• Korean Journal of Pharmacognosy
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• v.24 no.1
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• pp.54-57
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• 1993

The seasonal variations of five biflavones from Ginkgo biloba leaves from May to November were investigated by a reversed phase HPLC method. The total amount of biflavones was increased with time to reach its maximum in yellow autumnal leaves. Each biflavone showed a similar tendency. It increased rapidly about 3.1-fold from May to June and thereafter gradually increased about 2.5-fold. The ratio of each biflavone content to the total amount of biflavones was in the order of as follows: isoginkgetin>sciadopitysin>bilobetin>ginkgetin>amentoflavone.

• Natural Product Sciences
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• v.9 no.2
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• pp.45-48
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• 2003

The content of chiisanoside in the Acanthopanax Species was determined by reversed-phase high performance liquid chromatographic method. Chiisanoside was separated from the other components in the plant extracts using Zorbax 300 SB $C_{18}$ column with gradient elution of acetonitrile. Identification of chiisanoside was carried out by comparison in the LC/MS spectrum of separated peak from extract with that of standard. By HPLC analysis in this experiment, Acanthopanax species could be classified into two groups based upon the content of chiisanoside-one with low concentration of chiisanoside, such as A. senticosus and A. koreanum, and another with high concentration of chiisanoside, such as A. senticosus f. inermis, A. Divaricatus var. albeofructus, and A. chiisanensis.

• Natural Product Sciences
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• v.14 no.1
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• pp.68-72
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• 2008

A simple reversed phase HPLC method was developed for extracting pharmacologically active compounds coptisine, palmatine, berberine, and epiberberine from the roots of Coptis chinensis using a binary gradient of acetonitrile : 10 mM hexanesulfonic acid-Na monohydrate with UV detection at 254 nm. The coptisine (1), palmatine (2), berberine (3), and epiberberine (4) contents of the roots of C. chinensis collected from sixteen district markets in Korea and China were $6.79\;{\sim}\;24.63\;{\mu}g/g$, $5.40\;{\sim}\;20.75\;{\mu}g/g$, $21.40\;{\sim}\;81.21\;{\mu}g/g$, and $3.45\;{\sim}\;12.04\;{\mu}g/g$, respectively.

• Preventive Nutrition and Food Science
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• v.9 no.4
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• pp.295-299
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• 2004

Alpha-tocopherol was thermally oxidized and degraded at high temperatures and the resulting products were chromatographically separated and identified by LC-MS. Alpha-tocopherol dissolved in glycerol was heated at 200^{\circ}C for 30 min. The thermal products were separated by hexane extraction and analyzed by HPLC using a reversed phase $\mu$-Bondapak $C_{18}-column$ with two kinds of elution solvents: a mixture of acetonitrile and methanol (3:2), and of acetonitrile, methanol, 2-propanol, chloroform and methylene chloride (3:2:5:0.5:0.5) in a gradient mode. The isolated thermal. products of alpha-tocopherol were more viscous than alpha-tocopherol, and dark brown in color. Major thermal degradation products of alpha-tocopherol were identified by LC-MS, and the structures of thermal products were proposed. Alpha-tocopherol and its thermal degradation products were degraded into fragments, mainly at the non-aromatic parts. The degradation products of alpha-tocopherol. were combined with oxidized product (tocopherylquinone) to make thermal. products through dimerization.

• Journal of Pharmaceutical Investigation
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• v.25 no.3
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• pp.239-247
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• 1995

The physico-chemical stability of aucubin, a hepatoprotective iridoid glucoside, in buffered aqueous solutions was studied using a stability-indicating reversed-phase high performance liquid chromatography. The degradation of aucubin followed the pseudo-first-order kinetics. In strong acidic regions, aucubin was rapidly degraded by the specific acid catalysis, forming dark brown precipitates. From the rate-pH profiles, it was found that aucubin was most stable at the pH of about 10. From the temperature dependence of degradation, activation energies for aucubin at pH 2.1 and 4.9 were calculated to be 22.0 and 24.3 kcal/mole, respectively. The shelf-life $(t_{90%})$ for aucubin at pH 9.07 and $20^{\circ}C$ was predicted to be about 603 days. A higher ionic strength accelerated the degradation of aucubin at pH 4.01. The effect of metal ions on the degradation rate of aucubin at pH 7.16 was in the rank order of $Cu^{2+}\;>\;Fe^{3+}\;>\;Co^{2+}\;>\;Fe^{2+}\;>\;Mg^{2+}$. On the other hand, $Mn^{2+}\;and\;Ba^{2+}$ slowed the degradation rate.

