Keun-Hyung Park

Identification and Antimicrobial Activity of Phenylacetic Acid Produced by Bacillus licheniformis Isolated from Fermented Soybean, Chungkook-Jang

A bacterial strain, B65-1, which showed strong antimicrobial activity, was isolated from Chungkook-Jang, a traditional Korean fermented-soybean food with antimicrobial properties. Based on carbon utilization pattern and partial 16S rRNA sequence analysis, the B65-1 strain was identified as Bacillus licheniformis. An antibiotic compound, active against bacteria and yeast such as Staphylococcus aureus, Escherichia coli, and Candida albicans, was isolated by various chromatographic procedures from culture filtrates of B. licheniformis B65-1. The purified antibiotic was identified to be phenylacetic acid, with the molecular formula C8H8O2 by analyses of EI-MS and NMR. The phenylacetic acid was detected in fermented soybean made with the strain B65-1 as a starter, but was not present in extracts of nonfermented soybean. Our results indicated that the phenylacetic acid produced by B. licheniformis during fermentation of soybean is one of the main compounds of antimicrobial activity of Chungkook-Jang.

Isolation and Characterization of Antifungal Substances from Burkholderia sp. Culture Broth

A new antagonistic Burkholderia strain, designated MP-1 and producing antifungal activities against various filamentous plant pathogenic fungi, was isolated from the rhizoshere in the Naju area. Cultural characteristic studies strongly suggested that this strain belongs to the genus Burkholderia. The nucleotide sequence of the 16S rRNA gene (1491 pb) of strain MP-1 exhibited close similarity (99% to 100%) with other Burkholderia 16S rRNA genes. Extraction of fermentation broth of Burkholderia sp. MP-1 and various separations and purification steps led to isolation of four pure active molecules. The chemical structure of these four compounds—named phenylacetic acid, hydrocinnamic acid, 4-hydroxyphenylacetic acid, and 4-hydroxyphenylacetate methyl ester—was established on the basis on their gas chromatography–electron impact–mass spectrometry (GC-EI-MS) and trimethylsilation GC-EI-MS data. The four isolated compounds inhibited filamentous fungal growth on potato dextrose agar medium supplemented with 100 mg/L of phenylacetic acid, hydrocinnamic acid, 4-hydroxyphenylacetic acid and 4-hydroxyphenylacetate methyl ester individually.

Coumaroyl quinic acid derivatives and flavonoids from immature pear ( Pyrus pyrifolia nakai) fruit

Fourteen compounds were isolated from 60% ethanol extracts of immature pear (Pyrus pyrifolia Nakai cv. Chuhwangbae) fruit using Amberlite XAD-2 column HPLC with guided DPPH radical scavenging assay. Based on MS and NMR analysis, the isolated compounds were identified as 5-O-trans-caffeoyl quinic acid methyl ester (1), malaxinic acid (2), 5-O-trans-p-coumaroyl quinic acid methyl ester (3), 5-O-cis-p-coumaroyl quinic acid methyl ester (4), 5-O-trans-p-coumaroyl quinic acid (5), trans-p-coumaric acid (6), methyl cis-p-coumarate (7), methyl trans-p-coumarate (8), 3,5-O-dicaffeoyl quinic acid (9), (-)-epicatechin (10), (S)-(+)-2-cis-abscisic acid (11), isorhamnetin 3-O-β-d-galacto-pyranoside (12), isorhamnetin-3-O-β-d-glucopyranoside (13), and isorhamnetin 3-O-α-l-rhamnopyranosyl (1→6)-O-β-d-glucopyranoside (14). Six compounds (1, 2, 6, 9, 10, and 13) were identified previously, but other compounds (3–5, 7, 8, 11, 12, and 14) were isolated for the first time from pear.

