• Analytical Science and Technology
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• v.11 no.5
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• pp.404-408
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• 1998

Using a reversed-phase high performance liquid chromatography, the separation of 20(S)-, 20(R)-prosapogenin stereo-isomers of ginsenoside-$Rg_2$ and of ginsenoside-$Rg_3$ in ginseng saponins has been carried out with binary solvent system. The optimum conditions for the isomer separation are as following: Nova-$Pak^{(R)}C_{18}$ (Waters, $3.9{\times}150mm$) column, $CH_3CN/CH_3CN$ (100:8, v/v) binary solvent system and the flow rate was 1.7 mL/min. The stereoisomers were separated with change of the mixture ratio of the solvent system, the solvent elution by gradient program, and then detected at 203 nm of UV detector. The simultaneous separation of mixture that were the $Rg_2$, $Rg_3$ isomers was easily performed in nonpolar solvent for $Rg_2$, polar solvent for $Rg_3$ at the same optimum conditions.

• Environmental Analysis Health and Toxicology
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• v.19 no.2
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• pp.183-189
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• 2004

To obtain the residual organochlorine pesticides in the culture environment of ginseng on Sangju, Gyeongbuk, the analytical methods for BHC isomers, Aldrin, DDE, Dieldrin, DDD, Endrin and DDT by GCECD are surveyed. The relative retention times for $\alpha$-BHC, $\beta$-BHC, ${\gamma}$-BHC, $\delta$-BHC, Aldrin, DDE, Dieldrin, DDD, Endrin and DDT were 1.000, 1.042, 1.049, 1.086, 1.202, 1.335, 1.341, 1.371, 1.391 and 1.439, respectively The BHC isomers, Aldrin, DDE, Dieldrin, DDD, Endrin and DDT were separated on the base line. The qualified detection concentration for $\alpha$-BHC, $\beta$-BHC, ${\gamma}$-BHC and $\delta$-BHC is 0.43, 1.33, 0.54 and 1.63 ng/g and it's of Aldrin, DDE, Dieldrin, DDD, Endrin and DDT were 0.63, 0.50, 0.66, 0.74, 0.96 and 0.88ng/g, respectively. BHC isomers, Aldrin, DDE, Dieldrin, DDD, Endrin and DDT were not detected in culture environment of ginseng on Sanaju, Gyeongbuk. The detection concentration for Hg, Cd, Pb, Cr, and As in ginseng were 0.0086ppm, 0.0020ppm, 0.0200ppm, 0.0271ppm and 0.0220ppm, respectively, which were also lower than the 30ppm Korea Food & Drug Administration advisory level for heavy metal in herbal medicines.

• YAKHAK HOEJI
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• v.41 no.3
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• pp.277-282
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• 1997

Methamphetamine, which is the most commonly abused drug in Korea, exists in terms of d-, l- isomers and a racemate(dl). d-Methamphetamine is a potent central nervous system stimulant, whereas l-Methamphetamine is sold freely as a nasal decongestant. In addition, methamphetamine appears in different ratios of optical isomers by the clandestine synthesis applied. In this study, enetiomeric separation of methamphetamines was estabilished to distinguish the chirality of methamphetamines trafficked and abused in Korea. A gas chromatograph/mass spectrometer(GC/MS) system equipped with an achiral capillary column is used to isolate the isomers of methamphetamine after (S)-N-(trifluoroacetyl)-l-prolyl(TFP) deravatization.After analyzing 10 illicit methamphetamine powders and 10 positive urine samples, following findings were found: d-Methamphetamine was well resolved from l-Methamphetamine by chromatographic separation of TFP derivatibes on DB-5 with retention time of 11.80 and 11.35 min respectively. The detection of d-Methamphetamine in all 10 powders and 10 urine samples proves that all methamphetamines abused in Korea are illegally manyfactured and administred.

