Yeon-Ju Lee

Korea Institute of Science and Technology, Sŏul, Seoul, South Korea

Are you Yeon-Ju Lee?

Claim your profile

Publications (53)182.54 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Chemical examination of the ethyl acetate extract from the fermentation broth of the marine-derived bacterium Bacillus licheniformis resulted in the isolation of two new glycolipids, ieodoglucomide C (1) and ieodoglycolipid (2). The structural characterization of 1 and 2 was achieved by extensive spectroscopic evidence, including 2D NMR experiments. A combination of chemical derivatization techniques followed by NMR studies, LC-MS data analysis and a literature review was deployed for the establishment of the stereo-configurations of 1 and 2. Compounds 1 and 2 exhibited good antibiotic properties against Staphylococcus aureus, Bacillus subtilis, Bacillus cereus, Salmonella typhi, Escherichia coli and Pseudomonas aeruginosa with MICs ranging from 0.01 to 0.05 μM. Furthermore, the antifungal activity of 1 and 2 was evaluated against plant pathogenic fungi Aspergillus niger, Rhizoctonia solani, Botrytis cinerea and Colletotrichum acutatum as well as the human pathogen Candida albicans. Compounds 1 and 2 inhibited the mycelial growth of these pathogens with MIC values of 0.03-0.05 μM, revealing that these compounds are good candidates for the development of new fungicides.
    Lipids 04/2015; 50(5). DOI:10.1007/s11745-015-4014-z · 2.35 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We describe a new concise method for the synthesis of psammaplin A and its analogues, and antitumor activity of psammaplin A analogues. Psammaplin A was obtained with 41% yield in 5 steps from 3-bromo-4-hydroxybenzaldahyde and ethyl acetoacetate via Knoevenagel condensation and α-nitrosation as key steps. Twenty eight analogues of psammaplin A were prepared employing the new synthetic approach. Structure-activity relationship study against cytotoxicity reveal that the free oxime group and disulfide functional group were responsible for high cytotoxicity. Also the bromotyrosine component was relatively tolerable and hydrophobic aromatic groups preserved the cytotoxicity. The cytotoxicity of aromatic group is dependent on the size and spatial geometry. Among them, five compounds showed comparable cytotoxicity to psammaplin A. Compound 30 exhibited potential HDAC inhibitory activity and in vivo antitumor activity. Copyright © 2015 Elsevier Masson SAS. All rights reserved.
    European Journal of Medicinal Chemistry 04/2015; 96:218-230. DOI:10.1016/j.ejmech.2015.04.001 · 3.43 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Eight scalarane sesterterpenoids, including four new compounds, were isolated from the marine sponge Scalarispongia sp. The structures of the new compounds were elucidated by 2D-NMR and HRMS analyses. All of the isolated compounds, with the exception of 16-O-deacetyl-12,16-epi-scalarolbutanolide, showed significant in vitro cytotoxicity (GI50 values down to 5.2 μM) against six human cancer cell lines.
    International Journal of Molecular Sciences 11/2014; 15(11):20045-20053. DOI:10.3390/ijms151120045 · 2.34 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Nine suvanine analogs including suvanine phenethylammonium salt and two new compounds were isolated from the marine sponge Coscinoderma sp., collected from Chuuk State, Federated States of Micronesia. The structures of the new compounds were elucidated by 2D NMR and HRMS analyses. Suvanine and a new analog exhibited weak but selective cytotoxicity against colon (HCT-15), lung (NCI-H23), stomach (NUGC-3), and prostate (PC-3) cancer cell lines.
