Dongwon Seo

Method validation of 16 types of structural amino acids using an automated amino acid analyzer

An analytical method for the simultaneous determination of 16 types of structural amino acids in infant formula using an automated amino acid analyzer was validated through tests of precision, accuracy and linearity. The automated analysis of the amino acids was performed on an ion-exchange packed column with a visible detector. The certificated reference material (CRM) 1546 from NIST was used as the test sample to determine the precision and accuracy of the analytical method. The regression analyses revealed good correlations [correlation coefficient (r2)] that were greater than 0.99. The recovery values of the amino acids were ranged from 87.18 to 118.08%. The limits of detection and limits of quantification were less than 0.059 mg/100 g and less than 0.198 mg/100 g, respectively. The intra- and inter-day precisions were less than 14.62% in the CRM sample.

Rapid method for the determination of 14 isoflavones in food using UHPLC coupled to photo diode array detection

A rapid method for the determination of 14 types of isoflavones in food using ultra-high performance liquid chromatography (UHPLC) was validated in terms of precision, accuracy, sensitivity and linearity. The UHPLC separation was performed on a reverse-phase C18 column (particle size 2 μm, i.d. 2 mm, length 100 mm) using a photo diode array detector that was fixed to 260 nm. The limits of detection and quantification of the UHPLC analyses ranged from 0.03 to 0.33 mg kg(-1). The intra-day and inter-day precision of the individual isoflavones were less than 11.77% and calibration curves exhibited good linearity (r(2) = 0.99) within the tested ranges. These results suggest that the rapid method used in this study could be available to determine of 14 types of isoflavones in a variety of food such as soy bean, black bean, red bean and soybean paste.

Nephroprotection of plantamajoside in rats treated with cadmium.

Cadmium (Cd), an environmental and industrial pollutant, generates free radicals responsible for oxidative stress. Cd can also lead to various renal toxic damage such as the proximal tubules and glomerulus dysfunction. Plantamajoside (PMS), a major compound of Plantago asiatica (PA), was reported to have the antioxidant effects. In this study, we investigated the protective effects of PMS on Cd-induced renal damage in the NRK-52E cell and rat kidney tissue. Cd exposure increased the ROS generation, lipid peroxidation, serum biochemical values of renal damage, and mRNA and protein expressions of KIM-1 in vitro and in vivo. The significant reduction in glutathione (GSH)/glutathione disulfide (GSSG) ratio and activities of antioxidant enzymes were also observed in the rats treated with Cd. PMS significantly decreased the ROS generation and lipid peroxidation, thus enhancing GSH/GSSG ratio, antioxidant enzyme activities in the cells and rats, and improved histochemical appearances, indicating that PMS has protective activities against Cd-induced renal injury.

Determination of 22 Ginsenosides in Ginseng Products using Ultra-High-Performance Liquid Chromatography

A reverse-phase ultra-high-performance liquid chromatography (u-HPLC) method was developed for the rapid quantification of 22 ginsenosides in ginseng products. The proposed method for the analysis of ginsenosides is based on a heating-block method without further treatment. The u-HPLC separation was performed on a reversed C18 column (100 × 2 mm id, particle size 2 µm) followed by ultraviolet detection at 203 nm. Aqueous 50% methanol was used as the extraction solvent. The optimum amount of extraction solvent and the optimum extraction time were 20 mL and 20 min (extracted twice with 10 mL), respectively. The method validation parameters yielded good results for linearity, precision, accuracy and recovery. The recovery of ginsenosides from ginseng powder was greater than 98.1% and the limits of detection and quantification of the u-HPLC analysis were >0.6 and >1.8 mg/kg for ginsenosides. The calibration graphs for ginsenosides were linear from approximately 2.6 to 40.4 mg/kg for u-HPLC. The inter-day and intra-day precisions (relative standard deviation values) were <14.6 and 14.7%, except for Rg2(R) + Rh1(R).

Analysis of E,E-farnesol and squalene in makgeolli using stir bar sorptive extraction coupled with gas chromatography-mass spectrometry

The aim of this study was to establish an analytical method for the determination of E,E-farnesol and squalene in makgeolli, which is a traditional type of Korean fermented rice wine. E,E-farnesol and squalene in makgeolli were extracted using stir bar sorptive extraction (SBSE) coupled with gas chromatography-mass spectrometry. SBSE was found to be an effective method for analyzing the E,E-farnesol and squalene levels in makgeolli. The linear dynamic range of the SBSE method for detecting E,E-farnesol and squalene ranged from 0.5 to 200 ng/mL with R 2 =0.9974 for E,E-farnesol and 100 to 50000 ng/mL with R 2 =0.9982 for squalene. The limit of detection and the limit of quantification using the SBSE method were 0.1 and 0.5 ng/mL for E,Efarnesol and 15.0 and 40.0 ng/mL for squalene, respectively. The average recoveries obtained were, quantitatively, 101-107% for E,E-farnesol and 98-103% for squalene, respectively, supporting the accuracy of the SBSE-GCMS method.