• Mass Spectrometry Letters
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• v.2 no.1
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• pp.24-27
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• 2011

Hyperthermal ion/surface collisions of bromotoluene radical cations were studied using perfluorinated (F-SAM) and hydroxyl-terminated (OH-SAM) self-assembled monolayer surfaces in a tandem mass spectrometer with BEEQ geometry. The isomers were differentiated by ion abundance ratios taken from surface-induced dissociation (SID). The dissociation rate followed the order of ortho > meta > para isomers. The peak abundance ratio of m/z 51 to m/z 65 showed the best result to discern the isomers. A dissociation channel leading to tolylium ion was suggested to be responsible for the pronounced isomeric differences. The capability of SID to provide high-energy activation with narrow internal energy distribution may have channeled the reaction into the specific dissociation pathway, also facilitating small differences in reaction rates to be effective in the spectral time window of this experiment. All of the molecular ions experiencing reactive collisions with the F-SAM surface undergo transhalogenation, in which a fluorine atom on the surface replaces the bromine in the incoming ions. This reactive collision was dependent on the laboratory collision energy occurring in ca. 40.75 eV range.

• Korean journal of food and cookery science
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• v.19 no.1
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• pp.83-95
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• 2003

Investigations were conducted on the changes in carotenoids content, and quantification of cis-trans-${\beta}$-carotene Isomers in pureed and cooked carrot and spinach during storage. The isomerization and degradation of carotenoids were monitored by high-performance liquid chromatography on a C$\_$30/ reversed-phase column with diode-array detection. The results showed that lutein, ail-trans-${\beta}$-carotene, ${\alpha}$-carotene, 9-cis-${\beta}$-carotene and 13-cis-${\beta}$-carotene were present in carrot and spinach. Zeaxanthin and cryptoxanthin were present in raw spinach. The contents of lutein, zeaxanthin, cryptoxanthin, ${\alpha}$-carotene and all-trans-${\beta}$-carotene in pureed and cooked carrot and spinach decreased with increasing storage period. The 9-cis and 13-cis carotenoid isomers were the major types formed in cooked carrot during storage. Cooking was not found to alter the carotenoid profile of the sample, but increased the total amount of carotenoids compared with pured ones. This increase could be explained that cooking itself increased the extraction efficiency and inactivated the enzymes degradating carotenoids.

• YAKHAK HOEJI
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• v.41 no.6
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• pp.698-703
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• 1997

Recently, l-deprenyl (selegiline), a relative new antiparkinson`s drug, has been marketed in Korea. As its metabolites, l-methamphetamine and l-amphetamine, are the enantiomers of illicit drugs,d-methamphetamine and d-amphetamine, a method for analysis of enantiomers of methamphetamine and amphetamine in rat urine was investigated. The optical isomers of methamphetamine and amphetamine were analyzed with the chiral derivatizing reagent (S)-(-)-N-(trifluoroacetyl)-prolyl chloride (l-TFP), which was used to form the diastereomers of methamphetamine and amphetamine. And all diastereomers (l-TFP -l-AM, lTFP-d-AM, l-TFP-l-MA & l-TFP-d-MA) were well resolved by capillary gas chromatography. After administration of 10mg/kg l-deprenyl to rat, l-methamphetamine and l-amphetamine were detected without autoracemization to the d form in all urine samples collected during 24hrs, and the ratios of l-amphetamine/l-methamphetamine were 1.1~3.3. l-Amphetamine was detected in only 3 out of 8 urine samples collected during 24~48hrs where as no l-methamphetamine was detected in all cases.

• Korean Journal of Plant Resources
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• v.21 no.6
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• pp.435-439
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• 2008

Due to the fact that tocopherols and tocotrienols have antioxidant and anticancer properties, the commercial utilization of unsaponifiable fractions in rice bran is increasing. These nutraceutical compounds, however, are fairly unstable and readily break down when exposed to oxygen or lighting conditions. To compare the relative sensitivity of vit E isomers to heat and oxygen, concentrated unsaponifiable fractions extracted from crude rice bran oil were exposed to various temperature, oxygen (nitrogen-balanced), and bathing solvent conditions and resultant concentration changes in ${\alpha}$- and ${\gamma}$-tocopherols (T) and tocotrienols (T3) were evaluated. Each isomer exhibited different heat stability. Among them, ${\alpha}$-T3 degraded more rapidly compared to other vit E isomers while ${\alpha}$-T was the most stable isomer. Oxygen level also showed significant impact on each isomer's stability where severe reductions of ${\gamma}$-T (by 20%) and ${\gamma}$-T3 (by 29%) were observed under 2% oxygen conditions, while under 0% oxygen conditions no degradation could be observed even after exposure to $95^{\circ}C$ for 4 hours. When various blending solvents were mixed with concentrated unsaponifiable fractions, organic solvents such as isooctane and hexane were more effective in maintaining the stability of ${\gamma}$- T3 compared to edible oils, among which com oil was more efficient than soybean and rice bran oils.

