Sang Un Choi

Korea Research Institute of Chemical Technology, Daiden, Daejeon, South Korea

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Publications (115)203.01 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: As a part of an ongoing search for bioactive constituents from Korean medicinal plants, the phytochemical investigations of the twigs of Salix glandulosa afforded 12 new phenolic glycosides (1-12) and a known analogue (13). The structures of 1-13 were characterized by a combination of NMR methods ((1)H and (13)C NMR, (1)H-(1)H COSY, HMQC, and HMBC), chemical hydrolysis, and GC/MS. The absolute configuration of 13 [(1R,2S)-2-hydroxycyclohexyl-2'-O-trans-p-coumaroyl-β-d-glucopyranoside] was determined for the first time. Compounds 1-3, 6, and 7 exhibited inhibitory effects on nitric oxide production in lipopolysaccharide-activated murine microglial cells (IC50 values in the range 6.6-20.5 μM).
    Journal of natural products. 08/2014;
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    ABSTRACT: In the search for antitumor compounds from Korean natural resources, activity-guided fractionation and purification processes were used on seeds of Morning glory (Pharbitis nil). Air-dried P. nil seeds were extracted with ethanol and separated into n-hexane, chloroform, ethyl acetate, and n-butanol. Four new lignans, pharbilignans A-D (1-4) were isolated from the most active ethyl acetate fraction of the ethanol extract. Their structures were characterized on the basis of spectroscopic methods, including one- and two-dimensional nuclear magnetic resonance (NMR) techniques, high resolution mass spectrometry (HRMS), and circular dichroism (CD) spectroscopy. The cytotoxic activities of the isolates (1-4) were evaluated by determining their inhibitory effects on four human tumor cell lines (A549, SK-OV-3, SK-MEL-2, and HCT15) using a sulforhodamine B (SRB) bioassay. Pharbilignan C (3) showed potent cytotoxicity against A549, SK-OV-3, SK-MEL-2, and HCT-15 cell lines with IC50 values of 1.42, 0.16, 0.20, and 0.14 μM, respectively. On the basis of the expanded understanding that inflammation is a crucial cause in tumor progress, we also evaluated anti-inflammatory activity of the isolates (1-4). Pharbilignan C (3) strongly inhibited nitric oxide (NO) production in lipopolysaccharide (LPS)-activated BV-2 microglia cell line with an IC50 value of 12.8 μM.
    Journal of agricultural and food chemistry. 07/2014;
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    ABSTRACT: Two new spirostane-steroidal saponins, bletilnoside A (1) and bletilnoside B (2), together with five known compounds, 3–7, were isolated from the roots of Bletilla striata (Thunb.) Reichb. F. The structures of the new compounds were determined based on their 1D- and 2D-NMR spectral data. The isolated compounds 1–7 were tested for cytotoxicity against four human tumor cells (A549, SK-OV-3, SK-MEL-2, and HCT15) in vitro using a sulforhodamin B bioassay, and compounds 1, 2, and 5 showed significant cytotoxicities against all tested tumor cell lines with IC50 values ranging from 3.98±0.16 to 12.10±0.40 μM.