Rapid Method for Determination of Anthocyanin Glucosides and Free Delphinidin in Grapes Using u-HPLC

A rapid method for the determination of anthocyanin glucosides and free delphinidin in food using ultra-high-performance liquid chromatography (u-HPLC) was validated through tests of precision, accuracy and linearity. The u-HPLC separation was performed on a reversed-phase C18 column (particle size 2 µm, i.d. 2 mm, length 100 mm) with a photodiode array detector. The limits of detection and quantification of the u-HPLC analyses ranged from 0.07 to 0.65 mg/kg for nine types of anthocyanin glucosides and from 0.08 to 0.26 mg/kg for delphinidin aglycone. The intra-day and inter-day precision of individual anthocyanin glucosides and delphinidin aglycone were less than 9.42%. All calibration curves showed good linearity (coefficient of determination = 0.99) within the tested ranges. The rapid and simultaneous u-HPLC method presented in this study significantly improved the speed, sensitivity and resolution of the analyses of nine types of anthocyanin glucosides and free delphidinin aglycone in grapes.

Chemical Characteristics and Flavors of Bamboo-shoot Vinegar

Bamboo Resource Research InstituteAbstract We assessed the quality of a bamboo shoot vinegar produced in Damyang-gun in terms of parameters thatincluded acidity, mineral contents, amino acids, and flavonol aglycones. The flavor compounds of the bamboo shootvinegar were also analyzed using the stir bar sorptive extraction (SBSE) method. The acidity of the bamboo shoot vinegarwas 4.49%, which was the lowest value among the commercial vinegars studied. The bamboo shoot vinegar had a lowerconcentration of Na (8.36 mg/100 g) than the other commercial vinegars. There was a relatively large amount of tyrosineand lysine in the bamboo shoot vinegar. The concentration of quercetin, a flavonol aglycone, was 3.29 mg/100 g. Theresults of the flavor analysis showed that hexanal, 2-furancarboxaldehyde, and benzaldehyde were high in the bambooshoot vinegar. Oleamide, a compound that is known to induce sleep, was first found in bamboo shoot vinegar using theSBSE method.Keywords: bamboo shoot, vinegar, flavor, stir bar sorptive extraction, oleamide

Determination of 2-Propenal Using Headspace Solid-Phase Microextraction Coupled to Gas Chromatography–Time-of-Flight Mass Spectrometry as a Marker for Authentication of Unrefined Sesame Oil

Ascertaining the authenticity of the unrefined sesame oil presents an ongoing challenge. Here, the determination of 2-propenal was performed by headspace solid-phase microextraction (HS-SPME) under mild temperature coupled to gas chromatography with time-of-flight mass spectrometry, enabling the detection of adulteration of unrefined sesame oil with refined corn or soybean oil. Employing this coupled technique, 2-propenal was detected in all tested refined corn and soybean oils but not in any of the tested unrefined sesame oil samples. Using response surface methodology, the optimum extraction temperature, equilibrium time, and extraction time for the HS-SPME analysis of 2-propenal using carboxen/polydimethylsiloxane fiber were determined to be 55°C, 15 min, and 15 min, respectively, for refined corn oil and 55°C, 25 min, and 15 min, respectively, for refined soybean oil. Under these optimized conditions, the adulteration of unrefined sesame oil with refined corn or soybean oils (1–5%) was successfully detected. The detection and quantification limits of 2-propenal were found to be in the range of 0.008–0.010 and 0.023–0.031 µg mL−1, respectively. The overall results demonstrate the potential of this novel method for the authentication of unrefined sesame oil.

Development and Method Validation of Analysis of Urushiol in Sumac and Food Ingredients in Korea

This study developed an analytical method to determine the urushiol content in sap and several foods. The full process for urushiol analysis consists of extraction, trimethylsilyl silylation, analysis, and identification via GC-MS, with each step optimized to attain the required accuracy and precision. Urushiol was separated from sap via liquid-liquid extraction and was derivatized via silylation. The components were analyzed using a polar capillary column and identified using GC-MS. The deviations of relative retention times and retention time windows were within 0.001 and 0.02 min, which satisfied the criteria of 0.06 and 0.03 min, respectively. The response of the urushiol standards tested was found to be linear in the investigated concentration range, with a correlation coefficient of 0.998. The LODs were between 1.74 and 2.67 μg/mL.

Changes in the phenolic compounds and antioxidant activities of mustard leaf (Brassica juncea) kimchi extracts during different fermentation periods

This study was conducted to investigate the changes in the total phenolic content (TPC), total flavonoid content (TFC), and antioxidant activities of 80% methanol and water extracts from mustard leaf kimchi during different fermentation periods. The methanol extract exhibited higher TPC and TFC than the water extract. Both extracts from kimchi fermented for two months showed the highest antioxidant effects against the scavenging activities of 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radicals and 2,2-azino-bis diammonium salt (ABTS) radicals. Moreover, the methanol extract from kimchi fermented for two months showed the highest nitrite scavenging activity. The highest metal (Fe2+) chelating effect of the methanol extract and water extract was observed after three months and one month, respectively. Caffeic acid showed the highest increase with fermentation. These findings suggest that the antioxidant activities of kimchi depend on the fermentation period. Accordingly, this study provides basic data for improving the antioxidant activity of mustard leaf kimchi through the establishment of their fermentation period.