Displaying publications 1 - 20 of 81 in total

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  1. Tang SY, Tan CH, Sim KS, Yong KT, Lim KH, Low YY, et al.
    Phytochemistry, 2023 Apr;208:113587.
    PMID: 36646163 DOI: 10.1016/j.phytochem.2023.113587
    Eight undescribed iboga alkaloids, polyneurines A-H, were isolated from the bark of Tabernaemontana polyneura. The structures of these alkaloids were established by interpretation of the MS and NMR data, while the configurations were determined using GIAO NMR calculations and DP4+ probability analysis, TDDFT-ECD method, or X-ray diffraction analysis. Polyneurine A possesses a γ-lactone unit embedded within the iboga skeleton, while polyneurines D and E incorporate a formylmethyl moiety at C-3 of the iboga skeleton. Biosynthetic pathways towards the formation of polyneurines A, C, D, and E were proposed.
    Matched MeSH terms: Indole Alkaloids/chemistry
  2. Nugroho AE, Zhang W, Hirasawa Y, Tang Y, Wong CP, Kaneda T, et al.
    J Nat Prod, 2018 11 26;81(11):2600-2604.
    PMID: 30362746 DOI: 10.1021/acs.jnatprod.8b00749
    Three new bisindole alkaloids, bisleuconothines B-D (1-3), were isolated from the bark of Leuconotis griffithii. Their structures were elucidated by 1D and 2D NMR spectroscopy and DFT calculations. Bisleuconothine B (1) is the first monoterpene indole alkaloid dimer featuring bridges between both C-16-C-10' and C-2-O-C-9'. All compounds were deemed noncytotoxic (IC50 > 10 μM) when tested against A549 human lung adenocarcinoma cells.
    Matched MeSH terms: Indole Alkaloids/isolation & purification*; Indole Alkaloids/chemistry
  3. Kam TS, Choo YM
    Alkaloids Chem Biol, 2006;63:181-337.
    PMID: 17133716
    Matched MeSH terms: Indole Alkaloids/chemical synthesis; Indole Alkaloids/classification; Indole Alkaloids/chemistry*
  4. Kalshetti MG, Argade NP
    Alkaloids Chem Biol, 2020;83:187-223.
    PMID: 32098650 DOI: 10.1016/bs.alkal.2019.12.001
    The tryptamine-derived polycyclic bridged bioactive indole alkaloids subincanadines A-G were isolated in 2002 by Ohsaki and coworkers from the bark of the Brazilian medicinal plant Aspidosperma subincanum. Kobayashi proposed that subincanadines D-F could be biosynthetically resulting from stemmadenine via two different pathways and, furthermore, that the subincanadines A-C could be biogenetically resulting from subincanadines D and E. Kam and coworkers, in their focused efforts, isolated five indole alkaloids from Malaysian Kopsia arborea species, namely valparicine, apparicine, arboridinine, arborisidine, and arbornamine in combination with subincanadine E. On the basis of structural features, it has been proposed and proved in some examples that subincanadine E is a biogenetic precursor of these five different bioactive indole alkaloids bearing complex structural architectures. All important information on isolation, characterization, bioactivity, probable biogenetic pathways, and more specifically racemic and enantioselective total synthesis of subincanadine alkaloids and their biogenetic congeners are summarized in the present chapter. Special importance is given to the total synthesis and the synthetic strategies intended therein, comprising a set of main reactions.
    Matched MeSH terms: Indole Alkaloids/isolation & purification; Indole Alkaloids/metabolism; Indole Alkaloids/chemistry*
  5. Zhong X, Li Y, Zhang J, Han FS
    Org. Lett., 2015 Feb 6;17(3):720-3.
    PMID: 25602274 DOI: 10.1021/ol503734x
    The synthesis of a pentacyclic indole compound corresponding to the core structure of the misassigned indole alkaloid, tronoharine (1), is presented. The key reactions were a formal [3 + 3] cycloaddition of an indol-2-yl carbinol with an azadiene for the construction of the 6/5/6/6 tetracyclic system containing an all-carbon quaternary center and an intramolecular substitution reaction of an amine and a triflate for the creation of the bridged azepine ring. In addition, some other interesting transformations discovered during the synthetic studies are also discussed.
    Matched MeSH terms: Indole Alkaloids/chemical synthesis*; Indole Alkaloids/chemistry*
  6. Low YY, Gan CY, Kam TS
    J Nat Prod, 2014 Jun 27;77(6):1532-5.