    Helvetica Chimica Acta 01/2014; 97(1). · 1.38 Impact Factor
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    ABSTRACT: Raphanus sativus seeds (Brassicaceae) known as Raphani Semen have long been used as anti-cancer and/or anti-inflammatory agents in Korean traditional medicine. This study was designed to isolate the bioactive constituents from the seed extracts of Raphanus sativus and evaluate their anti-inflammatory and antitumor activities. Bioassay-guided fractionation and chemical investigation of a methanolic extract of the seeds of Raphanus sativus led to the isolation and identification of seven 4-methylthio-butanyl derivatives. Structural elucidation of the isolated compounds was carried out using 1D and 2D nuclear magnetic resonance (NMR) spectroscopy techniques ((1)H, (13)C, COSY, HMQC and HMBC experiments) and mass spectrometry. The isolated compounds were characterized as in the following: three new 4-methylthio-butanyl derivatives, sinapoyl desulfoglucoraphenin (1), (E)-5-(methylsulfinyl)pent-4-enoxylimidic acid methyl ester (2), and (S)-5-((methylsulfinyl)methyl)pyrrolidine-2-thione (3), together with four known compounds, 5-(methylsulfinyl)-4-pentenenitrile (4), 5-(methylsulfinyl)-pentanenitrile (5), sulforaphene (6), and sulforaphane (7). Full NMR data assignments of the three known compounds 4-6 were also reported for the first time. We evaluated the anti-neuroinflammatory effect of 1-7 in lipopolysaccharide-stimulated murine microglia BV2 cells. Compound 1 significantly inhibited nitrite oxide production with IC50 values of 45.36μM. Moreover, it also reduced the protein expression of inducible nitric oxide synthase. All isolates were also evaluated for their antiproliferative activities against four human tumor cell lines (A549, SK-OV-3, SK-MEL-2, and HCT-15), and all of them showed antiproliferative activity against the HCT-15 cell, with IC50 values of 8.49-23.97μM. 4-Methylthio-butanyl derivatives were one of the main compositions of Raphanus sativus seeds, and activities demonstrated by the isolated compounds support the ethnopharmacological use of Raphanus sativus seeds (Brassicaceae) as anti-cancer and/or anti-inflammatory agents.
    Journal of ethnopharmacology 11/2013; · 2.32 Impact Factor
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    ABSTRACT: A phytochemical investigation on the essential oil of Thuja orientalis resulted in the isolation and identification of three new sesquiterpenes, 3α-methoxy-4α-epoxythujopsane (1), Δ3,15-4β-epoxythujopsene (2), and Δ3,4-thujopsen-2,15-diol (3), together with eight known sesquiterpenoids (4-11). The structures of these new compounds were elucidated based on spectroscopic data analyses including extensive 2D-NMR data and HR-ESIMS. The full assignments of 1H and 13C NMR chemical shifts for thujopsadiene (4) were obtained by 2D-NMR for the first time. All compounds (1-11) showed antiproliferative activities against the SK-OV-3 and SK-MEL-2 cell lines with IC50 values of 5.85-28.64 µM. In addition, compounds 1, 3, 4, 7, 8, and 9 significantly inhibited nitric oxide production in lipopolysaccharide-activated BV-2 cells with IC50 values of 3.93-17.85 µM without cell toxicity.
    Planta Medica 10/2013; · 2.35 Impact Factor
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    ABSTRACT: A new series of 2,4-dianilino-5-fluoropyrimidine derivatives were designed and synthesized and their anaplastic lymphoma kinase (ALK) inhibitory activities were evaluated by biochemical and cell-based assays in order to discover a new ALK inhibitor. Most compounds synthesized showed good inhibitory activities against ALK and good cytotoxic activities in H3122 cell line. The best compound 6f showed good activity against wild-type ALK along with crizotinib-resistant mutant ALK, and it showed 6 times better activity in cell-based assay than crizotinib. Some SAR studies were performed by the comparisons of the activities between 6 and the designed-synthesized compounds.
    Archives of Pharmacal Research 10/2013; · 1.54 Impact Factor
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    ABSTRACT: The new lignan glucoside, acutumoside (1), was isolated from Sinomenium acutum rhizomes together with nine known compounds (2-10). The structure of 1 was elucidated on the basis of extensive spectroscopic analyses, including two-dimensional nuclear magnetic resonance and chemical reactions. Compounds 2, 7, 8, and 10 displayed potential antiproliferative activity against A549, SK-OV-3, SK-MEL-2, and HCT-15 cell lines, while compound 1 showed weak activity against these human tumor cells.