    Archives of Pharmacal Research 09/2014; DOI:10.1007/s12272-014-0479-1 · 1.75 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Two new α-pyrone derivatives, violapyrones H (1) and I (2), along with known violapyrones B (3) and C (4) were isolated from the fermentation broth of a marine actinomycete Streptomyces sp. The strain was derived from a crown-of-thorns starfish, Acanthaster planci, collected from Chuuk, Federated States of Micronesia. The structures of violapyrones were elucidated by the analysis of 1D and 2D NMR and HR-ESIMS data. Violapyrones (1-4) exhibited cytotoxicity against 10 human cancer cell lines with GI50 values of 1.10-26.12 μg/mL when tested using sulforhodamine B (SRB) assay. This is the first report on the cytotoxicity of violapyrones against cancer cell lines and the absolute configuration of violapyrone C.
    Marine Drugs 06/2014; 12(6):3283-3291. DOI:10.3390/md12063283 · 3.51 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Antifungal resistance and toxicity problems of conventional fungicides highlighted the requirement of search for new safe antifungal agents. To comply with the requirement, we discovered four new non-cytotoxic lipopeptides, gageopeptides A–D, 1–4, from a marine-derived bacterium Bacillus subtilis. The structures and stereochemistry of gageopeptides were determined by NMR data analysis and chemical means. Gageopeptides exhibited significant antifungal activities against pathogenic fungi Rhizoctonia solani, Botrytis cinerea, and Colletotrichum acutatum with minimum inhibitory concentration (MIC) values of 0.02–0.06 μM. In addition, these lipopeptides showed significant motility inhibition and lytic activities against zoospores of the late blight pathogen Phytophthora capsici. These compounds also showed potent antimicrobial activity against Gram positive and Gram negative bacteria with MIC values of 0.04–0.08 μM. However, gageopeptides A–D did not exhibit any cytotoxicity (GI50 > 25 μM) against cancer cell lines in sulforhodamine B (SRB), 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT), and WST-1 ((4-[3–4-iodophenyl]-2-(4-nitrophenyl)-2H-5-tetrazolio)-1,3-benzene disulfonate)) assays, demonstrating that these compounds could be promising candidates for the development of non-cytotoxic antifungal agents.
    Journal of Agricultural and Food Chemistry 05/2014; 62(24):5565–5572. DOI:10.1021/jf502436r · 3.11 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The suvanines, a new suvanine salt, five new (2, 4-8) and two known sesterterpenes from the same structural class, and two new modified lipids (9 and 10) were isolated from a Coscinoderma sp. sponge collected from Chuuk Island, Micronesia. On the basis of the results of combined spectroscopic and chemical analyses, a new suvanine salt was determined to be the suvanine N,N-dimethyl-1,3-dimethylherbipoline salt (2) and suvanine-lactam derivatives (4-8) formed by condensations between an oxidized furan moiety and amino acids. The lipid metabolites were found to be new derivatives of the taurine-containing deacyl irciniasulfonic acid class. The suvanines exhibited moderate cytotoxicities against the K562 and A549 cell lines, while the new suvanine salt (2) had significant antibacterial activity.
    Journal of Natural Products 05/2014; 77(6). DOI:10.1021/np500156n · 3.95 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Three new 5-hydroxyindole alkaloids (1, 2, 3) along with seven known analogs (4, 5, 6, 7, 8, 9, 10) were isolated from a Dokdo marine sponge Scalarispongia sp. The elucidation of the structures of the new compounds by spectroscopic analyses indicated that these compounds were an indole glyoxylate (1), a mono-indole analog of hyrtinadine A (2), and a symmetrical bis-indole with pyridine linker (3). The comparison of IC50 values for obtained compounds against a human leukemia cell line revealed that the bis-indole structure is a requirement for cytotoxicity.
    ChemInform 05/2014; 45(18). DOI:10.1002/chin.201418219
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Gageotetrins A-C (1-3), a unique class of linear lipopeptides, consisting of di- and tetrapeptides and a new fatty acid were isolated from a Marine Bacillus subtilis. The structures of 1-3 were assigned by spectroscopic data and their absolute stereochemistries were ascertained by chemical derivatization. Compounds 1-3 displayed good antimicrobial activities with MIC values of 0.01-0.06 μM. However, these compounds failed to register any cytotoxicity (GI50 > 30 μg/ml) against human cancer cell lines.