    PMID: 24832351 DOI: 10.1021/np500289t
    Racemic andransinine (1), an indole alkaloid derivative obtained during isolation of alkaloids from Alstonia angustiloba and Kopsia pauciflora, was found to undergo spontaneous resolution when crystallized in EtOAc, forming racemic conglomerates (an equimolar mechanical mixture of enantiomerically pure individual crystals). X-ray analyses of the enantiomers (obtained from crystals from EtOAc solution and from chiral-phase HPLC) provided the absolute configuration of each enantiomer as (15R,16S,21R)-(+)-andransinine (1a or I+) and (15S,16R,21S)-(-)-andransinine (1b or I-).
    Matched MeSH terms: Indole Alkaloids/isolation & purification*; Indole Alkaloids/chemistry
  7. Nge CE, Gan CY, Low YY, Thomas NF, Kam TS
    Org. Lett., 2013 Sep 20;15(18):4774-7.
    PMID: 23991636 DOI: 10.1021/ol4021404
    Two new indole alkaloids, voatinggine (1) and tabertinggine (2), which are characterized by previously unencountered natural product skeletons, were isolated from a Malayan Tabernaemontana species. The structures and absolute configuration of these alkaloids were determined using NMR and MS analysis, and X-ray diffraction analysis. A possible biogenetic pathway to these novel alkaloids from an iboga precursor, and via a common cleavamine-type intermediate, is presented.
    Matched MeSH terms: Indole Alkaloids/chemical synthesis*; Indole Alkaloids/chemistry
  8. Lim SH, Low YY, Tan SJ, Lim KH, Thomas NF, Kam TS
    J Nat Prod, 2012 May 25;75(5):942-50.
    PMID: 22559995 DOI: 10.1021/np300120p
    Three new bisindole alkaloids of the macroline-macroline type, perhentidines A-C (1-3), were isolated from the stem-bark extract of Alstonia macrophylla and Alstonia angustifolia. The structures of these alkaloids were established on the basis of NMR and MS analyses. The absolute configurations of perhentinine (4) and macralstonine (5) were established by X-ray diffraction analyses, which facilitated assignment of the configuration at C-20 in the regioisomeric bisindole alkaloids perhentidines A-C (1-3). A potentially useful method for the determination of the configuration at C-20 based on comparison of the NMR chemical shifts of the bisindoles and their acetate derivatives, in these and related bisindoles with similar constitution and branching of the monomeric units, is also presented.
    Matched MeSH terms: Indole Alkaloids/isolation & purification*; Indole Alkaloids/chemistry*
  9. Lim SH, Tan SJ, Low YY, Kam TS
    J Nat Prod, 2011 Dec 27;74(12):2556-62.
    PMID: 22148233 DOI: 10.1021/np200730j
    Four new linearly fused bisindole alkaloids, lumutinines A-D (1-4), were isolated from the stem-bark extract of Alstonia macrophylla. Lumutinines A (1) and B (2) represent the first examples of linear, ring A/F-fused macroline-macroline-type bisindoles, while lumutinines C (3) and D (4) were constituted from the union of macroline and sarpagine moieties. A reinvestigation of the stereochemical assignment of alstoumerine (8) by NMR and X-ray diffraction analyses indicated that the configuration at C-16 and C-19 required revision.
    Matched MeSH terms: Indole Alkaloids/isolation & purification*; Indole Alkaloids/chemistry
  10. 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/isolation & purification*; Indole Alkaloids/chemistry
  11. Tan YS, Ng MP, Tan CH, Tang WK, Sim KS, Yong KT, et al.
    J Nat Prod, 2024 Feb 23;87(2):286-296.
    PMID: 38284153 DOI: 10.1021/acs.jnatprod.3c00960
    Nine new alkaloids, eugeniinalines A-H (1-8) and (+)-eburnamenine N-oxide (9), comprising one quinoline, six indole, and two isogranatanine alkaloids, were isolated from the stem-bark extract of the Malayan Leuconotis eugeniifolia. The structures and absolute configurations of these alkaloids were established based on the analysis of the spectroscopic data, GIAO NMR calculations, DP4+ probability analysis, TDDFT-ECD method, and X-ray diffraction analysis. Eugeniinaline A (1) represents a new pentacyclic quinoline alkaloid with a 6/6/5/6/7 ring system. Eugeniinaline G (7) and its seco-derivative, eugeniinaline H (8), were the first isogranatanine alkaloids isolated as natural products. The known alkaloids leucolusine (10) and melokhanine A (11) were found to be the same compound, based on comparison of the spectroscopic data of both compounds, with the absolute configuration of (7R, 20R, 21S). Eugeniinalines A and G (1 and 7) showed cytotoxic activity against the HT-29 cancer cell line with IC50 values of 7.1 and 7.2 μM, respectively.
    Matched MeSH terms: Indole Alkaloids/pharmacology; Indole Alkaloids/chemistry
  12. Tan SJ, Lim KH, Subramaniam G, Kam TS
    Phytochemistry, 2013 Jan;85:194-202.