    Bioscience Biotechnology and Biochemistry 10/2013; · 1.27 Impact Factor
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    ABSTRACT: Components of gelatin/polycaprolactone (PCL) electrospun scaffolds are released to surrounding media and cause osmotic changes that adversely affect cell viability and proliferation. In this study, the physiological properties of gelatin/PCL scaffolds were investigated by qRT-PCR and by performing cellular studies on HEK 293 cells. Components released from gelatin/PCL scaffolds were found to induce osmotic stress response in these cells. However, osmotic stress was inhibited by adding fetal bovine serum (FBS) to scaffolds. In addition, focal adhesion related genes were found to be up-regulated in HEK 293 cells on gelatin/PCL/20% FBS scaffolds, and this induced the down-regulations of cell-death related genes. Furthermore, the inclusion of 20% FBS improved the viabilities of HEK 293 cells on gelatin/PCL scaffolds. This study indicates that adding FBS to gelatin/PCL scaffolds improves scaffold bio-affinity. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
    Journal of Applied Polymer Science 09/2013; 129(6). · 1.40 Impact Factor
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    ABSTRACT: The phytochemical investigation of Rudbeckia laciniata L. obtained a new flavonol glycoside (1), together with four flavonol glycosides (2-5) and eight quinic acid derivatives (6-13). The structure was elucidation by means of spectroscopic methods and chemical evidence. The isolated compounds were tested for cytotoxicity against four human tumor cell lines in vitro using the sulforhodamine B bioassay.
    Archives of Pharmacal Research 09/2013; · 1.54 Impact Factor
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    ABSTRACT: Two new steroidal saponins, cynanside A (1) and B (2) were isolated together with three known compounds (3-5) from the roots of Cynanchum paniculatum (Bunge) Kitag. The structures of 1 and 2 were elucidated on the basis of spectroscopic analyses, including extensive 2D NMR and acid hydrolysis. We evaluated the cytotoxicity of isolates (1-5) against A549, SK-OV-3, SK-MEL-2, and HCT-15 cell lines in vitro using the SRB bioassay. Compounds 1 and 2 showed selective cytotoxicity against SK-MEL-2 cells with IC50 values of 26.55 and 17.36μM, respectively.
    Carbohydrate research 09/2013; 381C:1-5. · 2.03 Impact Factor
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    ABSTRACT: The synthesis of bis-ortho-alkoxy-para-piperazinesubstituted-2,4-dianilinopyrimidines is described and their structure-activity-relationship to anaplastic lymphoma kinase (ALK) is presented. KRCA-0008 is selective and potent to ALK and Ack1, and displays drug-like properties without hERG liability. KRCA-0008 demonstrates in vivo efficacy comparable to Crizotinib in xenograft mice model.
    Bioorganic & medicinal chemistry letters 09/2013; · 2.65 Impact Factor
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    ABSTRACT: Pharbinilic acid (1), the first naturally occurring allogibberic acid, was isolated from ethanol extracts of morning glory (Pharbitis nil) seeds. Its absolute configuration was determined by NOESY NMR and ECD experiments. Compound 1 showed weak cytotoxicity against A549, SK-OV-3, SK-MEL-2, and HCT-15 cells and weakly inhibited nitric oxide production in lipopolysaccharide-activated BV-2 microglia cells.