Caffeoyl Triterpenes from Pear (Pyrus pyrifolia Nakai) Fruit Peels and Their Antioxidative Activities against Oxidation of Rat Blood Plasma

Six triterpenes, including three caffeoyl triterpenes, were purified and isolated from pear fruit ( Pyrus pyrifolia Nakai cv. Chuwhangbae) peel extracts using various column chromatography techniques with a guided 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging assay. The isolated compounds were identified as betulinic aldehyde (1), lupeol (2), betulinic acid (3), 3-O-cis-caffeoylbetulinic acid (4), 3-O-trans-caffeoylbetulinic acid (5), and 3-O-trans-caffeoyloleanolic acid (6) on the basis of nuclear magnetic resonance spectroscopy and electrospray ionization mass spectrometry. Four compounds (1, 4-6) were identified from Asian pear fruit for the first time. In addition, compounds 4-6, containing a caffeic acid moiety, showed higher DPPH radical-scavenging and suppression effects against copper ion-induced oxidation of rat blood plasma than other compounds without a caffeic acid moiety.

Hydroxycinnamoylmalic acids and their methyl esters from pear (Pyrus pyrifolia Nakai) fruit peel.

Two novel caffeoylmalic acid methyl esters, 2-O-(trans-caffeoyl)malic acid 1-methyl ester (6) and 2-O-(trans-caffeoyl)malic acid 4-methyl ester (7), were isolated from pear (Pyrus pyrifolia Nakai cv. Chuhwangbae) fruit peels. In addition, 5 known hydroxycinnamoylmalic acids and their methyl esters were identified: 2-O-(trans-coumaroyl)malic acid (1), 2-O-(cis-coumaroyl)malic acid (2), 2-O-(cis-coumaroyl)malic acid 1-methyl ester (3), 2-O-(trans-coumaroyl)malic acid 1-methyl ester (4), and 2-O-(trans-caffeoyl)malic acid (phaselic acid, 5). The chemical structures of these compounds were determined by spectroscopic data from ESI MS and NMR. Of all the isolated compounds, five hydroxycinnamoylmalic acids and their methyl esters (2-4, 6, 7) were identified in the pear for the first time.

Comparison of the content of bioactive substances and the inhibitory effects against rat plasma oxidation of conventional and organic hot peppers (Capsicum annuum L.).

The aim of this study was to evaluate the chemical compositions and antioxidative activities of hot pepper fruits cultivated with strict management by organic and conventional agricultural practices. The ascorbic acid content in the organically grown hot pepper (OGP) was significantly higher than that of conventionally grown hot pepper (CGP) in both green and red fruits. The content of other bioactive compounds such as flavonoids (apigenin, luteolin, quercetin) and total phenolics in OGP was typically higher than in CGP regardless of fruit color. In addition, the ABTS(+) radical-scavenging activity of OGP red fruits was significantly higher than that of CGP red fruits. Moreover, regardless of the color of the fruits, a higher antioxidative activity was observed in blood plasma from rats administered the OGP fruit extracts than in blood plasma from rats administered the CGP fruit extracts. It was hypothesized that the higher antioxidant activity of the OGP fruits may have resulted from the higher antioxidant content in the OGP fruits. These results suggest that consumption of pepper fruits may increase antioxidant activity in the blood, and OGP fruits may be more effective in increasing this antioxidant activity than CGP fruits.

Isolation and identification of antioxidative phenolic acids and flavonoid glycosides from Camellia japonica flowers

The ethyl acetate (EtOAc) layer of the hot water extracts of Camellia japonica flowers was found to have higher 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity than the other solvent layers. Nine phenolic compounds were isolated and purified from the EtOAc layer by Sephadex LH-20 column chromatography and octadecyl silane-high performance liquid chromatography using a guided DPPH radical-scavenging assay. The isolated compounds were identified as 3,4,5-trihydroxybenzoic acid (1), 3,4-dihydroxybenzoic acid (2), 4-hydroxybenzoic acid (3), 2,3-digalloyl-O-α-d-glucopyranoside (4), 2,3-digalloyl-O-β-d-glucopyranoside (5), quercetin 3-O-β-d-galactopyranoside (6), quercetin 3-O-β-d-glucopyranoside (7), kaempferol 3-O-β-d-galactopyranoside (8), and kaempferol 3-O-β-d-glucopyranoside (9), based on mass spectrometry and nuclear magnetic resonance. Four compounds (6–9) had been previously identified in the leaves of this plant, but other compounds (1–5) were newly isolated from this plant. Their DPPH radical-scavenging activities based on the 50% scavenging concentration decreased in the following order: 4 = 5 (4.7 μM) > 1 (9.8 μM) > 6 = 7 (8.2 μM) > α-tocopherol (24.7 M) > ascorbic acid (25.1 μM) > 2 (35.6 M) > 3 = 8 = 9 (> 250 μM). Quercetin glycosides (6, 7), gallic acid (1) and its glucosides (4, 5) showed higher DPPH radical-scavenging activities than other compounds. These results indicate that the antioxidant effect of C. japonica flowers may be attributable to quercetin glycosides and gallic acid derivatives. These isolated compounds will be useful in basic studies of plant physiology, food manufacturing, and biological function of C. japonica flowers.