    Organic Letters 02/2014; 16(3):928-31. DOI:10.1021/ol403657r · 6.32 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Concerning the requirements of effective drug candidates to combat against high rising multidrug resistant pathogens, we isolated three new linear lipopeptides, gageostatins A-C (1-3), consisting of hepta-peptides and new 3-β-hydroxy fatty acids from the fermentation broth of a marine-derived bacterium Bacillus subtilis. Their structures were elucidated by analyzing a combination of extensive 1D, 2D NMR spectroscopic data and high resolution ESIMS data. Fatty acids, namely 3-β-hydroxy-11-methyltridecanoic and 3-β-hydroxy-9,11-dimethyltridecanoic acids were characterized in lipopeptides 1 and 2, respectively, whereas an unsaturated fatty acid (E)-7,9-dimethylundec-2-enoic acid was assigned in 3. The 3R configuration of the stereocenter of 3-β-hydroxy fatty acids in 1 and 2 was established by Mosher's MTPA method. The absolute stereochemistry of amino acid residues in 1-3 was ascertained by acid hydrolysis followed by Marfey's derivatization studies. Gageostatins 1-3 exhibited good antifungal activities with MICs values of 4-32 µg/mL when tested against pathogenic fungi (R. solani, B. cinerea and C. acutatum) and moderate antibacterial activity against bacteria (B. subtilis, S. aeureus, S. typhi and P. aeruginosa) with MICs values of 8-64 µg/mL. Futhermore, gageostatins 1-3 displayed cytotoxicity against six human cancer cell lines with GI50 values of 4.6-19.6 µg/mL. It is also noteworthy that mixed compounds 1+2 displayed better antifungal and cytotoxic activities than individuals.
    Marine Drugs 02/2014; 12(2):871-85. DOI:10.3390/md12020871 · 3.51 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Background / Purpose: Microorganisms from marine origins continue to be potential producers of bioactive secondary metabolites. In fact, they are ubiquitous in the marine environment and can tolerate adverse conditions such as high temperature, pressure, salinity and pH, and possess unique metabolic pathways that are different from their terrestrial counterparts. As a consequence, a large number of natural product research on marine-derived Bacillus sp. resulted in the discovery of a diverse class of secondary metabolites including lipopeptides, polypeptides, macrolactones, fatty acids, polyketides, lipoamides, and isocoumarins.As part of our ongoing research presenting new antimicrobials to meet increasing demands against rising multidrug resistant pathogens, we discovered five new linear lipopeptides, kiostostatins 1-5 from a marine-derived bacterium B. subtilis. Main conclusion: In summary, we isolated five linear lipopeptides, kiostostatins 1-5, possessing new fatty acid moiety, from the marine derived- bacterium B. subtilis. A new unsaturated fatty acid was characterized as (E)-7,9-dimethylundec-4-enoic acid in compound 5. These lipopeptides displayed moderate antibacterial and good antifungal activity. Furthermore, with the exception of 1 and 2, compounds 3-5 exhibited cytotoxic activity against six human cancer cell lines with GI50 values of 4.6-23.2 micro-g/mL, respectively.