    PMID: 22995929 DOI: 10.1016/j.phytochem.2012.08.016
    Nine bisindole alkaloids, comprising four belonging to the macroline-sarpagine group, and five belonging to the macroline-pleiocarpamine group, were isolated from the stem-bark extracts of Alstonia angustifolia (Apocynacea). Their structures were established using NMR and MS analyses.
    Matched MeSH terms: Indole Alkaloids/chemistry*
  13. Low YY, Hong FJ, Lim KH, Thomas NF, Kam TS
    J Nat Prod, 2014 Feb 28;77(2):327-38.
    PMID: 24428198 DOI: 10.1021/np400922x
    Several transformations of the seco Aspidosperma alkaloid leuconolam were carried out. The based-induced reaction resulted in cyclization to yield two epimers, the major product corresponding to the optical antipode of a (+)-meloscine derivative. The structures and relative configuration of the products were confirmed by X-ray diffraction analysis. Reaction of leuconolam and epi-leuconolam with various acids, molecular bromine, and hydrogen gave results that indicated that the structure of the alkaloid, previously assigned as epi-leuconolam, was incorrect. This was confirmed by an X-ray diffraction analysis, which revealed that epi-leuconolam is in fact 6,7-dehydroleuconoxine. Short partial syntheses of the diazaspiro indole alkaloid leuconoxine and the new leuconoxine-type alkaloids leuconodines A and F were carried out.
    Matched MeSH terms: Indole Alkaloids/chemical synthesis; Indole Alkaloids/metabolism; Indole Alkaloids/chemistry*
  14. Muktar MR, Osman N, Awang K, Hazni H, Qureshi AK, Hadi AH, et al.
    Molecules, 2011 Dec 28;17(1):267-74.
    PMID: 22205092 DOI: 10.3390/molecules17010267
    A new indole alkaloid; neonaucline (1), along with six known compounds-Cadamine (2), naucledine (3), harmane, benzamide, cinnamide and blumenol A-were isolated from the leaves of Ochreinauclea maingayii (Rubiaceae). In addition to that of compound 1, (13)C-NMR data of cadamine (2) and naucledine (3) were also reported. Structural elucidations of these alkaloids were performed using spectroscopic methods especially 1D- and 2D-NMR, IR, UV and LCMS-IT-TOF. The excellent vasorelaxant activity on isolated rat aorta was observed for the alkaloids 1-3 after injection of each sample at 1 × 10(-5) M.
    Matched MeSH terms: Indole Alkaloids/isolation & purification; Indole Alkaloids/pharmacology; Indole Alkaloids/chemistry*
  15. 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/isolation & purification*; Indole Alkaloids/pharmacology; Indole Alkaloids/chemistry
  16. 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/isolation & purification; Indole Alkaloids/pharmacology; Indole Alkaloids/chemistry*
  17. 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/isolation & purification*; Indole Alkaloids/pharmacology*; Indole Alkaloids/chemistry
  18. Sim DS, Teoh WY, Sim KS, Lim SH, Thomas NF, Low YY, et al.
    J Nat Prod, 2016 Apr 22;79(4):1048-55.
    PMID: 26918761 DOI: 10.1021/acs.jnatprod.5b01117
    Six new bisindole alkaloids of the iboga-vobasine type, vobatensines A-F (1-6), in addition to four known bisindoles (8-11), were isolated from a stem bark extract of a Malayan Tabernaemontana corymbosa. The structures of these alkaloids were determined based on analysis of the spectroscopic data and in the case of vobatensines A (1), B (2), and 16'-decarbomethoxyvoacamine (8) also confirmed by partial syntheses. Nine of these alkaloids (1-5, 8-11) showed pronounced in vitro growth inhibitory activity against human KB, PC-3, LNCaP, HCT 116, HT-29, MCF7, MDA-MB-231, and A549 cancer cells.
    Matched MeSH terms: Indole Alkaloids
  19. 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/isolation & purification*; Indole Alkaloids/pharmacology; Indole Alkaloids/chemistry
  20. Qureshi AK, Mukhtar MR, Hirasawa Y, Hosoya T, Nugroho AE, Morita H, et al.
    Chem Pharm Bull (Tokyo), 2011;59(2):291-3.
    PMID: 21297315
    Two new indole alkaloids, neolamarckines A and B (1, 2) were isolated from the leaves of Neolamarckia cadamba (Rubiaceae). Structural elucidation of 1 and 2 was performed by combination of 2D-NMR and circular dichroism (CD) spectra, and chemical correlations. Neolamarckine A (1) showed inhibition of inducible nitric oxide synthase (iNOS) dose dependently.
    Matched MeSH terms: Indole Alkaloids/isolation & purification*; Indole Alkaloids/pharmacology; Indole Alkaloids/chemistry
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