Displaying publications 1 - 20 of 100 in total

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  1. van der Sar SA, Blunt JW, Cole AL, Din LB, Munro MH
    J Nat Prod, 2005 Dec;68(12):1799-801.
    PMID: 16378381
    A new dichlorinated pulvinic acid derivative, methyl-3',5'-dichloro-4,4'-di-O-methylatromentate, was isolated from the fruiting body of a Scleroderma sp. The structure was determined using spectroscopic methods, and an X-ray analysis was carried out for confirmation of the structure. Compound was found to display moderate antimicrobial activity against Bacillus subtilis.
  2. Zgoda-Pols JR, Freyer AJ, Killmer LB, Porter JR
    J Nat Prod, 2002 Nov;65(11):1554-9.
    PMID: 12444676
    Two new resveratrol tetramers, hopeaphenol A (1) and isohopeaphenol A (2), along with the known vaticaphenol A (3), were isolated from the stem bark of Vatica oblongifolia ssp. oblongifolia through bioassay-guided fractionation. The structures and their relative stereochemistry were determined by spectroscopic techniques. Compounds 1 and 3 demonstrated moderate activity against methicillin-resistant Staphylococcus aureus and Mycobacterium smegmatis.
  3. Yoshikawa K, Tao S, Arihara S
    J Nat Prod, 2000 Apr;63(4):540-2.
    PMID: 10785436
    The stem of Stephanotis floribunda afforded a new cyclic pentapeptide stephanotic acid (1), possessing a novel 6-(leucin-3'-yl) tryptophan skeleton. The structure of 1 was assigned on the basis of extensive NMR experiments and a chemical reaction and shown to be closely related to the bicyclic octapeptide moroidin (3), a toxin from Laportea moroides.
  4. Yeap JS, Lim KH, Yong KT, Lim SH, Kam TS, Low YY
    J Nat Prod, 2019 02 22;82(2):324-329.
    PMID: 30698428 DOI: 10.1021/acs.jnatprod.8b00754
    Three new Lycopodium alkaloids comprising two lycodine-type alkaloids (1, 2) and one fawcettimine alkaloid (3), in addition to 16 known alkaloids, were isolated from Lycopodium platyrhizoma. The structures of these alkaloids were elucidated based on analysis of their NMR and MS data. Lycoplatyrine A (1) represents an unusual lycodine-piperidine adduct. The structures and absolute configurations of lycoplanine D (hydroxy-des- N-methyl-α-obscurine, 10) and lycogladine H (11) were confirmed by X-ray diffraction analysis.
  5. Yeap JS, Saad HM, Tan CH, Sim KS, Lim SH, Low YY, et al.
    J Nat Prod, 2019 11 22;82(11):3121-3132.
    PMID: 31642315 DOI: 10.1021/acs.jnatprod.9b00712
    A methanol extract of the stem bark of the Malayan Alstonia penangiana provided seven new bisindole alkaloids, comprising six macroline-sarpagine alkaloids (angustilongines E-K, 1-6) and one macroline-pleiocarpamine bisindole alkaloid (angustilongine L, 7). Analysis of the spectroscopic data (NMR and MS) of these compounds led to the proposed structures of these alkaloids. The macroline-sarpagine alkaloids (1-6) showed in vitro growth inhibitory activity against a panel of human cancer cell lines, inclusive of KB, vincristine-resistant KB, PC-3, LNCaP, MCF7, MDA-MB-231, HT-29, HCT 116, and A549 cells (IC50 values: 0.02-9.0 μM).
  6. Yap WS, Gan CY, Sim KS, Lim SH, Low YY, Kam TS
    J Nat Prod, 2016 Jan 22;79(1):230-9.
    PMID: 26717050 DOI: 10.1021/acs.jnatprod.5b00992
    Eleven new indole alkaloids (1-11) comprising seven aspidofractinine and four eburnane alkaloids, were isolated from the stem-bark extract of Kopsia pauciflora occurring in Malaysian Borneo. The aspidofractinine alkaloids include a ring-contracted, an additional ring-fused, a paucidactine regioisomer, two paucidactine, and one kopsine alkaloid. The structures of several of these alkaloids were also confirmed by X-ray diffraction analyses. The bisindole alkaloids isolated, norpleiomutine and kopsoffinol, showed in vitro growth inhibitory activity against human PC-3, HCT-116, MCF-7, and A549 cells and moderate effects in reversing multidrug-resistance in vincristine-resistant human KB cells.
