• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.57.1-57.1
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• 2011

The effects of relative humidity on the properties of the porous $ZrO_2$ ceramics were investigated in terms of the curing behavior of phenolic resin as a binder. The $ZrO_2$ powders containing 5wt% of phenolic resin were conditioned in a consistent chamber condition at a temperature of $50^{\circ}C$ and different humidity levels (25, 50, 75, and 95%) for 1 h. The exposure of humid atmosphere caused changes of density and microstructure in the green bodies. The higher level the powders were exposed to the humid atmosphere, the lower green density was obtained and the more irregular microstructure was observed due to aggregation by the curing of phenolic resin. After firing, the porosity of specimens has risen from 35.7% to 38.1% and Young's modulus has declined in response to the variation of green density. These results could be explained by the degree of resin cure which was associated with the area under the exothermic peak enclosed by a baseline of DSC thermogram curve. Also, the curing behavior of phenolic resin according to relative humidity has been confirmed by decrease of ether groups which have interacted with the phenolic-OH group and the hexamine as a curing agent. Consequently, it could be demonstrated that increase the relative humidity during fabrication of porous $ZrO_2$ diminished the compaction and properties of specimens after firing owing to curing of phenolic resin.

• Korean Journal of Plant Resources
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• v.33 no.1
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• pp.40-49
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• 2020

The objectives of this study were to evaluate total phenolic content (TPC) and individual phenolic compounds in leaves of perilla genetic resources, assess whether they could be used as distinguishing factor among germplasms, and evaluate their relationship with some quantitative and qualitative morphological characters. TPC and individual phenolic compounds were determined using Folin-Ciocalteu method and UPLC-PDA system, respectively. Wide variations in TPC (7.99 to 133.70 mgGAE/g DE), rosmarinic acid (ND to 21.05 mg/g DE), caffeic acid (ND to 1.17 mg/g DE), apigenin-7-O-diglucuronide (ND to 2.21 mg luteolin equivalent (mgLUE)/g DE), scutellarein-7-O-glucuronide (ND to 5.25 mg LUE/g DE), and apigenin-7-O-glucuronide (ND to 2.81 mg LUE/g DE) were observed. Intensities of green pigment at abaxial and adaxial leaf surfaces were positively correlated with phenolic compounds whereas leaf length and width had negative correlation. Purple pigmented accessions were shorter in leaf length and width but exhibited higher amount of phenolic compounds compared to green pigmented accessions in most cases. Leaf shape was not related with content of phenolic compounds, color of leaves, and length/width of leaves. TPC and individual phenolic compounds along with morphological characters could be useful distinguishing factors for perilla genetic resources.

• Korean Journal of Medicinal Crop Science
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• v.15 no.2
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• pp.120-127
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• 2007

The objective of this research was to evaluate the ability of water and ethanol extracts from mulberry fruit (Morus alba L.) to influence the inhibitory activity of angiotensin converting enzyme (ACE) and xanthine oxidase(XOase). The total phenol contents and sixteen phenolic compounds were investigated in water and ethanol extracts. In order to understand the factors responsible for the potent antioxidant and antihypertensive ability of mulberry, it has been evaluated for anti-oxidative activity using Fenton's reagent/ethyl linoleate system and for free radical scavenging activity using the 1,1-diphenyl-2-picryl hydrazyl free radical generating system. The total phenol contents and total of phenolic compounds in ethanol extract showed higher levels than water extract in mulberry fruit six phenolic compounds (chlorogenic acid, narigin, syringic acid, quercetin, naringenin, kampferol) has a higher individual phenolic compound content in the 60% ethanol extraction than 80% ethanol extract. The inhibitory activity on angiotensin converting enzyme (ACE) were highest in 80% ethanol extract (9.0%). Also, activity of xanthine oxidase(XOase) inhibition appeared highest in 80% ethanol extracts and correlated well with the total phenolic content, which was modulated by the concentration of individual phenolic compounds. This result revealed, that strong biological activity was caused by specific phenol compound contents. Utilization of water and ethanol extracts from mulberry fruit are expected to be good candidate for development into source of free radical scavengers and anti-hypertentive activity

• Korean Journal of Agricultural Science
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• v.11 no.2
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• pp.295-302
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• 1984

The contents of phenolic compounds and its antioxidant activities were investigated in various year stored red and white ginsengs (panax ginseng C.A. Mayer) The results obtained were as follow; 1. Total content of phenolic compounds was lower in free phenolic fraction than in esterified phenolic fraction. 2. The content of free phenolic acid in long storage period was lower han that in short period but no significant difference was observed in esterified phenolic fraction. 3. Maltol, which constitute 50 to 80 percent of total phenolic acid in red and white ginseng. was higher in red ginseng than in white ginseng and was higher in long storage period. 4. Red ginseng showed higher antioxidant activity than white ginserg and no difference in varicus storage periods was observed.