    Journal of Natural Products 07/2013; · 3.29 Impact Factor
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    ABSTRACT: Bioassay-guided fractionation and chemical investigation of the extract of Rhus verniciflua bark resulted in the identification of six polyphenols, rhusopolyphenols A-F (1-6), together with four known compounds including (2R,3S,10S)-7,8,9,13-tetrahydroxy-2-(3,4-dihydroxyphenyl)-2,3-trans-3,4-cis-2,3,10-trihydrobenzopyrano[3,4-c]-2-benzopyran-1-one (7), peapolyphenol C (8), cilicione-b (9) and (αR)-α,3,4,2',4'-pentahydroxydihydrochalcone (10). The structures of these polyphenols were elucidated by spectroscopic analysis, including 1D and 2D NMR, and HR-ESIMS, and their absolute configurations were further confirmed by a combination of chemical methods and CD data analysis. All isolates were evaluated for their antiproliferative activities against four human tumor cell lines (A549, SK-OV-3, SK-MEL-2, and HCT-15), and compounds 4-6, 9 and 10 showed antiproliferative activity against the tested cells, with IC50 values of 3.31-18.51μM. On the basis of the expanded understanding that inflammation is a crucial cause of tumor progression, the anti-inflammatory activities of these compounds were determined by measuring nitric oxide (NO) levels in the medium of murine microglia BV-2 cells. Compounds 5 and 10 significantly inhibited NO production in lipopolysaccharide (LPS)-stimulated murine microglia BV-2 cells with IC50 values of 28.90 and 12.70μM, respectively.
    Phytochemistry 06/2013; · 3.05 Impact Factor
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    ABSTRACT: In our continuing search for structurally interesting and bioactive metabolites from Korean wild mushrooms, bioassay-guided fractionation and a chemical investigation of the MeOH extracts of the fruiting bodies of the mushroom Naematoloma fasciculare resulted in the isolation of four new lanostane triterpenoids (1-4), together with 11 known compounds (5-15). The structures of 1-5 were determined by a combination of 1D and 2D NMR and HRMS. The absolute configuration of the 3-hydroxy-3-methylglutaryl group as a side chain in 1 and 2 was determined by the alkaline methanolysis method. The full NMR data assignment of the known compound fasciculol G (5) is reported for the first time. Compounds 1-15 were tested for their antiproliferative activities against four human cancer cell lines (A549, SK-OV-3, SK-MEL-2, and HCT-15) and evaluated for their inhibitory effects on nitric oxide production in a lipopolysaccharide-activated murine microglial cell line.
    Journal of Natural Products 05/2013; · 3.29 Impact Factor
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    ABSTRACT: A bioassay-guided fractionation and chemical investigation of the MeOH extract of the twigs of Euonymus alatus resulted in the isolation and identification of five new phenolic compounds, named alatusols A-E (1-5), together with six known compounds (6-11). The structures of these new compounds were elucidated through spectral analysis, including extensive 2D-NMR data, and their absolute configurations were determined by the modified Mosher's method. Compounds 1-3 and 7-9 showed consistent cytotoxicity against A549, SK-OV-3, SK-MEL-2, and HCT-15 cell lines with IC50 values of 15.20-29.81 µM. In addition, compounds 5 and 7 inhibited nitric oxide production in lipopolysaccharide-activated BV-2 cells with IC50 values of 22.77 and 32.52 µM, respectively.
    Planta Medica 03/2013; · 2.35 Impact Factor
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    ABSTRACT: The bioassay-guided fractionation of the methanolic extract of the title plant leads to isolation and identification of thirteen phenolic derivatives, including the new neolignans surinamensinol A (I) and B (II) and the new phenolic compound acoramol (III).
    ChemInform 02/2013; 44(7).
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    ABSTRACT: A further phytochemical investigation of the rhizomes of Acorus gramineus afforded three new quinone derivatives (1-3), together with two known compounds (4 and 5). The identification and structural elucidation of these new compounds were based on 1D and 2D NMR (COSY, HMQC, HMBC and NOESY) and MS data. The absolute configurations were established on the basis of their circular dichroism (CD) data. To investigate the anti-neuroinflammatory effects of the isolated compounds (1-5), the nitric oxide (NO) production was evaluated in the lipopolysaccharide-activated microglia cell line, BV-2. Compounds (1-5) were also tested for their cytotoxicity against four human tumor cell lines (A549, SK-OV-3, SK-MEL-2, and HCT-15) in vitro by using the SRB assay.