  7. Yap WS, Gan CY, Low YY, Choo YM, Etoh T, Hayashi M, et al.
    J Nat Prod, 2011 May 27;74(5):1309-12.
    PMID: 21428274 DOI: 10.1021/np200008g
    Three new indole alkaloids (1-3), named grandilodines A-C, and five known ones were obtained from the Malayan Kopsia grandifolia. The structures were established using NMR and MS analyses and, in the case of 1 and 2, were confirmed by X-ray diffraction analyses. Alkaloids 1, 3, and lapidilectine B (8) were found to reverse multidrug resistance in vincristine-resistant KB cells.
  8. Xu YJ, Lai YH, Imiyabir Z, Goh SH
    J Nat Prod, 2001 Sep;64(9):1191-5.
    PMID: 11575954
    Nine new xanthones, parvixanthones A-I (1-9), isolated from the dried bark of Garcinia parvifolia, were found to have a common 1,3,6,7-oxygenated pattern for their xanthone nucleus, but various oxygenated isoprenyl or geranyl substituent groups. The structures were determined by spectroscopic methods.
  9. Xu YJ, Chiang PY, Lai YH, Vittal JJ, Wu XH, Tan BK, et al.
    J Nat Prod, 2000 Oct;63(10):1361-3.
    PMID: 11076552
    Leaf extracts of Garcinia parvifolia provided relatively high yields of four novel, cytotoxic prenylated depsidones. The structures were determined mainly by detailed NMR spectral analysis and X-ray crystallography.
  10. Xu YJ, Wu XH, Tan BK, Lai YH, Vittal JJ, Imiyabir Z, et al.
    J Nat Prod, 2000 Apr;63(4):473-6.
    PMID: 10785416
    Leaf extracts of the Malaysian plant Aglaia laxiflora provided two cytotoxic compounds, a new rocaglaol rhamnoside (1), a known rocaglaol (2), new (but inactive) flavonol-cinnamaminopyrrolidine adducts (3-6), and their probable biosynthetic precursors (7 and trimethoxyflavonol). All structures were elucidated primarily by 2D NMR spectroscopy. The structure and stereochemistry of aglaxiflorin A (3) were confirmed by single-crystal X-ray crystallography.
  11. Xu J, Harrison LJ, Vittal JJ, Xu YJ, Goh SH
    J Nat Prod, 2000 Aug;63(8):1062-5.
    PMID: 10978198
    Leaf extracts of Callicarpa pentandra provided four new clerodane-type diterpenoids (1-4), of which 1, 2, and 4 have ring-A-contracted structures. Their structures and stereochemistry were established by spectral data interpretation, and for 3 also by single-crystal X-ray diffraction.
  12. Wong SK, Wong SP, Sim KS, Lim SH, Low YY, Kam TS
    J Nat Prod, 2019 07 26;82(7):1902-1907.
    PMID: 31241923 DOI: 10.1021/acs.jnatprod.9b00255
    Three new alkaloids were isolated from the bark extract of the Malayan Kopsia arborea, viz., arbophyllidine (1), an unusual pentacyclic, monoterpenoid indole characterized by an absence of oxygen atoms and incorporating a new carbon-nitrogen skeleton, and arbophyllinines A (2) and B (3), two pentacyclic corynanthean alkaloids incorporating a hydroxyethyl-substituted tetrahydrofuranone ring. The structures of the alkaloids were deduced based on analysis of the MS and NMR data and confirmed by X-ray diffraction analyses. The absolute configuration of arbophyllidine (1) was established based on experimental and calculated ECD data, while that of arbophyllinine A was based on X-ray diffraction analysis (Cu Kα). A reasonable biosynthetic route to arbophyllidine (1) from a pericine precursor is presented. Arbophyllidine (1) showed pronounced in vitro growth inhibitory activity against the HT-29 human cancer cell line with IC50 6.2 μM.