• Food Science and Preservation
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• v.19 no.5
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• pp.735-743
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• 2012

Purple sweet potato (PSP, Ipomoea batatas) has various biological effects including antidiabetic, anti-inflammatory, and antioxidant activities. In this study, the antioxidant activity of PSP after roasting were compared using DPPH, ABTS, and FRAP assays. In addition, the total phenolics and flavonoid contents, Maillard reaction products, and phenolic acid contents were measured to identify the factors that changed PSP,s antioxidant activity due to roasting. The roasted PSP exhibited significantly higher antioxidant activity than unroasted PSP. In particular, the PSP roasted at $200^{\circ}C$ for 10 min showed the highest antioxidant activity among all the PSPs that were roasted under different conditions. The total phenolic and flavonoid contents, Maillard reaction products and phenolic acid contents markedly increased, corresponding to the general increase in antioxidant activities after roasting. These results suggest that roasted PSP extracts are potential source of natural antioxidants that may be used in certain food applications.

• Applied Biological Chemistry
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• v.45 no.3
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• pp.162-167
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• 2002

Free, soluble esterified and insoluble bounded phenolic acids were separated from Eungi chestnut endoderm. The composition and contents of phenolic acid were analyzed by gas chromatography, and their antioxidant activity was examined by DPPH assay, 2-deoxyribose oxidation, and ferric thiocyanate method. Gallic, ellagic, salicylic, and gentisic acids in free phenolic acid fraction, gallic, ellagic, and protocatechuic acids in soluble esterified fraction, sianpic and gentisic acids were the major phenolic acids in insoluble bounded fraction. Marked differences were observed in the phenolic acid composition and contents among the fractions. Free phenolic acid fraction showed the strongest antioxidant activity. Results revealed chestnut endoderm could be a potential antioxidant source containing gallic and ellagic acids.

• Korean Journal of Plant Resources
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• v.27 no.6
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• pp.610-621
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• 2014

Phenolic compounds such as isoflavones contribute to the antioxidant properties of soybean. This study investigated differences in the phenolic content and antioxidant activity of ten soybean cultivars grown in two different locations in Korea. We observed a wide range of variation in total isoflavone and phenolic content by location and cultivar. The total isoflavone content of cultivars grown at Pyeongchang (sub-highland) was significantly higher than that in cultivars grown at Gangneung (lowland). In contrast, the total phenolic content of cultivars grown at Gangneung was greater than that of cultivars grown at Pyeongchang. The radical scavenging activity of DPPH was similar to that of the total phenolic content rather than that of the total isoflavone content. These results suggest that antioxidant activity of soybean was associated with phenolic compounds rather than isoflavones. To identify the individual antioxidant components, we used an on-line HPLC-$ABTS^+$-based assay system, ESI/MS, and NMR. The results showed that the strongest antioxidant activity was linked to epicatechin.

• Journal of the Korean Society of Food Science and Nutrition
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• v.32 no.6
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• pp.948-951
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• 2003

The composition and antioxidative effects of phenolic compounds in black rice were studied. The contents of free and bound phenolic compounds extracted from black rice were 845.4 and 401.6 mg respectively per 100g sample weight. Free phenolic compounds had higher antioxidation ability than those of bound phenolic compounds. Solvent fractionation of free phenolic compounds revealed that butanol fraction had the highest phenolic compounds contents and antioxidative activity among other solvent fractions. Although butanol fraction showed lower lipid peroxidation inhibition (LPI) ability than that of $\alpha$-tocopherol and BHT, free radical scavenging ability was much higher than that of $\alpha$-tocopherol and BHT, as evidenced by electron donating ability (EDA) and benzoic acid hydroxylation inhibition (BAHI) assays.

• Environmental Engineering Research
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• v.24 no.1
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• pp.127-136
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• 2019

Land application of treated palm oil mill effluent (TPOME) could be used as an alternative tertiary wastewater treatment process. However, phenolic compounds in TPOME might be leached to the environment. This study investigated the ability of grasses on reducing phenolic compounds in the leachate after TPOME application. Several pasture grasses in soil pots were compared after irrigating with TPOME from stabilization ponds, which contained 360-630 mg/L phenolic compounds. The number of soil bacteria in planted pots increased over time with the average of $10^8CFU/g$ for mature grasses, while only $10^4-10^6CFU/g$ were found in the unplanted control pots. The leachates from TPOME irrigated grass pots contained lower amounts of phenolic compounds and had lower phytotoxicity than that of control pots. The phenol removal efficiency of grass pots was ranged 67-93% and depended on grass cultivars, initial concentration of phenolic compounds and frequency of irrigations. When compared to water irrigation, TPOME led to an increased phenolic compounds accumulation in grass tissues and decreased biomass of Brachiaria hybrid and Brachiaria humidicola but not Panicum maximum. Consequently, the application of TPOME could be conducted on grassland and the grass species should be selected based on the utilization of grass biomass afterward.

• Composites Research
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• v.33 no.6
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• pp.329-335
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• 2020

In this study, the thermo-rheological behaivors of petroleum pitches with different softening points were studied, and a B-stage phenolic resins/petroleum pitches blends were prepared by adding petroleum pitches to the phenolic resins. As a result, the petroleum pitch with different softening points decreased the fluidity of the petroleum pitch as the Quinoline insoluble (QI) content increased and showed the viscous properties of the solid. In addition, the effect of adding petroleum pitches having different softening points on the thermo-rheological properties of phenolic resins was investigated. When petroleum pitch with a high softening point was added, the fluidity of the phenolic resin was reduced, and the hardening behavior was fast. It was possible to control the curing rate and curing behavior of the phenolic resin by adding petroleum pitches of different softening points. Among them, the phenolic resin mixture to which P-Pitch 2 was added has a higher fluidity than other blends under the same curing temperature condition.