• Preventive Nutrition and Food Science
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• v.8 no.4
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• pp.301-305
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• 2003

This study was conducted to develop an HPLC method for determining vitamin B$_{12}$ in fortified foods which has typically been determined by microbiological assays according to AOAC and Korean Food Code approved methods. Vitamin B$_{12}$ (cyanocobalamin) was determined by reversed-phase HPLC with a triple column and UV/VIS dectector (550 nm) using the column switching technique after extraction with 5 mM potassium phosphate solution by sonication without a clean-up procedure. The recovery of spiked samples and limit of detection (LOD) by HPLC were 78.6 ∼107.5 % and 2 ppb ($\mu\textrm{g}$/kg), respectively. The LOD of the microbiological assay (MBA) was much lower than that of HPLC. The concentrations of vitamin B$_{12}$ analyzed in all tested samples (n=12) confirmed compliance with declared label claims. The range of recovery ratio by the HPLC method when compared to the microbiological assay was 76.2 ∼140.0 %. There was not significant difference between the HPLC and MBA methods (p < 0.01) with r=0.9791 and linear regression y=0.9923x-0.04. The HPLC method for determining vitamin B$_{12}$ using the column-switching technique appears to be suitable for determining vitamin B$_{12}$ concentrations above 1 $\mu\textrm{g}$/100 g in fortified foods.ied foods.

• Applied Chemistry for Engineering
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• v.17 no.3
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• pp.317-320
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• 2006

The optimum mobile phase condition for analysis of the six purine derivatives (caffeine, guanine, hypoxanthine, purine, theobromine, and theophylline) were determined by a HCI program. Reversed-phase HPLC system was used with the binary mobile phase, water and methanol. Three retention models (Snyder, Langmuir, and Binary polynomial) were considered to predict the retention factors. The elution profiles were calculated by the plate theory based on the binary polynomial retention model. From the final calculated results, the binary polynomial retention model showed the best agreements between the calculated and experimental data. In the isocratic mode, the optimum mobile phase composition of water/methanol is 93/7(v/v). However, we used step-gradient mode to decrease the run-time ($1^{st}$ mobile phase : water/methanol = 93/7 (v/v), gradient time : 5 min, $2^{nd}$ mobile phase : water/methanol = 75/25 (v/v)). The experimental and simulated profiles of above the two conditions show a good agreement.

• Bulletin of the Korean Chemical Society
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• v.29 no.3
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• pp.609-614
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• 2008

A periodic mesoporous organosilica material was synthesized by microwave heating (PMO-M) using 1,2-bis(trimethoxysilyl)ethane as a precursor in a cationic surfactant solution, and textural properties were compared with those of the product produced by conventional convection heating (PMO-C). These synthesized materials were characterized using XRD, TEM/SEM, N2 adsorption isotherm, 29Si and 13C NMR, and TGA, which confirmed their good structural orders and clear arrangements of uniform 3D-channels. Synthesis time was reduced from 21 h in PMO-C to 2-4 h in PMO-M. PMO-M was made of spherical particles of 1.5-2.2 m m size, whereas PMO-C was made of decaoctahedron-shaped particles of ca. 8.0 m m size. Effect of synthesis temperature, time, and heating mode on the PMO particle morphology was examined. The particle size of PMO-M could be controlled by changing the heating rate by adjusting microwave power level. PMO-M demonstrated improved separation of selected organic compounds compared to PMO-C in a reversed phase HPLC experiment. Ti-grafted PMO-M also resulted in higher conversion in liquid phase cyclohexene epoxidation than by Ti-PMO-C.

• Journal of Korean Society for Atmospheric Environment
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• v.7 no.1
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• pp.1-16
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• 1991

In this study, sampling and analytical procedures were evaluated for the determination of ambient levels of atmospheric PAH, both in gaseous and particulate phase. The method involves low-volume sampling and Soxhlet extraction of the filters and Tenax absorbent, followed by a clean-up stage using a silica column prior to analysis by reversed-phase HPLC with wavelength programmable fluorescence and UV detection. A total of 18 PAH were identified and quantified, all of which have been of environmental concern. In order to validate the methodology and to ensure compatibility of the results, the analytical method used for the determination of PAH was evaluated with respect to the efficiencies of extraction and clean-up procedure, HPLC separation, and lower limits of detection. In addition, substrate dependency of PAH recovery was investigated for the two types of fiters, i.e. glass fiber and PTFE filters.

• Korean Journal of Pharmacognosy
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• v.34 no.3 s.134
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• pp.201-205
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• 2003

This paper is intended as an investigation of the analysis of high-performance liquid chromatography and the method of extraction of decursin and decursinol angelate in Angelica gigas roots. There are three kinds of extraction methods: distilled water, 50% EtOH and 100% EtOH. The condition of HPLC was obtained on a reversed-phase column $(Polarity\;dC_{18},\;4.6{\times}250 mm,\;5\;{\mu}m)$ using a phosphate buffer-acetonitrile-sodium lauryl sulfate as the mobile phase. Under these chromatographic conditions, UV detector was 230 nm, column temperature $30^{\circ}C$ and the speed of a current 1.0 ml/min, respectively. The results of extraction with distilled water, 50% EtOH and 100% EtOH in Angelica gigas roots were as follows. The concentrations of decursin and decursinol angelate were 182 and 153 ppm (distilled water), 3,142 and 2,547 ppm (50% EtOH) and 3,341 and 2,778 ppm (100% EtOH). There were high positive correlations between the concentrations of decursin and EtOH (r=0.8928, p<0.01) and decursinol angelate and EtOH (r=0.9009, p<0.01).