Young-Soo Kim

Structural characterization of phenolic antioxidants from purple perilla (Perilla frutescens var. acuta) leaves

The antioxidant activities of various extracts from purple perilla (Perilla frutescens var. acuta) leaves based on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging ability, 2,2-azino-bis-(3-ethylenebenzothiozoline-6-sulfonic acid) (ABTS) radical cation scavenging ability, and reducing power were investigated. Purple perilla leaves were initially extracted with 80% ethanol and then sequentially fractionated according to solvent polarity. Of all fractions, the ethyl acetate fraction had the highest antioxidant activity. This fraction was separated into four sub-fractions (sub-fractions 1-4) by Sephadex LH-20 chromatography. Of the four sub-fractions, sub-fraction 3 had the highest antioxidant activity. The EC50 values of sub-fraction 3 for DPPH radical scavenging activity and reducing power were 2.4 and 1.7 times lower than those of butylated hydroxytoluene (BHT), respectively. Based on HPLC analysis, the most abundant phenolic acid in sub-fraction 3 of purple perilla leaves was rosmarinic acid, at 314.3 mg/g. The structure of rosmarinic acid was confirmed by ESI-IT-TOF MS and NMR analysis.

Chemical composition and antioxidant activity of Korean cactus (Opuntia humifusa) fruit

The chemical composition and antioxidant activities of the Korean cactus (Opuntia humifusa, OH) fruit were investigated in this study. Major minerals in the OH fruit were P, Ca, and Mg. Total dietary fiber content was 22.8% and the soluble dietary fiber/insoluble dietary fiber ratio was 1:1.3. An 80% ethanol extract was used to investigate antioxidant activities based on DPPH radical scavenging ability as well as total phenolic and flavonoid content. OH fruit extract from 80% ethanol was sequentially fractionated according to the polarity of solvents. Among various fractions, the ethyl acetate fraction showed the highest antioxidant activity as well as the highest total phenolic and total flavonoid contents compared to other fractions. The most abundant phenolic acid in the ethyl acetate fraction was ferulic acid, followed by protocatechuic acid. The most abundant flavonoid was taxifolin, followed by myricetin. The results suggested that OH fruit could be a good potential source of antioxidant.

Improved cognitive performance following supplementation with a mixed-grain diet in high school students: a randomized controlled trial.

OBJECTIVE Adolescence is a stage of rapid growth, when rich nutritional supplementation is important. Maintaining optimal cognitive functioning is critical in high school students, who are under considerable academic pressure. The objectives of this study were to identify the effects of a 9-wk randomly assigned diet of mixed grains versus a regular diet on cognitive performance and on levels of plasma brain-derived neurotrophic factor (BDNF) and S100B, a calcium-binding protein produced by astroglial cells, in healthy high school students (grades 10 and 11). METHODS In this 9-wk, single-blind, controlled study, subjects were randomly allocated to either a mixed-grain or a regular diet. Cognitive assessments and measurements of plasma BDNF and S100B levels were performed at baseline and after the 9-wk intake of a mixed-grain or regular diet. Computerized neuropsychological tests and self-rating scales were used for the cognitive assessments. RESULTS Significant improvements in some neuropsychological tests were found after 9 wk in both the mixed-grain and the regular-diet groups, but the changes from baseline between the two groups were not significantly different. Significant impairments on the AX-continuous performance test were observed at the endpoint in the regular-diet group, and the changes from baseline between the two groups were also significantly different for this test. A significant difference in changes in BDNF levels was observed between the two groups. CONCLUSIONS These results suggest that intake of mixed grains for 9 wk is beneficial for cognitive performance and plasma BDNF levels in high school students. These beneficial effects seem to be related to the prevention of cognitive deterioration in a mental-fatigue test with the mixed-grain diet, rather than cognitive enhancement per se.

Isolation and identification of phenolic antioxidants in black rice bran.

