Wol-Soo Kim

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.

Change in chemical constituents and free radical-scavenging activity during Pear (Pyrus pyrifolia) cultivar fruit development

Changes in chemical constituent contents and DPPH radical-scavenging activity in fruits of pear (Pyrus pyrifolia) cultivars during the development were investigated. The fruits of seven cultivars (cv. Niitaka, Chuhwangbae, Wonhwang, Hwangkeumbae, Hwasan, Manpungbae, and Imamuraaki) were collected at 15-day intervals after day 20 of florescence. Vitamins (ascorbic acid and α-tocopherol), arbutin, chlorogenic acid, malaxinic acid, total caffeic acid, total flavonoids, and total phenolics were the highest in immature pear fruit on day 20 after florescence among samples at different growth stages. All of these compounds decreased gradually in the fruit during the development. Immature pear fruit on day 35 or 50 after florescence exhibited higher free radical-scavenging activity than that at other times, although activities were slightly different among cultivars. The chemical constituent contents and free radical-scavenging activity were largely different among immature fruits of the pear cultivars, but small differences were observed when they matured. Graphical Abstract The contents of total phenolics and main phenolic compounds gradually decreased during the development of pear fruit.

An ether and three ester derivatives of phenylpropanoid from pear ( Pyrus pyrifolia Nakai cv. Chuhwangbae) fruit and their radical-scavenging activity

The ethyl acetate-acidic layer obtained after solvent fractionation of Asian pear (Pyrus pyrifolia Nakai cv. Chuhwangbae) fruit peel methanol extracts was purified by Sephadex LH-20 column chromatography and octadecylsilane-high performance liquid chromatography, and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity was evaluated. The four isolated compounds were identified as 2-O-(trans-p-coumaroyl) glyceric acid (1), 2-O-(cis-p-coumaroyl) glyceric acid (2), guaiacylglycerol-β-ferulic acid ether (3), and 2-O-(cis-caffeoyl) malic acid (4), based on the one- and two-dimensional nuclear magnetic resonance spectroscopic data. The isolated compounds 1–4 were identified for the first time from pear. Compound 4 showed higher DPPH radical-scavenging activity than 1–3.

Isolation and Identification of 3 Low-molecular Compounds from Pear (Pyrus pyrifolia Nakai cv. Chuhwangbae) Fruit Peel

Three low-molecular compounds were isolated from methanol extracts of pear (Pyrus pyrifolia N. cv. Chuhwangbae) fruit peels using solvent fractionation, various types of column chromatogrphy (Diaion HP-20, Sephadex LH-20, and silica gel), and high performance liquid chromatography with an assay guided by 1,1-diphenyl-2-picrylhydrazyl radical-scavenging activity. The isolated compounds were identified as 2-carboxyl-4(1H)-quinolinone (kynurenic acid, 1) from butanol fraction, cis-p-coumaric acid (2) from ethyl acetate-acidic fraction, and vanillin (3) from the ethyl acetate-phenolic fraction, respectively. These isolated compounds were confirmed on the basis of the spectroscopic data of electrospray ionization mass spectrometry and nuclear magnetic resonance. This is the first time that compounds 1-3 were isolated and identified in pear.

