Displaying publications 1 - 20 of 62 in total

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  1. Kam TS, Sim KM
    J Nat Prod, 2002 May;65(5):669-72.
    PMID: 12027738
    Five new indole alkaloids of the ibogan type (1-5), in addition to 12 other known iboga alkaloids, were obtained from the leaf and stem-bark extract of the Malayan species Tabernaemontana corymbosa, viz., 19(S)-hydroxyibogamine (1), 19-epi-isovoacristine (2), isovoacryptine (3), 3R/S-ethoxyheyneanine (4), and 3R/S-ethoxy-19-epi-heyneanine (5). The structures were determined using NMR and MS analysis and comparison with known related compounds.
    Matched MeSH terms: Indole Alkaloids/chemistry
  2. Kam TS, Sim KM, Pang HS
    J Nat Prod, 2003 Jan;66(1):11-6.
    PMID: 12542336
    Ten new bisindole alkaloids of the vobasinyl-ibogan type, viz., conodiparines A-F (1-6), conodutarines A and B (7, 8), and cononitarines A and B (9, 10), were obtained from the leaf extract of the Malayan species Tabernaemontana corymbosa. The structures were determined using NMR and MS analysis.
    Matched MeSH terms: Indole Alkaloids/chemistry
  3. Kam TS, Pang HS, Lim TM
    Org Biomol Chem, 2003 Apr 21;1(8):1292-7.
    PMID: 12929658
    The ethanol extract of the leaves of Tabernaemontana divaricata (double flower variety) provided a total of 23 alkaloids, including the new aspidosperma alkaloids, taberhanine, voafinine, N-methylvoafinine, voafinidine, voalenine and the new bisindole alkaloid, conophyllinine in addition to the previously known, biologically active bisindole, conophylline and its congener, conofoline. The structures of the new alkaloids were established by spectroscopic methods. The preparation and characterization of the corresponding quinones of the biologically active bisindoles are also described in relation to a structure-activity study of these compounds with respect to their action in stimulating insulin expression.
    Matched MeSH terms: Indole Alkaloids/chemistry*
  4. Kam TS, Sim KM
    Phytochemistry, 2003 Jul;63(5):625-9.
    PMID: 12809725
    Four bisindole alkaloids, viz., 19'(S)-hydroxyconodurine, conodurinine, 19'(S)-hydroxyconoduramine, and 19'(S)-hydroxyervahanine A, in addition to conodurine and ervahanine A, were obtained from the leaf and stem-bark extracts of Tabernaemontana corymbosa. The structures of the new alkaloids were determined using NMR and MS analysis.
    Matched MeSH terms: Indole Alkaloids/chemistry
  5. Kam TS, Choo YM
    J Nat Prod, 2004 Apr;67(4):547-52.
    PMID: 15104482
    Ten new indole alkaloids, alstomaline (1), 10,11-dimethoxynareline (2), alstohentine (3), alstomicine (4), 16-hydroxyalstonisine (5), 16-hydroxyalstonal (6), 16-hydroxy-N(4)-demethylalstophyllal oxindole (7), alstophyllal (8), 6-oxoalstophylline (9), and 6-oxoalstophyllal (10), in addition to 21 other known ones, were obtained from the leaf extract of the Malayan Alstonia macrophylla. The structures were determined using NMR and MS analysis.
    Matched MeSH terms: Indole Alkaloids/chemistry
  6. Kam TS, Pang HS, Choo YM, Komiyama K
    Chem Biodivers, 2004 Apr;1(4):646-56.
    PMID: 17191876
    Six new indole alkaloids, viz., (3S)-3-cyanocoronaridine (2), (3S)-3-cyanoisovoacangine (3), conolobine A (5), conolobine B (6), conolidine (7), and (3R/3S)-3-ethoxyvoacangine (8), in addition to 36 known ones, were obtained from the stem-bark extract of the Malayan Tabernaemontana divaricata. The structures were determined by NMR and MS analysis. The CN-substituted alkaloids showed appreciable cytotoxicity towards the KB human oral epidermoid carcinoma cell-line.
    Matched MeSH terms: Indole Alkaloids/chemistry
  7. Takayama H
    Chem Pharm Bull (Tokyo), 2004 Aug;52(8):916-28.
