Ibogan, Tacaman, and Cytotoxic Bisindole Alkaloids from <i>Tabernaemontana</i>. Cononusine, an Iboga Alkaloid with Unusual Incorporation of a Pyrrolidone Moiety Kuan-Hon Lim Vijay J. Raja Tracey D. Bradshaw Siew-Huah Lim Yun-Yee Low Toh-Seok Kam 10.1021/acs.jnatprod.5b00117.s002 https://acs.figshare.com/articles/dataset/Ibogan_Tacaman_and_Cytotoxic_Bisindole_Alkaloids_from_i_Tabernaemontana_i_Cononusine_an_Iboga_Alkaloid_with_Unusual_Incorporation_of_a_Pyrrolidone_Moiety/2164762 Six new indole alkaloids, viz., cononusine (<b>1</b>, a rare example of an iboga–pyrrolidone conjugate), ervaluteine (<b>2</b>), vincamajicine (<b>3</b>), tacamonidine (<b>4</b>), 6-oxoibogaine (<b>5</b>), and <i>N</i><sup>4</sup>-chloromethylnorfluorocurarine chloride (<b>6</b>), and two new vobasinyl-iboga bisindole alkaloids, ervatensines A (<b>7</b>) and B (<b>8</b>), in addition to other known alkaloids, were isolated from the stem-bark extract of the Malayan <i>Tabernaemontana corymbosa</i>. The structures of these alkaloids were established on the basis of NMR and MS analyses and, in one instance (<b>7</b>), confirmed by X-ray diffraction analysis. Vincamajicine (<b>3</b>) showed appreciable activity in reversing multidrug resistance in vincristine-resistant KB cells (IC<sub>50</sub> 2.62 μM), while ervatensines A (<b>7</b>) and B (<b>8</b>) and two other known bisindoles displayed pronounced in vitro growth inhibitory activity against human KB cells (IC<sub>50</sub> < 2 μM). Compounds <b>7</b> and <b>8</b> also showed good growth inhibitory activity against A549, MCF-7, MDA-468, HCT-116, and HT-29 cells (IC<sub>50</sub> 0.70–4.19 μM). Cell cycle and annexin V-FITC apoptosis assays indicated that compounds <b>7</b> and <b>8</b> inhibited proliferation of HCT-116 and MDA-468 cells, evoking apoptotic and necrotic cell death. 2015-05-22 00:00:00 Cell cycle MS analyses HT Compounds 7 ervatensine Unusual Incorporation HCT KB cells Iboga Alkaloid MDA compounds 7 Pyrrolidone MoietySix multidrug resistance NMR Cytotoxic Bisindole Alkaloids IC 50 bisindole indole alkaloids Malayan Tabernaemontana corymbosa 2 μ M cell death MCF