    10th International Marine Biotechnology Conference (IMBC) 2013; 12/2013
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The nitric oxide inhibitory (NOI) and antioxidant (ABTS and DPPH radical scavenging effects with reducing power) activities of the ethanol (EtOH) extracts and solvent partitioned fractions from Scytosiphon lomentaria, Chorda filum, Agarum cribrosum, and Desmarestia viridis were investigated, and the correlation between biological activity and total phenolic (TP) and phlorotannin (TPT) content was determined by PCA analysis. The yield of EtOH extracts from four brown seaweeds ranged from 2.6 to 6.6% with the highest yield from D. viridis, and the predominant compounds in their solvent partitioned fractions had medium and/or less polarity. The TP and TPT content of the EtOH extracts were in the ranges of 25.0-44.1 mg GAE/g sample and 0.2-4.6 mg PG/g sample, respectively, which were mostly included in the organic solvent partitioned fractions. Strong NOI activity was observed in the EtOH extracts and their solvent partitioned fractions from D. viridis and C. filum. In addition, the EtOH extract and its solvent partitioned fractions of D. viridis exhibited little cytotoxicity to Raw 264.7 cells. The most potent ABTS and DPPH radical scavenging capacity was shown in the EtOH extracts and their solvent partitioned fractions from S. lomentaria and C. filum, and both also exhibited strong reducing ability. In the PCA analysis the content of TPT had a good correlation with DPPH ( r = 0.62), ABTS ( r = 0.69) and reducing power ( r = 0.65), however, an unfair correlation was observed between the contents of TP and TPT and NOI, suggesting that the phlorotannins might be responsible for the DPPH and ABTS radical scavenging activities.
    Ocean Science Journal 11/2013; 48(4). DOI:10.1007/s12601-013-0033-y
  • [Show abstract] [Hide abstract]
    ABSTRACT: Seventeen bromotyrosine-derived metabolites, including eight new compounds, were isolated from a Micronesian sponge of the genus Suberea. Four of the new compounds were psammaplysin derivatives (10-13), and the other four were ceratinamine derivatives (14-17). Of the compounds obtained, the psammaplysins exhibited cytotoxicity against human cancer cell lines (GI50 values down to 0.8 μM), while the ceratinamine and moloka'iamine analogues showed almost no activity. These results suggest that the spirooxepinisoxazoline ring system is a requirement for cytotoxicity and, therefore, may serve as an attractive molecular scaffold for the development of a potent anticancer agent.
    Journal of Natural Products 08/2013; 76(9). DOI:10.1021/np400448y · 3.95 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Marine sponges are relatively less explored for their chemical features but highly anticipated resource for bioactive compounds. In this paper we report the screening of marine sponges crude extracts for their potential to bind the adenosine A1 receptor. Many samples showed very promising activity and in order to identify the active components, a metabolomics-chemometrics approach is employed. Nuclear magnetic resonance spectroscopy is used for the metabolic profiling of the marine sponges and partial least squares (PLS) and orthogonal PLS (OPLS) algorithms are used to correlate the metabolomics with bioactivity data. Using several two dimensional-NMR techniques, the resonances responsible for the separation of high activity samples from the medium and low activity samples were identified as associated to metabolites like halisulfate 1, halisulfate 3–5, and suvanine (1–5), all belongs to sesterterpenes class. The reference compounds for these metabolites are also tested for the activity, which endorse the findings of the applied methodology.
    Metabolomics 08/2013; 9(4):778-785. DOI:10.1007/s11306-013-0498-9 · 3.97 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Ieodoglucomides A (1) and B (2), unique glycolipopeptides consisting of an amino acid, a new fatty acid, a succinic acid, and a sugar, were isolated from a Marine-derived bacterium Bacillus licheniformis. The absolute stereochemistry of 1 and 2 was determined by deploying coupling constants, Marfey’s and Mosher’s methods, and literature reviews. Compounds 1 and 2 displayed moderate in vitro antimicrobial activity. Furthermore, ieodoglucomide B (2) exhibited cytotoxic activity against lung cancer and stomach cancer cell lines with GI50 values of 25.18 and 17.78 μg/mL, respectively.