  13. Wong CP, Seki A, Horiguchi K, Shoji T, Arai T, Nugroho AE, et al.
    J Nat Prod, 2015 Jul 24;78(7):1656-62.
    PMID: 26176165 DOI: 10.1021/acs.jnatprod.5b00258
    We have previously reported that bisleuconothine A (Bis-A), a novel bisindole alkaloid isolated from Leuconotis griffithii, showed cytostatic activity in several cell lines. In this report, the mechanism of Bis-A-induced cytostatic activity was investigated in detail using A549 cells. Bis-A did not cause apoptosis, as indicated by analysis of annexin V and propidium iodide staining. Expression of all tested apoptosis-related proteins was also unaffected by Bis-A treatment. Bis-A was found to increase LC3 lipidation in MCF7 cells as well as A549 cells, suggesting that Bis-A cytostatic activity may be due to induction of autophagy. Subsequent investigation via Western blotting and immunofluorescence staining indicated that Bis-A induced formation but prevented degradation of autophagosomes. Mechanistic studies showed that Bis-A down-regulated phosphorylation of protein kinase B (AKT) and its downstream kinase, PRAS40, which is an mTOR repressor. Moreover, phosphorylation of p70S6K, an mTOR-dependent kinase, was also down-regulated. Down-regulation of these kinases suggests that the increase in LC3 lipidation may be due to mTOR deactivation. Thus, the cytostatic activity shown by Bis-A may be attributed to its induction of autophagosome formation. The Bis-A-induced autophagosome formation was suggested to be caused by its interference with the AKT-mTOR signaling pathway.
  14. Velu SS, Di Meo F, Trouillas P, Sancho-Garcia JC, Weber JF
    J Nat Prod, 2013 Apr 26;76(4):538-46.
    PMID: 23441649 DOI: 10.1021/np300705p
    Oligostilbenoids (e.g., ampelopsin F, viniferin, pallidol) result from homogeneous or heterogeneous coupling of monomeric stilbenoid units, leading to various chemical structures. Oligostilbenoid synthesis is regio- and stereocontrolled. To tackle this regio- and stereocontrol, a supramolecular chemistry approach is required that can be achieved by quantum chemistry. The stability of noncovalent π-stacks, formed between two stilbenoid units prior to oxidation, is accurately evaluated with density functional theory (DFT) including dispersive effects (within the DFT-D formalism). These noncovalent arrangements drive the regiocontrol. The rest of the chemical pathway is a succession of dearomatization and rearomatization stages. The thermodynamics and kinetics of the processes are calculated with classical hybrid functionals. This study allows discrimination between the two main possible chemical pathways, namely, radical-neutral and radical-radical reactions. The former appears more likely, thermodynamics and kinetics being in perfect agreement with the experimental 1:2 ratio obtained for ampelopsin F:pallidol analogues, respectively.
  15. Tan SJ, Lim JL, Low YY, Sim KS, Lim SH, Kam TS
    J Nat Prod, 2014 Sep 26;77(9):2068-80.
    PMID: 25211145 DOI: 10.1021/np500439u
    A total of 20 new indole alkaloids comprising mainly oxidized derivatives of macroline- (including alstofonidine, a macroline indole incorporating a butyrolactone ring-F), pleiocarpamine-, and sarpagine-type alkaloids were isolated from the bark and leaf extracts of Alstonia angustifolia. The structures and relative configurations of these alkaloids were determined using NMR and MS analyses and in some instances confirmed by X-ray diffraction analyses. Alkaloids 3, 7, 35, and 41 showed moderate to weak activity, while 21 showed strong activity in reversing multidrug resistance in vincristine-resistant KB cells.
  16. Tan SJ, Low YY, Choo YM, Abdullah Z, Etoh T, Hayashi M, et al.
    J Nat Prod, 2010 Nov 29;73(11):1891-7.