    Bioscience Biotechnology and Biochemistry 01/2013; 77(2):276-80. · 1.27 Impact Factor
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    ABSTRACT: Although MLL-AF9 caused by the chromosomal translocation t(9;11) has a critical role in acute myeloid leukemia, the molecular pathogenesis is poorly understood. Here, we identified that the cell fate determination factor DACH1 is directly up-regulated by MLL-AF9. Recently we showed that the forced expression of DACH1 in myeloid cells induced p27(Kip1) and repressed p21(Cip1), which is a pivotal characteristic of the myeloid progenitor. Consistent with our previous study, ectopic expression of DACH1 contributed to the maintenance of colonogenic activity and blocked the differentiation of myeloid progenitors. Moreover, we here identified an endogenous HOXA9-DACH1 complex mediated by the carboxyl terminus of DACH1 in t(9;11) leukemia cells. qRT-PCR revealed that DACH1 has a stronger transcription-promoting activity with HOXA9 than does PBX2 with HOXA9. Furthermore, C/EBPα and GATA-1 can directly bind to the promoter of DACH1 and act as a transcriptional suppressor. Expression of DACH1 is down-regulated during myeloid differentiation and shows an inverse pattern compared to C/EBPα and GATA-1 expression. However, ectopic expression of C/EBPα and/or GATA-1 could not abrogate the over-expression of DACH1 induced by MLL-AF9. Therefore, we postulate that the inability of C/EBPα and GATA-1 to down-regulate DACH1 expression induced by MLL-AF9 during myeloid differentiation may contribute to t(9;11) leukemogenesis.
    Biochemical and Biophysical Research Communications 08/2012; 426(3):299-305. · 2.41 Impact Factor
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    ABSTRACT: On the search for anti-cancer compounds from natural Korean medicinal sources, a bioassay-guided fractionation and chemical investigation of the MeOH extract from the rhizomes of Acorus gramineus resulted in the isolation and identification of thirteen phenolic derivatives (1-13) including two new 8-O-4'-neolignans, named surinamensinols A (1) and B (2) and a new phenolic compound, named acoramol (9). The structures of these new compounds were elucidated on the basis of 1D and 2D NMR spectroscopic data analyses as well as circular dichroism (CD) spectroscopy studies. The cytotoxic activities of the isolates (1-13) were evaluated by determining their inhibitory effects on human tumor cell lines. The new 8-O-4'-neolignans, compounds 1 and 2, showed moderate antiproliferative activities against A549, SK-OV-3, SK-MEL-2, and HCT-15 cell lines with IC(50) values in the range of 4.17-26.18μM. On the basis of the expanded understanding that inflammation is a crucial cause of tumor progression, anti-inflammatory activities of these compounds were determined by measuring nitric oxide (NO) levels in the medium using murine microglia BV-2 cells. Compounds 1, 2, 4, 7 and 10 inhibited NO production in BV-2 stimulated by lipopolysaccharide with IC(50) values of 8.17-18.73μM via NO scavenging, inhibition of iNOS activity, and/or suppression of iNOS expression.
    Bioorganic & medicinal chemistry letters 08/2012; 22(19):6155-9. · 2.65 Impact Factor
  • The Journal of Antibiotics 07/2012; · 2.19 Impact Factor

Publication Stats

504 Citations
203.01 Total Impact Points

Institutions

  • 1992–2014
    • Korea Research Institute of Chemical Technology
      • Division of Drug Discovery Research
      Daiden, Daejeon, South Korea
  • 2013
    • Harvard University
      • Department of Chemistry and Chemical Biology
      Cambridge, MA, United States
    • Harvard Medical School
      • Department of Biological Chemistry and Molecular Pharmacology
      Boston, MA, United States
  • 2002–2013
    • Sungkyunkwan University
      • School of Pharmacy
      Seoul, Seoul, South Korea
  • 2007
    • Woosuk University
      완주, North Jeolla, South Korea
  • 2004
    • Kookmin University
      • College of Forest Science
      Seoul, Seoul, South Korea