• Archives of Pharmacal Research
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• 제22권6호
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• pp.614-618
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• 1999

A reversed-phase high-performace liquid chromatographic method was developed to determine the optical purity of metoprolol enantiomers. The enantiomers were converted to diastereomeric derivatives using (-)-menthyl chloroformate reagent. Separation of the enantiomers as diastereomers was achieved by reversed-phase HPLC within 30 min using Inertsil C8 column. This method allowed determination of 0.05% of either enantiomer in the presence of its stereoisomer and method validation showed adequate linearity over the required range. Owing to the reaction condition during the derivatization with (-)-menthyl chloroformate, the possibility of racemization had to be established. Different ratios of (S)-(-)-metoprolol and (R)-(+)-metoprolol were prepared. Enantiomeric separation of these mixtures took place on a chiralcel OD column or, after derivatization with (-)-menthyl chloroformate, on a C8 column. The results form the these two independent separation systems were compared with trace racemization and were in very good agreement. No racemization was found during the experiment.

• 한국자기공명학회논문지
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• 제19권1호
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• pp.23-28
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• 2015

Four spiroketal sestertepenoids (1 ~ 4) were isolated from the marine sponge Haliclona species. Their planar structures were completely determined from a combination of extensive 1D and 2D NMR experiments, and also the relative stereochemistry on the chiral centers were established by the ROESY experiment. Compounds 1 ~ 3 were determined as the same planar structures with different stereochemistry on the chiral centers C-11 and C-13. Of these, 1 was identified as a new stereoisomer. Four compounds showed the inhibition effect of nitric oxide (NO) production in LPS-stimulated RAW 264.7 cells (0.7~2.0 g/ml).

• Journal of Ginseng Research
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• 제44권2호
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• pp.341-349
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• 2020

Background: The replicative senescence of human dermal fibroblasts (HDFs) is accompanied by growth arrest. In our previous study, the treatment of senescent HDFs with Rg3(S) lowered the intrinsic reactive oxygen species (ROS) levels and reversed cellular senescence by inducing peroxiredoxin-3, an antioxidant enzyme. However, the signaling pathways involved in Rg3(S)-induced senescence reversal in HDFs and the relatedness of the stereoisomer Rg3(R) in corresponding signaling pathways are not known yet. Methods: We performed senescence-associated β-galactosidase and cell cycle assays in Rg3(S)-treated senescent HDFs. The levels of ROS, adenosine triphosphate (ATP), and cyclic adenosine monophosphate (cAMP) as well as the mitochondrial DNA copy number, nicotinamide adenine dinucleotide (NAD)⁺/1,4-dihydronicotinamide adenine dinucleotide (NADH) ratio, and NAD-dependent sirtuins expression were measured and compared among young, old, and Rg3(S)-pretreated old HDFs. Major signaling pathways of phosphatidylinositol 3-kinase/Akt, 5' adenosine monophosphate-activated protein kinase (AMPK), and sirtuin 1/3, including cell cycle regulatory proteins, were examined by immunoblot analysis. Results: Ginsenoside Rg3(S) reversed the replicative senescence of HDFs by restoring the ATP level and NAD⁺/NADH ratio in downregulated senescent HDFs. Rg3(S) recovered directly the cellular levels of ROS and the NAD⁺/NADH ratio in young HDFs inactivated by rotenone. Rg3(S) mainly downregulated phosphatidylinositol 3-kinase/Akt through the inhibition of mTOR by cell cycle regulators like p53/p21 in senescent HDFs, whereas Rg3(R) did not alter the corresponding signaling pathways. Rg3(S)-activated sirtuin 3/PGC1α to stimulate mitochondrial biogenesis. Conclusion: Cellular molecular analysis suggests that Rg3(S) specifically reverses the replicative senescence of HDFs by modulating Akt-mTOR-sirtuin signaling to promote the biogenesis of mitochondria.

• 한국환경농학회지
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• 제42권3호
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• pp.203-210
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• 2023

Ferimzone Z is a fungicide for effectively controlling rice blast. Under light irradiation conditions, it undergoes a rapid conversion to its E-stereoisomer. Given the importance of isomers in risk assessments of residues in crops, an analytical method was developed for individual isomer quantification. A comparative analysis performed using two columns in HPLC-MS/MS demonstrated that the isomers were successfully separated using the Cadenza column. For the brown rice sample preparation, 5 g of the homogenized sample was saturated with 7 mL of water. The sample was then extracted with a 10 mL mixed solvent of acetonitrile and ethyl acetate (1:1, v/v) that contained 0.1% formic acid, and it was subsequently partitioned with magnesium sulfate and sodium chloride. The upper layer was purified using dSPE containing C₁₈ and PSA sorbents. The established method was subjected to method validation, and it showed recovery rates of 90.6-98.8% (RSD ≤ 3.9%) at concentrations of 0.01, 0.1, 2 mg/kg, with a soft matrix effect (%ME) ranging from -3.1% to +6.5%. This method can be employed in monitoring studies of brown rice to determine the conversion ratio from the Z isomers to the E isomers.

• Archives of Pharmacal Research
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• 제23권6호
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• pp.568-573
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• 2000

A reversed-phase high-performance liquid chromatographic method was developed to determine the optical purity of bevantolol enantiomers. (S)-(-)-Menthyl chloroformate((-)-MCF), (S)-(-)-$\alpha$-methylbenzyl isocyanate((-)-MBIC) and 2,3,4,6-tetra-O-acetyl-$\beta$-D-glucopyranosyl isothiocyanate(GITC), which can react with the secondary amine group of bevantolol were investigated as chiral derivatization reagents. Among them indirect chiral HPLC method using CITC gave the best result. The derivatization proceeded quantitatively within 20 min at room temperature. Separation of the enantiomers as diastereomers was achieved by reversed-phase HPLC within 20min using ODS column. Different ratios of (S)-(-)-bevantolol and (R)-(+)-bevantolol were prepared. Enantiomeric separation of these mixtures took place on a chiralcel OD column or, after derivatization with GITC, on a ODS column. No racemization was found during the experiment. This method allowed determination of 0.05% of either enantiomer in the presence of its stereoisomer and method validation showed adequete linearity over the required range.