    PMID: 15304982
    The leaves of a tropical plant, Mitragyna speciosa KORTH (Rubiaceae), have been traditionally used as a substitute for opium. Phytochemical studies of the constituents of the plant growing in Thailand and Malaysia have led to the isolation of several 9-methoxy-Corynanthe-type monoterpenoid indole alkaloids, including new natural products. The structures of the new compounds were elucidated by spectroscopic and/or synthetic methods. The potent opioid agonistic activities of mitragynine, the major constituent of this plant, and its analogues were found in in vitro and in vivo experiments and the mechanisms underlying the analgesic activity were clarified. The essential structural features of mitragynines, which differ from those of morphine and are responsible for the analgesic activity, were elucidated by pharmacological evaluation of the natural and synthetic derivatives. Among the mitragynine derivatives, 7-hydroxymitragynine, a minor constituent of M. speciosa, was found to exhibit potent antinociceptive activity in mice.
    Matched MeSH terms: Indole Alkaloids/chemistry*
  8. Kam TS, Choo YM
    Alkaloids Chem Biol, 2006;63:181-337.
    PMID: 17133716
    Matched MeSH terms: Indole Alkaloids/chemistry*
  9. Lim SH, Sim KM, Abdullah Z, Hiraku O, Hayashi M, Komiyama K, et al.
    J Nat Prod, 2007 Aug;70(8):1380-3.
    PMID: 17608533
    Four new indole alkaloids were obtained from two Kopsia species, 6-oxoleuconoxine (1) from the leaf extract of K. griffithii and kopsinitarine E (2), kopsijasminine (3), and kopsonoline (4) from the stem-bark extract of K. teoi. The structures of these alkaloids were determined using NMR and MS analysis. Kopsijasminine (3) showed moderate activity in reversing multidrug resistance in vincristine-resistant KB cells.
    Matched MeSH terms: Indole Alkaloids/chemistry
  10. Lim KH, Hiraku O, Komiyama K, Koyano T, Hayashi M, Kam TS
    J Nat Prod, 2007 Aug;70(8):1302-7.
    PMID: 17665953
    Nine new indole alkaloids, rhazinoline (1), 19(S)-methoxytubotaiwine (2), 19(R)-methoxytubotaiwine (3), kopsamidine A (4), kopsamidine B (5), kopsinidine A (6), kopsinidine B (7), paucidactine C (8), and pericine N-oxide (9), in addition to several recently reported novel indoles and 34 other known ones, were obtained from the stem-bark extract of the Malayan Kopsia arborea. The structures were determined using NMR and MS analysis. Valparicine (12) showed pronounced cytotoxic effects against KB and Jurkat cells (IC(50) 13.0 and 0.91 microM, respectively).
    Matched MeSH terms: Indole Alkaloids/chemistry
  11. 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.
    Matched MeSH terms: Indole Alkaloids/chemistry
  12. Lim KH, Hiraku O, Komiyama K, Kam TS
    J Nat Prod, 2008 Sep;71(9):1591-4.
    PMID: 18778099 DOI: 10.1021/np800435c
    Seven new indole alkaloids of the Aspidosperma type, jerantinines A-G (1-7), were isolated from a leaf extract of the Malayan Tabernaemontana corymbosa. The structures were established using NMR and MS analysis. Five of the alkaloids isolated and two derivatives (1-5, 8, 9) displayed pronounced in vitro cytotoxicity against human KB cells (IC50 < 1 microg/mL).
    Matched MeSH terms: Indole Alkaloids/chemistry
  13. Kam TS, Tan SJ, Ng SW, Komiyama K
    Org. Lett., 2008 Sep 4;10(17):3749-52.
    PMID: 18683934 DOI: 10.1021/ol801354s
    A cytotoxic bisindole alkaloid possessing an unprecedented structure in which two indole moieties are bridged by an aromatic spacer unit has been isolated from Alstonia angustifolia. The structure was established by analysis of the spectroscopic data and confirmed by X-ray diffraction analysis. A possible biogenetic pathway from pyrocatechuic acid and pleiocarpamine is presented.
    Matched MeSH terms: Indole Alkaloids/chemistry*
  14. Lim KH, Thomas NF, Abdullah Z, Kam TS
    Phytochemistry, 2009 Feb;70(3):424-9.
    PMID: 19217125 DOI: 10.1016/j.phytochem.2009.01.001
    Two seco-tabersonine alkaloids, jerantiphyllines A and B, in addition to a tabersonine hydroxyindolenine, jerantinine H, and a recently reported vincamine alkaloid 7, were isolated from the leaf extract of the Malayan Tabernaemontana corymbosa and the structures were established using NMR and MS analysis. Biomimetic conversion of jerantinines A and E to their respective vincamine and 16-epivincamine derivatives were also carried out.