Isolation and Identification of Antioxidants from Makgeolli

The present study was carried out to isolate and identify of antioxidants from makgeolli. Makgeolli (3 L) was filtered and the residue was extracted by MeOH. The combined filtrates and MeOH extracts were successively solvent- fractionated by n-hexane, EtOAc, and BuOH. In the antioxidative activity against DPPH and ABTS + radicals of each fraction obtained after solvent-fractionation, EtOAc and BuOH layers showed higher activities than other fractions. Therefore, the two layers were respectively purified by column chromatography and HPLC. The isolated compounds were subjected to NMR and MS analyses and identified as 4-hydroxybenzaldehyde (1, 2.0 mg), 2-(4-hydroxyphenyl)ethanol (2, tyrosol, 15.3 mg), trans- and cis-ferulic acids (3 and 4, 1.2 mg), 1H-indole-3-ethanol (5, tryptophol, 3.4 mg), dimethyl succinate (6, 14.9 mg), succinic acid (7, 7.4 mg), and mono-methyl succinate (8, 7.8 mg). The presence of 1-5 in makgeolli have never before been reported.

Difference of Starch Characteristics of Sweetpotato (Ipomoea batatas (L.) Lam) by Cultivated Regions

We investigated out the effect of cultivation region on the physicochemical characteristics of starch in six sweetpotato cultivars. The following sweetpotato cultivars were analyzed: Daeyumi, Shingeonmi, Jinhongmi, Shinyulmi, Yulmi, and Yeonhwangmi. Samples were cultivated in Muan, Iksan, Nonsan, Boryeong and Hamyang. The soil texture was found to be sandy loam in Muan, Iksan, and Boryeong, sandy clay loam in Nonsan, and loam in Hamyang. The starch content of the sweetpotato was higher in Muan than in Hamyang. The amylose content was 22.3-30.9%, and the highest amylose content was found in samples from Iksan. Rapid viscosity analysis showed that the samples from Hamyang had the lowest values of pasting temperature, while samples of the Daeyumi cultivar had the highest values. Thermal analysis with a differential scanning calorimeter showed that the Muan samples had the highest values of onset temperature, maximum peak temperature, and completion temperature, and the samples from Hamyang had the lowest values. There was no difference between the cultivation regions or the cultivar in the X-ray pattern of the starch or its appearance in scanning electron micrographs. Therefore, the results of this study confirm that cultivation region and cultivar play an important role in determining the quality of sweetpotato and the physicochemical characteristics of sweetpotato starch.

Jaboticabin and flavonoids from the ripened fruit of black rasberry ( Rubus coreanum )

The ethyl acetate (EtOAc) layer of ripened fruits of black raspberry (Rubus coreanum) had higher DPPH radical scavenging activity than was detected in other layers. Six phenolic compounds were purified and isolated from the EtOAc layer of ripened black raspberry fruits via octadecyl silane (ODS)-column chromatography and amide column-HPLC using a guided DPPH radical scavenging assay. These compounds were identified as 4-hydroxybenzoic acid (1), 2-O-(3′,4′-dihydroxybenzoyl)-4,6-dihydroxyphenylmethylacetate (2, jaboticabin), phloridzin (3), kaempferol 3-O-β-d-glucopyranoside (4), quercetin 3-O-β-d-glucuronic acid methyl ester (5), and quercetin (6), based on MS and NMR analysis. Three compounds (1, 5, and 6) had been identified previously in this plant, but other compounds (2–4) were newly isolated from this plant. Compound 2, 5, and 6 evidenced higher DPPH radical scavenging activity than α-tocopherol at the same concentration.