Black rice bran contains phenolic compounds of a high antioxidant activity. In this study, the 40% acetone extract of black rice bran was sequentially fractionated to obtain 5 fractions. Out of the 5 fractions, ethyl acetate fraction was subfractionated using the Sephadex LH-20 chromatography. The antioxidant activity of phenolic compounds in the extracts was investigated by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical assay, 2,2-azino-bis-(3-ethylenebenzothiozoline-6-sulfonic acid) (ABTS) radical cation assay, reducing power. The subfraction 2 from ethyl acetate fraction had the highest total phenolic contents (TPC) (816.0 μg/mg) and the lowest EC50 values (47.8 μg/mL for DPPH radical assay, 112.8 μg/mL for ABTS radical cation assay, and 49.2 μg/mL for reducing power). These results were 3.1, 1.3, and 2.6 times lower than those of butylated hydroxytoluene (BHT), respectively. At a concentration of 100 μg/mL, the antioxidant activity and TPC of various extracts was closely correlated, with correlation coefficients (R(2) ) higher than 0.86. The major phenolic acid in subfraction 2 was identified as ferulic acid (178.3 μg/mg) by HPLC and LC-ESI/MS/MS analyses. Our finding identified ferulic acid as a major phenolic compound in black rice bran, and supports the potential use of black rice bran as a natural source of antioxidant.

Physicochemical properties and antioxidant activity of Korean cactus (Opuntia humifusa) cladodes

Physicochemical properties and antioxidant activity of Korean native cactus (Opuntia humifusa) cladodes (KCC) were investigated to evaluate the possibility for its application in new health functional foods. The KCC showed a high amount of crude ash (201.2 g·kg−1 DW), characterizing Ca (1,967.8 mg·100 g−1 DW), Mg (1,411.2 mg·100 g−1 DW), K (1,269.6 mg·100 g−1 DW), and P (1,110 mg·100 g−1 DW) as the major minerals, as well as a high total dietary fiber (503.3 g·kg−1 DW) including soluble dietary fiber (233.2 g·kg−1 DW). The water holding capacity (WHC), oil holding capacity (OHC), and swelling power of KCC were 20.6 g·g−1, 2.6 g·g−1, and 16.8 mL·g−1, respectively. The viscosity of a 100 g·L−1 KCC suspension showed a non-Newtonian flow behavior with shear thixotropy and time dependency. The ethyl acetate fraction from an 80% ethanol extract of KCC showed the highest antioxidant activity as well as the highest total phenolic (112.8 g·kg−1 fraction) and flavonoid (89.7 g·kg−1 fraction) contents compared to other fractions. The most abundant phenolic compound within the ethyl acetate fraction was taxifolin (13.97 g·kg−1 fraction). The results suggest that KCC could be used as potential sources of Ca and dietary fiber as well as a natural antioxidant. It might be possible to manufacture functional food products using the unique physical properties of KCC.

Isolation and characterization of phenolic compound from Allium hookeri root for potential use as antioxidant in foods

This study was carried out to identify phenolic compounds with antioxidant activity from Allium hookeri root (AHR). A methanol extract of AHR was sequentially fractionated and separated based on solvent polarity (methylene chloride, ethyl acetate, and n-butanol) using column chromatography (Sephadex LH-20 and Kiesel gel 60). The antioxidant activity of AHR was investigated by assessing the 1,1-diphenyl-1-picrylhydrazyl radical scavenging activity (DPPH RSA), superoxide quenching activity (SQA), and superoxide radical scavenging activity (SRSA) of the isolated fractions. Based on the DPPH RSA results and yield of each fraction, the n-butanol fraction (8.4-85.2% and 3.9%) was selected for further analysis. There was no significant difference between the EC50 value for SRSA of compound 1 purified from the n-butanol fraction and ascorbic acid. We identified compound 1 using mass spectrometry (MS) and nuclear magnetic resonance (NMR) as ferulic acid-4-O-β-Dglucopyranoside (FAG). Thus, this is the first report of a FAG isolated from AHR.