Optical absorption spectra of undoped and Co-doped Cd4GeSe6 single crystals

The ternary semiconducting compounds of A4BX 6 type ( A = C d , Hg, B = S i , Ge and X = S , Se) exhibit high photosensitivity and strong luminescence in the visible and near-infrared regions [1-4]. These desirable properties make the compounds promising optoelectronic materials. However, not many studies have been made on these compounds because of considerable difficulties in obtaining homogeneous and stoichiometric crystals. Among the few studies undertaken, some attention has been paid to crystal growth [5], photoconductivity [2, 4] and photoluminescence [3] of CdeSiS 6 and Cd4GeSe6. Quenez and Gorochov [6] have reported on the crystal growth of Cd4GeSe6 by the chemical transport technique using iodine, bromide and chlorine as transporting agents. In earlier work [7], the authors have investigated photoluminescence spectra of Cd4GeSe6 crystals. However, the temperature dependence of the optical energy gap in the CdeGeSe6 compound has not been investigated to date. No study of the optical properties of transition metal impurities in this compound has been made. The purpose of the present letter is to report on the temperature dependence of the optical energy gaps of undoped and Co-doped Cd4GeSe6 single crystals grown by the chemical transport technique. The effects of the doping of the cobalt transition metal impurity on the optical absorption of this compound are also studied. Single crystals of Cd4GeSe 6 and Cd4GeSe6:Co (2 mol %) were grown by the chemical transport technique using iodine as a transporting agent. The starting materials were powders of polycrystalline Cd4GeSe 6 and Cd4GeSe6:Co [7] prepared by reacting stoichiometric quantities of cadmium (99.9999% purity), germanium (99.9999% purity), selenium (99.9999% purity) and cobalt (99.99% purity) in an evacuated quartz ampoule using a rotating horizontal furnace. The amount of iodine was 5 mg per cm 3 ampoule volume. The charged ampoule was evacuated to 2 x 10 -6 mmHg and the sealed ampoule was placed in a two-zone furnace with the source zone temperature 580 °C and the growth zone

Comparison of bioactive compound contents and in vitro and ex vivo antioxidative activities between peel and flesh of pear (Pyrus pyrifolia Nakai)

We compared chemical constituents and antioxidative activities between the flesh and peel of two Asian pears (Pyrus pyrifolia Nakai cv. Niitaka and Chuhwangbae). Total phenolic, flavonoid, and ascorbic acid contents in the peels were higher than those in the flesh. However, total tocopherol content between peels and flesh was not different. The peels exhibited higher free radical scavenging activities in the in vitro models of DPPH, ABTS+, nitrite radicals, and reducing capabilities than those of the flesh. Pear fruit extracts significantly prevented 3T3-L1 cells from undergoing H2O2-induced oxidation and the effect was higher by the peel extract than by the flesh extract. In addition, blood plasma of rats administered the peel extract showed higher antioxidative activity than that of rats administered the flesh extract. These results suggest that consumption of unpeeled Asian pear fruit may effectively increase antioxidant activity in the body.

Isolation and Identification of a Sterol and Three Glucosides from the Peel of Pear (Pyrus pyrifolia Nakai cv. Chuhwangbae)

We isolated and identified antioxidants from acidic and neutral ethyl acetate fractions of the peel of pear (Pyrus pyrifolia N. cv. Chuhwangbae). We isolated 4 compounds from the methanol extract, by using 3 different types of column chromatography (Sephadex LH-20, silica gel, and octadecylsilane) and preparative HPLC. We identified the isolated compounds as (S)-(+)-2-cis-abscisic acid O-β-D-glucopyranosyl ester (compound 1), 1-(4-O-β-D-glucopyranosyl)phenyl ethanone (picroside, compound 2), β-sitosterol (compound 3), and β-sitosteryl 3-O-β-D-glucopyranoside (compound 4) by nuclear magnetic resonance analysis. We are the first to report the identification of compounds 1, 2, and 4 from pear.

Photoluminescence spectra of Er3+-doped MgAl2S4 and CaAl2S4 single crystals

MgAl2S4, CaAl2S4, MgAl2S4:Er3+ and CaAl2S4:Er3+ single crystals were grown by the chemical transport reaction method. The single crystals crystallized in an orthorhombic structure. The single crystals had the direct energy band structure and their optical energy gaps were 4.334 eV, 4.213 eV, 4.835 eV and 4.716 eV for the MgAl2S4, MgAl2S4:Er3+, CaAl2S4, and CaAl2S4:Er3+ single crystals, respectively, at 13 K. Sharp emission peaks appeared in the MgAl2S4:Er3+ and CaAl2S4:Er3+ single crystals, and they were interpreted to originate from the Er3+ ion substituted Mg2+ and Ca2+ ions in the MgAl2S4:Er3+ and CaAl2S4:Er3+ single crystals.