extract of RDP (EARDP) had a remarkable radical scavenging capacity with an $IC_{50}$ value of 0.1482 mg/mL. In addition, EARDP was shown to be higher in total phenolic and flavonoid contents than the methanol extract of RDP (MRDP). Moreover, the EARDP had the predominant antioxidant capacity, DPPH, hydroxyl, and ABTS radical scavenging activities and ferric reducing power. These results suggest a potential for R. diacanthum Pall extract as a functional medicinal material against free-radical-associated oxidative damage.

• Korean Journal of Medicinal Crop Science
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• v.19 no.5
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• pp.341-346
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• 2011

The objective of this study was to evaluate antioxidant activities of Rehmannia glutinosa (Raw Jihwang) by traditional method. The total phenol content of Rehmannia radix Preparata (the final cycle of Jihwang) was increased to 205%, compared with Rehmannia glutinosa. Antioxidant activities, determined by ferric-reducing antioxidant potential (FRAP), 2,2'-azinobis(3 ethybenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activity, 1,1-diphenyl-2-picrydrazyl (DPPH) and hydroxyl radical scavenging activities, increased remarkably as the number of steaming-drying cycles increased. Especially, FRAP value increased 285%. Also, $IC_{50}$ values for DPPH and hydroxyl radical scavenging activities of the final 9th-cycling product, decreased 48.4% and 76%, respectively, compared with those of Rehmannia glutinosa. Our result was suggested that antioxidant activities of Rehmannia radix Preparata improve according to the increasing number of steaming-drying cycles.

• Preventive Nutrition and Food Science
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• v.15 no.1
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• pp.30-35
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• 2010

The potential biological activities of methanol extract and 5 fractions (hexane, $CH_2Cl_2$, EtOAc, BuOH and water) from roots of Astragalus membranaceus were examined by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, hydroxyl radical (${\cdot}OH$) scavenging activity, reducing power assays, lipid peroxidation inhibitory activity, $\alpha$-amylase and $\alpha$-glucosidase inhibition assays. The EtOAc fraction showed high DPPH free radical scavenging activity ($EC_{50}=170.34\;{\mu}g/mL$), hydroxyl radical scavenging activity ($EC_{50}=32.14\;{\mu}g/mL$), lipid peroxidation inhibitory activity ($EC_{50}=52.46\;{\mu}g/mL$) and a concentration dependence, with OD value ranging from 0.234 to 0.345 (0.1 to 0.5 mg/mL), for reducing power. The EtOAc fraction has the highest total phenolic content ($142.13\;Gal\;{\mu}g/mg$) and the $CH_2Cl_2$ fraction has the highest flavonoid content ($71.63\;Que\;{\mu}g/mg$). Meanwhile, hexane and EtOAc showed certain $\alpha$-amylase and $\alpha$-glucosidase inhibition activities. These results suggest that the methanol extract and fractions from Astragalus membranaceus root have significant antioxidant and anti-diabetes activities, which could be used as a potential source of pharmaceutical materials.

• Macromolecular Research
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• v.10 no.2
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• pp.108-114
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• 2002

Poly(butylene succinate) (PBS) prepolymers were prepared by the condensation polymerization of 1,4-butanediol (1,4-BD) and succinic atid (SCA) in the presence of titanium (VI) isoproxide(TPI) catalyst. The PBS prepolymers reacted with 1,4-BD or SCA to obtain hydroxyl or carboxylic acid group terminated PBS. High molecular weight linear or branched PBS was synthesized by a coupling reaction between hydroxyl and carboxylic acid group terminated PBS, or by a branching reaction between carboxylic acid group terminated PBS and glycerol as a branching agent. The weight average molecular weight of the prepared linear or branched PBS was in the range of 100,000-220,000. Both melting point and thermal stability of the high molecular weight linear and branched PBSs were somewhat higher than those of general PBS. From a tensile behavior by Instron test, modulus, tensile strength and elongation at break improved with increase in the molecular weight of the prepared PBS through the coupling or the branching reaction. In particular, the high molecular weight linear PBS had about 2.5 times higher value in modulus than the branched one.

