ORCID Profile
0000-0003-3275-968X
Current Organisations
Agency for Science, Technology and Research
,
National University of Singapore
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Publisher: Elsevier BV
Date: 12-2004
Publisher: Frontiers Media SA
Date: 06-06-2022
DOI: 10.3389/FMICB.2022.898976
Abstract: Endophytic microorganisms are an important source of bioactive secondary metabolites. In this study, fungal endophytes obtained from A*STAR’s Natural Product Library (NPL) and previously isolated from different habitats of Singapore were investigated for their ersity, antimicrobial, and cytotoxic activities. A total of 222 fungal strains were identified on the basis of sequence analysis of ITS region of the rDNA gene. The identified fungal strains belong to 59 genera distributed in 20 orders. Majority of the identified strains (99% 219 strains) belong to the phylum Ascomycota , while two strains belonged to the phylum Basidiomycota , and only one strain was from Mucoromycota phylum. The most dominant genus was Colletotrichum accounting for 27% of all the identified strains. Chemical elicitation using 5-azacytidine and suberoylanilide hydroxamic acid (SAHA) and variation of fermentation media resulted in the discovery of more bioactive strains. Bioassay-guided isolation and structure elucidation of active constituents from three prioritized fungal strains: Lophiotrema sp. F6932, Muyocopron laterale F5912, and Colletotrichum tropicicola F10154, led to the isolation of a known compound palmarumycin C 8 and five novel compounds palmarumycin CP 30 , muyocopronol A-C and tropicicolide. Tropicicolide displayed the strongest antifungal activity against Aspergillus fumigatus with an IC 50 value of 1.8 μg/ml but with a weaker activity against the Candida albicans presenting an IC 50 of 7.1 μg/ml. Palmarumycin C 8 revealed the best antiproliferative activity with IC 50 values of 1.1 and 2.1 μg/ml against MIA PaCa-2 and PANC-1 cells, respectively.
Publisher: American Chemical Society (ACS)
Date: 14-09-2004
DOI: 10.1021/NP049844C
Abstract: An extract from the fungus Emericella aurantiobrunnea was found to compete with macrophage inflammatory protein (MIP)-1alpha for binding to human CCR5 in a scintillation proximity assay (SPA). Bioassay-guided fractionation led to the isolation of variecolin (1) and variecolol (2), which had IC50 values of 9 and 32 microM, respectively. An X-ray crystal structure of variecolin (1) was obtained for the first time. Also isolated were four new inactive analogues, emericolin A (3), B (4), C (5), and D (6), and the relative stereochemistry of these compounds was determined by NMR methods using ROESY spectra and 1H/1H coupling constants.
Publisher: Elsevier BV
Date: 11-2003
DOI: 10.1016/S0031-9422(03)00448-5
Abstract: Three compounds, 2,3-dihydroxy-4-methoxy-6,6,9-trimethyl-6H-dibenzo[b,d]pyran (1), 8-methoxy-2-methyl-2-(4-methyl-3-pentenyl)-2H-1-benzopyran-6-ol (2) and 4-methoxy-3-(3-methyl-2-butenyl)-benzoic acid (3), have been isolated from Wigandia urens. The structures of compounds 1, 2 and 3 were determined from spectroscopic data and showed activity in a CCR5 assay with IC(50) values of 33, 46 and 26 muM respectively.
Publisher: MDPI AG
Date: 23-12-2022
DOI: 10.3390/MOLECULES28010101
Abstract: Thiopeptides are macrocyclic natural products with potent bioactivity. Nine new natural thiopeptides (1–9) were obtained from a Nonomuraea jiangxiensis isolated from a terrestrial soil s le collected in Singapore. Even though some of these compounds were previously synthesized or isolated from engineered strains, herein we report the unprecedented isolation of these thiopeptides from a native Nonomuraea jiangxiensis. A comparison with the literature and a detailed analysis of the NMR and HRMS of compounds 1–9 was conducted to assign their chemical structures. The structures of all new compounds were highly related to the thiopeptide antibiotics GE2270, with variations in the substituents on the thiazole and amino acid moieties. Thiopeptides 1–9 exhibited a potent antimicrobial activity against the Gram-positive bacteria, Staphylococcus aureus with MIC90 values ranging from 2 µM to 11 µM. In addition, all compounds were investigated for their cytotoxicity against the human cancer cell line A549, none of the compounds were cytotoxic.
