12 research outputs found
School students’ views about Physics: A cross-national study involving England, Hong Kong and Singapore
Selected papers from First International Symposium on Advanced Networks and Telecommunication Systems (ANTS 2007)
10.1016/j.osn.2008.08.001Optical Switching and Networking611-
Conolodinines A–D, Aspidosperma–Aspidosperma Bisindole Alkaloids with Antiproliferative Activity from Tabernaemontana corymbosa
Examination of the EtOH extract of the leaves of the Malayan Tabernaemontana corymbosa resulted in the isolation of four new (1-4) and two known bisindole alkaloids (5, 6) of the Aspidosperma-Aspidosperma type. The structures of these alkaloids were determined based on analysis of the spectroscopic data (NMR and HRESIMS). X-ray diffraction analyses of the related bisindole alkaloids conophylline (5) and conophyllinine (6) established the absolute configurations. Treatment of the bisindole alkaloid conophylline (5) with benzeneselenic anhydride gave, in addition to the known bisindole polyervinine (7) previously isolated from another Malayan Tabernaemontana, another bisindole product, 8, an isolable tautomer of 7. X-ray diffraction analyses yielded the absolute configurations of both bisindoles and in addition showed that polyervinine (7) exists primarily as the neutral dione structure. The bisindoles (1-8) and the related conophylline-type bisindoles (9-13) showed pronounced in vitro growth inhibitory activity against an array of human cancer cell lines, including KB, vincristine-resistant KB, PC-3, LNCaP, MCF7, MDA-MB-231, A549, HT-29, and HCT 116 cells, with IC50 values for the active compounds in the 0.01-5 μM range. © 2019 American Chemical Society and American Society of Pharmacognosy
Ajmaline, Oxindole, and Cytotoxic Macroline–Akuammiline Bisindole Alkaloids from Alstonia penangiana
Examination of the EtOH extract of the Malayan Alstonia penangiana resulted in the isolation of 10 new alkaloids, comprising two ajmaline (1, 2), four macroline oxindole (3-6), and four macroline-akuammiline bisindole alkaloids (7-10). The structures of these alkaloids were determined based on analysis of the spectroscopic data and, in the case of the oxindole 6 and the bisindole alkaloid 7, also confirmed by X-ray diffraction analysis. The bisindole alkaloids 7 and 8 showed pronounced in vitro growth inhibitory activity against an array of human cancer cell lines, including KB, vincristine-resistant KB, PC-3, LNCaP, MCF7, MDA-MB-231, HT-29, HCT 116, and A549 cells with IC50 values in the 0.3-8.3 μM range
Gargantulide A, a complex 52-membered macrolactone showing antibacterial activity from streptomyces sp.
Gargantulide A (1), an extremely complex 52-membered macrolactone, was isolated from Streptomyces sp. A42983 and displayed moderate activity against MRSA. The planar structure of 1 was determined using 2D NMR, and its stereochemistry was partially established on the basis of NOESY correlations, J-based configuration analysis, and Kishi's universal NMR database
Ajmaline, Oxindole, and Cytotoxic Macroline–Akuammiline Bisindole Alkaloids from <i>Alstonia penangiana</i>
Examination of the EtOH extract of
the Malayan <i>Alstonia
penangiana</i> resulted in the isolation of 10 new alkaloids,
comprising two ajmaline (<b>1</b>, <b>2</b>), four macroline
oxindole (<b>3</b>–<b>6</b>), and four macroline–akuammiline
bisindole alkaloids (<b>7</b>–<b>10</b>). The structures
of these alkaloids were determined based on analysis of the spectroscopic
data and, in the case of the oxindole <b>6</b> and the bisindole
alkaloid <b>7</b>, also confirmed by X-ray diffraction analysis.
The bisindole alkaloids <b>7</b> and <b>8</b> showed pronounced
in vitro growth inhibitory activity against an array of human cancer
cell lines, including KB, vincristine-resistant KB, PC-3, LNCaP, MCF7,
MDA-MB-231, HT-29, HCT 116, and A549 cells with IC<sub>50</sub> values
in the 0.3–8.3 μM range
Ajmaline, Oxindole, and Cytotoxic Macroline–Akuammiline Bisindole Alkaloids from <i>Alstonia penangiana</i>
Examination of the EtOH extract of
the Malayan <i>Alstonia
penangiana</i> resulted in the isolation of 10 new alkaloids,
comprising two ajmaline (<b>1</b>, <b>2</b>), four macroline
oxindole (<b>3</b>–<b>6</b>), and four macroline–akuammiline
bisindole alkaloids (<b>7</b>–<b>10</b>). The structures
of these alkaloids were determined based on analysis of the spectroscopic
data and, in the case of the oxindole <b>6</b> and the bisindole
alkaloid <b>7</b>, also confirmed by X-ray diffraction analysis.
The bisindole alkaloids <b>7</b> and <b>8</b> showed pronounced
in vitro growth inhibitory activity against an array of human cancer
cell lines, including KB, vincristine-resistant KB, PC-3, LNCaP, MCF7,
MDA-MB-231, HT-29, HCT 116, and A549 cells with IC<sub>50</sub> values
in the 0.3–8.3 μM range