    Matched MeSH terms: Indole Alkaloids/chemistry*
  15. Lim KH, Sim KM, Tan GH, Kam TS
    Phytochemistry, 2009 Jun;70(9):1182-1186.
    PMID: 19643450 DOI: 10.1016/j.phytochem.2009.06.010
    Four tetracyclic oxindole alkaloids, 7(R)- and 7(S)-geissoschizol oxindole (1 and 2), 7(R),16(R)- and 7(S),16(R)-19(E)-isositsirikine oxindole (3 and 4), in addition to a taberpsychine derivative, N(4)-demethyltaberpsychine (5), were isolated from the Malayan Tabernaemontana corymbosa and the structures were established using NMR and MS analysis.
    Matched MeSH terms: Indole Alkaloids/chemistry
  16. Nugroho AE, Hirasawa Y, Kawahara N, Goda Y, Awang K, Hadi AH, et al.
    J Nat Prod, 2009 Aug;72(8):1502-6.
    PMID: 19388660 DOI: 10.1021/np900115q
    A new bisindole alkaloid, bisnicalaterine A (1), consisting of two vobasine-type skeletons, and 3-epivobasinol (2) and 3-O-methylepivobasinol (3), with vobasine-type skeletons, were isolated from the leaves of Hunteria zeylanica, and their structures were elucidated on the basis of spectroscopic data and chemical correlation. Bisnicalaterine A showed moderate cytotoxicity against various human cancer cell lines.
    Matched MeSH terms: Indole Alkaloids/chemistry
  17. Gan CY, Robinson WT, Etoh T, Hayashi M, Komiyama K, Kam TS
    Org. Lett., 2009 Sep 3;11(17):3962-5.
    PMID: 19708704 DOI: 10.1021/ol9016172
    A cytotoxic bisindole alkaloid possessing an unprecedented structure constituted from the union of an eburnan half and a novel vinylquinoline alkaloid has been isolated from Leuconotis griffithii. The structure was established by analysis of the spectroscopic data and confirmed by X-ray diffraction analysis. A possible biogenetic pathway to the novel quinolinic coupling partner is presented from an Aspidosperma precursor.
    Matched MeSH terms: Indole Alkaloids/chemistry
  18. Gan CY, Low YY, Etoh T, Hayashi M, Komiyama K, Kam TS
    J Nat Prod, 2009 Dec;72(12):2098-103.
    PMID: 20035556 DOI: 10.1021/np900576b
    Seven new indole alkaloids of the Strychnos type, leuconicines A-G (1-7), and a new eburnan alkaloid, (-)-eburnamaline (8), were isolated from the stem-bark extract of two Malayan Leuconotis species. The structures of these alkaloids were established using NMR and MS analysis and in the case of 8 also by partial synthesis. Alkaloids 1-5 reversed multidrug resistance in vincristine-resistant KB cells.
    Matched MeSH terms: Indole Alkaloids/chemistry
  19. Hirasawa Y, Hara M, Nugroho AE, Sugai M, Zaima K, Kawahara N, et al.
    J Org Chem, 2010 Jun 18;75(12):4218-23.
    PMID: 20469917 DOI: 10.1021/jo1006762
    Two new bisindole alkaloids, bisnicalaterines B and C (1 and 2) consisting of an eburnane and a corynanthe type of skeletons, were isolated from the bark of Hunteria zeylanica. Their absolute structures were determined by combination of NMR, CD, and computational methods, and each of them was shown to be in an atropisomeric relationship. Bisnicalaterines B and C (1 and 2) showed potent vasorelaxant activity on isolated rat aorta.
    Matched MeSH terms: Indole Alkaloids/chemistry*
  20. Gan CY, Etoh T, Hayashi M, Komiyama K, Kam TS
    J Nat Prod, 2010 Jun 25;73(6):1107-11.
    PMID: 20515042 DOI: 10.1021/np1001187
    Four new bisindole alkaloids of the Strychnos-Strychnos type, leucoridines A-D (1-4), were isolated from the stem-bark extract of Leuconotis griffithii. Alkaloids 1-4 showed moderate cytotoxicity against drug-sensitive and vincristine-resistant human KB cells.
    Matched MeSH terms: Indole Alkaloids/chemistry
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