Publisher: Springer Science and Business Media LLC
Date: 14-03-2012
DOI: 10.1038/JA.2012.15
Publisher: Elsevier BV
Date: 10-2008
Publisher: American Chemical Society (ACS)
Date: 23-07-2003
DOI: 10.1021/NP030146M
Abstract: Two new compounds, 10-methoxydihydrofuscin (1) and fuscinarin (2), and one known compound, fuscin (3), have been isolated from the soil fungus Oidiodendron griseum. These compounds were found to compete effectively with macrophage inflammatory protein (MIP)-1 alpha for binding to human CCR5, an important anti HIV-1 target that interferes with HIV entry into cells. The structures of these compounds were elucidated by spectroscopic methods.
Publisher: MDPI AG
Date: 24-11-2022
DOI: 10.3390/MOLECULES27238196
Abstract: Large scale cultivation and chemical investigation of an extract obtained from Actimonadura sp. resulted in the identification of six previously undescribed spirotetronates (pyrrolosporin B and decatromicins C–G 7–12), along with six known congeners, namely decatromicins A–B (1–2), BE-45722B–D (3–5), and pyrrolosporin A (6). The chemical structures of compounds 1–12 were characterized via comparison with previously reported data and analysis of 1D/2D NMR and MS data. The structures of all new compounds were highly related to the spirotetronate type compounds, decatromicin and pyrrolosporin, with variations in the substituents on the pyrrole and aglycone moieties. All compounds were evaluated for antibacterial activity against the Gram-negative bacteria, Acinetobacter baumannii and Gram-positive bacteria, Staphylococcus aureus and were investigated for their cytotoxicity against the human cancer cell line A549. Of these, decatromicin B (2), BE-45722B (3), and pyrrolosporin B (7) exhibited potent antibacterial activities against both Gram-positive (MIC90 between 1–3 μM) and Gram-negative bacteria (MIC90 values ranging from 12–36 μM) with weak or no cytotoxic activity against A549 cells.
Publisher: American Chemical Society (ACS)
Date: 25-02-2006
DOI: 10.1021/NP050528N
Abstract: Bioassay-directed fractionation using a glucocorticoid receptor assay led to the isolation of two new, weakly active polyprenylated acylphloroglucinol derivatives, sundaicumones A (1) and B (2), from the leaves of Calophyllum sundaicum collected in Singapore. The structures of 1 and 2, which were established by spectroscopic methods, contain a 3-substituted hexanoic acid unit not previously reported in other polyprenylated acylphloroglucinols.
Publisher: Elsevier BV
Date: 10-2001
Publisher: American Chemical Society (ACS)
Date: 27-02-2015
Publisher: American Chemical Society (ACS)
Date: 03-06-2011
DOI: 10.1021/NP1006179
Abstract: A prefractionated Streptomyces-derived extract was initially identified as being active using a luciferase-based AMP-activated protein kinase (AMPK) assay. Bioassay-guided fractionation led to the isolation of the new compound quinazolin-4(3H)-one (1) as the active component. However, 1 was shown to have potent firefly luciferase inhibitory activity with no effect on AMPK. This is the first report of a natural luciferase inhibitor.
Publisher: Elsevier BV
Date: 04-2009
Publisher: American Chemical Society (ACS)
Date: 05-06-2002
DOI: 10.1021/NP010626I
Abstract: Two new compounds, agonodepsides A (1) and B (2), were isolated from a nonsporulating filamentous fungus, F7524. The compounds were purified via reversed-phase chromatography and their structures determined by spectroscopic methods. Agonodepside A (1) was found to inhibit the mycobacterial InhA enzyme with an IC50 value of 75 microM, while 2 was inactive at 100 microM.
Publisher: American Chemical Society (ACS)
Date: 21-12-2000
DOI: 10.1021/NP000381U
Abstract: The crude extract of the broth of Aspergillus ochraceus was found to inhibit the final stage of polyprotein processing during hepatitis C virus replication. Bioassay-guided fractionation led to the isolation of the known compound mellein as the active component of the extract. Also isolated were circumdatin F and a new alkaloid, circumdatin G. The structure of circumdatin G was determined by spectroscopic analysis.
Location: No location found
No related grants have been discovered for Siew Bee Ng.