Antioxidant activity of phenolic compounds from canola ( Brassica napus ) seed

The antioxidant activities of various extracts from canola (Brassica napus) seed were investigated using the DPPH assay, ABTS radical assay, and reducing power. An 80% methanol extract from canola seed was sequentially fractionated and separated according to the solvent polarity and Sephadex LH-20 chromatography, respectively. The antioxidant activities of various extracts and their total phenolic content (TPC) and total flavonoid content (TFC) were closely correlated, resulting in correlation coefficient values higher than 0.87. Of all extracts, the sub-fraction 3 had the highest TPC (462.3 μg/mg) and TFC (75.4 μg/mg) while it showed the lowest EC50 value (183.1 μg/mL). The EC50 value of sub-fraction 3 measured using the DPPH radical assay was 1.3 times lower than that of butylated hydroxytoluene (BHT). The major free phenolic compound was trans-sinapic acid (193.4 μg/mg) and sinapic acid derivatives identified as 1-O-β-d-glucopyranosyl sinapate and 1,2-di-O-sinapoyl-β-d-glucose in sub-fraction 3.

Flow Behaviors of Fruit and Stem Extracts from Korean Cactus (Opuntia humifusa)

Water extracts from the fruit and stem of Korean cactus (Opuntia humifusa, OH) showed a prototypical pseudo-plastic behavior. The pseudo-plasticity was increased with increasing concentration and decreasing temperature. The extract from the stems showed higher shear stress, consistency, and yield stress than that from fruits. The flows were examined at different concentrations, temperatures, pH, and salt content. The activation energies from fruits and stems increased from 4.127×103 to 1.584×103 J/kg·mol and from 16.162×103 to 10.014×103 J/kg·mol, respectively, as concentration increased. The concentration-dependant constant K1 from fruits and stems decreased from 0.233 to 0.185 mPa·s and from 30.476 to 66.198mPa·s, respectively, as temperature increased. The viscosity from fruits and stems increased as pH increased, while decreased as Ca2+ concentration increased. The unusual flow behaviors of stems and fruits might play a major role in developing food products using OH extracts.

Mixed grain containing giant embryonic brown rice improves postprandial glycaemic response in healthy subjects

Aim Mixed grain, which contributes to lowered glycaemic responses, has been shown to be effective in dietary management of patients with impaired glucose tolerance or diabetes. Methods The present study determined the postprandial blood glucose response of 20 healthy volunteers to mixed grains containing giant embryonic rice (MG-GER) or giant embryonic brown rice (MG-GEBR) compared with white rice (WR) in a randomised crossover design. Plasma glucose and serum insulin at 0, 15, 30, 45, 60, 90, 120, 150 and 180 minutes were measured, and glycaemic index (GI) and incremental area under the curve (iAUC) were calculated. Results The GIs for WR, MG-GER and MG-GEBR were 86.75 ± 5.78, 76.09 ± 7.01 and 69.33 ± 6.54, respectively. The 120-minute iAUCs after administration of MG-GER or MG-GEBR were significantly lower than that of WR. In addition, the MG-GEBR diet group had a significantly lower C-peptide concentration at the 120-minute time point when compared to the WR group. Conclusions These results suggest that consumption of MG-GER or MG-GEBR instead of WR is more effective to reduce postprandial glucose levels without increasing insulin secretion.

Construction and Tests of the Vacuum Pumping System for KSTAR Current Feeder System

Current feeder system (CFS) for Korea superconducting tokamak advanced research(KSTAR) project plays a role to interconnect magnet power supply (MPS) and superconducting (SC) magnets through the normal bus-bar at the room temperature(300 K) environment and the SC bus-line at the low temperature (4.5 K) environment. It is divided by two systems, i.e., toroidal field system which operates at 35 kA DC currents and poloidal field system wherein 2026 kA pulsed currents are applied during 350 s transient time. Aside from the vacuum system of main cryostat, an independent vacuum system was constructed for the CFS in which a roughing system is consisted by a rotary and a mechanical booster pump and a high vacuum system is developed by four cryo-pumps with one dry pump as a backing pump. A self interlock and its control system, and a supervisory interlock and its control system are also established for the operational reliability as well. The entire CFS was completely tested including the reliability of local/supervisory control/interlock, helium gas leakage, vacuum pressure, and so on.