• Journal of Microbiology and Biotechnology
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• 제21권6호
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• pp.582-589
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• 2011

Bioconversion of timosaponin A-III (TA-III), one of the major steroidal saponins isolated from the rhizomes of Anemarrhenae asphodeloides Bunge (Liliaceae), was investigated in Saccharomyces cerevisiae. Five bioconversion products, denoted compounds 2-6, were obtained. Biotransformation metabolite 2 was a stereoisomer of TAIII with a specific isotype F-ring and ${\beta}$-ranged $CH_3$-21, which rarely occurs in nature. The structure of 2 was elucidated by extensive spectroscopic analysis (H-H COSY, HSQC, HMBC), as well as by high-resolution mass spectral analysis. The growth inhibitory activity of compounds 1-6 was assayed against four human cancer cell lines, HepG2, H-1299, HT-29, and HCT-116. Compounds 1 and 2 obviously inhibited the growth of the four types of cancer cells with $IC_{50}$ values being less than 19${\mu}M$. A structure-activity relationship is discussed, and the spirostane-ring F in compounds 1 and 2 appears to be the critical bioactive moiety for the cell growth inhibitory property.

• Bulletin of the Korean Chemical Society
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• 제35권5호
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• pp.1323-1328
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• 2014

Molecular structures of the various conformational stereoisomers of 2,8,14,20-cyanophenyl pyrogallol[4]arenes 1 were optimized using the mPW1PW91 (hybrid Hartree-Fock density functional) calculation method. The total electronic and Gibbs free energies and the normal vibrational frequencies of the different structures from three major conformations (CHAIR, TABLE, and 1,2-Alternate) of the four stereoisomers [1(rccc), 1(rcct), 1(rctt), and 1(rtct)] were analyzed. The mPW1PW91/6-31G(d,p) calculations suggested that $1(rcct)_{1,2-A}$, 1(rctt)CHAIR, and $1(rtct)_{CHAIR}$ were the more stable conformations of the respective stereoisomers. Hydrogen bonding is the primary factor for the relative stabilities of the various conformational isomers, and maximizing the ${\pi}-{\pi}$ interaction between the cyanophenyl rings is the secondary factor. The calculated IR spectra of the more stable conformers [$1(rctt)_{CHAIR}$, $1(rcct)_{1,2-A}$, $1(rtct)_{CHAIR}$] were compared with the experimental IR spectrum of $1(rtct)_{CHAIR}$.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2001년도 추계학술발표대회
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• pp.666-670
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• 2001

Levofloxacin은 ofloxacin의 L형의 광학이성질체로 D형의 ofloxacin보다 뛰어난 향균활성을 갖는다. 본 연구에서는 광학선택성을 지닌 외래 효소를 재조합균주에서 발현시키고 고농도배양과 세포고정화를 통해 levofloxacin을 생산하였다. E. coli 고농도 배양을 수행하여 89 g/L의 세포농도를 얻었으며 IPTG 1 mM로 단백질 발현을 유도하여 levofloxacin 생산 반응에 사용할 때 최적 첨가시기를 결정하였다. 세포고정화를 위해서는 sodium alginate를 사용하였으며 1.5% 첨가시 가장 우수한 효소활성을 나타내었고 재사용시에도 효소활성과 광학선택성이 유지됨올 확인하였다.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2001년도 추계학술발표대회
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• pp.652-655
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• 2001

The comparative study of enzymes that catalyze a similar reactions but have different substrate spectrum and/or stereospecificity is a powerful approach to understanding the reaction mechanism between the relative enzymes, and it was also an useful tool to cloning the related enzyme, without the typical cloning from DNA library of genomic pools. For this purpose, we conducted an approach that the comparison at the molecular and protein level of esterases, from various sources including a previously identified (S)-stereospecific esterase of Pseudomonas sp. ES1. As expected, we found an esterase family genes that shared a high similarity at the protein and genetic level in the identical genus Pseudomonad. The striking structural and biochemical identity strongly suggested the family genes to be an identical one. We, hence, aligned the family genes and designated a degenerated primer for PCR-cloning using six Pseudomonas strains as templates. As a result, a recombinant esterase from Pseudomonas fluorescens KCTC 1767 was cloned and high-level expressed with high selectivity to (R,S)-ketoprofen ethyl ester. The enzyme exhibited a high ester-hydrolyzing activity to (S)-ketoprofen but did not hydrolyzed the opposite stereoisomer. Further characteristics were discussed in our presentation.

• Applied Biological Chemistry
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• 제46권2호
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• pp.150-153
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• 2003

비목나무 잎의 메탄올 추출물을 n-hexane, ethylacetate, n-butanol, $H_2O$으로 순차적으로 용매분획하였다. Ethylacetate 분획으로부터 silica gel chromatography를 반복하고 재결정하여 활성물질을 분리 정제하였다. 화합물은 NMR과 MS의 기기분석 결과 methyllucidone의 입체이성질체 혼합물로 구조결정 되었다. 이 혼합물은 밀 붉은녹병에 대하여 $50\;{\mu}g/ml$에서 85%의 방제효과를 나타내었다.