• Preventive Nutrition and Food Science
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• v.11 no.1
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• pp.10-16
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• 2006

Radical scavenging and antioxidant activities of Laminaria japonica and fermented its extracts were evaluated. Freeze-dried L. japonica was fermented by Aspergillus oryzae and extracted with distilled water. The extract solution was mixed with ethanol and centrifuged. The supernatant was ethanol soluble fraction, non-polysaccharide fraction (ESF), and residue was ethanol insoluble precipitation, polysaccharide fraction (EIP). ESF was subjected to sequential fractionation with dichloromethane, ethyl acetate, butanol and water. To determine the radical scavenging and antioxidant activities of these, DPPH radical, hydroxyl radical, superoxide anion radical scavenging activities and linoleic acid oxidation were tested. Among the extracts, ESF of fermented L. japonica showed the highest radical scavenging activity. The ESF showed DPPH radical scavenging activity of 64.33% at concentration of $50{\mu}g/mL$. It was higher than 57.70% of vit. C. Ethyl acetate and butanol fraction had high value of radical scavenging and antioxidant activities, especially butanol fraction of fermented L. japonica was 79.48 % of hydroxyl radical scavenging activity at concentration of $50{\mu}g/mL$. The fermented L japonica had radical scavenging and antioxidant activities higher than L. japonica. These results suggest that fermented L japonica is healthy food having radical scavenging and antioxidant activities.

• Journal of Life Science
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• v.12 no.2
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• pp.75-79
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• 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.

• Applied Chemistry for Engineering
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• v.5 no.4
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• pp.737-742
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• 1994

The fracture energy of glass fiber/carbon fiber/epoxy resin hybrid composite system was investigated in the aspect of fracture mechanism. Epoxy resin matrix was DGEBA-MDA-SN-HQ system. On the interface of glass fiber and matrix, post debone friction energy provided a major contribution to the fracture energy, and debonding energy and pull-out energy were of the similar value. In the case of fracture on the interface of carbon fiber and matrix, pull-out energy was the major contributor.

• Bulletin of the Korean Chemical Society
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• v.34 no.10
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• pp.2883-2888
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• 2013

To enhance the power conversion efficiency of dye-sensitized solar cell (DSSC), the surface of titanium dioxide ($TiO_2$) photoelectrode was modified by hydroxylation treatment with $NH_4OH$ solution at $70^{\circ}C$ for 6 h. The $NH_4OH$ solutions of various concentrations were used to introduce the hydroxyl groups on $TiO_2$ surface. As the concentration of $NH_4OH$ was increased, the short-circuit current density ($J_{SC}$) value and conversion efficiency of solar cells were increased because the amount of adsorbed dye molecules on $TiO_2$ surface was increased. As a result of the surface modification to introduce hydroxyl groups, the concentration of adsorbed dye on the $TiO_2$ surface could be improved up to 32.61% without the changes of morphology, surface area and pore volume of particles. The morphology, the specific surface area, the pore volume and the chemical states of $TiO_2$ surface were characterized by using FE-SEM, $N_2$ adsorption-desorption isotherms and XPS measurements. The amount of adsorbed dye and the performance of fabricated cells were analyzed by using UV-Vis absorption spectroscopy and solar simulator.

• Journal of Microbiology and Biotechnology
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• v.23 no.2
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• pp.218-224
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• 2013

The aldo-keto reductases catalyze reduction reactions using various aliphatic and aromatic aldehydes/ketones. Most reductases require NADPH exclusively as their cofactors. However, NADPH is much more expensive and unstable than NADH. In this study, we attempted to change the five amino acid residues that interact with the 2'-phosphate group of the adenosine ribose of NADPH. These residues were selected based on a docking model of the YOL151W reductase and were substituted with other amino acids to develop NADH-utilizing enzymes. Ten mutants were constructed by site-directed mutagenesis and expressed in Escherichia coli. Among them, four mutants showed higher reductase activities than wild-type when using the NADH cofactor. Analysis of the kinetic parameters for the wild type and mutants indicated that the $k_{cat}/K_{m}$ value of the Asn9Glu mutant toward NADH increased 3-fold. A docking model was used to show that the carboxyl group of Glu 9 of the mutant formed an additional hydrogen bond with the 2'-hydroxyl group of adenosine ribose. The Asn9Glu mutant was able to produce (R)-ethyl-4-chloro-3-hydroxyl butanoate rapidly when using the NADH regeneration system.