    PMID: 21043460 DOI: 10.1021/np100552b
    A total of 25 alkaloids were isolated from the leaf and stem-bark extracts of Alstonia spatulata, of which five are new alkaloids of the strychnan type (alstolucines A-E, 1-5) and the other, a new alkaloid of the secoangustilobine A type (alstolobine A, 6). The structures of these alkaloids were established using NMR and MS analysis and, in the case of alstolucine B (2), also confirmed by X-ray diffraction analysis. A reinvestigation of the stereochemical assignment of scholaricine (13) by NMR and X-ray analyses indicated that the configuration at C-20 required revision. Alkaloids 1, 2, 6, 7, 9, 10, and 13 reversed multidrug resistance in vincristine-resistant KB cells.
  17. Tan CH, Yeap JS, Lim SH, Low YY, Sim KS, Kam TS
    J Nat Prod, 2021 05 28;84(5):1524-1533.
    PMID: 33872002 DOI: 10.1021/acs.jnatprod.1c00013
    A new linearly fused macroline-sarpagine bisindole, angustilongine M (1), was isolated from the methanolic extract of Alstonia penangiana. The structure of the alkaloid was elucidated based on analysis of the spectroscopic data, and its biological activity was evaluated together with another previously reported macroline-akuammiline bisindole from the same plant, angustilongine A (2). Compounds 1 and 2 showed pronounced in vitro growth inhibitory activity against a wide panel of human cancer cell lines. In particular, the two compounds showed potent and selective antiproliferative activity against HT-29 cells, as well as strong growth inhibitory effects against HT-29 spheroids. Cell death mechanistic studies revealed that the compounds induced mitochondrial apoptosis and G0/G1 cell cycle arrest in HT-29 cells in a time-dependent manner, while in vitro tubulin polymerization assays and molecular docking analysis showed that the compounds are microtubule-stabilizing agents, which are predicted to bind at the β-tubulin subunit at the Taxol-binding site.
  18. Suzuki M, Daitoh M, Vairappan CS, Abe T, Masuda M
    J Nat Prod, 2001 May;64(5):597-602.
    PMID: 11374951
    In connection with our chemotaxonomic studies of Malaysian species of the red algal genus Laurencia, the chemical composition of Laurencia pannosa Zanardini was examined. Two halogenated sesquiterpenoids, named pannosanol (1) and pannosane (2), have been isolated along with a halogenated C15-acetogenin, (3Z)-chlorofucin (3). The structures of these compounds were determined from their spectroscopic data (IR, 1H NMR, 13C NMR, 2D NMR, and MS). Pannosanol and pannosane are novel halometabolites with an unusual rearranged chamigrane framework. Antibacterial activities of these metabolites against marine bacteria are also described.
  19. Subramaniam G, Hiraku O, Hayashi M, Koyano T, Komiyama K, Kam TS
    J Nat Prod, 2008 Jan;71(1):53-7.
    PMID: 18078327
    Ten new indole alkaloids of the aspidofractinine type, in addition to several recently reported indole alkaloids and 20 other known alkaloids, were obtained from the leaf and stem-bark extract of the Malayan Kopsia singapurensis, viz., kopsimalines A-E (1-5), kopsinicine (6), kopsofinone (7), and kopsiloscines H-J (8-10). The structures of these alkaloids were determined using NMR and MS analysis. Kopsimalines A (1), B (2), C (3), D (4), and E (5) and kopsiloscine J (10) were found to reverse multidrug-resistance in vincristine-resistant KB cells, with 1 showing the highest potency.
  20. Subramaniam G, Hiraku O, Hayashi M, Koyano T, Komiyama K, Kam TS
    J Nat Prod, 2007 Nov;70(11):1783-9.
    PMID: 17939738
    Eleven new indole alkaloids, in addition to the previously reported rhazinal (1), and 14 other known alkaloids, were obtained from the Malayan Kopsia singapurensis, viz., kopsiloscines A-F (2-7), 16-epikopsinine (8), kopsilongine- N-oxide (9), 16-epiakuammiline (10), aspidophylline A (11), and vincophylline (12). The structures of these alkaloids were determined using NMR and MS analyses. Rhazinal (1), rhazinilam (17), and rhazinicine (18) showed appreciable cytotoxicity toward drug-sensitive as well as vincristine-resistant KB cells, while kopsiloscines A (2), B (3), and D (5) and aspidophylline A (11) were found to reverse drug-resistance in drug-resistant KB cells.
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