Hyun-Il Jun

Antioxidant Activities and Phenolic Compounds of Pigmented Rice Bran Extracts

UNLABELLED This study was carried out to investigate the antioxidant activities and phenolic compounds of pigmented rice (black, red, and green rice) and brown rice brans. Antioxidant activity was determined by using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical assay, 2,2-azino-bis-(3-ethylenebenzothiozoline-6-sulfonic acid) (ABTS) radical cation assay, reducing power, and chelating ability. Phenolic compounds were measured by using HPLC. Pigmented rice brans were extracted by using aqueous mixtures of acetone, ethanol, and methanol to determine the most effective extraction solvent. Of all solvents examined, extract from 40:60 acetone-water mixtures (v/v) provided the highest DPPH radical assay as well as the highest total phenolic and flavonoid content. We finally selected 40% acetone as an extraction solvent for antioxidant study of pigmented rice bran. Antioxidant activities of 40% acetone extracts of pigmented rice bran, measured in the range of 0 to 1500 μg/mL. At 500 μg/mL concentration, red rice bran, which had the highest total phenolic (259.5 μg/mg) and total flavonoid (187.4 μg/mg) contents, showed the highest antioxidant activity: 83.6%, 71.5%, 1.2%, and 16.4% for DPPH radical assay, ABTS radical cation assay, reducing power, and chelating ability, respectively. Red rice bran showed a lower EC(50) value (112.6 μg/mL) than that of butylated hydroxytoluene (144.5 μg/mL) from the DPPH radical assay. The major phenolic acids of red rice bran were ferulic, vanillic and p-coumaric acids. The results indicated pigmented rice bran might be used as a natural antioxidant. PRACTICAL APPLICATION The present study revealed black and red rice bran shows high antioxidant activities and they contain high amount of phenolic compounds. Indeed, black and red rice bran could be better raw materials for manufacturing the food with high antioxidant activity.

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.

The Effects of Germination Conditions on GABA and the Nutritional Components of Barley

Steeping and germination conditions were investigated in order to produce barley containing a high γ- aminobutyric acid (GABA) content, and the changes in GABA and nutritional components before and after germination were also evaluated in this study. Water absorption rates of three barleys increased alongside both steeping time and steeping temperature. The highest GABA contents of the three barleys, 10.4-14.1 mg/100 g, were obtained from the steeping condition of 25 o C for 24 hr. The GABA contents of germinated barleys ranged from 14.3 to 20.9 mg/100 g, increasing by 3.9 to 14.6 times compared with raw barley. The crude lipid, crude ash and total mineral contents were slightly decreased after germination. The major fatty acids of the three barleys before and after germination were linoleic and palmitic acids. β-glucan contents of three barleys were slightly decreased after germination. Keywards: germination, barley, GABA, nutritional component, β-glucan

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.

Changes in volatile flavor compounds in steam-dried Allium hookeri root

This study was carried out to identify volatile flavor compounds in Allium hookeri root (AHR) and steam-dried AHR. The volatile compounds were extracted using a simultaneous steam distillation and extraction (SDE) method and identified by gas chromatography/mass spectrometry (GC/MS) analysis. Forty volatile compounds, present at a concentration of 76.10 mg/kg, were identified in AHR, with sulfur-containing compounds (96.8%) as the major volatile compounds. On the other hand, in two and four times steam-dried AHR, 34 volatile compounds present at 5.96 mg/kg and 28 compounds present at 4.23mg/kg were identified, respectively. This two and four times steam-dried AHR respectively contained sulfur-containing compounds (64.1 and 37.4%) and aldehydes (19.3 and 45.4%) as the dominant compounds. The sulfur-containing compounds decreased, whereas the aldehydes increased relative to levels in AHR with increased steam-drying time. This is the first report on volatile flavor compounds in AHR and steam-dried AHR.