• Journal of Nutrition and Health
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• v.34 no.8
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• pp.896-904
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• 2001

Conjugated linoleic acid(CLA) is a group of positional and geometric isomers of linoleic acid(LA) and exhibits anticarcinogenic activity in multiple experimental animal models. Cis-9,trns-11(c9t11) and trans-10,cis-12(t10c12) CLA are the principal isomers found in foods. The present study was performed to determine whether CLA and the two isomers inhibits HT-29 cell proliferation and to assess whether such an effect was related to changes in secretion of eicosanoids. Cells were incubated in serum-free medium with various concentrations(0 to 20$\mu$M) of CLA or LA. CLA inhibited cell proliferation in a dose-dependent manner, with maximal inhibition(70 $\pm$ 1%) observed at 20$\mu$M concentration after 96 hours. However, LA had no effect at the same concentration range. To compare the ability of c9f11 and t10c12 to inhibit cell proliferation, cells were incubated with increasing concentrations(0 to 4$\mu$M) of these isomers. T10c12 inhibited cell proliferation in a dose-dependent manner. A 66 $\pm$ 2% decrease in cell number was observed within 96 hours after addition of 4$\mu$M t10c12. By contrast, c9t11 had no effect. The concentrations of CLA and the two isomers in the plasma membrane were increased when they were added to the incubation medium. However, they did not alter the levels of arachidonic acid in plasma membrane. To assess whether the proliferation inhibiting effect of CLA was related to changes in eicosanoid production, prostaglandin E$_2$(PGE$_2$) and leukotriene B$_4$(LTB$_4$) concentrations in conditioned media were estimated by a competitive enzyme immunoassay. Both CLA and t10c12 increased the production of materials reactive to PGE$_2$ and LTB$_4$ antibodies in a dose-dependent manner. By contrast, c9t11 had no effect. These results indicate that inhibition of HT-29 cell proliferation by CLA is attributed to the effect of the t10v12 isomer. The materials reactive to PGE$_2$ and LTB$_4$ antibodies may inhibit growth stimulatory effect of arachidonic acid-derived eicosanoids on HT-29 cell proliferation.

• Journal of Photoscience
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• v.9 no.2
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• pp.344-346
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• 2002

Eight intact bacteriochlorophyll (BChl)-d homologs and isomers were isolated from a strain of green sulfur bacterium Chlorobium vibrioforme. All the molecular structures of the BChl-d components were fully determined by a combination of mass spectrometry and $^1$H-NMR spectroscopy. The aggregation behavior of the isomerically pure BChls-d in hydrophobic organic solvents was examined with respect to the stereoisomeric configuration at the C3$^1$ position as well as the bulkiness of the C8 and C12 side-chains by using electronic- absorption spectroscopy.

• Journal of the Korean Society of Tobacco Science
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• v.9 no.1
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• pp.57-64
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• 1987

The pyrolysis of geometrical isomers of 9-octadecenoic acid were conducted at $600^{\circ}C$ under nitrogen, and its pyrolytic behaviors were investigated. The pyrolytic products of both fatty acids, cis-9-octadecenoic acid(oleic acid) and trans-9-octadecenoic acid(elaidic acid), were analyzed using a gas chromatograph and GC/MS spectrometer. Twenty-seven different compounds were identified from these pyrolyzates, and the chief products of them were ketones, alcohols and aromatic hydrocarbons. And also, the pyrolytic mechanisms of two geometrical isomers of this fatty acid were discussed by a comparison of experimental results.