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.

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.

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.

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.