    Organic Letters 04/2013; 15(8). DOI:10.1021/ol4008603 · 6.32 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Marine bacteria are a potential source of structurally diversified bioactive secondary metabolites that are not found in terrestrial sources. In our continuous effort to search for new antimicrobial agents from marine-derived bacteria, we isolated a bacterial strain 109GGC020 from a marine sediment sample collected from Gageocho, Republic of Korea. The strain was identified as Bacillus subtilis based on a 16s rRNA sequence analysis. After a 7 day fermentation of the B. subtilis strain under optimum growth conditions three new and four known secondary metabolites were discovered using chromatographic procedures and their biological activities were evaluated against both bacteria and crop devastating fungi. The discovered metabolites were confirmed by extensive 2D NMR and high-resolution ESI-MS data analyses to have the structures of new macrolactin derivatives, gageomacrolactins 1-3 and known macrolactins A (4), B (5), F (6) and W (7). The stereoconfigurations of 1-3 were assigned based on coupling constant values, chemical derivatization studies, and a literature review. The coupling constants were very crucial to determine the relative geometries of olefins in 1-3 because of overlap of the 1H NMR signals. The NMR data of these compounds were recorded in different solvents to overcome this problem and obtain accurate coupling constant values. The new macrolactin derivatives 1-3 displayed good antibiotic properties against both Gram-positive (S. aureus, B. subtilis, and B. cereus) and Gram-negative (E. coli, S. typhi and P. aeruginosa) bacteria with minimum inhibitory concentration (MIC) values of 0.02-0.05 μM. Additionally, the antifungal activities of 1-7 were evaluated against pathogenic fungi and found to inhibit mycelial growth of A. niger, B. cinerea, C. acutatum, C. albicans and R. solani with MIC values of 0.04-0.3 μM, demonstrating that these compounds were good fungicides.
    Journal of Agricultural and Food Chemistry 03/2013; 61(14). DOI:10.1021/jf4009229 · 3.11 Impact Factor
  • Bulletin- Korean Chemical Society 02/2013; 34(2):357-358. DOI:10.5012/bkcs.2013.34.2.357 · 0.84 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: An efficient enantioselective synthetic method for the synthesis of (2R)-5-phenyl-2-alkylproline tert-butyl esters was reported. The phase-transfer catalytic alkylation of tert-butyl-5-phenyl-3,4-dihydro-2H-pyrrole-2-carboxylate in the presence of chiral quaternary ammonium catalysts gave the corresponding alkylated products (up to 97% ee). The following diastereoselective reductions afforded chiral 5-phenyl-2-alkylprolines which can be applied to asymmetric synthesis as organocatalysts or synthesis of biologically active proline based compounds, such as chiral α-alkylated analogues of (+)-RP66803, as potential CCK antagonists.
    Organic & Biomolecular Chemistry 02/2013; DOI:10.1039/c3ob27089k · 3.49 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In the course of our ongoing research for antimicrobial agents, we isolated five new compounds, three 24-membered macrolactones, macrolactins X-Z (1-3) and two hydroxy unsaturated fatty acids, linieodolides A (5) and B (6), together with a known metabolite, macrolactinic acid (4), from the culture broth of a marine Bacillus sp. The structures of these metabolites were determined on the basis of their spectroscopic data interpretation. Their absolute configurations were addressed by modified Mosher's method and literature data review. Compounds 1-6 showed moderate to potent inhibitory activities (8∼128 μg ml(-1)) against selected pathogenic microorganisms.The Journal of Antibiotics advance online publication, 5 December 2012; doi:10.1038/ja.2012.102.
    The Journal of Antibiotics 12/2012; 67(8). DOI:10.1038/ja.2012.102 · 2.04 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A novel petrosiacetylene analog (petrosiacetylene E) has been isolated from the Korean marine sponge Petrosia sp., along with petrosiacetylene A, B and C. Their structures were elucidated on the basis of spectroscopic methods and the stereochemistry of the new compound was determined by using the modified Mosher's method. Petrosiacetylene E showed higher cytotoxicity against five human cancer cell lines than petrosiacetylene A and B, presumably due to the additional hydroxy group located at C-16.
    Lipids 10/2012; 48(1). DOI:10.1007/s11745-012-3727-5 · 2.35 Impact Factor